Philosophical transactions of the Royal Society of London

Natural History Museum Library

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PHILOSOPHICA L

TRANSACTIONS,

OF THE

ROYAL SOCIETY

O F

LONDON.

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V O L. LXVII. For the Year 1777.

P A R T I.

L O N D O N,

PRINTED BY W. .BOWYER AND J. NICHOLS ::

FOR LOCKYER DAVIS, PRINTER TO THE ROYAL SOCIETY, .

MDCCLXXVII. .

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iii

ADVERTISEMENT.

TH E Committee appointed by the Royal Society to dire& the pub-
lication of the Fhilofophical Tranfadions , take this opportunity to
acquaint the Public, that it fully appears, as well from the council-books
and journals of the Society, as from repeated declarations, which have
been made in feveral former Tranfadions , that the printing of them was
always, from time to time, the fingle aft of the refpeftive Secretaries, till
the Forty-feventh Volume : the Society, as a body, never intereffing them-
ielves any further in their publication, than by occafionally recommending
the revival of them to fome of their Secretaries, when, from the particular
circumltances of their affairs, the Tranfadions had happened for any
length of time to be intermitted. And this feems principally to have
been done with a view to fatisfy the Public, that their ufual meetings
were then continued for the improvement of knowledge, and benefit of
mankind, the great ends of their firff inftitution by the Royal Charters,,
and which they have ever fince fteadily purfued.

But the Society being of late years greatly inlarged,. and their com-
munications more numerous, it was thought advifeable, that a Committee
of their members fhouid be appointed to reconfider the papers read be-*
fore them, and feleft out of them fuch, as they Ihould judge moft pro-
per for publication in the future Tranfadions \ which was accordingly
done upon the 26th of March 1752. And the grounds of their choice
are, and will continue to be, the importance and fmgularity of the fub-
jefts, or the advantageous manner of treating them without pretending
to anfwer for the certainty of the faffs, or propriety of the reafonings,
contained in the feveral papers fo publifhed, which muff ftill reft on the
credit or judgment of their refpeftive authors..

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It is likewife neceffary on this occafion to remark, that it is an Sfta-
blifhed rule of the Society, to which they will always adhere, never to
give their opinion, as a body, upon any fubjeft, either of Nature or Art,
that comes before them. And therefore the thanks, which are fre-
quently propofed from the chair, to be given to the authors of fuch pa-
pers, as are read at their accuftomed meetings, or to the perfons through
whofe hands they receive them, are to be confidered in no other light
than as a matter of civility, in return for the refpeft fhewn to the Society
by thofe communications. The like alfo is to be faid with regard to
the feveral projects, inventions, and curiofities of various kinds, which
are often exhibited to the Society ; the authors whereof, or thofe who
exhibit them, frequently take the liberty to report, and even to certify
in the public news-papers, that they have met with the higheft applaufe
and approbation. And therefore it is hoped, that no regard will here-
after be paid to fuch reports, and public notices ; which in fome inftanccs
have been too lightly credited, to the dilhonour of the Society.

!’■

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I V ]

CONTENTS

T O

VOL. LXV1I. Part I.

»• AN Account of a Woman in the Shire o/Rofs living
zvithout Food or Drink. By Dr. Mackenzie, Phy-
Jician at New Tarbat. Communicated by the Right
Honourable James Stewart Mackenzie, Lord Privy Seal
of Scotland. page 1

II. On the Ufefulnefs of waflnng and rubbing the Stems of

Trees, to promote their Annual Increafe. In an Ex-
tract of a Letter from Mr. Marfham to the Lord Bi/hop
of Bath and Wells. p. i a

III. Difcoveries on the Sex of Bees, explaining the Manner

in which their Species is propagated', with an Account
of the Utility that may be derived from thofe Difcoveries
by the adlua'l Application of them to Practice. By Mr.
John Debra w, Apothecary to Addenbrook’s Hof pit al at
Cambridge, and Member of an Oeconomical Society in
the Principality 0/ Liege in Weftphalia. Communicated
by the Rev. Nevil Maflcelyne, B, D. F. R. S. and AJlro-
nomer Royal. p. 15

IV.

CONTENTS.

vi _

IV. An Account ' of a Portrait of Copernicus, prefented to
the Royal Society by Dr. Wolf of Dantzick: ex-
tracted from a Letter of his to Mr. Magellan, F. R. S.

P- 33

V. An Account of a Journey into Africa from the Cape

of Good-Hope, and a Defer ipt ion of a new Species of
Cuclcow. By Dr. Andreas Sparrman, of the Royal Aca-
demy of Stockholm, in a Letter to Dr. John Reinhold
Forfter, F. R. S. p. 38

VI. An Account of fome nezv EleSlrical Experiments. By

Mr. Tiberius Cavallo: communicated by Mr. Henley,
F. R. S. p. 48

VII. A Third EJfay on Sea-anemonies. By the Abbe

Dicquemare. p. 56

VIII. Experiments and Obfervations in Electricity. By

Mr. William Henly, F. R. S. p. 85

IX. Extract of a Letter from John Strange, Ef quire ,

His Majejlfs Refident at Venice, to Sir John Pringle,
Bart. P. R. S. : with a Letter to Mr. Strange from the
Abbe Jofeph Toaldo, Profejfor in the Univerfity of
Padua, &c. giving an Account of the Tides in the
Adriatic. p. 1 44

X. A Letter from Mr. Peter Wargentin, F. R. S. Secre-
tary to the Royal Academy of Sciences at Stockholm, to
the Rev. Nevil Mafkelyne, B. D. F. R. S. and AJlro-
nomer Royal ; concerning the Difference of Longitude of
the Royal Obfervatories at Paris and Greenwich, refult-
ing from the Eclipfes of Jupiter’s jirjl Satellite. , obferved
during the lajl Ten Tears: to which is added , a Compa-
rative

CONTENTS.

vn

native ’table of the correfponding Qbfervations of the
Firjl Satellite , made in the principal Obfervatories.

p. 162

XI. A Method of finding the Value of an infinite Series of

decreafing Quantities of a certain Form , when it con-
verges too Jlowly to be fummed in the common Way by
the mere Computation and Addition or Subtra&ion of
fome of its initial terms . By Francis Maferes, Ef quire ,
F. R. S. Curfitor Baron of the Exchequer. p. 1 87

XII. tranjlation of a Paffage in Ebn Younes; with fome

Remarks thereon : in a Letter from the Rev. George
Coftard, M. A. Vicar of Twickenham, to the Rev. Sa-
muel Horfley, LL.D. Sec. R. S. p. 2,31

XIII. Obfervations on the Annual Evaporation at Liver-

pool in Lancafhire ; and on Evaporation confidered as a
tefi of the Moifiure or Drynefs of the Atmofphere. By
Dr. Dobfon of Liverpool. Communicated by John
Fothergill, M. D. F. R. S. p. 244

XIV. An Account of Perfons who could not difiinguijh Co-

lours. By Mr. Jofeph Huddart, in a Letter to the Rev.
Jofeph Prieftley, LL.D. F. R. S. p. 260

XV. Anew theory of the Rotatory Motion of Bodies ajfeCled

by Forces difiurbing fuch Motion. By Mr. John Lan-
den, F. R. S. p. 266

XVI. Directions for making the befi. Compofition for the

Metals of reflecting telef copes ; together with a Defer ip-
tion of the Procefs for grinding, polifhing , and giving
the great Speculum the true parabolic Curve. By Mr.
John Mudge; communicated by Alexander Aubert,
Efq. F. R. S. p. 296

XVII. Ex-

vm

CONTENTS.

i

XVII. ExtraSl of a Regifter of the Barometer, Thermo-
meterand Rain, at Lyndon, in Rutland, 1776. By
Thomas Barker, Efquire. Communicated by Sir John
Pringle, Bart. P. R. S. p. 350

XVIII. ExtraSi of a Meteorologieal Journal for the Tear
1776, kept at Brifiol, by Samuel Farr, M. D. p. 353
XIX. Meteorological Journal kept at the Houfe of the Royal
Society, by Order of the Prejident and Council . p. 35 7

I

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PHILOSOPHICAL

TRANSACTIONS.

I. An Account of a Woman in the Shire of Rofs living
without Food or Drink. By Dr. Mackenzie, Phyfician
at NewTarbat. Communicated by the Right Honourable
James Stewart Mackenzie, Lord Privy Seal of Scotland.

TO SIR JOHN PRINGLE, BART. P. R. S.

o T t) Hill-Street,

^ 1 June 5, 1776.

ReadjNov. 7, T jjgRE inclofe the cafe of the fading
woman in Rofs-fhire, authenticated by
Mr. mac leod the fheriff, and feveral juftices of the peace
of that county ; that, in cafe you fhall think it vrorthy
to have a place in the Philofophical Tran factions, it may
be inferted therein. I am, with great regard, sir,
Your mod obedient humble fervant,

J. S. MACKENZIE.

B JANET

Vol. LXVII.

Dr. Mackenzie’s Account of

3

JANET MAG LEOD, unmarried, aged thirty-
three years and fome months, daughter of donald mac
leod, tenant in Croick, in the parifh of Kincardine, and
fhire of Rofs ; in the fifteenth year of her age had a
pretty fharp epileptic fit : fhe had till then been in perfect
health, and continued fo till about four years thereafter,
when fhe had a fecond fit, which lafted a whole day and
night ; and a few days afterwards, fhe was feized with a
fever of feveral weeks continuance, from which fhe had
a flow and very tedious recovery of feveral months.

During this period fhe loft the natural power of her
eye* lids, was under the neceffity of keeping them open
with the fingers of one hand, when fhe had any tiring
to do with the other, went out, or wanted to look about
her; in every other refpedl fire was in health and tolera-
ble fpirits, only here it may be fit to remark, that fire
never had the leaft appearance of the menfes , but peri-
odically fpit up blood in pretty large quantities, and at the
fame time it flowed from the nofe. This vicarious dif-
charge, according to her mother’s report, happened re-
gularly every month for feveral years.

About five years ago, a little before which time the-
abovementioned periodical difcharge had difappeared, fire
had a fhort third epileptic fit, which was immediately fuc-
5 ceedcd

a Woman living •without Food or Drink. 3
ceeded by a fever of about a week’s continuance, and of
which fhe recovered fo flowiy that fhe had not been out
of doors till fix weeks after the crifis ; when, without the
knowledge of her parents or any of the family (who
were all bulled in the harveft-fiekl) fire Hole out of the
houfe, and bound the corn of a ridge before they ob-
ferved her. On that fame evening fhe took to her bed,
complaining much of her heart and head ; and fince, file
lias never rifen out of it except when lifted, has feldom
fpoken a word, and has had fo little craving for food,
that at firft it was by downright compulfion her parents
could get her to take as much as would fupport a fuck-
ing infant : afterwards fhe gradually fell off from taking
even that fmall quantity ; infomuch that, at Whitfun-
tide 1763, flie totally refufed food and drink, and her jaw
became fo fall locked, that it was with the greateft diffi-
culty her father was able with a knife or other methods
to open her teeth fo as to admit a little thin gruel or whey,
and of which fo much generally run out at the corners
of her mouth, that they could not be fenfible that any
of it had been fwallowed.

Much about this time, that is, about four years ago,
they got a bottle of the water from a noted medicinal
fpring in Brea-mar, of which they endeavoured to get
her to fwallow a part, by pouring fome out of a fpoon

B 2 between

4 Dr. Mackenzie’s Account of

between her lips (her jaws all the while fall- locked) but
it all run out. With this, however, they rubbed her
throat and jaws, and continued the trial to make her
fwallow, rubbing her throat with the water that run out of
her mouth for three mornings together. On the third
morning during this operation, fhe cried, Give me more
water; when all that remained of the bottle was given
her, which fhe fwallowed with eafe. Thefewere the only
words fhe fpoke for almoft a year, and fire continued to
mutter fome more (which her parents underflood) for
twelve or fourteen days, after which fhe fpoke none, and
rejected, as formerly, all forts of nourifhment and drink,
till fome time in the month of July 1765, when a filler
of hers thought, by fome figns that fhe made, that fire
wanted her jaws opened; which her father, not without
violence, got done, by putting the handle of a horn-fpoon
between her teeth. She faid then intelligibly, Give me
a drink; and drank with eafe, and all at one draught,
about an Englifh pint of water. Her father then afked
her, Why fhe would not make fome figns, although fhe
could not fpeak, when fhe wanted a drink? She an-
fwered, why lhould fire when fhe had no defire. At
this period they kept the jaws afunder with a bit of wood,
imagining fhe got her fpeech by her jaws being opened,
and continued them thus wedged for about twenty days,

3 though

a Woman living without Food or Drink . 5

though in the firft four or five days fhe had wholly loft
the power of utterance. At laft they removed the wedge,
as it gave her uneafinefs, and made her lips fore. At
this time fhe was fenfible of every thing done or faid
about her; and when her eye-lids were opened for her,
fhe knew every body ; and when the neighbours in their
vifits would be bemoaning her condition, they could ob-
ferve a tear ftand.in her eye.

In fome of the attempts to open her jaws, two of the
under fore-teeth were forced out; of which opening
they often endeavoured to avail themfelves, by putting
fome thin nourifhing drink into her mouth ; but without
effect, for it always returned by the corners ; and, about a
twelvemonth ago, they thought of thrufting a little
dough of oatmeal through this gap of the teeth, which
fhe would retain a few feconds, and then return with
fornething like a {training to vomit, without one par-
ticle going down: nor has the family been fenfible,
though obferving, of any appearance like that of
fwallowing, for now four years, excepting the fmall
draught of Brea-mar water and the Englifh pint of com-
mon water; and for the laft three years fhe has not had
any evacuation by ftool or urine, except that, once or
twice a week, fhe has pafled a few drops of urine, as the
parents exprefs it, about as much as would wet the fur-

face

6 Dr. Mackenzie’s Account of

face of a half-penny ; and even fmall as this quantity is,
it gives her fome uneafmefs till fhe voids it : for they
know all her motions, and when they fee her thus un-
eafy, they carry her to the door of the houfe, where flic
makes thefe few drops. Nor have they, in all thefe
three years, ever difcovered the fmalleft wetting in her
bed; in proof of which, notwithftanding her being fo
long bed-ridden, there has never been the leall excoria-
tion, though lhe never attempts to turn herfelf,or makes
any motion with hand, head, or foot, but lies like a log
of wood. Her pulfe to-day, which with fome difficulty
I felt (her mother at this time having raifed her, and fup-
ported her in her bed) is cliftinft and regular, flow, and
to the extreme!! degree fmall. Her countenance is clear
and pretty frefh, her features not disfigured nor funk;
her fkin feels natural both as to touch and warmth ; and
to my aftonifhment, when I came to examine her body,
for I expecfied to feel a fkeleton, I found her breafts
round, and prominent, like thofe of a healthy young
woman; her legs, arms, and thighs, not at all ema-
ciated; the abdomen fomewhat tumid, and the mufcles
tenfe; her knees bent, and her ham-firings tight as a
bow-firing; her heels almoft clofe to the nates. When
they ftruggle with her, to put a little water within her
lips, they obferve fometimes a dewy foftnefs on her

fkin;

a Woman living without Food or Frink. 7
fkin; fhe deeps much, and very quiet; but when awake
keeps a condant whimpering like a new-born weakly
infant, and fometimes makes an effort to cough. At pre-
fent no degree of drength can force open her jaws. I
put the point of my little finger into the gap in her teeth,
and found the tongue, as far as I could reach, foft and
moifl ; as I did with my other fingers the mouth and
cheeks quite to the. back teeth. She never can remain
a moment, on. her back, but always falls to one fide or to
the other ; and when her mother fat behind her in the
bed, and fupported her while I was examining, her body,
her head hung down, with her chin clofe to her bread,
nor could I with any force move it backwards, the
anterior mufcles of the neck being rigid, like a perfon
in the emprojlhotonos , and in this pofture flie condantly
lies.

The above cafe was taken in writing this day, at the
difeafed woman’s bed-fide, from the mouths of her fa-
ther and mother, who are known to be people of great
veracity, and are under no temptation to deceive; for
they neither afk, expert, or get any thing : their daugh-
ter’s fituation is a, very great mortification to them, and
univerfally known and regretted by all their neigh-
bours. I had along with me, as interpreters .'<0, Mr. Henry
Robertfon, a very difcreet young gentleman,, elded fou

(a) The family fpoke only Erfe.

to

8 Dr. Mackenzie’s Account of

to the minifter of the parilh, and David Rofs, at the
Craig of Strath-Carron, their neighbour and one of the
elders of the parilh, who verified from his own know-
ledge all that is above related. The prefent fituation and
appearances of the patient were carefully examined this
aiftof Odober, 1767, by Dr. Alexander Mackenzie,
phyfician at New Tarbat; who likewife, in the month
of October, 1772, being informed that the patient was
recovering and ate and drank, vifited her, and found
her condition to be as follows : about a year preceding
this laft date, her parents one day returning from
their country labours (having left their daughter as
for fome years before fixed to her bed) were greatly
furprized to find her fitting on her hams, on the fide
of the houfe oppofite to her bed-place, fpinning
with her mother’s diftaff. I alked, whether (lie ever
ate or drank? whether fhe had any of the natural
evacuations? whether fhe ever fpoke or attempted to
fpeak? And was anfwered, that fhe fometimes crumbled a
bit of oat or barley cake in the palm of her hand, as if to
feed a chicken ; that fhe put little crumbs of this into the
gap of her teeth, rolled them about for fome time in
her mouth, and then fucked out of the palm of her hand
a little water, whey, or milk ; and this once or twice a
day, and even that by compulfion : that the ege/la were in

proportion

a Woman living without Food or Drink. 9

proportion to the ingejla ; that fhe. never attempted to
fpeak; that her jaws were Hill faft -locked, her ham-
ftrings tight as before, and her eyes lhut. On my open-
ing her eye-lids I found the eye-balls turned up under
the edge of the os front is, her countenance ghaftly, her
complexion pale, her fkin liar i veiled and dry, and her
whole perfon rather emaciated ; her pulfe with the ut-
moft difficulty to be felt. She feemed fenfible and
tractable in every thing, except in taking food ; for, at
my requeft, the went through her different exercifes,
fpinning on the diftaff, and crawling about on her hams,
by the wall of the houfe, with the help of her hands :
but when ffie was delired to eat, fhe fhewed the greateft
reluctance, and indeed cried before ffie yielded; and this
was no more than, as I have faid, to take a few crumbs as
to feed a bird, and to fuck half a fpoonful of milk from
the palm of her hand. On the whole, her exigence was
little lefs wonderful now than when I firft faw her, when
ffie had not fwallowed the fmalleft particle of food for
years together. I attributed her thinnefs and wan com-
plexion, that is the great change of her looks from what
I had firft feen when fixed to her bed, to her exhaufting
too much of the faliva by fpinning flax on the diftaff,
and therefore recommended her being totally confined
to fpinning wool: this ffie does with equal dexterity
Vol. LXVII. as

io Dr. Mackenzie’s Account of

as fhe did the flax. The above was her fituation in
October, 177a; and within thefe eight days I have been
told by a neighbour of her father’s, that fhe ftill con-
tinues in the fame way, without any addition to her fup-
port, and without any additional ailment.

New Tarbat,
April 1, 1275*

ALEX. MACKENZIE.

At Croick, the fifteenth Day of June, 1775.

T O authenticate the hiftory fet forth in the preceding
pages, donald mac leod, of Granics efq. fheriff depute
of Rofs-lhire, george munro efq. of Cuteain, simon
ross efq. of Gladfield, Captain george Sutherland of
Elphin, all juftices of the peace; Meflieurs william
smith preacher of the gofpel, john Barclay writer in
Tain, hugh ross ftudent of divinity, and Alexan-
der mac leod, did come to this place, accompanied by
the above Dr. Alexander Mackenzie phyfician at
New Tarbat, and after explaining the purport and mean-
ing of the above hiftory to donald mac leod father to
Janet mac leod above-mentioned, and to david ross
elder in the parilh of Kincardin, who lives in the clofe
neighbourhood of this place, and was one of the dodfor’S
original interpreters ; they, to our full fatisfadtion, after

a minute

a Woman Jiving without Food or Drink. n

a minute examination, authenticate all the fails let forth
in the above account : and, for our further fatisfadlion,
we had janet mac l-eod brought out before us to the
open air, when the doctor difcovered a very great im-
provement in her looks and health fince the period of
his having feen her laft, as now lire walked tolerably
upright, with a little hold by the wall. And notwith-
ftanding her age, which, upon inquiry, we found to be
exactly as fet forth in the above account, her counte-
nance and looks would have denoted her not to be above
twenty years of age at moll. At prefent, the quantity of
food fire ufes is not above what would be neceffary for
the fuftenance of an infant of two years of age. And we
do report, from our knowledge of the above men, and
the circumltances of the cafe, that full faith and credit
is to be given to every article of the above hiltory.

WILLIAM SMITH. DONd. Mc LEOD, SH. DEP.

JOHN BARCLAY, N. P. GEO. MUNRO, J. P.

HUGH ROSS. SIMON ROSS, J. P.

ALEXR. Mc LEOD. GEO. SUTHERLAND, J. P.

C a

la

Mr. mars ham on the Ufefulnefs of

II. On the Ufefulnefs of wafhtng and rubbing the Stems of
frees, to promote their Annual Increafe. In an Ex-
tract of a Letter from Mr. Marfham to the Lord Bi/hop
of Bath and Wells. r

Read Nov. 14, T H AD for feveral years intended to put in
■“* practice the celebrated Dr. hales advice
of wafhing, with that of Mr. evelyn of rubbing the:
Item of a tree jin order to increafe its growth; but other
avocations prevented me till the laft fpring: when, as
foon as the buds began to fwell, I wafhed my tree round
from the ground to the beginning of the head; viz. be-
tween thirteen and fourteen feet in height. This was
done fir ft with water and a ftiff fhoe-brulh, until the
tree was quite cleared of the mofs and dirt ; then I only
wafhed it with a coarfe flannel. I repeated the wafhing
three, four, or five times a week, during all the dry time
of the fpring and the fore-part of the fummer ; but after
the rains were frequent, I very feldom wafhed. The un-
wafhed tree, whofe growth I propofed to compare with
it, was (at five feet from the ground) before the laft year’s
increafe, 3 ft. 7 in. fihs ; and in the autumn, after the
7 year’s

wq/hing and rubbing the Stems of Trees. 1 3
year’s growth was compleated, 3 ft. 9 in. ~th ; viz. in-
creafe 1 in. T^ths. The wafhed tree was laft fpring 3 ft.

7 in. -r^ths, and in the autumn it was 3 ft. 9 in. f^ths ; ,
viz. increafe 2 in. ^ths, that is, one -tenth of an inch ,
above double the increafe of the un wafhed tree. As the .
difference was fo great, and as fome unknown 1 accident
might have injured the growth of the unwafhed tree, I
added the year’s increafe of five other beeches of the fame
age (viz. all that I had meafured), and found the aggre-
gate increafe of the fix unwafhed beeches to be 9 in.-^ths,
which, divided by fix, gives one inch and five -tenths and
an half for the growth of each tree ; fo the gain by waffl-
ing is nine-tenths and an half. To make the experiment
fairly, I fixed on two of my largeft beeches, fown in
1-741, and tranfplanted into a grove in 1749. The
wafhed tree had been, from the firft year, the largeft
plant till the year 1767, when its rival became and con-
tinued the largeft plant, until I began towafh the other:
therefore I fixed on the lefs- thriving tree as the faireft
trial. The trees were nearly of the fame height and.
fhape, fpreading a circle of about fifty feet diameter. I
think it necefiary to mention thefe circumftances ; for I
know by- experience, that a fhort and fpreading tree,
having ample room, v/ill increafe twice or three times,
and perhaps four times as much, as a tail ftnail-headed,

tree.

14 'Mr. mar.sham on thv JJfefulnejs , See.
tree of the fame age, that ftands near other trees. Thus
my wafhed beech increafed above fix times as much as
Mr. drake’s beautiful beech at Shardeloes, though that
.tree feemed in good health when I law it in 1759 anc^
<1766. But it increafed only 2 in. -^ths in thofe feven
years; which may perhaps be owing to its vaft height,
being feventy-four feet and a half to the boughs (as the
late knight of the fliire for Suffolk, Sir john rous, told
me that Mr. drake had informed him) only fix feet and
four inches round, and having a fmall head, and little
room to fpread.

Stratton, 061. 29, 1775.

[ 15 3

III. Difcoveries on the Sex of Bees , explaining the Manner
in which their Species is propagated’, with an Account
of the Utility that may be derived from thofe Difcoveries
by the adlual Application of them to Practice. By Mr.
John Debra w, Apothecary to Addenbrook’s Hof pit al at
Cambridge, and Member of an Oeconomical Society in
the Principality 0/ Liege in Weftphalia. Communicated
by the Rev. Nevil Mafkelyne, B, D. F. R. S. and AJlro-
nomer Royal.

Read Nov. 21, r | '1HE republic of bees has at all times-

gained uni verbal efteem and admi-
ration : their culture, an object fo worthy of our atten-
tion, has attracted and ftill does engage that of many of
the learned, and has arrived at a confiderable degree of
improvement of late years; but their mode of propa-
gating their fpecies teems to this day to have baffled the
ingenuity of ages in their attempts to difeover it. The
moil; fkilful naturalifts have been ftrangely milled in
their opinion, that the bees, as well as the other tribes
of animals, are perpetuated by copulation ; though they

acknowledge

1 6 Mr. DEBjRAw’s Di/cover ies

.acknowledge that they have never been able to detect
■them in the act.

pliny., who waslikewife of the fame opinion, that
in this particular they do not differ from other animals,
obferves, “ Jpium coitus vifus efl nunquam." Swammer-
dam, that fagacious obferver, having never been . able to
difco.ver it, entertained a notion, that the female or queen
bee .was fecundated without copulation; that it wras fuf-
ficient for her to be near the males ; that a vivifying aura,
•exhaling from the body of the males, and abforbed by
•the female, might impregnate her eggs. At laft the in-
comparable rea.umur thought he had in a great mea-
f ure. removed the veil, and brought their manner of ge-
nerating nearly to a proof. This part of phyfics has
been the principal objedt of my refearches for feveral
years paft, having been infenfibly engaged in it by the
pleafure I took in fo curious an inquiry; and although
this purfuit has been attended with more difficulties and
<embaraffments than can be well imagined, I have not
•been difcouraged, and have carefully avoided launching
into conjectures. To introduce a new fyflem in the dod/trine
.of bees, which in a great meafure contradicts all former
received opinions, requires, previous to its appearance,
;.every fandtion the various experiments, fuccelsfully re-
peated, can poffibly give it. The refults of thofe experi-
ments,

on the Sex of Bees. 17

ments, made all in glafs-hives, which carry with then*
an entire evidence, afford fufficient reafons to aflert, that
bees belong to that clafs of animals among which, al-
though they have fexes, a true copulation cannot be
proved ; and that their ova, like the fpawn of fifties, moil
probably owe their fecundation to an impregnation from
the males, as will appear in the fequel of this narrative.

I am not a little pleafed to find that the celebrated ma-
raldi had fucli a notion, and I lament his neglecting to
confirm it. He fays, in his Obfervations upon Bees , in the
Hiftory of the Academy of Sciences for the year 1712,
p. 332: Nous n'avons pu. decouvrir jufqu' a prefent de
quelle maniere fe fait cette fecondation,Ji deft dans le corps
de la femelle , ou bien ft c'eft a la maniere dcs poijfons, apres
que la femelle a pofe fes oeufs: la matiere blanchatre dont
Voeuf eft environne au fond de l' alveole peu de temps apres
fa naijfance, femble conforme a la dernier e opinion , auffi-
bien que les remarques faites plufteurs fois d'un grand
nombre d'ceufs qui font reftes infeconds au fond de I'al-
veole autour defquels nous n’avons point vu cette matiere.
(i We never yet were able to difcover in what manner
“ this fecundation is performed; whether it is in the body
“ of the female, or whether it is after the manner of
u fifties, after the female or queen-bee has depofited
“ her eggs : that liquid whitifh fubftance, with wrhich

Vo L. LX VII. D “each

1 8 Mr. deb raw’s Difcoveries

t{ each egg is fur rounded at the bottom of the cell a
“ little while after its being laid, feemingly eftablilhing
u this laft opinion, as well as the frequent remarks made
“ of a great number of eggs remaining barren in the cell,
M round which we could not fee the above-mentioned

whitifh fubftance.”

This ingenious naturalift, by a nice examination of
the ftruCture of the drones, had, as well as Swammer-
dam, difcovered fome refemblances to the male organs
of generation; and from thence conjectured, they were
the males of the bee-infeCt ; but he owns, with the reft,
that he never could difcover them in the aCt of copu-
lation.

i , . . , i

Having flood the trials of fo many prying eyes in
every age, the bees, as has been obferved by an ingenious
author, had gained the character of an inviolable chaftity,
till reaumur blafted their reputation. He makes the
queen no better than a messalina though he could
fee no more than what would raife a mere jealoufy or
generate fufpicions.

In order to be the better underftood in the relation of
my own experiments on the fecundation of bees, I here
premife the outlines of the opinions adopted by the above-
mentioned naturalifts on that head. They aflert that the

[a] Vid. juvenal. Sat. vi. ver.

•queen

on the Sex of Bees. i g

queen is the only female in the hive, and the mother of
the next generation; that the drones are the males
by which fhe is fecundated; and that the working
bees, or bees that collect wax on the flowers, that knead
it and form from it the combs and cells which they after-
wards fill with honey, are of neither fex.

But of late Mr. sciiirach, a German naturalift, has
given us a very different view of the clafles that confti-
tute the republic of bees, in an ingenious publication in
his own language, under the title of Bhe Natural Hi/lory
of the Queen of the Bees , which has been fince tran dated
into French ; an account of which has been given in the
Monthly Review, from which I beg leave to relate the
author’s dodtrine with regard to the working-bees only;
the quality and functions of the drones being points
which do not appear to be yet fettled by Mr. schirach
himfelf. He affirms, that all the common bees are females
in dilguife, in which the organs that diftinguifti the fex,
and particularly the ovaria , are obliterated, or at leaft,
through their exceffive minutenefs, have not yet been
obferved : that every one of thofe bees in the earlier pe-
riod of its exiftence is capable of becoming a queen-bee,
if the whole community ffiould think proper to nurfe it
in a particular manner, and raife it to that rank. In

D a fhorf,

2o Mr. debraw’s Difcoveries

fhort, that the queen-bee lays only two kinds of eggs ;
viz. thofe that are to produce the drones, and thofe from
■which the working-bees are to proceed.

The trials made by Mr. schirach feem to evince the
truth of his conclufions in the moft fatisfaCtory manner,
Angular as they appear to be at firft fight; and indeed
in my own judgement, from the conftant happy refult
of my numerous experiments, which I began near two
years before Mr. schirach’s publication, and repeated
every feafon fince, I am enabled to pronounce on their
reality.

Chance I own befriended me in that difcovery, whilft
I was moft anxioufly endeavouring to afcertain the ufe of
drones. It was in the fpring of the year 1770, that I for
the firft time difcovered what maraldi had only con-
jectured, I mean the impregnation of the eggs by the
males, and that I was made acquainted with the difference
of fize in the drones or males obferved by maraldi in his
Obfervations upon Bees , inferted in the Hiftory of the Royal
Academy of Sciences for the year 1 7 1 2, p. 333. in thefe
words :

Nous avons trouve depuis peu une grande quantite de
bourdons , beaucoup plus petits que ceux que nous avions
rentarque auparavant , et qui ne furpaffent point la gran-
deur des petit es abeilles\ de forte qu'il n'auroit pas ete aife

de

on the Sex of Bees. 2 r

de les dijlinguer dans cette ruche de abeilles ordinaires,fans
le grand nombre que nousy en avons trouve. II fepourroit
bien faire que dans les ruches ou Von riapas trouve de gros
bourdons, il y en eut de ces petit s, et qu’ils y aient ete con *
fondus avec le rejle des abeilles , lorfque nous ne favions
pas encore qu’ily en eut de cette taille. “We have of
“ late found a great quantity of drones much fmaller
“ than thofe we had formerly obferved, and which do not
“ exceed in lize the common bees ; fo that it would not
“ have been eafy to diftinguifh them in that hive from
“ the common bees, had not the quantity of them been
“ very confiderable. It might certainly have happened
“ that in thofe hives, where we have not been able to.
“ difcover large drones, there were a great number of
“ thofe little ones, which may have been intermixed
“ among common bees when we were yet ignorant that
“ any fuch fmall drones were exifting.”

reaumur himfelf, p. 591. of his Natural Hiftory of
Infects, fays, “We have likewife found drones that were
“ no bigger than the common bees.”

They have notwithftanding efcaped the obfervation,
of Mr. schirach, and of his friendMr. hattorf mem-
ber of an Academy in Lufatia, who, in a memoir he
prefented in the year 1769, annihilates entirely the
ufe of drones in a hive; and advances this lingular

opinion,.

Mr. Debra w’s Difeovaries

opinion, that the queen-bee of a hive lays eggs which
produce young ones, without having any communication
with the drones. For what purpofe fhould wife nature then
have furnifhed the drones with that large quantity of
feminal liquor? To what ufe fo large an apparatus of fe-
cundating organs, fo well defcribed by Reaumur and

MARALDI?

But I beg leave to remark, that thofe gentlemen fecm to
have drawn too hafty conclufions from their experiments,
in rejecting the drones as bearing no lhare in the propaga-
tion of thofe infedls. Their obfervations, that hives are
peopled at a time of the year when there are no drones
in being, is no ways conclufive; as it is evident, that they
had feen none but drones of a large lize, their lilence on
the difference in the fize of them juftifying my remark.
But to refume the narrative of my experiments : I had
watched my glafs-hivesw with indefatigable attention
from the moment the bees, among which I had taken care
to leave a large number of drones, were put into them,
to the time of the queen laying her eggs, which gene-
rally happens the fourth or fifth day. I obferved the
firft or fecond day (always before the third) from the
time the eggs are placed in the cells, that a great number

(b ) Glafs- hives were ufed in preference to boxes, for a purpofe too obvious to
need explaining.

©f

on the Sex of Sees, 23

of bees, fattening themfelves to one another, hung clown
in the form of a curtain from the top to the bottom of the
hive, in a fimilar manner they had done before at the
time the queen depofited her eggs ; an operation which
(if we may conjecture at the inftinCts of infeCts) feems
contrived to hide what is tranfaCting : be that as it will,
it anfwered the purpofe of informing me that fome-
thing was going forward. In fact, I prefently after per-
ceived feveral bees, the fize of which through this thick
veil (if I may fo exprefs myfelf) I could not rightly dif-
tinguifh, inferting the pofterior part of their bodies each
into a cell, and finking into it, where they continued but
a little while. After they had retired, I faw plainly with
the naked eye a fmall quantity of a whitifh liquor left in
the angle of the balls of each cell, containing an egg : it
was lefs liquid than honey, and had no fweet tafte at all.
Within a day after, I found this liquor abforbed into the
embrio, which on the fourth day is converted into a fmall
worm, to which the working-bees bring a little honey
for nourifhment, during the firft eight or ten days after
its birth. After that time they ceafe to feed them ; for
they fiiut up the cells, where thefe embrios continue in-
clofed for ten days more, during which time they un-
dergo various changes too tedious here to defcribe.

24. Mr. d eb raw’s Bi/cover ies

To evince the reality of this obfervation, anti to prove
that the eggs are fecundated by the males, and that their
prefence is neceflary at the time of breeding, I proceeded
to the next experiments. They confifted in leaving in a
hive the queen with only the common bees, without any
drones, to fee whether the eggs fhe laid would be pro-
lific. I accordingly took a fwarm, iliook all the bees
into a tub of water, and left them in it till they were
quite fenfelefs, which gave me an opportunity to dif-
tinguifh the drones without any danger of being ftung.
After I had recovered the working-bees and their queen
from the ftate they were in, by fpreading them on
brown paper in the fun, I replaced them in a glafs-hive,
where they foon began to work as ufual: the queen
laid eggs, which I little fufpected to be impregnated,
as I thought I had feparated all the drones or males, and
therefore omitted watching the bees ; but at the end of
twenty days (the ufual time of their hatching) I found
to my furprize feme of the eggs hatched into bees, others
withered away, and feveralof them covered with honey.
I immediately inferred that feme of the males, having
efcaped my notice, had impregnated only part of the
eggs ; but, in order to convince myfelf of the truth of
my fuppofition, I thought it necedary to take away all
the brood-comb that was in the hive, in order to oblige

the

3

on the Sex of Beesr 2 5

the bees to provide a frefh quantity, being fully deter-
mined to watch narrowly their motions after new eggs
fhould be depoiited in the cells. This was done accord-
ingly, and at lail the myftery was unravelled. On the
fecond day after the eggs were placed in the ceils, I per-
ceived the fame operation which I have related in a for-
mer experiment; I mean, the bees hung down in the
form of a curtain, while others thruft the poflerior part
of their body into the cells : I then introduced my hand
into the hive, broke off a piece of the comb containing
two of thofe infects, and kept them for examination. I
found in neither of them any fling (a ciicumfiance pe-
culiar to drones only) and upon difledtion, by the help ox
a dollond’s microfcope, difcovered in them the iour cy -
lindrical bodies, which contain the glutinous liquor of a
whitifh colour, obferved by maraldi in the large drones.

Having till then never obferved any difference in the
fize of drones, I immediately perufed the Memoirs on
Bees publifhed by Meff. maraldi and Reaumur, and
found that they had Remarked it frequently. ? have in-
ferted in a preceding page the fubftance of tneii obferva-
tions on that head, as taken from their writings. The
reafon of that difference muft I doubt be placed amongft
other arcana of nature. I found myfelf therefore unuci
aneceflity in my next experiments to be more particuku
V0L0 LXVII. E 311

2 6 Mr. debraw’s Difcoveries

in deftroying the males, even thofe which might he fuf-
pecfted to be fuch.

I once more immerfed all the fame bees in water ; and,
when they appeared to be in a fenfelefs ftate, I gently
preffed every one of them between my fingers, in order
to diftinguifh thofe armed with flings from thofe that
had none, which laft I might fufpedt to be males. Of
thefe I found fifty-feven, exactly of the fize of common
bees, yielding a little whitifh liquor on being preffed be-
tween the fingers. I killed every one, and replaced the
fwarm in a glafs-hive, where they immediately applied
again to the work of making cells; and on the fourth
or fifth day, very early in the morning, I had the plea-
fure to lee the queen-bee depofiting her eggs in thofe
cells, which fhe did by placing the pofterior part of her
bodv in each of them. I continued on the watch molt

J

part of the enfuing days, but could difcover nothing of
what I had feen before.

The eggs, after the fourth day, inftead of changing in
the manner of caterpillars, were found in the fame ftate
they were in the firft day, except thaefome of them were
covered with honey. But a very lingular event happened
the next day about noon : all the bees left their own hive,
and were feen attempting to get into a neighbouring com-
mon hive, on the ftool of which I found their queen dead,

3 having

on the Sex' of Bees. 27

having no doubt been flain in the engagement. The
manner in which I account for this event is as follows :
the great delire of perpetuating their fpecies, which is
mofl: obfervable in thefe infects, and to which end the
concurrence of the males feems fo abfolutely neceflary,
made them defert their own habitation where no males
were left, in order to fix their refidence in a new one, in
which, there being a good flock of males, they might the
better accomplifh their purpofe. If this does not yet
eftablifh the reader’s faith of the neceffity of the males
bearing a fhare in the fecundation of the ova , the next
experiment cannot I prefume fail to convince him.

I took the brood-comb which, as I obferved before, had
not been impregnated; I divided it into two parts; one I
placed under a glafs-bell N° 1 . with honey-comb for the
bees’ food; I took care to leave a queen, but no drones,
among the common bees I confined in it. The other piece
of brood-comb I placed under another glafs-bell N° 2 .
with a few drones, a queen, and a number of common
bees proportioned to the fize of the glafs ; the reft I dif-
pofed of as before. The refult was, that in the glafs N°
1 . no impregnation happened ; the eggs remained in the
fame ftate they were in when put into the glafs; and,
upon giving the bees their liberty on the feventh day,
they all flew away, as was found to be the cafe in the for-

E 2

mer

i>8 Mr. debraw’s Difcoveries

mer experiment: whereas in the glafs N° 2. 1 faw, the
very clay after the bees had been put under it, the impreg-
nation of the eggs by the drones in every cell containing
eggs; the bees did not leave their hive on receiving their
liberty ; and, in the courfe of twenty days, every egg un-
derwent all the above-mentioned neceffary changes, and
formed a pretty numerous young colony, in which I was
not a little ftartled to find two queens.

Fully fatisfied concerningthe impregnation of the eggs
by the males, I defifted for the prefent from any further
experiments on that head, being exceedingly anxious to
endeavour to account for the prefence of this new queen.

I conjectured that either two queens, inftead of one,
mull have been left among the bees I had placed under
that glafs ; or elfe that the bees could, by fome particular
means of their own, transform a common fubjedl into a
queen;

In order to put this to the tell, I repeated the experi-
ment with fome variation. I got four glafs-hives blown
flat, which I thought preferable to the bell-fhaped ones'
I had ufed before, as> I could with thole better examine
what was going forward., I took a large brood-comb
from an old hive, and, after having divided it into feveral
pieces, I put fome of them, containing eggs, worms, and
nymphs, with food, viz. honey &c. under each of the

glaflesj:

on the Sex of Bees . i §

glalTes ; and confined within each a fufficient number of
common bees, among which I left fome drones, but took,
care that there fhould be no queen.

The bees finding themfelves without a queen, made a,
ftrange buzzing noife, which lafted near two days; at the.
end of which they fettled and betook themfelves to work :
on the fourth day I perceived in each hive the beginning .
of a royal cell, a certain indication that one of the inclofed
worms would foon be converted into a queen. The con-
firuction of the royal cell being nearly accomplifhed, I
ventured to leave an opening for the bees to get out, and
found that they returned as regvdarly as they do in com-
mon hives, and fhewed no inclination to defert their ha-
bitation. But,, to be brief, at the end of twenty days, I ob-
served four young queens among the new progeny.

On relating the refult of thefe experiments to a,
member of this univerfity, well converfant in the na-
tural hiftory of bees, he deemed it neceflary, that they
ihould be repeated, in order the better to eftablhh the
truth of a fa£t feemingly fo improbable, that the eggs
deftined by nature to produce neutral or common bees,
fhould be transformed into females or queens. He flatted ;
an objection to me, which by the publication of Mr.
schirach appearing a little time after, feems to have
been pointed out to that author alfo by Mr. withelmi,

his •

Mr. debraw’s Difcoveries

his brother-in-law, namely, that the queen-bee of a hive,
befides the eggs which the depofits in the royal cells,
might alfo have laid royal or female eggs either in the
common cells, or indifcriminately throughout the dif-
ferent parts of the hive. He further fuppoled, that in the
pieces of brood-comb, which had been fuccefsfully em-
ployed in the laft experiments for the produdtion of a
queen, it had conftantly happened, that one or more of
thefe royal eggs, or rather the worms proceeding from
them, had been contained.

But the force of his objection was removed foon after
by the fame fuccefs having attended a number of other
experiments which I lince made, an account of which
would take up too much room here ; and this gentleman,
together with Mr. schirach’s brother-in-law, was at laft
brought to admit, that the working-bees are inverted with
a power of railing a common fubjeft to the throne, when
the community Hands in need of a queen ; and that ac-
cordingly every worm of the hive is capable, under cer-
tain circumftances, of becoming the mother of a genera-
tion: that it owes its metamorpholis into a queen, partly
to the extraordinary fize of the cell, and its particular
pofition in it; but principally to a certain nourilhment
appropriated to the occafion, and carefully adminiftered
to it by the working-bees while it is in the worm-ftate,

by

on the Sex of Bees. 31

by which, and poffibly other means as yet unknown, the
developement and expanfion of the germ of the female
organs, previoufly exiting in the embryos, is effected,
and thofe differences in its form and fize are produced,
which afterwards fo remarkably cliff inguifh the queen
from the common working-bees. And finally it appears
evident, from the experiments made by Mr. schirach
and myfelf, that the received opinion, that the queen lays
a particular kind of eggs, appropriated to the production
of other queens, is erroneous. 1 am not a little flattered
with the fimilarity of my difcoveries with thofe of the
ingenious German naturalift, in proving the fex of the
common bees ; although we fo widely differ in what re-
lates to the ufe of the males, whom, as we have feen be-
fore, he imagines to be quite ufelefs. I am alfo not a little
pleafed to find, that our experiments on the production
of a queen from a common embryo agree fo well.

I fhall now beg leave to point out the advantage that
may accrue to the public from thefe obfervations.
which is that of forming artificial fwarms or new co-
lonies; or in other words, of furnifhing the means to
bring on a numerous increafe of thofe ufeful infects : an
object of fome importance to this kingdom, as being
the only means to prevent the annual exportation of con-
fiderable fums in the purchafe of wax, a great quantity

of

:3'»

Mr. deb raw’s Difcoveries.

of which is loft every feafon for want of keeping up a
fufficient ftock of bees to collect it.

The practice of this new art, Mr. schirach tells us,
has already extended itfelf through Upper Lufatia, the
Palatinate, Bohemia, Bavaria, Silefia, and even in Poland.
In fome of thofe countries it has excited the attention
and patronage of government; and even the Emprefs of
Ruffia has thought it of fuch importance, that fhe has
fent a perfon to Klein Bautzen, to be inftruded in the
general principles, and learn all the nunutia ot this new
art.

The narrow limits of this paper do not permit me
here to give an account of Mr. schirach’s ingenious ob-
fervations. I beg leave to refer the curious reader to the
work itfelf, which, with the reviewers, I with was tranf-
lated into the Englifh language, as it contains many par-
ticulars highly deferving the notice of the fpeculative
naturalift, as well as of thofe who cultivate bees either
for profit or amufement.

C 33 1

IV. An Account- of a Portrait of Copernicus, prefented to
the Royal Society by Dr. Wolf of Dantzick: ex-
tracted from a Letter of his to Mr. Magellan, F. R. S.

DEAR SIR,

{lead Dec. 7, r
1776.

Dantzick,
April 7, 1776*

T~^HE captain who will deliver this to you,
“** will alfo put into your hands a copy of
an original portrait of the famous Copernicus, which I
beg you will prefent to the Royal Society, as a teftimony
of my devotion and attachment to that refpeftable body.
The original, from which it is copied with the greateft
accuracy, is in the poffeffion of the Chamberlain hus-

SARZEWSKI,

Avis touchant un . 'trait de Copernic, prefente d la Societe
Royale, par M. le * ■. Wolf de Danzic : extrait d'une Lettre
du dit Dr. a M. de Magellan, Membre de la Soc. R.

Monfieuret tres cherami, Danzic, le 7 Avfil, 1776.

LE capitaine qui vous delivrera celle-ci, vous appoitera en meme terns la
copie d’un portrait du fameux copernis. que je vous prie de prefenter
a votre illuftre Societe Royale, comme un temoignage de mon devouement et
refpect pour cet illuftre Corps. Le poffeffeur de l’original, dont le portrait fut
copie avec la plus grand attention, eft M. le Cluunbellau husjarzewski. II a
Vol. LXVII, F dej»

34 Dr. wolf’s Account of

sarzewski, who has already refufed one hundred ducats
for it, and will not part with it at any rate during his lifey
but intends to bequeath it me after his death ; for which
reafon there is no probability of my ever pofleffing
it, as he is likely to furvive me many years. We
have a portrait of Copernicus in the great church at
Thorn in a kind of maufoleum, created about thirty
years after the death of that great man, by a phylician
of that town, who is faid to have been one of his relations.

hartknoch has inferted a print taken from this por-
trait in his Chronicles of Pruffia. Our original has been
compared with that of the maufoleum, and the features
of the face are found to be perfectly fimilar, but there i9
a great difference in the drefs. That at Thorn reprefents
him kneeling before an altar, in the attitude of a prieft
officiating ; in ours he is cloathed in fur, with his hair

more

deja refufe ioo ducats, et ne le cedera pas fa vie durant pour aucun prix : mais
il rue le veut leguer apres fa morte. C’eft a dire tres probablement apres la
mienne: de forte qu’il n’y a rien a efperer de ce cote-ci. Nous avons un por-
trait de copernic dans la grande Eglife de Thorn, dans une efpece de
maufolee, erige une trentaine d’annees apres la mort de cet homme celebre, par
»n medecin de la ville, qu’on dit avoir ete un de fes parents.

hartknoch a fait graver ce portrait, et l’a infere dam fa Chronique de la
Pruffe. Notre original a ete compare fur le lieu avec celui du maufolee, et on
a trouve les traits du vifage abfoiument les memes : mais l’habillement eft tres
different.’ Celui de Thorn le reprefente devant I’autel en fon£lion de pretre.

Dans

a Portrait of copernicus, 35

more carefully dreffed, and as it were in a habit of
ceremony. The painter of it was certainly one of the
old Italians, as will appear by comparing it with other
works of thofe matters ; for inftance, it is known
that the painters of thofe times, and even Raphael,
never gave to the eyes that brightnefs which the 1110ft
indifferent artifts within this century never fail to exprefs
in their portraits : not but what the ferene and feemingly
inanimated countenances of the former artifts came
nearer to nature than the fparkling eyes which are now
all the fafhion. This however is a proof that the por-
trait is at leaft one hundred and fifty years old ; the in-
fcription fhews that the painter was an Italian; and it
mutt further be obl'erved, that it is now two centuries
fince they left off" painting on wood.

The

Dans le notre il eft habille en peliffe, avec Ies cheveux de la tete plus foigneufe-
ment arranges et coupes, comme en habit de parade. Le pinceau eft furement
Itaiien du vieux terns en queftion, comme on trouvera en regardant d’autres
de ce terns et les comparant avec celui-ei. Par exemple, on fait que les pein-
tres dans ce vieux terns, raeme Raphael, ne favoientpas encore donner aux yeux
cette vivacite, que le plus mediocre peintre depuis plus d’un fiecle, ne manque
pas de donner a fes peintures. Je ne dis pas que les vieux peintres n’approchent
pas plus de la nature avec leurs yeux tranquiles fans feu ; mais ils deplaifent a
notre iiecle, qui ne veut que des yeux petillants. Au moins c’eft la marque
d’une anciennete plus grande qu’un fiecle et demi. L’infcription fait voir
que le peintre etoit Itaiien. II y a deux liecles qu’on a celfe de peindre fur du
bois.

F 3

L’hilloire

36 Dr. wolf’s Account of

The lhftory of this portrait is as follows. It was for-
merly in the collection of Saxe Gotha, where it was al-
ways confidered as an original, which is even faid to ap-
pear from the archives of that court, and is the more
probable, as the prince-bifhop of Warmia, who- obtained
it from the late duke of Saxe Gotha, was too good a con-
noiffeur and too cautious to be deceived in this refpect.
That bifhop being at Gotha in the year 1735, obferved
this portrait in the gallery of that palace; the proofs that
were produced of its authenticity made him very defirous
to acquire it. He at length obtained it by a kind of theft
which it was neceffary to commit on the cathedral of
Warmia, in which there was a very old portrait of one
of the anceftors of the dukes of Saxe Gotha, who had
been bilhop of that fee, and whofe picture was wanting

in

L’hiftoire de notre original eft la fuivante. II a ete conferve dans la collec-
tion des dues de Saxe Gotha, dans le chateau du meni£ nom, toujours avoue
comme un veritable original: on pretend meme prouve comme tel par les
archives \ ce qui eft fort croyable, vu que le prince eveque de Warmie, qui l’a
obtenu du due defunt, etoit trop circonfpe£l et trop bon connoiffeur pour s’en
iaiiTer impoler. Enfin c^eft apres les paroles du prince eveque, que je fais cette
alfertion. Ce fut environ l’annee 1735 qu’ etant a Gotha, il remarqua ce
portrait dans la gallerie du due. Les preuves qu’on lui fit de fon authenticite,
augmenterent fon envie de le poffeder. II l’obtint enfin par un vol qu’il fallut
faire a la Cathedrale de Warmie, ou fe trouvoit un tres ancien portrait d’un des*
ancetres du due de Saxe Gotha, qui etoit jadis eveque de Warmie, et dont le
gortrait manquoit dans la. collection des portraits de fa famille. On fit done un

echange

a Portrait of Copernicus.

37

in the duke’s collection of the portraits of his family.
An exchange was accordingly made of the two originals,
and the biftiop has ftnce bequeathed that of Copernicus
to his favourite Mr. hussarzewski.

The copy I herewith fend you is very exact in every
refpect, except that I have glued three wooden lifts on
the back of the board to prevent its warping. After my
copy was taken, the proprietor of the original thought
proper to have it repaired and varnifhed, and they are
now fo much alike that it is fcarce poflible to difcern any
difference. The name of my painter is lorman of Ber-*
lin, an artift of fome reputation.

echange des deux originaux. Le prince eveque grabowski enfin a laiffe celui
de copernic a fon favori M. hussarzewski.

La copie eft abfolument la memo que l’original : excepte que j’ai fait coller
trois regies fur le derriere de la table pour empecher fon courbiffement. De-
puis que ma copie a ete tiree, M. hussarzewski, croiant bien faire, a fait
renouveller fon original, c’eft a dire, y mettre du vernis : et a6luellement il eft
£ bien le meme que la copie, qu’on peut a peine s’appercevoir de la moindre
difference, Mon peintre eft M. lorman de Berlin, affez celebre dans fon art,.

3§

Dr. sparrman’s Account of

V. An Account of a Journey into Africa from the Cape
of Good-Hope, and a Defer ipt ion of a new Species of
Cuckow. By Dr. Andreas Sparrman, of the Royal Aca-
demy of Stockholm, in a Letter to Dr. John Reinhold
Forfter, F. R. S.

DEAR SIR,

Gottenburg,
Sept. 16, 177^

Head Dec. 19, TOEING returned to my native country
J_3 after an abfence of five years from it,
I will endeavour to give you a fhort account of my expe-
dition into Africa, which I undertook foon after parting
with you at the Cape of Good-Hope. The voyage round
the world, of which I fhared the perils and pleafures
with you, had only made me more eager to continue my
rambles in quell of new difeoveries. I fet out therefore
from the neighbourhood of the Cape-town in the be-
ginning of Auguft 1772b with no other company than
the fon of the Dutch lieutenant emelman, who had
formerly accompanied my learned friend Dr. thunberg
on a fimilar journey, and fome Hottentots who took care
of my oxen.

1 The

\

his Journey into Africa. 39

The firft misfortune I met with was the lofs of the
thermometer which you had left me, and which broke
before I had reached the hot-baths. This was only a
prelude to greater diftrefles. The drought was fo violent
this year, that the like had not been experienced in the
colony within the memory of man, and it obliged the
inhabitants to leave their country-feats. *A great part of
their cattle perifhed for want of grafs and water, and I
have frequently buffered the moft raging third; in the
hot defarts which I traverfed; but I was too well feafoned
during the voyage to dread the hardfhips of a fcanty
fubfiftence, the fatigues of travelling, or the power of
the climate. The moft fenfible misfortune which the-
dry feafon brought along with it, was the defolation of
the vegetable kingdom. Far from being fo fortunate as
Dr. thunberg, who has added above athoufand fpecies
to the Flora Capenfis , I found every thing burnt up, and
only in the thickeft forefts met with fome perennial
plants which were new to me, and which, upon a revifal
of that gentleman’s herbal, I believe are likewife un-
known to him. Of thefe I propofe to fend you fpeci-
mens as foon as I can find time to bring my collecftion
into fome kind of order. On the other hand, I have
been fortunate with animals, and efpecially in the clafs
of quadrupeds. I fhall not fpeak of lions and other beafts

of

40- Dr. sparrman’s Account of

of prey, which I have frequently feen in broad day-light,
and heard roaring about me at night, though they never
ventured to attack our cattle. But it was chiefly among
the antelopes and animals of that fort that I hunted.
Mr. emelman and myfelf, with nine hottentots, a wag-
gon drawn by feveral pairs of oxen, and feveral hunting
horfes, happily traverfed a defart of fifty miles, where
we had greater fport than any German prince could ever
boaft of. On that route I penetrated farther into the
country than any of my predeceflors, having gone one
hundred miles beyond the laft Chriftian’s or Dutchman’s
hut, into the diftrift of the Yellow' or (as they are vulgarly
called) Chinefe Hottentots.

The great buffaloes which inhabit the wrilds of Africa,
do not appear to me to differ in any refpedt from the North
American Bifon , although I have feen great numbers of
them. I have likewife found a fpecies of pole-cat on that
continent which linn.<eus calls Viverra Putorius , con-
trary to M. de buffon’s opinion, who feems to confine
this animal and its fpecies to America. By the fea-fide I
was fortunate enough to catch a -Manatee alive, not with -
ftanding the difficulty which muff attend the capture of
fuch an umveildy animal. There I likewife faw fome
iflands, on which I was told an Englifh fhip had been
loft. Thefe 1 fufpedfted at firft to be the Doddingtons ; but

afterwards

v- his Journey into Africa. 41

afterwards had reafon to doubt it, thofe iflands being
fuppofed to lie in a more foutherly latitude.

I have had opportunities of making many curious and
Valuable Obfervations relative to the different tribes of
Hottentots, their oeconomy, hunting-matches, and other
puftoms.; an account of which, together with fome re-
marks on the natural hiitory of the elephant, the rhino-
ceros, and other animals, I intend to prepare for the prefs.
I am poffefied of an accurate map of that part of Africa
which I have vifited, containing all the hills, together
with the fmalleft rivulets, as far as the Bay de la Goa,
which, I think, will be a great addition to the work. I
only regret that I was not able to draw the objedls of
natural hiitory, and have an hundred times wifhed that
your fon had been with me for this purpofe.

As I had been upwards of nine months on this journey,
at my return to the Cape I found that my acquaintance had
given up all hopes of feeing me again, having had no tidings
of me for fo lbng a fpace of time. Notwithstanding the
many dangers to which I had been expofed on this expedi-
tion, failure you I was greatly tempted to ftay another year,
in hopes of being more fuccefsful in botanical difcoveries.
However, the profpect of fecuring the fpoils which I had
collected, prevailed on me to relinquifh that fcheme.
Indeed I little thought at that time that the greatest

Vol. LX VII. G danger

^2 Dr. starkman’s Account' of

danger awaited my collection in Sweden. A few days
ago a great part of it has been damaged here by fire,
which has been particularly fatal to my fluffed birds,
having deftroyed fome which were not yet defcribed.

As I am well acquainted with the pleafure which every
new difcovery in the hiflory of nature gives you, I take
this early opportunity of exprefling the readinefs with
which I wifh to contribute to your fatisfa&ion, and have
fubjoined to this letter an account of a curious bird, a fpecies
of Cuckow, which I have faved out of the fire. I only beg
that you will confider it as an earneft of more important
communications, as foon as the hurry of my affairs will
permit me to bring my papers into order. In the mean
time if you fhould think that account, and the annexed
drawing, worthy the attention of the Royal Society, I
fhould be greatly flattered if you would do me the ho-
nour to lay it before that learned Body.

With the greateft efteem I remain, 8ec,

THE

bis Journey into Africa.

43

THE HISTORY OF THE HONEY-GUIDE, OR

CUCULUS INDICATOR.

THIS curious fpecies of Cuckow is found at a confi-
de r able diftance from the Cape of Good-Hope, in the in-
terior parts of Africa, being entirely unknown at that
fettlement. The firft place where I heard of it was in a
wood, called the Groot Vaader's Bofch , the Grand Fa-
ther’s Wood, fituated in a defart near the river which the
Hottentots call T’kaufkai. The Dutch fettlers there-
abouts have given this bird the name of Honig-wyzer ,
or Honey-guide, from its quality of difcovering wild-
honey to travellers. Its colour has nothing ftriking or
beautiful, as will appear from the defcription and drawing
annexed ; and its fize is confiderably fmaller than that of
our Cuckow in Europe : but in return, the inftinit which
prompts it to feek its food in a lingular manner, is truly
admirable. Not only the Dutch and Hottentots, but like-
wife a fpecies of quadruped, which the Dutch name a
Rat el ( are frequently conducted to wild bee-hives by
this bird, which as it were pilots them to the very fpot.
The honey being its favourite food, its own intereffc
prompts it to be inftrumental in robbing the hive, as

( a) Probably a new fpecies of badger,

G 2 feme

44 Dr. Sparkman's Account of

fome fcraps are commonly left for its fupport. The morn-
ing and evening are its times of feeding, and it is then
heard calling in a fhrill tone cherr , cherr , which the honey-
hunters carefully attend to as the fummons to the chace.
From time to time they anfwer with a loft whiftle, which
the bird hearing, always continues its note. As boon as
they are in fight of each other, the bird gradually flut-
ters towards the place where the hive is fituated, conti-
nually repeating its former call of cherr, cherr : nay, if it
flioukl happen to have gained a confiderable way before
the men (who may eafily be hindered in the purfuit by
bullies, rivers, and the like) it returns to thenii again, and
redoubles its note, as if to reproach them with their in-
adtivity. At laft the bird is obferved to hover for a few
moments over a certain fpot, and then filently retiring to
a neighbouring bufh or other refling-place, the hunters
are lure of finding the bees nefi in that identical fpot,
whether it be in a tree, or in the crevice of a rock, or (as
is moft commonly the cafe) in the. earth. Whilft the
hunters are bufy in taking the honey, the bird is feen
looking on attentively to what is going forward, and wait-
ing for its lhare of the fpoil. The bee-hunters never fail
to leave a fmall portion for their conductor, but commonly
take care not to leave fomuch as would fatisfy its hunger.
The bird’s appetite being only whetted by this parfimony,

it

a

his Journey into Africa. 45

it is obliged to commit a fecond treafo'n, by difcovering
another bees-neft, in hopes of a better falary. It is fur-
ther obferved, that the nearer the bird approaches the
hidden hive, the more frequently it repeats its call, and
feems more impatient.

I have had frequent opportunities of feeing this bird,
and have been witnefs of the defirudtion of feveral re-
publicks of bees, by means of its treachery. I had
however but two opportunities of fhooting it, which I
did to the great indignation of my Hottentots. From
thole fpecimens (both of which are fuppofed to be
females) I have made the fubfequent defcription. The
inhabitants in general aceufe the fame bird of feme-
times conducting its followers where wild beads and ve-
nomous ferpents have their places of abode : this however
I never had an opportunity of afcertaining myfelf ; but
am apt to believe fuch cafes to be accidental, when dan-
gerous animals happen to be in the neighbourhood of a
bees-neft;

Whilft I ftald in the interior parts of Africa, a neft
was fhewn to me, which feme' peafants allured me was
the neft of a Honey-guide. It was woven of llender fila-
ments or fibres of bark, in the form of a bottle. The neck
and opening hung downwards, and a firing in an arched

fhape

.46 Dr. sparrman’s Account of

fhape was fufpended acrofs the opening, fattened by the
t two ends, perhaps for the bird to perch upon.

’DESCRIPTIO CUCULI I N D I C A T O R I S.

ROSTRUM crafliufculum, verfus bafin fufcum, apice
luteum.

Angulus oris ufque infra oculos extenfus.

Nares poftremee ad bafin roftri, fupremce vicinae
ut carinula dorfali faltem feparerentur, oblongce,
margine prominulo.

Pill aliquot ad bafin roftri, prsecipue in mandibula
inferiore.

Lingua plana, fubfagittata.

Oculorum irides ferrugineo-grifeae.

Palpebra nudae, nigrae.

Pedes nigri, fcanforii. Tibia breves; Ungttes term.es, nigri.
Pileus laete grifeus e pennis brevibus latiufculis.

Guta, Jugulum , Pectus, fordide alba, cum aliquo virore
vix notabili in pedlore.

Dorfum et Uropygium ferrugineo-grifea.

Abdomen , Grijfumque alba.

'Femora tecta pennis albis, macula longitudinali nigra
notatis.

Alarum

bis Journey into Africa. 4.7

Alarum teBrices fuperiores omnes grifeo-fufcae, exceptis
fummis aliquot quae flavis apicibus formant maculam

faepe tedtam.

TeBrices infra alam albidae, harum fupremae ex
albido nigroque maculatae.

Remiges omnes fupra fufci, primarii odlo, fecundarii
fex, fubtus cinereo-fufci. .

Alula grifeo-fufcae.

Cauda cuneiformis, reclricibus duodecim : harum duae
intermediae longiores anguftiores, fupra et infra aeru-
ginofo-fufcae; proximae duae fuliginofae, margine in-
teriore albicantes ; duae utrinque his proximae, albae, ,
apice fufcae, et exterius ad bafin macula nigra notatae ;
extima utrinque reliquis brevior, alba, apice fufca,; .
macula nigra vix ulla ad balin.

Ala complicatae.caudae partem quartam attingunt.

Longitudo ab apice roftri ad extremum caudae circiter r
feptem uncias pedis Anglicani explet.

Rojlrum a ball fuperiore ad apicem femunciale.

flavam in humeris, exiguam, et a plumis fcapularibus

;0 Mr. cavallo’s Account of

VI. An Account of fome new MeBriccil Experiments. By
Mr. Tiberius Cavallo: communicated by Mr. Henley,
F. R. S.

'DESCRIPTION AND USE OF THE ATMOSPHERI-
CAL ELECTROMETER.

Head Dec. 19:, T7' I G. I. represents a' very fimple inftru-

1776. S’

A ment, which I have contrived for
^making obfervations on the electricity of the atmofphere,
and which on feveral accounts feems to be the molt ufeful
inftrunient hitherto invented for that purpoie. a b is a
common jointed fillring-rod, without the lalt or fmallelt
joint. From the extremity of this rod proceeds a {lender
glafs tube c, covered with fealing-wax, and having a cork
d at its end, from wdrich a pith-ball electrometer is fuf-
pended. hgi is a piece 'of twine faftened to the other
extremity of the rod, and fupported at g by a frnall firing
fg. At the end i of the twine a pin is faftened, which,
when puflred into the cork d, renders the electrometer e
uninfulated.

When

fame Electrical Experiments . 49

When I intend to obferve the electricity of the atmo-
fphere with this inftrument, I thruft the pin 1 into the
cork d, and holding the rod by its lower end a, project it
out of a window in the upper part of the houfe, into
the air, railing the end of the rod with the electrome-
ter fo as to make an angle of about 50° or 6o° with
the horizon. In this lituation I keep the inftrument
for a few feconds, and then pulling the twine at h,
I difengage the pin from the cork d, which operation
caufes the firing to drop in the dotted fituation l k, and
leaves the electrometer infulated, and electrified with an
electricity contrary to that of the atmofphere. This done,

I withdraw the inftrument, and examine the quality of
the electricity without any obftruCtion either from wind
or darknefs.

With this inftrument I have made obfervations on the
electricity of the atmofphere feveral times in a day, and
have kept a journal of thofe experiments from the 27th
of September laft to this day.

The following is the molt remarkable part of the
above-mentioned journal, in which I have noted the
electricity of the- electrometer,' that is the contrary of
that in the atmofphere.

The ftroke fignifies as above.

Vol. LXVIL

H

Time

5®

Mr. cavallo’s Account of

Time of Obfervation.

Clouds.

Fog.

Wind.

lOpening of
the Electro-
meter in

Eleftri-

city.

inches.

Oft. 19th,

io§ o’clock.

Cloudy.

f Very little at
\ a diftance.

f Very
l llrong.

1

1^5

Negative.

1 1
2

Heavy clouds.

„ , . —

Violent.

3

4

Pofitive.

2$

Lefs cloudy.

Little.

I

3

Few atadillance.

—

—

T

X

Negative.

8

0

0

—

—

—

061. 31ft,

1 1 poll mer.

—

—

0

I

2.

—

Nov. 6th,

1 1 poll mer.

Very thick.

I

—

From the above-mentioned journal I have deduced the
following general obfervations.

i ft, That there is in the atmofphere at all times a
quantity of electricity ; for whenever I ufe the above
defcribed atmofpherical electrometer it always acquires
fome electricity.

adly, That the electricity of the atmofphere or fogs
is always of the fame kind, namely pofitive; for the
electrometer is always negative, except when it is evi-
dently influenced by heavy clouds near the zenith.

3dly, That the ftrongeft electricity is obfervable in
thick fogs, and the weakeft when the weather is cloudy
and there is a ftrong appearance of rain ; but it does not
feem to be lefs at night than in the day-time.

DESCRIP-

feme EMirkal Experiments*

5*

DESCRIPTION OF THE ELECTROMETER FOR

THE RAIN.

THE rain-eleCfrometer is, in its principle, nothing
more than an infulated inftrument to catch the rain, and
by a pith-ball electrometer to fhow the quantity and
quality of its electricity.

Fig. 2. reprefents an inftrument of this kind, which I
have frequently ufed, and after fever al obfervations have
found to anfwer very well, abci is a ftrong glafs tube
about two feet and a half long, having a tin funnel de
cemented to its extremity, which funnel defends part of
the tube from the rain. The out fide furface of the tube
from A to b is covered with fealing-wax, as alfo that
part of it which is covered by the funnel, fd is a piece
of cane, round which feveral brafs wires are twitted in
different directions, fo as to catch the rain eafily, and at
the fame time to make no refiftance to the wind. This
piece of cane is fixed into the tube, and a flender wire
proceeding from the former goes through the bore of the
tube, and communicates with the ftrong wire ag, which
is thruft into a piece of cork fattened to the end a of the
tube. The end g of the wire ag is formed into a ring, from

H 2 which,

52 Mr. cavallo’s Account of

which I fufpend a more or lefs fenfible pith-ball eledtro-

meter as occafion requires.

This inftrument is fattened to the fide of the window-
frame, where it is fupported by ftrong brafs hooks at
cb. The part H hands out of the window, with the end
F a little elevated above the horizon. The remaining part
of the inftrument pafies, through a hole in a glafs of the
fiath, into the room, and no more of it touches the fide
of the window than the part bc.

When it rains, efpecially in flying fhowers, this inftru-
ment, handing in the fituation above defcribed, is fre-
quently electrified ; and by the diverging of the electrome-
ter the quantity and quality of the electricity of the rain
may be obferved, without any danger of miftake. With
this inftrument I have obferved that the rain is generally
electrified negatively, and fometimes lo ftrongly, that I
have been able to charge a fmall coated phial at the
wire ag.

This rain-electrometer fliould be fixed in fuch a man-
ner that it may be eafily taken from and replaced at the
window as occafion may require ; for it will be neceflary
to clean it very often,, particularly when a fhower of rain
is approaching..

2X.PE.RT--

fame Electrical Experiments .

5,3-

EXPERIMENTS MADE WITH A GLASS TUBE HERMETI-
CALLY SEALED, AND HAVING SOME QUICKSILVER

INCLOSED IN ITS CAVITY.

I N making fome experiments rather foreign to elec-
tricity, it occurred to me, that when I agitated fome
quickiilver in a glafs tube hermetically fealed, and in
which the air was very much rarefied, it contracted a
very fenfible quantity of electricity ; which however was
not conftant, nor, as I firft thought, in proportion to the
agitation of the quickiilver. Being defirous of afcertain-
ing the properties of this tube, I conftrudted feveral of
them, and, as accurately as I could, obferved their pro-
perties ; but as they all agreed with regard to the chief
points, I lhall only defcribe one, which is the bed: I have
yet made.

This tube is two feet and feven inches long, and about
four tenths of an inch in diameter: the quickiilver in
it may be about three quarters of an ounce, and to ex-
haull it of air, I clofed it whilft the quickiilver was boil-
ing in its oppolite end.

Before I ufe this inllrument I warm it a little and
clean it; then holding it nearly horizontally, I let the
quickiilver in it run from one end of the tube to the-

other*

54 M-. cavallo’s Account of

other, by gently and alternately elevating and deprefling
its extremities. This operation immediately renders the
cutfide of the tube electrical, but with the following re-
markable property, viz. that part or end of the tube
where the quickfilver actually Hands is pofitive, and the
remaining part negative. If* by elevating this poiitive
end of the tube a little, I let the quickfilver run to the
oppofite end which was negative, then the former in-
flantly becomes negative and the latter pofitive. The
pofitive end is always more ltrongly eleCtrical than the
negative. If when one end of the tube (which we call a)
is pofitive, that is, if, when the quickfilver is in it, I do
not take off the eleCtricity ; then on elevating it lb as to
let the quickfilver run to the oppofite end b, the end a
becomes negatively electrified in a very fmall degree:
if I make it pofitive a fecond time, and do not take off
that pofitive eleCtricity; then, on elevating it again, it
appears to be pofitive in a fmall degree : but if whillt it
is pofitive I take off that pofitive eleCtricity, then on being
elevated it appears ltrongly negative.

Thefe appearances I would explain in the following
manner: the quickfilver agitated within the cavity of the
tube aCts like a rubber, that is, excites the infide furface
of the tube pofitively, and becomes itfelf negative. Now
when the quickfilver, negatively electrified, is on one

end

i

feme EleBrical Experiments. 55

end of the tube, the outfide of the glafs, by the known
property of charged electrics, muft be pofitive. The re-
maining part of the tube being pofitive on its inner fur-
face, muft be negative on the outfide. But as there is a
vacuum within the tube, it may be afked, why is not the
equilibrium between the negative electricity of the quick- -
iilver and the pofitive electricity of the glafs inftantly
balanced?

When about two inches of each extremity of this tube
are coated with tin-foil, that coating aflifts to make the
electricities more confpicuous.

With regard to the conftruCtion of fuch tubes (which I
have made of feveral lengths from nine inches to two
feet feven inches) I find that fome will aCt very well,
while others will hardly acquire any electricity at all,
even when they are made very hot. I am not as yet tho-
roughly fatisfied with refpeCt to the caufe of this difference,
but fufpeCt that the thicknefs of the glafs is more con-
eerned in it than any thing elfe ; for I find that a tube
whofe glafs is about one twentieth of an inch thick,
anfwers better than either a thicker or a thinner one.

November 13, 1776.

56

Abbe dig que mare’s Third EJJdy

VII. A Third Ejfay on Sea-anemonies.
By the Abbe Dicquemare.

ON THE GENERATION OF THE FOURTH SPECIES.

Read Jan. 9, TT AVING in my fecond eflay on fea-
1777* r“j

•* anemonies, communicated my difeo-
veries on the manner in which the fourth fpecies is mul-
tiplied, and offered fome conjectures on the internal or-
ganization of the fmall fhreds which become anemonies,
I added a caution, not to admit of thofe conjectures with-
out circumfpeCtion. What pafled under my own eyes

convinced

Troijietne Memoir e pour fervir a l' Hiftoire des Anemones de Mer.
Par M. V Abbe Dicquemare.

Sur la Generation de la Quatrieme Efpece.

Havre de Grace, Mars 7, 1776.

A Pres avoir expofe dans un fecond memoire pour fervir a Phiftoire des Ane-
mones de mer, mes decouvertes fur la maniere dont celles de la quatrieme
cfpece fe multiplient; apres avoir ouvert quelques conjectures fur l’organifation
interieure des petits lambeaux qui deviennent anemones, je ne diffimulai pas
qu’on ne devoit point y reftraindre fes idees. Ce qui fe paffoit fous mes yeux

ir*.

on Sea-anemonies.

57

convinced me more and more (and I gave fome hints to
that purpofe) that the fmalleft particle of a living ani-
mal, has an organization which far exceeds every idea
we can conceive of it ; and which, from the extreme mi-
nutenefs of thofe particles, baffles our clofeft infpeCtion :
fo that inftead of being furprized at the lingular effedts
of reproduction, they are rather what we ought to ex-
pe£f, and be prepared to obferve as they arife. I': is with
this view that I have continued my experiments and ob-
fervations: they have confirmed the difcoveries I had
made, and afforded me an opportunity to juftify fome
eminent men, whole affertions concerning the multipli-
cation of the frefh-water polypi by fe&ions, have met
with the rrloft unmerited contradictions.

Among all the objects which nature offers to the con-
templative mind, there is none fo ftriking and important
as that of the generation of beings, and efpecially of ani-
mated

me perfuadoit de plus en plus, et je m’en expliquai, que les moindres parties d’un
etre vivant ont une organifation qui furpaffe infiniment l’idee que nous pouvons
nous en faire, que l’enorme petitefTe de ces parties derobe aux regards les plus
avides ; et que loin de fe furprendre des effets iinguliers de reproduction, on
devroit pour ainfi dire les attendre, et fe mettre a portee de les faifir. C’eft dans
cette viie que j’ai continue mes obfervations et mes experiences : elks ont con-
firme les decouvertes que j’avois faites, et me procurent la fatisfaCtion de jufxifier
les hommes illukres, qui en nous faifant connoitre la multiplication des polypes
d’eau douce par la fe&ion, ont eprouve les contradictions les moins meritees.

De tous les objets que la nature offre a l’efprit meditatif, il n’en eft point c!c
plus grand, de plus refpeCtable, que celui de la generation des etres, et furtout dr 5
Vol. LXVII. I " etres

58 Abbe dicquem are’s 'Third EJfay

mated beings. This grand myftery has always attracted
the attention of the greateft philofophers ; but their want
of fuccefs in their refearches may be eafily inferred from
the deficiency of proper means of obfervation: and it
feems an advantage referved for our age, to introduce a
new fet of beings, which bids fair to throw great light
upon our enquiries on that fubjedt.

Had I only frefh proofs to add to thofe already given,
and no new difcoveries to commmunicate, I fhould cer-
tainly leave nature to eftablifh our opinion of her opera-
tions : but having been fortunate enough to gather fome
fcattered fruits in this wide field, which had efcaped the
obfervation of others merely becaufe they were engaged
in more plentiful harvefts, 1 have been ftruck with the
increafing Angularity, number, and importance of the
objedts, which have appeared to me to diffipate all doubt.

I 111 all

etres vivans : c’eft aufii vers cette merveille que les philofophes les plus diftin-
gues ont dirige leurs regards ; mais leur manque de fucces refulte naturelle-
ment des foibles moyens qu’ils avoient pour faire des obfervations; et c’eft
un avantage qui paroit avoir ete referve a notre fiecle, de faire paroitre fur la
fcene des etres jufqu’ici ignores, qui promettent de nous fournir des nouvelles
lumieres fur ce fujet.

Si je n’avois a prefenter ici que les memes decouvertes, quoique ce fut multi-
plier les preuves, je laifferois a la nature le foin de fixer 1’opinion ; mais dans ce
champ fertile j’ai ete aifez heureux pour recueillir quelques fruits a l’ecart, et
^qui n’avoient echappe aux regards des autres que parcequ’ils etoient occupes de
recoltes plus abondantes : j’ai vu la fingularite s’augmenter, et le nombre comme
I’etendue des objets m’a paru propre a difliper les doutes, Je ne rappellerai pas ici

ce

on Sea-anemon'tes.

59

I fhall not here repeat what I have already faid concern-
ing the reproduction of the fuperior part of the fourth
fpecies, which is often as thick as- one’s arm; new experi-
ments have confirmed it, and have fhewn the poffibility
of the reproduction of frefh- water polypi, without hav-
ing recourfe to a multitude of imperceptible animals :
but the better to explain what I have fince difcovered
concerning the generation of this fpecies of anemo-
nies, I muft beg leave briefly to recapitulate what I have
already publifhed on that fubjeCt. Thefe anemonies,
having their bafes unequally extended upon, and firmly
adhering at their extremities to a hard fubftance, contrail,
and thus tear off and leave on that hard fubftance, one or
more fmall fhreds of their bafes, covered with" pieces of
the coat of the old animals ; and thefe fhreds foon after
become fmall anemonies, which alfo is the cafe in artificial
feCtions. Of this Angular operation I have had opportu-
nities

ce que j'ai dit de la reprodu&ion de lapartie fuperieure des anemones de la qua-
trieme efpece, fouvent groffie comme le bras; de nouvelles experiences Font encore
confirmee, et ont fait voir la poffibilite de celle des polypes d’eau douce, fans avoir
befoin de recourir a une multitude d’animaux imperceptibles : mais qu’il me foit
permis de retracer ici en peu de mots ce que j’ai deja publie fur la generation de
cette efpece, autrement il feroit difficile de faifir ce que j’ai apper^u depuis. Ces
anemones, ayant la bafe inegalement etendiie et fortement attacliee par quelques
points de fes extremites fur un corps dur, fe retirent fur elles memes, et laiffent
ainfi en fe dechirant une ou plulieurs portions tres petites de leur bafe, recouvertes
d’une parcelle de leur robe, qui deviennent en peu de temps des petites anemones,
ce qui a lieu aulli par des fe&ions violences* En obfervant de nouveau ces

I 2, animaux

Go Abbe me que mare’s 'Third EJJay

nities of feeing repeated inftances, having been very afli-

duous and conftant in my obfervations.

On the 2 6th of October 1 7 7 5 , an anemony, on which
I had tried an experiment foreign to the prefent purpofe,
contracted, and left on the fide of the vale a fmall Hired,
which at the very firft I fufpeCted to be intended for a
young anemony : not that it was either flefiiy, or that it
feemed to contain a bulb ; but becaufe the anemony had
for feveral days before ffcretched itfelf confiderably, and
in a particular manner, from that point of the bafe. Cer-
tain internal fibres or radii appeared, which in the old
anemony had their direction from the circumference to
the centre: and as the Aired was an irregular fegment of
the area of the circle formed by the bafe of the old ane-
mony, it is evident that thefe fibres or radii, being fome-
what diftant from each other at the arch of the fegment,

did

animaux, et apres avoir attendu longtemps, j’ai eu la fatisfa&ion de voir fe repeter
cette operation finguliere, et je l’ai fuivie d’auffipres qu’il m’a ete polfible.

Le 26 Odlobre, 1775, une anemone fur laquelle j’avois tente une experience
quin’arien de commun avec notre objet prefent, laiffa contre les parois du vale,
en fe retirant, un petit lambeau que je foup^onnai des le commencement etre
deftine a devenir une petite anemone ; non qu’il fut epais ou qu’il me-parut contenir
quelque bulbe, mais parceque l’anemone s’etoit fort alongee par ce point de fa
bafe, depuis pi ulieurs jours, d’une maniere toute particuliere. On appercevoit dans
i’interieur certains fibres ou rayons qui dans l’anemone avoient tendu de la dr-
conference au centre, et comme ce lambeau etoit un feoment irregulier de l’aire
du cercle que forme la bafe d’une grande anemone, on comprend que ces fibres
ou rayons, un peu diflans Fun de l’autre a l’arc de ce fegment, ne convergoient

pas

on Sea-anemonies . 61

did not converge fufficiently to form a centre at the
chord ; and that the point of union of thefe radii was the
centre of a circle equal to that formed by the bafe of the
old anemony (fee tab, hi. fig. i . its natural fize, and fig.
2. magnified). During the firflc days this little fragment
acquired plumpnefs, bent itfelf gradually into a round
figure, and feemed to make fome efforts towards forming
itfelf into the fhape in which it appeared on the 25th;
the fibres becoming gradually more convergent, the chord
of the arch fhorter, and the arch a fegment of a fmaller
circle. At length the radii united in a centre (fee fig. 3.
magnified) and its profile appeared a fegment of a fphere
(fee fig. 4.)

On the 30th of Odtober I perceived in this fragment con-
fiderable contractions and dilatations in the direction of its
thicknefs ; but could fee no mouth nor limbs. On the ift

of

pas aflez pour former un centre a la corde; et que le point de reunion de ces
rayons etoit le centre d’un cercle egal a celui que formoit la bafe de l’anemone :
voyez tab. hi. fig. 1 . et 2. dans l’une ii eft de grandeur naturelle, etdans l’autre vu
a la loupe. Pendant les premiers jours cette petite portion prenoit de l’epaififeur, fe
recourboit et s’arrondifToit peu a peu; elle tendoit de toute fes forces a prendre la
forme ou elle parvint le 25, c’eft a dire que petit a petit, les fibres etantdevenus
plus convergens, la corde de Parc du cercle plus courte, Parc une portion d’un
plus petit cercle, il s’etoit forme un centre de reunion de ces rayons, qui occupoit
le cote de ce petit corps anime, comme le reprefente la figure 3. qui eft vile a la
loupe; quant au profil, il eft reprefente par un fegment de fphere, ou par la
figure 4.

Le 3oOftobre j’apper^us des contractions et des dilatations tres fenfibles dans
i’epaifleur, mais point de bouche ni de membres. Le 1 Novembre il a change de
2 place.

6 a Abbe dicquemare’s 'third EJJay

of November it moved from its place. On the 7th I dilco-
vered, by means of a ftrorig lens, an orifice and fome ap-
pearance of limbs. On the 1 6thlfa\v them very diftin&ly.
On the 17 th it changed its place again. At the beginning
of January 1 77 6, the folds of the body were formed, and
then it could not but be confidered as a young anemony,
fimilar in every refpeft to the old one by which it had
been produced, except in the number of limbs, which
however, although the animal be flill very fmall, are
now increafing. The femi-tranfparency, which often
prevents accurate obfervation, allowed me to view the
gradation through which the fmall fibres became con-
vergent: I could alfo fee the gradual contraction of the
angles of the fegment, and that not a fingle particle of
the fragment perifhed ; all feemed to be re-incorporated
into the mafs. The word all muft not, however, be
taken in a ftrict fenfe; for I muft confefs that I per-
ceived fome yellowifh filmy matter round this little

mafs,

place. Le 7, a l’aide d’une forte loupe, j’ai appergu un orifice, etdes apparenccs de
membres. Le 16 je lesai vus tres diftin&ement. Le 17 il a de nouveau change
delieu. Au commencement de Janvier 1776, le pli du corps s’eft forme; c’etoit
done alors une petite anemone qui, a l’exception du nombredes membres, reflem-
bloit parfaitement a celle dont elle etoit proveniie; les membres augmentent, et
cependant cette anemone eft fort petite. La demi-tranfparence, qui gene quel-
quefois dans les obfervations, m’a permis de diftinguer le progres par lequel les
petites fibres font deveniies convergentes : J’ai vu aufli les angles de fegment fe
racourcir, et rien ne m’a paru perir : tout s’eft refoule dans la made. Ce mot tout
ne doit cependant pas etre pris a lalettre: j’ai apper^u quelques pellicules quelques,

fubftances

on Sea-anenionies. 63

mafs, which feparated from it; but its quantity was fo
fmall, that I could not thence infer the lofs of any par-
ticle of the fhred, and rather imagined that this matter
was merely the effect of forne fecretions or extravafated
humour-

What ft ill leaves me a doubt concerning the germ is*,
that this effect has been more confiderable in fome of my
experiments than in others. Had the fragment of the
anemony contained a germ, it might be concluded that
the membrane which covered it fhould have perilhed as
foon as the animal was formed ; this however was not
fufficiently evident in feveral cafes, and efpecially in thofe
where the fragment had been naturally torn off. At firft
the fhred was thin, and thinner ft ill before it was fepa-
rated from the old anemony ; and no bulb could ever be
perceived either then or in the fequel. I was then led to

imagine.

fubltances un peu jaunatres, autour de la petite maiTe, qui en ont ete feparees 5
mais elles etoient en li petite quantite, que je n’ai pu en conclure qu’il eut peri-
quelque chofe du lambeau, cette fubftance etoit peut- etre due a des fecretions on
a quelque humeur extravafee.

Ce qui me laiffe encore un doute reel, c’efl: que cet efFet a ete plus fenlible dans
quelques unes de mes experiences. Si cette portion d’anemone eut contenu un
germe, n’eft-on pas porte a penfer que les membranes qui Penvelopent auroient
peri lors de fon developement. C’ell ce qu'on ne remarque pas d’une maniere
alfez fenlible dans plulieurs, et furtout dans ceux qui fe dechirent naturellement.
D’abord le petit lambeau etoit mince et, avant qu’il fut fepare de Panemone, je Pai.
c>bferve pendant plulieurs jours ; il etoit plus mince encore : je n’y voyois nulle-

apparence

64 Abbe dicquem are’s Third Effay

imagine, efpecially on account of the union of the fibres
in a common centre, that a fimple fhred produced an ane-
mony. But from what caufe does this little fragment
contrail into a circle, and increafe its thicknefs? how
111 all we account for its vifible tendency towards forming
a new animal? is it a neceflary inftinit ? can it be ad-
mitted that in thefe animals the vital principle is pecu-
liar to every particle? and in what manner is it, or is it
not, fubordinate to the general organization of the indi-
vidual, according to circumftances which it feems in our
power to modify ? How many fpecious reafonings might
he made on this fubjeft, did we prefer the admiration of
the public to real truth ! The only inference that I think
can as yet be derived from thefe and the following obfer-
vations is, that there certainly are animated beings which
multiply, as it were, by flips; but whether the con-
currence

apparence de bulbe, et je n’y en ai point vu depuis : j’ai done ete tente decroire,
furtout a caufe de la reunion du bout des fibres a un centre commun, que c’etoit
an fimple lambeau qui devenoit anemone. Mais qui eft ce qui fait, qu’etant
detachee, cette petite portion fe recourbe, et prend de 1’epailTeur ? par quelle caufe
tend-elle vifiblement a former un animal? fent-elle alors la neceffite de le
devenir ? le principe de la vie feroit-il, dans ces animaux, particulier a chacune
de leurs parties ; et comment eft il, ou n’eft il pas, felon les circonftances que
nous pouvons faire naitre, fubordonne a Torganifation generate de l’individu ?
Oh, fi on etoit tente de preferer l’admiration du public a la bonne foi, que de
chofes a dire ! Tout ce qui me fembie qu’on peut conclure de ces obfervations, et
plus encore de celles qui vont fuivre, c’efl qu’il ell vrayment des etres animes
qui fe multiplient comme de bouture ; mais j’attends etre inflruit par des

nouvelles

on Sea-anemonies. 6 5

currence of two fexes may or may not be difpenfed with,
is a fact I expedt to learn from future experiments. I
can at prefent only fufpedt its being unneceffary, fincefhe
anemonies I had hitherto operated upon were all pro-
duced at fea. The manner in w'hich they multiply feems
ftrongly to favour that fuppolition : fuch ideas begin al-
ready to become familiar to us, they appear lefs lingu-
lar; and yet how different are they from thofe we ufed
to entertain of the animal creation !

Let us now proceed from the operations of mere na-
ture, to fuch as are in fome meafure the effect of art. On
the 1 ath of December 1775, I fevered with the point
of a knife ten fmall pieces from the bafes of feveral ane-
monies, at the places where they feemed the moft dif-
tended, and moft adherent to large oyfter-fhells, from
which they dropped after the operation. I put thefe

pieces

nouvelles experiences, fur l’inutilite du concours des deux fexes : je ne puis que la
foupqonner, parceque les anemones que j’ai op ere jufqu’ici etoient nees en mer.
La maniere dontces animaux fe multiplient fetnble etayer fortement ce foup^on.
Deja nous nous accoutumous a toutes ces idees nouvelles; elles nous frapent mains:
cependant combien font elles eioignees de cel les que nous avions de Panimal !

Fallons maintenant dts operations propres de la nature, a celles ou Part entre
pour que [que chofe. Le 12 Decern bre 1775, je coupai, avec le bout d’un
biilouri, dix petites portions des bords de la bafe de plulieurs anemones,, aux
endroils ou ces bafes etoient plus etendiies, et plus adhf rentes a des ecailies de
groffes huitres, dont elles fe detachoient en les coup ant. Je mis ces particules
" Vo l. LX VII. K dans

66 Abbe dicquem are’s Third EJfay

pieces into different vafes. The next day two of them
fluck to the bottom; on the 14th two more adhered;
on the 2 2d, fix of them; on the 24th, nine; and on the
27th, all were affixed. Each of them went through the
fame progrefs as the pieces which had been torn off na-
turally ; and before the beginning of March they were
all furnifhed with limbs 8cc. Although I be confcious
of having been very accurate and attentive in my obfer-
vations, flill I have not yet been fortunate enough to fee
all that I could wiffi. I ffiall however repeat my at-,
tempts, and I have great expectations from the new ex-
periments I meditate. The prefent have pointed out
fome differences which lead to feveral reflections. Thofe
flireds which had been cut of a larger fize, produced (be-
fides the films they may have loft)largeranemonies. Whe-
ther this multiplication be the effeCt of a bulb, of a germ,

or

dans autant de vafes: le lendemain deux etoient attachees au fond; le 14 deux
autres- etoient de'meme attachees;- le 22 ii'x, le 24 neuf, et le 27 elles l’etoient
routes. Chacune d’elles- m’ayant prsfente fucceffivement les memes progrts qu’a-
voientfait les portions detachees naturellement, il feroit inutile de les decrire de
nouveau: avant le premier Mars elles avoient toutes des membres, &c. Quoique
j’aye obferve avec le plus grand foin ce qui sreft pafle, je n’ai pas encore ete
afiez heureux pour voir tout ce que je defirois; mais j’y reviendrai et j’efpere
beaucoup des nouvelles tentatives que je medite. Celles-ci m’ont offert des
differences qui donnent lieu a quelques reflexions. Ceux de ces petits morceaux
ifanemones que j’ai coupes plus grands* ont produit (independamment de ce qui a.
pu s’en detacher) des anemones plus grandes. Si e’eft en vertu d’une bulbe, d*un

germe?

on Sea-anemonies. 67

or of an egg, it ftill appears that its teguments, and all
that is contiguous to thofe teguments, fliould not be a con-
ftituent part of the animal, and that only a larger germ,
can produce a larger animal.

Is it then in our option to produce anemonies not only
when we pleafe, but alfo of what fize we pleafe'w ? Or
does the multiplying anemony follow in this its own in-
clination? All this, added to the junction of the fibres,
feems very oppofite to the opinion of the germs or eggs ;
but on the other hand there are obfervations which fa-

( a ) Without invalidating what is here faid, fome experiments have induced
me to think that this affertion fliould be admitted with Tome limitations;
that if the fhreds be very large, they will perifh; that in general only
fm all ones fliould be cut, without either fretting or tearing them; aad that the
vafes fliould always be kept very clean, and the water as clear and as frefli as
poflible.

vour

germe,ou d’un oeuf quelconque, que cette multiplication fe fait, il femble que tout
ce qui y feroit joint corame envelope, et plus encore comme contigu aux enve-
lopes, devroit ne pas faire partie du petit animal, et qu’il n’y auroit qu’un germe
plus gros, qui donnat une anemone plus groflfe.

Sommes nous done les maitres, non feulement de faire naitre les anemones
quand nous voulon?, mais nieme de leur donner plus ou moins de groffeur (a) ?
L’anemone qui multiplie en dilpofe-t-elle auffi a fon gre ? 1 out cela joint a la
reunion des fibres, femble bien oppofe aux germes et aux oeufs; mais auffi d’autres
obfervations leur font favorables. II m’a femble qu’il fe fe'paroit un peu plus de

(a ) Sans affoiblir de que j’expofe, quelques experiences me font penfer que ceci a des borries
afiez etroites; que des morceaux trop grands periffent, et qu’en general il n’en faut couperque
de petits, fans les tirailler ; que les vafes doivent etre nets, et l’eau claire et fi’aiche.

K 2

ces

68 -Abbe dicquemare’s 'Third EJfay

vour it; It appedred to me, that more of the membrana-
ceous particles came off from the flireds which had been
clipped of a larger fize, than from thofe which had been
naturally torn from the anemony ; but as I have not had
occafion to obferve many of the latter, this difference
may be owing merely to the different fizes of the fhreds.

Another circumftance I obferved in the pieces that
were naturally torn off is, that there are fomc which
produce feveral anemonies, which fometimes remain
^united, and at other times feparate. I have myfelf fre-
quently feen this operation. One of the flireds I had clip-
ped was of an irregular fliape, nearly as in fig. 5. A little
contraction was foon formed between the two extremities,
both of which became round, fwelled and affumed the ap-
pearance of two drops of tallow ; the contra&ion became

like

ces efpeces de pellicules des morceaux coupes un peu gros, que de ceux arrache's
naturellement par l’anemone meme ; mais comme je n’ai eu occafion d’obferver
qu’un petit nombre de ceux-ci, il pourroit arriver que cette difference ne feroit
diiequ’au plus oumoins d’etendiie du lambeau.

Une autre remarque que j’avois deja faite dans les morceaux fepares natu-
rellement eft, qu’il s’en trouve quelques uns d’ou naiffent plufieurs anemones,
entre les quelles il y en a qui reftent unies, tandis que d’autres fe fe'parent. Cette
operation, s’eft repetee fous mes yeux. Un lambeau que j’avois coupe avoit a peu
pres la forme que reprefente la figure 5, 11 fe forma un petit etranglement

sntre l’un et l’autre de fes bouts; chaque boutprit une figure ronde, et leur fur-
face fupericure s’elevoit en goute de fuif : 1’etranglement devint comme un

on Sea-anemcnies* 69

like a thread (fig, 6.), On the 24th of January, the
larged: piece (for they were of very unequal fizes) crept
up a little way on the fide of the vafe; and on the 28th,
the thread broke, when the two fragments became two
diftinct anemonies. Doth this imply that there were two
germs in the Hired: Or may one Angle Hired, without
any bulb, germ, or egg whatever, produce one or more
anemonies either connected or feparate ? Thefe are ques-
tions I am not yet able to folve, and I with I were the only
one thus uninformed. But to return ; the following fadts,
of which I have, frequently been, eye-witnefs, mufi now
be admitted. 1 ft, That the anemonies of this fpecies
are multiplied by flireds, both naturally and artificially.
2dly, That thefe flireds produce fometimes only one, and
at other times feveral anemonies. 3dly, That among
thefe young anemonies formed by one Hired, feveral re-

main

filet, figure 6; Le 24 Janvier, la plus groffepartie (car elles etoient fort inegales) .
monta un peu aux parois du vafe; le 28 le filet s’e ft rompu, et ces deux parties
font deveniies deux petites anemones. Y auroit il done eudeux germesdansce mor-
ceau ? ou bien peut-il d’un fimple lambeau fans bulbe, fans germe, fans oeuf
quelconque, naitre une ou pluGeurs anemones, unies ou feparees ? C’eft ce que je
ne f^ais pas encore, etje voudrois etre le feulqui fignorat. Revenons done a cette _•
fource feconde. D’abord on doit regarder comme des faits certains, dontj’ai ete
temoin plufieurs fois, i°, que les anemones de cette efpece fe multiplient
naturellement et artificiellement par des lambeaux ; 2°, que ces lambeaux

deviennent fouvent une, quelquefois plufieurs anemones ; 30, que de. ces

petites anemones, formees d’un meme lambeau, plufieurs reftent unies entre elles

q-uoique

7© Abbe dicquemark's Third EJJay

main connected, but that the greateft number feparate
by contractions. 4-thly, That among thofe which remain
connected there are fome which grow to the largeft fize,
fuch as the monftrous anemony mentioned in my fecond
effay, in which three individuals had been blended toge-
ther; and another of a fmaller lize in the fiiape of a Y(l*t
reprefented in the plate of the fame elfay, which before
my own eyes produced a young anemony, by tearing a
fmall fhrecl from the bafe of its coat.

What do we then perceive in thefe flireds? Nothing
hitherto but a membrane which was before part of the
bafe of the great anemony, a mere Ikin which was part of

(b) This fpecies, which is fo fertile in monftruohties, has alio prefented ine
with one which had two bodies on one bafe. Of the firft fpecies I have as yet
feen but one monfter, which on the contrary had two bafes and only one body.
I faw it at its birth.

its

quoique le plus grand nombre ie fepare par etranglement; 40, que parmi cedes
qui reftent unies, il y en a qui deviennentde la plus belle groffeur, com me l’ane-
mone monftrueufe dout j’ai parle dans inon fecond memoire, dans laquelle trois
individus etoient confondus, et une autre moins groffeen forme d’Y (b), repre^
fentee dans la p’anche du merae memoire, qui produifit devant moi une petite
anemone en dichirant un lambeau du bord de fa bafe.

Qu’appenpit-on done dans l’un de ces lambeaux ? Tufqu’ici je n’y ai vu qu’une
membrane qui faifoit auparavant partie de la bafe de la grande anemone, une

'(b) Cette efpece feconde en monftruofite m’en a encore offert une qui a deux corps fur une
merae bafe. Je n’ai jamais eu qu’un monftre de la premiere efpece, il avoit au contraire deux
bafes et un feul corps. Je l’avois vu naitre.

5

peau,

vn Sea-anemonies.

7i

its coat; fome mufcular fibres and fmall internal fila-
ments defcribed in my fecond eflay, as they appeared in
the folar microfcope; and a clammy fubftance filling up
the interfaces. When fuch a flared is decompofed, it
changes into a whitifh glutinous lubftance, which,
through a microfcope, appears a mafs of minute globu-
lar bodies, that feem ftill to be of a compound texture,,
and fome of which are of a larger fize, and of an oblong-
oval fhape (fig. 7.) as they may be often obferved in
fea-water viewed through a microfcope. The circular
edge of thefe fhreds which formed part of that of. the
old anemony, retains the faculty of adhering and loofen-
ing itfelf; nor do any of the fibres perifh in the forma-
tion of the new animal ; they only receive a new arrange-
ment, or acquire a greater convergency.. What caufe

can-.

peau portion de fa robe, cles fibres mufculaires, des petits cordons dans I’inte-
rieur dont j’ai parld dans mon fecond memoire apres-les avoir examines an micro
{cope folaire, etenfin une matieregelatineufe qui remplit les intervalles. Lorfque
ces lambeaux fe decompofent, il en refulte une matiere blanchatre, legerement
vilqueufe, 1 quelle, vue.au microfcope, ofFre des efpeces de corps globuleux, tres
petits, qui paroiffent compofes, , et parmi lefquels on remarque une grande quan-
tite d’animaux plus grands, d’un ovale fort allonge, comme le reprefente la figure
7, et comme on en voit fouvent dans l’eau de la mer examinee au microfcope,
Le bord en portion de cercle de c:s lambeaux, qui formoit celui de la grande ane-
mone, conferve la faculte de s’attacher et de fe detacher; et dans la formation du<
petit animal les fibres ne fe detruifent point, ils ne font que prendre comme l’on %
Toit un nouvel arrangement, ou plus de convergence. Quelle peut done etre •

72 Abbe dicquemare’s 'Third EJJ'ay

can we then affign to the tendency thefe fibres and thcle
lhreds have to form a new animal ? It can eafily be con-
ceived that the exterior border of the Hired, preferving
the faculty of adhering, may form a fegment of a fmaller
circle; but it might equally incline to form a fegment of
a larger one, did it not feem more natural that a body en-
dowed with fenfation, fhoukl rather endeavour to clofe a
wound, than to open and rend it more and more. There
muft then be in this Hired a ceitain degree of fenfation,
fince in order to fix, and to loofen itfelf, occafionally, it
muft have a perception of its adherent or detached ftate.
But there is even more than this in the Hired we are ex-
amining; for allowing that the border afliimes a circular
fiiape, and thereby caufes a convergency of the fibres,
that the angles contradt, and the wound clofes, the refult
of which is a fmall animated body; yet it will always be

difficult

la caufe par laquelle ces fibres, et le lambeau entier, tendent a former, et femblent
former en effiet une petite anemone ? On conceit aifement que le bord exterieur
du lambeau, confervant la faculte de s’attaclier, peut former une portion d’un plus
petit cercle; mais aufii il pourroit en former une d’un grand, fi ce n’eft qu’il paroit
plus naturel pour un corps jdoiie de la faculte de fentir, de tendre a reformer
une playe, que de i’ouvrir, ou de la tirailler de plus en plus. II y a done dans ce
petit lambeau une forte de fenfation, puifque pour s’attacher et fe detacher au
befoin, il femble qu’on doit fentir qu’on s’attache ou qu’on fe detache. II y a
plus que cela dans ce lambeau que nous obfervons, car quand le bord s’arrondi-
roit, que par la les fibres prendroient de la convergence, que les angles fe rap-
procheroient, que la playe fe confolideroit, qu’en refulterbit-il r un petit corps

anime ?

on Sea-anemonies.

lb

difficult to conceive how this fmall Hired preferves all
thefe faculties, how this animated being acquires the
power of loco-motion, and whence proceeds the whole
reproduction of an animal. Where lhall we find the
principles of the limbs, of the inteftines, of the mouth,
of the fold in the body, of the elegant tufts which ter-
minate the limbs, &c. fince nothing of all this can be
obferved in fuch a fragment? Shall we feek for that
principle in the fiender threads, the conft rudtion of which,
feen with the folar microfcope, had ftruck me with admi-
ration ? but my obfervations have not convinced me that
they were intended for thefe purpofes. What would
have determined my opinion in favour of thefe filaments
is, the facility with which they wrap themfelves up in a
fpiral, and form certain parcels (which have the ap-
pearance

anime ? mais outre qu’il fera toujours difficile de concevoir comment ce petit
lambeau conferve ces facultes, et comment ce corps anime acquiert celle dc
changer de lieu au befoin, on peut encore demander d’ou procedera le develope-
ment qui fuit ? ou fe trouvera le principe des membres, des inteflins, de la
bouche, du pli du corps ? d’ou naiffent ces beaux panaches qui terminent les
membres, &c. puifque rien de tout cela ne fe remarque dans cette partie?
Chercherons nous ce principe dans les cordons delies dont la ftrudlure, au mi-
crofcope folaire, nous a paru ii admirable? mais je n’ai pu trouver dans i’obfer-
vation de quoi me convaincre qu’ils foient de (lines a cet ufage. Ce qui eut ete
bien plus capable de me fixer fur ces cordons, c’efl la facilite qu’ils ont de fe
rouler en fpirale, et de former des efpeces de paquets qu’on appercoit comme un
Vol. LXYIL L ' petit

74 -Abbe dicquemare’s Third Ejjay

pearance of fmall whitifh bodies) near the border, be-
tween the ikin and the bafe of the young anemonies,.
when they extend the latter. I might have been parti-
cularly influenced by the number of floating tranfparent
globules, which, by means of the microfcope, I have
often feen among thofe filaments, and which appeared
nearly of the fame texture : but it muft be here obferved
that the illufions of the microfcope are often very great,
on account of the fpherical form and tranfparency of
thofe globules, which at firft fight appear to have a large
hole diametrically through them. The globules which,
by means of the microfcope, are often feen in lea-water,
evidently contain a liquid; and here all my knowledge
ends. Does the principle we are in fearch of exift in
this gelatinous fubftance, concerning wliofe texture we

are

petit corps blanchatre vers Ies bords, entrelapeau et la bafe des jeunes anemones,
lors qu’elles l’etendent. J’aurois pu encore etre arrete d’une maniere plus par-
tial] iere a l’afpedt de certains globules flotans et tranfparens, que j’ai fouvent
trouves au microfcope parmi ces cordons, et qui me paroiftent compofes a peu
pres de meme, Mutant que les illuiions microfcopiques permettent cPen juger ; car
ces illuiions font fort grandes a caufe de la fphericite et de la tranfparence de ces
globules, qui au premier coup d’oeuil femblent perces diametralement d’un gros
trou ; et le microfcope folaire ne m’a pas mieux fervi que les autres a ce fujet. Ces
globules, qui d’ailleurs fe rencontrent fouvent dans l’eau de la mer viie au mi-
crofcope, font fans doute' remplis d’une liqueur ; et voila ou fe tsrminent toutes
nies coanoilTances, Sera-ce dans la fubftance gelatineufe, dont la texture ne nous

eft

on Sea-anemonies .

7.5

are as yet perfectly in the dark? If ever we difcover this
texture, it will probably lead us back to a more diftant
mechanifm, and this to another of a ff ill more delicate
order: this laid perceptible caufe, will probably conduit
us to the general order, that is to nature; and nature to
its Author. But how fatisfaitory, how ufeful may it not
prove to unravel by degrees (although perhaps with
feme uncertainty) even the coarfeft mechanifm by
which nature operates? Shall we fuppofe that the ge-
latinous matter is nothing but an irregular, inco-
herent fubftance ? At firft fight the fame might he faid
of the white fubftance of the brain, although it feem

to have more confiftency; yet in many places it ap-
pears fibrous, and if we could trace it through the

nerves, we fhould no doubt difcover a moft admirable or-
ganization. The operations of nature in eggs, chryfa-

lids.

eft point conniie, qu’exiftera le principe que nous clierchons? Si nous la con-
noiffons un jour, elle pourra bien nous renvoyera un mechanifme plus eloigne ;
celui-ci a un d’un ordre plus delicat; etenfin la derniere caufe apper^ue, a l’ordre
general, e’eft a dire a la nature; et la nature a fon auteur. Mais combien
n’eft il pas fatisfaifant, combien ne peut il pas etre utile, de developer peu
a peu, quoiqu’avec quelque incertitude, le mechanilme meme le plus grofiier
par lequel la nature opere? Cette matiere gelatineufe ne feroit elle qu’un
corps informe fans texture ? a la premiere vue nous en dirions bien autant
de la fubftance blanche du cerveau, quoique plus compare ; cependant en
plufteurs endroits elle paroit fibreufe, et ft nous pouvions y fuivre les nerfs,
nous decouvririons fans doute une organifation admirable. Ce qui fe pafTe

L 2 dan$

76 Abbe dicque mare’s T'bird EJfay

lids, nymphs, and a great number of marine bodies, feem
to juftify the opinion that there is, in certain humours, a
kind of organization which is imperceptible to our eyes,
and conceals from us great and important myfteries. All
this mull then be fuppofed to exift in the gelatinous
matter contained in our fmall fragment : and it is this,
perhaps better than the reproduction of parts, that will
point out to us at large, the imperceptible operations of
nature in the formation of the foetus , of eggs, and per-
haps of all that may be called a germ. It is thus that
the different views taken of nature may mutually clear
up each other. I have not the vain prefumption to
think that I fhall be able to make a great progrefs in this
dark career; all I boaft is, that I have dared to enter into
it, I have great expectations from the experiments I

have

dans les oeufs, dans les chryfalides, dans les nimphes et dans une aflez grande
quantite de fubftances qu’on trouve dans la mer, &c. porte a croire qu’ii
y a dans certaines humeurs une forte d’organifation qui nous echappe et
qui couvre de grandes merveilles. II faudra done fuppofer tout cela dans la
matiere gelatineufe de notre petit lambeau : la, plus encore que dans les repro-
ductions de parties, elle pourroit nous offrir en grand, ce qui precede en tres petit
la formation du foetus dans l’oeuf,et peut-etre celle de tout ce qu’on peut appeller
germe. C’eft ainfi que les difterens points de vile fous lefquels on peut conii-
derer les operations de la nature, pourroient s’eclairer mutuellement. Je n’ai pas
la folle prefomption de croire que je ferai affez heureux pour faire beaucoup de
chemin dans cette carriere obfeure, je me fens feulement le courage d’y entrer.

a Je

on Sea-anemonies.

77

have in view; but I fhall be obliged to take up the fub-
je6t far backwards. An accident has juft now deprived
me of my twelve little ane monies : the fea-water was, in
in the firft days of March, fo much troubled by the fall-
ing in of part of the cliff, Sec. that my great anemonies
of the firft and third fpecies have confiderably fuffered,
and all the fmall ones of the fourth fpecies died in one
day. Another accident had juft preceded this, and had
occafionedthelofsof a whole year’s labour: on the 28th of
January, Reaumur’s thermometer fell to 150 below the
freezing point ; I had then forty vafes containing anemo-
nies on which I was making experiments, and was at the
fame time attending to other avocations : notwithftand-
ing all the meafures I had taken to prevent it, the water
froze in feveral of them : my anemonies however would
not have died, lince one of the firft fpecies, which I had

on

Je compte beaucoup far les experiences que je medite, tnais je ferai oblige de
reprendre les cliofes de loin.Un accident vient de me priyer de mes douzepetites
anemones : l’eau de la mer, dans les premiers jours de Mars, a ete tellement trou-
ble par I’eboulement des falaifes, &e. que mes grandes anemones de la premiere
et de la troilieme efpece orrt confxderablement fouffert, et les petites de la
quatrieme font toutes mortes en un meme jour. Un autre accident avoit precede,
et m’avoit fait perdre un an de travail: le 28 Janvier, le thermometre de
REAUMUR defeendit a 150 de condenfation ; j’avois alors quarante vafes d’ane-
mones de mer en experience, et mes foins etoient partages par d’autres objets :
quelque precaution que j’aye pris, i’eau de plulieurs gela ; mes anemones n’en

feroient

7 8 Abbe dic<5Uemare*s ’Third EJfay

on purpofe fuffered to freeze out of the water, did not
perifh; but they fuffered a good deal, and I am deter-
mined to avoid all uncertainty in my experiments.

If we judge of the multiplication of the anemonies of
the fourth fpecies, by the number of young ones that
are feen round the large ones, it muft be very confidera-
ble. This fpecies alfo affords us a Angularity which is
not obfervable in the frefh-water polypi, that of multi-
plying by tearing off, of its own accord, fmall flncds
from its body..

Although the main object of this effay be the genera-
tion of the fourth fpecies, I cannot however omit ob-
ferving that feveral of its individuals, having been cut
into two equal parts perpendicularly to their bafes,
formed each of them two compleat anemonies. And I
beg leave to infert here an obfervation on the firft fpecies,

which

feroient pas mortes, puifqu’une de la premiere efpece, que j’ai fait geler expres
a fee, n’a point peri : mais elles ont beaucoup fouffert, et je ne veux aucun
equivoque clans rn.es experiences.

A en juger par le nombre des petits qu’on trouve autour des grofies anemones
de la quatrieme efpece, leur multiplication eft tres nombreufe : elle ofFre aufii,
comme on vient de voir, une ftngularite que ne nous ont point prefente les
polipes d’eau douce, oell.es de fe multiplier ,en s’arrachant elles memes des petits
lambeaux.

Quoique ce memoire ak pour objet la generation de la quatrieme elpece, je ne
laiflerai pas d’indiquer que plufteurs de fes individus, coupes en deux portions
egales perpendiculairement a leur bafe^ ont forme chacun deux anemones; et

d’inferer

on Sea-onemonies.

79

which will in fome meafure fupply the want of an elfay,
the publication of which is retarded by the abovemen-
tioned accident.

A FURTHER OBSERVATION- ON THE FIRST SPECIES.

TOWARDS the end of the year 1 774, 1 cut in two,
in a perpendicular direction, an anemony of the firft
fpecies, which had been formed from a moiety of one I
had cut before, fo that each half was then only a quarter
of the primitive anemony- Thefe two halves had the
fame fate as the firft fecfions ; and one of them, after
having been thus reftored, and having been always kept
by itfelf, produced, on the 1 ft of J une 1 7 7 5 , a young ane-
mony as perfedt as thofe that are produced at fea, and of
the fame colour as the mother. It mull be remembered

that

d’inferer ici une notice fur la premiere efpece qui fuppleera en partie au memoirs
clout les accidents que je viens de rappoter retarderont la publication.

NOTICE SUR LA PREMIERE ESPECE.

A LA fin de 1774* je coupai par la moitie, dans une direction perpendicu-
laire a fa bafe, une anemone de la premiere efpece, qui apres l’avoir ete, s’etoit
reformee : chaque moiti-e n’etoit done alors que le quart de l’anemone primitive.
Ces deux parties ont fait comme la premiere fois; et une d’elles, apres s’etre ainfi
reformee, et avoir toujours vecu en particular, me donna, le premier Juin 1775,
une petite anemone, auffi parfaite que celles qui naifient a la mer, et de la meme
couleur que la mere. Qir’on j’uge de ma furprife quoique je m’attende a tout j et

8 o Abbe d rcQU e m ar e’s Third EJJay

that in this fpecies, the young ones are entirely formed in
the infide of the animal, whence they are put forth
through the mouth ; fo that, whatever idea we may form
to ourfelves of this fpecies of beings, we can find no real
analogy between any fedfions from them, and thofe torn
from items and roots of certain trees, with a view to mul-
tiply them. The young anemony we are fpeaking of is
not large enough to favour the fuppofition that it had
been ready for birth, in that part of the old anemony,
for more than two years before; fince fome young ane-
monies of this fpecies, which I had kept in order to ob-
ferve their encreafe, have in ten months time grown to
double the diameter of their bafes, without my having
ever taken the trouble to feed them: and it is befides
known, that it is ufual for thefe anemonies, when they

are

ft on me demande, comment ceci, comment cela? je repondrai fans rougir
(puisqu’on peut le faire maintenant) je n’en f^ais rien. On fe reflouvient fans
doute que, dans cette efpece, les petits font entierement formes au plus interieur de
l’animal, d’ou ils naiffent plus ou moins gros par la bouche : alnfl on ne pour-
roit, quelqu’ idee qu’on fe fit de ces animaux, trouver d’analogie reelle entre ces
fe&ions, ct celles qu’on fait aux tiges et aux racines de certaines plantes pour les
multiplier. La petite anemone dont nous parlons n’efl pas affez grofle pour
qu’on puiffe penfer qu’elle ait refte prete a naitre depuis plus de deux ans dans cette
partie de Panemone primitive, puifque des petits de cette efpece, que j’avois pre-
cedemment gardes pour en obferver l’acroiffement, ont augmente du double de leur
diametre en dix mois, fans que je priffe la peine de les nourir; et on f§ait d’ail-

leurs

on Sea-anemonies . $i

are put to any pain, to ejedt all the young ones they
contain.

The reftored moiety produced another young ane-
mony on the yth of Auguft, another on the 27th, one
more on the ift of September, a larger one on the 20th
of October; whereas to this day the other half has not
yet afforded me a Angle young one. Another circum-
fiance worth notice is, that the two halves of the origi-
nal anemony never produced any young ones, neither
during their recovery, nor after their reftoration.

Some perfons, who intereft themfelves in the progrefs
of my experiments, induced me on the 27 th of June
laft, to cut an anemony of the firft fpecies perpendicu-
larly into four parts. For this pui'pofe I chofe a very
large one, juft taken out of the fea; and on cutting it in
that manner, it put forth twelve young ones. One of

thefe

leurs qu’il ell aflez ordinaire qu’une anemone, lorsqu’elle foufFre quelque incom-
modite notable, pouffe dehors Ies petits qu’elle renferme.

Revenons a notre moitle reformee : eliem’a donne une autre petite anemone le
5 A out, une le 27, une le 1 Septembre, enfin une plus grande que ies autres
lc 20 O&obre: jnfqu’au 7 Mars 1776, que j’ecris ceci, l’autre partie lie m’a
point encore donne de petits. Une chofe qui elx a remarquer, e’eft oue ies deux
monies- de [’anemone primitive, ni en fe reformant, ni apres s’etre reformecs,
ne m’en avoient donne aucun.

QiMques perfonnes qui s’intereffent a mes experiences, mhnviterent le 27
Juin dernier, a couper, perpendiculairement a fa bafe, une anemone de la premiere
efpece, en quatre parties, comme j’en avois coupe en deux : j’en pris une alter
Yol* LX VI]. M groffe

82. Abbe dicque mare’s Third EJfay

thefe quarters adhered the next day to the fide of the
vafe: on the 30th it had crept to the furface of the
water. It looked healthy till the middle of November;
hut at the end of the year the wound was not yet per-
fectly healed : neverthelefs, a few days after, it put forth
a young one of a tolerable fize. The cold of the 28th
of January feems to have accelerated its diflolution. The
fecond quarter had nearly the fame fate, except that it
yielded no young ones. The third produced, on the 6th
of September, a young one of a very fmall fize. On the
1 5th the wound feemed to be clofed, but its place ftill
appeared of a pale colour, tranfparent, and confiderably
deprefled. On the 30th it put forth another fmall young
one; and on the 26th of October, a third of a lbmewhat
larger fize. On the 29th of January 1776, after the
water had been often frozen, I faw it put forth three

young

grofle qui venoit d’etre pechee, et en la coupant ainfi, elle me donna douze petits.
Une de ces portions s’attacha le lendemain aux parois du vafe:- ]e 20 elle
etoit monteea fieur d*eau : elle a fait bonne figure jufqu’il la moitie de Novem-
b're : a la fin de 1’annee la playe n’etoit qu’fmparfaitement confolidee ; peu de
jours avant, fans avoir 1’aif vigoreux, elle avoit donne un petit un peu fort. Le
fircid du 28 Janvier a paru accelerer fa ruine* II en a ete a peu pres de meroe
de la feconde portion comme de la precedente ; mais elle n’a point donne de
petits. La troifieme m’a donne un petit d’une petiteffe extreme le 6 Septembre.
Le 15, la playe paroiffoit confolidee ; mais la marque en etoit tres fenfible par
la couleur pale, la tranfparence, et un refle d’applatiffement. Le 30 elle m’a
donne un petit tres petit, et le 26 O&obre un un-pcu plus gros. Le 29 Janvier

1 776,.

on Sea-anemonies. 83

young ones of a moderate fize. On the 3 1 ft it produced
a feventh ; but fince the froft it has ever appeared in a
weakly ftate. The fourth quarter, after feveral changes
in its ftate of health, produced, on the 29th of Novem-
ber, three young ones; one large, the other of a mid-
dling fize, and the third very fmall. After the fevere
cold it declined: it neverthelefs put forth three more
young ones, and died one of the firft days in March.
Thus from three of thefe quarters I had no lefs than
fourteen young ones, befides the twelve the animal had
produced during the operation. The interior contract
tions of the anemonies not only renders it difficult to cut
them into four parts ; but I have alfo obferved, that thofe
feftions do not ealily recover a cylindrical form, and
that they are ealily affected by froft or any other acci-
dent. This therefore is an experiment of little ufe,

which

1776, apres que Peau fut glacee plufieurs fois, j’ai vu naitre trois petits de
moyenne groffeur. Le 31 Fevrier ellenfien a donne un feptieme; mais depuis la
gelee, elle a fait mauvaife figure. Apres des alternatives de bon et de mauvais
etat, laquatrieme s.eft reformed, et m’a donne ie29Novembre trois petits, Pan gros,

I* autre moyen, et letroifieme tres petit. Depuis le grand froid elle alloit mal ; elle
a cependant donne encore trois petits, et s’eft decomp fee dans ics premiers jours
de Mars. Void done quatorze petits donnes par trois de ces portions, indepen-
damment des douzeque Panemone avoit rendus en la coupant. Non feulement il ell
difficile de couper exadement une anemone en quatre, a caufe des contradions
jaterieures; mais meme j’ai remarque que ces portions avoient bien de la peine
a reprendre une forme cylindrique, et que les accidens comme la gelee et autres,

M 2 les

84 Abbe dicquemare’s Third EJJay , 8cc.
which I only relate on account of the number of young
ones; and to fhew, that even a quarter of an anemony
tends towards refuming, and does fometimes actually re-
ume the cylindrical form, which is the figure of the
whole animal when it dilates itfelf.

les afferent beaucoup. C’eft doncune experience peu fru&ueufe, que je ne
rapporte qu’a caufe des petits ; et pour faire connoitre que jufqu’a un quart
d’anemone tend, et peut meme parvenir quelquefois a reprendre la forme
cylindrique qu’a Tanemone entiere lors qu’elle fe dilate.

VIII. Ear-

C 85 X

«s

\rill, Experiments and Obfervations in Electricity.

By Mr. William Henly, F. R. S.

P A- R T I.

Remarks on the effects of lamp-black and tar, or lamp-black
and oil, as protedlors of bodies from the Jlroke of light-
ning', .with fimilar effetfs produced by experiments in the
artificial electricity .

Read, Jan. 16 and 23, | Ar, lewis, inhis Philofophical Com-
^ merce of Arts, p. 364. mentions a;
remarkable inftance of the effect of a coating of lamp-
black, and .tar, in preferving thofe parts of the maft of a.
ffiip, which were covered with it, from damage by a
ftroke of lightning which fhivered the other, that is, the
uncaated parts of it, in a very extraordinary manner.
The account is recited at large in voL.XLV.III. of the
Philofophical, Tranfadlions. Captain nairne, in his
Remarks on . the Effedls of Lightning, on the mails of.
feveral velfels which were llruck in the Bafon at Que-
bec/^, mentions, in his letters to fome friends in London,
no lefs than five inltances, where the lightning palling

(a) His own.fhipj the Generous Friends r, was twice preferved there by.
his condu&or*

oyer

86

Mr. henly’s Experiments and

over thofe parts of the mafts of the flfips which were
covered with lamp-hlack and tar, or painted with lamp-
black and oil, without the leaft injury, Ihivered the un-
coated parts (tearing out fplinters five or fix feet in length,
and fix or eight inches deep) in fuch a manner as to ren-
der the mafts entirely ufelefs. A very curious inftance
of this kind hath lately been communicated to me by a
learned and ingenious member of the Royal Society, from
whom I received the account which I fliall here infert ver-
batim,

“ On the firft of April, 1776, being on board a brig
u in the latitude 340 N. our veffel was ftruck with light-
“ ning, which difabled our fore-maft. Upon getting the
“ whole of the top-mafts down upon the deck, I ob-
“ ferved the following particulars, with regard to the
“ courfe and effects of the electrical matter. The light-
“ ning had firft ftruck the pinnacle of the fore-top-gal-
“ lant-maft (on which, at that time, there happened to
“ be no iron fpindle, as ufual) which it juft fplit flightly
“ for about two feet and a half, where it was painted
“ with lamp-black and oil (I could not, however, afcer-
“ tain whether this part of the maft had been newly
“ fplit or not : it might have been firft occafioned by
“ driving in the iron fpindle, whereon a vane is ufually
•“ placed; for there was a hole where fuch a fpindle had

“ been

Obfervations in Electricity - 87

“ been fixed) and then the lightning immediately fhi-
“ vered the reft of that maft as far as it was greafed, till
“ it met the bottom of that and the top of the top-maft,
w which had likewife been coated over with lamp-black
“ and oil, on an old coat of tar. Over thefe it glanced,
u without any perceptible effect, till it reached that part
“ of the top-maft which was alfo greafed; this part it fhi-
“ vered, fplitting off large fplinters which were thrown
“ on the deck. The lower part of the fore-maft being
u tarred, the lightning Aid over it for about nine
u feet, without the leaft mark of violence; then darted
u into the fore-maft, where it was greafed ; rived it ter-
u riblv, tearing off fplinters as large as a man’s arm, and
“ four or five feet long, all the way down. It continued
H this courfe till it again met a coat of tar, which was
“ laid on the maft for more than five feet above the
“ deck; here its effects on the maft difappeared, and its
“ courfe feemed to be divided different ways by two at-
“ tractive bodies of iron ; one, in a cleet faftened to the
“ fore-maft, about ten inches below the top of the laft
“ mentioned coat of tar, by two large fpike-nails: this
“ cleet with the nails was entirely ftruck off; the light-
** ning then tore the canvas coating round the foot of
u the maft (about a yard below the cleet) without any
u other hurt to the maft itfelf; and from thence was

“ attracted .

88 Mr. henly’s Experiments and

u attracted by a large anchor lying in a horizontal pofi-
u tionon the deck, about two feet from the mail. All this
“ part of the electrical matter feems to have been then
“ difcharged by the different conductors of the two flukes
a and the main fhank of the anchor, without any other
u vifible eflfeCt than breaking a piece out of a large iron
“ pot, ftanding in an immediate direction to one of the
“ flukes, and about ten inches diftant. The other divi-
“ fion of the eleCtrical matter darted from the malt to
“ the belfry, about fifteen inches diftant, tore off two
£‘ cleets fattened to it by large iron nails ; then defcended
“ to the large iron hinges which hold the palls or ftops
“ (joined to the belfry-pofts) of the windlals, where,
“ after tearing off a fmall nail or two, it totally difap-
“ peared. The belfry which was painted was much
“ fplit, but not broke to pieces. The molt remarkable
“ part of this accident, and for which the whole relation
“ is given, is, the effeCt of the tar and lamp-black and
“ oil as impellents of the eleCtrical matter; for in four
M inftances, i ft, a t the head of the fore-top-gallant-maft ;
u 2(lly, at the bottom of that and head of the top-maft;
“ 3dly, at the bottom of the top-maft and head of the
u fore-maft ; and 4thly, at the bottom of the fore-maft;
“ the lightning had glanced over all thofe parts without
“ doing the leaft damage, and had regularly darted into,

“ and

Obfervations in EkShicily, 89

u and fhivered all the intermediate parts of thole mails,
u where they were covered with greafe. This appears
u lb extraordinary to me, that I thought proper to take a
“ note of it upon the fpot, in order to occalion the making
“ of fome philofophical inquiries and experiments on
<l the fubjecl by thofe more capable of accounting for it
u than myfelf : and for that reafon the above relation
“ may be depended on as juft and true, after a repeated
“ and critical examination of the feveral parts of the
u mails which I have defcribed. W. D.”

In confequence of this relation, and the hint which
concludes it, I have been induced to make the following
experiments, ift, A glafs tube, eight inches long, with
a bore or cavity of about a quarter of an inch diameter,
being filled pretty clofely with lamp-black, and each end
flopped with a bullet, the ftem of which juft entered,
and was cemented in the cavity of the tube, conducted
the charge of a jar containing three fquare feet of coated
furface inftantaneoufly, but with fcarce any expiation.
2dly, Such a tube being filled with a mixture of lamp-
black and oil (as ufed by the painters) entirely failed to
conduct the fhock. 3dly, The outer furface of fuch a tube
being painted with lamp-black and oil, and excited with
dry warm flannel, acted (the tube being alfo dry and
warm) as a very ftrong negative electric. 4thlv, A piece
Vol. LXVII. N of

go Mr. hetcly’s Experiments and

of polifhed plate glafs being introduced into the circuit,
the ends of the wires which compofed the circuit were
laid at about an inch and an half from each other upon
the furface of the glafs, when the jar above-mentioned
being difcharged, the polifh of the glafs was always torn
off in an irregular and deep line, extending from one
wire to the other; but if a piece of glafs painted with
lamp-black and oil were thus introduced into tho cir-
cuit, and the difcharge made as before, not the fmalleft
trace of the electricity could ever be perceived on its fur-
face. 5thly,.If inftead of the glafsj a flip of writing-paper
was introduced into the circuit, it was torn in pieces, by
the explofion, much of.it flying about the room in the
form of fine flue or down. 6thly, A flip of the fame
paper, painted with lamp-black and oil, received not the
leaf! injury, nor fhewed the fmalleft trace of the electri-
city upon its furface but the common oiled paper, with-
out lamp-black, was torn confiderably, though not fo
much as the paper unoiled !tK When the charge of the
jar above-mentioned is made to pafs between the furface

{ b ) Mr. cavallo, who hath fince repeated thefe experiments, finds, that
if the paper be very thinly painted with the lamp.rblack and oH, it will be torn
by the explofion;,; but having tried a piece of the fame that I had ufed in ray
experiments,, he was not able to make the leaft impreflion on it. Lamp-black
and tar therefore, on account of the greater tenacity of the latter, and its being
equally a non-conduflor, feems to be the moft proper for thepurpofe.

of

Obfervaiions in Ele&ricity . 91

of thick plate glafs, and that of a cylinder of -ivory three-
quarters of an inch diameter, preffed by a weight of
about fix or eight ounces Troy ; the glafs is always lhi-
vered into very fmall fragments, and part of it is fome-
times reduced to an impalpable powder. But ythly, If the
plate of glafs be covered with a Hip of writing-paper,
painted with lamp-black and oil, or with a flip of oiled
filk (fuch as is frequently ufed for garments) the charge
pafles over thefe fubftances without leaving the fmalleft
trace on either of them, though the glafs under them be
broken by the blow of the explofion.

From thefe experiments, and the obfervations above
recited, I think the following corollaries may be deduced,
1 ft, That a charge of .electricity, or a ftroke of lightning,
which is the fame thing, paffes, in many cafes, upon the
furface of bodies, in a much larger proportion than
through the interior fubftance of them, as appears by the
malls of fhips, coated with lamp-black, &c,. 'T andhy the
experiment above recited, with the cylinder of ivory and
the glafs See. ; for in this experiment, the charge being re-
filled by the ivory (which however is fometimes fplit by
the explofion) forces a paffage between that and the
glafs, and being there confined by heavy weights, exert?

(c) See a curious inFuuice of this kind in M. adanson’s Voyage to
Senegal, ^p. 239.

its

:n 2

gs Mr. iienly’s 'Experiments and

its expart five power in fuch manner as t ce to the
fmalleft fragments the plate of glafs then i pofed to its
violent operation, adly, This violent effort of the eledtri-
city produces not the leaft effedt upon the lurface of the
flip of paper painted with lamp-black and oil, or upon a
flip of oiled filk, placed in the fame fituation. 3dly, May
not therefore a coating of lamp-black and tar, or lamp-
black and oil, be in fome cafes ufefully applied on flight
buildings of Wood, See. to preferve them from damage
by lightning, as well as to prevent thofe large cracks and
rents (the ufual effect of the heat of the fun) from being
made in them ? 4thly, As the effedt of the lightning on
the mafts of fliips has been in fo many inftances pre-
vented by a coating of lamp-black and tar, or lamp-black
and oil, it feems probable, that a fafe and fixed con-
dudtor might be applied to them in a very cheap and
convenient manner, as follows ; viz. let all thofe parts of
the mail which are ufually greafed, be provided with
plates of metal three inches broad, which plates might
extend a few inches upon the other parts of the maft
which are coated with lamp-black and tar, or lamp-black
and oil; and thus by the condudtor of metal, and the
protedlor of lamp-black and tar, placed alternately and
extending the whole length of the maft, it would pro-
bably be preferved from damage by lightning. A

metallic

Obfervatians in EkBricity. 93

metallic communication might be made from the mail
to the water in the manner I have before mentioned, in
Phil. Tranf. vol. LXIV. p. 41 2. This method of making
conductors to fhips, from its fimplicity and practicability,
I had fome thoughts of recommending to my acquaint-
ance in the marine department; but there is one objec-
tion to it, which I think a very material one, and fhall there-
fore ftate it in its full force : it is this ; the lamp-black and
tar, or lamp-black and oil, though they protet, by their
property of repelling the eleCtric matter, thofe parts of the
malt which are coated with them, yet being perfect non-
conductors, thofe things or perfons which might hap-
pen to ftand in their vicinity (as in the tops, &c.) would
be in danger of a fevere itroke, perhaps deftruCtion, by
the lightning. How far the other oil colours, viz. thofe
prepared from minerals and metals, may anfwer thefe
purpofes, may perhaps deferve enquiry, and the morefo,
as the experiments are not difficult to make. The belfry-
pofts painted with white lead, mentioned in the letter
above recited, were much ffiivered. 5thly, As oiled liik
teems to be fo good a fecurity againft the effects of a
charge of electricity, may not garments, viz. cloaks and
hats, covered with that fubftance, contribute in fome
meafure to protect the wearers (if overtaken by a ftorm)
from a ftroke of lightning? particularly, if the precau-
a tions

94 Mr. henly’s Experiments and

tions be properly attended to, which I have before re-
commended from Dr. winthrop, in Phil. Tranf. vol.
LXIV. p. 1 5 1.

PART II.

On the 'electricity of chocolate : and the rejloration of that
property to it , when loji , by melting it together with a
, /mail quantity of olive-oil.

HAVING been informed by my ingenious friend
Mr. george adams, philofophical inftrument-maker to
his majefty, that Mr. sanders, an eminent manufacturer
of chocolate, had frequently obferved a very vivid light
flalhing upon its furface, when coohng in the tin pans in
which it is received from the mill; particularly in clear,
-frofty evenings, when it would alfo ftrongly attraCt light
fubftances, fuch as fmall particles of dull, bits of paper,
ftraw, thread, See. (i> ; I was very defirous to afcertain,if I
could, the caufe of thefe phenomena. For this purpofe
I waited on Mr. sanders., in company with Mr. adams,
and made the following experiments, ift, A large cake

( d ) The wax-chandlers alfo, in forming their flicks, kct of wax, are fre-
quently fpe&ators of thefe effefls of ele<5lnc*attra£lion.

of

Qbfervations in EleBricity. 95

of chocolate being turned out of the tin pan, in which it
had been fet to cool; I prefented towards it Mr. can-
ton’s electrometer, and obferved that, at fix inches dis-
tance, the balls began to diverge ; and when they came
within two inches of the chocolate (being fufpended over
it) their divergence was full an inch and an half, and upon
examining their electricity, I found the chocolate to be
in a plus or pofitive ftate. 2dly, Having Separated another
large cake from the pan, I touched it repeatedly with
the knob of a fmall phial, properly prepared for the
Leyden experiment; then bringing that knob gently
toward one of my knuckles, I faw a fpark between them,
and had a fmall fenfation in my knuckle. 3dly, Having
Separated another cake of chocolate from the tin pan
which contained it, 1 touched the cake repeatedly with the
brafs ball on the neck of my Leyden vacuum, or analyfis
of the Leyden bottle and inftantly perceived a moft
beautiful and large pencil of rays darting from the wire,
and Spreading themfelves through the bulb towards the
coated part of the bottle. 4thly, Changing the pofition of
the bottle, I prefented the coated bulb towards the cho-
colate,, and then perceived (as I expected) a fmall lumi-
nous fpark upon the point of the wire in the neck of the
bottle; completely proving the electrical quality of the

(e) Defcribed in Phil. Trank vert. LXIV. £, 400.

chocolate.

g6 Mr.' HENti’s Experiments and

chocolate, and ascertaining its direction in the experi-
ments.

Before I had an opportunity of making this com-
plete invefligation, I had feparated a piece of chocolate
from the tin pan in which it had been cooled, and acci-
dentally left, for fome months, under an open counter
in a fhop, expofed to dull, damp air ike. ; notwithstand-
ing which, on its reparation from the pan, it attracted a
thread of trial at a quarter of an inch diftance. I then
took a quarter of a pound of chocolate, and having
melted it in an iron ladle, poured it into a tin pan, and
the next day (it being perfectly cooled) feparated it from
the pan, and found it ftrongly electrified plus', but as the

electricity was foon loft by handling (owing, I fuppofe,

*

to the large quantity of conducting matter contained in
it) I melted it again, but produced no electricity; which
I imputed to the chocolate having become very dry and
powdery. I therefore melted it a third time, adding a
little oil of turpentine ; but this trial alfo (perhaps from
the evaporation of the fpirit) failed. I then melted it the
fourth time, and added a fmall quantity of olive-oil, Suf-
ficient as I imagined to reduce it again to its original
confidence, and having cooled it in the tin pan as before,
I found on removing it, that its eleClricity was completely
reftored. The large proportion of phlogifton in oil is
well known ; and as the addition of oil to the chocolate

completely

Qbfervations in Electricity. 97

completely reftored its electricity when loft, is not this
an indication of a great affinity at leaft between phlogif-
ton and the eledtric fluid, if indeed they be not the fame
thing d^? Further, as electricity is produced in the choco-
late by heat and fridtion, and manifefted by its ufual
phenomena in the cooling of that fubftance, query, may
not eledtricity be produced from the other oily nuts, ker-
nels, or feeds (particularly thofe of the torrid zone)
treated in the fame manner?

However, as the electric matter is refident in, and may
be difengaged from, all the fubftances we are acquainted
with ; as the air is at all times replete with it ; as its ope-
ation is fo fecret, fo rapid, and at times fo tremendous;
as it is fo eafily excited or put in adtion by fridtion, by
heating and cooling, and perhaps by means we are totally
unacquainted with; I think we may fafely conclude,
that electricity, as it is one of the moft powerful, is alfo
one of the moft important, agents in nature. Many ufe-
ful difcoveries have been made refpedting the adlion, in-
fluence, and effedts of this fubtile fluid; but certainly
much remains to be done, and the field for future la-
bourers feems daily to enlarge. Indeed, notwithftanding
the number of difcoveries in eledtricity this age may
juftly boaft of, I cannot but be of opinion (which I men-

(f) A thick leum from the furface of fome linfee-doil expofed to the air, anl
thoroughly dried, became a very Itrong negative eicftric.

Vol. LX VII. O tion

98 Mr. henly’s Experiments and

tion as an incitement to the ftudy) that, compared with
the facts ftill undifcovered in that branch of pliilofophy,
they bear but a very fmall proportion.

PART III.

Obfervations on fome new and fingular phenomena in ex-
cited and charged glafs ; with experiments jnade in con-
fequence of thefe phenomena, further illujlrating the
Franklinian theory of the Leyden bottle ; and a defer ip-
tion of the apparatus conjiru&ed for that purpofe by
Mr. HENLY.

HAVING carefully repeated the experiments with
the two coated plates of looking-glafs, mentioned in my
paper on Mr. volta’s machine, and finding with Mr.
lane, that they exactly agreed with the account given
by Mr. symmer and Mr. eeles, I was defirous to be fa-
tisfied whether glaffes of a different thicknefs would be
differently affected in the experiment. F or this purpofe
I tried two large fquares of crown or "window-glafs, and
found them to charge and difeharge exactly as the look-
ing-glafs plates had done ; but on trying the experiment
with two plates of Nuremburg glafs, commonly called
Dutch plates, I was not a little furprifed to find that each

of

Obfervations in Eleciricity. 99

of the plates, when feparated after charging, had a poli-
tive and a negative furface; and that having replaced
them, and made the difcharge as in the Leyden experi-
ment, the electricity of all the furfaces was changed,
though it appeared to be very ftrong, and continued to
give repeated dallies of light, when the plates were al-
ternately clofed, touched, and feparated, as the looking-
glafs plates above mentioned. If a clean dry uncoated
plate of looking-glafs was placed between the coated
plates, either of looking-glafs or crown-glafs, before they
were charged ; that uncoated plate was always found,
upon feparating them after charging, to be eleClrified
negatively oh both its furfaces ; but if it was put between
the Dutch plates, it acquired, like them, a pofitive and a
negative electricity . As this phenomenon was not fatif-
factorily accounted for, it occafioned much converfation
with refpeCt to Dr. franklin’s theory of the Leyden
bottle, which I had myfelf (as I imagined) fatisfaCtorily
explained and even demonitrated. I was, however,
foon convinced, that that theory is not fo generally
received as I imagined; for I met with a number of
gentlemen who not only doubted, but feemed abfolutelv
to deny it. This induced me to make feme further ex-
periments, in order (if I could) more fully to illuftrate
that theory, and to put the matter out of doubt. For

O 2

this

ioo Mr. henly’s Experiments and

this purpofe a pretty large jar was coated and furnifhed:
as in fig. i. a is the jar; bb the tin-foil coating; c a tin-
ftand which fupports the jar; d a focket of metal which
fupports a rod of glafs e ; F a curved wire or plate of
metal with points, not very fharp ; this wire or plate of
metal is fattened to the end of a brafs rod g, which rod
is moveable at pleafure in a fpring tube h, that tube being
fixed by a focket upon the top of the glafs rod e. The
charging wire of the jar communicates with both parts of
the infide coating of the jar by horizontal wires (the ends
of which are bent a little downwards) fixed at right an-
gles to each other, in order to prevent fhaking and ratling.

THE USE OF THE DOUBLE COATED JAR.

According to Dr. franklin’s theory, the fame quantity
of the eleftric matter which is thrown upon one of the
furfaces of glafs in the operation of charging it, is at the
fame time repelled or driven out from the other furface,
and thus one of the furfaces becomes charged plus, the
other minus ; and that this is really the cafe is, I think,,
fatisfattorily proved by this contrivance. For example,
place the jar as ufual, with the knob in contact with the
prime conductor ; then work the machine, and the appa-
ratus being perfectly dry and in good order, a fmall lu-
minous fpark will appear upon the upper point of the
wire f (a plain indication that the point is then receiving
6 electricity

Obfervations in Eleclriciiy. ioi

electricity from the upper ring of coating on the outfide
of the jar) and a fine flxeam or pencil of rays will at the
fame time fly off, beautifully diverging from the lower
point of the wire f upon the bottom ring of coating on
the jar. When thefe appearances ceafe, which they will
as foon as the jar becomes charged, let a pointed wire be
prefented towards the prime conductor; this will foon
difcharge the jar filently, during which the lower point
of the wire f will be illumined with the fmall fpark,
while the upper point of the wire will throw off a fine
pencil of rays, diverging towards the upper ring of coat-
ing, to which it Hands contiguous, as upon Dr. frank-
lin’s hypothefis it ought to do. A wire of the fame form
as that marked f may be inferted on a fmall eleCtric Hand,
fitted by a proper bafe to the bottom of the jar on the
infide ; this will fhew the appearances when the jar is .
charged negatively.

1 he fame experiment may be very conveniently made _
with a large pane of crown glafs ^ coated in two places
at a proper diftance from each other (fig. 2.) leaving a
fufficient quantity of glafs uncovered quite round the
two coatings. This coated plate of glafs fhould be fixed
in a frame, and mounted upon a proper eleCtric ft and.
Another Hand of glafs or fealing wax fhould be provided*

(g) Mine is eighteen inches by fourteen inches.

to

102 Mr. henly’s Experiments and

to fupport a wire or piece of metal placed horizontally,
and curved fo as to bring the ends of it, which fhould
have blunt points, within half an inch diftance of the
two tin-foil coatings on one of the furfaces of the glafs.
On the oppofite fide of the glafs, two wires, bluntly
pointed, are alfo to be employed; one of thefe is to com-
municate with the prime conductor, and to throw off the
electricity from thence upon one of the coatings of tin-
foil placed contiguous to it ; the other wire is to commu- '
nicate with the earth, Handing in a perpendicular direc-
tion, with the point bent towards and reaching within
.half an inch of the other coating of tin-foil (on the fame
fur face of the glafs) to receive the electricity thrown off
iby that coating, while the oppofite fide is charging.

EXPERIMENT.

"The apparatus being perfectly dry (the uncoated part
K>f the glafs and the frame, &c. fhould be varnifhed),
clean, and in good order; the plate of glafs fhould be fo
fixed, that each of the four coatings of tin-foil may come
within half an inch of the point of the wire oppofed to
it. The apparatus being thus placed, if a powerful ma-
chine be worked in a dark room, the electricity will be
feen to iiTue from the point of the wire in contact with
?the prime conductor upon one of the tin- foil coatings a

(fig-

Obfervations in EleBricity. 103

(fig. 3.) charging it pofitively. The coating b (fig. 3.)
on the other fide of the glafs throwing off, at the fame
time, an equal quantity of the electric matter, (vifible in
the form of a fmall luminous fpark upon the point of the .
infulated wire f) is thus left in a negative ftate. The
electricity palling along the infulated wire, flies off from
the other point of it in a pencil of rays, diverging upon
the tin-foil coating c (fig. 2.) on the fame fide of the
glafs, charging it pofitively; while the oppofite coating
D (fig. 3.) throws off its electricity, which is received in
a fmall fpark upon the point of the wire (g) oppofed to
it, and communicating with the earth. Thus, by the
fame operation of the cylinder, may a pofitive and a ne-
gative charge of electricity be obtained at the fame time
upon each furface of the glafs; and by applying two
curved difcharging rods (which fhould have glafs handles)
at the fame inftant, fo as to come nearly into contact with
the coatings upon each furface of the glafs, the whole
will be difcharged together; or if a pointed wire be pre-
ferred near to the prime conductor, they will all be dif-
charged filently, and then the appearances on the points
of the wires will all be reverfed; that which was a brufh
or pencil of rays being now a fmall luminous fpark, and
that which was a luminous fpark being a brufh or pen-
cil of rays. If the machine be very powerful, the

rubber

ii04 Mr. henly’s Experiments and

rubber may be infulated, and a blunt pointed wire, com-
municating with the earth, may be placed within half
an inch of it ; this wire, while the plates are charging,
will throw off a beautiful pencil of rays diverging upon
the rubber, and thus compleatly exhibit the progrefs of
the eleddricity through all the apparatus, from its exit
out of the earth to its entrance into the earth again : and
its return may be manifefted by reverfing all the ap-
pearances upon the points of the wires, in the operation
of difcharging the glafs lilently by a pointed wire pre-
sented toward the prime conductor, as above directed.
Another very fatisfadlory method of demonftrating the
truth of Dr. franklin’s hypothefis is as follows. I take
a bottle, containing about one hundred fquare inches of
coated furface, properly prepared for the Leyden expe-
riment, and holding it by the wire, I fet the coating upon
the prime conductor, and charge it negatively (fig. 6.);
when charged (if not too dry) the upper edge of the
coating will throw off one or more pencils or brufhes of
light into the air, which vifibly incline towards the
charging wire of the bottle, and fometimes actually reach
it. If I hold the bottle by the coating, andprefent the knob
to the prime conductor, charging it pofitively (the bottle
being in a proper ftate) a fmall lpark of light firft appears
rnpon the edge of the cork in the neckof the bottle, through

which

Obfervations in EleSIricity. 105

which the wire pafies ; after a few turns of the globe,
this fpark becomes a fine brufh, darting out from the
cork, and gradually lengthening, till it forms a beautiful
arch, the end of it regularly extending downward,
till it reaches the edge of the coating and refts upon it
(fee fig. 5.). I remember, when I firfl: fhewed thefe
experiments to my fincerely refpeCted and worthy friend
the late ingenious Mr. ferguson, f. it. s. he exprefled
great fatisfaflion ; and allured me, that he thought
them fome of the molt convincing he had ever feen
exhibited for the purpofe. If the bottle be dry, it will,
in both cafes, be difcharged fpontaneoully ; but if the
uncoated part of the glafs be then breathed upon, the
appearances may be produced at pieafure. I have lately
prepared another bottle for this purpofe, the infide of
which is coated in the ufual manner; but the out fide is
covered with fquare pieces of tin-foil about a quarter of
an inch broad, and about three-fixteenths of an inch
diftant from each other; the bottom is compleatly co-
vered with the coating (fig. 4.). If in charging this bot-
tle, the electricity pafled abfolutely through the glafs, it
would find a ready conveyance by the coated bottom into
the table (and then indeed it could never be charged at
all) ; but the truth is, that this bottle does not become
charged till ftrong flafhes of electricity have pafled,
Vol. LX VII. P diverging

to6 Mr. henly’s Experiments and

diverging in different directions quite round it. If it be
difcharged by bringing a pointed wire near the wire, or
the prime conductor, with which it is in contaCt, the noife
it occafions much refembles the report of a fired cracker;
and the uncoated glafs between the fpots of tin-foil is
very brilliantly illuminated. If the bottle difcharges it-
felf fpontaneoully, or be difcharged fuddenly, by making
a regular communication by the rod between the two fur-
faces of the glafs, the whole outfide furface feems to be
illuminated. To produce thefe appearances the glafs
muff be thoroughly dry.

XXTEEIMENT.

A fmooth piece of mahogany, two inches fquare and
five inches long, was hollowed into an elliptic groove,
about three-quarters of an inch deep, and painted with
lamp-black and oil. Into this groove two wires, termi-
nated by brafs balls each three-quarters of an inch in
diameter, were introduced; the brafs balls being placed
about one inch and an half from each other : between
the brafs balls, at an equal diftance from each, was
placed a ball of the pith of elder, half an inch in dia-
meter, nicely turned in a lathe. The apparatus being
thus adjufted, and the circuit compleated by a fhort chain,
a bottle, containing forty fquare inches of coated furface,

was

Qbfervations in EleBricity. 107’

was many times difcharged through it ; and whether the
bottle was charged pofitively or negatively, the pith-ball
conflantly moved in the direction of the fluid, according
to Dr. franklin’s hypothecs- This is a delicate experi-
ment; but, as I have perfectly fucceeded in it, I thought
it proper to give this fhort account of it. Perhaps if the
pith-ball were fufpended by a filk firing, it might anfwer
the purpofe as well ; but this I have not tried.

E X P E R I M E N T.

In melting fmall wires fome inches in length, I have
often obferved the wire to become red-hot, firfl at that
end in contadt with the ddl'charging rod, and the rednefs
has proceeded gradually and regularly towards the coat-
ing of the jars or battery;, plainly and fully demonflrating
the direction of the eledtric matter in the difcharge of
the jars or battery, which,, for this experiment, were al-
ways charged poiitively. This phenomenon hath alfo

* N

been obferved by Mr. bell, and many times by Mr.

NAIRNE*

EXPERIMENT.

Before I quit the fubjedl of the Leyden bottle, I fhall
mention one experiment more which I have lately made,
andwhich gives a full andcompleatanfwertoaparagraph
in Dr. Priestley’s Hiftory of Eiedlricity, 2d edit, p, 465,
1. 21. It is this 1 1 procured fome phials coated with fil-

P 2 ver.

10S Mr. henly’s Experiments and

ver, by burning it into the very fubftance of the glafs, in
fuch a manner that nothing can remove it without injuring
the glafs together with the metal. Glafs thus coated
and bimrifhed has certainly a moft elegant appearance*
has no inequalities or points upon its furface, and charges
as high and as readily as when it is coated with tin-foil ;
fuch glades will difcharge fpontaneoufly, and one of them,
which was very thin, was burft by the explofion ; an acci-
dent which, by this double annealing, I was in hopes to
have prevented, but was forry to findmyfelf difappointed.

OBSERVATIONS ON EXCITED GLASS,

In my remarks on Mr. volta’s curious little machine
lately prefented to the Royal Society, I have obferved
that the eledtric matter, being once thoroughly excited
and put in action, is not fo foon as might be expelled
reduced again to a quiefcent hate, efpecially in bodies fo
peculiarly adapted to affeft each other as thefe appear to
be. As a proof, I introduced the experiments with the
looking-glafs, crown-glafs, and Dutch plates. I alfo men-
tioned Dr. Priestley’s obfervations on the refiduum of
his battery ; and in a note to that paper, I added an ex-
periment made by my friend the rev. Mr. hemming,
f. r. s. who fhewed me a fmall bottle, which then at-
tracted a thread of trial, though it had flood in a cup-
board

l

Obfervations in Eleffriciiy.. io<j

board in his ftudy feventy days from the time he charged
it. I alfo mentioned a Angular effect of his cylinder,,
which will feparate the balls of Mr. canton’s eledtro-
meter, at twelve or fourteen inches diftance, fometimes
a fortnight after ufmg, though the air of the room may
have been many times changed, and 3. variety of methods
ufed to deilrey that power in the interval. As the detail
is curious, I fhall here iniert one fet of experiments,
as I find them regiftered in a journal, which Mr.
hemming took the trouble to make for my fatisfac-
tiqn. On May 1 3 177 6, the cylinder was ufed, and
when placed in the cupboard at 1 o o’clock a. m. it fepa-
rated the balls at feven inches diftance. The power was
then entirely deftroyed by breathing on it, and the elec-
tricity marked o, From that time the journal proceeds

as follows:

it'i. .

Day.

* Hour*

Diftance at which the
balls diverge.

May 13 „

X I t A. Mi.

7 inches,.

*4 0

;8 A. M..-

i * « - i 1 .

*3

Breathed on it once.

V f

i . « / 1

9

Ditto four times,

» .A 6 i

8

Door open till

. 9j A\ Mi,

orrfeli I>oi rA

14

3 P. JM.
7 P. M.
10 Po M..

7

6

Breathed]

■ ■

1 1 o Mr, henly’s Experiments and

Day.

Hour.

Breathed on it twice,

May 14 1 of p. M-.

15 8 p. M.

Door open ten minutes,

Didance at which die
balls diverge.

o inches
6

13 wind N.
8

9 P. M.

ro r. m.

The power deftroyed by flame,
16 7 A. M.

18 8 P. M.

13

8

o

i4f wind N:
1 7 wind N.,

I I P. M.

Deftroyed by flame,

ao A fire in the room the whole day.

4 p. m. 2

8 P^ M- 1

10. p. m- 3

21 7 A. M.. 9

9 p. h. 9

Deftroyed by flame quite round o

22 7 a. m. 8f

10 a. m. nf wind N,

Applied flame quite round the cylinder, o

1 P. M- 1 2f

May

Ill

Qbjervations in Electricity.

X>3Y. Hour. Diftance at which the

balls diverge.

May 22 4 P. m. ia{ inches.

8 P. M. O

IO~ P. M. 2

23d, Mr. hemming (hewed me the experiment, when I
faw the balls feparate at twelve inches dillance from the
cylinder. The caufe of thefe phenomena is, no doubt,
the excited eleilricity lodged in the pores of the glafs
acting upon the vapour in the air of the room, and pro-
ducing a greater or lefs effect, as circumftances may
contribute to inereafe or diminifh its operation. The cy-
linder was now ufed again, which clofed this fet of ob-
fervations. Mr. hemming has added a meteorological
journal for the time; but the particulars of this I did not
think it neceflary to introduce in the above extrail.

A SECOND SET OF OBSERVATIONS.

Feb. 3, 1777, the cylinder was excited, and from the
5th to the 1 4th no fire had been made in the ftudy.

Day.

Hour.

Diflajiee at which th«

balls diverge.

I4^

3

P. M,

7 inches.

J!

TO

B. M*

0

1 5

9

A. M*

1 1

(b) Thisvwas the firft time, fince Augufl or September* that I had obferved
<my cylinder to retain its attra&ive power longer than twelve hours alter being
excited, though it was conftantly ke; t in the fame place, and, as well as I caa
obfery.e, under the very fame circuipftancss.

fr a Mr, henly’s Experiments and

Hour.

Diftance at which the
balls diverge.

Feb. 15 4 p. M. 8 inches.

. - 9 p. m. o

IO P. M. O

A large fire in the itudy the whole clay.

l6 9 A. M. 9

12 9

8 P. M. o

1 - j ^ ■ • y * • ^ 7 r * «r . r „ . . ^ • s\

10 p. m. o

17 9 A. M. 3

6 P. M. 2

II P. M. O

H

00

.*?

A. M.

Abfent till a ad,

3

P. M.

6

P. M.

7

P. M.

Dili L .... i . :;.f; . y.

1 1

P. M.

23

8

A. M.

a

P. M.

C - . .

5

P. M.

0

9

P. M.

■*- ~ 1

11

P. M.

24

9

A. M.

.

12

V; ^

3

P. M.

2 .
8
2

o

o

7

2

O T

o

o

o

o

Feb.

o

ObfervationS in EieSiricity. 113

Day.

Hour.

Diftance at which the

balls diverge.

Feb. 25

9

A. M.

2 inches.

Abfent till 28 th,

3

P. M.

2 .

9

P. M.

0

Mar. x

9

A. M.

0

The fire in the ftudy put out at noon.

10

P. M.

O

2.

9

A# M.

O

1

P. M.

O

Abfent till 8 th,

3

P. M,

9p

6

P. M*

*1

I

>P* M*

0

9

I-OJ

8

1

A. M.

9

T

4

8

>P. M,

a

10.

1

10

8

A. M.

8

The cylinder was

now excited again,

which clofed this

fet of obfervations. Thefe changes in the electricity feem
very extraordinary, and I think them not ealily to be ac-
counted for, as they happened in ftates of the weather
which were totally different. I regret, however, that an
accurate and fenfible hygrometer was not obferved the
Vol. LXVII. Q whole

i-iyfc Mr,. HENLT’a Experiments and

whole time; and for fuch a purpofe I fhould recommend

Mr. Co ventry’s, made with a number of circular pieces of

iffue-paper, amounting to a certain weight, thoroughly

» ■ » • ' r ■

heated and ftrung on a thread, 'kept feparate from each
other by a fmall glafs bead, andfufpended on one of the
ends of a lever, nicely poized, and turning freely:on its
axis; the other end ferving as an index to a graduated
fcale, on which it fliews the weight of the moifture im-
bibed at any time by the papers.- This hygrometer, from
its extreme fenfibility, I fhould choofe, 1 fay, to recom-
mend for this purpofe, in preference to any other that
I have ever feen.

HAVING lately had o'ccafion to fhew the experi-
ments with the coated Dutch plates to an excellent elec-
trician (Mr. cavallo) and having charged them as high
as I could, and feparated them I think rather more expe-
ditioufly than ufual, I was- aftonifhed to find, that the
very fame plates I have fo often mentioned were now
charged, the one pofitively, the other negatively, on both
furfaces. I then laid them together, and having made
the difcharge as ufual, I feparated them, and found one
of the plates negative on both fides, and the other plate
pofitive on one furface, and negative on the other. Here
was a new caufe of admiration, and I was utterly at a lofs
to account for it, as the plates had in every inftance be-
fore

Obfervations in Electricity. 1 1 5

fore uniformly aCted as reprefented in my paper. At
length I recollected, that this experiment had been made
rather more expeditiouily than ufual: I therefore re-
peated it, and having allowed fomewhat more time be-
tween the removal of the plates from the prime con-
ductor, and the feparation of them, in order to examine
their electricity, I found on each plate a pofitive and a
negative furface; and having replaced them and made
the difcharge, I obferved that the electricity of all the
furfaces was changed. I have mentioned this circum-
ftance, to fhew how fmall a difference in the manner of
making an experiment, will make an effential difference
alfo in the refult. There is fomething, however, very
lingular in this kind of glafs, which I believe is owing to
its not being properly annealed ; for I once met with a
plate of it which I found very difficult to charge at all ;
and when a fmall quantity of electricity had been forced
into it, it diffipated proportionably fooner, without the
ufe of the difcharging rod.

In glafs, properly annealed, whether in the form of
plates or jars, prepared for the Leyden experiment, the
diffipation of the electricity is, in forne Hates of the atmo-
fphere, a remarkable, and fometimes (when there is not
a fire in the room) a difagreeable circumftance : this ef-
fect, however, in the jar itfelf, may be in a great mea-
fure prevented, by having the uncoated part of the glals

Q 2 neatly

Mi1> Mr. henly’s Experiments and

.neatly covered with the beft varnifh/^ ; and I fhould not
omit to obferve, that Mr. hemming’s bottle, which re-
tained its charge fo long, was prepared in this manner.

POSTSCRIPT,

.• Containing fome experiments and obfervations on Mr.
volta’s machiney by Mr. tiberius cavallo, -with
remarks by Mr. henly.

Mr. volta’s machine, which occafioned feveral of
the preceding enquiries, hath lately been made by Mr.
cavallo, by coating the glafs plate (about fix inches in
diameter) with fealing-wax. With one excitation of this
platehe foon charged a bottle compleatly, and with that
charge pierced three holes in a card, which he hath fince
fhewed me. If, when this machine aCted vigoroufly, he
inverted the excited plate, and fet the brafs plate upon
the glafs, he produced a contrary electricity, but in a
much fmaller degree. If when -the fealing-wax was
ftrongly excited, fo that fparks, two inches long, might
be * drawn from the brafs plate, -the excited wax, &c.

' was placed on an eleCtric Hand, and the procefs continued
- as ufual; the fparks from the ibrafs plate prefently dimi-

The-varnilhing fhould be feveral times repeated.

nifliedj

"Obfervatiom in EleSIricity. 1 17

■-nifhed, and in a fhort time ahnoft totally ceafed: this,
5 think, clearly indicates that the electricity in the lower
.furface of the glafs and the table were mutually affeCted
in the operation, as well as that, in the excited fealing-wax
and the brafs plate (h) . 1 have feen one of thefe machines,
made by Mr. cavallo, aCt fo fkrongly that, -upon fepa-
rating the brafs plate from the fealing-wax, a flafh has
ftruck from 'the brals toward the table, and it has betides '
given a ftrong fpark upon the knuckle, when held at up-
wards of an inch diftance. If the brafs plate, after being
.raifed from the wax, be prefented with- its edge toward
the wax (lightly touching it) and thus drawn over its
furface, the electricity of the plate, he obferves, will be
abforbcd by the fealing-wax, clearly fhewing the ftrong
negative ftate in which the excited wax is left on the re-
moval of the brafs plate.

The attraction between the plates is alfo fometimes fo
ftrong, that the coated glafs has frequently been lifted
up by the’ brafs plate from the table ; yet in a few days,
being carefully placed in a proper repofitory.(in contaCt
with each other) not the leaft fign of electricity has been

( h ) It has beea fuppofed by fame gentlemen, that the very fame quantity .of
eleCtricity imparted by. the linger to the plate on touching it, was emitted again
by the plate on removing it from the electric and prefenting it towards the
knuckle; and that therefore, in air perfectly dry, this machine would at all
times exhibit its phenomena, without a. frefh excitation of the eleCtric, and
thus merit the appellation of a machine for exhibiting perpetual electricity-; but
the faCt a !>eve mentioned entirely refutes that fuppohtiom

2 'difcoverable

1 1 8 Mr. henly’s Experiments and

difcoverable on their reparation: fo far is even this ma-
chine from exhibiting perpetual electricity. Indeed, in
this particular, it is far exceeded by Mr. grey’s apparatus
of the cone of fulphur in the glafs, which, on being fe-
parated, I have never perceived to fail of exhibiting
iirong figns of electricity, in every hate of the weather.
To this apparatus I have lately added the improvements
of M. jlpinas, and find that they fully anfwer his report.

THE following paper contains a fet of experiments
which may perhaps lead to fome curious, ufeful, and im-
portant truths in electricity. They are made with the
moft fimple apparatus, and in the moil fimple manner;
nothing more being requifite for this purpofe than a few
fticks of fealing-wax (one of them being referved as a
teft) to the ends of which the fubltances to be examined
are to be fixed or tied as occafion may require, and Mr.
canton’s electrometer, neatly made and properly infu-
lated. With this fmall apparatus may almoft every ar-
ticle that can be propofed be examined with the utmoft
facility. The animal, the vegetable, the foflil kingdom,
with all the works and combinations of art and manu-
facture, may afford materials ; almoft any of which, by
a flight friction againft woollen cloth or filk, will become
c electrified

Obfervations in Ele&ricity \ 1 1 g

electrified (either positively or negatively, according to
the nature of the fubftance and form of its furface, and
the quality and furface of the rubber) Sufficiently to Se-
parate the balls of the electrometer, So as to determine
their electricity in a very Satisfactory manner. This, I
think, fully confirms an opinion I have long entertained
and mentioned in a former paper, viz. that the Slightest
friction of bodies of every kind, in every fituation, may
difturb the electric matter contained in them, though the
effect be imperceptible to us, having no electrometer nice
enough to difcover it. Here, therefore, is a boundlefs
field for future enquiry; and, to affift thofe who may be
inclined to profecute it, I Shall mention a few general ob-
servations and precautions, which I have found exceed-
ingly ufeful in the courfe of my own experiments, iff,.
The air Should be dry, and the apparatus clean and warm,
adly, The fubftances to be tried Should be perfectly clean.
3dly, When the rubber hath been ufed once or twice, it
Should be held near the fire or the flame of a candle,
not only to prevent its acquiring moifture, but to take off
the electricity left in it by one Substance, before another
be examined ; for it Should always be remembered, that
whenever a fubftance is made eleCtrical by friCtion, the
rubber acquires the contrary electricity, and this electri-
city, if it be not carefully taken off as is above directed,

will

12.0 Mr. henly’s Experiments and

will fometimes remain in it fo as to confufe and adtualif -
miflead in the experiments. 4thly, Some minute fub-
ftances, as a fmall leaf, feed, or hair, will not be eafily
excited in damp weather; thefe, therefore, as well as the
apparatus, fhould be warmed; for heat, I find, doth al-
ways difpofe bodies to become eledtrical. 5thly, The in-
fulating Hands, and the flicks of fealing-wax, with which
the fubftances to be examined are connected, fliould not
be rubbed, left they, by the fridtion, fliould be made
eledtrical, and, adting through the fubftance in contadl
with them, deceive in the experiment. Gthly, The ani-
mal fubftances, as hair; horn, bone, cartilage, nails, teeth,
mufcles, See. become eledtrified pofitively, by friction,
againft woollen cloth or black filk; and the. vegetable
creation, with very few exceptions, negatively. The metals
differ with refpedt to kinds, form, and furface, and may be
differently affedted by different rubbers. Laftly, I muft
not omit to obferve that, among vegetables, I find the hot,
acrid, pungent,,and aromatic fubftances, as the fpices,8ec. to
be much more eafily excited, and ftronger in their power,
than the cold ones, as the feeds of gourd, melon, or cu-
cumber. Among the herbs, hemlock and parfley are
ftrong : a Angle leaf of laurel, bay, yew, rofemary, See.
will be found very powerful; but, as I have before ob-
ilwvcd, this field is indeed immenfe, and life itfelf too.

fhort

Obf emotions in EleBricity. 1 21

fliort for a corapleat investigation. The experiments
prove, however, how univerfally the eledtric matter is
difieminated; or, in other words, its exiftence in all bo-
dies ; with what readinefs it is excited ; and, I think, the
conftancy of its adtion*( though imperceptible to us) as
well as its ufe and importance as a principal agent in the
greateft, and to mankind the moll interefting, operations
in nature. I have enclofed a catalogue, exhibiting at
one view the articles I have had an opportunity to try,
with their kinds of eledtricity marked againft them;
hoping this fpecimen may induce gentlemen of more
leifure to purfue the enquiry.

Hair, wool, down, and many other articles, may be
made up in the form of little taffels, and in this manner
readily fixed upon or tied to the end of an eledtric for
experiment.

Vol, LXVII.

II

The

122 Mr. henly’s Experiments and

The following fubftances being fixed or tied upon the
end of a flick of fealing-wax, and excited by friction
againft a woollen garment or a piece of foft black filk,
became electrified as marked in the columns of the
annexed table. The ftrongeft in power are diftin-
guifhed by the letter s, and the weakeft by the let-
ter w.

)

r

METALS.

A new guinea ; a fmooth fix pence ; a

brafs ferule; tin, and tin-foil; enamelled

>

copper, s; gilding on leather, s; lead
ore; copper ore; iron ore; ftream tin
Milled lead ; copper, s ; a polifhed fteel
button, s; a new filver ditto; a metal
button gilt, s ; tutenague ditto, s ; iron ;

Lead from a tea-cheft, in which there
is a mixture of tin, w ;

A gilt button,, bafket pattern; the
juncture at the end of a brafs ferule ;

Wool. Silk.

Neg. Neg.

Pof. Pof.

Neg. Pof.

Pof. Neg.

A N I M AL

Obfervatiom in Ete&ricity*
animal substances.

Tortoife-fhell, w; ivory, s; Lone, s; \
horn; lamb’s-tooth; horfe’s-hoof; deer’s-
hoof; mufcle of the leg of a deer, s;
cartilage, s; fpur of a young cock;
bill, claw, and fcale from the leg of a
turkey, s ; fcale of a carp; the chryfalis of
a moth, recent from the earth, cleanfed ;
crajjamentum of the human blood ex-
ficcated, w ; quills ; claw of an unboiled >
lobfter; cowrie and feveral other fmooth
fhells, s; fhell of a hen’s egg; tail of
a fmall filli ; thigh of the elephant bee-
tle ; a fmall beetle, fmooth furface ; hu-
man hair; red and white horfe’s and bul-
lock’s hair, s; hog’s briftles, s; wool;
lilk from the worm, w; oyfter-fhell,
fmooth furface ;

Mother of pearl, and feveral other 1
fhells ; j

Mufcle and cockle-fhells, recent ; a re- i
cent fnail-fhell, rough furface ; elitra of /
the flag-beetle ; oyfter-fhell, rough fur- (
face ; J

123

Wool. Silk.

Pof. Pof.

Neg. Pof.
Neg. Neg.

Mr ► henly’s Experiments and

.1*4

VEGETABLES.

Rind of cheftnut, s; Barcelona nut- 1
fhell, s ; cafhew nut, s ; cocoa nut-fhell
politlied; brazil; lignum vita ; black
ebony, s ; box, w ; cane, s ; quinquina ,
or Peruvian bark, s ; tamarind-ftone ;
coffee-berry roafted, s ; nutmeg, s ; gin-
ger, s; white pepper, freed from the
hulk, s ; cinnamon, s ; cloves, s ; mace, s ;
all-fpice, s ; capficum, both fides of the
pod, s ; hemlock, s ; a clove of garlic ;
ditto of efchalot, freed from the hulk, s ;
a green onion, s ; rue, s ; cork, s ; leaves
of laurel, bay, yew, holly, rofemary, with
their berries, s ; parfley, s ; leaf of tur-
nip; ditto of Savoy cabbage, s ; celery, s ;
fago, s ; thime, s ; carrot ; turnip ; potatoe ;
an acorn, s ; rind of Seville orange, s ;
a large Windfor bean, s; a white pea;
root of the white lily; fnow-drop root;
feeds of gourd, melon, cucumber, w ; a
fpecies of long-mofs, w; an apple, s;
down of the cotton-rufh, w; fea-flag;
leaf of the American aloe, s ; cotton, w;

Wool. Silk.

Neg. Neg.

Hemp ;

Obfervations in Electricity.

Hemp; flax; ftalk of the tobacco-leaf; '

Wool.

Silk,.

fpike, from the leaf of the American aloe ;

► Neg.

Pof.

palma-cbrijli nut ; horfe-radifh ; .

A white kidney-bean, fmooth furface ; '
black negro of the fame ; fcarlet of the
fame ; J

| Pof.

Pof,

CORALLINES. ,

|

Sea-fan, the horny part, w ; rough
coral, w ; -

l Neg.

Pof.

Spunge, w ; coral polifhed, w ;

Pof.

Pof.

S A L T s.

Allum, w,

Neg. Neg.

Borax, 1

,T. ' .r. ? fmooth furf aces ;

Nitre purified, J

| Pof.

Pof.

FOSSIL AND MINERAL SUBSTANCES.

Common pebble-hones of all colours, ,
s; marble, s; pit-coal, s; black-lead, j

r

w; jet, s; aJbeJlos\ mineralized ful- >
phur; thunder-bolt hone ; cornu-ammo- 1

; Neg. Neg.

nis; fhark’s-tooth; coat of petrifadtion ; J

Several fmooth native cryftals ; brown '

Iceland ditto; talc , s; Ceylon pebble, /
fmooth and tranfparent; agate, s; corne-

> Pof.

Pof.

lian; amethyft, s;

A lpecimen

1 26 Mr. henli’s Experiments and

A fpecimen of gypfum>

<+. -- k •

ARTIFICIAL SUBSTANCES.

Staffordfhire ware glazed ; China ware,
s; Wedgwood’s ware glazed, s; whale’s
fin prepared, w; writing-paper; parch-
ment, s; fheep’s gut,

Tobacco-pipe, s; Wedgwood’s ware
unglazed ; elaftic gum, s ; hard under-
cruft of a leaf; a tallow-candle, w; oiled
filk ; painted paper, s ; filver, burnt into
glafs, unburnifhed ; pearl-barley, w ; In-
dian ink, w; blue vitriol, s,

Dr. lewis’s glafs porcelain,

Silver burnt into glafs, burnifhed, could not be excited
either with the woollen or filk. It is fuppofed that the
fubftances being fo intimately incorporated or blended
together, the fridtion at the fame time excited both the
fubftances, fo as to counteradl and deftroy the effedt of
each other.

In thefe experiments I have been affifted by Mr. ca-
vallo and Mr. adams, who have carefully repeated
them in mv prefence. It may be proper to obferve alfo,
that the white pea, a fcarlet bean, and the thorn from

the

Wool. Silk.

Neg. Pof.

Pof. Pof.

> Neg. Neg.

Neg. Pof.

3

Obfervations in Electricity. 137

the American aloew, being rubbed upon new, fine, cla-
ret-coloured cloth, became weakly electrified pofitively.

A lock of black hair from a young colt I have ob-
ferved to become very weakly electrified negatively,
when excited either with wool or filk.

It will be proper to obferve, that the rubber of wool-
len cloth, which I ufed in the preceding experiments,
was a part of the coat or waiftcoat which I happened to
wear at the time ; but being defirous to try the effeCt of
another, I took a piece of fine, new, white flannel, and
ufing that fide of it which is free from knap, I perceived
a remarkable difference; viz. the copper and other but-
tons, the different ftones,, fliells, China ware, mofi of the
animal fubftances (hair excepted) and all the vegetable
ones, which with the former rubbers were pofitively,
being now negatively electrical ; but thofe which were
negative with them, I found to be negative with thefe
alfoAA In all the experiments with the flannel, I had

hitherto

(h) All thefe fubft’ances have fmooth furfaces.

(i) On this'1 account an ingenious friend of mine propofed the following;
queftion, vi%. Whether, if the elediric matter were inherent (as I aflerted) in:
the different fubftances I examined, the kind of ele&ricity could be changed by.
the ufe of different rubbers? I reminded him of Mr. canton’s experiments
with a glafs tube, and informed him, that a ftick of fealing-wax becomes pofi-
tively eleftrified by dipping it in quickfilver, or exciting it with a flip of tin-
foil ; that a fmooth glafs tube may be made negative by drawing it cxofs-wjfe

over

128 Mr. henly’s Experiments and

hitherto warmed the fubftances, but kept the rubber
cold ; fufpefting that, in fome cafes, the refult might be
different from what it is when the rubber is warm and
the fubftance cold: but this, with the effect of cloths of
different textures and colours, filks, fattins, velvets, lea-
ther drefled in oil, and in allum, &c. ufed as rubbers, I
have not had leifure to determine. A fmall turnip and a
potatoe, which I could not excite at all with either of the
rubbers when they and the fubftances were cold, I ex-
cited in a very fmall degree with the flannel a little
warmed ; but very ftrongly when the flannel and the re-
fpective articles were, each of them, moderately warm.
A fprig of celery ailed very powerfully when the
flannel only had been previoufly warmed <k]. As in all
cafes the rubber is affeited with an electricity contrary
to that of the fubftance rubbed, it will be fufficient for

oyer the back of a cat, or by exciting it with a dry, warm rabbit’s fkin ; that
a fmall coated bottle may be charged with a flip of writing-paper, excited by
drawing it brifkly between the fingers of a dry hand lo as to pierce a hole in a
card; that the dry leathern cover of a book may be m .de ftrongly electrical by
the frlCtion of a dry hand, and that its eleCtricity is remarkably fhewn by
touching it with an infulated button, in the form of the plate to Mr. volta’s
machine. He then acknowledged, that fuch an objection as he had darted muft
certainly be groundlcfs.

(k) A palma-chrijii nut was excited very ftrongly with the flannel, weakly
with my coat, and not ail (in a room where there was no fire) with the black
filk. I have alfo to add, that fome particular fubftances, though negatively
eleCtrical when heated, become pofitive when cold, by friction againft the very
fame rubber.

many

5

Obfervations in EleElricity. 1 2 9

many purpofes to ufe a rubber with a handle of glais,
wax, See. with which the electricity of many fixed bo-
dies, gems that are fet in metals, &c. and other articles
that it would be improper to divide or remove, may be
determined. Such rubbers of different forms have been
conftruCted and fatisfaCtorily employed in a variety of
inftances by Mr. errington and Mr. cavallo, who
have extended their enquiries far beyond the limits at
which I defifted; their collection of animal, vegetable,
foflil, and artificial fubftances, added to my catalogue,
amounting to almoft one thoufand articles.

G O N C L U S I O N.

AT the conclufion of the fecond part of the pre-
ceding paper, in my remarks upon the electricity of
chocolate, I have obferved, that many and great difeo-
veries have been made in this age, refpeCting the aCtion,
influence, and effeCts of electricity ; but it is a queftion
that hath been frequently put to electricians, What is
electricity ? For my own part, I have generally chofen
(perhaps for want of a better anfwer) to reply by a fimilar
queftion, viz. What is air? or, what is water ? For, as thefe
are underitood to be fluids diftinCt from all others, and
Vol, LXVII. S diftinguifhed

1 30 Mr. henly’s Experiments and

diftinguifhed by the names they bear, fo have I ever con-
fidered eledfricity as a fluid Jut generis , and properly cha-
radterifed by the term eledfricity, eledfric fluid, or eledfric
matter; and have always avoided the term eledfric fire,
as conveying a confided idea of adfual inflammation,
burning, See. : but I now begin really to doubt, whether
another appellation might not be applied with greater
propriety ; whether eledfricity may not be confidered as a
pure, ethereal, elementary fire, inherent in all bodies, inti-
mately connedted or blended with an earthy or other bafe,
and apparently, though not adtually, remaining in it in a
quiefeent ftate, till roufed into adtion by fome proper ap-
plication, as motion, or rather fridfion, which may, and
probably does, colledt it in our experiments. (But can
motion convey inftantaneoufly that which is not material,
but only a quality, a property, an accident, or affection,
of matter, through fuch circuits as thofe of Dr. watson,
and produce fuch aftonifhing effedfs at the interruption
of thofe circuits? Befides,in Dr. franklin’s molt curious
and decifive experiment of charging the Leyden bottle
with its own eledfricity, the glafs undergoes no fridfion
whatfoever; but the eledfricity inherent in it is limply ex-
haufted from one of its furfaces, and forced round upon
the other by the eledfrical apparatus : the fame may be
aflerted of bodies prefented toward a condudf or negatively
5 eledfrifiedj

Obfervations in Electricity. 131

electrified, or to the infulated rubber of the eleCtrical
machine.) That it may be faid to reiide in vegetables, and
is extracted together with their oil ; that in fermentation,
effervefcence, and putrefaction, it flies off in the phlo*
giftic vapour thence arifing (fee note 1 . at the conclulion
of this paper); that in diftillation it is difengaged and
brought over in an ardent fpirit, in which it refides, re-
taining its original properties in a purer bafe ; that, fince by
the collifion of flint, fteel, See. aCtual fire is inftantaneoufly
produced (as in the inftance of the dry axle of a carriage,
which, by the friction of the nave againft it, foon takes
fire) fo by the friction of other bodies, which by long per-
feverance would produce the fame effeCt, this latent fire
may be firft excited, and its appearances, though unob-
ferved, be thofe we term eleCtrical. A wind-mill, when
it works under the break (as the millers term it when no
iron is concerned) foon catches fire (the mill-ftones,
when no corn is between them, produce the fame effeCt,
though the motion be the fame in both cafes) and many
a mill hath been confirmed by this means. The method
ufed by the Indians, of producing fire by the friClion of
two pieces of w'ood againft each other is well known;
and in all thefe cafes may not the firft effects of the
latent fire, thus roufed into aCtion, be the production of
thofe very appearances we call eleCtrical? See notes 2.
3. 4. 5. and 6.

132 Mr. henly’s 'Experiments and

This thought, I confefs, remained fo ftrongly im*
preffed upon my mind, that I requefted fome of my
friends, who had a better opportunity than myfelf,
to make the trial. For this purpofe fome pieces of
wood were baked in an oven, in order to expel the moif-
ture, and prepare them for the experiment. When they
were cooled, a fridtion was begun, which, as I expedted,
fioon produced electricity ; one piece of the wood being
excited pofitively, the other negatively, as I have fince
myfelf feveral times experienced. Had the fridtion been
continued, the produdtion of adtual fire might perhaps
'have been the confequence. May not, therefore, the
produdtion of adtual fire be the ultimum of electricity ?
or, in other words, eledtricity the firlt effedt of latent fire
thus roufed into adtion ; adtual fire, the fecond ; and in-
flammation and diffolution, its third and greateft effort?
like fermentation, producing firft, wine; fecondly, vine-
gar; laftly, putrefadtion. To give fome countenance to
this fuppofition, let fome of the effedts of eledtricity and
fire be placed in a comparative view. Firft, a fmall iron
wire, held in the flame of a candle till it acquires a white
heat, will frequently burft into little balls, flying off in
•all diredtions. The fame effedt is produced by a flint and
iteel ; and in a fuperior manner, by a ftrong charge of
eledtricity, or a flafh of lightning paffing through fuch
% 3. fmall

X)bfervations in TLleEiricity. 133

a fmall wire ; the balls then appearing, on examination,
to be little more than the fcorice of the metal. The effect
of electricity, lightning, and fire, in deftroying the power
of the artificial or natural magnets, is a circumftance that
hath been often remarked, and repeatedly publifhed.
The effects of electricity, in common with fire, on proof-
fpirit, gun-powder, pbofphorus , dry lint, and many other
fubftances, mult occur to every gentleman converfant in
thefe experiments ; indeed the parallel might be conti-
nued much further. But it may be afked, if this be
really the faCt, fhould not metals become eleCtrical by
friCtion ? I anfwer, they are readily excited, provided they
be firft properly infulated; (but if metal be rubbed
againft metal, the phlogifton or latent fire, if I may be
allowed the expreffion, is fo nearly proportioned in the
two metals, that the equilibrium is reftored as foon as
deftroyed, from the very nature of the bafe, which is the
moft perfeCt conductor we are acquainted with) to il-
luftrate this, let it be remembered, that though the
hydroftatic paradox may be readily explained, yet the
fluid muft be confined in a proper veffel ; and
though the weight, the fpring, and the compreffibi-
lity of the air, be eafily demonftrable, a fuitable appa-
ratus muft neceffarily be employed for each purpofe.

it

134 Mr. henly’s Experiments and

It is a queftion by no means decided, how the clouds be-
come eledtrified ? But if we fuppofe the electric matter to
be a pure, ethereal, elementary fire, refident in all bo-
dies; that the great procefs of vegetation is carried on
by means of this fubtile, adtive, volatile, and pervading
element ; that it is continually exhaling from all the ve-
getable tribe ; that as evaporation is a remarkable agent
in the cooling of heated fubftances, that is, a good con-
dudtor of their fire, as I am well allured it is of elcdtri-
city ; may we not conclude, that this is one great caufe
of the clouds becoming at times furcharged with this
fluid? The great effedt of eledlricity in promoting ve-
getation, hath been fully proved by Dr. de maimbray,
the abbe nollet, Mr. jallabert, and other gentle-
men, and was very remarkable in that year when the
fatal earthquake happened at Lifbon. Dr. stukeley’s
obfervations on the frequent appearances of fire-balls,
corufcations, and aurorce boreales , at this time (which I
well remember) deferve to be particularly noticed; and
it is generally remarked, that thunder-ftorms are pre-
ceded by a continuance of hot weather, and that a moderate
temperature immediately fucceeds the ftorm. The re-
marks and obfervations of the worthy Dr. hales on this
fubjedt feern alfo to merit peculiar attention. Further,
as the rays of the fun, concentrated by a powerful burn-

Obfervations in TLle&ricity. 135

ing mirror, will produce a fufion of metals, and inftantly
reduce a number of fubftances prefented to the focus to
a calx , as the fame effeCt is in many cafes produced
by a ftroke of lightning; and as the colours of the
electric and folar light are equally divilible by the prifm;
may not thefe alfo bear fome kind of relation to each
other ^? Upon the whole, is there not an high degree
of probability in the fuppofition, that light, fire, phlo-
gifton, and electricity, are only different modifications of
one and the fame principle? See notes 7. 8. and 9. A
fimilarity in feveral of the phenomena of electricity and
magnetifm hath been long fince pointed out by Dr.
price, from M. spinas ; and the effeCt of heat on both
admirably difplayed by Mr. canton. Of all the fub-
ftances I have yet examined, the moft difficult to excite,
I obferved to be a fine, fmooth, unarmed load-ftone, and
a piece of black lead ; thefe feemed to bid defiance to all
my rubbers: at length, however, with a piece of new
flannel they were both excited, in a very fm all degree,
negatively. In ffiort, I have not yet met with a Angle
article (on which the experiment could be tried) that I
could not, with one or other of my rubbers, make in

(l) Many other particulars might be adduced in this place; but they are pur-
pofely omitted, this paper being already extended far beyond the limits originally
intended by the author.

136 Mr. henly’s Experiments and

fome degree electrical. The laws by which all thefe
fluids are governed, and what conftitutes the precife dif-
ference between them, may yet, perhaps, by fome fortu-
nate philofopher, by a train of juft reflexion, and a fet of
happily contrived and well-conducted experiments, be
much farther elucidated. Laftly, I do not fpeak of thefe
things as fafts of which I am abfolutely convinced ; but
earneftly wifh to recommend them to the ferious con-
iideration of future enquirers. From what hath been
faid, however, I apprehend it will fcarcely be doubted,
that electricity, whatever it be (as I have often remarked)
is one of the greateft and moft important agents in the
operations of Nature; that the effects of lightning, there-
fore, are but as difcords in her harmony; and, though
fingly confidered, they may appear unpleafing notes,
yet perhaps may be neceffary to fill up and compleat her
grand and general chorus.

NOTES ON THE CONCLUSION.

i . I am juft informed by Mr. adams, that Mr. clarke*
an ingenious gentleman from Ireland, hath lately proved,
to the fatisfadtion of fome of the ableft chemifts there,
that the variety of airs produced by different gentlemen

in

Obfervations in Ele&ricity. 137

in their pneumatical refearches (that produced from the
calces of metals perhaps excepted) are only phlogiftic
vapours arifing from, and partaking of, the qualities of
the fubftances from which they are difengaged.

“ The vapour of fermentation is much more fubtle
“ than common air, it pafles through bodies which
“ would be impenetrable obftacles to the latter.

“ Mr. de smeth was not able to retain it by the aid
“ of lutes : a moiftened bladder, tied over the mouth of a
“ velfel which contained fome fermenting matter, was
“ not at all inflated during the height of fermentation.

“ Dr. Priestley has obferved, that the fixed air from
“ fermenting beer combines eafily with the vapour of
“ water, as alfo with the fmoke of rofin, fulphur, and
“ other electrical fubftances.

“ If it were permitted me to indulge in conjectures, I
“ fhould fay that fome experiments induce me to be-
“ lieve, that every elaftic fluid refults from the combina-
u tion of fome folid or fluid body with the inflammable
“ principle, or perhaps even with the matter of pure
“ fire; and that on this combination the ftate of elafti-
“ city depends.” See henry’s tranflation of M. Lavoi-
sier’s Effays, phyfical and chemical.

Mr. lane, in his curious and moft important experi-
ment of diffolving iron in water impregnated with fixed

Vol. LXVII. T air.

1-3-8 Mr. henly’s Experiments and

air, obferved, that after the water fo impregnated had
been paired through a clofe filtering paper, it was ren-
dered quite tranfparent, the iron being in perfect folu-
tion. This clear liquor he endeavoured to preferve in its
tranfparent ftate, by thing every means that then occur-
red to him to retain the elaftic vapour, but without fuc-
cefs, for in a few hours the tranfparency diminilltcd:
afterwards the liquor became opaque, and depofited the
iron that had been diflolved in it.

2. Several gentlemen have obferved, that in working
their electrical machines with great velocity, as heat was
produced by the friction, the electricity was proportiona-
bly leflened.

3. Mr. errington, a gentleman who often recreates
himfelf with mechanical operations, frequently ob-
ferved, that after he had been for fome time brilkly
working his drill, the firing of it became ftrongly elec-
trical.

4. Mr. ca vallo, who fometimes amufes himfelf with
the violin, having played a few fprightly airs, examined
at my requeft the hairs of the bow, and the firings of
the inftrument, and found by his electrometer that both

of them were electrical ; the former in a plus , the latter
Sin a minus ftate. In this cafe, the xofin contributes to
jc the

Obfervations in Electricity. 139

the electricity. Perhaps a tenor or bafs-viol might pro-
duce the effect in a greater degree.

5. Mr. cavallo likewife informs me, that taking two
pieces of broken China ware, he ftruck the edges of
them brifkly together, and produced fparks of fire, but
no electricity. He then rubbed the broader furfaces
gently together, and produced a ftrong e left rid ty ; pofi-
tive in one piece, negative in the other. This experi-
ment I have feveral times repeated to my entire fatif-
f aft ion.

6. 1 have myfelf obferved,that two glafs tubes, nibbed
brifkly together, produce a vivid purple light and ftrong
phofphoreal fmell, but no attraction or repulfion; but
two pieces of plate glafs, each two inches long and one
inch broad, warmed and rubbed gently againft each
other, produce electricity, negative in one piece, pofitive
in the other. Both glafs and amber I have alfo made
eleCtrical by blowing upon them (previoufly warmed)
with a pair of bellows.

7. Platina, in the pureft ftate to which it could be re-
duced by chemiftry, and on w'hich Dr. lewis informed
me that the ftrongeft fires he could raife had no further
effeCt, I have been able to fufe in a fmall degree, by a
ftrong charge of electricity. Phil. Tranf. vol, LXIV.
p. 416.

T *

8. Since

140 Mr. henly’s Experiments and

8. Since the learned and accurate F. beccaria pub-
lifhed the account of his curious experiment of revivi-
fying the calces of metals by electricity, it hath been re-
peated with perfect fuccefs by feveral other gentlemen.

9. With refpeCt to earthquakes, upon this liypo-
thelis Dr. stukeley’s and the rev. Mr. mitchel’s inge-
nious theory may both be near to truth, as the difference
between them will confifl more in words than in facts.
See a molt curious and aftonilhing effeCt of evaporation
produced by electricity in Dr. franklin’s Experiments
and Obfervations, firft edit. p. 415. Perhaps it may not
be improper to mention in this place the following
experiment, which I made long fince myfelf. A
pretty large wine-glafs being nearly filled with water,
two wires, terminated by fmall brafs balls, were hung
oppolite to each other upon the brim of the glafs, fo as
to let the balls defcend to about half the depth of the
water. The communication being then compleated by a
chain, a jar containing three fquare feet of coated fur-
face, was difcharged through it. The confequence was,
the Item of the glafs was broken in two places ; the bowl
was fhivered perhaps into a thoufand pieces, and fcat-
tered with the water in all directions : part of it flew into
my face, and fo much upon the apparatus, that I remem-
ber it put an end to my experiments for that time. I had
negleCted to cover the glafs, being defirous to fee the

effeCt

Obfervations in Electricity. 141

effect of the charge paffing through the water; not fuf-
peCting the danger of the electricity evaporating part of
it, and exploding with fuch violence as might have been
attended with very difagreeable confequences.

to. That water-fpouts are really occafioned by elec-
tricity I have long fufpeCted, from feveral circumftances ;
but Mr. george forster, F. R. s. in his curious remarks
and circumftantial defcription of one of thefe phenomena
(Voyage round the World, vol. I. p. 191.) feems to have
confirmed this matter beyond a doubt : the form of the
column, the hail-ftones which fell at the time, and the
flafh of lightning which appeared at the disjunction of
the tube, are, I apprehend, as complete proofs as can be
given, or as the cafe can admit or require.

1 1. Some gentlemen have fuppofed, that the eleCtric
matter is the caufe of the cohefion of the particles of bo-
dies. If the eleCtric matter be as I fufpeCt, and my expe-
riments and the foregoing notes feem to prove, a real ele-
mentary fire inherent in all bodies, that opinion may
probably be well-founded; and perhaps the foldering of
metals and the cementation of iron by fire may be confx-
dered as ftrong proofs, of the truth of their hypothefis.

1 a. Dr. Priestley obferves (Experiments and Obfer-
vations on Air, vol. I.p. 2 80.) That it is probable, that elec-

5 tric

t'4'i AS*. henly’s Experiments and

trie light comes from the electric matter itfelf; that this
being a modification of phlogifton, it is probable that
all light is a modification of phlogifton alfo; and that,
prior to his deductions from electrical phenomena, it
was pretty evident that light and phlogifton are the fame
thing in different forms or ftates. Dr. Priestley’s third
volume on the fame fubject was not publifhed till' the
laft fheet of my paper had- been compofed, and a proof
ftruck off. In the appendix to that volume I find fo cu-
rious an article in a letter from fignor volta to the DoCtor,
that I fliall take the liberty to tranfcribe a part of it, as a
very important addition ; viz: “ I fire inflammable air
“ by the Ample electric fpark, even when the electricity
“ is very moderate, which explains the ignes fatui , pro-
a vided they confift of inflammable air iffuing from
u marfliy ground by the help of the electricity of fogs
u and by falling-ftars, which are very probably thought
u to have an electrical origin.

“ I do not know whether you have ever tried the effeCt
u of the Bolognian phofphorus on air. It phlogifticates it
u in the higheft degree, and the diminution it occafions
u takes place very quickly, and is altogether furprifing ;
“ but for this purpofe the phofphorus rauft be good,
a and the weather not too cold.”

Since

Obfervations in Electricity. 1 43

Since the preceding papers were prefented to the
Royal Society, I have feen and heard of fuch a number
of curious remarks, obfervations, and difcoveries on light,
fire, phlogifton, and electricity, which tend to illuftrate
and confirm the opinions I have advanced, that I would,
beg leave to add, that, had I feen or known of feveral of
thofe excellent pieces in time, I thould certainly have
availed myfelf of fuch important labours, and have
fpoken of the fubjeCts above-mentioned with a . greater
degree of confidence. The authors I allude to are,
boerhaave on Fire; stahl on Phlogifton; Dr. Pem-
berton on Fire; Dr. higgins on Light; the celebrated
macquer, particularly in his Memoir on Phlogifton, in
.the abbe rozier’s Journal for Nov. 1776; a Memoir
by Mr. opoix on Phlogifton and Light; Mr. achard’s
Electrical Experiments on the Ice of diftilled Water,
frozen in a degree of cold exceeding what w.e ever expe-
rience in this country; with plates of which ice he not
only performed the Leyden experiment, but even ex-
cited it by friCtion like glafs (fee the Abbe rozier’sJoui-
nal for Nov. 1776); and laftly, M. koestlin’s curious
and fnoft valuable experiments on the influence of elec-
tricity, in the production and fupport of animal and ve-
getable life, particularly his difcovery that vegetation was
.actually retarded by electrifying his feeds negatively.

144

TOALDO de JEJlu

VIII. Extract of a Letter from John Strange, Efquire ,
His Majejly's Refident at Venice, to Sir John Pringle,
Bart. P. R. S. : with a Letter to Mr. Strange from the
Abbe Jofeph Toaldo, Profejfor in the Univerjity of
Padua, See. giving an Account of the Lides in the
Adriatic.

s i R,

Venice,

Nov. 19, 1776.

Read Jan. 23. and Feb. 6.T jsj- yom- faVour you exprefied a

j yy j *

defire of having fome account of the
the courfe of the tides here. As I have hitherto had but
little opportunity of making any conclufive obfervations
on that fubjedt, I applied to the Abbe toaldo, profeflor of
aftronomy and meteorology in the univerfity of Padua,
as the moil likely perfon to inform me. He obligingly
complied with my requefl: by the enclofed letter, which
I hope will be acceptable to you, and in fome meafure
fatisfadtory, being chiefly grounded on the obfervations
of a very accurate man here, fignor temanza, a cele-
brated architect and engineer. It is a pity but thofe ob-
fervations had been extended to -a longer term ; but as no
better are to be had at prefent, we mull be contented,
and hope for better hereafter. In the mean time it will
be a further fatisfaction to the learned profeflor, as well

as

Maris Veneti. 145

as to me, sir, fhould this communication prove alfo ac-
ceptable to the gentlemen of the Ro'/al Society, to whom
you may probably think proper to prefent it.

De reciproco /Eftu Maris Veneti. Ad Nobilem ac Doc-
tiffimum Joannem Strange , Sec. Epiftola Jofepbt
Foaldi, See.

QUyERENTI tibi, vir praeftantiflime, notitiam reci-
proci maris aeftus, in portu atque aeftuario Veneto obtf*
nentis, idque nomine Regiae Societatis veftrae, clariffimi-
que ejus praelidis D. johannis pringle, baronetti, liben-
tiflime, pro modo ac viribus, morera gero. Qui enim
negare poffem vel tibi, ftudiorum meorum fautori mu*
nifico, rerumque naturalium ferutatori eximio ? vel Re-
giae Societati, cujus acfta cognitionum humanarum re-
rum gazophylacium, in publicum ufum paratum, ex-
hibent? vel illuftri ejus prsefidi, ob feientiarum amo-
rem, in Europe tota tam celebrato ? vel ipfi heroicae na«
tioni Britannicae, pro rerum maritimarum praeftantia,
notitiam hanc praecipuo jure quafi petenti. Accedit,
quod res haec illuftrium autorum falfa traditione infedta
ac turbata eft, ficut mox docebo ; ut proinde interlit non
minus navigationis quam feientiae, veram ejus hiftoriam
Vol. LXVII. U memorise

146 TOALDO de JFjtl

memoriae ac litteris tradere. Conabor ergo praecipua ac
fu-mma rei capita breviter colligere. Ipfe quidem, Pa-
tavii degens, obfervationum ferieirqquod utinam licuiffet-,
inftituere non potui. Sed D. thomas temanza,
architedlus Yenetus clari nominis, diaria obfervationum
fuarum liberaliter mecum jamdiu communicavit ; ac,
licet femel in die obfervaverit, aquarum tamen motus ac
leges in aeftubus reciprocis fatis indicant : et autores alios
confului fatis idoneos; et ipfe identidem, Venetias digref-
fus, adnotare aliqua minime neglexi.

1. Primum igitur, illud etiam vulgo notum, Venetiia,
nempe in portu atque aeftuario Veneto, lingulis diebus,
bis aquarum acceffum live fluxum fieri, bifque receffum,
five refluxum ; lingulis vero menlibus lunaribus accelTu6
fieri majores per aliquot dies circa novam plenamque lu-
nam, quae Veneti appellant Punti d' acqua , quibus
tan turn, navigia majora in. portum compelli poifunt, val
ab eo educi.

2. Quod praecipue fcire intereft in hoc negotio eft
bora, qua aeftus menftruus ad culmen pervenit, quaque
portum pertranlire poifunt. Dubitare quis polTet prop-
ter jani planci, aliorumque fortalfe fcriptorum auto-
ritatem. plancus autem in Specimine reciproci ajiiis
in mari fupero , recufo Romae a. d. 1760, una cum
libro de conchis minus not is, baud hsefitanter tradit,

aeftum

Maris Veneti* 147

aeftura maris fequi curium potius fobs quam Lunae ; id eft,
aquas in quolibet accefiix maxime elatas deprehendi foie
meridianum obtinente, maxime vero depreftas foie ad
horizontem delato. Quid plancum aliofque in errorem
induxerit, pronunciare non aulim. Fortaffe caufa errons
fuit haec : aeftus majores contingunt circa novam plenam-
que Lunam : iftorum autem acceffuum hora parurn diftat,
ut mox oftendam, a Lunae tranfitu per meridianum; qui
iis diebus parum item diftat a tranfitu ipfius foils per eun-
dem circulum. Ecce ergo caufam erroris, quae certe impo-
fuit ipfi jano planco; qui, ut in praefatione libri fui
fatetur, ad portum Ariminenfem, et ad motum aquarum
obfervandum, non nifi tempore majorum aeftuum novi-
lunii ac plenilunii defcendere confueverat; circa quadra-
turas, aeftus modici funt, vixque fenfibiles, ut proinde
ipforum horam (turbatam etiam ob divulfionem folis ac
Lunae) obfervare non tarn fit promptum.

3. Quaecumque fuerit errandi caufa certe errarunt:
aeftus enim maxis, ut alibi, ita Venetiis, regitur a motu
Lunae. Dodtor vincentius miotti, obfervator diligens
ac navus, muriani, quae urbs milliari uno circiter a Ve-
netiis diftat feptentrionem verfus, anno 1766 et 67,
cum tabulas quafdam hue pertinentes conficere vellet,
per plures menfes aeftus accedentis ac pleni horam explo-
ravit, eamque, in fumma, comperit effe unam cum di-
ll 2 midi&

148 TOALDO de MJlu

midia ante tranfitum Lunae per meridianum fuper vel
fubter; vel potius decimam cum dimidia poft: dico po-
tius poft, quia credibile eft, aquam, quae ob aeftum in
Mediterraneum ex oceano influit, tan turn temporis infu-
mere ut ad extremas oras maris Adriatici perveniat. Ean-
dem horam colligo ex obfervationibus anno 1770 hor-
tatu meo habitis a laudato domino temanza (nam in
diariis praecedentibus hoc neglexerat): idem ipfe, cum
Yenetiis non femel effem, ftudiofe rem animadvertens at-
que explorans, verum effe deprehendi.

4. Hora ergo completi portus, quern ftatum etablijje-
ment du port appellant Galli, id eft aeftus altiflimi in fyzi-
giis praecipue, eft 1 o-^ poft Lunae tranfitum per meri-
dianum, fuperiorem, aut inferiorem, ita ut poftea defcen-
clere incipiant. Luna vero ad horizontem, five orienta-
lem five occidentalem, accedente, aquae humiles ac de-
preflae fun 5 ac turn demum crefcere incipiunt (aK

Ex

(a) Hujufmodi aquarum vices in portu Yeneto atque zeftuario, fi automate
©pus lit, traditas deprehendo in veteri codice manufcripto, rationem univerfam
Venetae navigations, tunc temporis continente, una cum ampliflimo portulano :
Gonfulendum olim praebuit fereniflimus Marcus foscarenus, Venetiarum
prius liiftoricus, deinde dux, vir dum viveret artium ac doftorum patronus muni-
fkentilSmus ; fcriptus eft codex lingua Veneta ve macula, eaque antiquiore*
Opinabatur fereniftimus dux, fuifle codicem petri lauretani, ftrenuiffimi,
ducis maritimi ex noftris, qui anno 1443 extrema nece Januenles apud rapal-
jluA debellavit. Is ergo codex inter praecepta navigandi ad rem noftram haec
babet, p. iji. Le atque di quefaparto (di Vinetia) ft xe quefe: quando la Luna

Maris Feneti. 1 49-

Ex hoc igitur fcriptore (in adnotatione) habemus vices
oeftus, cum diurni turn menftrui, in portu Yeneto. Quod
vero afferit, Luna in meridiano exiftente aquas fieri ple-
nas, latius eft fumendum ; ut intelligatur circa illam ho-
ram, id eft cum parva differentia unius ac climidice horse,
quam fuperius ftatuimus.

5, Confequitur, ut dicamus de magnitudine, five alti-
tudine aquarum in seftu. Circa fyzygias crefcunt aquse
plerumque tres pedes, vel tres cum dimidio fere, juxta

menfuram Venetam (pes autem Venetus ad Londinen-

0

xe in Ponente e Lev ante, fono iuiie le acque baffe ; e quando xe in Siroco e Maiftro r
fon mezze piene ; e quando 'la Lima xe in OJlro , le acque fon tutte piene j e quando
la Luna xe in Greco e Gar bin , le acque fon mezze vode .

Avifote y chele acque in ftde comenza zorni quattro della Luna infin a zorni 10; e
la xe a ponta ; e dai 1 1 infufo fono acque feconde infina a zorni 19 della Luna ; e da
zorni 19 infina zorni 2$fono le acque infede ; e dai 25 infina quattro della Luna fono
crefcenti . Avifote , che in una Luna fono do fede , e do feconde % e da J alii 9 Tacqua :
no xe move , zoe non a poJJ'o : quse hanc vim habent.

Regula aquarum in portu Yeneto eft haec: cum Luna eft in occafu vel
6: ortu, aquae funt prorfus humiles; cum refpicit plagas intermedias ventorum,.
u id eft cum mediam altitudinem afcendendo vel defcendendo occupat, aquae lunt-
4C femi-plenae, vel femi-vacuae. Denique cum. Luna eft in auftro* vel merL
<c diano, aquae funt ubique plenae.”

Haec de aeftu diurno, quod fequitur pertinet ad aeftus menftfuos.

Admoneo, aquas deficere incipere, vel aeftus-parvos fieri a quarta die Lunae
11 ufque ad decimam, ac turn incipiunt crefcere ; a die undecima ufque ad unde-
<c vicefimam fecundae funt,. vel' plenae; a decima nona ad viceftmam quintans
<c rurfus deficiunt, et deinde iterum crefcunt ufque ad quartam diem Lunae.
16 Admoneo intra Lunationem efte duas periodos, minorum, totidemque ma*
“ jorum aeftuum; a feptima autem die ad nonam (addendum etiam 22 ad 24)
€( aquas minime moveridd

3

fenx

TOALDO de JEftu

i'50

fern fefe habet ut 1 540 ad 1 35 1 i) raro ad quatuor, ra-
rius ad quinque, rariffime aut fere nnmquam ad fex,
auftro flante, mari irato ac procellofo.

6. Circa quaclraturas elatio aquarum multo minor eft,
aliquando vix trium pollicum; media, ut poftea often-
dam, eft pedis 1-’-.

7 . Indicata altitudo aeftus, maxima eft quae obfervetur
in toto Adriatico (cumulantur enim aquae intra Veneta
aeftuaria) : quo enim magis acceditur ad Mediterraneum,
minores continuo deprehenduntur aeftus, ita ut in Medi-
terraneo ipfo vix animadvertantur, exceptis euripis, aliis-
ve anguftis linubus.

8. Omitto quae funt communia aeftus maritimi in
omnibus maribus ; ex. gr. retardare fingulis diebus cum
Lutxae tranfitu per meridianum; ex duobus diurnis
aeftubus, alterum efie majorem et diuturniorem ; aeftus
maximos circa fyzygias fere nunquam contingere ipfo die
fvzigiae, fed vel antevertere, vel retardare, uno, duobus,
tribus, aliquando vel quatuor diebus.

9. Peculiaria quaedam adnotabo, ut illud cum jano
planco, aquas, initio acceflus, paulatim ac lente cref-
cere per tres aut quatuor horas, ut vix tres pollices horis
fingulis afcendant; poftea vehementer infurgere curfu
valde citato ; turn fieri, in culmine, quoddam quafi aquif-
titium , ut femihora quiefcere videantur, poftea velociter

defcendere,

j

Maris Veneti.

15 1

defcendere, et eafdem vices reciproce fubire ; unde patet
fpatium tranfeundi portus quatuor horis ad fummum in
majoribus asftubus circumfcribi.

10. Illud praecipue peculiare videtur huic mari noftro,
atque Adriatico toti, aeftus aequinoctiorum (Luna nova
vel plena) effe quidem magnos, fed non totius anni maxi-
mos ; fed maximos contingere circa folftitium hybernum.
Sciendum praeterea, finum Venetum pleniorem in genere
deprehen di, et aquas altiores elfe hyerne, quam aeftate;
animadverterat hoc janus ipfe plancus in laudatofpe-
cimine. Id oftendo duplici comparatione.

11. D. temanza obfervationes fuas inftituit ab
anno 1751 ad 1 7 5 5 . Ex hoc. quinquennali diario ex-
cerpfi aeftus medios fingulorum anni menfrum, quos in
duas clafles tribuo, fex hybernos, fexque aeftivos.

Menfes hybemi;

Menfes aeflivi.

r ,

.fliftus med.

in ped.

poll.

^Eftus med.

in ped,

/ poll.

Januarius,

2

L9

Aprilis,

I

9>9

Februarius,

o,3

Maius,

I

9s 5

Martius,

I

9>7

Junius,

I

n>7

October,

1 10,9

Julius,

I

9’9

November,

2

1,4

Auguftus,

I

7)9

December,

2 ■

2,6

September,

I

9,2

Med. diurnus,

2

o,S

Med. diurnus,

I

9)7

Patet

'1 5 2 TOALDO de JEJlu

Patet ex hac tabella, i°, Maximum aeftum totius anni,
Venetiis, contingere menfe Decembri, fcilicet circa fol-
ftitium hybernum ; et huic proximum effe aeftum menfis
Januarii. 2°, Minimum accidere menfe Augufto. 30,
Mediocrem effe menfibus oequinodtialibus Martio ac Sep-
tembri. 40, Inter fex menfes aeftivos, menfem folftitia-
lem Junium afferre prae cseteris aeftum magnum, et qui-
dem majorem aequinodtialibus ipfis. 50, Tandem men-
furam aeftuum aeftivorum valde fuperari a menfura
seftuum hybernorum.

12. D. temanza, in seftu adnotando, refpexit ad
terminum quendam medium, qui Venetiis ab aquarum
architedtis appellatur commune: intelligunt libellam
quandam mediam aquarum in lacuna. Quoad ergo
hanc libellam, five altitudinem mediam aquarum, adno-
tavit, quae menfura aeftus, tarn accedendo quam rece-
dendo, fuiffet fingulis diebus fupra vel fubter (accidit
enim aliquando ut aeftus ad earn altitudinem mediam mi-
nime pertingat). Contuli ego in fummas ex una parte
dies, quibus fuit fupra, ex alia, quibus fuit infra; idque
pro utraque menfium claffe.

^Eftus

Marls Vemtu

*53

iEftus menfibus hyb.

.®ftus menfibus eeft.

Dies

Dies

Dies

Dies

fupra med.

inf. med.

fupra med.

inf. (tied.

Januario, 105

51

Aprili,

82

68

Februario, 86

55

Maio,

85

80

Martio, 9 5

60

Junio,

73

77

Odlobri, 86

69

Julio,

64

9C

Novembri, 98

'5*

Augufto,

63

92

Decembri, 102

: 53

Septembri,

75

75

Summae, 572

340

Cl

442

483

Etiam ex hac tabella difcimus, seftus hybernis menfi-
bus fieri faepius elatiores, et finum nofirum pleniorem
effe, quam seftate.

13. Phaenomenon hoc ab alii caufii repetere nefcio,
quam a vicinia majorefolis, in fine Decembris ad peri-
gaeum delapfi ; nifi forte partem aliquam fibi vindicet in-
citatio major, eo temporis, in annuo telluris motu; ut ali-
quid fortaffe concedendum fit etiam ingeniofse galil^ei
theorise; ut dum aquae, vi attrahente corporum ccelef-
tium, attolluntur, patiantur fimul agitationem aliquam ob
inaequalem motum telluris.

Vol. LXVII, X

14. Porro

154 toaldo de JEftu

14. Porro fex illis menfibus hybernis contingunt
etiam procellae majores, atqvie inundationes urbis, in viis,
foris, ac locis minus eminentibus. Hoc loco quaeftionem
de majore altitudine aquarum, atque elata fuperficie mans
noftri minime movebo. 111am tradtarunt abunde cl.
manfredius in ASlis- Academia Bononenjis , torn. II.;

J ANUS PLANCUS, 1. C. ; CL. ALBERTUS FORTIS in Defci tp-

tmne infulce cherso atque osero. § xvi.; probaruntque,
aquas Ad'riatici revera altiores efle hifce annis quam fae-
culis praecedentibus. Nunc fane faepius acceffus aqua-
rum Venetiis pertingunt ad ea loca, ad quae nunquam-
antea perveniebant. Itaque necefle eft hodie attollere
Itrata viarum, ac praecipue cifternarum, quae aquas plu-
vias excipiunt, ne in magnis aeftubus ab aqufi falfa infici-
antur. Nec mirum fit, in lacuna urbem ambiente, exif-
tere tradtus non exiguos qui ab aeftu fere jam nunquam
regantur; folum enim lacunae elatum eft, atque extolli-
tur quotidie (licet magnis ac prorfus regiis fumptibus
omnes fiuvii a lacuna jamdiu depulli fuerint) ob fedir
menta aquarum, ac mar is alluviones^

Ad aeftus quod attinet, ex diario domini temanza, at-
que ex folutisquibufdam fchedis, erui menfuram mediam
aeftbs, annis hifce, prout in appolita tabella.

■ ) ", .. ** . ' f - "V* ' • - - -

4silus

Maris Feneti. *55,

JLftus medius annbrum.

^ Anai iEftus medius.

ped.- poH,

1751 1 11,82

175^ 1 10,53

v *753 *' °>35

1754 1 it, 88

1755 1 u>7*

1760 2 1, 11

1764 2 3,32

1765 2 o,S7

1766, Jun. 2 0,16

1769 2 1,13

Si quinque pofteriorum annorum obfervationes fideles
effent, ut priores (quod tamen ne ipfe quidem D. te-
manza omnino fpondet) manifefto evincerent, aeftum
maris Venetiis, annis hifce proximis, fummatim crefcere.
Quod credibiles reddit obfervationes ipfas eft id, quod
modo aiebam, aquas hoc tempore, quacunque de caufa,
infolitos acceffus facere, et inundare ea loca quae num-
quam antea attingebant. Satis de hac quaeftione.

X a

15. Modo,

TgO TOALDO de MJlu

75. Modo, data occaflone, non eft tacendus curfus
quidam generalis aquarum in toto Adriatico, qui eft extra
eontroverfiam, et cujus cognitio non inutilis efle poteft
ratione navigationis. Dete&us eft ergo curfus quidam,
feu motus aquas, qui ingreditur finura noftrum a dextri
parte, fitque fecundum littora Epiri, Dalmatia;, atque Hif-
triae; torquetur per finum TergeftinurnvrefLuitque ra-
dendo oras Porojulienfes, Venetas,Ravennates, reliquasin
ditione pontificia ac regni Ne^politani,egrediturque aparte
finifttra. Hinc nautse-noftri, cum a Corcyra atque Ionio,
Venetias petunt, legere confueverunt Epiri ac Dalmatiae
littora; cum contra Venetiis Corcyram ten'dunt, navigare
ftudent fecundum1 littora pontificia ac Neapolitana; con-
tenduntque, eodem vento, ac ceteris paribus, hac via
multo plus itineris confici, quam fecus.

16. Circularem hunc aquarum in Adriatico fluxum
detexit primus, ni fallor, inter fciptores geminlanus

siontanarius, profefior Patavinus, anno 1681, dum

-

f juffu publico lacunam vifitaret. Rem litteris tradidit, ut
videre eft in ejus commentario Italico, cui titulus yIlMare
Adrdatico , e Jua corrente efaminata, in Colledione Autorum
qulde. Aquis currentibus fcripferunt^ vol, iv. recentis edi-
tionis Florentinse, 1768. Ex progreffu corporum aquas
innatantium (puta infularum quarumdam ex putrefadis
radicibus arundinum paluftrium concretarum, quarum
3 plurimae

Maris Veneti. 157

plurimae concrefcunt in paludibus Adrianis) arguit mon-
tanarius, curfum hunc aquae in Adriatico conficere
milliaria tria vel quatuor intra horas xxiiiL At janus
plancus, qui eundem hunc curfum. et agnovit et obfer-
vatione confirmavit, ut videre eft libro laudato, putat, ex
progreffu cadaverum fluitantium, quae aliquando curfu
hoc deferuntur ad littora inferiora Ariminenfia, putat,
inquam, effe adhuc velociorem..

17. Opinatur porro ingeniofe monta-n arius, fluxum
hunc in Adriatico derivationem effe curfus generalis in
Mediterraneo.. Tefte enim fournerio in Hydrography
oceani aquae, per fretum Gaditanum, Mediterraneum in-
grediuntur a parte dexter^ vel Africae; hujus littora ra-
dunt ufque ad ^Egyptum et Syriam; inde convertuntur
per oras Afiae, fortafle circumeunt JEgeum, legunt oras
Peloponnefi, ingrediuntur in Adriaticum eo modo quo
diximus, atque inde exeundo, peragrant littora infera
Italise, Ligurise, Galliae, Hifpaniae, ac tandem per fretum
Gaditanum, a pane finiftra, in oceanum exonerantur ac
revertuntur,

18. Haec habebam quae de motu aquarum in finu Ve-
neto proferrem. Non ingratum, opinor, erit accipere
conclufa qrjaedam ex obfervationibus ad aeftus maritimi
theoriam fttnul pertinentia, ac doftrinam newtonianaM
mirifice illuftrantia..

19. Conferre

'r*5$ toaldo de JEJlu

19. Conferre primum placuit seftus fyzigiarum cum
aeftibus quadraturarum, edudtis numeris mediis ceftuum
quinque dierum circa lingulas, elicitifque mediis medio-
rum fingulis illis quinque annis exa<ftis. Et quia Luna,
cum fita eft in perigaeo, ob viciniam majorem, attollere
magis debet aquas, quam in apogaeo, hi quoque numeri
additi funt : ecce tabellam.

iEftus medius ratione fitus Lunae.

In Novil.

Pr. Quad.

Plenil.

Ult.Quad.

Perigaeo.

Apogaeo,

I75i

2

4,5

1

5,4

2

3>i

1

6,4

2

hS

1 IO,°

i752

2

3>6

I

4,2

2

5,8

1

3,5

1

8,5

1 7>l

1753

2

7,6 .

1

5,9

2

5,8

1

4,2

2

4,i

2 0,6

1754

2

4,2

I

V3

2

3,8

1

4,i

2

5,5

2 1,5

1755

2

o,6

Ji

5,8

2

4,0

1

4,i

2

°,9

i 10,8

Med. 5 ann'.

2

4,1

1

4,i

2

4,5

1

4,5

2

1,2

1 10,1^

Patet, x°, aeftus fizigiarum medios valde excedere
seftus quadraturarum ; ut ft numeri utriufque fyzigiae, et
quadrature, componantur, seftus medius fyzigiarum fit
pollicum 28,3, quadraturarum 16, 3, in ratione fere 7 : 4.
a°, Animadverti poteft, seftum plenilunii plerumque elfe
paulo majorem aeftu novilunii, ut quodammodo magis
'videatur retrahi a luminaribus mafia globi terreftris,
4 quam

Marts Veneti.

1 59

quam aquae oceani, utroque in fitu, in novilunio quidem
fecundum elationem aquarum; in plenilunio vero lumi-
naribus divulfis, et in oppofita trahentibus, contra nifum
aquarum. Hinc enim fequitur, aeftum plenilunii ali-
quantulo elatiorem efle debere. Utcumque lit, certe 3®
aeftus Lunae perigeae, prout ratio poftulat, fuperat aeftum.
Lunae apogeae, in ratione 25,2 ad 22, vel circiter 1 ad 7 ;
quae eft proportio apparentis diametri Lunaris a perigaeo
in apogaeum.

20. Porro juxta theoriam phyficam, ratione fitus Lunae
et locorum terreftrium, ft caetera lint paria, maximi fieri
deberent aeftus, fpedtata tellure tota, cum Luna imminet
lineae aequinodtiali ; ratione vero loci peculiaris, aquae
magis attolli debent, cum Luna, declinatione, cognominl
latitudini geographicae ejufdem loci potitur; minime in
oppofita. Confeci ergo fummas aeftuum, pro diebus qui-
bus Luna morata eft (quinquennio hoc) in finguiis zo-
diaci fignis: ex his edvuStos numeros medios expofui in. .
adjedta tabella.

Tatefta

Tabula aeftus maris, fecundum xn. figna zodiaci, quatenus refertur ad Lunam»

i6o toaldo de MJltt

Optandum fane eflet, praefto
efle obfervationes plurium an*
norum quam quinque, ut in-*
tegroe revolutionis nodorum
Lunae, vel faltem apfidum ; et
bis fuifle pera<ftas diebus fm-
gulis, pro utroque acceflii ac
receflu aeftus. Interim tabula
haec oftendit: i°f Minimum
aeftum in mari noftro contin-
gere, prout jubet theoria, Luni
lignum Capricorni obeunte.
a0, Summatim fignorum auf-
tralium aeftus minores efle,
quam borealium; 3*, aeftum
Cancri, et auftralium omnium
(except^ libra) et borealium
afcendentium efle maximum;
fed 40, fuperari ab aeftu trium
fignorum defcendentium Leo-
nis, Virginis, ac Librae, quod
videtur principiis noftris re-
pugnare, fed res facile expli-
catur. Primum enim a<5lio
Lunae in oceanum generatim

maxima

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Maris Veneti. i6x

maxima effe debet cum verfatur prope aequatorem ; de-
inde in fignis defcendentibus, prope aequinodiium librae,
colledtio quaedam cumulufque aquarum fieri debet, ex
praecedente impreffione, in fignis borealibus (ratione cli-
matis noftri) et ob vim inertiae in aquis ipfis. Quare
aeftus circa Virginem ac Libram debent effe generatim
maximi, prout funt in tabula.

21. 5% Adnotavi pro fingulis annis locum perigaei
Lunaris; ex quo apparet, perigaeum ipfum, motu fuo,
altiores aeftus fecum quafi trahere a figno in lignum, a
Tauro ac Geminis, 1751; ad Cancrum, 1752; ad Leo-
nem, 1753; ad Virginem ac .Libram,. 1754; at^ Scorpio-
nem, 1755. Praeterea anno 1753, quo anno perigaeum
proximum erat vertici noftro, aeftum annuum videmus
fuiffe maximum: omnia juxta theoriam.

22. Similes vices, hortante cl. lambertq, academico
Berolinenfi, ex obfervationibus quadraginta an norum cl.
poleni, R. s. s. quae funt apud me, deprehendi in motu
barometri. Sed de hoc egi in Specimine meo Meteorolo-
gico , et in opufculo, cui titulus Nova 7" abula Barometric
agamque fortaffe alias.

Interim opto, hafce qualefcumque notitias meas de
seftu maris Veneti, a Societate Regia non inutiles judi-
cari. Vale, vir praeftantiffime, ac favere perge addic-
tiffimo cultori tuo.

Dabam Patavii, 9 calendas Nov. 1776.

Vol. LX VII. Y

[ 162 3

X. A Letter from Mr. Peter Wargentin, F. R. S. Secre-
tary tQ the Royal Academy of Sciences at Stockholm, to
the Rev. Nevil Mafkelyne, B. D. F. R. S. and AJlro-
nomer Royal ; concerning the Difference of Longitude of
the Royal Obfervatories at Paris and Greenwich, refult-
ing from the Eclipfes of Jupiter’s firfl Satellites , obferved
during the lajl Fen Tears : to which is added , a Compa-
rative Table of the correfponding Obfervations of the
Firjl Satellite , made in the principal Obfervatories.

Vir plurimum reverende atque celeberrime,

Read Feb. 6, TPfcETIISTI in utrifque litteris tuis, u ve-
1777. wf

“ lim obfervationes fatellitum Jovis,
“ praecipue primi, a te grenovici, et a Cl. d. messier
“ parisiis, ab anno 1765 habitas, inter fe conferre, ut
“ inde eliciatur vera differentia utriufque meridiani:”
huic defiderio tuo lubens fatisfacio.

Tuis obfervationibus primi fatellitis non nil! 1 7 cor-
refpondentes messierii obtigerunt; quarum 8 fuerunt

inimerliones

Mr. wargentin’s Letter , 8cc. 163

imraerfiones, et 9 emerfiones. Ipfas obfervationes, inter
fe et cum multis aliis, atque cum poftrema editione mea-
rum tabularum (ea fcilicet, quam alteri editioni aftrono-
mise fuae inferuit Cl. delalandius) comparatas, videas
in fubjundta appendice, in qua Paris Cl. indicat obfer-
vationes messierii, in palatio Clugny; Paris O. autem,
in ipfo obfervatorio regio habitas. Hie fufneiat attulilTe
refultantes a quovis immerfionum et emerlionum cor-
refpondentium pari, meridianorum differentias.

Ex immerfionibus correfp.

Ex emerfionibus

#

1 765, Dec. 24. prodit difF, merid.

r n

8 35

1767, Apr. 9. ditjr. rnerid.

9 99

9 49

1769, Apr. 12.

9 3i

1768, Mai. 11.

9 29

Apr. 28.

9 58

Jun. 3.

9 S3

1772, Jun. 9.

9 59

Jun. 19.

10 16

Jul. 11.

9 -23

1769, Mai. 16.

9 26

1774, Sept. 26.

9 49

Jun. 8.

9 45

oa. 3.

9 26

1770, Aug. 5.

9 11

oa. 21.

9 47

1 773’ oa- 25-

9 23

Media ex imm. merid. differ.

9 39

Nov. 1.

9 39

Med. exclufa prima.

9 4*

Media ex emerfionibus,

9 37

Med. exclufa quarts,

9 32

Tu, vir celeberrime, fere Temper ufus es telefcopio new-
toniano 6 pedum: cl. messier plerumque Grego-
rian 0 2j pedum, vel acromatico 2>\ peclum, vel aliis

Y 3 aequales

164 Mr. wargentin’s Letter on

sequalis fere potential, quorum neutrum non plufquam
centies objedtorum diametros amplificat. /Equales fere
inventse per immerfiones et emerfiones correfpondentes
meridianorum differentiae, fatis indicare videntur, ferme
aequalis quoque praeflantiae fuiffe utriufque obfervatoris
inftrumenta. Alium et certiorem mcdum ea compa-
randi nefcio, praecipue cum tu fa) nullibi indicaveris po-
tentiam tui newtoniani : nam longitudo folaambiguum
eft argumentum.

Per medium itaque dedudtum ex 7 paribus immer-
fionum et 8 emerlionum, invenitur differentia inter
meridianum grenovicensem et. obfervatorium cl.
messier, 9' 38"; vel feclufis uno immerfionum uno
emerfionum pari, utpote quae nimium a reliquis re-
cedentem, indicant meridianorum differentiam, 9' 37";
adeoque foret inter obfervatorium grenovicense et
regium Parifinum 9' 35", hoc eft 19 fecundis major
quam hucufque putavimus. Obftupui videns tantam
incertitudinem circa veram meridianorum differen-
tiam inter duo praecipua orbis obfervatoria, eaque vici-
na, in quibus ingens obfervationum numerus, annis

(a) The diameter of the aperture of this telefcope is 9 4 inches, as is men-
tioned in the preface to my Greenwich Obfervations, from 1765 to 1774? pub-
lifhed this year. n. m.

plufquam

the Difference of Longitude , &c. 165

plufquam 100, habitus eft. Quid turn de aliis fentien-
dum ? Ab uni parte vix perfuadere mihi pofliim, tantum
errorem tamdiu potuifle latere ; vel comparatas obferva-
tiones eclipfium Solis, Lunas, occultationum fixarum, 8cc.
tarn multum potuifle fallere : ab altera, egregius 1 5 bo-
11 arum obfervationum confenfus, haud facile fortuitus,
fidem quandam mereri videbatur; nifi obfervationes fa-
tellitum, ad determinandas accurate longitudinum dif-
ferentias, prorfus inepats judicaveris.

Ad tollendum hoc dubium, confului obfervationes
primi fatellitis, eodem tempore, in ipfis obfervatoriis re-
giis, quarum non nifi duse funt immerfiones, fed novem
emerfiones.

Immerf.

x7^7j Jan- *2. diff. merid.

/

9

n

l6

1772, Jul. II.

9

4

Medium ex hifce duabus*

9

10

Emerf.

i n

i7665Apr.il. 955

1767, Mart. 22. 9 36

Apr. 16. 9 32

Apr. 30. 9 5

Mai. 9. 9 47

Jun. 1. 10 28

Jun, 3. 94

1769, Jun. 8. 10 13

j773> 5* 9 37

9 42
9 32

4

Medium ex omnibus,

exclulis 6a et 8^,

Harum

Mr. wargentin’s Letter on

166

Harum longe minor eft confenfus : ft tamen fumatur
medium, erit id 9' 26 " vel 9' 21".

Ulterius comparavi feptem paria immerfionum et 4
emerfionum, annis 1761 — 1764, in utroque obferva-
torio captarum: medium ex prioribus reperi 9' 26", ex
pofterioribus 9' 30". Etne quid deeffet, excufli quoque
obfervationes ante annum 1700 fadtas^ inter quas 12
immerfiones correfpondentes indicant, per medium, dil-
ferentiam meridianorum 9' 57"; fed 7 emerfiones tan-

tummodo 8' 45": ex lioc utroque medio refultat novum
9' 21".

Porro tentavi, mediantibus meis obfervationibus, quo-
rum multas tuis funt correfpondentes, multce Parifienfi-
bus, quaefitam ftabilire meridianorum differentiam. Ego
Temper ufus fum tubo achromatico dollondiano 10
pedum, cum oculari, quod objedta 90 amplificat, et valde
xliftindla reddit.

Immerf,

the 'Difference of Longitude, Zee

167

Immerf. correfp.

1765, Dec. 1.

h r it

1 12 34

(b) 1766, G&. IO,

1 12 14

1768, Apr. 2.

1 13 10

1769, Mart. 29.

1 11 47

1774, Sept. 12.

1 12 32

O £. 3.

1 12 12

i775>oa- i.

1 12 59

Medium,

1 12 14

Sed tua obfervatio,

die 10 Odl. 1766,

vix re£te fe- habere poceft, Ilia

negletta, manet

ex reliquis me-

dium,

1 12 32

Emerf,

h / n

1766, Mart. 5.

1

12

ii

1767, Jun. 1.

1

12

7

1768, Jun. 12.

1

12

16

1769, Mai. 16.

1

1 1

32

Jun. 8.

1

12

*9

1771, Aug. 17.

1

12

0

Sept. 25.

1

12

8

1772, Sept. 27.

1

12

H

1773, o&. 25.

1

id

3*

1774, Dec. 29.

1

id

23

W5> Feb. 22.

1

12

16

Dec. 27.

1

12

1 1

Medium ex his.

1

12

1 1

Obfervationes emerfionum fatis pulchre confpirant:
medium ex immerfionibus et emerfionibus innuit dif-
ferentiam meridianorum Grenovicenfis et Stockholm enfis
ih 1 a' ai". Perfuafus fum earn i]l 12' ao" vix eife mi-
norem. Per medium ex 8 obfervationibus correfponden-

JL

(b ) There was a miftake of twelve hours in fetting down this obfervation at
Greenwich, by the clock keeping fidereal time, which made an error of i' 49"
in the redu&ion to apparent time. The correct time of imrnerlion is i6h 59' 3 1",
which happens to agree exactly with Mr. waecentin’s calculation, and the
difference of longitude of Stockholm and Greenwich by this obfervation is
ih 12' 14" inftead of ih 10' 25 fet down above; and the mean difference frem
all the f«ven correfponding immerfions is ih 12' 30'’'. See the errata- printed
with my Obfervations. n. m.

tibuSj .

1 6 8 Mr. wargentin’s Letter on

tibus, quae habitge funt annis 1761 — 1764, emergit

,ih 1 2' 25".

Quod attinet difFerentiam meridianorum obfervatorii
Parifienfis et Stockholmenfis, ex 8 immerlionibus et 13
emerfionibus primi fatellitis fimul in utroque notatisante
annum 1760, concluii earn, per medium, effe i'1 2' 51".
Sed 7 immerfiones et 1 2 emerfiones correfpondentes,
fadtae poft annum 1760, earn paulo minorem, fcilicet
2' 47", reddunt. Nihilominus, cum per obfervationes
quarundam eclipfium folarium evincere conati funt cele-
berrimi viri, pingre, du sejours, et lexell, earn pau-
cis fecundis effe majorem, non refragabor affumere earn
ih 2' 5 5", qua fubtradta ab inventa differentia obfervato-
rorum Grenovicenfis et Stockholmenfis ih 12' 21", reftat
differentia Grenovicenfis et Parifienfis 9' 26".

Omnes itaque liae difquifitiones teftantur, differentiam
quaefitam majorem effe 9' 1 6" quantam hucufque exifti-
mavimus; et ni fallor ad g' 2 5" proxime accedere; de qua
re tamen totum ad te, vir celeberrime, defero judicium.

Interim hinc apparet, arduum fane effe, praecifas me-
ridianorum differentias, ope obfervationum fatellitum
Jo vis, deter min are. Fixarum occultationes a Luna, probe
obfervatae et excuffae, certiorem line dubio fuppeditant
methodum.

Valde

the Difference of Longitude, &c. 169

Valde miror, quare illi, qui bonum telefcopium vel
tubum habent, eo non Temper in obfervandis fatellitibus
utantur, fed jam hoc, jam alio, forte minus praeftanti.
Obfervationes multum dubias, vel aeris vitio vel aliam ob
cauffam, ne quidem in diarium refero, nam nulla obfer-
vatio praeftat malae. Quantum malae obfervationes, pro
bonis venditatse, me confuderint et torferint, dicere non
polfum.

Quartus, die 8 Februarii hujus anni, eclipfin tantrum
partialem palfus eft. Magnum tuse in me amicitiae fig-
num id interpretabor, fi, quovis anno finito, tuas mecum
communicare velis obfervationes fatellitum; nam his,
etiam fenex, deledtor. Hanc quoque provinciam, exa-
minandi motus fatellitum, mihi, quail tacito confenfu, tie-
tulifle videntur collegae aftronomi. Ceterum ingruens
aetas, nimiae occupationes quas fecretarii munus in-
jungit, defedtus inftrumentorum (nam murali nondum
inftrudlus fum, quidquid dicat Celeb, lalandius) ut
taceam modicas ingenii vires, vetant quo minus aliquid
tua vel aliorum exfpedtatione dignum praeftare poffim (b>.
Frigus hac hieme in Suecia continuum fuit, a 28 Dec. ad
5 Februarii; fed neutiquam, pro ratione climatis, praeter

(c) Notwithftanding the author’s modefty, the aftronomsrs of Europe know
him better, and lament with him that he is not fo well provided with capital
inftruments as he willies and deferves to be. n. m.

Vol. LXVII.

Z

modum,

170 Mr. wargentin’s Letter on

modum, rigidum : plerumque 5 vel 10 gradum thermo-
metri reaumuriani. Diebus tantum 26 et 27 Januarii,
ad 17 et 18 gradus exafperatum fuit. Minor quoque
nivis copia apvtd nos fuit, quam pro folito. Miror itaque
intenfitatem frigoris, eodem tempore, apud exteros.

Dab. Stockholm i x, die 19 Mart. 1776.

Obfervationes primi fatellitis Jovis in pnecipuis obferva
toriis habitae, inter fe et cum tabulis comparatae.

Ann. Temp. Obfervationis,

Calculus.

Diff. Calc. Obfervatorium.

M. D.

h /

//

h ' "

/

u

1765. Sept. 21.

16 53

22

Im.

16 S3 15

0

7 — Stockholm.

Oft. 23.

13 31

6

-

13 31 30

0

24 -f Tyrnav.

Dec. 1.

IO 40

1 1

-

10 40 48

0

37 + Greenwich.

11 33

25

-

I1 33 33

0

8 Lund.

11 50

56

-

11 51 0

0

4 + Tyrnav.

11 52

45

-

11 52 59

0

14 4- Stockholm.

8.

12 31

34

-

12 31 25

0

9 — Green vv.

J5-

14 22

3

-

14 21 40

0

23 — Greemv.

*5 31

40

-

15 31 52

0

12 4- Tyrnav.

17-

10 1

-

10 1 26

0

1 1 4“ Stockh.

22.

16 12

l9

-

16 11 47

0

32 — Greenvv.

24.

io 39

27

-

10 39 19

0

8 — Greenvv.

10 48

2

-

10 48 37

0

33 4- Paris Cl. d .

11 49

6

-

11 49 31

0

25 -f- Tyrnav.

1 766. Jan. 2.

8 8

44

-

8 9 24

0

40 4" Stockh. d.

9*

9 40

16

9 4° 37

0

21 4“ Lund.

16.

11 50

51

-

11 51 17

0

26 + Stockh.

23*

13 40

32

-

13 41 28

0

36 4" Upfala d.

25-

8 8

3°

Mr

8 9 30

1

0 + Upfala d.

Obfervatione

s

the Difference of Longitude , Bcc. 1 7 1

Obfervationes comparatas primi fatellitis Jovis.

Ann. Temp. Obfervationis.

Calculus.

Diff. Calc, Obfervatoriu

M. D.

h

rt

h

t tr

f

//

1766. Jan. 25.

8

10

39

Im.

8

1 1 10

0

31 +

Stockholm.

Febr. 15.

16

6

31

Em.

16

6 14

0

i7 —

Upfala.

24-

12

31

20

-

12

31 48

0

28 +

Stockholm.

Mart. 5.

7

43

55

-

7

44 25

0

3° +

Greenw.

8

55

4

-

8

54 56

0

8 —

Upfala.

8

56

6

-

8

56 36

0

3° +

Stockh.

9

45

36

-

9

45 39

0

3 +

Peterfb.

10.

15

20

27

-

i5

20 58

0

3i +

Paris. Cl.

20

35

-

*5

20 56

0

21 +

Paris. O.

12.

9

49

54

-

9

50 3

0

9 +

Paris. O.

9

49

56

-

9

50 5

0

9 +

Paris. Cl.

10

33

12

-

10

33 32

0

20 -j-

Lund.

10

5°

41

-

10

5° 59

0

1 8 4*

Tyrnav.

10

50 53

-

10

51 18

0

25 +

Upfala,

10

52

T3

10

52 58

0 45 +

Stockh.

11

4i

56

-

1 1

42 I

0

5 +

Peterfb.

*9-

12

3°

*5

-

12

3° 8

0

7 —

Lund.

12

47

52

-

12

47 54

0

2 +

Upfal. d .

21.

7

16

3^

-

7

16 48

0

12 +

Tyrnav.

26.

13

33

36

-

13

34 43

0

37 +

Greenw.

28.

8

12

33

-

8

12 44

0

11 +

Paris, CL

9

8

56

-

9

8 53

0

3 ““

Wien,

Apr. 4.

1 1

10

7

-

1 1

10 48

0

41 +

Upfala.

11

10

21

-

1 1

10 29

0

8 +

T yrnav.

11

12

4

-

1 1

12 28

0

24 +

Stockh.

11.

11

56

3°

-

1 1

56 59

0

29 +

Greenw.

12

6

25

-

12

6 *5

0

10 —

Paris. O.

*3

2

32

-

13

2 26

0

6

Wien.

20.

8

31

18

-

8

31 49

0

31 +

Paris. Cl.

8

31

37

-

8

3* 47

0

10 +

Paris O.

9

27

56

-

9

27 58

0

2 +

Wien.

9

32

3°

~

9

32 43

0

13 +

Tyrnav.

Z

3

Obfervatio

172

Mr. wargentin’s Letter on

Obfervation.es comparatae primi fatellitis Jovis.

Anni. Temp. Obfervationis. Calculus. Diff. Calc. Obfervatorium.

M. D.

h in

h • "

/ //

1766. Apr. 20.

9 34 24

Em.

9 34 42

0 18 -j- Stockholm-

10 23 9

-

10 23 45

0 36 4- Peterfb.

27-

11 30 20

-

11 30 42

0 22 + Stockh.

May 13.

9 47 45

-

9 48 2

0 17 4- Tyrnav.

9 49 24

-

9 50 1

0 37 4“ Stockholm^

20.

11 25 12

-

11 25 4

0 8 — Lund.

Jun. 5.

9 54 1

-

9 53 44

017 — Wien.

9 58 39

-

9 58 29

0 10 — Tyrnaw

Oft. 10. (d) 17 I 20

Im.

16 59 31

1 49 — Greenw.

18 11 45

-

18 11 42

0 3 — Stockh.

26.

16 27 59

-

16 28 13

0 14 4- Tyrnav.

Nov. 2.

17 21 9

-

17 21 18

0 9 4" Paris. Cl.

18 22 20

-

18 22 12

0 8 — Tyrnav.

18 24 19

-

18 24 11

0 8 — Stockholm.

18.

16 36 1

-

35 51

0 10 — Tyrnav.

25-

18 9 27

-

18 10 1

0 34 4* Lund, d.

18 29 37

-

18 29 27

0 10 — Stockh.

Dec. 4.

13 44 46

-

*3 45. 9

0 23 + Paris. O.

13 44 53

-

13 45

018+ Paris. Cl.

18.

17 25 29

-

17 25 29

0 0 Paris. O.

1767. Jan. 3.

15 24 1

-

*5 23 57

0 4 — Greenw.

12.

11 41 41

-

11 42 15

0 34 + Greenw.

” 5° 57

-

11 51 31

0 34 4- Paris. O.

26.

15 34 34

-

15 34 40

0 6 4- Paris. Cl.

Feb. 2.

17 26 54

-

17 27 20

0 26 4- Paris. Obf.

17 27 13

-

17 27 22

0 94- Paris. Cl.

*3-

9 18 13

-

9 18 44

0 31 4“ Tyrnav.

20.

11 14 44

-

11 i5 14

0 3° 4“ Stockholm.

27-

11 57 7

11 58 6

0 59 + Greenw. d .

Mart. 17.

8 12 16

Em.

8 11 32

0 44 — Tyrnav.

22.

14 28 48

-

14 28 40

0 8 — Greenw.

\d) This obfervation rightly reduced to apparent time is i6h 59' 31", which
happens to agree exactly with Mr. wargentin’s calculation. N. m.

Obfervationes

the Difference of Longitude , Sec. 173

Obfervationes comparatce primi fatellitis Jovis.

Ann. T emp. Obfervationis.

M.

D.

h

/

it

1767, ,Mar.

22.

14

38

24

Em

31*

12

4

36

-

12

4

54

-

12

6

28

-

Apr.

7-

14

1

46

-

14

2

59

-

9-

7

20

1

—

7

29

50

-

14.

14

47

52

-

16.

9

16

13

-

9

25

45

-

23*

12

23

22

-

12

23

42

-

12

24

3°

-

3P-

r3

9

10

-

J3

18

*5

Mai.

9*

9

32

26

9

42

*3

-

10

43

7

16.

12

38

6

-

30*

10

*5

32

—

Jun.

1.

9

44

1

-

9

54

29

—

IQ

56

8

-

8.

1 1

37

42

-

1 1

46

46

—

Nov.

2J.

I9

10

24

Im.

Dec.

23-

14

43

47

-

30r

1.6

24

27

1768. Jan.

22.

16

24

*3

—

31*

12

53

1 1

-

>

12

53

22

Calculus.

Diff. Calc. Obfervatorium,

h / "

r n

*4 37 56

0 28 — Paris. O.

12 5 0

0 24 4 Upfala.

12 4 41

0 13 — Tyrnav.

12 6 40

0 12 4 Stockh.

14 I 35

on—* Upfala.

H 3 i5

0 16 + Stockh.

7 2Q 13

0 12 + Greenw.

7 29 31

0 19 — • Paris. Cl.

14 47 36

0 16 — - Greenw,

9 16 43

0 30 -4* Greenw.

9 2 5 59

0 14 4 Paris. 0«

12 23 10

0 12 — Tyrnav.

12 23 29

0 13 — Upfala,

12 25- 9

o 39 -f- Stockh.

13 8 47

0 23 — ■ Greenw.

J3 18 3

0 12 ’ — Paris. O.

9 32 58

o 32 4" Greenw,

9 42 H

0 1 4" Paris. O.

10 43 10

0 3 4- Tyrnav.

12 37 54

o 12 — ■ Tyrnav.

10 15 17

0 15 — Philadelphia,.

9 44 20

0 19 4“ Greenw.

9 53 36

0 53 — Paris. O, d*

10 56 31

0 23 + Stockh,

11 37 49

0 7 4 Greenw.

ii47 5

019+ Paris. 00

19 i° 35

0 11 4“ Lund.

14 43 45

0 2 — Paris. CL

l6 24 l6

on — Greenw.

16 23.37

o 36 — Greenw,

12 52 56

0 15 — Paris. O,

12 52.58

0 24 — Paris. Cl.

Obfervationes

174

Mr. wargkntik’s Letter on

Obfervationes comparatae primi fatellitis Jovis.

Ann. Temp. Obfervationis.

Calculus.

DiflT. Calc. Obfervatorrum,

M. D.

h / /'

h ' ft

/

it

1768. Feb. 14.

16 39 50

Im.

16 39 28

0

22 — Paris. Q.

17 42 37

-

17 42 21

0

16 — Stockh.

16.

12 8 37

-

12 9 14

0

37 + Upfala.

12 8 54

-

12 8 55

0

1 -f Tyrnav.

12 1 1 9

-*■

12 10 54

0

15 — -Stockh.

12 59 24

-

12 59 57

0

33 + Peterfburg.

Mart, i .

9 46 49

-

9 47 26

0

37 _j_ Philadelphia.

H 57 57

-■

14 57 21

0

36 — Paris. Cl.

15 58 20

-

*5 58 15

0

5 — Tyrnav.

3-

IO 26 59

-

10 27 4

0

5 + Tyrnav.

8.

J7 54 32

-

17 54 10

0

22 — Upfala.

10.

11 22 15

-

11 21 56

0

19 — Paris. Cl.

1 2 22 40

-*■

12 22 50

0

10 -f Tyrnav.

13 13 25

-

i'3 J3 52

0

27 4- Peterfburg.

*7-

l3 32 J7

-

13 32 47

0

30 4- Geneve.

19.

9 39 0

-

9 38 56

0

4 — Peterfburg.

24.

*5 29 3

-

15 29 3

0

0 Geneve.

26.

9 43 3

-

9 43 1&

0

13 4- Paris. O.

9 58 1

9 58 6

0

5 4" Geneve.

10 43 56

-

io 44 12

0

16 + T yrnav.

ii 34 52

-

** 35 J4

0

22 4~ Peterfburg.

Apr. 2.

11 29 33

-

11 30 25

0

52 4- Greenw. d.

V. .O

i'a 42 43

-

12 42 36

0

7 — Stockh.

18.

12 1 37

Em.

12 1 14

0

23 — Greenw.

25-

8 56 5°

-

8 56 33

0

17 — Philadelphia.

13 57 19

-

• 13 57 i°

0

9 — Greenw.

27.

8 35 11

-

8 35 26

0

15 4” Paris. Cl.

Mai. 4.

10 31 0

-

10 30 56

0

4 — Paris. Cl.

II 32 18

-

11 31 50

0

28 — Tyrnav.

11 33 22

-

11 33 49

0

27 4- Stockh.

11.

12 l6 46

«

12 l6 46

0

0 Greenw.

12 26 15

-

12 26 4

0

l I — • Paris. CL

6

Obfervationes

the Difference of Longitude , See. 175

Obfervationes comparatae primi fateliitis Jovis.

Ann. Temp.

Oblervationis.

Calculus.

DifF. Calc. Obfervatorium.

M D.

h

/

tr

h r "

/

//

1768. Mai. 20.

8

49

54

-

8 49 29

0

25 — - Paris. Cl.

9

52

6

-

9 52 22

0

16 -f* Stockh.

27.

10

43

14

-

10 43 44

0

30 4“ Paris, Cl.

Jon. 3.

12

28

6

-

12 28 19

0

"3 T Greenw.

12

37

39

-

12 37 37

0

2 — Paris. Cl.

12.

8

50

16

-

CO

1-1

0

00

0

2 Greenw.

10

0

23

-

V*

0

0

'O

0

26 4~ Upfala.

IO

2

32

-

10 2 29

0

3 — Stockh.

, I9-

IO

43

27

-

IO 4-3 38

0

1 1 4“ Greenw.

IO

53

43

-

IO 52 56

0

47 — Paris. Cl. d .

Jul. 5.

9

8

5

-

9 8 13

0

8 4“ Paris. Cl.

1769. Jan. 17.

18

37

12

Im.

18 37 6

0

6 — Stockh.

Feb. 2.

** 16

46

3°

-

l6 46 I9

0

11 — > Tyrnav.

16.

H

21

IO

-

14 20 57

0

13 — Norriton.

H

21

5i

-

14 21 49

0

2 — Philadelphia.

23*

16

*5

1

-

16 14 59

0

2 — Norriton.

16

16

21

-

16 15 51

0

30 — Philadelphia.

Mart. 20.

16

9

9

-

16 9 3

0

6 Paris. Cl.

29.

12

25

7

-

12 24 22

0

45 — Greenw.

13

34

34

-

!3 34 34

0

0 T yrnav.

*3

36

54

-

!3 36 33

0

21 — Stockh.

Apr. 3.

14

49

25

-

14 49 49

0

24 4~ Norriton.

50

48

—

14 50 41

0

7 — Philadelphia.

5-

*5

13

35

-

!S J3 1

0

34 — Lund.

32

30

-

15 32 27

0

3 — Stockh.

io.

16

46

0

-

16 45 41

0

19 — ■ Norriton.

12.

1 1

H

37

-

II 14 40

0

3 4“ Norriton.

1 1

i5

49

-

II 15 32

0

17 — Philadelphia.

16

16

8

-

l6 l6 9

0

1 -f- Greenw.

16

25

39

-

l6 25 27

0

12 — Paris. Cl.

21.

12

50

14

-

12 50 I

0

13 — Paris. Cl.

S2

41

—

13 52 54

0

13 4- Stockh. d»

Obfervationes

176

Mr. wargentin’s Letter on

Obfervationes comparatae primi fatellitis Jovis.

Ann. Temp. Qbfervationis

Calculus.

DifT. Calc. Obfervatorium.

M. D.

h ' "

h > //

t it

1769. Apr. 28.

H 35 17

-

14 36 7

° 5° + Greenw.

14 45 J5

-

14 45 25

0 10 -f Paris. Cl.

3°*

9 13 42

-

9 14 16

0 34 + Paris. 0.

10 16 38

-

10 17 9

0 31 + Stockh.

Mai. 5.

11 29 27

-

11 29 43

0 16 -f Norriton.

11 30 28

~

11 3° 35

07 + Philadelphia.

12.

10 37 6

Em.

10 35 37

1 29 — Otaheite. d.

16.

9 3i 35

-

9 3° 54

0 41 — Greenw.

9 4i 1

-

9 40 12

0 49 — Paris. Cl.

10 43 7

-

10 43 5

0 2 — Stockh.

21.

11 55 !3

-

11 55 5

0 8 — Norriton.

23-

11 34 52

-

11 34 28

0 24 — Paris. Cl.

12 37 42

-

12 37 21

0 21 1 — Stockh.

28.

11 3i 59

-

11 3i 53

0 6 — S. Jofeph.

Jun. 4.

10 45 31

-

10 46 31

1 0 4- Otaheite.

6.

7 53 58

-

CO

0 10 4- S. Jofeph.

10 11 32

-

10 11 27

0 5 — Norriton.

8.

9 4° 56

-

9 41 20

0 24 + Greenw.

9 5° 4i

-

9 5° 38

0 3 — Paris. Cl.

9 51 9

-

9 5° 36

0 33 — Paris. O.

io Si 45

-

10 51 51

0 64- UpfaJa.

10 53 !5

-

10 53 31

0 16 4- Stockh.

l3-

7 8 16

-

7 8 28

0 12 4- Otaheite.

J2 5 1

-

12 5 1

0 0 Norriton.

*5-

11 35 33

-

” 34 53

0 40 — Greenw.

18.

14 33 36

-

i4 33 37

0 14- Otaheite.

20.

9. 1 43

-

9 1 57

0 14 4- Otaheite.

11 40 56

-

11 41 11

0 15 4- Norriton.

22.

8 27 35

-

8 27 51

0 16 4- Philadelphia.

24-

9 6 41

-

9 7 3

0 22 4* Tyrnav.

27.

10 56 15

-

10 55 39

0 36 — Otaheite.

.*9*

5

8 2 52

—

8 3 i4

0 22 + S. Jofeph.

Obfervationes

the Difference of Longitude, See, 177

Obfervationes comparative primi fatellitis Jovis.

Ann. Temp. Obfervationis.

Calculus.

I) iff. Calc. Obfervatorium.

M. D.

h /

h r rr

/ //

1769. June 29.

IO 21 55

-Em,

IO 21 25

0 30 — Philadelph.

Jui. I.

9 5° 24

-

9 5° 31

0 7 + Greenwich.

n 0 59

-

I I 0 43

0 16 — Tyrnav.

6.

7 18 16

-

7 17 S6

0 20 — Otaheite.

13*

51 49

-

II 51 24

0 25 S. Jofepli.

24.

10 12 28

-

10 ii 41

0 47 — Paris. Cl.

Aug. 23.

7 is 43

-

7 i5 i4

0 34 — Philadelph.

177°. Jan. 29.

17 52 18

Im.

17 52 29

0 11 + Tyrnav*

Mart. 16.

17 2 47

-

17 2 16

031 — Greenwich.

25-

H 37 H

-

i4 36 33

0 41 — Tyrnav.

Mai. 3.

13 9 36

-

l3 9 33

0 3 — Tyrnav.

1.0.

!4 45 45

-

14 46 20

0 3g 4- Lund.

i5 5 43

-

15 5 46

0 3 + Stockholm.

26.

13 2 18

-

13 3 9

0 51 + Berlin*

Jun, 4.

9 40 27

-

9 41 18

0 51 4 Tyrnav.

11.

12 35 22

Em,

12 34 27

0 55 — Greenwich.

20.

10 8 39

—

10 8 6

0 24 — Stockholm.

Jul. 13.

9 5 7

-

9 5 *9

0 12 -f Greenwich.

9 6 24

-

9 5 3s

0 46 — Chiflehurft*

9 59 *5

9 59 1

0 14 — Berlin*

29.

8 34 19

-

8 34 13

0 6 — Tyrnav.

Aug. 5.

9 19 41

-

9 i9 57

0 16 4- Greenwich,

9 20 42

—

9 20 16

0 26 — Chiflehurft.

9 28 52

9 29 12

0 20 4 Paris, CL

10 13 31

-

10 13 34

0 3 4 Berlin.

10 30 25

-

10 30 6

0 19 — Tyrnav.

21.

8 52 49

-

8 52 47

0 2 — - Tvrna'v.

J

Sept. 13.

8 15 14

-

8 14 46

0 28 — Paris. Q*

1771.Mart.28.

16 45 22

Im.

16 45 6

0 16 Paris. CL

Apr. 13.

15 4 at

-

15 4 -56

0 5 — Paris. CL

Mai. 22.

13 46 13

-

13 46 28

0 15 -b Geneve.

¥ol. LXXVII.

A a

Obfervationes

i7 8 Mr. wargentin’s Letter on

Obfervationes comparatse primi fatellitis Jovis.

Ann, Temp. Obfervationis. Calculus. Diff. Calc. Obfervatorium.

M.

D.

h

«

n

h

/

n

/

n

1771. Mai.

22.

H 32

20

Im.

H

32

25

0

5 + Tyrnav.

Jun.

7-

II

44

57

-

I I

44 53

0

4 — Paris. Cl.

II

59

43

-

II

59

50

0

7 4" Geneve.

14,

*3

52

20

-

13

52

14

0

6 — Geneve.

22

4

-

H

21

39

0

25 — Berlin.

j«i. 23.

14

5

3S

Em.

14

4 58

0

40 — Greenwich.

25-

9

44

15

-

9

43

5i

0

24 — Tyrnav.^

Aug.

1.

10

37

38

-

10

38

1

0

23 + Paris Cl.

TO.

8

3

49

-

8

3

38

0

11 — Tyrnav.

*7*

8

49

47

-

8

49 53

0

6 + Greenw.

8

51

0

-

8

50

12

0 48 — Chiflehurft.

9

14

12

-

9

H

8

0

4 — Geneve.

V

10

1

47

-

10

2

4

0

17 4- Stock.

Sept.

2.

8

23

55

-

8

24

2

O

7 4- Tyrnav.

8

26

14

->

8 26

1

O

13 — Stockholm,

9*

9

11

56

9

11

44

0

12 — Greenw.

9

12

18

-

9

12

3

O

15 — Chiflehurft.

25-

7

37

43

-

7

37

24

0

19 — Greenw,

8

49

5i

-

8

49

35

O

16 — Stockh.

oa.

2.

9

35

40

-

9 35

26

O

14 — Greenw.

9

35

56

-

9

35 45

0

11 — Chiileh.

11.

6

2

33

-

6

2

39

0

6 4“ Greenw,

6

3

16

6

2

58

0

18 — Chifleh.

7

*3

21

-

7

12

47

O

34 — Tyrnav.

Nov.

3*

7

32

32

-

7

32

12

0

20 — Tyrnav.

19.

5 52

27

-

5

52

34

0

7 4- Stockh.

177a. Mai.

12.

15

11

3°

Im.

15

12

1

0

31 4- Pekin.

Jun.

9*

*4 57

33

-

h 57

H

0

19 — Greenw.

15

7

32

15

6

32

1

0 — Paris. Cl.

*5

28

20

-

i5

27

55

0

25 — Perinaldo.

25-

*3

9

i7

-

*3

18

43

0

24 — Paris. O.

Obfervationes

the Difference of Longitude, See. 179

Obfervationes comparat* primi fatellitis Jovis.

Ann. Temp. Obfervationis.

Calculus.

Diff. Calc. Obfervatorium,

M. D.

h ' "

h ' //

r n

1772. Jun. 25.

13 4° 9

Im.

13 4° 8

0 i — Perinaldo.

14 20 1

-

14 19 39

0 22 — Tyrnav.

27.

15 22 54

-

15 23 10

0 16 -f- Pekin.

Jul. 2.

IS 32 3i

-

IS 32 27

0 4 — Perinaldo.

11.

11 22 34

-

11 22 33

0 1 — Greenw.

11 22 34

-

11 22 52

0 18 4“ Chill ehurfl.

11 31 38

-

11 31 49

0114- Paris. O.

n 31 57

-

11 31 Si

0 6 — Paris. Cl.

12 32 25

-

12 32 45

0 20 4- Tyrnav.

18.

13 25 10

-

13 25 4

0 6 — Paris. O.

14 25 41

-

14 2S S9

> 0 18 + Tyrnav.

27.

9 38 2

-

9 38 2S

0 23 4“ Chiflehurft,

9 47 28

-

9 47 24

0 4 — Paris. Cl.

11 39 6

km*

11 39 20

0 14 4" Peterfb.

Ang. 3,

11 32 48

-

11 33 2

0 14 4- Chiflehurft.

13 33 40

-

13 33 57

0 17 4- Peterfb,

10.

13 36 46

-

13 37 10

0 24 4” Paris. Oc

13 37 11

-

13 37 I2

0 1 4“ Paris. Cl.

15 28 26

-

15 29 8

0 42 4“ Peterfb.

21.

14 23 21

Em.

14 22 41

0 40 — * Pekin.

26.

14 4 22

14 4 18

0 4 — Greenw.

28.

9 26 ss

-

9 27 20

0 25 4“ Berlin.

9 44 5

-

9 43 52

0 13 — Tyrnav*

30.

10 48 44

-

10 48-31

0 13 — Pekin.

Sept. 4.

11 23 38

-

1 1 23 26

0 12 — Lund.

11 23 50

-

11 24 21

0 29 4“ Berlin.

11 41 11

-

11 40 53

0 18 — Tyrnav.

8.

7 IS 19

-

7 i4 59

0 20 — Pekin.

*3-

8 9 44

8 9 38

0 6 — Stockholm.

*5-

9 12 7

9 12 29

0 22 4“ Pekin.

20.

9 47 54

\

9 47 49

0 5 — Lund.

A a 2

Obfervatione

i8o

Mr. w argent in’s Letter on

Obfervationes comparatae primi fatellitis Jovis.

Anni. Temp. Obfervationis.

Calculus.

Diff. Calc. Obfervatorium.

M. D.

h t n

h / '/

/ //

3 7 72L. Sept. 20.

10 6 56

Em.

10 7 16

0 20 + Stockh.

22.

ii 9 47

-

11 ia 6

0 19 4* Pekin.

27.

10 52 31

-

LO 52 47

0 l6 4- Greenw.

12 2 52

-

12 3- l8

0 26 + Upfala.

12 4 45

-

12 4 58

0 13 4* Stock h.

o&. 4.

12 50 41

-

12 50- 41

O 0 Chiflehurft.

6,

7 S3

-

7 29 6

0 ig 4- Paris. O.

8 13 17

-

8 13 3°

0 1.3 4- Berlin.

8 30 12

-

8 30. 2

0 10 — Tyrnav.

9 16 49

-

9 >7 i3

0 24 4* Greenw.

9 >7 i3

-

9 n 32

0 19 4- Chiflehurft.

10 9 40

-

10 9 58

0 18 4- Lund.

10 10 13

-

10 10. 53

0 40 4- Berlin.

w

10 27 31

-

IO 27 25

0 6 — Tyrnav.

6 1 36

-

6 1 26

0 10 — Pekin*

20.

11 *3 $9

-

11 14 11

0 12 4* Greenw.

11 14 32

-

11 14 30

0 2 — Chiflehurft*

22.

6 36 57

-

6 36 59

0 2 + Berlin.

6 53 28

-

6 53 31

0 34- Tyrnav.

24.

7 58 20

M

7 58 10

0 10 — Pekin.

29.

8 50 14

-

8 49 55

0 19 4- Tyrnav.

31*

9 54 21

-

9 54 25

0 44- Pekin.

Nov. 9.

6 19 6

-

6 18 51

015 — Pekin.

14*

5 59 28

-

5 59 23

0 5 — Greenw.

16.

8 13 54

-

8 13 37

017 — Pekin.

Dec. 2*

6 29 46

-

6 2 9. 41

0 5 — Pekin.

9*

8 23 12

Jw

8 22 37

0 35 — Pekin.

*3*

5 i5 3

5 14 39

0 24 — Lund.

5 *5

-

5 15 34

O 17 — Berlin.

25>

6 36 12

-

6 35 36

0 36 — Pekin.

1773. Mai, 29,

15 18 46

Jm.

15 18 4

0 42 — Perinaldo. d.

Obfervationes

the Difference of Longitude , See. 1 8 r

Obfervationes comparatas primi fatellitis Jovis.

Ann. Temp. Ol

bfervatior

M. D.

h t

I773. JUD. 14.

14 10

l6.

35 34

21.

15 16

M 7.

*3 35

3 4*

15. 28

16.

11 27

23-

11 19

1 1 50

3°-

13 44

35 34

Aug.- 6.

15 37

l5 :'l7

3 5 32

8.

10 0

10 7

10 48

33 37

35*

11 41

3 3 55

12 41

33 32

%%.

13 26

15 28

24.

9 8

iS 41

26.

10 10

29.

35 32

35 47

1S 53

33*

9 51

10 22

Calculus.

n

h

/

//

37

Im.

34

10

45

37

-

35

34

23

43

-

35

16

58

59

*3

36

23

55

-

35

28

45

8

-

1 1

27

4°

22

-

11

39

42-

22

-

1 1

5°

l7

28

-

33

44'

6

40

-

3 5

34

45

30

-

35

37

33

36

-

35

3 7

1 1

20

- ..

35

32

10

42

-

10

0

53

35

-

10

7

33

41

-

10

48- 49

37

-

1 1

37

52

5 :

-

11

40 47

58

-

1 1

55

44

23

—

12

41

41

58

-■

33

32

43

34

-

33

27

n

D

20

— •

35

28

17

24

-

9

8

18

22

-

35

41 -

46

31

-

10

10

40

41

-

35

3 2

25'

40

-

35

47

22

49

-

*5

53

42

57

-

9

52

12

16

-

10

22

47

Diff. Calc. Obfervatorium,

/ tt

o 8 + Tyrnav.
o 4 — Pekin,
o 15 + Geneve,
o 24 + Perinaldo. d ,
o 10 — Perinaldo.
o 32 + Peterfburg,
o 20 + Green'w.
o 5 — Perinaldo,
o 22 ■ — Perinaldo.
o 5 + Peterfburg.
017 — Paris. Cl.
o 25 — - Paris. O.

o 10— Geneve.

A

o 1 1 + Geneve,
o 2 — Perinaldo.
0.8+ Stockholm,
o 15 + Peterib
O 18 — Paris. Cl.
o .14 — ■ Geneve,
o 18 + Tyrnav,
o 15 — Peterfburg.
o 49 + Green w. >L
c 3 — Peter fb
o 6 — Stockholm,
o 24 + Pekin.

O 9 + Pekin,

016— Paris. Cl.
018— Geneve,
o 7 — Perinaldo.
o 15 + Greenw.
o 31 + Perinaldo.

Obfcrvatiooes

1 82 Mr. WAR-GEN tin's Letter on

Obfervationes comparatoe primi fate! litis Jo vis.

Ann. Temp. Obfervatio.nis. Calculus. D iff. Calc . Obfervatorium.

M. D.

h

/ u

(h

t!

/

n

1 7 7 3* Aug-S1-

1 1

2 7

Im.

I I

2

24

0

»7 +

T yrnav.

Sept. 7.

12

18 35

-

12

*9

I I

0

36 +

Perinaldo.

9*

14

2 56

-

14

3

27

0

31 +

Pekin,

14.

14

9 8

-

14

9

36

0

28 +

Geneve.

*5

46 14

-

*5

46

35

0

21 +

Peterfburg.

' 16.

9

27 O

-

9

27

8

0

8 +

Stockholm.

25-

12

26 7

-

12

26

27

0

20 +

Pekin.

27-

9

6 28

Em.

9

6

3°

0

2 +

Pekin.

oa. 2.

9

58 55

-

9

53

41

0

14 —

Tyrnav.

10

49 49

-

10

49

43

0

6 —

Peterfburg.

16

33 55

16

34

8

0

13 +

Pekin.

9*

10

44 40

-

10

45

13

0

33 +

Greenw.

■

12

46 30

-

12

46

27

0

0 , - - ,

Peterfburg.

II.

7

15 30

-

7

i5

36

0

6 +

Peterfb.

12

59 *9

—

13

0

1

0

42 +

Pekin.

*3-

7

28 57

-

7

29

12

0

15 +

Pekin.

16.

12

5° 34

-

12

51

2

0

28 +

Paris. Cl.

13

12 37

-

*3

12

19

0

18 —

Perinaldo.

18.

7

19 48

-

7

20

5

0

17 +

Paris. Cl.

7

4i 33

-

7

4i

22

0

1 1 —

Perinaldo.

8

20 52

-

8

20

59

0

7 +

Tyrnav.

20.

9

25 6

9

25

33

0

27 +

Pekin.

25.

9

6 12

-•

9

6

5o

0

38 +

Greenw.

9

J5 35

-

9

16

8

0

33 +

Paris. Cl.

. - ' -

9

15 49

-

9

16

6

0

17 +

Paris. O.

9

37 1

-

9

37

31

0

3° +

Perinaldo.

10

17 19

-

10

*7

21

0

2 +

Upfala.

10

18 43

-

10

J9

1

0

18 +

Stockholm.

27.

11

20 54

-

11

21

27

0

33 +

Pekin.

29.

5

49 54

-

5

5°

20

0

26 +

Pekin.

► Nov. 1.

11

2 10

11

2

25

0

15 +

Greenw.

Obfervationes

the Difference of Longitude , See. 183

Obfervation.es comparatee primi fatellitis Jovis.

Ann. Temp. Obfervationis. Calculus. Diff. Calc. Obfervatorium.

M. D.

h f "

h / "

/

rr

i 773* Nov. 1.

II II 49

Em.

11 11 43

0

6 — Paris. Cl.

11 33 24

-

11 33 0

O

^24 — Perinaldo.

3*

6 23 58

-

6 23 58

O

0 Lund.

26.

6 12 30

6 13 3

O

33 + Perinaldo.

6 35 2

-

6 35 13

O

11 4- Lund.

6 52 57

-

6 52 59

O

2 4- Upfala.

6 54 45

-

6 54 39

O

6 — Stock h.

7 44 4

-

7 43 42

O

22 — Peterfburg.

Dec. 3.

8 46 25

-

8 46 5

O

20 — Upfala.

8 47 58

-

8 47 45

O

13 — Stockh.

10.

9 27 59

-

9 28 15

O

164- ' Green w.

19.

6 59 !5

-

6 59 11

O

4 — Tyrnav.

1774. Jan. 2.

9 42 59

-

9 42 55

O

4 — Paris. CL

4-

5 1 27

-

5 12 4

0

3 — - Tyrnav.

11.

6 4 24

6 4 10

0

14 — Paris. CL

772

-

7 7 3

0

1 4- Stockh.

iB,

7 48 22

-

7 4s 20

0

2 — GreenWo

Feb. 3.

6 15 33

-

6 15 8

0

25 - — Paris. CL

7 16 17

-

71621

0

4 4- Upfala.

7 18 10

-

•<&r

CO

0

9 — Stockh.

19.

5 33 58

-

5 38 41

0

17 — Stockh*

26.

6 23 29

-

6 23 14

0

15 — Green w.

Aug. 4.

12 32 38

Im.

12 32 16

0

22 — Tyrnav.

12 32 51

-

12 32 35

0

16 — Upfala.

12 34 42

-

12 34 J5

0

27 — Stockh.

13 23 17

-

13 23 18

0

1 4~ Petersburg.

18.

15 21 15

15 21 3

0

12 — Paris. CL

20.

IO 5I IO

-

10 51 6

0

4 — Upfala.

JO 53 9

- '

10 52 46

0

23 — ■ Stockh.

27-

12 46 32

12 46 44

0

12 4“ Upfala.

Sept. 3,

14 25 0

-

14 24 48

0

12 — Lund.

Oblervationes

184

Mr. w argent in’s Letter on

Obfervationes comparatse primi fatejlitis Jovis.

Temp.

Obfervationis

Calculus.

D iff. Calc. Obfervatorium*

M. D,

h ' /'

h / //

/ rr

Sept. 3.

14 42 21

Im.

14 42 15

0 6 — Tyrnav.

15 33 29

-

i5 33 i7

0 12 — Peterfburg.

10.

15 ^8 31

-

15 28 7

0 24 — Greenw.

16 38 28

-

16 38 19

0 9 — Tyrnav.

12.

9 57 H

-

9 57 13

0 1 — Greenw.

ii 9 46

-

11 9 24

0 22 — Stockh.

11 58 36

-

11 58 27

0 9 — Peterfb.

21.

8 23 43

-

8 23 43

0 0 Peterfb.

26,

13 49 S3

-

13 49 4°

0 13 — Greenw.

13 59 42

-

13 58 58

0 44 — Paris. Cl.

oa. 3.

15 46 19

-

IS 45 47

0 32 — Greenw.

15 55 45

-

15 55 5

0 40 — Paris. Cl.

16 5s 31

-

16 57 58

0 33 — Stockh.

5-

10 24 45

-

10 24 8

0 37 — Paris. Cl.

11 25 9

-

11 25 2

0 7 — Tyrnav.

•

11 26 59

-

1127 1

0 2 + Stockh. d .

12 16 5

-

12 16 4

0 1 — Peterfb.

to.

17 4i 57

-

17 4J 43

0 14 — Greenw.

12.

12 20 23

-

12 20 0

0 25 — Paris. Cl,

14*

7 50 7 •

-

7 50 6

0 1 — Uplala.

7 52 0

-

7 51 46

0 14 — Stockh.

19.

14 16 20

-

14 15 32

0 48 — Paris. Cl.

2 r.

8 35 0

—

8 35 3

0 3 4" Greenw.

8 44 47

-

8 44 21

0 26- — Paris. Cl.

26.

1.6 1 23

-

16 1 26

0 3 + Greenw.

3°-

6 10 47

-

6 10 59

0 12 + Stcckh.

'Nov 1,1.

17 19 3

Em.

17 18 53

0 10 — Lund.

*3-

1252

-

12 4 39

0 23 — Tyrnav.

*5-

6 15 39

-

6 15 36

0 3 — Lund.

6 34 34

-

6 35 2

0 28 -j- Stockh.

,20.

12 56 42

-

12 57 3

0 21 4- Paris. CL

■ ■ f 1 A nO'j

Obfervationes

the Difference of Longitude , See.
Obfervationes comparator primi fatellitis Jovis,

18

5

Ann. Temp. Obfervationis.

Calculus.

DifE Calc. Obfervatori

M. D.

h / //

h t r'

1 n

1774. Nov. 22.

8 27 22

Em.

8 28 10

0 48 4- Stockh.

Dec. 6.

11 9 25

-

1 1 10 7

O 42 4- Paris. Cl.

12 11 9

12 11 1

0 8 — Tyrnav.

24.

4 52 25

-

4 52 47

0 22 4 Stockh.

29.

11 3 48

-

11 4 32

0 44 4 Green w.

12 14 15

12 15 3

0 48 4 Upfala.

12 16 11

-

12 16 43

0 32 4 Stockh:

3i-

6 25 S

-

6 25 17

0 12 4 Lund.

177 5- Jan. 23.

6 48 55

M

6 49 43

0 48 4* Eyrnav,

Feb. 15.

5 53 2

-

5 53 32

0 30 4 Green w.

22.

7 49 37

-

7 49 59

0 22 4- Greenw.

8 42 39

8 42 44

0 54 Lund.

906

-

9 0 1 1

0 5 4 Tyrnav,

9 1 55

-

9 2 10

0 15 4 Stockh.

Mart. 10.

7 23 51

-

7 23 53

0 24 Tyrnav.

l7-

8 11 7

8 11 21

0 14 4 Greenw.

Jul. 15.

14 42 36

Im.

14 42 14

0 22 — Greenw.

24.

13 5 40

-

13 5 46

0 64 Peterfb.

Aug. 7.

J4 53 55

~

14 53 26

0 29 — Greenw.

16.

13 18 25

-

13 18 29

0 44 Peterfb,

Sept. 1.

11 38 30

-

11 38 45

0 15 4 Peterfb.

*5-

*5 31 7

15 3° 54

0 13— Peterfb.

24.

11 6 50

-

11 6 56

0 64 Stockh.

oa. 1.

n 50 3

-

11 50 36

0 33 4 Greenw.

>3 3 2

-

13 2 47

0 15 — Stockh.

10.

9 27 23

-

9 27 20

0 3 — - Stockh.

22.

17 37 1

-

17 36 25

0 36 — Greenw.

Nov. 2.

8 27 48

-

8 27 35

0 13 — Greenw.

18.

7 54 22

-

7 54 S

0 17 — Stockh.

Dec. 11.

10 6 5

Em.

10 6 34

0 29 4 Stockh.

20.

6 23 33

-

6 23 37

0 44 Upfala.

Vol. LX XV II.

B b

Obfervatf

num,

i8 6

Mr. wargen tin’s Letter, See

Obfervationes comparatae primi fatellitis Jovis.

Ann. Temp.

Obfervationis

Calculus.

Diff. Calc.

Obfervatorium,

M. D.

h / /a

h t

n

t

tt

1775. Dec. 20.

6 24 55

Em.

6 25

*7

0

22 +

Stockh.

27.

7 3 6

-

7 4

9

1

3 +

Greenw.

8 15 17

-

8 16

20

1

3 +

Stockh.

1776. Jan. 12.

6 26 48

-

6 27

22

0

34 4

Stockh.

J9*

8 19 7

-

8 19

5i

0

44 4

Stockh.

26.

10 12 15

i° 13

7

0

52 4

Stockh.

28.

4 40 51

-

4 4i

32

0

4i 4

Stockh.

Febr. 2.

12 6 20

-

12 7

7

0

47 4

Stockh.

27.

6 51 S

-

6 51

33

0

28 +

Stockh,

C is7 3

XIV. A Method of finding the Value of an infinite Series oj
decreafing Quantities of a certain Form , vehen it con-
verges too Jlowly to be fummed in the common Way by
the mere Computation and Addition or Subtraction of
fome of its initial Terms. By Francis Maferes, Ff quire ,
F. R. S. Curfitor Baron of the Exchequer.

Read Feb. 13, A RTIGLE Iff Let a , b, c, d, e,f g, h, &c.

ad infinitum , reprefent a decreafing pro-
greffian of numbers, fo that b fhall be lets than a, and
c than b, and d than c, and fo on of the following num-
bers, ad infinitum.

And 2dly, let thefe numbers be fo related to each
other, that they not only fhall form a decreafing progref-
fion themfelves, but that their differences, a— b, b—c ,
c-d, d-e, e—ff-g,g-h, See. fhall alfo form a decreafing
progreffion, fo that b—c fhall be lefs than a-b, and c-d
than b—c , and d—e than c—d, and fo on of the following
differences; and likewife, that the differences of thefe
differences (which may be called the fecond differences of
the original numbers a, b, c, d, e, f g, h, 8cc. fhall form
a decreafing progreffion ; and that the differences of thole
fecond differences, or the third differences of the original

B b a numbers

1 88 Mr. maseres’s Method of

numbers a, h, c, d, e, f g, h> 8cc. fhall alfo form a de-
er eafing progreffion ; and in like manner, that the dif-
ferences of the faid third differences, or the fourth dif-
ferences^ of the original numbers a , b, c, d, e,f g, h> 8ec.
and the fifth and fixth differences, and all higher differ-
ences, of the fame numbers, fir all alfo form decreafing
progreflions.

And 3dly, let x be a quantity of any magnitude not
greater than unity.

Upon thefe fuppofitions the value of the infinite feries
a— bx.+cxx-dx'i-1rex*-fxi+gx(‘—hx1 + 8 cc. (in which the
fecond, fourth, fixth, and eighth, and every following
even term, is marked with the fign - , or is to be fub-
trafted from that which immediately precedes it) may be
determined in the following manner.

Art. 2. Compute the firlf, fecond, third, fourth,
and other fubfequent differences of the co-efficients of
the powers of x in this feries, that is, of the numbers
b, c} d,.e,fygr h, See. as far as fhall be convenient, Thefe
differences will be as follows.,

Firft differences, b — c^c — dr d — e, e—f f—g, g — h, &c,

Second differences,

l — c — (c—dy c — d—[d~eX, d~—e — e'—f~\f~g[, f—g — Q— b\ &c*
or, b—2 c-\- dy c—2 dr f e, d—z e + /,.. e—zf+gy f—zg -f b> &c.

Third differences,

c-\- d * {c^zd^t\ , c — 2 d-\- e — [d — ze -J-/1, d—2e±f — |V — 2 f+g\,
e-zf+g—lf—zg &c._

Ol y

finding the Value of an infinite Series , 8 cc. 189

or, b — 3^ + 3^ — e> c—^d+ze—f, d-ze+zf—g, e— 3f+3g~ b> &c.
Fourth differences, b — 3 c 4 3*/ — e — \c — 3 d + 3 *—/),

3-^+ 3 e~f— + ,

3 * + 3f—g— 3/ + 3£ — ^ , &c.

or, £— 4^4-6/— 4*4-/, c— - 4d+6e — 4/4-^, ^—4*4-6/— 4^+^, &eQ
Fifth differences, £ — 4c + 6d — 4*4*/ — |r— 4 d+ 6 * — 4/4-~g| ,

c— 4^+6^ — 4/+ £ — [d—^e 4- 6f—~4g 4^\ , &c.
or, ^—5^4-i°^— 1°^4-5/~ g, c— $d+iOe — lof+sg — b , &c*

Sixth differences,

^—5^4-10^—10^4-5/—^ — !r— 5^4- io<?— 10/4- $g — h\> &c9
or, b — 6r4-i5^ — 20^4- 15/— -6^4-^, &c.

Let the firft difference of the firft order, to. wit,
b.—c , be called d1;

and the firft difference of the fecond order, to wit,
b—zc+d, be called n”;

and the firft difference of the third order, to wit,

b— 3 c 3 d—ey be called b1H ;

and the firft difference of the fourth order, to wit,
b~ 4C+ 6d— 4-e+f, be called d1v;
and the firft difference of the fifth order, to wit,

b— $c+iad—- ioe+ $f—g, be called dv;

and the firft difference of the fixth order, to wit,,.

b- 6c+ 15 d—zoe+ 1 5/- 6g+h, be called dvi;
and in like manner let the firft differences of the feventh,
eighth, ninth, and tenth, and every following order of'
differences be denoted by dvii,.dvui, nIX, dx, Sec. that is, ,
by the capital letter d, with a Roman numeral figure

annexed

IQO

Mr. MasKres’S Method of
annexed to it, expreffing the order of differences to

which it belongs,

Thefe things being fuppofe'd, the aforefaid infinite fe-
ries a—bx+cxx— dx* + ex*- fxt+gx6— hx^ 8ec. will be
equal to the following differential feries, to wit,

bx

D1 xx

a-

Dntf3 D111 X* D IVJf5

I + * I -i

I x\ I -f- A'i I -f- a)

1 -f- XI

T>'r'X7 0

, S ~ ■ ) 7

I -f A

in which feries all the terms after the firft term a are
marked with the fign or are to be fubtra&ed from
that term.

Art. 3. If we infert the differences themfelves inftead
of d1, D11, Dnr, div, dv, &c. in the foregoing differential
feries (which it may perhaps fometimes be convenient

bx

to do) that feries will be as follows: a—ff- — \b— ~c x

XX

I +*

I f

id1

I + A I I -f- A'

— \b~j^c + ^d-Aee+fx df— -

I -j- aJ

-\b- 5 c+ io^-io^+5_/-^x=^

1 If

~\b~6c+\$d-2oe+isf-6g+bx-~- &c. ad infini-
tum.

Of the convergency of the foregoing differential feries.

Art. 4. The foregoing differential feries will always
converge with a confiderable degree of fwiftnefs, fo

that

finding the Value of an infinite Series , f ee. igx

that fix or eight of its terms will give the value of
the whole (and confequently that of the original feries
a-bx+cx x-dx^ + ex^- fx^+gx^-bx1 + &c. to which it
is equal) exadt to feveral places of figures, even in the
molt difficult cafes : for if x is = i (which is its greateft
pofiible magnitude) i+x will be — i + i or 2, and confe-
quently t Tx[i i +a,)35 1 +A'tfi 1 +x);, and the following
powers of 1 + x, will be equal to 4, 8, 16, 32, and the
following powers of 2 ; and the powers of the fraction

X

ppp will be equal to the powers of Therefore the feries

a

bx

DT XX

D11*3

TTIA.^ DIV^.5 Dv*(

DV*X‘

1 +■*■ r+i* r i~t xV

in this cafe be = to a

I +a1+ I + h’ I -f d

b D 1 D11 DIXI

I-M

8cc.will’

DIT DT EVI

~fi~ 64-778-tZC'

4 s x6

the terms of which decreafe in a greater proportion than
that of 1 to 2, becaufe. the numerators a , b, d1, c", d111,
D1V, dv, DVI, &c. form a decreafing progrefilon, and the
denominators increafe in the proportion of 2 to 1 .

Of the invejtigation of the foregoing differential feries.

Art. 5. The foregoing differential feries was invefti-
gated by firft, fuppofing the original feries a-bx+cxx
-dxi+ex*~fxs+gx(,—bx1 + & c. to be equal to another
feries whofe terms fhould involve the fame powers of .v
as the former, but in which every power of x fhould be

multiplied.

192

Mr . maseres’s Method of

l+x

in

multiplied into the fame power of the fraction
order to accelerate their convergency, and then inquiring
what .would be the co-efficients of the terms of fuch a
feries, if fuch a feries is poffible, and what would be the
ligns to be prefixed to them, or in what manner they
would be connecSted with the firft term, whether by ad-
dition or fubtracfion. In order to this inquiry, I denoted
the unknown co-efficients of the affumed feries by the
capital letters p, q_, r, s, t, v, &c. and wrote down the
terms of it near each other, without prefixing to hem

either of the figns

and -

>ut

each other only by a comma; fo
equation, from which I derivt-f
above-mentioned, was as follows •.

aratedi them from
it the fundamental
e differential feries
b x + c x x-dx^+e. x 1

-fxi+gx(‘—hxn‘ + See. is = f,

QJ

T X

a r x\

3 ^

I -h^V I+£

v A3

&:c. By neceffary deductions from this equation

it appeared that p would be equal to a\ and that all
the following terms, of the affumed feries, to wit,

OX RAA sa3 TA4 V*5 _ _ , _ , _ .

— =rT> Sec. muff be fubtracted

I+Ai I+U I+d I+A’I

from the firft term p, or a; and that would be equal to
b-C) or d1; and r =b-c-[c^d, or b-zc+d, or d11; and
2C+d~ [c— 2 d+e: or b- %c+ £d~ey or D111; and

finding the Value of an infinite Series. 193

t=£-4C+6*/-4£+/, or div; and v =fr- $c+iod-ioe
+ $f-g, or dv; and fo on of the following co-efficients,
to wit, that every new co-efficient of the affumed feries
is equal to the firft difference of the next order of the
differences derived from the original co-efficients
b, c, d, e, f gy by &.c. And from hence I concluded that
the feries a- bx + cxx-dx^-rex^-fx^+gx^-hx1 + See.
was equal to the feries,

a-

bx

T>'xx

D11*3

> 1 1 1 r4

D1^

Dv X

D VI Y7

1+x I+A>

1+*'

+ I + A

I

I

Sec.

Art. 6. The thought of fuppofing the original feries
a-bx + exx-dx^ + ex^-fx^-r Sec. to be equal to the feries

QX R XX S#3 T X^ V Xs

‘ &c. containing the

> 1 + #

-M

f+H4 I +a]

powers of x multiplied into the fame powers of the

fraction ppp in order to accelerate their convergency,
occurred to me in confequence of reading the late Mr.
thomas simpson’s Mathematical Differtations, p. 62,
63. concerning the fummation of feriefes, in which he
makes a fuppofition of a limilar kind. Yet there feems
to be a confiderable difference between his propofftion
and that which is the fubjedt of thefe pages ; for he feems
to fuppofe his quantities/), q, r, s, t, See. (which anfwer
to a, by Cy dy £y Sec. in the notation made ufe of in the
above feriefes) to form an increafing progreffion of
terms, and accordingly fubtradts p from q, and q from r,
Vol. LXVII. C c and

194 JVfr. maseres’s Method of

and r from s, and s from t, and fo on; and he feems alfo
to fuppofe the differences q-p , r-q, s—r , t-s, See. to
form an increafing progreffion, and every fubfequent
order of differences to form likewife an increafing pro-
greffion, and accordingly fubtraefs q-p from r-q, and
r—q from s-r, and s—r from t-s, and fo on; whereas in
the foregoing feries a— b x+cx x-dx^’+ex*- fx'+gx**— bx1
+ See. the numbers a, b, c, d, e, f g, h, See. are fuppofed
to form a decreafing progreffion of terms, as they are
moft commonly found to do in the feriefes that occur in
the folution of mathematical or philofophical problems*

Examples of the. ufefulnefs of the foregoing differential fe-
ries in finding the values of infinite feriefes whofe terms
decreafe very ffozvly.

Computations of the lengths of circular arcs by means of
infinite feriefes derived from their tangents-.

Art. 7. It is well known, that if r be put for the
radius of a circle, and t for the tangent of any arch in it
that is not greater than 45 °, the magnitude of the arch
whole tangent is t will be expreffed by the infinite feries

r r
’ — “ 4 :

7 r 9 r

t1'

13- 4 ;

Hr 1 3 r

15 r

— + Sec. This fe-

ries converges with, great fwiftnefs when the tangent is
1 much

finding the Value of an infinite, Series , <kc. 195
much lefs than the radius; but when the taigent is
nearly equal to the radius, it converges exceeding {lowly ;
and when it is quite equal to the radius, or the arch is
equal to 450, the decreafe of the terms is fo, flow as to
make the computation of it in the common way, by com-
puting the value of its initial terms, abfolutely impradi-
cable. For Sir Isaac newton has obferved concerning
this feries in that extreme cafe (which then becomes

equal tor — + — — H + + See.) and another

u 3 5 7 9 11 13 i5 J

feries that is almolf as flow as this, that to exhibit its

value exact to twenty decimal places of figures, there
would be occaflon for no lefs than five thoufand mil-
lions of its terms, to compute which would take up
above a thoufand years. See Sir Isaac newton’s fecond
letter to Mr. oldenburgh, dated October 24, 1676,
in the Commercium Epifiolicum , p. 159. In tliefe
cafes therefore it will be convenient to make ufe of
fome artifice to difeover the value of the leries

f f
— H

t t

73 +

- + 8:c. ; and we

t_ r

3 r F 5 r* 7 9 ru 1 1 137"“ 15

fliall find the application of the differential feries above-
mentioned to be a very proper artifice for this purpofe.
Art. 8. In order to make this application, we muft con-

,3 yS f Zr3 fl$

fider the feries t- — '4— ■ + + ^c*

3 r r 5 7 r 9 r ll r I 3 r 1 3 r

as being the produd of the multiplication of t into the

C c 2 feries

196

Mr. maseres’s Method of

feries 1 -

tt

3rr 5

>]r6 ^ 9 r

1 1 r

13;-

1 5r,+

Sec. and

tt

muft fubftitute x inftead of — in the terms of this laft fe-

rr

ries, by which means it will be converted into the feries

X XX

I -T “

3 5

+ — +JZ--—r+ Sec. This feries is of

the fame form with the original feries above-mentioned,
a-bx + cxx—dxi + ex^-fxs+gx(,-bxljr Sec. the numeral
co-efficients 1 , }, j, fr, TV, 8cc. of the powers of a;

in the former feries anfwering to the literal or general
co-efficients a, b , c, d, e, f \ g, b, Sec. of the fame powers in
the latter feries. Andthefe numeral co-efficients evidently
form a decreafing progreffion, as the co-efficients a, b, c,
d, ey f, g, b, Sec. are fuppofed to do; and we fhall find,
upon examination, that the differences of thefe numeral
co-efficients, of the feveral fuccefiive orders, alfo confti-
tute decreafing progreffions, as the feveral fuccefiive or-
ders of differences of the co-efficients a , by c , d, e, f, g, b,
Sec. are fuppofed to do. Confequently the feries

X XX X 3 X 4 X ^ X ^ X ^

1 ~ T + T~ 7’f9-rT+T3~r^+ will he efiu£fi to the dif-
ferential feries

bx

T>1 X X D11*3 D111*4 DIV*5

Dv/

Dyl X7

See. if

1 +*1 i+*r 1 1 +n 5 1 +^1° 1 -(-a)

we fuppofe the letters a, b, c, d, e, f, g, b, Sec. to be
equal to the numbers 1, }, j, }, fr, T'T, T'T, &c. and
D', Dnj Din, D,v, dv, dvi, 8cc. to be the firft differences of
4 the

.. finding the Value of an infinite Series , 8cc. 19 7.

the feveral orders of differences of thofe numbers, be-
ginning from the fecond term }. Now the values of
thefe numbers, 1, }, }, j, -f, -f, 8 cc. and of their

differences of the feveral fucceflive orders, beginning
from the fecond term j, will, when expreffed in decimal:
fractions, be as follows : '

1 is = 1.000,000,000,000;

7 = •3'3'3V333>333>333 >'

j = .200,000,000,000;

7 = .142,857,142,857;

I = .III, XII, 111,711;

TT = .090,909,090,909;

it = .076,923,076,923;

l^j = .066,666,666,666.

The differences of thefe numbers, beginning from the
fecond term, -333>333>333>33> are as follows;

Firft differences.

•I33>333>333>333;

.057,142,857,143;

.031, 746, 031, 746;
.020,202,020,202;
.013,986,013,986;
.010,256,410,257;
&c.

Second differences.
.076,190,476,190;
.025,396,825,397;
.011,544,011,544;
.006,216,006,216;
.003,729,603,729;
&c.

Third

19B Mr, maseres's Method of

Third, differences.

■05°, 793*650,793;
.013,852,813,853;

.005,328,005,328;
.002,486,402,487 ;

Be c.

Fourth differences.

•036,940,836,940;
.008,524,808,525;
.002.841,602,841 ;

Sec.

Fifth differences.

.028,416,028,41 5 ;
.005,683,205,684;
Sec.

Sixth differences.
.022,732,822,731;
8cc.

Therefore d1 is = .133*333,333,333;

D11 = .076,190,476,190;

DUI =-050,793,650,793;
DIV =.036,940,836,940;
Dv = .028,416,028,415;

Dvt = .022,732,822,731.

Therefore the feries i~—+~

3 S

equal to the feries

A*5 X6 X 1

if IS 15

+ 8cc. is

1 •333*333,333*333, * I+*

A- AT

33>333?333>333> x

— .076,1 90,476,1 90, x

- -050,793*650,793, X

- .036,

finding the Value of an infinite Series , 8cc. 199

X *

~ .036,940,836,940, x -===p

A:6

- .028,416,028,415, X

XI

- .022,732,822,731, X ==p

- <kc. ; and confequently the product of this latter feries
into the tangent t will be equal to the product of the

former feries 1— — + fir
3 5

X 3 X 4 Xs ' , * X , o • .

— + + -+ See. into

7 9 11 I3 »5

the fame quantity, that is, to the product of the feries

tt t* t6 t

^-r-r+TZi *+

3 r r ' 5 r4 7 r6 ‘ 9 r8 1 1 r10 13 r12, 1 5 r J

gent /, or to the original feries

, l L

t~ 1 : * +

3 r r 5 r4 7 r° 9 r

t+

1 1 ri0 13 r12, i5^I+

+ &e. into the tan-
+ 8cc. which ex-

preffes the magnitude of the arch of which t is the
tangent..

Computation of an arch of 30 degrees .

Art. 9. Now let t be the tangent of 30°, which is

rr I

,or x, = — r, or- •
: -- , and ~ will be

2 ’ 1 -\-x

rr

r r 1 1

- r x — • Then will 1 1 be = — ; and
a 3 3

I o i

Therefore 1 + „v will be =1+-=- + -

f 3

=6V and

I

4 4

*4

Therefore — ~ will be -T , and

1 + a!

J+7T " 16

? and =

and *5 = > and

rra3

, and xl

*3?+

. Confequently the, differential feries will in this

cafe

2,00

Mr. maseres’s Method of

cafe be equal to

1 ~ .333>333>333>333> x 4

- 'I33i333’333>333> x ^

- .076,190,476,190, x £

- •050,79-3»6S«>,793» x ^5

- .036,940,836,940, X ^

- .028,4x6,028,415, X ^5

- .022,732,822,731, x -^g-4

- &c. = i — .083,333,333,333,

- .008,333,333,333,

- .001,190,476,190,

- .000,198,412,698,

- .000,036,075,036,

- .000,006,937,506,

- .000,001,387,501,

- 8cc.

= 1 - .093,099,955,597, = 0.906,900,044,403

. - ^ . # ## X* X* JT X X'

Therefore the fenes or

it

3rr 5r 7r 9r “ + i^+ is in this Cafe

= 0.906,900,044,403, or (neglecting the latter figures
-after the fixth place of figures, becaufe we are fure they

are

finding the Value of an infinite Series , Sec, 201
are not exadt) 0.906,900. Therefore the produdt of the

r . tt a t 6 <8

lenes 1 +

3 r r 5 r+ 7 r& 97"

tangent / is equal to 0.906,900, x t — 0.906,900 xr

/I0 £12 /T4

-7^0 + —^,--—;+ 8tc. into the

II r I3r i5r 4

— 0.906,900, x r x

= 0.906,900 x r

1.732,050,8

x .577,350,2 = 0.523,598,8 x r; that is, the feries

t-

+

r t‘
+

$rr Sr 7r'u 9r II r 13' 15r

+ &c. (which ex-

prefles the magnitude of the arch of which t is the tan-
gent) is in this cafe = 0.523,598,8 x r, or an arch of 30*
is equal to 0.523,598,8 x r.

Art. 10. This value of an arch of 30° is exadt in the
fix firft places of figures, and errs only an unit in the fe-
venth figure, which fhould be a 7 inftead of an 8, the
more exadt value of that arch being 0.5 2 3, 5 9 8, 7 7 5, 5 9 8,
8cc. And thus by the help of only eight terms of the
differential feries

a-

bx

T>xXX Dti X3 D111*4 Div^-5 dv^6 D VI X^

1 + * i +^3 14- #1* r+^5 rr^ n^7

have obtained the value of the feries

.*S

&c. we

t t t t t t t r r

t- — +„ — To “t — r»— rm;+ Sec. in the cafe of

$rr $r4 7 r6 9 r ur 137* 15 r 4

an arch of 30 degrees, exadt to fix places of figures.
This degree of exadtnefs is the fame with that which we
fhould attain by computing twelve terms of the feries

7— r4+ 8tc. itfelf, as will

t-

+

: +

3rr Sr4 7 r6 gr b 11 rl° 13^* 15

appear from the following calculation
Vol. LXVII. Dd

Art.

202

Mr. maseres’s Method of

. t3 I5 /? <9 t" t'3

Art. ii. The feries t- — • 4-—;-— +;r^ - +

3 r r 5 r 7 r 9 r

1 1 r*

I qr'

^7

FJ9

- r

+ -

17 r16 19 r15'-' air*® ”23^ + ^CC* *S ~ t * t^ie fertes

tt t* t 6 f

.12

3rr 5

7 r 9r° 1 1 r

/T4 /

+

16

.13

I3rlx J5r14 1J r16 19 r18 2irzo

^2 I

^r. + &e. =, in the cafe of an arch of 30% to rx — into

the feries 1

I I

+

I I

+

I

3x3 5X 9 7x27 9x81 11x243

1 1 1 1

15x2187 17x6561 19x19683 21x59049 23x177,147

1 3 x 729

+ See.

— rx — x.the feries t. 000, 000, 000, 000,

+ -m, hi, hi, in, _ •Q37,°37>o37,037,

5 7

+ .012,345,679,012, _ .004,115,226,337,
9 11

+ -001,371,742,1 !2, _ •ooo,457>247>37°>
r3 !5

+ .000,152,414,790, _ .GOO, O50, 805, 263,

17 !9

+ .000,016,935,087, _ .000,005,645,029,

21 2J

333>333>333-333>,

3

+ &c..

= f x -7- x the feries

^3

1.000,000,000,000, — .1 1 I,III,I I I, I IT,.

+ .022,222,222,222, - .005,291,005,291,
+ .OOI, 37 I, 742, 1 I 2, -.OOO, 374, 1 I 1, 485,
+ .000, 1 05, 5 1 8,624, -.000, 030, 483, 1 5 8,
+ .000,008,965,634, - .000,002,673,961,
+ .000,000,806,432, — .000,000,245,436,
+ See. i

finding tbs Value of an infinite Series , 8cc. 203
~rx -Jr* [1.023,709,255,024,- .116,809,630,442,

» «5

+ Sec#

-f* “X. 906,899, 624,582,

= rx x •9o6>899,624,582,

= r x *5775350,2 x .906,899,624,582, = (if we neglect
the fix latter figures of 906,899,624,582, which we
know to be not exadt) r x *5775350,2 x 906,899,
-rx .523,598,319,029,8 ; of which the firfl: fix fi-
gures *523,598, are exadt.

Computation of an arch of 45 degrees.

Art. 1 2. Now let the tangent t be equal to the radius
r, or the arch (whofe magnitude is exprefled by the

jf tS f t9 fl 5

feries/ + — ■ -—5+ — rs+r^— — a + &c.) be an

arch of 450. This feries will, in this cafe, become equal
tor-— +-7 — -+ - — ^c. of which the firft
eight terms will give the value of the whole exa£t to
only one figure, as will appear by the following com-
putation. Thele terms are equal tor x the eight terms

I- ~+ y “ J+ + r3~Ts » that is> to r x the eisht terms

1. 000, 000, 000, 000, -.333, 333, 333, 333,

+ .200,000,000,000, - .142,857,142,857,

+ .111, hi, in, .111,- .090,909,090,909,

+ .076,923,076,923,- .066,666,666,66 6,

Mr. maseres’s Method of

■204

= rx [1.388, 034, 187, 034, -.633, 766, 233, 765,
-rx .754,267,943,269; which agrees with the value-

of the whole feries r- -j+y-y +y~n + &c- only in the
higheft figure 7, the more exact value of that feries
being .785,398,163,397, Sec. But, if we compute eight
terms of the differential feries which is equal to the

feries r-—+— — -+—-77+ Sec., we fhall thereby obtain

its value exadt to three places of figures; which is as
great a degree of exadtnefs as would be attained by
computing about five hundred terms of the feries

r + + + + 8cc. itfelf. The computation

3 S 7 9 11 J3 *5 1

of the eight firft terms of the faid differential feries is as
follows.

Art. 13. Since t is in this cafe = r, tt will be = rr,
and confequently or x, will be = 1. Therefore xx, x 3,
x^^ x^ , and all the other powers of x, will in this cafe be
equal to 1, and 1 +x will be equal to 1+ 1,. or 2, and the
powers of 1 +# to the powers of 2. Therefore the frac-
tion and its powers will be equal in this cafe to the

fradlion4 and its powers. Therefore the general differ-
ential feries in art. 8. to wit,

i-

finding the Value of an infinite Series , See. 2.05

1 — -333,333,333,333, x i+*

XX

~ 3 3? 3 3 3? 3 3 3? 3 3 3? x

^3

— .076,190,476,190, x jq— |i
“ -050,793,650,793, X

.036,940,836,940, x ■=

+4J

~ .028,416,028,415, x ^5

X7

~ .022,732,822,731, x ==p-.

fkc. will become in this cafe equal to

1 - -333,333,333,333, » 2
“ -i 33, 333, 333,333, x ^
- .076,190,476,190, x -g-

~ -050,793,650,793, X ^

- .036,940,836,940, x p

- .028^,416,028,415, X ^

- -022,732,822,731, x

- 8cc. = i — .166,66 6,666,666,

- -033,333,333,333,

- .009,523,809,523,

2q6 Mr. maseres's Method of

~ .003,174,603,174,

- .001,154,401,154,
.000,444,000,443,

- .000,177,600,177,

- Sec.

- 1 ~ •2I4,474,4I4,47°,

Therefore the feries 1 — - + —

3 5

tt t 4 /8 fTO Z11

^ 3rr~^5r+ 7/6"^9rb iir10^ i$rl*

= *7 ^5)525,585,530.

Jr3 Ar4 *5 *6 #7

7 + 9 ” ' «3~I5 + ^CC' °r

t'*

-7^77-4+ &c. is equal to

•785)5 25,5

t3 r

t 2,rr+ 5r*

85,530; and confequently the feries

f t9 t 11 /I3 t15

— sH — i r3+ — n — — r- + See. is in this cafe

7 r 9 r 11 r iSr

= ^.785, 525, 585, 530, -rx •785,525,585,530; that
is, the length of an arch of 45 °, in a circle whofe ra-
dius is r, is = r x •785,525,585,530; which number is
true to three places of figures, the more exadt value of
that arch being/* x .785,398,163,397, 8cc.

Art. 14. It has been aflerted in art. 12. that in
order to obtain the value of the feries

i 3 r

*

3rr 5r

JL ‘I Cl

y r6 4 gr* Ilr10 4

t'3

l3rlz

tls

ypr. r+ Scc.exadt to 3

places of decimal figures by the mere computation of its
terms, in the cafe of an arch of 45% we muft compute
at leaft 500 of its terms. This maybe proved in the
following manner. The indexes of the powers of t in
that feries are the odd numbers 1, 3, 5, 7, 9, 1 1, 13, 1 5,

8cc.

•finding the Value of an infinite Series , <kc. 2.07
Sec. in their natural order; to which if we add an unit,
the numbers thereby produced will be the even numbers
2, 4, 6, 8, 10, 12, 14, 16, &c. in their natural order,
which are the doubles of the natural numbers, 1, 2, 3,
4) 5) 7, &c. Therefore the number of terms of that

feries from the beginning of it to any given term in it,
including the faid term, is always half the number that
is produced by adding an unit to the index of t in the

faid term. Thus, if we take the term 777^, and add 1 to

11, which is the index of the power of t in it, the fum
will be 1 2, the half of which is 6, which is the number
of terms in the feries from the beginning of it to the

t11

term 777-0, including the faid term, that term being the
fixth term in the feries. If therefore we take the term

t999 #

— 7-,.', and are defirous of knowing its place in the fe-
ries, or the number of terms from the beginning of the
feries to that term inclufively, we muft add 1 to the in-
dex of the power of t in its numerator, which will in-
creafe it to 1000 ; and half this fum, to wit, 500, will
be the number of terms from the beginning of the feries

t 999

to the term - 99ii- inclufively ; or, in other words, this

term wrill be the 500th term of the feries. To arrive
therefore at thofe terms of the feries in which the in-
dexes

2,0 8 Mr. maseres’s Method of

dexes of the powers of t are greater than 999, or 1000,
or in which the numeral co-efficients of the terms
(which, by the law of this feries, are equal to 1 divided
by thefe indexes) are lefs than or it is neceffary
to compute 500 of its terms. Now when t is = r, and
confequently the literal parts of the terms of this feries
do not converge at all, it is evidently neceffary to carry
the computation as far as thofe terms in which the nu-
meral co-efficients of the terms are lefs than ~ or rizzt
in order to get the value of the feries exaft to the th
or T^th part of the radius r, or to the place of thou-
fandths, or the third place of decimal figures. There-
fore, when t is = r, or the arch is =45°, it is neceffary to
compute at leaf! 500 terms of the feries

r

^ 3 r r 5 r* 7 r6 9 r8

11 r

+

l3r

— + + 8cc., in or-
der to obtain the value of it exadf to three places of de-
cimal figures, that is, to the fame degree of exadtnefs to
which we attained In art. 13. by computing only eight
terms of the above-mentioned differential feries. ^.E.D.

Art. 15. But the beft way of applying the aforefaid
differential feries to the inveftigation of the value of one
of thefe very flow feriefes, is to compute a moderate
number of the firft terms of the flow feries in the com-
mon way, and then apply the differential feries to the
3 computation

finding the Value of an infinite Series. 209
computation of its remaining terms. The advantage
of this method of proceeding will be manifeft, if we
apply it to the foregoing example of the feries

+ &c. in the cafe of

an arch of 450.

Compute therefore the firfl: twelve terms of this feries
in the common way. Thefe terms will be as follows :

t

=

r

t 3

r3

_ r

3rr

3rr

~X

t 5

r5

r

5r4

5r4

~*7

t7

r7

r

Jr6

7r*

~ 7

i9

r9

__ r

9r*

9r8

~T

l"

r11

- r

nr10

iirl°

ri

JIL*

r13

r

13^

t's

rIS

_ r

i5r‘4

15 r14

~*5

t 17

r17

__ r

17 r16

i?ri6

~ 17

t' 9

r19

_ r

jgr15

19 r18

19

*ai

r21

r

r x. .090,909,090,909;

2,1 r

^3

2,1 r*

~-~rx .047,619,047,619;

^“■23r“=r3-n .043,478,260,869,

Vol. LXVII.

E e

X.OOO,

2io

Mr. maseres’s Method of

,1 ,7 ,9 f.I

Therefore the twelve terms t- — +-jp-y-5+— .-77^5

<I3 _ ,IS , *1 *1 1 C fll_are

+ l 37-*1 I’jr'6 I9r‘s 2ir10 23*-“

' rx 1. 000, 000, 000, 000, -rx. 333, 333, 333, 333»'
+rx .200,000,000,000,-^.142,857,142,857,
+rx . hi, hi, hi, hi, -rx. 090, 909, 090, 909,
+rx .07 6, 9 23, o 7 6, 923, -rx. 066, 666, 666, 666,
+rx .058, 8 23, 5 29, 41 1, -rx. 05 2, 631, 578, 947,

u +rx .047, 619, 047, 619, -rx. 043, 478, 260, 869, j

X ?

= r x 1.494,476,765,064, -rx .729,876,073,581,

= rx .764,600,691,483.

Having thus found the value of the firft twelve terms

of the feries /-^r+— -•—«-+ -^r- + &c. to be

rx .764,600,691,483, we muft apply the differential

feries to the difcovery of the value of the remaining

part of this feries, which is the feries

r* e1 t" r3 /» Qr

25rl+ 27 r14 29r*8 3ir3° + 33r31 3S''3+"^" 37>"36 cCC.eid

t *

Jinitum . Now this feries is equal to the produdt of -r4 into

the feries

it 1*

tro ,i

+

>»*

25 27 rr 29 3 4 3ir6 33^ 35r‘° 37rxl 397-

+ &c.or

(putting x, as before, = to the product of p-4 into the

feries

finding the Value of an infinite Series , 8tc. h i

* I x xx *3 X* *5 *6 *7 . . r

feries — — — + '^r — ^r+ Sec. which is of
the fame form with the feries a - hx + exx - dx* + ex*-
fx s at6- /6x7 + See. Therefore, if we put a-~,b-

' = rV> £/=rr» e ~ TP /= rr> £ = TP * = tp and fo on> and
compute the differential feries

bx D* xx D«i*s D”**4 D*v*s D**®

DVI*7

^ UA * A 1J" A U A XJ- « ^ ~ ” 0

* i+*~r+riT mv xT^4 i+^15 it?? i+37 KC*
thence refulting, the number thereby obtained will be

the value of the feries +f-J+ &c.

25 27 29 31 33 35 37 39

or

" + '

r" t
: +

39 f

25 27 rr 29r* 3xr6 33^ 3Sr“ 37r

computation is as follows :

Here a is = ^= .040,000,000,000;
b = ^=.037,037,037,637;
f =^ = .034,482,758,620;
d =^=.032,258,064,516;

f = TT = -° 3 0 J 3 0 3>° 3 °> 3 o 3 ?
/ = ^=.028,571,428,571;

g =^=.027,027,027,027;
£ = 3V = .025,641,025,641.

■+ 8cc. This

E e 2

Tlie

a i a Mr. maseres’s Method of

The differences of thefe numbers (beginning from the
fecond number ^ , or .037,037,037,037,) are as fol-
lows :

Firft differences.

•002,553., 278, 416;

.002,224,694,104;

.001,955,034,213;

.001,731,601,731 ;

.001,544,401,544;

,001,386,001,386.

Third differences.

.000,059,924,420;

.000,046,227,409;

.000,036,232,294;

.000,028,800,028.

Second differences.
.000,329,584,311;
.000,269,659,891 ;
.000,223,432,481;
.000,187,200,187;
.000,158,400,1 58.

Fourth differences*.

.000,013,697,010;

.000,009,995,115;

.000,007,432,265.

Sixth, differences,
00.0,00 r, 1 39,044.

Fifth differences..

.000,003,701,894;

.0 0:0,0 o 2, 5 6 2, 8 5 o .

Therefore d1 is = .002,554,278,416;

Dn =-000,329,584,311;
nm =.000,059,924,420;
= .000,013,697,010;
= .000,003,701,894;
= .000,001,139,044...

D

IV —

V _

D

VI —

Confequently the differential feries

a-

bx

T>'XX DJ1*3 D111*4 DVA,<

DVI X7

i + x i + jf i .+ #) 1 H-Ps fTP5 HhP

Sec. is=to

finding the Value of an infinite Series , 8cc.

.040?000,000,000r

- •°37>°37>°37>°37>x-^

- .002,554,278,416, X p

- .000,329,584,311, X ]

AT*

t- .000^059 5 9 2 4^4 2 o , x

# 5

- .000,013,697,010, X "j~^s

„ *6

- .000,003,701,894, X «p-

x7

- .000,001,139,044, X

— Sec.

But, fince t is in this cafe = r, or will be = 1 , and

confequently 7— will be — or i" Therefore the

foregoing differential feries is in this cafe equal to

.040,000,000,000,

•°37>°37>°37>037> x

2

002,554,278,416, x —

oooj3a9Js84?3ii5 x T

I

.000,059,924,420, X Jg
.000,013,697,010, X ^

.000,

214 Mr. maseres’s Method of

- .000,003,701,894, x £

- .000,001,139,044, X

- 8cc. = .040,000,000,000, - .018,518,518,518,

- .000,638,569,604,

: . - .000,041,198,038,

- .000,003,745,276,

— .000,000,428,031,

— .000,000,057,842,

- .000,000,008,898,

— &c.

— .040,060,000,000, - .019,202,526,207, - &c.
' : J' ' = .020,797,47 3,793 - &c.

Therefore the feries ^ + — - — + — + &c. or

25 27. 29 31 33 35 37 39

f/

36

2.5 j2jrr : 29/-* 3ir6+33ra*

3S

37r‘l 39r‘4

— r.+ 8cc. is in this

cafe = .020,797,473,793. Therefore the feries

<**

+ See. is in

‘S’?: ,3?'{ ■ 39

r5

this cafe ^ 4020^97,473,793, that is, to

;^x, 020, 797, 473, 79.3, err* .020,7973473,793; that

is, the remainder of the infinite feries

t — — + f ~ -L-+-L — 8cc. after the firft twelve
3?r 5r 7 r 9r Hr

terms, is ~r x •020,797,473,793. But we before found
7 thofe

finding the Value of an infinite Series , See. i r -

thofe firft twelve terms to be = rx .764,600,691,483.

1 3 f t7 t\

Therefore the whole feries t~— +.— «+

3rr 5^ 7 r

1 ir

8cc. infinitum is in this cafe = r x .764,600,691,483,
+ r x .020,797,473,793, = r x -785,398,165,276,
which is true to eight places of figures, the more exadt
value of that feries being r x -785,398,163,397, 8cc.;
fo that the value here found for this feries, by the help
of only eight terms of the differential feries, differs from
its true value by lefs than an unit in the eighth place of
decimal figures, that is, by lefs than an hundred-mil-
lionth part of the radius r, which is a degree of exadt-.
nefs that could not have been attained by the mere com-

/3 t7 t 9

putation of the feries /-•— +— ; 1+ — - — — 8cc. it-

1 3rr Sr lr 9r i Jr

felf without computing fifty millions of its terms. There
cannot be a ftronger inftance of the utility of that dif-
ferential feries.

Computation of the feries which eUpreJfes the time of the
dejcent of a pendulum through the arch of a circle .

Art. 16. As another example of the utility of the
foregoing differential feries in finding the value of a fe-
ries that converges very flowly, I will now apply it to
the feries which expreffes the time of defeeat of a
heavy body through a circular arch of 90°, which de-

creafes

■a 1 6 ■'Mr. maseres’s Method of

creafes almoft as flowly as the above-mentioned feriesr

; ~7+7~7+7_^+^~7T+ &c,» which expreffes the

magnitude of a circular arch of 45 0 in a circle vrhofe

%

radius is r.

Art. 17. If a heavy body, or a pendulum, be fuppofed
to defcend by the mere force of gravity through any
arch of a circle not exceeding the arch of a quadrant, or
90°; and the motion be fuppofed to begin from a date
of reft, and to continue till the bob of the pendulum, or
the heavy body, comes to the lowed point of the circle;
and the radius of the circle be called r, the perpendicular
height, or verfed fine, of the arch through which the
defcent is made, be called v, and the right fine of the
fame arch be called s; and n be put for the number
1.570,796,326,794, 8cc. which exprefles the lemi-cir-
cumference of a circle whofe diameter is called 1 ; and
the time of the fall of a heavy body through the verfed
fine <y, or the perpendicular altitude of the arch through
which the pendulum defcends, be denoted by v; the
time of the defcent of the pendulum through the faid
circular arch, co'rrefponding to the verfed fine or altitude
v, to the lowed: point of the circle, will be exprefted by

the product of it x — into the feries

1.1 w 1. 1. 3.3 .7* i->-3-3-5-5.y 1 >-i-3 3-5-5-7-7 *>*

2.2 ss 2>2«4*4 j4 2.2.4*4.6.6 / 2. 2. 4.4.6. 6. 8. 8 j8

finding the Value of an infinite Series , Sec. 2x7
_ i-i-3-3-5-5-7:7;9-9_ 8tc. in which the law of

the continuation of the terms is very manifeft,

every new term being derived from the preced-

*1)1)

irig term by multiplying it into the fraction — , and

likewife into a numeral fraction, whofe denominator is
the fquare of the index of the powers of v and s in the
new term, and whofe numerator is the fquare of the odd
number that is lefs than the faid index by an unit.

Art. 18. Let the numeral co-efficients of the terms

j

of this feries be denoted by the capital letters of the
alphabet, a, b, c, d, e, f, g, h, See. in their natural
order, fo that a ffiall be equal to 1, and b ffiall be =

, and c = , and d — 7 > and fo on of the reft.

7 2. 2. 4.4 7 2. 2. 4.4.O. O 7

1. 1

2.2

And we fhall have

0.0 II. II

Ej F, H~

B=SA> C=HB> D=^6C’ E=HD> F-1o.io->

~~ g, and fo on ; and confequently the feries

1. 1 VV 1. 1.2.3 v 4 I.I.q. 2.5.5 V6 o

I- x — + —x-r- — f ‘:xt + &X.

or a

2.2 ss 2. 2. 4.4 r 2.2.4«4.6.6

EVV CV 4 DV6 Ev8 FV10 Gv‘

ss r s s
.6

+ s'

KV

+ 8cc. will be a

1,1, aw 3.3-B‘z;4 5.5.C7;6 7.7 D-y8 9.9. E vl° ii.n.Fi;12 13.13. G7/14

H : .-7 — 7T-+ ctt: — — — — — ttt~ -f

2.2. ss 4.4. s 4 6.6. s(

8.8.

IO.IO. s1Ci 12.12. s':

I2IFV

o IAVV QBi;4 2ZCV6 4Q D*y8 8lE7/c

+ 8cc. or A + Vr- 4t+27- 5 nr + ;

4 ss i6j4 36/ 64 is 100/ 144*

14.14. r-

I69G7/14
I96F4

+ &c. or, if we convert the co-efficients of the terms
into decimal fractions,

Vol. LXVII. Ff t-

,4.1 8 Mr. maseres’s Method of

vv , t>4

i-. 250,000,000,000,* — + .140,025,000,000, X j

v6 v%

-.097,656,450,000, xpr + .074,768,066,406, X jr

V10

-.060, 562, 133, 788, xj^ + .050,889,015,196, x s-

— .043, 878, 793, 714, xjtx + See. The co-efficients of
thefe terms decr'eafe fo flowly (efpecially after the firft
twelve or fourteen terms) that, when the verfed line v is
very nearly equal to the right fine s (as is th e cafe when the
arch through which the heavy body defeends is nearly
equal to 90°, or the arch of a W'hole quadrant of a circle)
it would be neceffary to compute a vaft number of the
terms of the feries in order to obtain its value exadt to
feven or eight places of figures ; and, when v is quite
equal to s (as is the cafe when the arch, through which
the defeent is made, is exadtly equal to 90°) the compu-
tation of the value of the feries to that degree of exadt-
nefs in that diredt manner becomes wholly impractica-
ble. But by the help of the differential feries above-
mentioned its value may be found, even in this cafe, to
that degree of exadtnefs without much difficulty ; more
efpecially if we compute the firft twelve terms of the
feries in the common way, and then apply the differen-
tial feries to the inveftigation of the remaining part of it
in the fame manner as in the laft example. This we
lhall now proceed to do.

5

Art.

finding the Value of an infinite Series , See. 219

Art. 19. The co-efficients of the firft twelve terms of

JAW 9B^4 25CV6 49DI/8 8 1 EVl° 121

the feries a — ^Js + 1^)s4 ^6 s6 ‘ 64^ ioo*1

- giC. are as follows :

196 sl

a = I = i.oo0j00o,ooo?ooo;

B “ 1 —

9E

C = 16" =

2CC

° = -k =

p - i££ .

E_ 64 -

F =
G =

81 E

100

I2IF

144

1690 _
H - 196 -

_ 225 H __

1 - 256 -
_ 2891^ _

324

_ 36 IK
■k 400” "*

M =

44 11
484

*44*

.250,00 0?00 0,000;
.140,625,000,000;
.097,656,250,000;
.074,768,066,406;
.060,562,133,788;
.050,889,015,196;
.043,878,793,714;

•038,5655346,037;

•034,399>336,434;
.03i,045,4°1>I3I;
.028,287,235,328.

.But when v is = s, as it is in the cafe of an arch of 90%
and all its powers will be = 1, and the twelve terms

VV

ss

A-

BVV C if DV® W* TV™ GVXZ H^4 I^16 KV LV‘

SS

+ t* + ,a + ,

,4+V6

+-s— ■

,■* • Si0

F f 4t

will

2,20 Mr. maseres’s Method of

will be equal to their co-efficients a-b + c-d-fe-f + g-
h+ i-k+l-m. Therefore in this cafe the firft twelve
terms of this feries are

1.000,000,000,000, — .250,000,000,000,

+ .140,625,000,000,— .097,656,250,000,

+ .074,768,066,406,- .060,562,133,788,

+ .050, 889, 01 5, 1 96, -.043, 87 8, 793, 7 14,

+ -038, 565,346,037, - .034,399,336,434,

+ -031)045, 40 1, 1 3 1, — .028, 287, 235, 328,
which are =1.335,892,828,770, - .514,783,749,264,
= .821,109,079,506.

Art. 20. The remaining part of this feries is

,*4

OV

7-6

vv °

+ — _

sv

34

TV

3fi

VV

38

s* s s s
23.23-M‘y’4 2$.2<;.NV

°r 24.24. s'*

" -32. f 34 c36

S S S j

16 2h].2h].0V1% 29.29.Pi;30

+ 8cc.

26.26. S26 28.28.J:

30.30.

32.32. J3

3»

33-33-R^4 , 35-35-s-t>36 37-37-™33 «

34.34. V4 + 36-36- 7s 38.38. i3,> + ^c- or

-oa5)979)°75).5oo, x~ - .024,019,115,661 x Jr

vzs

+ .022,334,101,169, x j-t - .020,869,976,759 x pr
+ .019,585,984,048, x pr- .018,450,810,232, x jz
+ .017,440,001,955, X Jr -.016, 534, 1 84,679, X Jj
+ See. ; which is = x the feries

.025,979^07S>500j - .024,019,115,661,

2/2/

+ .02 2:,

221

finding the Value of an infinite Series, See.

+ .0 2 2, 334, 101,169, -^-.0 20, 869,976, 759,^-

*L>5 ty10

+ .oi9,585>984>°48>— -.018,450,810,232,^

+ •oi7,44050oi,9SS>7^--oi6,534,i84,679,~

+ 8cc. or, if we fubftitute x in this laft feries inftead of

VV v1* 1 r •

-- 5 —-t-+ x the ienes

• ° 2 5 >9 7 9»° 7 5 *5 ° °> - .024,019,1 15, 661, x
+ .022, 334, 101,169, xx - .020, 869, 976, 759, xz
+ .019,585,984,048, a:4 - .0 1 8,45 0,8 1 0,2 3 2,a:5
+ .017,440,001,955, a;6 - .0 1 6, 5 34, 1 84, 679, x7
+ &c. Now the value of this laft feries may be difeo-
vered by the application of the differential feries

bx D1 X X T>™X3 D 1 1 1 Ar4 DiVy5 BvX6 Dvl*7

bcc,‘

in the manner following :

> V |

Here a is = .025,979,075,500;
b =.024,019,115,661;
c =.022,334,101,169;
d = .020,869,976,759;
e =.019,585,984,048;

/ =.018,450,810,232;

g =.017,440,001,955;
and h =.016,534,184,679..

Therefore

a22, Mr. maseres’s Method of

Therefore the differences of b, c, d, e, f g, and h, of the

feveral fucceffive orders, are as follows :

Firft differences.

b - c is = .001,685,014,492;
c - d = .001,464,124,410;
d-e =.001,283,992,711;
e-f =.001,135,173,816;
f-g =.001,010,808,277;
g - h =.000,905,817,276.

Third differences.

.000,040,758,383;

.000,031,312,804;

.000,024,453,356;

.000,019,374,538.

Fifth differences.

.000,002,586,131 ;
.000,001,780,630.

Second differences.
.000,220,890,082;
.000,180,131,699;
.000,148,818,895;
.000,124,365,539;
.000,104,991,001.

Fourth differences.

.000,009,445,579;
.000,006,859,448 ;
.000,005,078,818.

Sixth differences.
.000,000,805,501.

Therefore d1 is = .001,685,014,492;

n11 = .000,220,890,082;

nm =.000,040,758,383;
nIV =.000,009,445,579;
Dv =.000,002,586,131;

DVI = .000,000,805,501.
Confequently the differential feries

bx T>1XX D11*3 D111*4 IHv*5 Dv#6 DVI X^

J+* I I I I 4- at5 I + A *S I -f

See. is=to
.025,

finding the Value of an infinite Series.

.025,979,075,500,

- .024,019,115,661, x~

- .001,685,014,492, X ==ji
=■ .000,220,890,082, X

- .000,040,758,383, x

- .000,009,445,579, X -==p

- -000,002,586,131, X

- .000,000,805,501, X

- 8cc.

This is the general value of the faid differential feries,
whatever may be the value of x, or — . But in the cafe
here fuppofed of an arch of 90% the verfed fine v is
equal to the finer; and therefore ~y, or x, is = 1, and

^ or j. Therefore the foregoing differential

feries is in this cafe equal to

- 025>979>°75,S0©>

- .024,019,115,661, x *

- .001,685,014,492, X “

- .000,

Sa4 Afr. maseres’s Method of

- .000,2,20,890,082, X'y

- .000,040,758,383, X 4

- .000,009,445,579, X ~

- .000,002,586,131, X ^

- .000,000,805,501, X

- See. = .025,979,075,500, - .012,009,557,830,

- .000,421,253,623,

- .000,027,611,260,

- .000,002,547,398,

- .000,000,295,174,

- .000,000,040,408,

- .000,000,006,292,

- 8cc.

= .025,979,075,500, - .012,461,311,985, &c.

= .013,517*763,515, - &c. Therefore the feries
a-&x+cxx-dx3+ex4-fx5+gx6-hx',+ Sec., or
.025, 97 9, 075, 500 — .O 24,0 I 9, 1 15, 66l, AT
+ .022, 334,101, 169, ata;- .020, 869, 976, 759, a;3
+ .019,585,984,048, a;4 - .018, 450, 810, 232, a;5
+ .017,440,001,955, a?6 - .016, 534, 184, 679, x7
+ 8cc. is in this cafe = .01 3,5 17,763,5 15, - 8cc.

Therefore x this laft feries, or ^ x the feries

finding the Value of an infinite Series , See. 225

-02.5,979, 07 5,500,- .024,019,1 15,661, jy

* >022, 334, 101,169, ^- .020^869,976,759^

+ •oi9?s85>9^4?°4^ 7 - .018,450,810,232,-^

-+ .017, 440, 001, 955,71- .016,534,184,679,—

4- See. is in this cafe = x .013,517,763,515, - Sec.;
that is, the feries

V1* , , »*«

-.025, 979, 075, 500, ^-.024,019,115,661,^—

T,28 7,20

4 .022, 334,101, 169,7;-. 020, 869, 976, 759,7°

V3*2 V3*

* .019^85, 984, 048, ^-.018,450,810,232., x —
4 .017,440,001,955, ^-.016,534,184,679,^

istt/24' ot;26 pt/28 qjz/3° uu31 s*y34 t^36 vv3S
^ j OF ^24 j26-' j2'& ,^30 ^2 " ^34 ,j36 ’ ^38 oCC. IS

<1)**

in this cafe = x .0 1 3,5 1 7,763,5 1 5, - Sec. = (becaufe
v is in this cafe = s, and confequently -,-+ is - 1)

.013,517,763,5 15, - &c. But we before found the
value of the firft twelve terms of the feries

HW CV4 DV6 EVS

ss + ;4 s6 -i8

F V

+ &x. to be in this cafe =

i8 2 1 , 1 o 95 o 7 9, 5 06. Therefore the value of the whole
ieries a — — + ^ — ^r+— — + ^c* aa infinitum is in

this cafe = .821,109,079,506, + .013,517,763,515,
You LXVII. Gg - &c.

<2 26 Mr. maseres’s Method of

- See. = 834,62,6,843,021, - See. of which the firft
eight figures .834,626,84 are exa<£t, the error being in
the ninth figure 3, which ought to be a 2 inftead of a 3,
as would have appeared if we had computed another
term or two of the differential feries.

Art. 21.
See., or 1-

. _ r . nvv cv*

d E -i/8

F Vxo

bince rue leneb a— ^ t

l.I.AVV 3 3-B^4 5.5 CV6 1 7.7.D^8

*6 + is
9.9.E<yI°

JlvJ

Sec.

2.2 .ss ^ 4.4.J4 6.6. j6 * 8

l0.lO,iiJ

is, in this cafe of an arch of 90°, = .834,626,843, — &:c.,
or fomewhat lefs than .834,626.843, the product of that

feries into tlx — , will be - ttx — x .834,626,843,-Stc^
(becaufe is in this cafe — s) z x r x .834,626,843, -8tc.

= 1 *5 7°>7 965326,7 94, Sec. x r x .834,626,843
— &c. — r h 1. 311,02 8, 77 9, — Sec., or fomething lefs than
rx 1,311,028,779; which is exact to nine places of
figures, the more exact value of this quantity being
r -x 1. 31 1,028,777,146, <kc. as appears by a computa-
tion made by Mr. Stirling, in his admirable Treatife on
the Summation of .Seriefes, p. 5 8.

Art. 22. This value of the product of 1.570,796,

3 2 6,7 94, &c. —into the feries

I.I.-AW 3.3.BT;4 5.5. CV6

2.2. s s ‘ 4.4. s4 6.6. s6

7.7 di;s 9 9.E7;10
SJ.j8 Vo. 10. s'1"'

4- &c., found by

stbe foregoing proceffesin this extreme and moll difficult
.cafe, to wjt, 1.311,028,779, See. x r, exceeds its true

finding the Value of an infinite Series , See. 227
value, 1.3115028,777,146, &c. x r by only .000,000,
002, x r, or two thoufand-millionth parts of the radius
which is indeed a moft minute difference, and thews the
great exadtnefs and utility of this differential feries.

Art. 23. Of the nine figures to which the number
1. 31 1, 028, 779, found by the foregoing procefs,is exadt,
the laft eight are owing to the differential feries. For if
we were to multiply the value of the firft twelve terms

. r . r . BW CZ)* DV6 E V*

only 01 the. lenes a- — 4 — — — + —

J SS / s s

FV

-f 8cCe or

I 1.A.VV Q.'i.BV

X — °

2.2 .SS

4

9.9 EV

+ t0 wit5 the

4 4.r 6.6./ ‘ 8.8. /

number .821,109,079,506', into 7 : x r, or 1.570,796,
326,794, &c. x r, the product would be only 1.289,
See. x r, which is true to only one place of figures, the
fecond figure being a 2 inftead of a 3. This therefore is
an eminent proof of the utility of the faid differential
feries.

Art. 24. In an arch of 90° the verfed fine is equal to
the radius of the circle, that is, according to the fore-
going notation, v is = r. Therefore by art. 17. together
with the foregoing computation, it appears, that the time
of the defeent of a pendulum, or other heavy body
(moving freely from a ftate of reft by the force of
gravity only) through the arch of a whole quadrant
of a circle is to the time of the fall through the cor-

Gg 2

refpondent

228 Mr. maseres’s Method of

respondent perpendicular altitude, or the radius, as
i .31 1,028,779, - x r is to r, or as 1. 31 1,028,779,
- &c. is to 1 .

Art. 25. Hence we may determine the proportion of
the time of defcent of a pendulum through an arch of
90° to the time of its defcent through an infinitely fmall
arch at the bottom of a quadrant, or rather (to fpeak cor-
rectly) to the limit of the time of defcent through a very
fmall but finite arch at the bottom of the quadrant, to
which the faid time continually approaches nearer and
nearer as the faid fmall arch is taken lefs and lefs, and to
which it may be made to approach fo nearly, by taking
the faid fmall arch fufficiently fmall, as to differ from it
by lefs than any given quantity. For this latter time, or
limit, is known to be to the time of the fall of a heavy
body through half the length of the pendulum, or half
the radius of the circle, as the femi-circumference
of a circle is to its diameter, that is, as the number
i-57°j796,326,794, 8cc. is to i. But the time of the
fall of a heavy body through half the radius of the
circle is to the time of the fall through the whole radius
as 1 to s/ a, or 1.414,213, &cc. Therefore, ex tequo, the
faid limit of the time of defcent of a pendulum through
a very fmall arch of the circle at the bottom of the qua-
> drant, is to the time of the fall of a heavy body through

6 the

finding the Value of an infinite Series, Sec. 229
the radius of the circle, or the whole length of the pern
dulum, as 1.570,796, &c. is to 1.414,213, ,&c. But
we have Teen in the laft article that the time of the fall
of a heavy body through the radius of the circle is to
the time of defeent of a pendulum through the arch of
a whole quadrant as 1 to 1.311,028,779,- Sec. There-
fore the limit of the time of defeent of a pendulum
through a very finall arch at the bottom of the quadrant
is to the time of delcent through the arch of the whole,
quadrant as 1.570,796,326, Sec. x 1 is to 1 .414,2 1 3,,
<kc. x 1.3 1 1,028,779, - &c., or as 1.570,796,32.6, 8cc.
is to 1.414,213, Sec. x 1. 31 1,028,779, - See., that is,
by art. 21. as 1.570,796,326, Sec. is to 1.414,213, Sec.
x 1.570,79.6,326, Sec. x .834,626,843, - &c., or as
1 to 1.414,213, &c. x .834,626,843, - Sec., or as 1 to
1.180,340, 8cc., or, in fmaller numbers, as 1 to 1.180,
or as 1000 to 1 180, or as 100 to 1 1 8, or as 50 to 59.

Art, 26. This proportion of the times of the de-
feent of a pendulum through an infinitely fmall arch
at the bottom of the quadrant, and through the arch
of the whole quadrant, agrees pretty nearly with
that afligned for them by Mr. huygens in the pre-
face to his admirable Treadle on Pendulum-clocks,
or De Horologia Of dilator io , which is that of 29 to
34. For 50 is to 59 as 29 25 to 34.2, or 34}; or
(negle&ing the fraction j) as 29 is to 34; Mr. huygens

meaning

230 Afr. maseres’s Method. , &c.

meaning,, probably, in that place, not to exprefs this pro-
portion as accurately as he could, but only as nearly as it
could be expreffed by fmall whole numbers. However,
the numbers 50 and 59 exprefs this proportion rather
more accurately than 29 and 34, and with pretty much
the fame degree of fimplicity, and therefore, upon the
whole, are fomewhat to be preferred to them.

Art. 27.I have endeavoured to find another differen-
tial feries, fimilar to that above defcribed, for the purpofe
of inveftigating the value of an infinite feries of this
form, to wit, a + b x + e ft &+ d-x* + ex* +fxi + g x* + b x~ + &c.
(in which all the terms are marked with the fign+,01
are added to the firft term a ) when the co-efficients b, c,
d, e,f,g, b> &c. decreafe very flowly, and x is very nearly
equal to 1, and the terms of the feries decreafe confe-
quently fo flowly as to make the fummation of it in the
common way, or by the mere computation and addition
of its terms, almoft impracticable ; but my endeavours
have not been attended with fuccefs. I may therefore,
from my own experience, fubferibe to the truth of what
is afferted upon this fubjeft by the very learned and in-
genious Mr. James Stirling in his Treatife, intitled,
Summatio Serierum , p. 17. to Wit, that Series quorum
termini Junt per vices negativi et dffirmativi, funt tttdgis
trhclabites quam alter a, ubi de Summations agitur;
though at firft fight one would be apt to imagine the re-
verie of this propofition to be true.

[ 231 ]

XL Lranflation of a PaJJage in Ebn Younes; with fome
Remarks thereon : in a Letter from the Rev. George
Collat'd, M. A. Vicar of Twickenham, to the. Rev. Sa-
muel Horfley, LL.D. Sec. R. S.

REV. SIR,

T wickenham^
Jan. 9, 1777.

Read Feb. 13, T Ta V1N G, by means of the Royal Society,
1 7 7 7- ff 1

■* been favoured with a tranfcript of the
•Arabic palfage in manufcript of ebn younes, in the
library at Leyden, I now fend you as exa£t a translation
of it as I can. I give it you in Latin, as the former
..tranflations of it were in that language ; and as the num-
bers in the manufcript by no means agree with calcula-
tions made by modern tables, I have ventured to fup-
pofe that they have been fomehow or other altered from
what they were in the original tables of ebn younes. I
have likewife ventured to fhppofe that the prefcnt Ley-
hen copy is a tranfcript of another copy, which is no
very violent ftippofition, confidering how long ago thefe
obfervations have ibeen made, and how long it is face

ebn younes wrote..

: S32 Mr, cost are’s ‘franjlation of

1 have likewise made no fcraple to fuppofe that, how-
ever diftlndt and elegant both the Arabic letters and
-figures are in later manufcripts, they were not fo in thofe
of a more -ancient date, fo that the one might eafily be
xniftaken for the other, where there is a limilarity : and
this miftake would be the more eafily committed by a
perfon ignorant of the fulxjefi: lie was upon. This pro-
bably was the cafe of all fiich as were hired by bookfellers
■ to tranfcribe manufcripts for fale; and for this reafon,
when the tranfcriber had made any mifiake, he would
not blot it out for fear of fpoiling the fale of his book.

There is an inftance of this fort in this very manu-
script in the obfervations of the third eclipfe, which is
iChat. of the Moon, as you will fee in the tranfcript and
•franflation fent you laft year by Mr. schultens.

If what hath been faid be allowed me, as 1 hope it will
not be thought too much, T think I fliall be able to ac-
-eount poffibly, if not probably, for the differences be-
tween the ©bfervations as fet down in the manufcript,
_,and the reful-t of the calculations by modern tables: a
thing which hath not been hitherto attempted, as few
•who have been verfed in aftronomy have been ac-
quainted with the Arabic language; and they on the
other hand, who have well underftood Arabic, have
.been as little converfant with aftronomy.

What

a Pq/Jage in ebn younes. 233

What I have now advanced da all be exemplified under
the firft eclipfe, which is one of the Sun.

In this eclipfe, according to the manufcript, at the be-
ginning, the Sun’s altitude was more than 1 5 (*>) degrees,
and lefs than 16 (*>); aud at the end it was more than
33 degrees (gJ) and j. But I make the Sun’s height
at the beginning 30 (J) degrees, and at the end nearly
36 (V ). In the manufcript, the digits eclipfed are faid to
have been 8 (v, or a> as it is fometimes written) ; but I
make them only a little more than 4(0), or about 4|.

Whether the notation in the original manufcript of
ebn younes was in letters or arithmetical figures is un-
certain ; but moft probably it was in the former of thefe
two, as it is in moft of the tables now extant, though
compofed fince the admiffion and ufe of arithmetical
figures. Upon this fuppofition then, or that they were
fo in the manufcript from whence the prefent manufcript
was copied, we fhall very naturally account for the mif-
takes we find in it.

Thus for inftance, J by fome accidental ftroke at the
bottom, would eafily be taken for <J, as is fometimes
written in manufcripts ; and if the perpendicular ftroke in
the J was made fhort, as in a table it very well might be,
' (.3^) would naturally be taken for rd or (15); and,

Vol. LX VII. H h by

2,34 Afr. costard’s Tranflation of

by the fame rule, ^ (36) would very eafily be taken
for ^ (16); and (4) the digits eclipfed for v which is 8
in the other form of notation, or ^ in this.

In the manufcript it is faid, that the Sun’s altitude at
the end, by obfervation, was a little more than 3 3 (gJ) de-
grees; but this would, in a manufcript ill writen, eafily
be miftaken for<J (35) or j (36).

As to the words, tranllated by Profeflor schultens
for Mr. grischow, “ accidit hoc in piano circuli ejus
“ minus quam 7 digiti,” I am apt to fufpeft they are
nothing more than fome marginal reading crept into the
text; that is, fomebody feeing the digits eclipfed here
made 8 (^), added, as the Arabic will very well bear,
u imo minus quam j (7) or v ( 7 ),” as in the other form
of notation that figure is fometimes made. The writer
of this manufcript, whoever he was, was certainly ac-
quainted with both forms of notation, as he hath made
ufe of both.

This interpretation is at leaf; plaufible, and clears
up a fentence which greatly perplexed both Mr. gris-
chow and Dr. bevis, and feemed to them quite unin-
telligible.

The account given by curtius of the fecond eclipfe,
which was a folar one, is this :

5

Anno

a PaJJcige in ebn younes. 235

Anno eodem, die Sabbati, videlicet, 29 menfis Sywal,
{numero decimi, qui Pafchalis eft eorum) eclipfis Solis
occupavit digitos In principio, Sol altus fere 56°. In
fine, Sol occiduus elevabatur gradibus 26. Ex shickardo
in ms.

This it is plain is not a tranflation of the Arabic, for
that, as tranflatedby schultens for Mr. grischow, and
tranfmitted by him to Dr. bevis, is much fuller, and is
as follows :

ECLIPS IS SOLARIS.

Hsec eclipfis extitit die Sabbati, 29 menfis Siewal, anno
367 Hegirae. Etdies Sabbati hicce ipfe eft dies 9 men-
fis Chordadma, anni 348 Jefdagirdis, et ipfe 8 menfis
Haziran anni 1289 Alexandri, et ipfe eft 14 menfis
Buna, anni Dioclefiani.

Fuitque maximum quod eclipfatum eft de diametro
Solis, 5 digiti et i fuper calculo accuratiore.

Erantque de piano circuli ejus 4 digiti et 1 o minuta.

Et erat elevatio Solis, tempore quo eclipfis incepit, fe-
cundum oculum 56° circiter; et erat integra ejus re-
apparitio cum eflet elevatio ejus 26 graduum, aut circi-
ter; erantque Sol et Luna fimul in hac eclipfi, in pro-

H h 2 pinquo

236 Mr. costard’s ‘Tranjlation of

pinquo difiantise maximae a terra. Deus fcit an calculus
hie bene lit politus. Tempus refpondet diei 8 Jun.
an. Chrifti 978.

Thus far Mr. schultens. And here I mull obferve
that, according to him as well as curtius, the Sun’s al-
titude at the beginning was about 56°, or in Arabic nota-
tion y ; but by computation I make it only about
47° 50* Suppofe it were 47 (/-*}; then where the letters
are fmall and ill made, y and may ealily be miftaken
for each other.

The Sun’s altitude at the end of this eclipfe, according
to both curtius and schultens, was 26° (J) ; but'by
calculation I make it a little more than 36° (p ). But
thefe figures are fo nearly alike that they would eafily
be miftaken by an ignorant tranferiber, and from a ma-
nulcript that was ill wrote.

How schickard, or curtius for him, came to make
the digits eclipfed 7^ I know not: for in the manufeript,
as tranllated by schultens for Mr. grischow above,
we fee they were only 5^ and that fuper calcnlo accura -
tioret or as the Arabic Ihould have been tranllated', juxfa
calculum accuratiorem. The meaning of which, I fup-
pofe, is that ebn younes had found' by calculation that
the digits eclipfed would be 5I, and that at the time his
calculation agreed with his obfervation; as indeed itdid,

for

a Paffage in ebn younes. 237

for I make them about 5|, however widely this differs
from 7y as in curtius.

When the altitude of the Sun, at the beginning of
this eclipfe, is faid to have been 56° or nearly, Jecundum
oculum , it is evident that this was an obfervation.

When it is added, erantque de piano circuit ejus 4 digit!
et 10 minuta , in words at length, it feems to have been
fome interpolation or marginal reading, crept into the
text, as another feems to have done under the former
eclipfe; for if the digits eclipfed here were 5I, agreeable
both to obfervation and accurate calculation , they muft
certainly have been more than 40 1 o'..

At the conclufion of the former eclipfe it was added
in the tranflation, Deus fcit an obfervatio lit bene infti-
tuta; and here the paffage, as tranflated, concludes with
Deus fcit an calculus hie bene fit pofitus. But in the
Arabic, as I have received it, there is no mention made
either of obfervation or calculation. The words are the
fame in both paffages, and are only adjuvante Deo. The
other tranflations feem only to have been what Mr.
GRiscHow collected from profeffor schultens, who, he
fays, was totally ignorant of aflronomical language, as he
himfelf was ignorant of Arabic.

The third is a Lunar eclipfe; and the account given
of it by curtius, from schickard, is this ;

Annoi

:2, 38 Mr. costard’s 'Tranflation of

Anno Chrifti 979. Anno Hegirae 368 (qui incepit
d. 8 Aug. mihi die 9 Aug. anno Chriftiano 97 b) die
Jovis, 14 Sywal, Luna fuit orta cum defedtu, qui ad
digitos accrevit, cum extaret fupra horizontem gradibus
etiam 26 (fubaudio finem tunc accidiffe). schickardus.
Qui adjungit, tempus refpondere diei 14 Maii, anno
Chrifti 979.

The account of this eclipfe, as tranflated by Profeffor
schultens for Mr. grischow, is more particular and
intelligible.

Eclipfis Lunae extitit in menfe Sieval (five Xaval) anno
368 Hegirae. Orta eft Luna eclipfata, in nodie cujus au-
rora fuit feria quinta. Et haec feria quinta fuit dies 2 5
menfis Ijar, anni 1290 Alexandi'i, et ille 20 menfis
Bafchner (five Pachon) anni 695 Dioclefiani.

Spatium quod eclipfatum fuit de diametro ejus, fuit
amplius quam odio digiti, et minus quam novem.

Fuitque hora ortus ejus proxima horae oppofitionis, fe-
cundum fundamenta quibus computare foleo.

Et perfedla eft ejus reapparitio (five finis) cum prae-
teriiflet de nodle (i. e. poft occafum Solis) circiter hora
jufta, et quinta horse pars, prout obfervavi. Et erat Luna,
in hac eclipfi, in propinquo diftantiae fuse mediae.

Tempus refpondet diei 14 Maii, anno Chrifti 979-

With

a Pajfage in ebn younes. 239,

With regard to the time of the oppofition, and the
Moon’s riling at Cairo, there is very little difficulty; for
flie role there at 6h 48' to", and the time of oppofition
was at 6 51 24' 36".

The end of this eclipfe there was at y h 54' 26", and
the time of Sun-fet was at 6h 47' 5 2". The difference is
rh 6/ 1 6",. and agrees very well with the maruilcript.

The paffage, as we have it here in curtius from
schickard, is very obfcure. For it feems either to mean
that when the digits eclipfed were the Moon was 26°
high, or that fhe was 2 6° high when the eclipfe ended.
But I take the laft to be intended; for the Moon was
26° high at 711 36', and the eclipfe ended, as we faw, at
7h 54' 26".

But when schickard or curtius fay this defectus ad
Si digitos accrevit , the meaning mull be that they
amounted only to 5^. But this is not true; for according
to the manufcript, they were between 8 and 9, and I
make them about 8|.

I am apt to fufpect, therefore, that the tranfcriber,
whoever he was, call his eyes on the Solar eclipfe above,
where the digits eclipfed are really 5^, and carelefsly fet
them down to this Lunar eclipfe where they do not be-
long. And to confirm this conjedture it muff be ob-
ferved, that after the word Dioclefian under this Lunar
eclipfe,, in the Arabic follow fix lines, which are a repe-
tition

240 Mr. costard’s Translation of

tition of all that was faid cinder the laft folar eclipfe,

from the fame word Dioclejian to the end of that obfer-

vation.

I fhall now, in the laft place, give you a tranflation of
the Arabic paflage intire, omitting however the interpo-
lations mentioned above, which embarrafs the whole.

Infit AH IBN ABDORRAHMAN, IBN ACHMED, IBN
YODNES, IBN ABDOL’ AALI.

Imprimis, jam commemoravi eclipfes, tarn Solares
quam Lunares, quas obfervarunt viri dodti; eruditi ii
quorum nomina recenfui, quafque ad eos retuli, incipi-
endo ab audtoribus libri di<fti almomtahen, ufque ad
filios Majour; quin et conjundtiones eorum cum ftcllis
fixis, quas obfervarunt, et quorum loca commemorarunt,
■et invenerunt, tempore conjundtionum eorum.

Ipfe deinde memorabo eclipfes quas obfervavi, tam
Solares quam Lunares, et conjundtiones cum ftellis fixis,
et quaenam fuerunt formas eorum in conjundtionibus
fuis. Ut quicunque me fequantur, et indicia habere defi-
derent, meis utantur, quemadmodum ac ego eorum in-
diciis et diredtionibus ufus fum, qui ante me obfervarunt.
Deus autem adjutor eft.

Eclipfis Solaris erat priore parte diei, feria quinta, die
decimo odtavo menfis Rabiae pofterioris, anno Hegiras

367.

a PaJJage in ebn younes. 241

367. Et hsec feria quinta erat dies decimus fecundm
meniis Adzermah, anno Yezdagerdis 346.

CarafKe adfuimus, in templo abi gaafari achmed
ibn nasar Africani, coetus eruditorum, ad hanc elipfin
obfervandam. E quorum numero erat haroun ibn ivlo-

HAMMED AL GAAFARI, et ABU ABDALLAH AL HOSEIN IBN

nasar Africanus, et abul’ hosein ali ibn mahar-
bacht Perfa, et abijl’ abas achmed ibn achmed al

CHURGII, et ABU ACHMED ASSUMACHI, et ABU OMAR

Scriba.

Ex his, prseter alios eruditos cum reliquis obfervatori-
bus, nonnulli erant aftronornice dodlL

Ipfe quoque eodem contendi, una cum abul’ kasem
ABDORRAHMAN IBN HOSEIN, IBN TISAN, AL IDAS, et HO-
SAN IBN AL DARANI, et HAMED IBN AL HOSEIN.

Et hi omnes initium hujus eclipfeos obfervarunt, quae,
ad fenfum meum, apparere incepit foie plus quam gra-
dibus 15, minus autem quam 16 elevato.

Omnes quoque praefentes opinione confentierunt ob*»
fcurari de diametro ejus circiter 8 digitos.

Ai v'r

U' v ^ '4'

Et fplendor ejus perfedte recuperatus eft cum eleva-
retur amplius quam gradibus 33 cum tertia fere parte,
prout ipfe menfuravi ; omnibus qui aderant confentien-
tibus.

Vol. LXVII. li la

242 Mr. costard’s T ranfiation of

In hac eclipfi, Sol et Luna fimul erant non longe a
diftantia fua proxima a terra. Adjuvante Deo.

ECLIPSIS SOLARIS.

Hsec eclipfis incidit in diem Sabbati, diem 29 menfis
Shuwal, anno Hegirae 367. Eratque hie dies Sabbati,
dies 9 menfis Chordadmah, anno Yezdagerdis 347, et
dies 8 menfis Haziran, anno Alexandri 1289; et infu-
per dies 14 menfis Bounah. anno Dioclefiani 694.

Maximum quod obfeuratum eft de diametro folis erat
Si digiti.

\</

V

Et quando hcec eclipfis, ad oculi aciem, jam incepifle
conftabat, Solis altitudo erat circiter gradus 56, et lucis
ejus reftitutio completa eft cum altitudo ejus eflet 26
gradus, vel circiter.

Erantque Sol et Luna fimul, in hac eclipfi, prope dif-
tantias fuas maximas a terra. Adjuvante Deo.

ECLIP'SIS LUNARIS.

Hcec contigit menfe Shuwal, anno Hegirae 368. Orie-
batur Luna, eclipfi jam inchoata, nodte cujus Aurora
erat feria quinta, quee feria quinta erat dies 28 menfis
Ardbaheft, anno Yezdagerdis 348, quae fuit 18 menfis

Ijar

a PaJJage in ebn younes. 2,43

Ijar, anno terse Alexandri 1290. Eratque dies 20 men-
fis Bifhnis, anno Dioclefiani 698.

at at at

V

Eratque quantitas diametri ejus obfcurata, plufquam
digiti 8, et minus quam novem. Tempufque ortus ejus
erat prope tempus oppoiitionis, juxta fundamenta quibus
computavi : lucemque plenam recuperavit cum de nodle
praeteriiffet hora circiter sequinodtialis, cum quinta parte,
prout ipfe conjedtavi.

Eratque Luna in hac eclipfi, haud procul a diftantia
fu& media a terra. Adjuvante Deo.

This I hope will be fufficiently fatisfadtory.

I am, &c.

I i a

[ 244 1

XIII. Obfervations on the Annual Evaporation at Liver-
pool in Lancalhire; and on Evaporation considered as a
! Eejl of the Moifture or Drynefs of the Atmofphere. By
Dr. Dobfon of Liverpool. Communicated by John
Fothergill, M. D. F. R. S.

Read Feb. 13, f g *HE quantity of rain which falls during

the courfe of the year, is a very un-
certain teft of the moifture or drynefs of any particular
ffeafon, fituation, or climate. There may be little or even
no rain, and yet the air be conftantly damp and foggy ;
or there may be heavy rains, with a comparatively dry
ftate of the atmofphere. The fame depth of rain will
likewife produce different effects on the air, according as
it falls upon a flat or hilly country ; for large quantities
foon quit the hills or high grounds, while fmaller quan-
tities have more falling and powerful effects on a flat
country. Much alfo depends upon the nature of the
foil, whether clay or fand, whether firm and compact, or
loofe and fpungy.

Is not evaporation therefore a more accurate teft of
the moifture or drynefs of the atmofphere, than the
quantity of rain ?•

It

Dr. dobson’s Obfervations , 8cc. 245

It is well known, that air is an active folvent of water,
and that its powers of folution are in proportion to its
drynefs. It is likewife well known, that in chemical fo-
lutions, the action of the menjiruum is greatly promoted
by heat and agitation. If the temperature of the air
then, and the ftate of the winds, be afcertained, which
in the prefent cafe denote the heat and agitation of the
menjiruum , the evaporation will be the true index of the
drynefs of any particular feafon, lituation, or climate.

To determine the annual evaporation in the neigh-
bourhood of Liverpool, I procured two weli-varnifhed
tin veffels; one of which was to ferve the purpofe of a
rain-gage; the other was to be employed as my evapo-
rating veffel. The evaporating veffel was cylindrical,
twelve inches in diameter and fix inches deep. The
rain-gage confiHed of a funnel twelve inches likewife in-
diameter, the lower end of which was received into the
mouth of a large ftone-bottle ; and, to prevent any eva-
poration from the bottle, the pipe of the funnel wras
Hopped with a grooved cork. Thefe veffels were placed
in the middle of a grafs-plot, on a riling ground adjoin-
ing and immediately overlooking the town, about fe-
venty-five feet above the level of the fea, and with a free
expofure to the Sun, winds, and rain. The cylindrical
veffel was filled with water within two inches of the

7,4*5 Dr. dobson’s Obfervations on

top; and if, in confequence of heavy rains, there was
danger of its overflowing, a quantity of water was taken
out; but if, in confequence of long drought, it funk
lower, a quantity of water was then occalionally added;
and thefe additions or fubtraftions were carefully re-
gistered. At the end of every month, the depth of rain
was firft calculated ; and, as each veflel received the fame
depth of rain, I had only to examine the quantity of
water which had been added to, or taken out of, the eva-
porating veffel, and the evaporation of the month was
afcertained.

The first column of the following tables points out
the mean temperature of the air at two in the afternoon.
The fecond, the character of the month with refpedt to
the winds, the number of dots exprefiing their trength ;
and, to make this part tolerably accurate, daily obferva-
tions on the winds were marked down, and the character
of the month formed from a general furvey of thefe ob-
fervations: our winds are Wefterly for near two-thirds
of the year. The third column points out the evapora-
tion of each month in inches and decimal parts of an
inch. The fourth, the depth of rain during each month.
And the fifth, the Hate of the feafons, e being prefixed
to the evaporation of the whole three months, r to the
I'ain, and t to the mean temperature. i

It

the Annual Evaporation at Liverpool, See. 247
It is to be obl'erved, that in making thefe experiments,
251 grains were allowed for every cubic inch of water;
and that three pounds and twelve ounces of water give
a depth of one inch on a circular area of twelve inches
diameter.

table 1.

A comparative view of the evaporation, rain, winds, and
temperature of the air, during the year 1772.

Months.

Temp.

Winds.

Evaporat.

Rain.

Sealons.

January

38

• • •

1.27

3.26

|E. 4.87

February

39

• • • •

1.25

2-3S

rR- 7-2 3

March

44

2*35

1.62

' T. 40.

April

48

2.53 .

1-85

'j E. II 40

May

57

•

4-25

3-42

U. 839

June

67

4 ^2

3.12

J T. 57.

July

70

5-53

1 59

E. 13.2O

Auguft

68

5-35

3-65

l R. 1 1.29

September

62

2,32

6.05

J t. 66.

O&ober

60

3-lS

3-42

E. 6.46

November

50

0 • •

2.15

4-85

l R. IO.48

' December

44

l''3

2.21

J T- 51*

54

35-95

37-39

TABLE

248 D/\ dobson’s Obfervations on

T A B L E II.

A comparative view of the evaporation, rain, winds, and
temperature of the air, during the year 1773.

Temp.

Winds.

Evaporat.

Rain.

Seafons.

January

44

• • • •

1.85

3*z5

1

|e. 5*74

February

42§

. . .

2-37

1

R. 6.17

March

50

• • •

2.76

0.65

J

T. 45.

April

54

• • %

2 89

2.47

]

E. 9.34

May

57

• •

3- 79

456

1

JO

00

bo

June

641

2.66

1.42

j

T. 58.

July

67

t •

4.92

i-32

1

| E. I4.O2

Auguft

70

5*75

2.21

Ir. 10.08

September

60

• •

3-35

6.55

1 T. 65.

October

55

• • •

2.79

4*57

I E- 5*49

November

47 i

6.69

JO

»

KH

bi

OO

December

4*i

. . .

i-55

4*32

| T. 48.

54l

34-59

40.18

TABLE

the Annual Evaporation at Liverpool, See. <*49

TABLE III.

A comparative view of the evaporation, rain, winds, and
temperature of the air, during the year 1774.

Temp.

Winds. JEvaporat.

Rairn

Seafons.

January

37

a a. a

1.38

443

Se. 592

February

45t

• • a a.

1.67

2.42

j R. 8.23,

March.

49t

a • •*>

2.87

1.38

' T. 44,

April

54i

a • •-

4-56

2.23

1 e. 12.39

May

S9l

a » a

4-31

1.65

U- 7*I4.

June

63

3*52

3.26

>

J t. 59;

Ny

66|

a a a

4-97

2.68

•j e. I3-51

Auguft

67

4-52

2-36

l r. icu$6

September

6 i-l:

4.02

S-52

J t. 65.

0£lobr

57

i*95

1.68

E. 4,82

November

46!

® • a

1.12

2.69

l R. 6.00

December

4i|

1.63

J T. 48I.

54

3664.

1 31 93

1

I

K k

Vo l. LXVIL

TAB L E

Dr. dobson’s Obfervatlons on

£50

TABLE IV.

A comparative view of the evaporation, rain, winds, and
temperature of the air, during the year 1775.

|Temp.

Winds.

Evaporat.

Rain.

Seafor.s.

January

C *

441

", , ,

* *3.21

] E. 7.IO

February

49

....

3.02

4.62

r r. 10.28

March

48!

• • +

2.57

’ '2-45

' T. 47 f.

April

571

• • •

3.21 *

I.OI

] E- 15-09

May

61

...

5.02

'0.85

fR- 3-98

June

702

♦ • •

6. 86

2.12

J T.63.

July

681

5-03

1 E. I2.5O

Auguft

66 1

4.42

4.26

i R. 12.57

September

6 5

# *

3 °5

4 00

J T. 56J.

October

541

• • •

2.12

7.01

j E* 5-27

November

45

I »

1.63

3-°3

.R. 13.39

December

48J

1*52

3*35

. T. 49J.

54

-39 96

40.22

OBSERVATIONS.

I. It is evident from thefe tables, whether we attend
to feparate months, feafons, or years, that the depth of
rain is a very erroneous index of the moifture or drynefs
of the atmofphere. On comparing the two months July
and Auguft of the year 1772, it appears that the tem-
1 perature

the Annual Evaporation at Liverpool, 8cc. 251
perature of the air, the ftate of the winds, and the eva-
poration, were nearly the fame during thefe t wo months,
and yet the rain of Auguft was more than double that of
July. The reafon why the greater quantity of rain had
no more effect than the fmaller in adding moifture to
the atmofphere, is obvious ; for on confulting my regifter
I find, that the rain of Auguft fell in heavy fhowers, and
ran off the ground before it could be evaporated ; while
that of July, falling in fmall drizzling fhowers, gave
more time for its evaporation.

Again, the temperature of the air, the ftate of the
Wrinds, and the evaporation, were nearly the fame during
the firft three months of the year 1773, with what they
were during the laft three months of that year; the ftate
of the air therefore, with refpedt to moifture and dry-
nefs, muft have been the fame during thefe two feafons ;
and yet the depth of rain, in one of thefe feafons, was
much more than double what it was in the other. If
we attend to whole years the fame obfervation is con-
firmed. The rain of 1775 exceeded the rain of 1774
more than eight inches; and hence it might he con-
cluded, that the atmofphere was more moift in 1775
than in 1774; the reverfe of this, however, is found to be
the fa£t : for there evaporated from a conftant and deter-
minate furface of water in 1775, full three inches more

K k 2 than

■z 5 a Dr. dobson’s Obfervations on

than evaporated from the fame furface of water in 1774.
Confequently the drynefs of the atmofphere or its power
of folution, during the year 1775, exceeded that of
1774-

2. If we take the medium of four years obfervations
it appears, that the annual evaporation at Liverpool
amounts to 36.78 inches.

Dr. halley obferved at London, that water placed in
a clofe room, where neither the winds or Sun could act
upon it, exhaled only eight inches during the whole
year. He makes no doubt but that the free accefs of the
winds would have trebled the quantity carried away;
and that this again would have been doubled by the
alliftance of the Sun. Dr. halley, therefore, fixes the
annual evaporation of London at 48 inches (a) . If this
calculation be admitted, it follows, that the annual eva-
poration of London exceeds the annual evaporation of
Liverpool 1 1 inches ; but were the experiments to be
made in London, in the fame cii'cumftances with thofe
made at Liverpool, it is probable, that this would be
found to be more than the real diffei'ence.

The learned cruquius obferved at Delft in Holland,
that there exhaled from water fet in the open air, but in
a calm and fhady place, about 30 inches; and it is not to

(a) Phil. Tranf* N° 21 2*

be

the Annual Evaporation at Liverpool, fee. 253
be doubted, fays Dr. brownrigg in his very valuable
work, The Art of making common Salt , but that double
this quantity, or 60 inches, would have exhaled, had it
been placed where the Sun and winds could have had
their due effects fiJ. In another part of this publication,
Dr. brownrigg fixes the evaporation of fome parts of
England at 7 3.8 inches during the four fummer months,
May, June, July, and Auguft; and the evaporation of the
whole year at upwards of 140 inches/^. Thefe are cal-
culations, however, which do not appear to correfpond
with experience ; for the whole evaporation at Liverpool,
inftead of 140 inches, was only 36.78 inches. The eva-
poration likewife of the four fummer months, on a me-
dium of four years, inftead of 7 3 inches, was only 18.88
inches.

3. Dr. hales calculates the greateft annual evapora-
tion from the furface of the earth in England, even that
from a furface of hop-ground, at 6.66 inches'^. If we
compare this with the annual evaporation from a furface
of water as determined by experiment, we find, that the
latter exceeds the former about 30 inches; and that the
annual evaporation from a furface of water, is to the an-
nual evaporation from the furface of the earth in this
part of England, nearly as 36 to 6, or as 6 to x.

(b) Page 185. (c) P. 1S9.

(d) Veg. Stat. vol. I. p. 55, 56,

4. Oil

254 Dr' dobson’s Obfervatiom on

4. On comparing the depth of rain with the annual
evaporation of this part of Lancafhire we find, that more
falls in rain than is raifed in vapour, even though the
whole were a furface of water; for the rain is to the
evaporation as 37.43 inches to 36.78 inches: and we
farther find, that the quantity exhaled from the furface
of the earth is little more than a fixth part of what de-
fcends in rain ; we muft therefore have very large fup-
plies from other regions, from the furrounding fea, and
from the ocean of warmer climates. Hence we fee, why
our South and South -weft winds are fo often accompa-
nied with rain ; for as the air fweeps along the warmer
latitudes, it involves a large proportion of moifture,
which is conftantly and copioufly exhaling from the
ocean ; and this moifture being retained in a ftate of fo-
lution till it reaches the colder climates, is then either
collected in clouds or immediately precipitated in rain,
according to the different conditions of the atmofphere.

Thefe foreign fupplies, however, are uniformly re-
ftored to the fources from which they were derived : for
that proportion of rain which rifes not in vapour, after
moiftening and refrefhing the earth, forms fprings,
"brooks, and rivers, and is thus perpetually returning to
the ocean whence it was taken; fo truly philofophical are
the words of the preacher when fpeaking of this vaft

circulation ■:

the Annual Evaporation at Liverpool, Sec. 255
circulation : “ All the rivers run into the fea, yet the fea
“ is not full: unto the place from whence the rivers
“ come., thither they return again.”

5. About a century ago, the ingenious Mr. townley,
of Townley in this county, made fome accurate obferva-
tions on the depth of rain which fell annually in the
neighbourhood of the hills which divide Lancafhire and
Yorkfhire; and on taking a medium of fifteen years, he
determines it to be 41 .5 1 6 inches^. The depth of rain,
therefore, at Townley exceeds the depth of rain at Liver-
pool about four inches. This is probably, however, lefs
than the real difference ; for there was a fource of error
in Mr. townley’s experiments with which the world was
not at. that time acquainted. Mr. townley’s rain-gage
was fixed full ten yards above the furface of the earth \
which circumftance, according to fome later obferva-
tions, makes a very material difference in the refult of
the experiment^. Were the obfervations to be repeated
at Townley, and the rain-gage placed upon the ground,
there can be no doubt but that the depth of rain would
confiderably exceed 41.516 inches; for I find from a
great number of experiments, made during the laft three

(e) Phil. Tranf. abridged by Lowthorp, vol. II. p. 46. (/) Ibid.

(g) Phil. Tranf. vol. LIX. art, 47.

rears

* ^

256 Dr. dobson’s Obfer vat ions on

years with two veffels of equal dimenfions, one placed ort
the ground, and the other eighteen yards higher on the
battlement of the hofpital ; that the quantify received in
the lower veffel exceeds that in the higher more than
one-third and lefs than one-half.

6. An ingenious friend, on perufing thefe obferva-
tions, alked, “ Whether the fad: of evaporation going on
u equally well in an exhaufted receiver, was not an un-
“ furmountable objection to that theory concerning eva-
u poration, which fuppofes a chemical folution of water
M in air?” With a view to afcertain this fad. I made the
following experiment.

Two china faucers, each containing three ounces of
water, were accurately weighed. One of them wa3
placed in the open air ; the quickfilver in. the thermo-
meter Hood duiing the experiment between 48° and 50°,
the day tolerably clear with a moderate breeze. The
other was put under the receiver of an air-pump; the air
was exhaufted, and the piftons occafionally worked, to
draw off any of the water which might be fuppofed to
be converted into vapour. After four hours the faucers
were again accurately weighed; that in the open air had
loft one drachm and eight grains; the weight of the
other was not lcnfibly dimin.iihed,

Froni:

the Annual Evaporation at Liverpool, Sec. 257
From this experiment it appears, that air is a chemi-
cal folvent of water, and as fuch is undoubtedly to be
confidered as one caufe of the evaporation of water.
Heat is another caufe of evaporation, and when raifed
to a fufficient degree may produce this effect with-
out the intervention of air, and the evaporation confe-
quently go on copioufly in an exhaufted receiver, agree-
ably to the experiments of the ingenious Dr. irving^.

The following obfervations are added as a farther il-
luftration of this fubjed. W ater may exift in air in three
different ftates. 1. In a ftate of perfect folution. 2. In
a ftate of beginning precipitation. Or, 3. Completely
precipitated, and falling in drops of rain.

In the firft inftance, where the water is in a ftate of
perfed folution, the air is clear, dry, heavy, and its
powers of folution ftill adive, though it already contains a
confiderable proportion of water. In the fecond, the air
becomes moift, foggy, its powers of folution are dimi-
nifhed, and it becomes lighter in proportion as its water
is depofited. It is a Angular and well-attefted fad, that it
never rains in the kingdom of Peru ; but that during part
of the year the atmofphere is conftantly obfcured with

(i) Phipps’s Voyage to the North Pole, p, 21 1.

Vol. LXVII. L 1 vapours,

2, 5 8 Z)r. Dobson’s Obfervations on

vapours, and the whole country involved in what they

call Gamas , or thick fogs (,J.

It is not necefiary to point out the caufes which thus
difpofe the air to depofite its diflblved water ; nor to con*
fider with what bodies air hath a Stronger affinity than
with water; neither to inquire how far the electrical fluid
is engaged in the procefs. It is fufficient to obferve, that fo
long as thefe caufes have a general aCtion on the air, they
diminifh its power of folution,and give a damp and foggy
ftate of the atmofphere; that when they operate fora con-
fiderable proportion of the year, they produce a moift
climate ; and that when they more generally do not, and
the air retains its moifture in a ftate of perfedt folution,
the climate is dry. Confequently, that the moifture or
drynefs of a climate, do not fo much depend upon the
abfolute quantity of water which is contained in the air, as
upon the air being in a ftate of perfect or imperfeCt folu-
tion. During long continued fummer droughts, a very
large proportion of water is diffolved in the air; notwith-
standing this, the air is ftill dry, and continues to be fo as
but as the water remains in a- ftate of perfect folution;
long no fooner are the powers of folution diminished,
than what was before a dry, now becomes a moift climate.

(i) D’Ulloa’s Voyage to South America, vol. II. p. 69.

In

the Annual Evaporation at Liverpool, Sec. 259
In the third inftance, the diffolved water may be
either flowly precipitated and fall in drizzling rain, or it
may be more powerfully difcharged in brilk rain; or
there may be partial and fudden precipitations from par-
ticular regions, while other parts of the atmofphere ftill
retain their water in a ftate of perfect folution. Heavy
thunder-fhowers are the mold remarkable inftances of
partial, fudden, and copious precipitations.

Liverpool, Nov. 20, 1776.

l 1 2

/

[ a6o ]

XIV. An Account of Perfons who could not dijlinguijh Co-
lours. By Mr. Jofeph Huddart, in a Letter to the Rev.
Jofeph Prieftley, LL.D. F . R. S.

SIR,
Read Feb

*777

London,
Jan. 15, 1777.

?eb. i3,"f T J HEN I had the pleafure of waiting on
* * you laft winter, I had hopes before now
of giving you a more perfect account of the peculiarity
of vifion which I then mentioned to you, in a perfon of
my acquaintance in the North: however, if I give you
now the belt I am able, I perfuade myfelf you will par-
don the delay.

I promifed to procure you a written account from the
perfon himfelf, but this I was unfortunately difappointed
in, by his dying fuddenly of a pleurify a fhort time
after my return to the country.

You will recollect I told you that this perfon lived at
Mary-port in Cumberland, near which place, viz. at Al-
lonby,I myfelf live, and having known him about ten years
have had frequent opportunities of converting with him..

7 His

"Mr. huddart’s Account of. , See. 261

His name was Harris, by trade a fhoe-maker. I had
often heard from others that he could difeern the form
and magnitude of all objects very diflindlly, but could
not diftinguifh colours. This report having excited my
curiolity, I converfed with him frequently on the fub-
jedl. The account he gave was this : That he had reafon
to believe other perfons faw fomething in objects which'
he could not fee; that their language feemed to mark,
qualities with confidence and precifion, which h© could,
only guefs at with hefitation, and frequently with error.
His firft fufpicion of this arofe when he was about four
years old. Having by accident found in the ftreet a
child’s Hocking, he carried it to a neighbouring houfe to
inquire for the owner : he obferved the people called it
a red flocking, though he did not underfland why they
gave it that denomination, as he himfelf thought it com-
pletely deferibed by being called a flocking. The circum—
fiance, however, remained in his memory, and together
with fubfequent obfervations led him to the knowledge
of his defedl. As the idea of colours is among the firft.
that enters the mind, it may perhaps feem extraordinary
that he did not obferve his want of it 'ft ill earlier. This, ,
however, may in feme meafure be accounted for from
the circuroftance of his family being quakers, among

whonu

a 6 % Mr. hud dart’s Account of

whom a general uniformity of colours is known to pre-
vail.

He obferved alfo that, when young, other children
could difcern cherries on a tree by fome pretended dif-
ference of colour, though he could only diftinguifh
them from the leaves by their difference of fize and
fhape. He obferved alfo, that by means of this difference
of colour they could fee the cherries at a greater diftance
than he could, though he could fee other objects at as
great a diftance as they ; that is, where the fight was not
aflifted by the colour. Large objects he could fee as well
as other perfons; and even the fmaller ones if they were
not enveloped in other things, as in the cafe of cherries
among the leaves.

I believe he could never do more than guefs the name
of any colour ; yet he could diftinguifh white from black,
or black from any light or bright colour. Dove or ftraw-
colour he called white, and different colours he fre-
quently called by the fame name : yet he could difcern a
difference between them when placed together. In ge-
neral, colours of an equal degree of brightnefs, how-
ever they might otherwife differ, he frequently con-
founded together. Yet a ftriped ribbon he could diftin-
guifh from a plain one ; but he could not tell what the
colours were with any tolerable exadlnefs. Dark colours
3 in

Perfons who could not dijlinguifh Colours. 263
in general he often miftook for black, but never ima-
gined white to be a dark colour, nor a dark to be a white
colour.

He was an intelligent man, and very defirous of un-
derftanding the nature of light and colours, for which
end he had attended a courfe of lectures in natural phi-
lofophy.

He had two brothers in the fame circumftances as to
light ; and two other brothers and lifters who, as well as
their parents, had nothing of this defeat.

One of the firft mentioned brothers, who is now liv-
ing, is mafter of a trading veflel belonging to Mary-
port. I met with him in December 1776, at Dublin,
and took the opportunity of converting with him. I
wilhecl to try his capacity to diftinguifh the colours
in a prifm,, but not having one by me, I afked him,
Whether he had ever feen a rain-bow ? He replied, He
had often, and could diftinguifh the different colours ;
meaning only, that it was compofed of different colours,
for he could not tell what they were.

I then procured and Ihewed him a piece of ribbon :
he immediately, without any difficulty,, pronounced it a
ftrlped and not a plain ribbon. He then attempted to
name the different ftripes: the feveral ftripes of white
he uniformly, and without hefitation, called white : the
four black ftripes he was deceived in, for three of them

he

-264 Mr, hudd art’s Account of

he thought brown, though they were exactly of the fame
fhade with the other, which he properly called black.
He fpoke, however, with diffidence as to all thofe ftripes;
and it muft be owned, the black was not very diftindt: the
light green he called yellow ; but he was not very pofi-
tive : he faid, “ I think this is what you call yellow.”
The middle ftripe, which had a flight tinge of red,
he called a fort of blue. But he was molt of all deceived
by the orange colour; of this he fpoke very confidently,
faying, “ This is the colour of grafs; this is green.” I
alfo fhewed him a great variety of ribbons, the colour of
which he fometimes named rightly, and fometimes as
differently as poflible from the true colours.

I afked him, Whether he imagined it poflible for all
the various colours he faw, to be mere difference of light
and fhade ; whether he thought they could be various
degrees between white and black; and that all colours
could be compofed of thefe two mixtures only? With
Tome hefitation he replied, No, he did imagine there
was fome other difference.

I could not conveniently procure from this perfon an
account in writing; but I have given his own words,
having fet them down in writing immediately. Befides,
as this converfation happened only the 10th of laft

month

Per/ons who could not dijlinguijh Colours . 265

months, it is Hill frelh in my memory. I have endea-
voured to give a faithful account of this matter, and not
to render it more wonderful than it really is.

v IC 1S ProPer t0 add, that the experiment of the ftriped
ribbon was made in the day-time, and in a good light.

I am, sir, 8cc,

Vol. LXVII.

M m

[ 266 ]

XV, Anew 'theory of the Rotatory Motion of Bodies affeBed
by Forces dijlurbing fuch Motion. By Mr. John Lan-
den, F. R. S.

Read Feb. 20, T am induced to conlider this paper as
1777. 1

not unwoithy the notice of this Society,,
through a perfuafion that the theory herein contained
will conduce to the improvement of fcience, by enabling
the reader to form a true idea, and accordingly to make
a computation of the motion (or change) of the axis about
which a body having a rotatory motion will turn, or have
a tendency to turn, upon being affeCted by a force dif-

■ ■y' . *

turbing its rotation; particulai'ly of the motion of the
earth’s axis arifing from the attraction of the Sun and
Moon on the protuberant matter of the earth above its
greateffc infcribed fphere: which compound motion* I
conceive, has not been rightly explained by any one of
the eminent mathematicians whofe writings on the fame
fubjeft have come to my hands. Whether in this elfay
I have really fucceeded better than other writers who
have attempted an explanation of fuch motion, I fubmit
to gentlemen well verfed in mechanics to determine.

1. Fig.

Mr. landen’s new 'Theory, See. 267

1. Fig. 1 . Let the fphere adbe, whofe radius is r, re-
volve uniformly about the diameter acb as an axis, with
the angular velocity c , meafured at d or e, the motion
being according to the order of the letters dgeh in the
fe&ion at right angles to acb, fig. 2. ; and, whilft it is fo
revolving, let the pole a be impelled by feme inftan-
taneous percuflive force to turn about the diameter dce,
from a towards h, with the velocity w. It is propofed to
find the new axis about which the fphere will revolve
after receiving fuch impulfe.

Calling al , parallel to DC, x; cl will be : the

velocity of the point a (about acb) before the impulfe

on a will be = — ; and the velocity (about dce) given
to the fame point (<3) by the faid impulfe will be =

~~V% . Which velocities of the point a being in con-

trary directions, if it be fo fituated that they be equal,
then, one deftroying the other, that point will flop and
become one of the new poles fought, about which the for-
mer poles a and b will revolve with the velocity w ; and the
points d and e will revolve with the fame velocity (c) as
before the perturbating impulfe on the point a ; but in-
llead of deferibing the great circle dgeh, their motion
will be about the new axis ah; about which they (as well
as the points a and b) will deferibe lefler circles parallel

M m 2

<268 Mr. landen’s new 'Theory of

to the great circle de , in which the points d and e (de

Being at right angles to ab) will revolve about the fame

axis ( ab ) with the velocity Vc2+ wr. Which being de-
noted by e , and m and n being put for the fine and cofine
of the angle Aca to the radius i, me will be = w, ne = c,
and confequently mne" — cw.

Now taking — = w'^r — , in order to- find that new

axis ah, we have from that equation x— r—-ah

Moreover it is obvious, that if a fpheroid, a cylinder,
or any other body, whofe center of gravity is c and pro-
per axis acb, were, whilft revolving about that axis with
the fame angular velocity (r), to receive fuch an impulfe
as inftantly to give the point a the angular velocity w
about dce ; the axis about which that fpheroid, cylinder,
or other body, immediately after the impulfe, would re-
volve, or would have a tendency to revolve, would be
the fame line ab.

The great circle de (fig. i.) and any other great circle
fo fituated with refpedt to the axis of any revolving
fphere, I fhall denominate the mid-circle.’

2 . In the manner above deferibed the polesof the fphere
are by the iriftantaneous impulfe on the point a inftantly
changed from a and b to a and b. But if, inftead of fuch
impulfe, a continued attractive force f (like that of gra-
vity)

the Rotatory Motion of Bodies.

269

* *!

vity) adted at a fig. 3. and at the new poles a , a, See. as
they become fuch by a fucceffive change caufed by fuch
continued adtion of the force f urging the fphere at

i i if //

every inftant to revolve about the diameter dey or dei

i a

Sec. of the contemporary mid-circle, the new pole ( a ,
See.) would not inftantly be at a finite diftance from the
primitive pole a, but fome finite time would be requifite,
that by fuch fucceffive change, the pole might be varied
to. a finite diftance from a: and the force F continuing
invariable, the velocity ( v ) wherewith the pole changed

its place would be exprefled by y, t being the time elap-

fed whilft the pole is varying from a to a, and z the
length of the arc a a. Therefore the velocity wherewith
the pole will change its place during fuch adtion of the
force f will be exprefled in the fame manner as the ve-
locity (v) of a body moving uniformly from a to a in
the time t may be exprefled ; that is, in both cafes v will

be = - . But there is a material. difference, between the

i

motion of a body fo moving from a to a and the change

/ //

of place of the pole a, a, &e. the former. is permanent,
and will continue to carry the body forward without the
adtion of any force whatever ; whereas the latter will
inftantly ceafe, and the axis will keep its pofition, if the

force

tjx} Mr. landen’s new Theory of

force f ceafes to act thereon ; like as the varying direc-
tion of a projectile near the earth’s furface would imme-
diately ceafe to change, if the force of gravity ceafed to
;aCt.

It is obfervable, that whilft the force f aCts, and the
revolving fphere, in confequence of fuch aCtion, every
moment takes a new axis, the angular motion about the
axis will continue invariable; the aCtion of fuch force
-only altering the axis without altering the angular velo-
city of the fphere about it: like as the direction of a
moving body is altered, without altering the velocity
thereof, by an attractive force continually aCting on it in
a direction at right angles to that in which the body is
moving. And if ever the force f lliall ceafe to aCt, the
fphere will inftantly revolve with its primitive velocity
if) about the axis it then may have been brought to take
by the preaCtion of that force.

The new axis, about which the fphere has fuch ten-
dency to revolve at any inftant during the a Chon of the
force f, I lliall call the momentary axis', and the poles
thereof the momentary poles.

3. From the equation ~~Ws//’r~x (art. 1.) we have
~ — i-. Now if a continued attractive force (f) aCt

* s/ r% — xz

during the time t as above-mentioned, inftead of the
4 inftan-

the Rotatory Motion of Bodies, 271

inftantaneous percuflive force at a, we, according to the
doCtrine of fluxions, muft, inftead of w, take wt or its

equal F i, and x inftead of x, in the expreffion ™ ; there-
fore, in this cafe, we have --4 =-• — — : » .Whence, put-

* * v/ r1 — v! ’ r

/ //

ting z for the arc (a a, or a«, &c.) whole fine is v, and
writing z for its equal —4*-—- , we get r-~ — c> or z — — .
Hence v. denoting the velocity wherewith the mo-

t u

mentary pole (<?, <2, See.) changes its place during the

aCtion of the accelerative force f, we have 2 — vt ■=— > ~

1 c

and confequently v. = —•

4. The value of may alfo be. determined in the fol-
lowing manner (fig. 4.). Conceive a very thin firing
(without weight) to have one of its ends faftened to a
fixed point / and the other to a heavy particle of matter
m\ alfo conceive fuch particle fo to revolve with the ve-
locity e, about the line /», that a certain accelerative
force F (like that of gravity referred to a certain direc-
tion) continually acting on the faid particle m, in a di-
rection at right angles both to the fixing Jm and. to the
tangent to the curve in which m is moving, the firing
fliall deferibe a conical furface. Then Itn being denoted

by

37.2 Mr. landenV new Theory of

e*

by r, .and mo, perpendicular to In, by q; - , the centri-
fugal force urging tn in the direction om, will be to f as

r to V ' r'—q- - lo. Therefore f muft be = - — . Now

if, whilft rn is fo revolving, the force f ceafes adting, the
laid particle ( m ) will, it is obvious, immediately proceed
to defcribe a great circle of the fphere whole radius is r
and center /, of which great circle one of the poles will
be lituated in alefler circle parallel to, and 9o° .diftant
from, that defcribed by m during fuch action of the faid
force; which pole, during fuch adtion, will change its
place in the faid leffer circle in which it will at any time
be found with a velocity (v) which will be to e as (s) the
radius of the laft mentioned circle to q. But s will be

Vr2-y2; therefore we have v : e :: Vr2-y2 : q, and — -

-= — . Confequently f = tyfl — L will be = - x — =— , and

rq

V-

r F

Let now «bea point on the furface of a fphere whofe
center is /, and radius Im - r; and let the fphere revolve
. about an axis lo that m lhall defcribe a great circle with
.the velocity e. If then fuch a motive force begins to adt
on the fphere, that, continuing its adtion, the point m
lhall always be urged by the invariable accelerative force
vF to move in a diredtion atright angles to the ray Im and

the Rotatory Motion of Bodies. 2 73

to the tangent to the curve which m will defcribe ; that
point it is obvious will, in confequence of the adtion of
that force, defcribe a leffer circle of the fame radius (y)
as that defcribed by the particle ni when faftened to a
firing and acted on by the force F as above-mentioned;
and the center of the fphere being always confidered as
at reft, one of the momentary poles of the fphere will

defcribe a circle whofe radius will be — V r* - qz parallel
to, and 90° diftant from, that defcribed by the point ?«,
For if the faid force were to ceafe adting, that point of
the iphere would defcribe a great circle, as would the
particle m at the firing in the like cafe ; and therefore
both the faid particle and the point m of the fphere at
every inftant having the fame tendency, and being adted
on by -equal accelerative forces, the effedt will be the fame
with refpedt to the motion of each. Gonfequently, v being
put to denote the velocity wherewith the momentary
pole changes its place in the circle which it will defcribe
whilft the motive force producing the accelerative force

F adts on m as juft now mentioned, v will be = — , the

fame as in the preceding article, e here denoting that
velocity which we there denoted by c.

5. Referring the point of adtion of the perturbating
force to the mid-circle we have not hitherto confidered

Vol. LXVII.

that

N n

5»74 Mr. landen’s new. 'Theory of

that point as varied with a greater or lefs velocity than,
(e) that of the point m ; that is, with reference to fuch
circle we have always confidered the point m as the point
of action. But it is obvious, that, cateris paribus y the
point of adtion with refpedt to the mid-circle (which
point we will now denote by q) may be varied with a
velocity greater or lefs than e\ and that, cater is paribus,
the velocity ( v ) of the momentary pole will be the fame
with what velocity foever (y) the point of adtion of the
force F be varied; the diredtion in which that force adts
being always at right angles to the ray (/y) from the
center of the fphere, and to the tangent to the curve de-
fcribed by (y) fuch point of adtion.

Yet, although v continues the fame whether, cateris
paribus , (u) the velocity of the point y be greater, equal
to, or lefs than e , the immoveable circle in which the
momentary pole will be found will not continue the
fame ; that circle being greater, equal to, or lefs than the
circle whofe radius is vV-y2 according as u is lefs, equal
to, or greater than e% as will be made more evident by
what follows.

/ * '

6. Fig. 5. Let p (in the great circle R p Q.y t) be one

of the poles of the axis about which the fphere rstv,

whofe radius is r, is revolving (according to the order of

the letters v y s) with the angular velocity e% meafured at

the Rotatory Motion of Bodies. zj $

the diftance r from the axis; and whilft it is fo revolving
let the faid pole be urged to turn about a diameter of the
/ /

mid-circle vqs towards q, by an accelerative force f, and
let fuch force continue to a<ft on th&fucceffive new poles

tt at

p, pf Sec. as they become fuch, always urging the fphere
to turn about a diameter of the contemporary mid-circle,
whilft the direction in which fuch perturbating force
acts is regulated in the following manner.

Conceive the faid revolving fphere to be furrounded
by an immoveable concave fphere of the fame ra-

t // at

dius r. Then the momentary pole (/>,/>, />> 'Sec.)" will

/ it i.i>

always be found in fome curve pp? Sec. in the faid

i it Hi

concave fphere, and in fome curve ppp Sec. on the
revolving fphere; which laft mentioned curve will conti-

/ a tit

nually touch and roll along the bther curve p pp Sec. on
the immoveable fphere, the force f and the direction in
which it a6ts varying in any manner whatever. Let f
be invariable; then, it is obvious, the two curves fo
touching each other will be circles ; and if great circles

t / an tit nt

p y, p y, p y, Sec. be deferibed on the furface of the im-
moveable fphere whofe planes fliall be at right angles to

,/ // /// . ✓ // ttf >

the plane of the circle ppp Sec. the points q, q, q, Sec.

N n 2 therein,

<276- Mr. landen’s new 'Theory of

/ U Hi

therein, each 90° diftant from p, p, p, Sec. refpe£tively„

/ it Hi

will be in a circle {qqq See.) parallel to the faid circle

i - ;/ m .

ppp &c, Now as a regulation to the direfiion in
which the force f lhall urge the momentary pole, let
that direction be always a tangent to the great circle fo
palling through that pole and the correfpondent point

/ it

Hi

J ii / W

q, q, or q, 8cc. whilft the arcs qq, qq, 8cc. are to the arcs,

/ it i Hi

p p, p p, 8ce. refpedlively in the conftant ratio of u to v.
The direction in which the force f adls being fo regu-

✓ // Hi

lated, it is obvious that the radius of the circle p p p

/ a at

See. being denoted by b, the radius of the circle qqq

See. will be— Vr1—^2, the diftance of thefe parallel cir-
cles being 9 a0. Therefore their peripheries being as the
velocities (<y and u) with which they are deferibed, their
radii (b and 's/r^—b1) will be in the ratio of the faid velo-

V- - ■ /rz b*

rT-h~ \ whence, - being =

* a ih

b, the radius oi the circle ppp See. is found =

b

rv

V

y/ u%+ v1,

. i a at

and the radius of the circle qqq.

I + -T~i
r F

&c. -

r u

s/uL-\-vL rz F‘

¥ F

==, v being = — , the velocity where-

with

the Rotatory Motion of Bodies. . 277.

// ///

with the momentary pole p, />, 8cc. changes its place.

/

Confequently, if pr be an arc in the faid immoveable

concave fphere whofe line is

rv

y/ul + vz f

, the great*

I+rz f1

/ i a it Hi v//

circles q p, q p, q p, Sec., will interfedt each other at the
point r.

7. Moreover, the force f being invariable and adting
as exprefled in the preceding article; the primitive pole

/ Ht

p and the momentary poles p, py. Sec. will all be founds

t nit*

in a circle ppp 8cc. defcribed upon the furface of the
revolving fphere, as obferved in that article; which,
circle, during the adtion of the force of f, will (as is alfo
obferved in the faid article) always touch and roll, along

/ 1/ Hi

the immoveable circle (p p p &c.) whofe radius we

have juft now found —

rv

, the point of:

\/ uz + vz y1 e 2 u
1 +“

contadt being always the momentary pole. .

t. !<

Let the line of the arc PQ_of the great circle RpQji t
in the revolving fphere be equal to h, the radius of the

i a ni

faid circle ppp 8cc. then will the point Q_and its oppo-
fite point’ (o) in the furface of the faid fphere, during
the adtion of the force F, deferibe circles in the fur-
3, rounding

278 Mr. landen’s new 'theory of

f d /h

rounding immoveable concave fphere parallel to (p p p

— // Ht

&c.) the circle defcribed by the momentary pole p, p,
See. in the fame concave fphere. And fuch point eg and
its oppofite point (o) being continually urged by the
force f in directions at right angles to the tangents to
the arcs they deferibe, their velocity will continue the
fame as before the action of the faid force commenced ;

4 n m

which velocity, and the radius of the faid circle ppp
&c. will be determined by the following computation.

ek

That radius being denoted by h, we have r : k :: e : — »
the velocity of the point egbefore the aft ion of the force

F commenced; and b : v :: k :-j , the velocity of the

fame point (eg) during the action of that force, k being
put for the fine of the arc <gR ; therefore the velocity of
eg continuing the fame during the aftion of f as before,

6 k K.ZJ

we have — — -y . But k is the fine of the fum of the arcs

rp, peg, whofe fines are h and k refpeftively ; therefore
b y/r —k + be = k ; and by fubftitution we get

ek v\/.rx — kz kv<Vrz — bl v\/rz — kx ku */r2 — hz , . «

-= = — + 7’ V- being = -

r

by the preceding article. Hence we find k =

rv

the Rotatory Motion of Bodies.

rv

; and it follows, that

ev

*79

, , , , , , ( = — ) will be

equal to the velocity of the point q_, and likewife of its
oppolite point (o^ in the furface of the fphere. It alfo
follows, that k, the radius of each of the circles defcribed
by thofe points, during the action of the force f will be

, rev

equal to -7== — ..

V uz-{-vx xv e — + vz

By what is done it appears, that during the aflion of
the force F, the motion of the revolving fphere will be

/ it ni

regulated by the circle ppp Sec. thereon (whofe radius is
^3=== = ■■ = — continually touching and rol-

* 2 S

r f

i n nt

ling along the immoveable circle ppp 8ec. (whofe ra-

dius is

— - = ~r r ? fo that the velocity of the
y/u1 + Vi +*!£/

point of contrail be = v = — . Conlidering the point Q_as

t it m

always urged from the points p, p, p, 8ec. and confe-
quently its oppolite point (o) towards thofe points, it is
neceflary to obferve, that according as u is lefs or greater

than e, the arc pq^ (whofe fine is — wilt be lets

or greater than 90° ; and the point (o) oppolite to q_
on the furface of the fphere will accordingly be at a,

i

greater or lefs diftance than 90° from p.

If

will

-280 Mr, landen’s new theory of

If u be negative the arc pr whofe fine is ^===e

be greater than 90°.

8. The motion of the fphere according to the regula-
tion in the preceding article is one motion compounded
of the primitive motion of the fphere and the motion
generated by the action of the force f. But conceiving

the velocity of the point Q_to arife from an

impulfe given to it whilfl: the fphere revolved about an
axis of which Qjwas an immoveable pole before fuch im-
pulfe, and about which the mid-circle correfponding to
that primitive axis revolved with the angular velocity

-e.ecn u (a)

and confidering that the force f, continually

aching at right angles to the momentary direction of the
point Q_and to the plane of the faid mid-circle, only ferves
to alter the pofition of the faid primitive axis ; we may,
by the help of what is done above, explain the motion
which the fphere will have, during the adlion of the
force F, fo as to retain in our ideas the two primitive mo-
tions (one about the axis qo, and the other about a dia-
meter at right angles to that axis) as remaining diftindt
and unaltered.

(a) Denoting this by c and the velocity of Qpy d, y/ d + d1 is e, agree-
.able to art. j ,

Fig-

the Rotatory Motion of Bodies. 281

Fig. 6. Let ed be a great circle on the revolving
fphere, of which Q_is a pole, and let a fmaller circle dl
parallel to (mqJ that which we have found will be de«
fcribed by the point q^, be drawn on the immoveable
concave fphere fa as to touch that great circle in the point

(d) where the great circle qjpr cuts it; the radius of

rv c/3 ru.e — u

which 1 effer circle will be ( - yV1 — k 2 = > . ,

;vV + v* x 7,1 ‘ + v‘

Then the revolving fphere, during the adtion of the
force f, will fo move, that the firft mentioned great circle
(ed) lhall continually touch and roll along the faid leffer
circle dl, the velocity of the point of contact (along that

circle) being =

v c/o u.e — u

(b)

, and the fphere at the fame

%/ e—it " + v*

time turning about the axis of which Q_is a pole with the
primitive angular velocity

e — zJ -\-vz

Thus the primitive motion about the axis of which
qJs a pole is preferved diftindt, whilft that pole proceeds

defcribing a circle, whofe radius is

■with the velocity
it.

rev

ev

e — -f'y2

%/ uz -±vzx\/ “ -f vz

which we fuppofed given to

(h) This is to the velocity of the point c^as y/r*— k2, to k; that is, as the
radii of the arcs defcribed,

Vo LXVIL Oo It

2.82 Mr. landen’s new 'theory of

It is obfervable, that the laft mentioned velocity will,
according to this regulation of the motion, be to the
primitive angular velocity about the axis of which ojs a
pole, as v to e—u, or as v to u-e, according as u is lefs or

J

greater than e\ that is, according as the arc pQ_is lefs or
greater than 90°.

9. From what has been faid it follows, that denoting

the two primitive angular velocities

e.ers: u

e — d + vz

and

ev

—»l +v

(fpecified in the preceding article) by c and d

refpe&ively, the radius (fig, 5.) of the circle ppp See.

dr

(or fine of the arc pq=pq_, Sec.) will be = — ; the radius

4 it iii * Ji

of the circle ppp 8ec. (or fine of the arc pr=pr, Sec.) =

— t a great circle oaffing through the,

primitive poles o and eg, on the revolving fphere, will
turn from the pofition oRCgwith the velocity^ meafured;

at the mid-circle,, or with the velocity — ■

meafured at the fixed point r ; whilft thofe poles deferibe,

i // W

with the velocity d, circles parallel to ppp See. the
radius (k) of each of the circles (fig. 6.) fo deferibed
2 being

the Rotatory Motion of Bodies.

83

being = — . : the radius (Vr*-k*) of tne

♦/ d e'"zsp2.cdr¥ r F ' ’

s/d

circle dl will be =

GO

rXcd -}- r F

s/dx ex^2edr? r2F

L=— ; and the velocity

. ^7. ' J

( aiong the faid circle dl = c % rf: the

\V e—u\ +i/V d

up

per or lower of the double figns taking place according
as u (= e q= ~j) is lefs or greater than e; that is, according

i rfr\

as the arc PQ.(whofe line is = —) is lefs or greater than

90°.

10. As an inftance of the ufe of the preceding con-
clufions, I will now apply them in the folution of a very
interefting problem, which I have not before feen folved.

Suppofe a given fpheroid , wbilft revolving uniformly
about its proper axis , with a given angular velocity , to be
fuddenly urged by fome percujfve force to turn , with fome
given angular velocity , about a diameter of its equator ; it
is propofed to explain the rotatory motion of the fpheroid
confequent to the impulfe fo received.

Fig. 7, 8. Let DOEQ_be the fpheroid, whofe femi-axis
co = cc^is = b, and equatorial radius cd = ce = r; and
fuppoling it before the impulfe to revolve about its pro-
per axis QQjwith the angular velocity c, meafured at the
diftance r from the axis, let the poles (o and qJ be fud-
denly urged by fome percuffive force to turn about a

O o % diameter

Mr. landen’s new Theory of
diameter of the equator of the fpheroid, with the angu-
lar velocity dy likewife meafnred at the distance r from,
that diameter. Upon receiving fuch impulfe,the fpheroid
will take a new axis of motion, which will be a momen-
tary one; fuppofe fuch new axis to be p c.7ta;. Then the
particles of the fpheroid being urged (or having a ten-
dency) to turn about that axis with the angular velocity

\Jc2+dzy (which we will denote by e) their joint centri-
fugal force will fo urge the fpheroid to turn about that
diameter of the equator which fhall be at right angles to
the momentary axis p err, that the accelerative force of
the point d of the equator to turn it about the faid dia-
meter according to the order of the letters d q_e will (as
appears by what is proved in art. i . and in the Appendix

annexed hereto) be = y x prpj. or ^ x ^ ^ according as

b is lefs or greater than r: and it follows from hence and
what is proved in art. 3. and 4, that v, the angular velo-
city (at the diftance r from c) with which the momen-
tary pole p will change its place, will accordingly be =

cd r*—bz cd r-—r

* Kr* + b* °r t V + ***

(c) To find the pofition of this axis fee art. 1, by which the fine of the angle

dr

oc p (to the radius r) is.found = — .

More-

the Rotatory Motion of Bodies . 285

Moreover, referring to our obfervation in art. 8. let

u-e be to — x p pr (the value of v) as c tod, u being

1 i . cd bz — r 2 , ,

greater than e ; or let e—u be to — x pr—jy as ctoa^u being
lefs than e: whence, in both cafes-, we fhall have the

(f r ^ If- \

yx— ) for the value of u-e; and:

f }f

eonfequently u, in both cafes, will be = e + — x prpry •

Conceive now a fpherical furface without matter,
having the fame center and radius as the equator de, to
be carried about with the revolving fpheroid; and fup~
pofe a fphere, whofe radius is r, to revolve about an
axis pen with the angular velocity er and, whilft it is
lb revolving, let an accelerative force (f) equal to

T*?TP or r xv+T25 according as a is lels or greater

than r, urge the pole />, and the fucceffive momentary
poles as they become fuch, to turn about a diameter of
the contemporary mid-circle in the manner exprelfed in.

, , . f1 r2-bz cd rz — bz

art. o. u being to v as e + to — x y-yy or as e +

-x -r-^p to — x prp-p. , according as a. is lefs, or greater

than r. Then will the motion of the furface of this
fphere be exactly the fame as the motion of the faid
fpherical furface carried about with the revolving

fpheroid

8 6 Mr. lan den’s new 'Theory of

-fpheroid after receiving the impulfe of the percuffive
force. Therefore, having reference to onr conclufions in
the preceding articles, we, by fubftitution, readily obtain
folution to our problem.

By fubfhtuting properly or — x —~p. ror F ,we

find,

d2r

dr

— — X

r’ + i’

l/SS^zcdrF+r' ‘ +

&

r xca + r f

2r

y/d%? ^%cdrF + rzF2 ^

d 2

, in rF 2 r c

andc + 7 = pq^i*

Which equations, refpedt being had to the conclufions in
art. 8. and 9. indicate that, whether b be lefs or greater
than r, if an immoveable circle dl, whofe radius is =

.. — ~t , be conceived to be defcribed in a plane

v4,A+7qrT><-

inclined to the plane of the equator of the fpheroid (be-
fore the impulfe) in an angle whofe fine (to the radius r)

dr

IS = ~ x

v;

r^ + b2

, fo that the faid circle touch

4r++7+7yx —

the faid equator in the point d in the fedtion o/dqje;
the fpheroid after the impulfe will fo revolve, that its

equator

the Rotatory Motion of Bodies . 2.87

equator will always touch and roll along the faid im-
moveable circle (dl), the velocity of the point of con-

2 c

tact (along that circle) being = pr— 7, whilft the fpheroid

turns about its proper axis (oq.) with the primitive an-
gular velocity c , and the poles o and q_ (by the faid
rolling of the equator) defcribe circles (whofe radii are*

each =

dl, with the angular velocity d (or their proper velocity

--) which we fuppofed given to them by the impulfe^..
Thus the motion of the fpheroid confequent to the im- -
pulfe appears to be remarkably regular.

And in the very fame manner may be explained the
motion of a cylinder, whofe primitive motion about its .
proper axis may be difturbed by fome pereuffive force in
like manner as we fuppofed the fpheroid difturbed ; only
(inftead of the former fubftitution for f) fubftituting for
the accelerative force arifing from the centrifugal force .
of the particles of the revolving cylinder its proper value .

— x (computed in our Appendix) and afterwards :

proceeding as we have done with regard to the fpheroid,

(d) Other ways of folving the problem are alfo fiaggelled by the preceding
articles e

bd

7 x

r*'+b’

V

4 r'+S+W x

i)

parallel to the faid circle

b de- -

288 Mr. lan den’s new theory of

3 denoting half the length of the cylinder, and r the
radius of any fedtion at right angles to its proper axis.

Seeing that ) the expreffion for the faid

accelerative force refpedting the cylinder vanifhes when b

i

is = it is manifeft that the cylinder in that cafe will

(with refpedt to its own particles) undifturbedly revolve
about any axis whatever paffing through its center of
gravity, as will a fphere. Which remarkable property of
that particular cylinder I believe has not before been
taken notice of.

There are, I am aware, bodies of other forms having
-the like property.

The preceding articles lead us to confider the motion
of the earth’s axis in a light, I prefume,, more clear and
fatisfadtory than any in which it has before been confi-
.dered ; hut I muft, for want of leifure, defer making the
application till fome future opportunity ; only obferving
here, that by what is done above it appears, that from
the adtion of the Sun and Moon on the earth its axis has
a diurnal motion, which I have no where feen explained.
Which motion is not much unlike that of the axis of
the revolving fpheroid juft now confidered, when (2 b)
this laft mentioned axis is many times longer than (af)
a the

Wf

-f

M

X

the Rotatory Motion of Bodies. 289

* - V ’

the equatorial diameter of the faid fpheroid, and - very

C

fmall.

APPENDIX.

Shewing how the joint centrifugal force of the particles of
a fpheroid or cylinder , having a rotatory motion about
any momentary axis , is computed.

1 . FIG. 9. Let p be a particle of matter firmly connected
'di the plane doefqg, in which the line qcqJs fituated ;
and pq being a perpendicular from p to the faid plane,
let the diftance pq be denoted by u; alfo, the line ql
being at right angles to o/cq_, let the diftance pi be de-
noted by h. Then, the faid plane with the particle p
being made to revolve about o/cQ^as an axis, with the
angular velocity e meafured at the diftance a from the

faid axis, the velocity of p will be = y , and its centri-
fugal force from / will (by a well-known theorem) be =

he7" he7"

to make it or the expreflion being ~ x p. Whence,

by refolving that force into two others, one in the
direction qp , and the other in a direction parallel to
lq, it appears that the force urging p from the plane

ue7"

doefqg will be= — x />, let the diftance lq be what it will.
Vol. LX VII. P p 2. The

ago Mr. lan den’s new Theory of

2. The particle p being connedted with the plane
doefqg as mentioned in the preceding article, and the
diftance c/ being denoted by v; if p be urged diredtly
from the faid plane by a force/# x />, the efficacy -of that
force to turn the faid plane about the line hci, therein ;
drawn at right angles to ocq_, will (by th'e property of the

lever) be equivalent to the force adting on the

faid line occyat right angles to tire faid' plane at the dif-
tance g from the point c.

Moreover it is obvious, that, cceteris paribus , the effi-
cacy will be. the fame let the diftance of q from / be what
it will.

Fig. 10. Let q coincide with /; and let be a line
in the plane c/p continued (which plane will be at right
angles to the plane doefqg) ; alio, pk being at right an-
gles to c ky let thofe lines p k and c k be denoted by w and
x reflectively. Then the fine and cofine of the angle
kco to the radius i, being refpedtively denoted by m and

the forced — will be = — x«kx^2-x‘ ^wk—T^wx.

Confequently, if each particle of any folid body, through
which a line hci and a plain doeifqgh may be conceived
to pafs, be urged from that plane by a force expreffed by
fuxp as above; the force which, adting on the line
oco_at the diftance g from c, would be equivalent to the

efficacy

the Rotatory Motion of Bodies. 291

efficacy of all the forces acting on the feveral particles of
that body to turn the fame about the line hci will
be obtained by computing the fum of all the forces

adbing on the faid body.

The computation of fuch equivalent force will in moft

cafes be abridged by obferving that, if pk be continued to
// //

p fo that kp be = kp, the efficacy of the force on the par-
//

ticlep, to turn the body about the line hci in oppofition
to the force on the particle />, will be reprefented by

It

v/ A " ' * ■■ — -

the equivalent force -- x mn x xz-'vf+ml~nz x wx a&ing

on the line oco_at the diftance g from c ; and that there-

//

fore the efficacy of the two forces on p and p, to turn the
body about hci, will be reprefented by the equivalent

force Xmnx.w2—xz adting on the line ocq_, at right
angles to the plane doeifqgh, at the dillance g from c.
3. Pig. j 1, i t,. If the body be a cylinder, afpheroid,

or the like, and its proper axis be lituated in the line c k,

//

the ordinates correfponding the ab/ciffic kp.-, kp, in the
circular fedlion hi whofe center is k, will each be paral-
lel to that diameter paffing through c, about which the
body will be urged to turn ; and each of thofe ordinates

will be = \ly%—wz, y being the radius of fuch fedtion.

P p a Therefore,

29a Mr. landen’s new Theory of

Therefore, writing 2 ^]yL-wL inftead of p, it follows that

*mnxx — -x2y\ the whole fluent of K

£ 4 s

/ • “

mnxxw2-x2xw, generated w ( = k p — kp) from o becomes

equal to the radius y (both x and y being confidered as

invariable) will exprefs the value of the force which,

acting on the line oco_at the diftance g from c, would be

equivalent to the force of all the particles in the faid fec-

tion, whofe thicknefs is denoted by the indefinitely fmall
/

quantity x ; the diftance c k being denoted by x, and a
being put for (.78539.) the area of a quadrant of a circle
whofe radius is 1.

4. Fig. 1 1 . In the cylinder whofe length is 2 b and dia-

4. yZ

meter 2 r ; y being -r->g_ - x'y1 will be = r x — —x2 : con-

r i

fequently, the fluent of —~x2xx, generated whilft x
from o becomes = b, being ~ , we have —p— xmnx

~ - b— - x 3r~ — 4 b2 x M for the force which, acting

as above at the diftance g from (c) the center of gravity
of the cylinder, would be equivalent to the efficacy of the
forces ailing as above on all the particles of the cylinder
to turn it about a diameter paffing through c, M being
the mafs or content of the cylinder.

7

5- Fig-

tbe Rotatory Motion of Bodies. 293

5. Fig. 12. In the fpheroid whofe proper axis is 2 b

and equatorial diameter 2 r, y1 being — jly.bz—xzf- — xzyz

confequently, the

... . , r r x r x

will be = r x — - -yjr + —b

fluent of

+ -AT +
x*x

X T

72 :

jjy - -x*x+y , generated whilft a from

, , , . Pb Pb Pb b 3 P 2 — —

o becomes = b , being — — g- + — — -+-•=— x r b-b 3, we

have

16 a/j

y.mny.rzb—bi—- — s for the force

which, a6ting at the diftance g from c the center of the
fpheroid,. would be equivalent to the efficacy of the
forces adting as above on all. the particles of the fpheroid.
to turn it about a diameter of its equator,, s being the mafs
or content of the fpheroid.

Thefe equivalent forces are diftinguifhed by the name
of motive forces; the correfpondent accelerative forces
are computed in the following articles.

6. Fig. 13. The body being a fpheroid whole center
is c, and whofe proper axis pn is = 2 b and equatorial dia-
meter ab — ir\ let f be the accelerative force of a par-
ticle at the diftance^- from the. axis about which the body
is urged to turn, which axis is fuppofed to be a diameter
of its equator. Denote by ki by y; and let the
abfciffa ko and its correfpondent ordinate (parallel to the
laft mentioned axis) in the circle whofe radius is ki be

denoted

ag4 Mr. laxdek’s new ’Theory of

denoted by s and t reflectively. Then, confidering the
' body as urged to turn about that diameter of its equator
which is at right angles to ab, the accelerative force of

s every particle in the laid ordinate will be = + * x f,

, and the motive force of all the particles in the fame ordinate

will be

v/ s + ** . x1 + .

xf is=

s' g

f s Vyw1', to which (by

i ** 9 I

the property of the lever) a motive force =— — x f j vy2-sl

acting at the diftance g from the center at right angles to

a ray therefrom would be equivalent. Therefore, confi-

dering x and y as invariable, and s only as variable,

/

x the whole fluent of x sz+xz will denote a

g y

force which, acting at the diftance g from c, would be
equivalent to; the motive force of all the particles in the

fedtion hi whofe radius is hi and thicknefs x. Which

fluentis xhz-xzxxz+ ~xhz-x\ Con-

8 A rzF

fequently ~gj~ x the whole fluent of x x bz — xl x

x l + Tbl * bz-xz will denote a, motive force which, adting

at the diftance g from c at right angles to a ray therefrom,
<would be equivalent to the whole motive force urging
-the fpheroid to turn as above mentioned. Such equivalent

force

the Rotatory Motion of Bodies.

293

1 6 A F — * * p •— — .

force will therefore be = z x r^b+rb^-.—x r'+^xs:

Ss 5

*5£

ftnn

and this being put -J~— xrz-h'~ x s (the value of the

vo

r2— £2
rz + y ’

fame force found- in art.. 5.) we find f =fgmn x
which will bfe - x if / be = ^, its value

computed in art. 1*.

C £ y1 If-

Or f will be denoted by — x -t-j-j-; if t be to e as m 1

to d, and as « to c; and a and g be each — r.

7 . Fig. 14. The body being a cylinder whcrfe center
of gravity is in c, and. whole proper axis pn is 2 b and
diameter 2 r ; .the accelerative force . (f) at the diftance

p' from c; will in like manner be found — MjygL x ?r ~4'i „

0 7 a $r -f 4 b V

the cylinder being confidered as urged to turn about a
diameter palling through c.

If 1 : e :: m : di: n : c, and a and g be each = r, f will

r * 3^ + 4^

C *96 3

XVI. Directions for making the bejl Compojition for the
Metals of reflecting Telef copes ; together with a Befcrip-
tion of the Proce/s for grinding , polijhing , and giving
the great Speculum the true parabolic Curve. By Mr.
John Mudge; communicated by Alexander Aubert,
Efq. F. R. S. •

Read Feb. 27.^ March 6, and 13. Jk g the method of calling,

■** grinding, and polifhing the
fpecula of reflecting telefcopea, by MelT. molyneux and
■Hadley, which is publdfhed in Dr. smith’s Optics, is
what the workmen have generally followed, and is
confequently well known to them ; I fhall in the follow-
ing account avoid a repetition of the general directions
there given,, and only remark upon fuch parts of that
procefs which I think are efientially defective, and fup-
ply them by a method of my own, which, from long
and repeated trials, I have found completely to anfwer
vthe purpofe. After, therefore, referring to the above
account for the manner of making the gages, patterns,
the method of calling, as well as a great many other par-
ticulars, I will begin with

Phe

Mr. mudge on the ConftruCtion, See.

297

The befl compofition for the fpecula of reflecting telefcopes.

The perfection of the metal of which the fpeculum
fhould be made confifts in its hardnefs, whitenefs, and
compaCtnefs; for upon thefe properties the reflective
powers and durability of the fpeculum depend. And
firft of the hardnefs and whitenefs of the metal. There
are various compolitions recommended in smith’s Optics,
all which have however their feveral defects. Three
parts copper and one part and one-fourth of tin will
make, he fays, a very hard white metal ; but it is liable
to be porous. This, however, is an imperfection which
I fhall prefently fhew the method of preventing ; but the
permanent fault of it, and which I have myfelf expe-
rienced, is, that it is not hard enough. The fpeculum of
a reflecting telefcope ought to have the utmoft poflible
hardnefs, compatible with its being operated upon by the
tool.

It is to be obferved, that ever fo fmall a quantity of
tin added to melted copper deftroys its perfeCt malleabi-
lity, and at the fame time produces a metal whiter and
harder than copper. As the quantity of tin is increafed,
fuppofe to a fifth or fourth part, the metal becomes
whiter, ftill harder, and confequently more friable. If
the quantity of tin be further increafed to a third of the

Vol. LXVII. Q q whofe

298 Mr. mudge on the ConJlruBion

whole compofition, it will then have its utmoftwhitenefs;
but will he rendered at the fame time fo exceedingly
hard and brittle, that the fineft wafhed emery upon lead
or brafs wfill not cut it without breaking up its furface ;
and the common blue ftones ufed in grinding the fpe-
culum, w ill not touch it. Mr. jackson (fome time fince
dead) a mathematical-inftrument-maker, and a moft ex-
cellent workman, told me, that the tin was increafed to
the above proportion in his metals; but that they were
fo exceedingly hard, that it coll him an infinite deal of
pains, and a journey of two hundred miles, to find out a
ftone of fufllcient hardnefs to cut it, and whofe texture
at the fame time was fine enough not to injure its furface.
I have feen feveral of his finifhed metals ; they were in-
deed perfectly hard andw’hite; but the kind of ftone with
which he ground them he kept a fecret.

After many experiments with various proportions of
tin and copper, by gradually increafing the former, I at
laft found that fourteen ounces and an half of grain-tin
to two pounds of good Swedifh copper, made a beautiful
white and very hard metal; fo hard indeed, that the
ftones would but barely cut it, and wafhed emery on
"brafs or tin but juft grind the furface without breaking
it up ; whereas the proportion of tin being increafed by the
addition of only another half ounce, the former incon-
venience

of Metals for reflecting flelef copes. zgg

venience immediately took place. This therefore is the
maximum in point of hardnefs.

Thus much of the two firft confiderations, the hard-
nefs and whitenefs of the metal; the next, and indeed
the raoft effential, property is its compadlnefs, or its
being without pores.

This compofition (though complete in the former
refpedls) was, as well as Dr. smith’s, fubjedt every now
and then to be porous ; fometimes, indeed, I fticceeded in
calling a lingle metal, or perhaps two or three, without
this imperfedlion ; at other times, and moft frequently
indeed, they were attended with this defedl, without my
being at all able to form a probable conjedlure at the
caufe of my fuccefs or difappointment. The pores were fo
very fmall that they were not difcoverable when the metal
had received a good face and figure upon the hones, nor
till the laft and higheft polifh had been given ; and then
it frequently appeared as if dulled over with millions of
microfcopic pores, which were exceedingly prejudicial
in two refpedls ; for firfc, they became in time a lodg-
ment for a moillure which tarnilhed the furface; and
fecondly, on polifhing the fpeculum, the putty necefia-
rily rounded off the edges of the pores, fo as to fpoil a
great part of the metal, by the lofs of as much light and

Q q 2 fharpnefs

300 Mr. mudge on the ConJlruSUon

tharpnefs in the image as there were defective points of.
reflection in the metal.

Betides the trouble of a great number of experiments,
in order to get rid of this mifchief, and to afcertain the
eaufe to which it was owing, there was this additional
inconvenience attending it, viz . that the fault was not
difcovered, as was obferved before, till a great deal of
trouble had been taken in grinding and even polifhing
the metal, the whole of which was rendered ufelefs by
the mortifying difcovery of this defeat.

I was extricated at laft from this difficulty, and in fome
meafure by accidept. Having one day made a great num-
ber of experiments, and having melted down all the good
copper I had or could procure ; though puzzled and fa-
tigued, yet not caring to give it up, I recollected that I
had fome metal which was referved out of curiofity,
and was a part of one the bells of St. Andrew’s which
had been re-caft. Expecting, however, very little from
this grots and uncertain compolition, I was neverthelefs
determined to fee what could be made of it by enriching
the compolition with a little freffi tin. Accordingly
catting a metal with it, it turned out perfectly free from
pores, and in every refpeCt as fine a metal as ever I taw.

I could not at fir ft conceive to what this fuccefs was
owing ; but at laft I hit upon the real eaufe of that defeCt,
c which

of Metals for reflecting ctielefcopes. 301

which had given me fo much embarraffment and trou-
ble during a courfe of near a hundred experiments, and
in confequence thereof fell upon a method which ever
after prevented it.

I had hitherto always melted the copper firft, and
when it was fufficiently fufed, I ufed to add the propor-
tional quantity of tin ; and as foon as the two were mixed,
and the fcoria taken off, the metal was poured into the
moulds. I began to confider that putty was calcined tin,
and ftrongly fufpedted, that the exceffive heat which the
copper neceffarily undergoes before fuilon, was fufficient
to reduce part of the tin to this ftate of calcination, which
therefore might fly off from the compofition in th e form
of putty, at the time the metal was poured into the flafks.

Upon this idea, after I had furnifhed myfeif with
fome more Swediih copper and grain-tin (both which I
had always before ufed) I melted the copper, and having
added the tin as ufual to it, caffc the whole into an in-
got: this was, as I expedted, porous. I then melted it
again, and as in this mixed ftate it did not acquire half
the heat which was before neceffary to melt the copper
alone, fo it was not fufficient to calcine the tin ; the fpe-
culum was then perfectly clofe, and free from this fault ;
nor did I ever after, in a fingle inftance, meet with the
above mentioned imperfection.

All

2,0 2 Mr. mudge on the ConfiruBion

All that is ncceiTary, therefore, to be done to procure
a metal which fhall be white, as hard as it can be
wrought, and perfectly compact, is to melt two pounds
of Swedifh copper, and when fo melted, to add fourteen
ounces and a half of grain-tin to it; then, having taken
off the fcoria, to caft it into an ingot. This metal muft be
a fecond time melted to caft the fpeculum ; but as it will
fufe in this compound ftate with a fmall heat, and there-
fore will not calcine the tin into putty, it flioukl be poured
off asfoonas it is melted, giving it no more heat than isab-
folutcly neceffary. It is to be obferved, however, that the
fame metal, by frequent melting, lofes fomething of its
hardnefs and whitenefs : when this is the cafe, it becomes
neceffary to enrich the metal by the addition of a little
tin, perhaps in the proportion of half an ounce to a
pound. And indeed when the metal is firft made, if in-
ftead of adding the fourteen ounces and a half of tin to
the two pounds of melted copper, about one ounce of
the tin were to be referved and added to it in the fucceed-
ing melting, before it is caft off into the moulds, the
compofttion would be the more beautiful, and the grain
of it much finer: this I know by experience to be the
cafe.

The beft method for giving the melted metal a good
furface is this : the moment before it is poured off, throw
into the crucible a fpoonful of charcoal-duft ; imme-
2 diately

of Metals for reflecting TeleJ copes. 303

diately after which the metal muft be ftirred with a
wooden fpatula, and poured into the moulds,

I wiili I may not be confidered as tedious in the above
detail; but as this bulinefs caufed me a great deal of
trouble, I was willing to give fome account of the means
by which I was freed from this difficulty ever after.
Perhaps, indeed, the whole of this procefs may be unne-
ceffary, as many years lince, I communicated this com-
polition, and I believe at the fame time the method of
preventing the pores, to the late Mr. peter collison,,
a member of the Royal Society ; and likewife two or three
years lince, at the defire of my brother, to Mr. michell.
Although it be poffible, therefore, that this method is
generally known, yet, as I have frequently of late feen,
fpecula with this defect, and obferved metals of fome
of Mr. short’s telefcopes which are not quite fo per-
fect as could be wiffied (though they are all exqui-
litely figured) I was willing by this publication wholly
to remove any future embarraffment of this fort, and
to furnilh workmen with an excellent compofition for
their metals. And would the Royal Society be pleafed
to honour the procefs with a place in their records, I
know of no other method fo proper to give this, as well
as the following information, a general notoriety.

The metal being caft, there will be no occafion for
the complicated apparatus directed by Dr. smith, for

grinding

304 Mr. mudge on the ConJlruEUon

grinding and polifhing it. Four tools are all that are
neceffary, viz. the rough grinder to work off the rough
face of the metal ; a brafs convex grinder, on which the
metal is to receive its fpherical figure ; a bed of hones
which is to perfect that figure, and to give the metal a
fine fmooth face; and a concave tool or bruifer, with
which both the brafs grinder, and the hones are to be
formed. A poliiher may be confidered as an addi-
tional tool; but as the brafs grinder is ufed for this pur-
pofe, and its pitchy furface is expeditioufly, and without
difficulty formed by the bruifer, the apparatus is there-
fore not enlarged.

Of rough grinding the fpeculum.

The tool by which the rough furface of the metal is
rendered fmooth and fit for the hones, is belt made of lead,
ftiffened with about a fifth or fixth part of tin. This tool
Ihould be at leaft a third more in diameter than the metal
which is to be ground ; and for one of any fize, not lefs
than an inch thick. It may be cemented upon a block
of wood, in order to raife it higher from the bench.

This leaden tool being caft, it mult be fixed in the lathe,
and turned as true as it is poffible, by the gage, to the
figure of the intended fpeculum, making a hole or pit in

the

of Metals for refle£ling Telef copes. 305

the middle, as a lodgment for the emery, of about an inch
diameter for a metal of four inches : when this is done,
deep grooves mult be cut acrofs its furface with a graver,
in the manner reprefented in fig. 1. Thefe grooves
will ferve to lodge the emery, and by their means the
tool will cut a great deal falter. There is no occafion
to fear any alteration in the convexity of this tool by
working the metal upon it, for the emery will bed itfelf
in the lead, and fo far arm the furface of it, that it will
preferve its figure and cut the metal very fait. Any kind
of low handle, fixed on the back of the metal with foft
cement, will be fufiicient; but it fhould cover two-thirds
of its back to prevent its bending. This way of working
will cut the metal falter, and with more truth, than the
method defcribed by Dr. smith; for fhould the fur-

* f

face and rough parts be attempted to be ground off by
a common grind-ftone by hand, though you did it as
near the gage as poffible, yet the metal would be fo
much out of truth when applied to the fucceeding tool,
that no time would be faved by it. I ufed to employ
a common labourer for this purpofe, who foon acquired
fuch a dexterity at working upon this tool, that in two
hours time he would give a metal of four inches dia-
meter fo good a face and figure as even to fit it for the
hones. When all the fand-holes and irregularities on the
face of the metal are ground off, and the whole furface
Vol. LXVII. R r is

30 6 Mr. mudge on the ConJlruSUon

is fmooth and regularly figured, the fpeculum is then
ready for the brafs grinder, and muft be laid afide for the
prefent.

'The manner of forming the brafs-grinding tool.

The following is the method I have always purfued.
Procure a round flout piece of Hamburgh brafs, at
molt a fixth part larger than the metal to be poliilied ;
and let it be well hammered into a degree of convexity
(by the affiftance of the gage) fuitable to the intended
fpeculum. Having done this, fcrape and clean the con-
cave fide fo thoroughly that it may be well tinned all
over ; then caft upon it, after it has been prefied a proper
depth into the fand, the former cornpofition of tin and
lead, in fuch quantity, that it may (for a fpeculum
of four inches diameter) be at leaf! an inch and an half
thick, and with a bafe confiderably broader than the top,
in order that it may ftand firmly upon the bench in the
manner hereafter to be defcribed. This being done, it
muft; be fixed and turned in the lathe with great care,
and of fuch a convexity as exactly to fuit the concave
gage, which we fuppofe already made. It will be necef-
fary to be more careful in forming this than the former
tool, and efpecially that no rings be left from the turning;

nor

i

of Metals for reflecting felef copes. 307

nor will the fucceeding hone tool require fo much exadt-
nefs, as any defe&s in turning, will, by a method hereafter
mentioned, be eafily remedied; but any inequality or want
of truth in the brafs tool will occafion a great deal of trou-
ble before it can be ground out by the emery. This tool
muft have a hole (fomewhat lefs than that in the metal
to be worked upon it) in the middle, quite through to
the bottom. When this tool is finiihed off in the lathe,
its diameter fhould be one-eighth wider than the metal.

Hozv to form the bed of hones , or the third tool.

Having chofen the kind of hones, and the bell too, of
the fort recommended in smith’s Optics; they fhould
be cemented in fmall pieces (in a kind of pavement
agreeably to his directions) upon a thick round piece of
marble, or metal made of lead and tin like the former
compofition (which is what I have always ufed) in fuch
a manner, that the lines between the (tones may run
ftraight from one fide to the other; fo that, placing the
teeth of a fine faw in each of thefe divifions, they may
be cleared from, one end to the other of the cement
which rifes between the ftones. This bed of hones
1 he be at leaft a fourth part larger than the metal
which is to be ground upon it. The furface of the

R r 2 metal

go8 Mr. mudge on the Conjlruflion

metal upon which the hone pavement is to be cemented
may or may not, as you pleafe, be turned of a convexity
fuitable to the gage, though I have never taken that
trouble. As foon as the hones are cemented down, and
the joints cleared by the faw, this tool mull be fixed in
the lathe, and turned as exactly true to the gage as pof-
fible ; which done, it muft be laid afide for the prefent.
The next tool to be made is the bruifer.

The manner of forming the bruifer, the fourth and

lafl tool.

This tool lhould be likewife made of thick flout brafs
like the former, perfectly found, about a quarter of an
inch thick, and hammered as near to the gage as pofli-
ble. It fhould be then fcraped, cleaned, and tinned on
the convex fide, as the former tool was on the concave,
and the fame thicknefs of lead and tin caft upon it. The
general fhape of this fhould differ from the former ; for
as that increafed in diameter at the bottom for the fake
of Handing firmly, fo this fhould be only as broad at
bottom as at top, as it is to be ufed occafionally in both
thofe petitions. When this tool is fixed in the lathe, and
turned off concave to the convex gage with great truth

likewife,

of Metals for reflecting T ’elej 'copes. 309

likewife, its diameter ought to be the middle fize be-
tween the hones and the polilher.

Having with the lathe roughly formed the convex
brafs grinder, the bed of hones, and the concave bruifers,
the convex and concave brafs tools and the metal muft
be wrought alternately and reciprocally upon each other
with fine emery and water, fo as to keep them as nearly
to the fame figure as poffible, in order to which fome
walhed emery muft be procured. This is beft done by
putting it into a phial, which muft be half filled with
water and well fhaken up, fo that, as it fubfides, the coarfeft
may fall to the bottom firft, and the fineft remain at the,
top : and whenever frefh emery is laid on the tools, the
beft method (which we fhould alfo obferve with the
putty in polifhing) will be, to fhake gently the bottle.,
and pour out a fmall quantity of the turbid mixture.

Of grinding the fpeculum , the brafs tool , and the bruifer

together.

All the tools being ready, upon a firm poft in the
middle of a room, you are to begin to grind the brafs con-
vex tool with the bruifer upon it, working the latter crofs-
ways, with ftrokes fometimes acrofs its diameter, at others-
a little to the right and left, and always fo fliort that the

bruifers

3io Mr. Mudge on the Conjlruclion

br uifers may not pafs above half an inch within the fur-
face of the brafs tool either way, fhiftiug the bruifer
round its axis every half dozen lirokes or thereabout.
You muft likewife, every now and then, fhift your own
pofition, by walking round, and working at different fides
of the brafs tool ; at times the ftrokes fhould be carried
round and round, but not much over the tool : in fhort,
they muft be directed in fuch a way, and the whole
grinding conducted in fuch a manner and with fuch
equability, that every part of both tools may wear
equally. This habit of grinding, as ■well as the future
one of polifhing, will be foon acquired. When you have
wrought in this manner about a quarter of an hour with
the bruifer upon the tool, it will be then neceffary to
change them, and, placing the bruifer upon its bottom,
to work the convex tool upon that in the fame manner.

When by working in this equable manner, alternately
with the bruifer and tool, and occafionally adding frefh
emery, you have nearly got out all the veftiges of the
turning tool, and brought them both nearly to a figure,
it will be then time to give the fame form to the metal.
This muft be done by now and then grinding it upon
the brafs tool with the fame kind of emery, taking care
however, by working the two former tools frequently
together, to keep all three exactly in the fame curve.

The

of Metals for reflecting Aelef copes. 3 1 1

The beft kind of handle for the metal is made of lead,
a little more than double its thicknefs, and fomewhat
lefs in diameter, of about three pounds weight, with a
hole in the middle (for reafons to be fliewn hereafter) a
little larger than that in the metal : this handle fhould be
cemented on with pitch. The upper edge of this weight
mull be rounded off, that the fingers may not be hurt;,
and a groove, about the bignefs of the little finger, be
turned round juft below it, for the more conveniently'
holding and taking the metal off the tools.

Abe manner of figuring the metal upon the bones .

When the bruifer, brafs tool, and metal, are all
brought to the fame figure, and have all a true good
furface, the next part of the procefs is to give a
correct fpherical figure and a fine face to the metal,,
upon the hones. It will be neceffary to premife, how-
ever, that the hones fhould be placed in a veffel of water,
with which they fhould be quite covered for at leaft an
hour before they are ufed, otherwife they will be per-
petually altering their figure when the metal comes- to
be ground upon them. The fame precaution is alfo ne-
ceffary, if you are called off from the work while you are

grinding r

3i3 Mr. mudge on the Conjlru&ion

grinding the metal, for if they he fuffered to grow dry,
the fame inconvenience will arife.

In order to give a proper figure to the hones, and
exactly fuitable to that of the brafs tool, bruifer, and me-
tal, when the hones are fixed down to the block, fome
common flour emery (unwalhed) with a good deal of
water muft be put upon them, and the bruifer being
placed upon the hones and rubbed thereon with a few
firokes and a light hand, the inequalities of the ftone w ill
be quickly worn off; but as a great deal of mud will be
fuddenly generated, it muft be wafhed off every quarter
of a minute with a great deal of water. By a repetition
of this, two or three times, the hones (being of a very foft
and friable fubftance) will be cut down to the figure,
without wearing or altering the bruifer at all. Though
this bufinefs may be quickly done, and can be continued
but for a few ftrokes at a time, I need not fay that it is
neceffary that thofe ftrokes be carried in the fame direc-
tion, and with the fame care, which was obferved in
grinding the former tools together.

As foon as the hones have received the general figure
of the bruifer, and all the turning ftrokes are worn out
from them, the emery muft be carefully waflied off; in
order to which, it will be neceffary to clear it from the
joints with a brufti under a ftream of water. The bruifer

and

2

of Metals for reflecting Telefcopes. 313

and metal muft be like wife cleared in the fame manner,
and with equal care, from any lurking particles of emery.

The hones being fixed down to the block, you now
begin to work the bruifer upon them with very cautious,
regular, fhort ftrokes, forward and backward, to the
right and left, turning the axis of the bruifer in the hand
while you move round the hones, by fluffing your pofi-
tion, and walking round the block. Indeed the whole
now depends upon a knack in working, which fhould be
conduced nearly in the following manner. Having
placed the bruifer on the centre of the hones, Hide it in
an equable manner forward and backward, with a ftroke
or two diredtly acrofs the diameter, a little on one fide,
and fo on the other; then fluffing your pofition an eighth
part round the block, and having turned the bruifer
in your hand about as much, give it a ftroke or two
round and round, but not far over the edges of the hones,
and then repeat the crofs ftrokes as before : thofe round
ftrokes (which ought not to be above two or three at
moft) are given every time you ftiift your own pofition
and that of the metals, previous to the crofs ones, in
order to take out any ftripes either in the hones or
bruifer, which may be fuppofed to be occafioned, by the
ftraight crofs ftrokes. During the time of working, no
mud muft be fuffered to colledt upon the hones, fo as to

Vol. LXVII. Sf deftroy

314 .Mr. mudge on the ConJlruBion

deftroy the perfect contadl between the two tools; and
therefore they muft every now and then be walked clean
by throwing fome water -upon them. When by work-
ing in this manner all the emery ftrokes- are ground oft*
from the bruifer, and it has acquired a good figure and
clean furface, you may then begin with the metal upon
the hones, in the fame cautious manner, walking off the
mud as faft as it collects, though that will be much lefs
now than when the bruifer was ground upon them...
Every now and then, however, the bruifer muft be rube-
fied gently and lightly upon the hones, which will as it
were, by lharpening them and preventing too- great
fmoothnefs, occafion them to cut the metal much rafter. .

When, after having fome time cautioully wrought in
the manner before deferibed, the hone-pavement has
uniformly taken out all the emery ftrokes, and given a
fine face and true figure to the metal, which will be
pretty well known by the great equality there is in the
feel while you are working, and by which an expe-
rienced workman will form a pretty certain judgment ;
having proceeded thus far, I fay, you may then try your
metal, and judge of its figure by this more certain
manner.

Wafh the hone pavement quite clean; then put the
metal upon the center of it, and give two or three light

1 ftrokes

of Metals for refleSling Telef copes. 315

ftrokes round and round only, not carrying, however, the
edges of the metal much over the hones ; this will take out
the order of ftraight ftrokes : then having again wafhed
the hones, and placed the fpeculum upon their center,
with gentle preffure, Aide it towards you till its edge be
brought a little over that of the hones, then carry it
quite acrofs the diameter as far the other fide, and having
given the metal a light ftrolce or two in this direction,
take it off the tool. The metal being wiped quite dry,
place it upon a table at a little di fiance from a window;
ftand yourfelf as near the window, at fome diftance from
the metal, and looking obliquely on its furface, turn it
round its axis, and you will fee at every half turn the
grain given by the laft crofs ftrokes flafh upon your eye
at once over the whole face of the metal. This is as cer-
tain a proof of a true fpherical figure as the operofe and
difficult method defcribed in Dr. smith’s Optics; for as
there is nothing foft or elaftic, either in the metal or in the
hones, this glare is a certain proof of a perfect contact
in every part of the two furfaces; which there could not
be if the fpheres were not both perfect .and precifely the
fame,.

Indeed there is one accidental circumftance which ne-
ceffarily affords its aid in this and every bufinefs of the
like fort ; and that is, that a concave and convex furface

S f 2 ground

3.x:6 M\'m-ueq-e 'vn'tbe Confiruciion..

ground together, though ever io irregular at firft, will
(if thbavorking be uniform and proper, <: onfifting, efpe-

cially at lalt, of crofs ftroh' 3 at : ’ poflible direction-
acrofs the diameter) be formed ...;o :: ions of true and

equal fpheres; had it not been for this lucky neceffity, it-
would .have been impoflible to have produced that cor-
reCtnefs which is eflential in the fpeculum of a good re-
flecting telefcope by any mechanic contrivance what-
ever. For when it is confidered, that the errors in reflec-
tion are four times as great as in refraction, and that the
leaft defect in figure is magnified by the powers of the
inflrument, any thing Ihort of perfection in the figure:
of the fpeculum would be evidently perceived by a want
of diftinCtnefs in the performance.

I mull not, however, quit this article without obferv--
ing, that I all along fuppofe, both in forming the tools,
and at laft figuring the metal (and indeed the fame mult,
be obferved in the future procefs of polifhing) that no
kind of preffure is ufed that may endanger the bending:
or irregularly grinding them; they fhould therefore be
held with a light hand, and loofely between the fingers,,
and the motion given fhould be in a horizontal direction,
with no more preffure than their own dead weight.

Having now finifhed the metal on the hones, and ren-
dered it both in point of figure and furface fit for the

laft

for Metals of reflecting Telefcopes . 317

laft and moft effential procefs, viz, that of polifhing, I
will defcribe it in the bell manner I can ; though many-
little circumftances which will be unavoidably omitted
(and which at the fame time are frequently effential to.
the fuccefs of a mechanic procefs) can only be fupplied
by adlual experience.

The polilhing the fpeculum is the moft difficult and.
effential part of the whole procefs; for every expe-
rienced workman knows, to his vexation, that the moft
trilling error here will be fufficient to fpoil the figure of
his metal, and render all his preceding caution ufelefs. I
have, however, difcovered a method which I lhall explain,
not only of giving the metal a parabolic figure, but alfo of
recovering it when it happens to be injured ; both to be
effected in. the a£t of polifhing, and the former as cer-
tainly as the fpherical figure is given upon the hones.
Indeed, if we conlider rightly, polifhing will be perceived
to be but a kind of grinding with a finer order of ftrokes,
and with a powder infinitely finer than was before ufed
in what is commonly called the grinding. But before I
defcribe this method, which was the refult of many
years experience, I will take the liberty of making fome
few ftriddures on that of Meff. hadley -and moly-
neux, which is followed by the generality of work-

men. .

3 1 8 Mr, mudge on the Conjlruflion

Firft, then, the tool itfelf ufed by them for polifh-
,ing the metal, is formed with infinite difficulty. The
firft defcribed polifher is directed to be made by covering
the tool with farcenet, which is to be faturated with a
folution of pitch in fpirit of wine, by fucceffive applica-
tions of it with a brufh, till it is covered* and by the eva-
poration of the fpirit of wine filled with this extrad of
pitch; the furface is then to be worked down and finifhed
'With the bruifer. This is all very eafy in imagination ;
but whoever has ufed this method (which I have myfelf
tunfuccefsfully feveral times) muft have found it attended
with infinite labour, and at laft the bufinefs done in a
•very unfatisfiadory manner; for the pitch by this procefs
■will be deprived of an effential part of its compofition.
The fpirit of wine diffolves none but the refinous parts
of its fubftance, which is hard and untradable ; and if
you ufe foap or fpirit of wine to foften or diffolve it, it
will equally affed the whole furface, the lower as well as
higher parts of it. And fuppofe that with infinite labour
with the bruifer, it is at laft reduced to a fine uniform
furface, it is neverthelefs too hard ever to give a good
polifh with that luftre which is always feen in Mr.
short’s, and indeed all other good metals. Nor will it
give a good fpherical figure; for a perfed fphere is
formed, as X obferved before, by that intimate accommo-
dation

of Metals for reflecting 'Telefcopes . 319

dation arifing from the. wear and yielding of both tool :
and metal; whereas in this method, there is fuch a ftub-
bornnels in the polifher, that the figure of the metal,
good or bad, muft depend upon the truth of the former, ,
which is very feldom perfect.

If the polifher be made in the fecond manner propo-
fed, by flraining the pitch through an outer covering,,
which is afterwards to be ftripped off, the fuperficies of
pitch and farcenet is- fo very thin, that the putty, work-
ing into them, forms a furface hard and untradlable, fo
that it is impoffible to give the fpeculum a fine polifh.
Accordingly all thofe metals which are wrought that way
have an order of fcratches inftead of polifh, difcovering
itfelf by a grey ifli vifible furface. Befides, fuppofing this
tool perfectly finifhed, and anfwering its purpofe ever fb
well, it is impoffible. it can produce in .the fpeculum any
other than a fpherical .figure ; and indeed nothing elfe is
expected from this method, as very evidently appears by
the experiment recommended to afeertain the truth of
the figure. You are directed to place a, final! luminous
object in the center of the fphere of which the metal is
a fegment, and then having adjufled an eye-glafs at the
diftance of its own focal length from the object, and fo
fituated that the image of the objedt formed by the fipe—
culum may be. vifible to the eye, you are to judge of the
3 perfect

320 Mr. mudge on the ConJlruBlon

perfect figure of the metal by the fharpnefs and diftindt-
nefs with which the image appears. From hence it is
very evident, that as the object and image are both diftant
from the metal by exactly its radius, nothing but a true
fpherical figure of the fpeculum can produce a fharp
diftindt image.; and that the image could not be diftinct
if the figure of the fpeculum were parabolic. Confe-
quently, if the fame fpeculum ufed in a telefcope were
to receive parallel rays, there would neceffarily be a con-
fiderable aberration produced, and a confequent imper-
fiedtion in the image. Accordingly, there never was a
good telefcope made in this manner; for if the number
of degrees, or the portion of the fphere of which the
great metal is a part, were as confiderable as it ought to
be, or as great as Mr. short allowed in his metal, the
inftrument would bear but a very low charge, unlefs a
great part of the circumference of the metal were cut off
by an aperture, and the ill effedts of the aberration by
that means in fome meafure prevented.

If ever a finifhed metal turned out without this defied!,
and has been found perfedtly lharp and diftinct, it muft
have been owing to an accidental parabolic tendency, no
ways the natural refult of the procefs, and therefore quite
unexpedted, and moft probably unknown, to the work-
man.

Without

f- df Metals for refl'eSling feTef copes. 3 2 1

" 'Without enlarging, therefore, oh the difficulty 'of the
; above "procefs, and the impoffibility of giving the fpecu-
lum fhecorreCtnefs" and the' kind of figure "effentially
neceffary toa- good telefcope, I will defcribe (by way of
• iutrodudtion to the 'fucceeding' directions) tlie fteps by
which I was led to a certain and e'afy method of giving a
proper and correct parabolic figure to the metal, even
though ;it cameoff imperfeCt from the hones, and an ex-
quifite polifli at the fame - tim e .

Having made many efforts in the former method,
which by no means pleafed me for the reafons above-men-
tioned; and having obferved, from feme of Mr. short’s
telefcopes which fell into my hands, that the highliiftre of
the polifli could never have been produced in the manner
above- deferibed, but by fome fofter and more tender fub-
ftance; and at the fame time recollecting, that Sir Isaac
newton had given an account in his Optics of his hav-
ing finifhed fome metals, and confiderably mended the
objeCt glafs of a refraCtor, by working both upon a tool
whofe furface had been covered with common pitch
about the tMcknefs of a gfoat; reflecting, I fay, upon

■ thefe matters (coarfe and uncertain as this method ap-
peared at firft fight) 1 was determined to try whether I

■ could not get rid of my embarraffment, by a mode of

■ operation fomewhat fimilar. Accordingly, fhertening

• Vol. LXVII. T t Dr.

322 Mr. mudge on the ConJlruElion

Dr. smith’s procefs, I made a fet of tools in the manner
before defcribed, except that I was obliged to make fome
fubfequent alteration in the poliflier which I ill all pre-
fen tly defcribe. Having given a good fpherical figure
to the brafs tool and the bruifer, and likewife to the
metal upon the hones, and made the brafs convex tool fo
hot as juft not to hurt the finger, I tied a lump of com-
mon pitch (which fhould be neither too hard nor too
foft) in a rag, and holding it in a pair of tongs over a ftill
fire where there was no rifing duft, till it was ready to
ftrain through the linen, I caufed it to drop upon the
feveral parts of the convex tool, till I fuppofed it would
cover the whole furface about double the thicknefs of a
fhilling; then fpreading the pitch as equally as I could, I
fuffered the poliflier (by which name I fliall for the
future call this tool) to grow quite cold. I then warmed
the bruifer fo hot as almoft to burn my fingers, and hav-
ing fixed it to the bench with its face upwards, I fud-
denlv placed the poliflier upon it, and quickly flid it off ;
by this means rendering the furface of the pitch more
equal. The pitch is then to be wiped off from the bruifer
with a little tow; and by touching the furface with a
tallow candle, and wiping it a fecond time, it will be then
perfectly clean and fit for a fecond procefs of the fame
fort, which muft again be performed as quickly as poflible ;

and

of Metals for reflecting ti defcopes. 323

and this is ordinarily fufficient to give a general figure to
the furface of the pitch. The bruifer and polifher. are
then fuffered to grow perfectly cold, when the pitch,
conlidering what has "been taken off, will be about the
thicknefs of a fliilling.

It is however here neceffary to obferve, that the pitch
Ihould be neither very hard and refinous, nor too foft; if
the former, it will be fo untraftable as not to work
kindly ; and if too foft, it will in working alter its figure
falter than the metal, and too readily fit iilelf to the ir-
regularity of . its figure, if it have any. When both tools
were perfectly cold, I gave the polifher a gentle warmth,
and then fixed the bruifer to the block with its face up-
wards; and (having with a large camel’s-hair brufh
fpread over the face of the poliiher a little water and foap,
to prevent flicking) with fhort, ftraight, and round
ftrokes I worked it upon the bruifer, every now and then
adding a little more water and foap, till the pitch upon
the polifher had a fine furface, and the true form of the
bruifer; and this I continued to do till they both grew
perfectly cold together : in this manner the poliiher was
perfectly formed in about a quarter of an hour. But
here a difficulty arofe : when I begun to polilh the metal,

I found that the edge of the hole in the metal collected
the pitch towards the middle of the polifher; and

T t 2 though

O

32.4 -A-//', mudge on the Conjlrn&ion

though in this method of working I could give an ex-
quilite poliih, as the putty lodged itfelf in the pitch
exceedingly well, yet the figure of the metal was injured
in the middle, nor did indeed the work go on with that
equability which is the infeparable attendant on a good
figure. In order to obviate this difficulty, I call fome
metals with a continued face, the holes not going quite
through, within perhaps the thicknefs of a fix-pence.
I finiffied two or three metals of this fort, and the work
promifed and went on very well ; but when I came to open
the holes, which I did with the utmoft caution, I found
the metals ffiort of perfection ; which I attributed to an
alteration of the figure from the removal of even that fmall
portion of metal after the fpeculum had been finiffied.
.This I do fuppofe was in fome meafure the reafon why I
fpoiled a very diftinCt and perfect two-foot metal, which
bore a charge of two hundred times, only by opening
the fharp part of the edge of the hole, becaufe I thought
it bounded the field : fo eflentially neceffary is an exqui-
fite correCtnefs of figure in the fpeculum of a pcrfeCt
refiebtor.

This experiment not fucceeding, inftead of calling the
metal without a hole, I made one quite through the
middle of the poliffier, a little lefs than that in the Ipe-
culum. This perfectly anfwered the purpofe; no more

incon-

' of Metals for reflecting I’elefcopes. 325

inconvenience arofe from the gathering of the pitch (for
it had now no greater tendency to collect at the center
than the tides) and I finilhed feveral metals fucceffivelv,
excellent both in point of figure and polifh ; one of thole
of two inches diameter and 7,5 focal length, bore a charge
of fixty times. and upwards, which when mounted in a
telefcope I gave to my brother. This telefcope underwent
Mr. short’s examination, who was pleafed to remark
only, that he thought he had made one more diftindt.

I mult obferve, that in this method of working the
polilhing goes on in an agreeable, uniform, and fmooth
manner; and that the fmall degree of yielding in the
pitch (which is actually not more than the wearing of
the metal) produces that mutual accommodation of
furfaces fo neceffary to a true figure. In the beginning
of the polifh, and indeed for fome time during the pro-
grefs of it (always remembering now and then to move
the metal round its axis) I worked round and round, not
far from and always equally diftant from the center, ex-
cept that every time, previous to the drifting the metal
on its axis, I ufed a crofs ftroke or two ; and when the
polifh was nearly compleated, I moftly ufed crofs ftrokes,
giving a round ftroke or two likewife every time I turned
the metal on its axis. I oblerved in this method of work-
ing, that the metal always polilhed fafteft in the middle;

info much,

326 Mr, mudge on the Confiruclion

infomuch, that half or two-thirds of it would be com-
pletely polifhed when the circumference of it was fcarcely
touched by the tool. Obferving this in fome of the firft
metals, and not confidering that this way of polifhing
was in faff a fpecies of grinding, and as perfect as that
upon the hones, I went on reluctantly with the work,
almoft defpairing of being able to produce a good
figure. However, I always found myfelf agreeably
deceived; for when the polifh was extended to the
edge, or within the tenth of an inch of it, I almoft
conftantly found the figure good, and the performance
of the metal very diftinCt. But this fame cficumltance of
apparent defeCt in the metals, was in faCt that to which
their perfection was owing; for they all, contrary to my
expectation, turned out parabolic. However I did not
for a great while know any certain way of giving that
degree of parabolic tendency which was juft neceflary,
and which will be defcribed hereafter. It was a long
time before I got rid of my prejudice againft this appa-
rent imperfection in the procefs,. or could reconcile my-
felf to the irregular manner in which the polifh pro-
ceeded ; for I looked upon it as a certain fource of error,
and notwithftanding I faw it eventually fucceed, yet
whenever I chanced to find that a metal, when firft ap-
plied to the polifher, took the polifh equally all over,

and

of Metals for reflecting felef copes . 527

and confequently the whole bufinefs did not take up
above ten minutes; under thofe circumftances, I fay, I
always ufed to pleafe myfelf with the expe (Station of a
correct figure, at lead as much fo as the metal had re-
ceived from the hones, where the furface was but juft
and equally taken off by the putty ; but in this I con-
ftantly found myfelf deceived, and the metal turned out
good for nothing. In fhort, at this time, though I fpe-
culatively knew that a parabolic figure was neceffary to
a perfect image, I yet confidered it as of little practical
confequence.

From the foregoing experiments, and a number of
fueceeding trials, I at length difcovered a certain way of '
giving a correct parabolic figure, and an exquifite polifli
at the fame time. This, which I have ftrong reafons to
believe was Mr. short’s method, I will now defcribe in
as few words as I can..

How to potijh the Speculum .

It is firft neceffary to obferve, that, in order to avoid
the detrimental intrufions of any particles of emery, it
would not be right to polifh in the fame room. where the
metal and tools were ground, nor in the fame deaths
which were worn in the former proceis ; at leaft it. would

r ■$ % 8 z -Mr. * mu.dge , on 'the ConjlruBwn

neceffary; to. keep the. bench quite wet, to .prevent any
puhifrpna jifing.

" Haying them made the polifher. by coating the brafs
- convex tool n equally <; with pitch, which we fuppofe
Smoothed and finifhed with the brafs tool in the manner
before defcribed, and which is . a very eafy procefs, the
whole operation is begun. and. finilhed in the following
manner.

The leaden weight or handle upon the back of the
inetal Hr on! d be divided into eight parts, by fo many deep
ftrokes of a graver upon the upper furface of the lead,
marking each ftroke with the numbers i, 2, 3, 4, and fo
on, that the turns of the metal in. the hand may be
known to be uniform and regular.

To prevent any mifcliief from coarfe particles of
putty, Lai ways. walla it immediately before ufing. In order
, .£0 this, put about half an ounce of putty into an ounce
phial, and fill it two-thirds with water; then having
. Ihaken the whole, let the putty fubfide, and flop the
; bottle with a cork.

'lira tea-cup with a little water j there fhould be a full-
fized camel’s-hair brufh, and a piece of dry clean foap in
a galley- pot : a foft piece of fpunge will alfo be neceflary.
Thefe, as well as the metal bruifer and polifher, fhould
. be cqnflantly covered from dull.

The

of Metals for refle&ing felef copes. 3 29

The polifher being fixed down, and the camel’s-hair
brufti, being firft wetted and rubbed a little over the foap,
let every part of the tool be bruflied over therewith;
then work the bruifer with fhort, ftraight, and round
ffrokes, lightly upon the tool, and Continue to do fo,
now and then turning it, till the poll fltc-r have a good face,
and be fit for the metal. Then having fhakenupthe putty
in the phial, and touched the polifher in five or fix places
with the cork wetted with that and the water, place the
bruifer upon the tool, and give a few ftrokes upon the
putty to rub down any gritty particles; after which,
having removed it, work the metal lightly upon the po-
lifher round and round, carrying the edges of the fpecu-
lum, however, not quite half an inch over the edge of
the tool, and now and then with a crofs ftroke.

The firft putty, and indeed all the fucceeding appli-
cations of it, fhould be wrought with a con fider able
while; for if time be not given for the putty to bed it-
felf in the pitch, and any quantity of it lie loofe upon the
polifher, it will accumulate into knobs, which will in-
jure the figure of the metal : and therefore as often as ever
fuch knobs arife, they muft be carefully fcraped off with
the point of a penknife, and the loofe fluff taken away
with the brufh. After the putty is well wrought into the
pitch, fome more may be added in the fame manner, but
Vol, LX VII. U u

never

330 Mr. mudge on the ConJlruBion

never much at a time, and always remembering to work
upon it firft with the bruifer, for fear any gritty particles
may find their way upon the polilher. If the bruifer be
apt to flick, and do not Hide fmoothly upon the. pitch, the
furface of either tool may be occafionally brufhed over
with the foap and water, but it muft be remembered that
the wet brufh muft be but lightly rubbed upon the foap.

In the beginning of this procefs Iktle.effedt is pro-
duced, and the metal does not feem to polifh faft, in fome
meafure owing to its taking the polifh in the middle, and
perhaps becaufe neither that nor the bruifer move evenly
upon the polifher : but a little perfeverance will bring the
whole into a good temper of working ; and, when the
pitch, is well defended by the coating of the putty, the
procefs will advance apace, and the former acquiring pof-
fibly fome little warmth, the metal moves more agreea-
bly over it, with an uniform and regular fruftion. All this
while the metal muft have no more preflure than that
which it derives from its- own weight and that of the
handle ; and the polifher muft never be fuffered to grow
dry, but, as often as it has any tendency to do, fo, the edges
of it muft be moiftened with the hair-pencil; and .now
and then, even when frefh putty is not laid on, the fur-
face of the polifher fhould be touched with the, brufh to
keep it moilh

4

When

of Metals for reflecting ti’elef copes. 331

When the polifh of the metal nearly reaches the
edge (for it always, as I faid before, begins in the mid-
dle) you muft alter your method of working; for’ now
the round ftrokes muft be gradually altered for the
Ihort and ftraight ones. Supposing then you are juft
beginning to alter them ; after having put on frefh putty,
and gently rubbed it with two or three ftrokes of tiie
bruifer, you place the metal on the tool, and after a ftroke
or two round and round, give it a few forward and back-
ward, and from ftde to fide, but with the edges very little
over the tool; then having turned the metal one-eighth
round in your hand, and having moved yourfelf as much
round the block (which muft be remembered throughout
the whole procefs) you go on again with a ftroke or two
round, to lead you only to the crofs ftrokes, which are
now to be principally ufed, and with more boldnefs.
After this has been done fome time, the metal will begin
to move ftiffly as the friftion now increafes, and the fpe-
culum polifhes very beautifully arid faft ; and the whole
furface of the polifhing tool will be equally covered over
with a fine metallic bronze. The tool even now muft
not be fuffered to become dry ; a fingle round ftroke in
each of your ftations and turnings of the metal will
be fufficient, and the reft muft all be crofs ones, for we
are completing a circular figure. You muft now be very

U u 2 diligent,

332 Mr. mudge on Jhe ConJlruElion

diligent, for the polifher drying, and the friction in-
creating very fall, the bufinefs of the fpherical figure is
nearly at an end. As the metal wears much, its furface
mull be now and then cleaned, with a piece of fhammy
leather, from the black fluff which collects upon it;, and
the polifher likewife from the fame matter, with a foft
piece of wet fponge. You will now be able to judge of
the perfect fpherical figure of the metal and tool, when
there is a perfect correfpondence between the furfaces,
by the fine equable feel there is in working, which is
totally free from all jerks and inequalities. Having pro-
ceeded thus far, you may put the laft finifhing to this

\

figure of the metal by bold crofs ftrokes, only three or
four in the directions of each of the eight diameters,
turning the metal at the fame time: this mull be done
quickly, for it ought, in this part of the procefs particu-
larly, to be remembered, that, if you permit the tool to
grow quite dry, you will never be able, with all your
force, to feparate that and the metal, without deftroying
the polifher by heat.

The metal has now a beautiful polilh. and a true
fpherical figure, but will by no means make a fharp dif-
tindt image in the telefcope : for the fpeculum (if it be
tried in the manner hereafter recommended) will not be
found to make parallel rays converge without great

aberration ;

of Metals for refle&ing ft def copes. 333

aberration ; indeed the deviation will be fo great, as to be
very fenfibly perceived by a great indiftindtnefs in the
image.

How to give the parabolic figure to the metal.

In order then to give the fpeculum the laft and finilh-
ing figure, which is done by a few ftrokes, it muft be
particularly remarked, that by working the metal round
and round, the fphere of the polilher by this means
growing lets, it wears fafteft in the middle : and as a
legment of a fphere may become parabolic, by open-
ing the extremes gradually from within outwards, fo
it may be equally well done by increafing the curva-
ture in the middle, in a certain ratio,, from without kw
wards.

Suppofing then the metal to be now truly fpherical,
flop the hole in the polilher, by forcing a cork into it
underneath, about an inch, fo that it do not reach quite
to the furface; and having w allied off any mud that may
be on the furface of the took with a wet foft piece of
fponge, whilft the furface of it is a little moift, place the
center of the metal upon the middle of the polilher;
then having, with the wet brulh, lodged as much water
round the edge of the metal as the projecting edge will
. hold.

334 A7r. mudge cn the ConflruSiion

hold, fill the hole of the metal audits handle with water,
to prevent the evaporation of the moifture, and the con-
fequent aclhefion between the fpeculum and polifher, and
let the whole reft in this ftate two or three hours: this
will produce ah intimate contact between the two, and
by parting, with any degree of warmth they may have
. acquired by the vicinity of the operator, they will grow
perfectly cold together.

- By. this time you may.pufh out the cork from the po-
lithe r, to difeharge the water, and give the metal the pa-
. .xabolic figure in the following manner.

Move the metal gently and ilowly at firft, a very little
round the centre of the polifher (indeed after this reft it
will move ftiflly) then increafing by degrees the dia-
meter of thele ftrokes, and turning the metal frequently
round its axis, give it a larger circular motion, and
this without any preflure but its own weight, and
holding it loofely between the fingers: this manner
of working may iafely be continued about two mi-
nutes, moving yourfelf as ufual round the block,
and carrying the round ftrokes in their increafed
and largeft ftate, not more than will move the edge
of the metal half an inch or fiv^-eighths over the took
The fpeculum muftnot all this while be taken off from
the polifher; and confequently no ffefh putty can be

added.

of Metals for refledling TeleJ copes, 335

added. It will not be fafe to continue this motion longer
than the time above-mentioned ; for if the parabolic ten-
dency be carried the leaft too far, it will be impoSTible ta
recover a true figure of that kind but by going through the
whole procefs for the fpherical onein the manner before
defcribed, by the crofs Strokes upon the polilher, which
takes a great deal of time. However, when there is occa-
sion, it may be done; and I have myfelf feveral times
recovered the circular figure, when I had inadvertently
gone too far with the parabolic and ultimately finished
thejnetal on the polilher without the ufe of the hones. .

To try the true figure of the metal.

It will now be proper to try the figure of the Specu-
lum, and that is always heft done by placing it in the
telefcope it is intended for. In order to this, I ufe the in-
strument as a kind of microfoope, placing theobjeff,
however, at fuch a distance that the rays may be nearly
parallel. At about twenty yards a watch -paper, or feme
fuch object, on which there, are fome very fine hair
Strokes of a graver, is fixed up. The lead muft be then
taken.off from the back of the- lpeculuin y which is belt
done by placing the edge of a knife at the junction of
the lead and metal, when, by Striking the back of it with a

Slight

Mr. mudge on the Conjlruftion

flight blow, the pitch immediately feparates, and the
handle drops off; the remaining pitch may be fcraped
oflF with a knife, taking care that none of the dull flick
to the polifhed face of the metal.

Having placed the fpectilum in the cell of the tube,
and directed the inftrument to the object, make an annu-
lar kind of diaphragm with card-paper, fo as to cover a
circular portion of the middle part of the metal between
the hole and the circumference, equal in breadth to about
an eighth part of the diameter of the fpeculum : this
paper ring fliould be fixed in the mouth of the telefcope,
:and remain fo during the whole experiment, for the part
of the metal covered by it is fuppofed to be perfect, and
therefore unemployed.

There muft likewife be two other circular pieces of
card-paper cut out, of fuch fizes, that one may cover the
center of the metal by completely filling the hole in the
daft defcribed annular piece ; and the other, fuch a round
piece as fhall exadtly fit into the tube, and fo broad as
that the inner edge may juft touch the outward circum-
ference of the middle annular piece. It would be con-
venient to have thefe two laft pieces fo fixed to an axis
that they may be put in their places, or removed
from thence fo eafily as not to difplace or lhake the
3 .inftrument.

of Metals for refteBing felef copes. 337

inftrument. All thefe pieces therefore together will
completely Hint up the mouth of the telefcope.

Let the round piece which covers the center of the
metal, or that which has no hole in it, be removed; and,
by a nice adjuftment of the fcrew, let the image (which
is now formed by the center of the mirror) be made
as iharp and diftindt as poffible. This being done,
every thing elfe remaining at reft, replace the central
piece, and remove the outfide annular one, by which
means the circumference only of the fpeculum will be
expofed, and the image now formed will be from the
rays reflected from the outfide of the metal. If there be
no occafion to move the fcrew and little metal, and the
two images formed by thefe two portions of the metal
be perfectly fharp and equally diftindt, the fpeculum is
perfedt, and of the true parabolic curve; or at leaft the
errors of the great and little fpeculum, if there be any,
are corredted by each other.

If, on the contrary, under the laft circumftance, the
image from the outfide of the metal fhould not be dif-
tindt, and it fhould become neceflary, in order to make it
fo, that the little fpeculum be brought nearer, it is plain
that the metal is not yet brought to the parabolic figure ;
but if, on the other hand, in order to procure diftindtnefs,
you be obliged to move the little fpeculum farther oft', then
the figure of the great fpeculum has been carried beyond
Vol. LXVII. Xx the

338 Mr. mudge on the ConJlruBion

the parabolic, and hath affumed an hyperbolic form.
When the latter is the cafe, the circular figure of the
metal muff be recovered (after having fixed on the han-
dle with foft pitch) by bold crofs ftrokes upon the po-
liiher, finifhing it again in the manner above defcribed.
If the fpeculum be not yet brought to the parabolic form,
it muff cautioufiy have a few more round ftrokes upon
thepolifher; indeed a very few of them in the manner be-
fore defcribed make in effect a greater difference in the
fpeculum than would be at firft imagined. If a metal of
a true fpherical figure were to be tried in the above men-

*

tioned manner in the telefcope (which I have frequently
done) the difference of the foci of the twTo fegments of
the metal would be fo confiderable, as to require two or
three turns of the fcrew to adjuft them ; fo very great is
the aberration of a fpherical figure of the fpeculum, and fo
improper to procure that fharpnefs and precifion fo ne—
eeffary to a good reflecting telefcope.

This is by no means the cafe with the object glaffes of
refractors ; for befides that they are in fa£t never fo dif-
tinft as weli-finifhed refleftors, the apertures of them
are fo exceedingly fmall, compared to the latter, and the
number of degrees employed fo very fmall, that the in-
convenience of a fpherical figure is not fo much per-
ceived. Accordingly we obferve in the generality of
a reflectors

of Metals for reflecting Telef copes. 339

reflectors (whofe fpecula, unlefs by accident, are always
fpherical) that the only true rays which form the dif-
tinCt image arife from the middle of the metal : and un-
lefs the defect be remedied by a confiderable aperture,
which deftroys much light, the falfe reflection from the
infide of the metal produces a greyifh kind of hazinefs,
which is never feen in Mr. short’s or indeed in any
good telelcopes.

Suppofing that the two foci of the different parts of the
metal perfectly coincide, and that, by the union of them
when the apertures are removed, the telefcope thews
the objects very fharp and diftinCt, you are not however
even then to conclude that theinflrument is not capable of
farther improvement; for you will perceive a fen Able
difference in the fharpnefs of the image, under different
pofitions of the great fpeculum with refpeCt to the little
one, by turning round the great metal in its cell, and
oppofing different parts of it to different parts of the little
metal, correcting by this means the error of one by the
other. This attempt fhould be perfevered in for fome
time, turning round the great fpeculum about one-fix-
teenth at a time, and carefully obferving the moft diftinCt
fituation each time the eye-piece is fcrewed on : when,
by trying and turning the great metal all round, the
diftinCteft pofition is difcovered, the upper part of the

X x a metal

340 Mr. mudge on the Conjlruci'wn

metal ihould be marked with a black ftroke, in order
that it may always be lodged in the cell in the fame por-
tion. This is the method Mr. short always ufed; and the
■ caution is of fo much confequence, that he thought it
necelfary to mention it very particularly in his printed
directions for the ufe of the inftrument.

And farther, Mr. short frequently corrected the
errors of the great by the little metal in another way. If
the great fpeculum did not anfwer quite well in the tele-
fcope, he cured that defeCt fometimes by trying the effeCt
of feveral metals fucceffively, by this means correcting
the errors of one by the other; for in feveral of his tele-
fcopes which have puffed through my hands, when
the fizes and powers have been the fame, I have found
that the great metals, though very diftinCt in their pro-
per telefcopes, yet have, when taken out and changed
from one to the other, fpoiled both telefcopes, render-
ing them exceedingly indiftinCt, which could arife from
no other circumftance. For this reafon I fuppofe it
was, that he kept, ready finifhed, a great many large
metals of the fame focal length, fo that, when he wanted
to mount a telefcope, he might from a great choice,
be able to combine thofe metals which fuited each
other beft. I am ftrongly inclined to believe this was the
cafe, not only from the above obfervation, but becaufe

r he

cf Metals for reflecting T'ekf copes. 341

he fhewed me himfelf a box of finilhed metals, in which
I am fure there were a dozen, and a half of the fame focal
length.

To return : a little ufe in working will make the whole
of the procefs of grinding and polifhing very eafy and
certain ; for though I have endeavoured to be as particu-
lar as I can (I am almoft afraid too much fo) it is yet
fcarcely poflible to fupply a want of dexterity, arifing
from habit only, by the moll laboured and minute de-
fcription. And though the above account may appear
irkfome to the reader, as it lies cold before the eye, I am
very fure, whoever attempts to make the inftrument,
will not complain of it as tedioully particular.

I will, however, farther remark, that when the metal
begins to move ftiffly upon the polifher, and particularly
when the figure is almoft brought to the parabolic form,
it will be neceffary to fix the elbows againft the tides, in
order to give momentum and equability to the motion
of the hand by that of the whole body.

The fame polifher will ferve for Jeveral metals, if it
be fomewhat warmed when you begin to ufe it.

There is another eircumftance, and a material one
too, which muft not be omitted ; it is this. For the very
fame reafon that the pitch lhould not be too hard or loft,
the work will not proceed well in the heat of fummer,

or

34a Mr. mudge on the Conjlru&ion

or the cold of winter: in the latter, it may he poffible to

%

remedy the defedt by having the room warmed with a
Itove ; and in the fummer, the other inconvenience may
perhaps be avoided by ufing a harder kind of pitch ; but 1
much doubt in either cafe whether the work will go on
fo kindly : I have myfelf always wrought in fpring and
autumn.

The procefs of polifliing, and indeed grinding upon
the hones, will not go on fo well if it be not continued
uninterruptedly from beginning to end ; for if the work
of either kind be left but for a quarter of an hour, and
you then return to it again, it will be fome time before
the tool and metal can get into a kindly way of working;
and till they do, you are hurting what was done be ore.

I have all along fuppofed that the metal we 1 Lave been
working was about four inches diameter : if it be either
larger or fmaller, the lizes of the hones, bruifer, and po-
lifher, muft be proportionably different. I never find any
ill confequence arifing from the different expanfion from
heat and cold in any of the tools, though they be made of
different metals and fubftances, unlefs the inconvenience,
occafioned by the interruption before h inted at, be thought
to refult from thence ; for the alteration produced in the
furface of the fpeculum, both by grinding and polifliing,
is fo much quicker than any that can be fuppofed to arife

from

of Metals for reflecting I’eleJ. copes. 343'

from the former caufe, that it is never attended with any
practical confequence.

Magnifying very minute objects, and particularly read-
ing at a diftance, have been generally confidered as the
fureft tefts of the. goodnefs of a telefcope ; and indeed
when the page is placed at a great diftance, fo that the let-
ters fubtend but a very fmall angle at the eye, if then they
appear with great precifion and fharpnefs, it is mod: pro-
bable that the inftrument is a good one. But we are, ne-
verthelefs, fometimes apt to be deceived by this method ;
nor is it always poffible to determine upon the different
merits of two indruments of equal power, by this mode
of examination ; for when the letters are removed to the
utmoft extent of the powers of the two indruments, the
eye is apt to be prejudiced by the imagination. If twro or
three wrords can be here and there made out, all the reft
are gueffed at by the fenfe; infomuch that an obferver,
zealous for the honour of his inftrument, is very apt to
deceive himfelf in fpite of his intentions. The furer teft is
by figures, where you can procure no aid from this fort
of deception. In order to examine my refledting tele-
fcopes, I made upon a piece of copper and on a black
ground, fix lines .confiding of about twelve pieces of gold
figures, and each line of figures differing in magnitude,
from the fmalleft that could be diftindtly made to thofe

344 M\ mudge on the ConJlruBiion
of about two-tenths of an inch long; moreover, the
figures in the feveral lines were differently difpofed, and
the fum of each line alfo differed. It is evident that by this
method all guefs is precluded ; and that of twoinftruments,
of the fame powers, that which can make out the leaft
order of figures, which will be known by the fum, is the
beft telefcope. Such a plate I caufed to be fixed up for
experiments againft the top of a ft eeple, about three hun-
dred yards North of my houfe; and it will ferve to give
fome idea of the diftindtnefs with which very fmall figures
could be made out at that diftance, by faying, that in a
clear ftate of the air, and with the Sun behind me, with
a telefcope of eighteen inches focal length, which Count
bruhl did me the honour to accept and now has in his
poffeflion, I have feen the legs of a fmall fly, and the
fhadows of them, with great precifion and exadtnefs.

I cannot conclude without indulging myfelf in an ob-
fervation on the amazing fagacity of Sir Isaac newton
in every fubjedt upon which he thought fit to employ
his attention. It was he who firft propofed, and indeed
pradtifed, the polifhing with pitch; a fubftance which at
firft fight perhaps every one but himfelf would have
thought very improper, from its foftnefs, to produce that
corredtnefs of figure fo neceffary upon thefe occafions;
and yet I do believe, that it is the only fubftance in nature
..-a that '

of Metals for refleSling T’elef copes. 345

that is perfectly well calculated for the purpofe ; for at
the fame time that it is foft enough to fuffer the putty to
lodge very freely on its furface, and for that reafon to

4

give a moft tender and delicate polifh ; it is likewife
totally inelaftic, and therefore never, from that princi-
ple, fuffers any alteration in the figure you give it. If
the firft makers of the inftrument, therefore, had given
proper credit to, or had limply followed the hint Sir
Isaac gave, it would have faved them infinite trouble,
and they would have produced much better inftruments ;
but the pretended refinement, of drawing a tin&ure
from pitch with fpirits of wine, affords you only the re-
dinous, hard, and untraftable part of the pitch, divefted
of all that part of its original fubftance which is necelfary
to give it that accommodating pliability in which its
excellence confifts.

It is needlefs to fwell this account with a detail of the
procefs for polilhing the little fpeculum, as it mull be

N»4

conducted in the fame manner which has been already
defcribed in that of the large one; only obferving, that
as the little metal has an uninterrupted face, without a
hole, fo there is no occafion for one in the polifher; and
likewife that, as a fpherical figure is all that need here be
prattically attempted, fo the difficulty in finifhing is infi- -
nitely ffiort of that of the other.

Vol. LXVII. Y y

As

346 Mr. mudge on the Conjl ruction

As it is always neceffary to folder to the back of the
little fpeculum a piece of brafs, as a fixture for the fcrew
to adjuft its axis, I fhall juft hint a fafe and neat method
of doing it, which may be very ufeful to the optical or
mathematical inftrument-maker upon other occafions.
Having cleaned the parts to be foldered very well, cut out
a piece of tin-foil the exadt fize of them ; then dip a fea-
ther into a pretty ftrong folution of Jal ammoniac in wa-
ter, and rub it over the furfaces to be foldered; after
which place the tin-foil between them as faft as you can
(for the air will quickly corrode their furfaces fo as to
prevent the folder taking) and give the whole a gradual
and fufficient heat to melt the tin. If the joints to be
foldered have been made very flat, they will not be
thicker than a hair : though the furfaces be ever fo ex-
tenfive, the foldering may be conducted in the fame man-
ner, only that care muft be taken, by general preflure, to
keep them clofe together. In this manner, for inftance,
a filver graduated plate may be foldered on to the brafs
limb of a quadrant, fo as not to be difcemable by any
thing but the different colour of the metals. This me-
thod was communicated to me by the late Mr. jackson,
who during his life kept it a fecret, as he ufed it in the
conftrudtion of his quadrants, and is, I believe* not as yet
known to any workman.

In

of Metals for reflecting felej 'copes. 347

In the annexed plate are figured the lhape of the
leaden tool for rough-grinding; the hones; and the ap-
paratus to be applied to the mouth of the telefcope, to
afcertain the true figure of the fpeculum.

POSTSCRIPT.

It was fome time after I had written the above account
that I faw Mr. short’s method of polifhing object glaffes
for refracting telefcopes, which is publiflied in the Tran-
faCtions. By that paper I find that what I before
ftrongly fufpeCted is really the cafe, viz. that he knew
how well pitch was calculated for purpofes of this kind.
Only it may be remarked, that as glafs is much harder,
polifhes much flower, and confequently does not wear
away and alter its figure fo foon as the metal of which
the fpeculum is made ; and as at the fame time (on ac-
count of the very fmall apertures allowed to telefcopes
of this fort) nothing more than a fpherical figure is pro-
poled ; he is therefore obliged to ufe pitch in a hard,
friable, and ftubborn ftate : whereas, confidering the de-
licate fubftance of the metal fpeculum, and the figure
intended to be given to it, the foft pitch of the common
fort, by fuffering the putty to bed itfelf in its fubftance,

Y y 2 produces

348 Mr. mudge on the ConJlruBion

produces the moft beautiful polifh ; and by its pliability
is better calculated for that mutual accommodation be-
tween polifher and metal,, fo neceffary to the figure pro-
pofed.

EXPLANATION OF THE FIGURES.

Fig. i . The grinder for working off the rough face of
the metal; the black ftrokes reprefent deep grooves
made with a graver.

Fig. 2. The bed of hones, which is to complete the
fpherical figure of the fpeculum, and to render its
furface fit for the polifher.

Fig. 3. An apparatus for examining the parabolic figure
of the fpeculum.

a a The mouth of the telefcope, or edge of the great
tube.

bb„ A thin piece of wood fattened into, , and flufh with the
end of the tube ; to which- is permanently fixed the
annular piece of pafte-board ce, intended to cover,
and to prevent the action of the correfponding part
of the fpeculum.

r>. Ano-

mi * * f

'

i

\

•ib

of Metals for reflecting ’felej copes. 349

D Another piece of pafte-board, fixed by a pin to the
piece of wood bb, on which it turns as on a center; fo
that the great annular opening hh may be ihut up by
the ring ff, or the aperture gg by the imperforate
piece e in fuch manner that, in the firft inftance, the
reflexion may be from the center, and in the latter,
from the circumference, of the great Ipeculum.

OAF

V : *-»

t 35° 1

:>t nn b

j: l'j'J

:n::1 H

^ . i . .

XVII. Extract of a Regijler of the Barometer , thermo-

.

meter , and Ram , at Lyndon, /# Rutland , 1776. By

: , [mi . . ) r ' ' -

Thomas Barker, Efquire. Communicated by Sir J ohn
Pringle, itari. P. P. B.

;iiLrvO(/j

Read February 20, 1776.

Barometer.

Thermometer.

|Rain.

Higliell

Loweft

Mean.

In tl
High.

lie He
Low.

>ufe.

Mean

A

High.

ibroac

Low.

1.

Mean

Jan.

Feb.

Mar.

Apr.

May

June

July

Aug.

Sept.

oa.

Nov.

Dec.

1

Morn.

Aftern.

Morn,

Aftern.

Morn.

Aftern.

Morn.

Aftern.

Morn.

Aftern.

Morn.

Aftern.

Morn.

Aftern.

Morn.

Aftern.

Morn.

Aftern.

Morn.

Aftern.

Morn.

Aftern.

Morn.

Aftern.

29 ,65
29>5°
29>95
29,94
29»99
29,87
29,86
29,83

29.93
29,87
29,8S

29.94

28,88

28,24

28,50

29,00

28,73

29,°4

29.03

29,00

28,75

29,06

28,60

28,73

29,27

28,89

29,46

29,58

29,57

29,42

29,45

29.41
29,40
29,56

29.42

29.43

42f

43

44x

45

53x

55

54i

57 i
§2j
66
66

69x

65

68i

7°

ll

64

57x

58
52
52

48J

49

23
26

24

25

3*1

40

43

44

47

48

55x

57x

57

59§

57

59

52§

54i

48

48

37

37

34

34

32x

33

39

40

44x
46 ;

50 '

5iii

5*x

53

59

61

62
64
61
62f
57z
58f
52|
S3i
45x
46

42|

43

42

45

44

45 x
47x
62I
52
641
58
76
62

75

63i

80

63i

82§

60

69

62

54

54

49

52

10
16

1 1
27
27

37
3i
42

38
38
4§i
54
53
65

46

58x

37

52j

36

48

261

32x
2 1 2
261

26

29

35

41!

38

48i

42i

55

47

57
54
64i

58
69!
54
66

49x

61

45 x

54

3§i

44

37

40} (I

2,5JI
3> 1 95
I?5l8
0,887
1,627

2,485

1,850

5,200

2,452

2,061

2,823

1,233

27,842

The

Mr. barker’s Regijler of the Weather. 351

The year began wet, but there foon fell a greater quan-
tity of fnow than for feveral years paft : we had perhaps
the fliarpeft froft fince 1740, and it was more intenfe
at the latter part of it than at the beginning. The froft
went away finely the beginning of February, and without
much rain till the fnow was almoft gone ; but a good deal
of the middle of February was ftormy and wet, and it was
chiefly wet till about ten days in March, yet not cold.
Then the feafon grew dry; the feed-time was fine, plea-
fant, growing warmer, and in the middle of April hot.
There was great plenty of blofloms of all forts, and the
grafs came on well; but the wheat, which had been left
thin by the great froft and fnow, was rather hurried on
too fail. It grew colder at the end of April, and was cool
and dry moft part of May, with chiefly Northerly, winds.
During this time the wheat mended much, but rain
began to be wanted, of which there came fome in June,
and brought on both corn and grafs. The latter end of
that month and July were only fhowery and hotter, fio
that the hay was got in well; and toward the end of July
and beginning of Auguft, the ground began to burn
pretty much, when after fome very hot days there came
a great deal of wet.

The courfe of the feafons this year was I believe the
fame in all places. Dry fpring and beginning of fummer,
fhovrery June, drier July, very hot beginning of Auguft,
5 and

3^ 2 barker’s Regi/ter of the Weather.

and wet after; but in different proportions in various
places. In fome, as Leicefterfhire and Northamptonfhire,
the drought fo much prevailed that the ground was
greatly burnt, and hay very fcarce ; on the other hand
here and in Hun tingdonfhire, there were fo many refrefh-
ing fhowers that we never were in want of grafs.

The beginning of harveft was wet, and the reft
fhowery. I believe a little of the wheat might grow, but
in general the grain was pretty well got in. It was a re-
markably plentiful year for almoft all kinds of fruit;
the crop of grain was pretty good, efpecially the barley;
and there were great quantities of latter grafs and tur-
nips. In the middle of September the weather grew
fairer; it was a fine latter end of the year and wheat
feed-time, without too much rain intermixed. As the
winter came on, it was chiefly calm, and there was much
cloudy or mifty weather, fcarce any frofty mornings till
near the end of November; a fhort froft then and mild
again-; but towards the latter half of December it began
to be more inclined to froft, and the year ended with a
iharp one, and pretty deep fnow.

[ 353 3

XVIII. Extra?? of a Meteorological Journal for the Tear
1776, kept at Briftol, by Samuel Farr, M. D.

Read February 27, 177

Barometer.

Months.

Higheft.

Lowell

Mean.

Viciffitude,

January

29.93

29,04

29.53

47“ i

+

F ebruary

29.74

28,66

29,21

102-2

+

March

30,28

28,80

29.53

1 10-2
+

April

30,28

29,26

29.85

68-2

May

3°>3°

29,10

29,88

40 ~ i

June

30,20

29.38

29,88

39”1!

July

30,16

29,30

29,76

4o-iJ

Augufl:

3°, 08

29,3°

29,68

3°“ i

September

30,20

20,17

29,72

98-4

+

October

30, 1 8

29,60

29,87

54^1

4-

November

28,90

29.74

65“ i
+

December

30,28

29,26

29,76

32- i

4- riling.
— falling.

Z z

Vol. LXVII.

An

354

Dr. farr’s Meteorological Journal.

An abridged Table of the winds, See. for Bristol, for

the Year 1775.

l

N

E

W

S

NW

SE

NE

SW

Rain.

F rofty
Days.

Fail-

Days.

Thunder, &c,

fan.

O

1

0

0

1

2

3

23i

3

3,993

25

6

Feb.

O

0

0

n

I

3!

4

20|

5,538

1

51

5. S.W.

Mar.

O

H

0

i§

3

7l

l6

1)643

oi

z2

*3l

Apr.

**

1

1

2

2

4

2

I01

81

°,438

I

18

May

2i

2

1

2

oi

Z2

4

1

7

1,149

O

13%

June

1

2

1

2

0

3

2

5

51

13i

2)554

O

i3l

*3- S.

July

0 !

0

1

2

3

3

5

1

1 81

2,332

O

i3

5. S.E. 19. S.E.

t

/* r

f 6. N.W. 16. S.W.

Aug.

1

J.

2

1

2

1

5

6|

3

14

4,747

I

ul

1 30. S.W.

Sept.

0

O

0

1

2

4

3

10

I2l

3,270

5

15I

•4, N.W. 8. N.W.

oa

0

if

0

*1

3i

4

r3

71

1,686

4

6

Nov.

1

0

1

2

0

2

13

i}

12

2,283

5

*°1

30. S.E.

Dec.

3l

1

2

1

2

1

2

3i

rof

2

10

1,422

9

1 1

1. S.E.

9l

8|

3

17

34

sal

91!

J43

3I?°55

531

>3721

WEATHER FOR THE YEAR 17.76..

January. It rained a little at firft; but foon changed
to fnow, which was fucceeded by a hard froft that
lafted till the next month.

February. After, the thaw it became very wet and

tempeftuous.

March. Often frofty and fair, with now and then a
eonfklerable lborm, as on the 8th and 9th.

3

April

Dr. farr’s Meteorological Journal. 355

April. Stormy, although but little rain fell for about
half this month; after the 20th it was quite fair.

May. After this it was ftormy, with fome rain on the
4th, 5th, 6th, 8th, 1 1 th, 1 9th, and 20th, but not much;
the reft of this month was fair.

June. Very wet for 7 or 8 days, and on the 10th,
I ith, and 1 2th, and alfo from the 14th to 17th; it was
then fair to the 23d; rained then and on the 24th and
27 th.

July. Very wet and cloudy, with thunder, See. on the
5th and 19th; very few days fair till the 2 2d; after
which it was in general fair this month.

Auguft. Very fine for a few days; but afterwards it
became wet and ftormy till the 20th; after which it was
in general fair.

September. Stormy for fome days; fair on the 8th and
9th; frofty on the 10th, and then fair to the 15th; wet
to the 1 8th; and then fair to the end.

October. Dry though cloudy, with a little rain for
7 or 8 days ; after which it rained part of every day for
as many more, and then became variable with fome
frofty nights.

November. Dry with fome froft and fog, but with
little rain on the 9th and 1 itli, and for a fortnight after;

Z z 2

it

356 Dr. farr’s Meteorological Journal.

it next became variable, but generally fair; it rained

very hard on the 23d and on the 28th.

December. Wet for a few days and then cloudy, but
without rain for the firft week ; it was then dry for a few
days; it froze on the 16th, and fnow fell on the 18th;
the 19th was fair; it rained afterwards to the 23d, and
fnowed on the 24th; after which a froft fat in, and con-
tinued till the end.

V

METEOROLOGICAL JOURNAL

KEPT AT THE HOUSE OF

THE ROYAL SOCIETY,

BY ORDER OF THE

PRESIDENT AND COUNCIL:

[ 358 ]

METEOROLOGICAL JOURNAL

for January 1776.

Time.

Therm.

without

Therm.

withih.

Barom.

Rain.

Winds.

Weather.

H.

M.

Inches.

Inch.

Points.

Str.

Jan. 1

8

0

38, 5

39)°

29)94

SE

1

j Cloudy.

2

0

41,0

4°,°

?9t82

S

1

Fine.

2

8

0

41,0.

4i>5

29,5b

CW5

NNW

. I

(Rain.

2

0

4^5

4r,5

29,69

NNW

1

Cloudy.

3

8

0

36,0

39)5

3°>°9

0,065

NE

1

Cloudy.

2

0

37>°

40,5

3°, i4

E

1

Fine.

4.

8

0

39>°

38,5

29>77

0,031

SSE

1

Rain.

2

0

44>°

40,0

29,5°

S

2

Rain.

5

8

0

44,5

43?$

29,4°

0,444

-s w

ir

FairC, -

c:

2

0

48,5

45)5 '

29,48

wsw-

r

Cloudy.

6

8

0

36>°

4 3)5

29,63

wsw

1

Fine.

2

io

4*, 5

44,0

29,57

E by N

1

Fair.

7

8

3°

33>°

39)5

29,245

°,i53

ENE

2

Rain.

2

0

31,0

38,0

29>35

ENE

2

Snow.

8

8

0

3°>°

34?°

29,46

0,229

NE

1

Much fnow laft night.

2

0

32,°

35>5

29,49

(R ;

1

F air.

9

8

0

3°>°

34)5

29,63

0,079

N

1

Cloudy.

2

0

28,5

33>5

29,67

ENE

1

Cloudy.

10

8

0

3°> 5

33)5

29,73

NNE

1

Cloudy.

2

0

33,°

34)0

29,73

NW

1

Cloudy.

1 1

8

0

3°,°

3L5

29,57

E

1

Cloudy.

T

VI i

2

0

35P

33)5

29?4I

> SE

' n ,

Cloudy.

12

8

0

3°>°

33)°

29,21

0,091

E

" 2

Much fnow and wind laft nt.

2

0

32>°

34>°

29,21

ENE

2

Snow.

*3

8

0

3°,°

32)5

29,32

NE

2

Much fnow and wind laft nt.

2

0

29,0

32)0

29,36

NE

2

Cloudy.

14

8

0

25.0

30,0

29,45

ENE

2

Snow.

2

0

26,0

29,0

29,49

NE

2

Snow.

15

8

0

26,0

.29,0

29,70

N

1

Cloudy.

2

.0

29,0

3°) 5

29,7°

ME

1

Snow.

16

8

0

2 5o

29P

29,71

NNE

’ 1 1

Snow.

2

0

3°>5

3°) 5

29,70

NE

1 !

Snow.

METE-

C 359 1

METEOROLOGICAL JOURNAL,
for January 1776.

Time

. Therm

. Therm

. Barom

Rain

. Winds.

withou

t within

*ttt . i

w eatner.

H. M

Inches.

Inch.

Points.

Str

•

Jan. 1 7

8

c

28,0

29,5

29>74

NNE

1

Cloudy.

2

c

3°>5

3°>5

29>74

NNE

1

Cloudy.

18

8

c

33,°

32,0

29,87

;

ENE

1

Cloudy,

2

0

3°>°

3b5

29,90

ENE

1

Cloudy,

l9

8

0

27,0

30,5

29,90

NE

1

Snow.

2

0

27,0

3i5o

29,85

NE

1

Fair,

20

8

0

23>5

29,0

29,70

N

1

Fair.

2

0

24,0

29,0

29,70

»

N

1

Fine.

21

8

0

22,0

27,0

29,62

r SSW

1

Cloudy.

2

0

28,5

27,5

29>55

j

ssw

1

Fine.

22

8

0

3o,S

28,5

29,4i

E

1

Fair..

2

0

33,5

3°, 5

29?39

NE

1

Fine,

23

8

0

25,0

28,5

29>53

NE

1

Fair.

2

0

33,°

30,0

29,58

NNE

1

Snow.

24

8

0

3°,°

3°>°

29,81

w

ENE

0

Cloudy, ,,

2

0

35>°

3L5

29,84

NEbyE

1

Fair.

25

8

0

29,0

3L5

29,87

NE

1

Cloudy.

2

0

33,o

32,5

29,85

SE

{

1

Fair.

26

8

0

26,0

30,5

29,82

E

;

1

!

Cloudy,

2

0

26,0

3°, 5

29,82

SSE

2

Fine.

27

8

0

J9>5

26,0

29,80

ENE

2

Snow.

2

0

20,5

25?5

29>79

ENE

2

Snow.

28

8

0

18,5

22,5

29>94

E

2

Snow.

2

0

22,0

23>°

30,00

E

2

Fine.

25

8

0

I4?5

20,0

29,91

SE

I

Fine.

2

0

24,0

2I?5

29,88

SE byE

I

Fair.

3°

8

0

I5>o

I9?5

29>97

NE

I

F air.

2

0

21,0

20,5 .

30,02

E

I

Fine.

3i

8

0

J3>5

*9*5 ;

30,09

NE

I

Fair.

a.. - 1

2

0

23>5

2°?5 :

30,07

E

1 ■-

Fine. ,

METE—

[ 3^0 ]'

METEOROLOGICAL JOURNAL

for February 1776.

Time.

Therm.

without

Therm.

within

Barom.

Rain.

Winds.

Weather.

H.M.

Inches.

Inch.

Points.

Str.

Feb.

J

8

0

J4,5

19,0

29.97

NE

1

fair.

■

2

0

3bS

3J,5

29,86

E

1

Cloudy.

2

8

G

37>°

28,5

29,78

NE

0

Cloudy.

2

O

40,5

31,0

29.57

SE by E

1

t air.

3

8

O

37>°

34.5

29.34

0,093

SSE

1

Fog.

2

O

44,o

36,°

29.51

S by W

1

Fine.

4

8

20

44,°

38,5

29,22

sw

2

Cloudy.

:

2

O

48,0

41,0

29,22

sw

1

Cloudy.

5

8

O

40, s

42,0

29,16

0,153

wsw

2

Fine.

j

2

0

48,0

44>°

29,11

SWbyW

2

fine.

6

8

O

37,°

42.5

28,98

0,221

WSW

2

Fine.

2

O

45>°

44,0

29,02

WSW

2

fine.

7

8

O

43,°

42,0

28,91

SWbyW

2

Fair.

2

O

47,5

43,5

29.07

SW

2

Fair.

I

:

8

8

O

40,0

42,5

29,66

0,190

sw

1

Rain.

2

O

49>S

44,5

29,62

SSW

2

Cloudy.

9

8

G

41,0

44,5

29,78

0,19°

ssw

1

fine.

'

2

0

45,5

45,5

29,58

s

2

Cloudy.

10

8

O

42,0

46,0

28,99

0,524

SWbyW

2

Rain.

.

2

O

48,0

47,°

28,97

sw

2

Fair.

1 1

8

O

42,5

45,o

28584

0,275

sw

2

Fair.

2

O

45,5

46,0

28,84

ssw

2

Rain.

12

8

O

■ 34,o

42,0

29,10

ssw

1

Fair.

2

O

46,0

44,o

29,24

wsw

1

fine.

13

8

O

36,5

42,5

29,68

3

sw

1

Fine..

2

0

47,o

44,o

29,71

0,163

wsw

1

Fine.

H

8

O

47,°

45,o

29551

sw

2

Fair.

2

O

51,0

48,0

29>53

S by W

1

Fine.

15

8

G

i 38,0

44,5

29,96

ssw

1

fine.

2

O

48,0

46,5

29,91

ssw

2

Fair.

16

8

O

42,0

46,0

29.75

0,085

sw

1

Fine.

1

2

C

1 49,5

47,5

29,78

sw

1

Fair.

METE'

[ 30x ]

METEOROLOGICAL JOURNAL

for February 177 6.

Time.

Therm.

without

Therm.

within.

Bar 01m

Rain.

]

Winds.

Weather.

H.M.

Inches.

Inch.

Points.

Str.

Feb. 17

8

0

36>o

43>°

29,68

0,021

ENE

1

Rainy.

2

0

43,5

42)5

29>S3

E

1

Fair*

18

7

0

35? 5

42,0

29)43

0,270

ss w

1

Fair.

2

0

39?5

42,0

29,25

NE

1

Cloudy.

*9

7

0

38,5

42,0

29)34

0,140

sw

1

Rainy.

2

0

4 1,5

4i)5

29,62

NW

1

Fair.

20

7

0

4i>5

40,5

29?775

0,089

s

1

Rainy.

2

0

5°>°

44)0

29,80

W by S

1

Fine.

21

7

0

49>5

45?5

29.5s

WSW

2

Cloudy.

2

0

54?5

49)0

29.5°

wsw

2

Fair.

22

7

0

36>5

44)0

29,62

0,412

SW

1

Fine.

2

0

45?o

45)0

29)4*

SSE

3

Rain,

23

7

0

35?o

40,5

29.3s

0,148

WSW

1

Fine*

2

0

45 ?5

44,o

29,50

wsw

2

Fair.

24

7

c

39)0

41,0

29,25

0,079

SSE

1

Rain.

2

0

46,0

48,0

29,1°

WSW

1

Rain.

25

7

0

37)0

4°)°

29,5°

0,102

N

1

Cloudy.

2

0

43?o

41,5

29,55

SSW

1

Fair.

26

7

0

46,0

43,5

29,18

SSW

1

Cloudy.

2

0

53)0

4^,5

29, 13

Shy W

2

Cloudy. _

27

7

0

39)5

43,0

29.155

0,149

SSW

2

Cloudy.

2

0

48,0

45>°

29,26

WSW

2

Fair.

28

7

0

43 ?o

43,5

29,11

0,140

SSW

2

Fair.

2

0

47?o

45,5

29,17

SW

2

Fair.

29

7

0

38?0

43?°

29,35

0,066

SSW

1

Fine,

2

0

48,0

45,°

29,35

wsw

1

Fine.

Vol. LXVII. A a a mete

t 362 ]

METEOROLOGICAL JOURNAL

for March 1776.

Time.

Therm.

without

Therm.

within.

Barom. 1

Kain.

Winds.

»

Weather.

H. M.

Inches.

Inch.

Points.

Str.

Mar. 1

7

0

32>°

42,0

29>S2

0,080

WSW

1

Fair.

2

c

45.5

43? 5

29,60

NE

1

Fine.

2

7

0

3 5 5°

41,0

29>75

N

1

Fair.

2

0

43>°

42,5

29.77

NNE

1

Fair.

3

7

0

3°?5

37>°

29,78

SSW

1

Fine.

2

0

44P

40,5

29,67

SSW

1

Fair.

4

7

0

36,0

38,o

29?49

0,159

N

2

Cloudy.

2

0

44? 5

4X?5

29. 73

NNW

2

Fair.

5

7

0

445o

42,5

29,81

0,058

sw

2

Fair.

2

0

46.0

44,5

29.85

SvV

2

Rain.

6

7

0

4i?5

44? 0

29.77

°,3l4

SE

I

Rain.

I

2

b

43.5

44? 5

29.58

E

I

Rain.

7

7

0

39.°

43>°

29,70

°?5I4

E

I

Cloudy.

r

2

0

42,0

43?5

29.59

SSE

I

Rain.

8

7

0

40,0

45?o

29.25

0,229

SSW

I

Fine.

2

0

49?°

47 ?o

29,18

sw

2

Fair,

9

7

0

43.o

45?5

28,98

0,065

s

2

Fair.

2

0

So,o

49,°

28,99

SSW

2

Fair.

10

7

0

40,5

44? 5

29>37

0,079

WSW

I

Fair.

2

b

48,0

4b, 5

29^0

W

I

Fine.

1 1

7

0

35?°

41,0

29,72

NNW

I

Fine.

2

0

46,0

44,o

29,86

NW

I

Fine.

12

7

0

4

42,0

29?95

SSW

I

Cloudy,

2

0

49,°

45?°

29?99

SSW

I

Rain.

*3

7

c

46,0

46>5

3°?oo

0,014

SSW

I

Fair.

2

0

5 3.5

49>°

29,86

SSW

I

Fair.

14

7

0

4i?5

45?5

29^83

N

I

Fair.

2

0

49?°

47?°

29?94

N

I

Fine.

15

7

0

40,0

45.5

3°.°3

w

I

Fine.

2

3°

55.o

48,5

3°.°5

WSW

I

Cloudy.

16

7

0

43.°

48,0

3°?i9

N

I

Fine.

2

0

49>5

49,0

30,2 1

N

I

Fine.

METE

[ 3$3 1

METEOROLOGICAL JOURNAL

for March 1776.

Time.lThrem.

Therm.

Baro m.

Rain.

Winds.

without

within.

Weather.

H.M.

Inches,

Inch.

Points.

Str

Mar. 1 7

7

0

38,0

46,0

3°. 3°

S

1

Fine.

2

0

53- s

48,5

30,3°

wsw

1

Fine.

18

7

0

34>°

45>° .

30,18

sw

1

Fine.

2

0

53>5

48,0

3°, '3

sw

1

Fine.

*9

7

0

47?°

48,0

30,06

sw

1

Cloudy.

2

0

5°>°

46,0

3°>°9

sw

1

Cloudy.

20

7

0

48,0

49,0

3°;I5

w

1

Cloudy.

2

0

55>°

52,0

30, 2 3

ssw

1

Cloudy.

21

7

0

43>S

49>5

30,23

E

1

Fine.

2

0

59,5

53>5

30,20

sw

1

Fair.

22

7

0

49, 0

5 25o

29,96

sw

i

Fine.

2

0

63, 5

6o,o

29,95

ssw

1

Fine.

23

7

0

46,5

49.5

29,94

NE

1

Fog,

Fine^

2

0

66,0

57.°

29,91

SW by S

1

24

7

0

5- 2,5

56,0

29,94

NNE

1

Fair.

2

0

67,0

59.°

29,99

SE

1

Fine.

25

7

0

4S>°

52,0

30,30

ENE

1

Fair. ,

2

0

49,0

49>°

30,33

ENE

2

Fine.

26

7

0

37,o

42,0

30,38

NE

1

Fair.

2

0

49,5

46,0

30,33

NE

1

Fine.

27

7

0

33>5

42,0

3°, 1 3

NNE

1

Fine.

2

0

5i,S

45.°

30,04

NNE

1

Fine.

28

7

c

4i,5

44>5 .

30,01

0,029

NNE

,1

Cloudy..

2

0

46,0

46,0

30,03

NE

1

Cloudy. j

29

7

0

40,0

4-4,5

30,11

N

1

Fair..

Fair.

2

0

47,5

46,0

30,20

NNE

1

3°

7

0

35,o

44,0

3°, 3 7

S

1

Fine.

2

0

56,5

47.5

30,38

N by W

1

Fine.

31

7

3°

44,5

47 ,5

30,43

wsw

1

Fair.

2

0

60,5

5E5

30,42

wsw

1

F i ne.

A a a 2

M ETE-

[ J«4 ]

[

METEOROLOGICAL JOURNAL

for April 177 6.

rime.

Therm

without

Therm.

within.

Barom.

Rain.

Winds.

Weather.

H. M.

Inches.

Inch.

Points.

Str.

■ Apr. 1

7

0

44.0

5°>5

3°,44

SSVV

1

Fine. -

2

0

60,0

54>°

3°,43

N

1

Fine.

2

7

0

48,0

53'°

3°, 3 7

NNE

1

Cloudy.

2

0

59?°

54.5

3°, 34

N h

1

Fine.

3

7

0

42?5

3°, 34

SW

1

Fine.

2

0

62.0

56) 5

30,28

w

1

Fine.

4

7

0

45>°

5

30,22

N

1

Fine.

2

0

54>°

53’5

30,22

N

1

Fine.

5

7

0

4>)°

43)5

3°, 22

N*

1

Fair.

2

0

49,0

49)5

3°>l7

N

1

Fair.

5

7

0

4°,5

46,5

3<V45

N

1

Cloudy.

.2

0

47,0

48,0

ssw

1

Cloudy.

7

7

0

45 5

46,0

3°>°3

WNW

1

Fair.

2

0

50.5

43)5

29>94

NW

1

Cloudy.

§■

7

0

45>°

48,0

29>75

WNW

1

Fair.

2

0

5L5

5°)°

29?57

NW

2

Fine.

9

7

0

39>°

43>5

29,71

0,065

NW'

2

Fair.

2

0

39>°

45.°

29,86

NWbyN

2

Cloudy*,

10

7

0

34)5

41,0

3<V3

0,052

N

1

Fine.

2

0

4^>5

44,0

3°, 16

NNE

2

Fine.

1 i

7

0

44s5

44)0

30,21

NNE

1

Cloudy*

2

0

54)0

48,0

30,21

, N

1

Fair.

12

7

0

44,0

46,0

3°, 17

NW

1

Fair.

2

0

53)5

49>5'

3°)°7

WNW

1

Fair.

l3

7

0

45>°

48)5

29,85

\

SW

1

Fair. -

2

°j

56,5

52)°

2%So

NW

1

Fair.

14

7

o|

43,5

5i)°

29,81

. SSW

1

Cloudy.

2

°i

57?°

54,5

29,76

wsw

1

Fair.

25

7

0

4&?5

52,0

29,68

0,GlO

SW

1

Cloudy

2

°!

56?0

53’5

29,68

SW

1

Fair. '

16 j

7

°i

4 8,5

57,5

29>5!

E

1

Fair.

i

2

Oj

62,0

55)°

29,46 [

S •

2

Rain.

METE

[ 36 5 ]

METEOROLOGICAL JOURNAL

for April 1776.

Time.

Therm.

without

Therm.

within.

Barom.

Rain.

Winds.

Weather.

H.M.

Inches.

Inch.

Points.

Str.

Apr. 17

7

0

52,0

5S,o

29,58

0,132

S

2

Rain,

2

0

65, 5

60,0

29,64

S

1

Fine.

l8

7

0

56,5

58,5

29,64

0,061

S

0

Cloudy.

SW

1

Fair. .

*9

7

0

44,5

51,0

29,97

SW

1

Fair.

2

0

60,5

59>o

30,00

SSW

1

Fair.

20

7

0

48,5

53,o

30,04

SW

1

Fair. ,

2

0

59,°

57,5

30,07

w

1

Fair.

21

7

0

47, 0

50,5

30,27

N

1

Fine.

2

0

60,0

57,5

30,30

N by W

1

Fine.

22

7

0

48,5

54,o

30,30

S

1

Fair.

2

0

63)°

58,5

30,25

N

1

Fair.

23

7

0

48,0

53,5

30,16

NE

1

Fair.

2

0

62,5

59,5

30,09

NE

1

Fine.

24

7

0

48,0

55,o

29,95

NE

1

Fine.

2

0

64,5

58,5

29,88

ENE

1

Fine. .

25

7

0

50,0

57)°

29,86

SE

1

Fair.

2

0

68,5

62,0

29,88

NW

1

Fine. .

26

7

0

43,0

49,5

3°> 1 6

N

1

Fine.

2

0

58,0

55,o

3°j19

N

1

Fair.

27

7

0

47>5

5LO

3°>3°

NW

1

Fine, ..

2

c

59>°

55,5

3°>3°

NE

1

Fine, .

28

7

0

46,5

5G5

3°>3°

SW

1

Fine.

2

0

63>5

57,5

30,20

wsw

1

Fine.

29

7

0

45)5

52,0

3°, 10

N .

1 ,

Fair. .

r 2

0

56) 5

55,5

30, 10

NNW

1

Fair. ,

3°

7

0

4>>o

46,0

30,18

NNW

1

Fair.

2

3°

50,5 .

51,0

3°sI9

NW

1

Cloudy. .

METE*

[ 3^6 ]

METEOROLOGICAL JOURNAL

for May 1776.

Time.

Therm.

without

Therm.

within.

Barom.

Rain,

Winds

■

Weather.

H.M.

Inches.

Inch.

Points.

Str.

May 1

7

0

40,0

47>°

30,21

N

1

Cloudy.

2

0

5°, 5

49>5

30,21

NNE

1

Cloudy.

2

7

0

49.°

50,0

30,18

W

1

Cloudy.

3

0

64,5

55,5

$o,ii

sw

1

Fine.

3

7

0

52,0

55>o

29,70

sw

2

Cloudy.

2

0

60,5

57,5

29,64

W byS

2

Fine.

4

7

0

46,0

5o>°

29,77

0,094

NNW

2

Fine.

2

0

61,0

55,5

29,65

wsw

I

Fair.

5

7

0

44> 5

52,5

29,21

0,105

sw

1

Cloudy.

2

0

50,5

54,0

29,14

wsw

2

Fine.

6

7

0

42, °

48,5

29,48

0,242

NWbyN

2

Fine.

2

0

5*>5

51,5

29,50

NW

2

Fair.

7

7

0

42,5

48,0

29,76

W by N

I

Fair.

2

c

5°>5

50,5

29,70

N by W

I

Fair.

8

7

0

4L5

48,0

29,66

0,-167

N

I

Fair.

2

0

52,0

51,0

,29,67

NNE ,

2

Fair, Thunder at i.

9

7

0

45>°

49>°

29,71

0,077

NE .

I

Cloudy.

2

0

5 2P

5L5

29,78

NN E '

I

Cloudy.

10

7

0

46,0

50,0

30,00

0,QI0

SE •

I

Fine.

2

0

58,0

53>°

30,05 _

ENE

I

Fine.

1 1

7

c

46, 5

52,0

30,18

,0,071

N .

I

Fine.

2

0

59>°

55,5

30,2 2 .

NNE '

I

Fair.

12

7

0

53,°

54>5

3°x28

SSW

I

Fair.

2

0

62,0

58,0

30,79

SW

I

Cloudy.

*3

7

. o:

49,°

55,5

3°, 45

0,067

NE

I

Fine.

2

0

62,5

57,5

30,46

N by W

I

Fine.

7

0

55> 0

57,5

3°, 43

wsw

I

Fa.i r.

2

0

63>S

6j,5

N by W

I

Fine.

15

7

0

48,0

54,5

3°, 18 '

C

N

, I

Rain.

2

0

55, 0

57,o

30,16

N

2

Fair.

16

7

c

46,0

58,0

3°,r3

0,010

N

I

F air.

2

0

54,o

,54,5

3°, 02

N

I

(Fine.

M E T E-

[ 367 ]

METEOROLOGICAL JOURNAL

for May 1776.

1 ime.

Therm.

without

Therm.

within.

Barom.

Rain.

Winds.

Weather.

H

M

Inches.

Inch.

Points.

Str.

May 17

7

0

47 >°

52,0

3°>°3

0,051

N

1

Fair.

2

0

55>°

55,°

30,06

N by E

1

Fair.

18

7

0

46,0

ShS

30,06

NEbyN

1

Rain.

2

c

56,°

53>°

29,98

NE

2

Fair.

l9

7

0

52,°

52,5

29,91

0,110

E by N

2

Fair.

2

0

5°>°

53’5

29>93

NE

2

Rain.

20

7

0

49-5

53,5

30,1°

0,590

NNE

I

Rain.

2

0

64,°

57?°

39? 1 5

NE

I

Fair.

21

7

0

47,5

53’5

3°>255

NE

I

Cloud)/.

2

15

58>5

56,0

30,22

NNE

I

Fine.

22

7

0

47,°

53?°

30,15

N

1

Fair.

2

0

61,5

55j5

3°>°7

NE

I

Fine.

23

7

0

47,o

52,5

30,08

N

I

Fair.

2

c

54,o

53>5

30,07

N

I

Fair.

24

7

0

46,5

48,0

30,15

NE

2

Fine.

2

0

58,5

535°

30,20

NNW

2

Fine.

25

7

0

44,o

49>5

30,22

S

I

Fine.

2

0

59,o

53’5

30,16

NNW

I

Fine.

26

7

c

53>°

54 0

30,12

W

I

Fine.

2

0

65,0

5^,5

3°, 1 1

WNW

I

Fair.

27

7

0

54,o

57>5

30,09

-

NW

I

Cloudy,

2

0

64,5

61,0

30,06

SSE

I

Fair.

28

7

0

57,5

59,°

30,04

SE

I

Fine.

2

0

72,0

64,0

30,02

sw

1

Fine.

29

7

0

61,5

61,5

29,98

SSE

I

Fine.

2

0

77,5

67,0

29,97

S

I

Fine.

3°

7

0

62,0

66,o

29,87

S

I

Fair.

2

0

66,0

68,0

29,85

S by E

2

Fair.

31

7

0

60,0

65,0

29,86

s

I

Fair.

2

0

70,5

68,5

29,87

ssw

I

air.

MET E

[ 368 I

METEOROLOGICAL JOURNAL

for June 1776.

lime.

Therm.

without

[Therm.

within.

Barom.

iRain.

Winds.

f

Weather.

H. M.

Inches.

Inch.

Points.

Str.

June 1

7

0

58,0

64,5

29,81

0,010

NE

I

Cloudy,

2

0

60,0

65, 5

29,75

E

I

Rainv.

2

7

0

57>5

64,0

29,90

0,215

W

I

Fair.

2

0

73>°

67,0

29,92

E

I

Fair.

3

7

0

60,0

65.5

29,92

0,070

NNE

I

Cloudy.

2

0

78,5

70,5

29,92

E

I

Fine.

4

7

0

66,o

7°, 5

29,83

NNE

I

Fine.

2

0

74>°

72,5

29,87

SWbyW

I

^ ine.

5

7

0

61,0

65,0

29,8a

SW

I

Fine.

2

0

63>5

67,5

29,75

SW

I

Cloudy.

6

7

c

56,0

63.0

29,5!

0,189

W

I

Cloudy.

2

0

59>S

65)0

29,48

NW

I

Fair.

' 7

7

0

52,5

6 i,o

29,59

0,138

SW

I

Fine.

2

0

58,0

61,5

29,63

S by W

I

Rain.

8

7

0

55>°

58>°

29,66

0,249

SW

I

Fine.

2

0

61,5

60,5

29,68

SW

I

Fine.

9

7

0

5S>°

58,5

29,85

0,041

S

1

Rain.

2

0

63.°

61,5

29,87

S

2

Rain.

10

7

0

59>°

61,0

30,00

0,078

SSW

I

Fair,

2

0

66,5

63)0

30,00

1 SSW

I

Fair.

1 1

7

0

58,0

61,5

29,67

o,3°7

SE

I

Rain.

2

0

67,0

65,0

29,64

SSW

I

F air.

12

7

0

57.°

6a, 0

29,56

0,016

E

I

Rain.

2

0

65.5

64,0

29,57.

SSE

I

Fair.

*3

7

0

57>°

59.0

29,61

w

I

Fine.

2

0

67,5

63,5

29,64

w

I

Fine.

H

7

0

59>5

63,5

29,81

SW

I

Fine.

2

0

71,0

65,5

29,87

SW

I

Fair.

15

7

0

62,0

65.0

29,80

S

I

Fine.

2

0

67,0

67.5

29,89

SW

I

Cloudy.

16

7

0

59>°

65,5

29,73

S

I

Rain.

2

0

62,0

66,0

29,72

SSW

I

Cloudy.

METE-

[ 3«9 ]

METEOROLOGICAL JOURNAL

for June 1776.

Time.

Therm.

without

Therm.

within.

Barom.

Rain.

Winds,

Weather.

H.M.

inches.

Inch.

Points.

Str.

June 17

7

0

57,o

64,0

29,82

0,230

W

1

Fine.

2

0

69, 5

66,5

29,99

w

1

Fine.

l8

7

0

S8»°

64,5

30,14

sw

1

Fine.

2

0

67,5

7o?o

30,2!

N.W

1

Cloudy.

*9

7

0

6i,5

66,0

3°>32

N

1

Fine.

2

0

72,0

69,5

30,34

E

1

Fine.

20

7

0

60,0

63,5

30,27

SSW

1

Fine.

2

0

74,o

68,s

30,19

s

1

Fine.

21

7

0

64,5

65,5

29,94

s

1

Cloudy.

2

0

72, S

69,5

29,88

sw

1

Cloudy,

22

7

0

60,5

66,5

29,89

wsw

1

Fine.

2

0

68,5

67,5

29,90

W by S

2

Fair.

23

7

0

58,0

64,5

29,95

W by S

2

Fair.

2

0

69>5

66,5

29,93

SW

2

Fair.

24

7

0

58,0

54,5

29,76

w

I

Fine.

2

0

67,0

65,5

29,87

sw

2

F air.

25

7

0

S5,o

62,5

3°,°3

w

I

Fine.

2

0

66}o

64,0

30,02

.

w

I

Fine.

26

7

0

55,o

6o,o

29,94

w

I

Fine,

2

0

68,5

65,0

29,86

NE

I

Cloudy.

27

7

0

56,0

62,0

29,77

NE

I

Cloudy.

2

0

56,5

63,5

29,79

SE

2

Rainy.

28

7

0

53,5

58,5

29,87

0,465

NNE

I

Cloudy.

2

0

63,°

67,0

29,94

NE

I

F air.

29

7

0

53,5

59,°

30,03

05020

N

0

Cloudy.

2

0

63,0

63,°

30, °5

NW

I

Fair.

3°

7

0

57,0

62,0

30, 01

N

I

Fair.

2

0

71,0

65,5

29,99

SWbyW

, I

Fair.

Vol. LXVII

B b b

METE

[ 370 ]

i —

METEOROLOGICAI

.JOURNAL ^

for July 17

76.

Time.

Therm

Therm.

Barom

Rain.

Winds.

without

within.

Weather.

H.M.

inches

Inch.

Points.

Str.

ju y 1

7

0

55’°

62,0

29>95

W by S

1

Pair.

2

c

69,0

67,0

30,00

W by S

1

Fair.

2

7

c

60,5

65,0

29,98

SW

1

Fair. <

2

0

69.5

68,5

29,98

sw

1

Rain.

3

7

c

5«,°

60,0

29,99

o,ioj

SW

1

Fair.

2

o

7 hS

7°,°

29,97

wsw

1

Fair.

4

7

o

64,0

67,5

29,95

sw

1

Fair.

2

0

76,0

72?°

29,91

sw

1

Fair.

s

7

o

70,0

70,0

29,77

s

1

Fine.

2

o

67,0

71,5

29,74

S by W

1

Rain.

6

7

o

63,°

67,0

29,55

o,4*9

S

1

Cloudy.

2

o

65,0

69,5

29,59

sw

1

Rain.

7

7

0

59>5

69>S

29,555

0,039

SW

1

Fair.

2

0

66,5

68,5

29,62

ssw

2

Cloudy.

8

7

0

58,5

64,5

29,94

0,054

sw

I

Fine.

2

o

7°,°

66,5

29,99

sw

I

Fair.

9

7

o

S6>°

64,0

29,995

ssw

I

Fair.

2

o

69,0

66,0

29,96

S bv W

I

Fair.

IO

7

o

58,5

63,5

29,94

SWbyW

I

Fair.

2

o

74,o

69,0

29,94

SSW

I

Fair.

ii

7

o

5&>5

65,5

29,84

0,360

ENE

I

Rain.

2

c

63,0

68,0

29,85

NEbyN

I

Fair.

12

7

o

62,0

66,5

29,855

0,150

SSW

I

Fair.

2

o

7°>5

69,5

29,86

SW

I

Fine.

13

7

c

61,0

67,0

29,77

0,198

W by N

I

Rainy.

2

c

70,0

7°,°

29,76

WSW

I

Fair.

14

7

0

62,0

67,0

29,85

sw

I

Fine.

2

o

7i>5

69,5

29,80

S by W

I

Fine.

1 5

7

c

62,5

67,5

29,755

0,092

S

I

Fine.

2

0

65,5

68,5

29,71

S by W

2

Fair.

t6

7

o

63,°

67,0

29,58 -

0,064

S

I

Cloudy.

2

o

73>°

70,5'

>9,61

SW

2

Fine.

5

METE

[ 37i ]

METEOROLOGICAL JOURNAL

for July 1776.

Time.

Threm.

Therm.

Barom.

Rain

Winds.

without

within.

H.M.

Inches.

Inch.

Points.

Str.

V V tfl tlivT 9

July 17

7

0

64,0

69,0

29,66

SSW

1

Fair.

2

0

71,0

70,5

29>7*

W by S

1

Fair.

18

7

3°

62,0

67.5

29,82

SWbyW

1

Fine.

'

2

0

74>°

7 0.0

29,82

sw

2

Fine.

l9

7

0

60,5

65.5

29.74

ENE

1

Fair*

2

0

76,0

7

29,68

S

1

Fair.

20

7

0

63*°

68,0

29,71

W by N

1

Fair.

2

0

72,5

71,0

29,81

W by N

1

Fair.

21

7

0

63.0

6 7.o

29,87

SSW

1

Cloudy,

2

0

69,0

69,0

29.85

SSW

1

Fair.

22

7

0

61,0

65.0

29,80

°>275

E byS

0

Cloudy.

2

0

66,0

67,0

29,84

NE

1

Cloudy.

23

7

0

59>°

65.°

29,9°

SW

1

Fine.

2

0

74.o

f9>5

29.95

SWbyW

1

Fine.

24

7

0

63.°

68,5

3°j°3

SW

l

Fair.

2

0

67,0

69>5

30,05

S

1

Rainy.

25

7

0

57.o

63.5

30,22

SSW

1

Fine.

2

0

69,0

67.5

3°.23

sw

1

Fine.

26

7

0

61,0

67,0

3°. *3

SW

1

Fine.

2

0

82,0

73.o

30,08

S by w

1

Fair,

27

7

0

62,5

67.5

3°. *5

SW

1

Fine.

2

0

73>°

70,5

30,18

w

1

Fair.

28

7

0

59,5

67,0

30,22

sw

1

Fine.

2

0

71.5

7°>5

30,J7

SSW

1

Fair. -

29

7

0

62,0

66,0

30,18

NW

1

Fine.

2

0

72,0

7°.5

30,22

W by N

1

Fine.

3°

7

0

61,0

65.0

3°, 3 1

NE

1

F air.

2

0

74.o

7°>5

30,29

E by N

1

Fine.

31

7

0

62,0

65.0

30,24

SE

1

Fine.

2

0

75.°

72,0

30, 2 1

E by S

1

Fine. j

B b b 2

M E T E-

C 37 2 ]

METEOROLOGICAL JOURNAL

for Augnft 1776.

>■ ■

Lime.

Therm.

without

Therm.

within.

Barom

Rain.

Winds.

Weather.

H.

M.

Inches.

Inch.

Points.

Str.

Aug. 1

7

0

6 5,°

66,0

30, 1 6

SW

1

Fair.

2

0

74.o

67,0

3°, 14

S by W

1

Fine.

2

7

0

67,0

68,5

30,i3

E

1

Fair.

2

0

86,o

7 7 5°

3°>°9

S

1

Fine-

3

7

0

62,0

72,5

3°>°9

0,052

W by S

1

Fine.

2

0

76,0

755°

30,06

N

1

Fine.

4

7

0

63.5

68,5

3°, °3

W by N

1

Fair.

2

0

73>°

73>°

30,00

NNW

1

Fair.

5

7

0

66,0

7°.5

29,92

SW

1

Fine,

2

0

79.5

74,5

29,85

wsw

1

Fine.

6

7

0

63.5

7i,5

29,77

NW

1

Fair.

2

0

7 2.°

72,5

29,73

W by N

1

Fair.

7

7

0

56,0

64,0

29,82

SW

1

Fine.

2

0

67.5

67,0

29,84

W

1

Fair.

8

7

0

55.°

61,0

29,64

0,262

SE

1

Rainy.

2

0

65.°

64,5

29,76

NW

1

Fine.

9

7

0

59.5

63.5

29,80

0,067

SE by S

1

Fine.

2

0

66,5

66,0

29,71

SSE

2

Cloudy.

10

7

0

57.o

63,5

29?53

0,452

SSW

1

Rainy.

2

0

66, o

65,5

29,65

w

2

Fair.

1 1

7

0

67,0

65,0

29,76

0,129

SE

I

Fair.

2

0

66,5

66,5

29,71

S

1

Rain.

12

7

0

60,0

64,°

29,75

0,306

SW

I

Finp-.

2

6

66,5

66,0

29,73

SSW

I

Rain.-

13

7

0

S9>°

64,0

29,70

0,169

S W by S

I

Fine.

2

0

67.S

68,0

29,70

W

2

Fine.

H

7

0

55.5

63,5

29,96

°>°54

SW

I

Fine.

2

6

7 1 >5

68,0

29,98

SW

I

Fine.

15

7

0

64.5

67,0

29,88

0,022

SSW

I

Cloudy-

2

0

73>5

71,5

29,80

SW by S

I

Fine^

16

7

0

63.°

67,5

29,61

0,161

S by W

I

Rain.

2

0

69,5 1

70,0 I

29,63

. SSW

2

Fair.

METE

[ 373 I

METEOROLOGICAL JOURNAL

for Auguft 1776.

Time.

Therm.

without

Therm

within.

Barom.

Rain.

Wind

Is.

Weather.

H.

M.

Inches.

Inch.

Points.

Str.

Aug. 1 7

7

0

55>o

63)0

29,76

0,201

wsw

1

Fine.

2

0

67,0

66,0

29,81

wsw

2

Fair.

l8

7

0

5 4;0

62,0

29,875

0,018

w

1

Fine.

2

0

69*5

65)5

29,88

w

1

Fine.

*9

7

0

61,5

64,0

29,64

o?I39

s

1

Rain.

2

0

69,5

68,0

29,64

sw

1

Fair.

20

7

0

59»°

65)5

29,69

0,250

W by S

2

Fair.

2

0

67?5

67,0

29,82

W by S

2

Fine.

21

7

0

57,5

63)0

30,08

ENE

1

Fair.

2

0

67,0

67,0

3°,°9

NE

1

Fine.

22

7

0

54,5

58,0

30,07

NNW

1

Fine.

2

0

67,0

6 5)5

3°)°6

NW

1

Fine.

23

7

c

57,o

62,5

3°)°6

NE

1

Fair.

2

0

70,0

66,5

3°, °5

NE

1

Fine.

24

7

0

54,o

62,0

30,06

W by N

1

Fine.

2

0

64,5

64>5

3°, °7

NW

1

Fair.

25

7

0

53,o

61,0

3°, 10

w

1

Fine.

2

0

66,0

64,0

3°, 1 3

NW

1

Fine.

26

7

0

57,5

6i,5

3°,07

E

1

Cloudy.

2

0

67,0

66,0

30,03

S

1

Cloudy.

27

7

0

57,°

62,5

29,93

0,050

E

1

Cloudy.

2

0

64,5

66,5

29,93

E

1

Fair.

28

7

0

53)0

60,0

29,85

NE

1

Fine.

2

0

69)S

65>5

29,84

SE

1

Fair.

29

7

0

59)°

62,0

29,55

0,050

S by E

1

Rainy.

2

O'

69,0

67)5

29,99

SW

1

Fair.

3°

7

a

57>o

64)5

29,60

0,136

S

1

Fine.

2

0

66,0

67)5

29,60

SW

1

Fair.

31

7

0

54)°

63)5

29,69

0,022

ssw

1

Fine.

2 ‘

0

70,0 |

68,5

29,66

SSW

1 1

Fine.

METE

[ 374 1

METEOROLOGICAL JOURNAL

for September 1776.

Time.

Therm.

without

Therm.

within.

Barom.

Ram.

Winds.

Weather.

H.

M.

inches.

Inch.

Points.

Str.

Sept. 1

7

0

55,5

54>°

29,48

0,120

SW

T

Fine.

2

0

68,5

68,5

29,52

SSW

2

Fine.

2

7

0

S8, s

64,5

29,3°

0,248

S

2

Fine.

2

0

63>5

67)5

29,26

SW

2

Fine.

3

7

0

5^)0

62,5

29,29

0,358

SW

1

Rainy.

2

0

&3)°

66,0

29,41

SSW

2

Cloudy.

4

7

0

55,°

62,5

29,41

0,084

SW

1

Fair.

2

0

63>°

65,5

29,49

W by N

1

Fine.

5

7

0

5‘,o

6 i,o

29,65

0,054

SW

1

Fair.

*

2

0

63,0

65,0

29,72

NW

1

Fair.

6

7

0

53>°

60,5

29,92

0,045

SSW

1

Fair.

2

0

65.5

65,0

30,0°

W by S

1

Fair.

7

7

0

52>5

60,0

29,84

S

1

Fine.

2

0

66,5

65,5

29,75

S by E

1

Fair.

8

7

0

5°>°

61,0

29,48

o,i 60

SW

1

Fair.

2

0

57)5

63,5

29,48

NW

1

Fine.

9

7

0

48,0

57)°

29,90

0,058

N by W

1

Fine.

2

0

66,5

63,5

29,97

N£

1

Fine.

i°

7

0

53)°

60,0

3°, 1 1

N

1

Cloudy.

2

0

63>o

63,5

30,12

SSW

1

Fair.

1 1

7

0

57.°

61,5

30,10

SW

1

Fine.

2

0

68,5

66,5

30,1!

SW

1

Fair.

12

7

0

60,0

64,0

3°, °7

SSW

1

Cioudy.

2

0

68,5

68,0

30,08

s

1

Fair.

13

7

0

57)°

64,5

30,07

S

1

Fair.

2

0

67,0

67,0

30,00

S by W

1

Fine.

14

7

0

57)°

64,0

29,90

NW

1

Fair.

2

0

64,0.

68,0

29,92

NW

1

Fair.

*5

7

0

55)5

62,5

29,99

NE

1

Cloudy.

2

0

61,0

65,0

29,88

NE

1

Cloudy.

16

7

c

6i,5

53>°

29,91

o,377

NW

1

Cloudy.

J L

2

0

61,5

64,5

29,98

W by N

1

Fine.

METE-

[ 375 ]

METEOROLOGICAL JOURNAL

for September 1776.

Time.

Therm.

without

Therm.

within.

Barom.

Rain.

Winds.

Weather.

H.M.

Inches.

Inch.

Points.

Str.

Sept. 1 7

7

0

55, o

62,0

29,99

WSW

1

Cloudy.

2

0

54,5

63,0

29,84

E by N

1

Rain.

18

7

0

49,°

57,5

29,86

0,638

N

1

Cloudy.

2

0

57, o

61,0

29, 94

N

2

Fair.

*9

7

0

47>°

5 4,°

3°,°5

0,082

N

1

Fair.

2

0

5°,°

5 7,5

3°,I2

NE

1

Rain,

20

7

c

44,5

52,5

3°,25

0,178

NNE

1

Fine.

2

0

52,0

57,5

30,26

NNE

1

Fine.

21

7

0

43,°

52,0

3°, 3°

0,160

N

1

Fine.

2

0

57>5

57,°

3°,35

$

E

1

Fair.

22

7

0

46,5

52,5

3°, 33

NNE .

1

Fair.

2

0

59,o

57,5

3°,23

E

1

Fine.

23

7

0

45,5

53,5

29,99

NE

1

Fine.

2

0

60,0

58,0

29,92

NE

1

Fair.

24

7

0

48,0

55,o

29,91

N

1

Fair.

2

0

63,5

60,5

29?7i

NE

1

Fine.

25

7

0

54,o

57,5

29,70

SE

1

Cloudy.

2

0

66, o

62,5

29?57

SE

1

Fine.

26

7

0

56,5

6i,5

29.3°

0,131

S

1

Fine.

' 2

0

63,0

65,0

29 >3°

S

2

Fair.

27

7

0

48,°

58,5

29.55

s

1

Fair.

2

0

6j,o

62,5

29,64

S by W

1

Fine.

28

7

0

57,°

60,0

29,52

0,019

ssw

1

Rain.

2

0

62,0

63,0

29,59

sw

1

Fine.

29

7

0

49,5

59,o

29,80

WNW

1

Fine.

2

0

61,5

62,5

29,97

NE

1

Fine.

3°

7

0

51,0

58,0

29,99

NNE

1

Fair.

2

0

61,5

62,5

30,00

NE

1

Fine.

METE-

[ 376 ]

METEOROLOGICAL JOURNAL

for Odtober 1776.

Time.

Therm.

without

Therm.

within.

Barom.

Rain.

Winds.

Weather.

H. M.

Inches.

Inch.

Points.

Str.

oa. 1

7

0

52,0

58,5

29,92

NE

1

Fair.

2

0

59»5

62,0

29,92

ENE

1

Fair.

2

7

0

54? 5

60,0

3°,°5

NE

1

Cloudy.

2

0

66,5

64.5

3°, 10

NNE

1

Fair.

3

7

0

55?°

62,0

3°, 2 1

NE

1

Cloudy.

2

0

60,0

64,0

3°, 2 1

N

1

Cloudy.

4

7

0

53>°

65,0

30, j°

SSE

1

Cloudy.

2

0

58.o]

63,0

29,98

NW

1

Fair.

5

7

0

46,5

57.5

29,83

WNW

1

Fair.

2

0

56,5

60,5

29,80

NNW

1

Fair.

6

7

0

44,5

55.0

29,78

NNE

1

Fair.

2

0

5S>°

57.5

29,77

NNW

1

Fine.

7

7

0

42,0

52>o

29,76

ssw

1

Fine.

2

0

58,5

57,5

29,65

sw

2

Rain.

8

7

0

49,°

55.0

29,84

0,020

s

1

Fair.

2

0

61,0

59,5

29>75

s

2

Cloudy.

9

7

0

43>S

54.5

3°>J 7

0,012

s

I

Fine.

2

0

58,0

58,5

3°>23

wsw

2

Fine.

10

7

0

57>°

58,5

3°>12

wsw

I

Fair.

2

0

66,5

63,5

30,18

w

I

Fair.

11

7

0

53>°

60,0

3°?:7

wsw

I

Fine.

2

0

62,5

64)5

S0?^

NNW

I

Fair.

12

7

0

49)5

58,5

30,28

N

I

Fair.

2

0

57)5

61,5

3°?32

NE

I

Fine.

*3

7

0

52)0

58,0

30,28

SW

I

Cloudy.

2

0

58.5

62,0

3°?24

NW

I

Cloudy.

H

7

0

5J>°

59,o

30? 1 7

j

w

I

Cloudy.

2

0

57)0

61,5

3°,i6

!

s

I

Cloudy.

15

7

0

57)5

58,5

30,16

NNW

I

Cloudy.

2

0

57.0

61,5

30, 10

SE

I

Cloudy.

16

7

0

44,0

53,5

29,92

NE

I

Foggy.

2

0

6l,0

60,0

29,88

S by E

I

Fair.

.. •

METE-

[ 377 ]

METEOROLOGICAL JOURNAL

for October 1776.

Time.

Therm.

without

Therm.

within.

Barom.

Rain.

Winds.

Weather.

1

H

M

Inches.

Inch.

Points.

|Str.

0&. 17

7

0

58,0

60,0

29,80

S

i

Fair.

2

0

58,0

62,5

29,85

NNW

1

Rain.

18

7

0

43)5

55,°

30,23

0,152

SW

1

Fair.

2

0

59>°

6o?o

30,1 9

S

1

Fine.

J9

7

0

52,5

57?o

29,86

E by N

\ l

F°ggy*

2

0

61,5

61,5

29,80

S

1

Rain.

20

7

0

56>°

59,°

29,73

s

1

Fair,.

2

0

56,0

62,0

29,84

W by N

1

Rain.

21

7

0

46,0

55,5

30,01

0,356

SSE

1

Cloudy,

2

0

59>°

60,0

29,97

S by E

1

Fine.

22

7

0

55,5

58,0

29,99

S

1

Fair.

2

0

65,0

64,0

3°,°4

S

1

Rain.

23

7

0

5S,o

60,0

30,10

NE

1

Cloudy,

2

0

s6,o

62,0

30,12

NE

1

Cloudy.

24

7

0

56>o.

6o,o

30,i4

E byN

1

Cloudy.

2

0

55,o

6i,5

3°,!4

NE

1

Cloudy.

25

7

0

5L°

5^,5

30,0 1

NE

1

Cloudy.

2

0

54,0

59 0

29,93

NE by E

1

Fair.

26

7

0

48,0

54,0

29,84

N

1

Cloudy,

2

0

51,0

5^,5

29,85

NNE

1

F air.

27

7

0

43,5

5**5

29,90

NNW'

1

Cloudy.

2

0

52,0

55,5

29,93

N

1

Fine.

28

7

0

38,0

49,5

30,04

NE

1

Fair.

2

Q

5L°

55,o

3°,°4

E

1

Fine,

29

7

0

49,°

52,5

3°, °3

SE

1

Cloudy,

2

O

53,°

55,5

30,00

ESE

1

Rain.

3°

7

O

49>°

54,o

30,01

0,194

SE

2

Fair.

2

0

54,o

57,5

30,96

SSE

1

Fine.

3i

7

O

43,o

51,0

29,85

ENE

1

Cloudy, 1

2

0

48,0

53,5

29,89 |

NE

1

Fine.

Vol. LXVII

C c c

M E T E

I 378 ]

METEOROLOGICAL JOURNAL

for November 1776.

Time.

Therm.

without

Therm.

within.

Barom.

Rain.

Winds,

Weather.

H. M.

Inches.

Inch.

Points.

Str.

Nov. 1

7

O

37,5

47?5

29>94

E

I

Fair.

2

0

50,0

52>°

29,82

Sby E

I

Fair.

2

7

O

39>°

48,5

29,78

0,165

ssw

I

Fair.

2

O

49,5

5 2>°

29,78

W by N

I

Fair.

3

7

O

33,5

45>°

30,06

s

I

Fair.

2

O

44,0

49>°

3°>J 1

sw

I

Fair.

4

7

O

38>5

44,5

30,16

sw

I

Fine.

2

O

54>°

5°>°

3°, *4

s

I

Fine.

s

8

0

49,0

5°, 0

30,18

ssw

I

Fair.

2

0

54,0

54,0

30,19

NW

I

Cloudy.

6

8

0

36,0

47,5

3°, 1 7

NE

I

Foggy.

2

c

44,0

50,5

30,10

NE

I

Fair.

7

8

0

40,°

46,5

30,02

NE

I

Foggy.

2

0

5r,5

5!,°

30,00

NE

I

Foggy.

8

8

0

4°,°

49,0

30,01

NE

I

Foggy-

2

0

54,0

56,0

29,98

NE

I

Foggy.

9

8

0

40,5

47,0

29^92

N by E

I

Foggy.

2

0

55,°

5i,5

29,92

S by E

I

Fair.

10

8

0

49,°

5i,5

29>97

SE

I

Foggy.

■

2

3d

52>5

54,5

29,97

S

I

Cloudy,.

1 1

8

0

49,0

53,5

29,90

s

I

Fair.

2

0

50,5

56,0

29,85

SE

I

Cloudy.

12

8

0

42,0

52,5

30,02

0,136

SW

I

Fair.

2

0

52,0

55,5

3°,”

<

W by S

I

Fine.

13

8

0

48,0

53,°

3°, 1 3

sw

I

Fine.

2

0

55, S

56,5

3°, r3

sw

I

Fine.

14

8

0

52>5

55,5

30,23

0,010

sw

I

Cloudy.

2

0

57,o

58,5

30,21

sw

I

Cloudy.-

15

8

0

48,5

55,5

30,22

0,025

sw

I

Fair.-

2

0

565°

57,5

3°, 12

sw

I

Fair;

16

8

0

57?5

58,0

29,73

sw

I

Cloudy.

|

-2

.0

£5>°

59,5

29,95

sw

I

Cloudy.

■METE'

C 379 1

METEOROLOGICAL JOURNAL

for November 1776.

Time.

Therm.

without

Therm.

within.

Barom.

Ram.

W inds.

W eather.

H.M

Inches.

Inch.

Points. !

■St x.

Nov. 1 7

8

0

45>5

55,o

29,67

0,010

SW

1

Fair.

2

0

49,5

56,o

29,77

w

1

Fair.

18

8

0

42, °

5°,o

29,87

w

1

Fair.

2

0

5i,5

53,o

29,74

SW

1

Fair.

*9

8

0

49,0

53,o

29,71

s

0

Rain,

2

0

52,0

55,o

29,67

0,140

SE

1

Rain.

20

8

0

53, 0

56,°

29,32

SW

2

Fair.

2

0

58,0

59,5

29, 36

0,089

SW

2

Rain.

21

8

0

40,0

49,5

29,70

WNW

2

Fine.

2

0

45>°

51,0

29>75

0,080

SW

1

Fine.

22

8

0

33.0

45,o

29,94

SW

1

Fair.

2

0

43.°

48,0

29,89

w

1

Fair.

23

8

0

4°>°

45,5

29,36

S by E

1

Rain.

2

0

43.5

48,0

29,23

0,840

SE

1

Rain.

24

8

0

36.°

44.Q

29,61

N by E

2

Fair.

2

0

42,0

46,5

29,94

0,176

NW

2

Fine.

25

8

0

33.0

41,0

30,16

N

1

Fine.

2

0

41,0

45,o

30,20

N by E

1

Fine.

26

8

0

28,0

39,5

30,39

E by N

1

Foggy*

2

0

37.0

43,5

30,31

NE

1

Fine.

27

8

0

31.0

37,o

30,09

E

1

F roily.

2

0

36,0

4°»o

29,97

SE.

1

Fair.

28

8

0

34,o

48,5

29,655

SE

1

Cloudy.

2

0

35»o

42,0

29,52

SE

1

Cloudy.

29

8

0

38,0

40,5

29,11

SE

1

Rain.

j

2

0

46,5

45,o

29,11

SE

;

Cloudy..

3°

8

0

41,0

45,5

29,37

0,520

SW

1

Rain.

2

0

47,o

40,0

29,44

SW

1

Fine, . j

C c c 2

METE'

[ 38o ]

METEOROLOGICAL JOURNAL

for December 1776.

Time.

Therm

without

Therm.

within.

Barom.

Rain.

Winds

!.

Weather.

H. M.

Inches.

Inch.

Points.

Str.

Dec. 1

8

0

5°>°

5°,°

29,48

0,222

S

2

Fair.

2

0

54,Q-

54»°

29,69

SSW

2

Cloudy.

2

8

0

47^°

ShS

3°,°4

SE

1

Rain.

2

o'

52>5

54,5

29,97

E

1

Fair.

3

8

0!

44,5

5i,5

29,985

E

1

Foggy.

2

0

51,0

54,o

29,96

SE

1

Fair.

4

8

0

5° 5

53,5

29,95

SSW

1

Foggy.

2

0

55, o

56,°

29>97

S by W

1

Cloudy.

5

8

0

49,5

5°,°

3°,Ol

SE

1

Cloudy.

2

0

53>°

56,0

SO,06

N by E

1

Cloudy.

6

8

0

47,°

54,5

29,95

0,052

NE

1

Cloudy.

2

0

48,0

55,o

29,91

NE

1

Cloudy.

7

8

0

42,0

50,0

29,95

ENE

1

Fair.

2

0

43,5

52,0

29,97

S by E

1

Fine.

8

8

0

43>°

47,0

3°, °5

E

1

Fair.

2

0

50,5

52,0

30,06

SE

1

Fair.

9

8

0

42,0

49,5

30.10

SSE

1

Fine.

2

0

44,0

49,5

3°, 11

SE

1

Fine.

10

8

0

42,0

47>o

30,20

S

1

Cloudy. .

2

0

46,0

48,5

30,25

sw

1

Cloudy.

11

8

0

46,0

48,5

3°, 35

sw

1

Fine.

2

0

53>°

5i,5

3°,4i

sw

1

Fine.

12

8

0

49,0

52,0

30,42

sw

1

Cloudy.

2

0

57,5

52,5

30,39

w

1

Cloudy.

*3

8

0

47>°

57,5

30,34

0,057

NE

: r:i

Cloudy.

2

c

47,°

52,0

30,32

NE

17 1

Rain.

14

8

0

46,0

50,5

30,33

0,055

SSW

I

Cloudy.

2

0

47,°

51,0

30,27

SE

I

Cloudy.

15

8

0

39>°

47>°

30,09

SE

I

Fair.

2

0

42,0

47,o

29,99

SW

I

Cloudy.

16

8

c

40,0

46,0

29,73

0,409

N

Rain.

0

—

0

44,°

46,0 ,

29,73

NW:

I

Fine.

METE

C 381 3

METEOROLOGICAL JOURNAL

for December 1776.

Time.

Threm

withou

Therm

within.

Barom.

Rain.

Winds.

Weather.

fi.M.

Inches.

Inch

Points.

Str

Dec. 17

8

0

3°,°

41,0

29,755

0,02c

» NNW

1

Fine.

2

0

36,0

4J>°

29)755

NW

1

Fine.

18

8

0

26,0

35)0

29,59

WNW

1

Cloudy.

2

0

32,0

35)0

29)55

S by W

I

Frofty.

*9

8

0

38>°

36,5

29,I6

°>I39

W by N

2

Rain.

2

0

4°,o

37)0

29,32

W

I

Fair.

20

8

0

35.0

37,o

29)47

ssw

1

Cloudy.

• 2

0

36,°

39>°

29,47

NE

I

Rain.

21

8

0

52,0

39,o

29,69

0,109

sw

I

Rain.

2

0

54>o

4J,o

29,58

sw

I

Rain.

22

8

0

52>°

46,0

29,765

0,053

wsw

2

Cloudy.

2

0

54>°

46,0

29,84

wsw

I

Fair.

2 3

8

0

42,0

48,0

29,87

0,050

SW

I

Fair.

2

0

46> 5

48,5

29,81

WNW

I

Fine.

24

8

0

3 9>°

44,o

29)57

0,022

NW

2

Fair.

2

0

39.°

44,o

29^5*

WbvN

2

Rain.

25

8

0

35>5

3S,5

29)77

0,047

NW

2

Fine.

2

0

39>°

40.0

29,82

N by W

I

Fine.

26

8

0

30)0

36>5

29,81

N

I

Fine.

2

0

36,0

37,o

29,76

NE

I

Rain.

27

8

0

33>°

36>°

29,98

N

I

Cloudy,

2

0

36)0

37,o

29,87

NE

I

Cloudy.

28

8

0

29,0

35,o

30,00

N

I

"air.

2

0

33>°

35,o

30,02

NNE

I

Tair.

29

8

0

32>°

33,5

29,73

N

I

?air.

2

0

36>S

34,5

29,62

W by N

I

Fair.

3°

8

0

32>°

34,5

29)47

0,040

N

I

Snowy.

2

0

29,0

34,o

29,49

N by E

I

Fine and frofty.

31

8

0

25,0

30,5

29,71

N

I

Fair and frofty.

2

0

31)0

31,0

29,88

NW

1

Fair and frofty. J

t 38, ]

— — •—

rhermometer without.

Thermometer v

mli in.

Barometer

•

Rain.

.

1776.

3 rente ft
Height.

Leaft

Height.

Mean

Height.

Greateft

Height.

Leaft

Height.

Mean 1
Height.

Greateft

Height.

Leaft

Height.

Mean

Height.

Inches.

January

44,5

*3,5

29’3

43,5

20,5

31,8

3°,x4

29,21

29,687

M57

February

49,5

14,5

42,6

46,0

• 9,0

42,4

29,97

28,84

29,408

3>5X0

March

5Z>° "

3°, 5

45,9

56,o

37,0

46,4

30,43

28,98

29,91

I,54I

April

56,5

34,5

50,3

58,0

41,0

S • *2

3°, 44

29,46

29,542

0,320

May

62,0

40,0

54,3

66,0

47,0

54,9

30,46

29,14

29,999

L594

June

66,0

32,5

62,4

70,5

54,5

64,2

30,34

29,48

29,87

2,028

July

70,0

55,o

65,9

70,0

60,0

68,3

3o,3i

29,55

29,913

x,752

Auguft

67,0

53,°

64,2

72,5

58,0

66,1

30,16

29,53

29,546

2,540

September

61, s

43,°

57,2

64>5

s2,o

66, 1

3 o,35

29,26

29,83

2,712

O&ober

58,0

42,0

53,8

65,0

51,0

53,4

30,32

29,65

30,00

o,734

November

57,o

28,0

45,o

58,0

37,0

49,9

30,39

29,11

29,878

1,19!

December

52,0

25,0

42,0

57,5

3°, 5

45,°

30,42

29,16

29,882

x,275

Whole Year.

1

5M

52,9

29,789 120,354

VARIATION

I 3S3 1

VARIATIO N-N E E D L E.

7

A.M.

12 h, ]
M

2 h.

! P.M.

ioor 1 1 h.

P.M.

Daily

Mean.

June

21

21

52

21

45

21

49

22

21

38

21

49

21

52

22

20

21

55

23

21

43

21

42

21

43 1

21

47

21

44

24

21

41

21

49

21

54

2 1

36

21

45

25

21

57

21

54

21

53

9 1

4*

21

51

26

21

43

z*

47

2JL

49

21

33

21

43

27

21

38

21

48

21

50

21

37

21

43

28

21

43 -

21

47 ,

21

40

2.1

37

21

42

29

21

59

21

5i

21

45

21

36

21

48

3°

21

39

21

49

21

44

21

34

21

42

July

i

22

00

21

Si

21

50

21

40

21

50

2

21

36

21

So

- - \

2;I

54

21

46

21

47

3

21

59

21

49

2-1

5°

21

46/

21

5f

4

21

40

21

55

21

52

21

47 ,

21

49

5

21

40

21

56

21

56

,21

46

21

49

6

21

40

21

5o

21

53

24

35

21

49

7

22

00

21

49

21

•49

21

53

21

53

Means, -
«•

21

46

M

21 50
'ean. of ;

21 50

all 21

21

(■7*

43

1

DIPPING—

[ SB4 1

DIPPIN G-N E E D L E.

J

7 h-

12 h.

2 h.

ioor 1 1 h.

Mean.

A.M.

M.

P.M.

P.M,

0 /

0 /

0 t

0 /

0 /

June 21

71 32

71 36

*

22

72 22

71 40

71 40

71 45

7i 43

Weft mark up-

23

71 4C

71 50

7i 45

71 30

permoft.

24

71 5°

7« 35

7* 45

71 35

25

7i 37

73 10

73 00

72 45

26

73 20

72 50

73 05

73 00

73 01

Eaft.

27

73 °5

73 20

73 »5

72 20

28

73 10

71 50

7i 5°

71 50

29

72 05

72 20

72 00

71 40

3°

July 1

71 35

72 00

71 5°
7i 5°

71 5°
71 50

72 10
7i 50

71 56

Eaft mark
down.

2

7i 55

70 50

71 52

71 50

-

3

71 5°

7i 50

7i 55

72 00

4

72 00

7 1 57

73 i°

73 30

5

73 20

73 25

73 20

73 30

73 22

Weft.

6

73 3°

73 24

73 20

73 20

7

73 25

73 *5

73 20

73 25

72 3°

'

There are SIX PLATES in the First Part
of the PHILOSOPHICAL TRANSACTIONS,
Vcl. LXVII. But the Second of them, containing
Two diftindt Subjects, is numbered Tab. II. at the
Head, and Tab. III. below.— -This is mentioned, left
the Binder, attending to the Number at the Head only,
ihould fuppofe the Third Plate to be wanting.

I

PHILOS OPHICA L

TRANSACTIONS,

OF THE

ROYAL SOCIETY

O F

LONDON.

VOL. LXVII. For the Year 1777.
PART II,

LONDON,

PRINTED BY J. NICHOLS, SUCCESSOR TO MR. BOWYER ;
FOR LOCKYER DAVIS, PRINTER TO THE ROYAL SOCIETY.

MDCCLXXVIIL

• *

[ V ]

CONTENTS

T Q

V O L. LXVII. Part II.

XX. Account of a Volcanic Hill near Invernefs.

In a Letter from Thomas Weft, Efq. to Mr.

Lane, F, R. S. Page 385.

XXI. New Elehlrical Experiments and. Obfervations ; with

an Improvement of Mr. Canton’s FleBrometer. By
Mr. Tiberius Cavallo, in a Letter to Mr. Henly,
F. R. S. p. 388

XXII. Barometrical Obfervations on the Depth of the Mines

in the- Hartz. By John Andrew de Lue, F. R. S. In
a Letter to Sir John Pringle, P. R. S. p. 401

XXIII. Fhe general Mathematical Laws which regulate
and extend Proportion univerfally ; or, a Method of
comparing Magnitudes of any Kind together , in all the
pojfible Degrees of Increafe and Decreafe. By James
Glenie, A. M. and Lieutenant in the Royal Regiment of
Artillery. p. 450-

XXIV. .

vi CONTENTS.

XXIV. The Cafe of Ann Davenport. By Mr. Fielding
Be ft Fynney, Surgeon at Leek, in Staffordfhire ;
communicated to Thomas Perci al, M. D. F. R. S. and
by him to Sir John Pringle, Bart. P. R. S. p. 45 8

XXV. An Account of the Kingdom of Thibet. In a

Letter from John Stewart, Ff quire , F. R. S. to Sir
John Pringle, Bart. P. R. S. p. 465

XXVI. Of the Degrees and Quantities of Winds requifte
to move the heavier Kinds of Wind Machines. In a
Letter from John Stedman, M. D. Fellow of the Royal
College of Phyjicians at Edinburgh , to the Reverend
Samuel Horfley, LL.D. Secretary to the Royal Society .

P- 493

XXVII. Defcription of the Jefuits Bark Tree of Jamaica
<and the Caribbees. By William Wright, M.D. Member
of the Philofophical Society of America, and Surgeon-
general in Jamaica. Communicated by Jofeph Banks,
Ef quire , F. R. S. p. 504

XXVIII. Defcription and Ufe of the Cabbage-bark Tree
of Jamaica. By William Wright, M. D. ; commu-

. nicated by Richard Brocklefby, M. D. F. R. S. p, 507

XXIX. Obfervations made in Savoy, in order to afcertain
the height of Mountains by means of the Barometer ;
being an Examination of Mr. De Luc’s Rules , deli-
vered in his Recherches fur les Modifications de l’At-
mofphere. By Sir George Shuckburgh, Bart. F. R. S.

P-513

XXX. An Account of the Bramin’s Obfervatory at Benares.

By Sir Robert Barker, Knt. F. R. S.; in a Letter to
Sir John Pringle, Bart. P. R. S. P-598

XXXI. A

CONTENTS.

vn

XXXI. A port Account of Dr. Maty’s Illnefs , and of the
appearances in the dead Body , which was examined on
the 3< i of July, 1776, the Day after his Deceafe. By
Dr. Hunter and Mr. Henry Watfon, FF. R. S. p. 608
XXXII. An Account of fome Experiments made with an
Air-pump on Mr. Smeaton’s Principle; together with
fome Experiments with a common Air-pump. By Mr.
Edward Nairne, F. R. S. p. 614

XXXIII. On the Culture of Pine-apples. An extract of a
Letter from William Baftard, Efq. of Kitley in Devon-
fhire, to Samuel Mufgrave, M. D. F. R. S. dated
Kitley, March 15, 1777. Communicated to the Society
by Dr. Mufgrave. p. 649

XXXIV. Experiments and Obfervations made in Britain,
in order to obtain a Rule for meafuring Heights with
the Barometer, By Colonel William Roy, F. R. S.

P- 653

XXXV. Account of a new Micrometer and Megameter
By the Abbe Bofcovich, &c. p. 789

XXXVI. Account of a new Injlrument for meafuring fmall
Angles^ called the prifmatic Micrometer. By the Rev.
Nevil Mafkelyne, D. D. F. R. S. and Ajlronomer-

Royal. P-799

XXXVII. the Report of the Committee appointed by the
Royal Society to confider of the befl Method of adjufting
the fixed Points of thermometers ; and of the precau-
tions necejfary to be ufed in making Experiments with
thofe Injlruments. p. 816

PHILOSOPHICAL

TRANSACTIONS.

XX. An Account of a Volcanic Hill near Invernefs. In
a Letter from Thomas Weft, Efq. to Mr. Lane, F, R. S.

DEA* oa. 27^7,6.

Read Dec. 12, A S you feem defirous to have a more par-
1776. f~\

ticular account of the lava, which I
left at your houfe on my return from my tour in Scot-
land, I herewith fend it you. At the fame time I muft
own, that the little attention paid to fo extraordinary a
phenomenon, and which feems to prove beyond a doubt
the exiftence of volcanos in this country, is to me matter
of great furprize.

The hill from whence I took the fpecimens of lava
which I have the pleafure to fend you, is about a mile
Vol. LXVII. E e e and

386 Mr. west’s Account of

and an half diftant from Invemefs, and is called by the
inhabitants Creek Faterick, or Peter’s Rock : the lower
part of it is chiefly ploughed up; the upper part is ex-
tremely fteep, craggy, and very difficult of accefs, and
appears to me to have evident marks of having been a
volcano, as by much the greateft part of the largeft
rocks on it have been either ftrongly calcined or fufed,
as will, I think, plainly appear by thefe fpecimens, fome
of which I picked up on the fides of the hill, others I
broke off from the folid rock with a pick-axe (though
not without great difficulty, on account of the extreme
hardnefs of the rock) ; and others I dug out from the
fummit of the hill, at the depth of four feet, lying in
a rich, light, black mould, which, after having been ex-
pofed to the air for fome time, turned to a whitilh afh
colour.

On the fummit of this hill (which commands a moll
beautiful and extenfive profpedt) is a fmall plane, ninety
paces long, by twenty-feven wide, furrounded by rocks,
from fix to eight feet high, like a breaft-work, extremely
craggy, and difficult of accefs on the outfide, but riffng
from the center, in the infide, to the top of the breaft-
work, with a gentle flope of turf, equal to any of the
fineft on our fheep downs.. This I at firft thought might
have been the crater; but the fmoothnefs of the infide
leeming not to favour this opinion, I carefully examined
2. every

a Volcanic Kill near Invernefs. 387

every part of the hill, in hopes of finding fome marks
of one, but without fuccefs. There are, indeed, feveral
fmall caves, but of no great depth, which feem to be
fonjied by the hanging rocks on the fides, near the top
of the hill. There is alfo a fmall fpring about fifty
yards from the top of the hill, but it was almofi: dry
when I faw it, which was the latter end of July. I could
not get, from the belt inquiries I was able to make, any
account of this extraordinay phenomenon, no perfon in
Invernefs (except one gentleman of that city) having
ever taken the lead: notice of it ; nor can I find that any
mention has ever been made of it in hiftory, though it
feems probable that there has been at lead: one more in
this part of the country ; as a gentleman near Dingwal,
which is about twenty miles from Invernefs, allured me,
that there were many ftones on a hill near his houfe
which they called the vitrified fortification, that had the
fame appearance with thofe at Creek Faterick; but that
no perfon had ever taken any particular notice of them^.

I am, 8tc.

(a) The fpecimens fent with the above letter to the Royal Society, having
been examined by fome members well acquainted with volcanic productions,
were by them judged to be real lava ; and it was their opinion, that if a great
quantity of the like fubilance be found on the hill from whence thefe pieces
were taken, the hill mod probably owes its origin to a volcano. J. P.

[ 388 ]

XXI. New Electrical Experiments and Obfervations ; with
an Improvement of Mr. Canton’s Electrometer. By
Mr. Tiberius Cavallo, in a Letter to Mr. Henly,
E. E. S.

DEAR SIR, FebmaryT.77 *

Read March 13, rr^OGET HER with this letter I fend

1 7 7 7 • 8

■*“ you an account of fome electrical
experiments I have lately made, and moft of which have
been fuccefsfully repeated in your prefence. As you did
me the honour to mention, in your laft paper to the
Royal Society, fome remarks I had made on Mr. volta’s
machine, I hope you will farther oblige me by prefent-
ing this account to that learned Body, if you think it
contains any thing deferving the attention of the
curious.

I am, 8cc.

Experiments

Mr. cavallo’s Experiments , 8cc.

389

Experiments on Mr. yolta’s plates , commonly called a
machine for exhibiting perpetual eledlricity.

THE following experiments, which fhew how both
lides of an eleCtric plate are affeCted in different circum-
ftances, wrere principally made with a plate which mea-
fured fix inches and a quarter in diameter, and which
confifled of a circular piece of thick glafs coated on one
lide with fealing-wax1^.

If, after having excited the fealing-wax, I lay the plate
with the wax upon the table, and the glafs uppermoft,
that is, contrary to the common method; then, on
making the ufual experiment of putting the metal plate
on it, and taking the fpark, &c. I obferve it to be attended
with the contrary electricity ; that is, if I lay the metal
plate upon the eledtric one, and, while in that fituation,
touch it with an infulated body, that body acquires the

(a) Having conftru&cd feveral of thofe plates, with a view to difcover which
iubftance would anfwer the bed for coating the glafs plate, I obferved that the
ealieft to be made, and the flrongeil in power, are thofe made of the fecond fort
of fealing-wax. It is remarkable, that fometimes they will not adf well at iirfb,
but they may be rendered very good by fcraping with the edge of a knife their
Alining or gloffy- fur face. This feems analogous to the well-known property of
glafs, which is, that new cylinders or globes made for eledlrical purpofes are
often very bad electrics at firft, but that they improve by being worked, that is,
by having their furface a little worn.

pofitive

390 Mr. cavallo’s Experiments and

pofitive eledtricity, and the metallic removed from the
eledtric plate appears to be negative.

This experiment, I find, an.fwers in the fame manner
if an eledtric plate be ufed which has the fealing-wax
coating on both fides ; for, whichever fide of this is ex-
cited, it will adt like the waxed fide of the above de-
icribed plate, that is, will render the metal plate fet on
it pofitive, and the oppofite fide will render it negative.

If, inftead of laying the eledtric plate upon the table,
it be placed upon an eledtric ftand fo as to be accurately
inful ated, then the metal plate fet on it acquires fo little
eledtricity that it can only be difcovered with an eledtro-
meter; which fhews, that the eledtricity of this plate will
not be confpicuous on one fide of it, if the oppofite fide
be not at liberty either to part with, or acquire more of,
the eledtric fluid. In confequence of this experiment,
and in order to afcertain how the oppofite fides of the
eledtric plate would be affedted in different circumftances,
I made the following experiments.

Upon an eledtric ftand I placed a circular tin plate,
nearly fix inches in diameter, which by a flender wire
communicated with an eledtrometer of pith-balls, which
was alfo infulated; I then placed the excited eledtric plate
of fix inches and a quarter diameter upon the tin plate,
with the wax uppermoft, and oh removing my hand

from

Obfervaiions in EkBricity. 39-r

from it, the electrometer which communicated with the
tin plate, that is, with the under fide of the electric plate,
immediately opened with negative electricity. If by
touching the electrometer I take that electricity off, the
electrometer will not afterwards diverge. But if now,,
©r when the electrometer diverges, I prefent my hand
open, or any other uninfulated conductor, at about one or
two inches over the eleCtric plate, without touching it,,
then the pith- balls .diverge; or, if they diverged before,
they come together, and immediately diverge again with
pofitive electricity. — Remove the hand, and the balls
come together ; approach the hand, and they diverge,,
and fo on.

If while the pith-balls diverge with negative electri-
city, I put the metal plate upon the wax, the balls ap-
proach each other for a little time, but foon open again
with the fame, that is with negative electricity.

If, whilft the metallic lies upon the eleCtric plate, I
touch the former, the. electrometer immediately diverges'
with pofitive electricity, which if by touching the elec-
trometer I take off, the electrometer continues without
divergence. I touch the metal again, and the electro-
meter opens again.; and fo on for a confiderable number
of times, until the metal plate has acquired its full
charge. On taking now the metal plate up, the electro-
meter

392, Mr. cavallo’s Experiments and

meter inftantly diverges with ftrong negative elec-
tricity.

I repeated the above experiments with this only dif-
ference in the difpofition of the apparatus: I put the
electric plate with the excited fealing-wax upon the
circular tin-plate, and the glafs uppermoft : and the dif-
ference in the refult was, that where the electricity was
poiitive in the former difpofition of the apparatus, it now
became negative, and vice verja\ except that, when I
firft lay the eleCtric plate upon the tin plate, the electro-
meter diverged with negative electricity as well in this
as in the other difpofition of the apparatus.

All the above experiments have been repeated with
an eleCtric plate, which, befides the fealing-wax coating
on one fide, had a ltrong coat of varnifh on the other;
and their refult has been fimilar to thofe when the above
defcribed plate was ufed.

Experiments on colours .

Having accidentally obferved that an eleCtric Shock,
fent over the furface of a card, marked a black ftroke
upon a red fpot on the card, I was from this induced to
try what would be the effeCt of fending Shocks over
cards painted with different water colours. Accordingly
4 I painted

Obfervations in Eleclricity. 393

I painted feveral cards with almoft every colour I had,
and fent {hocks over them when they were very dry :
the effects were as follows

Vermillion was marked with a ftrong black track,

v

about one-tenth of an inch wide.

Carmine received a faint and {lender impreffion, of a
purple colour.

Verdigreafe was fhaken off from the furface of the
card.

White lead was marked with a ftrong black track,
not fo broad as that on vermillion.

Red lead was marked with a faint mark much like
carmine.

The other colours I tried were, orpiment, gamboge,
fap-green, red ink, ultramarine, Pruffian blue, and a few
others, which were compounds of the above, but they
received no impreffion.

It having been infinuated, that the ftrong black mark,
which vermillion receives from the eledtric {hock, might
poffibly be owing to the great quantity of fulphur con-
tained in that mineral, I was induced to make the fol-
lowing experiment. I mixed together equal quantities
of orpiment and flower of fulphur, and with this mix-

(b) The force employed was the full charge of one foot and a half of coated
glafs.

VOL. LXVII. Fff true,

F f f

394 Mr. cavallo's Experiments and
ture, by the help, as ufual, of very diluted gum* water,
I painted a card; but the electric fhock fent over this
left not the lead: impreffion.

Defirous of carrying this invefligation on colours a
little farther, I procured fome pieces of paper painted on
both fides with oil colours ^ and fending the charge of
two feet of coated glafs over each of them, I obferved
that the pieces of paper painted with lamp-black, Pruf-
fian blue, vermillion, and purple brown, were torn by
the explofion \ but white lead, Naples yellow, Englifh
ochre, and verdigreafe, remained unhurt.

The fame fhock lent over a piece of paper, painted
very thick with lamp-black and oil, left not the leaft
impreffion. I fent the fhock alfo over a piece of paper,
unequally painted with purple-brown, and the paper was
torn where the paint laid very thin, but remained un-
hurt where the paint was evidently thicker.

Having repeated thofe experiments feveral times, and
with fome little variation, they were attended with dif-
ferent effe<fts ; however, they all feem to point out the
following proportion.

I. A coat of oil-paint over any fubftance, defends it
from the effects of fuch an electric fhock as would other-
wife injure it; but by no means defends it from the force

(c) The colours were mixed with linfeed oil.

1

of

Qbfervations in Electricity. 395

of every eie&ric fliock that can be given. II. No one
colour feems preferable to the others, if they be equal
in fubftance, and equally well mixed with oil; but a
thick coating does certainly afford a better defence than a
thinner one.

By rubbing the above mentioned pieces of paper, I find
that the paper painted with lamp-black and oil is more
eafily excited, and acquires a ftronger eleilricitv than the
papers painted with the other colours ; and perhaps on
this account it may be, that lamp-black and oil might
refill the fhock fomewhat better than the other paints.

It is remarkable, that vermillion receives the black
impreffion, when painted with oil, nearly as well as
when painted with water. The paper painted with white
lead and oil receives alfo a black mark, but its nature is
very particular. The track, when firft made, is almofl
as dark as that marked on white lead painted with wa-
ter; but it gradually lofes its blacknefs, and in about two
hours after it appears without any darknefs, and when
the painted paper is laid in a proper light appears only
marked with a colourlefs track, as if made by a finger-
nail.

F f f 2

396

Mr. cavallo's Experiments and

Promifcuous Experhnents.

Confidering what a ftrong fpark is obtained from the
metal plate belonging to Mr. volta’s machine, when
not the leaft fpark can be obtained from the eleCtric plate
itfelf, I was naturally induced to make ufe of the above
mentioned metallic plate in difcovering the electricity of
very weak eleCtrics, which otherwife would be either in-
obfervable, or fo little as not to permit its quality to be af-
certained. Accordingly, by the ufe of this plate, I obtain a
very fenlible electricity from the hairs of my legs and of
my head, or the head of almoft any other perfon, when
ftroaked.

In this manner I obtain fo ftrong fparks from the back
of a cat, a hare’s fkin, a rabbit’s fkin, a piece of paper,
or a piece of new flannel, that I can prefently charge a
coated phial with either of thofe, and fo ftrongly as to
pierce a hole through a card with its difcharge.

I have often obferved, that, when ftroaking a cat with
one hand I hold it with the other, I feel frequent fmart
pricklings on different parts of that hand which holds
the animal. In thefe circumftances very pungent fparks
may be drawn from the tips of the ears of the cat.

5 Smooth

Obfervations in Electricity. 397

Smooth glafs rubbed with a rabbit’s fkin, dry and
warm, acquires, I find, the negative electricity ; but if
the fkin is cold, the glafs is excited pofitively.

New white flannel has alfo fuch ftrong electric power,
that fometimes I have excited fmooth glafs negatively
with it.

Confidering the ftrong eleCtric power of new white
flannel, I thought that a piece of it rolled round the
globe of an electrical machine would perhaps give a
ftronger electricity on the prime conductor than the glafs
itfelf. In order to try the truth of my fuppofition, I
tied a large piece of flannel dry and warm round the
globe of the machine; and for a rubber I applied the
palm of my hand, then turned the winch, firft flowly,
and afterwards brifkly; but, contrary to my expectation,

I obferved that the electricity at the prime conductor,
although pofitive, was fo weak, that the index of your
electrometer was not moved. Surprifed at this event, I
refolved to take off the apparatus; but I was more fur-
prifed when, on removing the flannel from the globe,
the former appeared fo ftrongly pofitive, that it darted
feveral fparks to my arm and other contiguous bodies;
and the latter remained fo ftrongly negative, that your
electrometer upon the prime conductor inftantly elevated
its index to about 450. I repeated this experiment feve-

398 Mr. cavallo’s Experiments and

ral times, and the effect was always the fame. The elec-
tricity of the flannel and of the glafs, therefore, balanced
each other.

Having had occafion to coat a ten-ounce phial, I ftuck
the infide coating, which was of brafs filings, with var-
nifh, agreeable to the directions given by fome writers
on eleCtricity. This phial remained about a week unufed;
but it happened, that, whilft I was charging and dif-
charging it for fome experiments, 1 obferved that on
making a difcharge it exploded with a greater noife than
ufual, the cork with the wire being at the fame time
blown out of the neck of it. Being intent upon the main
experiments in hand, I omitted to examine the pheno-
menon of the phial. I replaced the cork on it, and went
on charging and difcharging it again; but it had not
been charged above three or four times more, when I
obferved that, on making a difcharge, the varnifh that
ftuck to the brafs filings was in a flame, which burned
the bottom and fides of the cork confiderably, and occa-
fioned a good deal of fmoke and flame to come out of
the bottle. You will recoiled, that I repeated this expe-
l'iment in the prefence of yourfelf, Mr. adams, and Mr.
Coventry, when it fucceeded perfedly ; but the varnifh
was this time fo far burnt, that the brafs filings, which

by

Qbfervalions in Ele&ricity, 399

by the combuftion had changed their colour, were almoft
all dropped to the bottom oi the phial.

I fhall conclude this paper with the defcription of a
pocket electrometer which I have lately conftruCted,
and which, on feveral accounts, feems preferable to thofe
of the moft fenlible fort now in ufe. The cafe and
handle of the electrometer is formed by a glafs tube
about three inches long, and three-tenths of an inch in
diameter; half of which is covered with fealing-wax.
From one extremity of this tube, that is, that without
fealing-wax, a fmall loop of filk. proceeds, which ferves
occalionally to hang the electrometer on a pin, 8cc. To
the other extremity of the tube, a cork is adapted, which,
being cut tapering on both ends, can fit the mouth of
the tube with either extremity. From one extremity of ’
this cork two threads proceed, a little fhorter than the
length of the tube, fufpending each a. little cone of pith
of elder. When this electrometer is to be ufed, that end
of the cork which is oppofite to the threads is pufhed
into the mouth of the tube, then the tube forms the
infulated handle of the pith electrometer, as appears in
fig. i . When the electrometer is to be carried in the
pocket, then the threads are put into the tube, and the
cork flops it, as is reprefented in fig. 2, The peculiar

advantages;

400 Mr. cavallo’s Experiments , See .
advantages of this electrometer are, its convenient fmall
iize, its great fenfibility, and its continuing longer in
good order than any other I have yet feen, as you have
yourfelf experienced To preferve this electrometer
from injury, it ihould be carried in a tooth-pick cafe, or
fome other of the like fort.

(d) I have lately conftru&ed a portable ele&rometer of another kind, which
is contrived fo as not to be affe&ed by the wind or the rain, and confequently is
very convenient to examine the ele£lricity of the cloud* out of doors in time of
thunder-ftorms : but I ftiall take another opportunity to prefent to the Royal
Society a particular defeription of the fame.

T/ii/os Trans: VoLT^VJT.Tab: VJHp.4.00.

;

L 401 I

XXI. Barometrical Obfervations on the Depth of the Mina
in the Hartz. By John Andrew de Luc, F. R, S. In
a Letter to Sir John Pringle, P. R. S.

_ 'Pimlico,

& A -ft? Feb. 8, 1777.

Read March 20, T HAVE the honour to lay before you
1777* If

JL fome obfervations on the Barometer,
which I made during my fhort journey into Germany;
and beg, if you think them worthy its attention, that
you would communicate them to the Royal Society.

I fat out with the hopes of being able to make a fhort
excurfion into the Hartz, to vifit fome of the mines there.
Thefe I knew were extremely deep; and it made me
very defirous to try in them my rules for meafuring

heights

Obfervations Barometriques fur la Profondeur des Mines du Hartz.
Par Jean Andree de Luc, Membre de la Socie'te Royale, See. dans
une Lettre au Chevalier Baronet Pringle, Pref. de la Soc. R.

MONSIEUR,

J’AI Phonneur de vous faire part de quelques obfervations du Barometre, que
j’ai faites dans un petit voyage en Allemagne; vous priant de les commu-
niquer a la Societe Royale, fi vous les trouvez dignes de fon attention.

En partant pour ce voyage, j’avois Pefperance de faire une excurfoa
dans le Hartz pour y vifiter quelques unes de fes mines. Je favois qu’elles
etoient fort profondes; et par confequent j’avois grande envie d’y eflaycr mes
Yol. LXVIE * G g g rcgUs

4oa M. de luc’s Barometrical Obfervations on
heights by the Barometer, that I might know whether
in thofe pits (where exhalations of all kinds fpread them-
felves) the condenfations of the air follow the fame laws
that they do out of them.

I nearly mifcarried in this interefting operation
through an accident which had happened to my Ba-
rometer. Having lent it to a friend, when I came to
examine it a little before my fetting out, I found that air
had fome how got into it. Luckily I had time enough
to take it to pieces and make the quickiilver boil in it; a
circumftance which I only mention in order to obferve,
that I fucceeded fo thoroughly in this manoeuvre, that,
from that time to this, the quickiilver has always ad-
hered to the fummit of the tube as often as I have raifed
it to it, juft in the fame manner as it adheres by the
ebullition. It requires a lhake to make it defcend : and

fometimea

regies pour la mefure des hauteurs par le Barometre; pour favoir dans ces
puits, ou des exhalations de tant d’efpeces fe repandent, les condenfations de
Pair fuivroient les memes loix qu’au dehors,

Je failiis a manquer cette intereflante operation par un accident arrive a mon
Barometre. Je l’avois prete; et lorfque-je Pexaminai a la veille.de mon depart,
je trouvai qu’on y avolt IaiiTe entrer de Pair. J’eus le terns heureufement de le
demonter, et d’y faire bouillir le mercure: circonftance dont je ne fais mention,
que pour ajouter; que je reuffis fi parfaitement dans cette operation, que des ce
moment, pendant tout mon voyage, et jufqu’a aujourd’hui, le mercure a .tou-
jours continue de s’attacher an fommet du tube, Iorfque je Py ramene;
comme il s’y attache au moment de Pebullition ; et il n’en defcend que par une

fecoulie*

the Depth of the Mines in the Hartz. 403
lometimes the column breaks beneath the fummit, and
there remain only fome lines of the quickfilver fuf-
.pended to the top.

It is for barometers cleared of air to this degree that
my formula have been determined : and I had the fatis-
faftion to find that they anfwered in the Hartz juft as
they had done upon the mountains in the neighbourhood
of Geneva, where they took their origin.

Another remarkable circumftance which relates to the
Barometer itfelf is as follows. Having occafion for cor-
refponding obfervations in fome places of my rout, I ap-
plied to obfervers who had good Barometers; amongft
which I met with one of Mr. dollond’s. Thefe Baro-
meters I compared with my own, being well allured
beforehand, that I Ihould find a difference in the heights
indicated, from the circumftance of their having cifterns

at

fecoufle. Quelquefois meme la colomne fe romp au deffous du fommet, et il
ne refte que quelques lignes de mercure fufpendu.

C’efl pour des Barometres purges d’air a ce point, que mes formul.es ont ete
determinees: auffi ont-elles rtuffi dans le Hartz, t ut comme dans ies mon-
tagnes des environs de Geneve, ou elles ont pris nalffance.

Void encore, Monfieur, une circonftance remarquabie, qui regarde le Baro-
nijtre meme. Ayanteu befoin en quelques endioits de raa route, d’obfervadons
correfpondentes, je m’adreflai a des amateurs, qui avoient de bons Barometres.
J’en trouvai un encr’ autres de M. dollond. Je comparai ces Barometres au
mien, etant bien alTure de trouver de la difference dans la hauteur indiquee ;
parcequ’ils avoient des refervoirs en bas; ce qui fait que la colomne barome-

G g g 2 triquc

404 Mf. de Lire’s Barometrical Obfervations on
at the bottom, which makes the barometrical column
always fhorter in thefe than it is in a plain tube in the
form of a fyphon, as I have fhewn in my treatife on the
Modifications of the Atmofphere. Accordingly this was
the cafe in all thefe Barometers; they did all hand lower
than mine, but varied from each other, according to par-
ticular circumftances, depending chiefly on the diame-
ter of the tube, and the figure of the ciftern.

In going from Hanover to the Hartz I went through
Gottingen, where I did not flop then, becaufe I wilhed
to make ufe of. the fine weather. I left it therefore with-
out having fettled any thing about correfponding obfer-
vations of the Barometer, Profeflor lichtenberg having
been kind enough to undertake the care of procuring
them for me ; the comparifon of the inftruments being
deferred till my return. Profeflor erxleben was accord-
ingly

trique y eft toujours plus courte, que dans un tuyau fimple en forme de fyphon ; .
eomme je l’ai expHque dans mon Ouvrage fur les Modifications de l' Atmofphere,
C’efl aufli ee que je trouvai dans Lous ces Barometres: ils fe tenoient tous plus
has que le mien; mais diverfement, fuivant quelques circonftances particulicres3
dependantes principalement du diametredu tube, et de la figure du refervoir.

En allant de Hanovreau Hartz, je paffai par Gottingue, ou je ne m’arretai*
point talors, parce que je youlois profiter du beau terns. J’en partis done, fans
avoir rien determine pour des obfervations -correfpondantes du Barometre; M. le
Profefleur lichtenberg ayant bierr voulu fe charger du foin de m’en procurer; et
renvoyant a mon retour la comparaifon des inftrumens. II s’adreffa pour cet effet
a M. le Profeffeur erxleben; parce qmil avoit un Barometre faitd’un fimple

tube

the Depth of the Mines in the Hartz. 405
ingly applied to by him, becaufehehad a Barometer made
of a Angle bent tube upon the principle of mine. During
my journey Mr. erxleben was fo good as to obferve this
Barometer very frequently ; and it is from his obferva-
tions that the heights of fome of the places of the Hartz,
which I lhall mention, have been determined.

At my return, I placed my Barometer near that of
Mr. erxleben ; and, when they were expofed to the fame
temperature,, there was found no difference between-
them. 4

This example, joined to all thofe with which my own
experience has furnifhed me for a long time paft, makes
me more and more folicitous that the lovers of natural
philofophy would fix the fcale of their Barometers with
citterns (very convenient ones no doubt for common ufe)
by comparing them with a Barometer made in the form

of

tube recourbe, fur la pri-ncipe du mien. M. erxleben eut la bonte d’obferver
tres frequemment ce Barometre pendant mon voyage; et c’eft d’apres fes obfer-
vations, que j’ai determine les hauteurs de quelques endroits du Hartz dontje
ferai mention.

A mon retour j’apportai mon Barometre aupres de celui M. erxleben; et
quand ils furent reduits a la meme temperature, il ne fe trouva entr’eux aucune-
difFerence. .

Cet exemple fe joignant a tous ceux que mes propres experiences nFontfourni
depuis long terns, me fait dehrer toujours davantage que les Pnyficiens veuil-
lent bien fixer l’echelle de leurs Barometres a refervoir (tres commodes fans doute
pour l’ufage ordinaire) en les comparant a un Barometre fait en forme de fiphon ;

3 ct

40 6 A/.de luc’s Barometrical Obfervations on
of a fyphon, and not by any immediate meafure com-
mencing at the level of the quickfilver in the cittern.
This is the fureft method to render exactly correfpon-
dent thofe obfervations which are made with Barometers
which one cannot compare together; at the fame time
that the barometrical height exprefled by Barometers of
this form is the only true one ; that is to fay, the only
one which, after the correction for the heat, exprefles
the weight of the air, by the height of a column of
quickfilver of a given denfity, with which it is really in
equilibrio.

I lhall begin the account of my obfervations of the
Barometer in the Hartz by thofe which I made in places,
the height of which is afcertained.

Knowing that the ore is drawn up in pales from
the pits of the mines. I thought at firft that it would

be

et non par une mefure immediate, qui parte du niveau du mercure dans le refer-
voir. C’eft le plus fur moyen de rapporter avec exactitude les unes aux autres,
des obfervations faites avec des Barometres que 1’on n’a pu comparer j en meme
terns que la hauteur barometrique exprimee par Jes Barometres de cetle forme, eft
la feule vraie; c’eft a dire la feule qui, apres la correction pour la chaleur, ex-
prime le poids de l’air par la hauteur d’une colomne de mercure de denftte
donnee, avec laquelle il eft reellement en equilibre.

Je commencerai, Monfteur, lerecit de mes ©blervations du Barometre dans le
Hartz, par celies que j’ai faites en des lieux dont la hauteur eft connue.

Sachant que l’on monte le mineral dans des feaux, par les puits des mines,
j’ayois cru d’abord qu’ii me feroit pofftbje d.e mefurer ces profondeurs aucordeau;

et

X

the Depth of the Mines in the Hartz. 407
be eafy to meafure their depths with a line, and I had
accordingly provided myfelf with all the neceffary im-
plements for that purpofe ; but when I arrived at Clauf-
thal, the principal place of the King’s mines, I found that
thofe pits, being dug in the direction of the veins of ore,
are too inclined to make fuch a mode of menfuration
practicable.

At firft this gave me great concern, becaufe I had
my experiments much at heart; but I was foon made
eafy by Baron reden, captain-general of the mines.
“ You do not want thefe meafures,” faid he, “ fince it is
“ of much more confequence to us, than it can poffibly
** be to you, to know exabtly the depth of all the points
H of thefe mines. Without fuch knowledge, how could
“ we direct ourfelves in boring from one to the other ?”
This confideration did in fadt difpel all the fcruples
which had made me delirous of meafuring the depths

myfelf,

et je m’etois muni des chofes necelfaires a cet effet. Mais lorfque je fus arrived
Claufthal, chef lieu des mines du Roi, j'appris que ces puits, creufes dans la
dire&ion des filons, font trop inclines pour que cette efpece de mefure foit
poflible. J’y eus d’abord beaucoup de regret; parce que j’avois fort a coeur
ces experiences : mais M. le Baron de reden, capitaine-general des mines, me
tranquillifa bientot, a Vous n’avez pas befoin de mefurer,? me dit-il, “ il nous
importe bien plus qu’a vous de connoitre exa&ement la profondeur de tons
iC les points de ces mines. Sans cela, comment nous dirigerions-nous, pour
percer de Tune a Tautre?” Cette confideration en efFer, fit difparoitre pleine-

ment

40S M. de luc’s Barometrical Obfervations on
myfelf, and by fo doing gave me time for a greater num-
ber of obfervations.

The firft of this kind were made in three mines in the
^environs of Claufthal; called the Dorothea, the Caroline,
and the Benedict. Mr. de reden andMeff. HELZENER and
Friedrich, chief officers of the miners, went down with
me; and, whillt we were penetrating into the bowels of
the mountain, Mr. leyser, fyndic of the mines, and a
lover of meteorological obfervations, was obferving every
quarter of an hour, at the top of the pit into which we
had defcended, a barometer and thermometer which
have been fince compared with mine.

I had obferved my Barometer at the mouth of the
Dorothea pit when we were going into the mine at
half an hour after eleven in the morning; I obferved it

at

ment les fcrupules qui m’avoient fait deiirer de mefurer moi-meme ces pro-
fondeurs; ce qui me facilita un plus grand nombre d’obfervations.

Les premieres de ce genre furent dans trois mines contigues des environs de
Claufthal; nomme.es la Dorothee, la Caroline, etla Benedi&e. M. de reden
et MeiT. helzener et friedrich, premiers officiers des mineurs, fedonnerent
la peine d’y defcendre avec moi: et tandis que nous nous enfoncions dans le fein
de la montagne, M. leyser, iindic des mines, et amateur des obfervations
ineteorologiques, obferva de quart d’heure en quart d’heure, au haut du puits
par lequel nous etions defcendus, un barometre et un thermometre, qui furent
depuis compares aux miens,

J’avois obferve mon Barometre en entrant dans les mines a u| h. du matin*
au haut du puits de la Dorothee; je l’obfervai au fond de ce puits a h.; au

fond

f^e Depth of the -Mhus jn. the. \\ artz. 409 -

at the bottom of this pit at a quarter paft one o’clock; \
at the bottom of the Caroline, at a quarter paft three
o’clock ; in the loweft fearching gallery of the Benedict,
at fix o’clock ; and again, at the mouth of the Dorothy, .
on our return, at feven o’clock. During the feyen hours
and a half that we had ft aid in the mines, the greateft
variation of the Barometer had not exceeded a quarter of-
a line ; and Mr. leyser’s obfervations indicated the times •
when this variation had taken place.

At my return 1 calculated thefe obfervations, and gave
the refults to Baron reden, in order that the fubter-
raneous Geometer might compare them with the regifters
which are kept of the depths of all thefe mines. The
following are the refults of thefe calculations, the parti-
culars of which I likewife fend you.

The

fond de celui de la Caroline a 3! h.; dans la galerie de recherche la plus balfe
de la Benedi£te a 6 h. ; et enfin je robfervai encore a 7 h, etant de retour a
Psntree du puits de la Dorothee. Pendant les 7I h. que nous etions relies dans
les mines, fa plus grande variation avoit ete d* | ligne; et les obfervations de
M. leyser me marquoient les terns ou cette variation s'ctoit faite.

Au retour je caiculai ces obfervations, et j’en remis les refultats a M. le Baron
DE reden, pour les faire comparer par le Geometre fouterrain, avec les regitres
tenus de toutes les profondeurs dans les mines. Voici, Monlieur, les reiultst;
de ces calculs, dont j’ai 1’honneur devous envoyer aufE les details.

Vol. LXVII.

H h k

-r *

410 M. de luc’s Barometrical Obfervations on

French toifet*

The depth of the Dorothy pit between two'
fixed points,

That of the Caroline, relatively to the fame]
point at the mouth,

That of the lowed; fearching gallery of the'l
Benedict, relatively to the fame point,

168,96

170,74

I43>96

Mr. Friedrich was appointed to give me the geome-
trical meafures. He had been prefent at my obferva-
tions, and found the refults of them fo near thofe mea-
fures, confidering they had been furnifhed by a method
fo eafy, and according to his notions fo extraordinary,
that he gave me a certificate in due form of the real
heights, which are as follows :

The

Toifes de Fn

La profondeur du puits de la Dorothee, entre deux points fixes, 168,96

Celle du puits de la Caroline, relativement au raeme point d’enhaut, 170,74

Celle de la galerie de recherche la plus profonde de la Benedi&e, de meme, 143,96

Ge fut M. Friedrich, qui fut charge de me communiquer Ies mefures geo-
metriques. II avoit ete temoin des obfervations; et il en trouva les refultats ft
pres de ces mefures, pour avoir ete founds par une route ft aifee et ft ftnguliere
a fes yeux, qa’il m’expedia un certiftcat en dues formes de ces hauteurs reelles ::
•lies etoient comme fuiti

U

4i i

Lachter**

172*31

173*92

144*79

I could not at firft judge of the agreement of the two
meafures, becaufe it was neceffary to know the relation
between theLachter and the French Toife. Ihad brought
with me a very accurate half Toife, which we compared
with the half Lachter, and found the latter fhorter than
the former in the proportion of 61 to 62.

Reducing then, according to this proportion, the geo-
metrical meafures above mentioned into French toifes,
we ftiall have,

The

Lachters, ou toifes
du Hartz.

Le puits de la Dorothee en partant des points des obfervations, — I72>31

Celui de la Caroline, — — — * I73?92

La galerie de la Benedi&e, — — — *44>79

Je ne pus pas juger d’abord du rapport des deux mefures, parcequ’il falloit
connoitre celui de la Lachter avec la Toife de France. J’avois apporte avec moi
une demi Toife fort exa&e ; nous la comparames a la demi Lachter, et nous trou-
vames celle-ci plus courte que la demi Toife dans le rapport de 61 a 62.

En reduifant done fuivant ce rapport, les mefures geometriques ci-defius en
Toifes de France, nous aurons:

the Depth of the Mines in the Hartz,

The depth of the Dorothy, from the points'
of obfervation, J

That of the Caroline,

The gallery of the Benedict,

H h h a

Le

412 M. de luc’s Barometrical Obfervations on

French toifes.

The pit of the Dorothy, 1 69,53

That of the Caroline, 171,12

The gallery of the Benedict, 142,42

The geometrical meafures come then very near tfi4
i barometrical ones, for they only differ by

Toifes.

In the firft obfervation, 0,57 fhort.

In the fecond, 0,38 ihort.

In the third, 1,54 excefs,

I was really furprized to have come fo near to the
geometrical meafures (which, as I fhall have occafion to
mention hereafter, may be looked upon as the real
heights) for I had imagined, that the exhalations of all

kinds

Toifes de Fr.

Le puits de-la Dorothee,
Celui de la Caroline,

La galerie de la Benedi£le,

171,12

142,42

Les mefures geometriques s’approchent alors de bien pres des mefures baro-
metriques y puifque celles-ci different feulement des autres favoir :

T oife.

Dans la premiere obfervation de, 0,57 en defaut.

Dans la feconde de, 0,38 auffi en defaut.

Dans la troifleme de, 1,54 en exces.

Je fus reellement furpris d’avoir approehe de fi pres des mefures geometriques;
- qui, comme j’aurai occafion de le dire enfuite, peuvent etre regardees comine
«4ee hauteurs reelles. Car j’avois imagine, que les exhalaifons de toute efpece

qui

the Depth of the Mines in the Hartz. 413
kinds in the mines muft in' feme meafure affeft the com-
mon laws of the air’s elafticity in different degrees of
heat, if not its abfolute elafticity. On re fteflingy however,
on this lingular conformity of the air in mines with the
external air, I foon found the caufe of it in the extreme
care taken to procure a circulation of external air in the
mines, in order to prevent the pernicious effects of the
exhalations: fo that the fame means, which really pre-
serve the health of the miners in their fubterraneous
abodes, give the air which circulates in them, and more
efpecially that of the pits in which are the principal
currents, the properties of the external air as to baro-
metrical meafurements. Doubtlefs this is the caufe of
that interefting phenomenon, as fatisfadlory for the fe-
curity it gives to the lives of the miners, as for the ap-
plication of the laws of aerometry: this was again con-
firmed by obfervations I made fome days after in other

mines,

yqui fe repandent dans les mines, devoient y alterer les loix communes de l’elafti-
cite de Fair en differens degres de chaleur; et peut-etre fon elafiicite abfoluec
Mais en reflechiflant enfnite fur cette linguliere conformite de Fair des mines.,
avec Fair exterieur, j’en apper^us la caufe dans le foin extreme qu’on prend d'y
faire circuler Fair exterieur, pour empecher les mauvais effets des exhalaifons0
Ainu les memes moyens qui confervent reellement la fante des mineurs dans
leurs demeures fouterraines, donnent a Fair qui y circule, et furtout dans les
puits, ou font les principaux courants, les proprietes de Fair exterieur dans les
mefures barometriques. C’eft la fans doute la caufe de cet interelfant pheno-
> inene, aulli tranquillifant fur le fort des mineurs, que fur Fapplication des regle-s
d’aerometrie, Ce qui fe confirme encore par d’autres obfefvations que je fis

\ .quelques

414 de luc’s Barometrical Obfervations on
mines, where indeed I met with fome irregularities, but
not fuch as might have been expedled from barely con-
fidering the local circumftances.

Thefe mines are in the Ramelfberg near Goflar. The
ore that is chiefly extracted from them, as well as from
thofe of Claufthal, is lead ; but they are worked in ano-
ther manner. The vein of ore, which is near eighteen toifes
broad, is extremely impregnated with pyrites: infomuch
that, when you heat it, the vapour of the fulphur, which
difengages itfelf, burfts the ftone, which falls down in
large fragments. The method then is to light great fires
againft the rock; and, when they are extinguilhed, the
miners aflift with their inftruments the fall of the ftones,
that may ft ill remain fufpended.

Sulphureous vapours, therefore, conftantly difengaged
from the heated ore, circulate in the caverns of the

mountain,

quelques jours apres dans d’autres mines, ou jc trouvai quelque irregularite, mais
non point fuivant ce que les circonftances locales fembloient devoir en produire.

Ces mines font dans le Ramelfberg, pres de Goilar. Elies fourniflent prin-
cipalement du plomb, comme celles de Claufthal ; mais on les exploite d’une
autre maniere. Le filon, qui a pres de 18 toifes de largeur, eft extremement
penetre de pyrite; tellement qu’en PechaufFant, les vapeurs du fouffre qui fe
degage, font crevafterla pierre, qui tombe d’elle-meme en grand lainbeaux. On
allumedonc de grand feux contre lerocher; et lorfqu’ils fonteteints, lesmineurs
aident avec des inftrumens, la chute des pierres qui font encore lufpendues.

II fe detache done prefque conftamment du mineral echauffe, des vapeurs ful-
fureufes, qui circuient dans les cavernes de la montagne, et dans les puits et

foupiraviH

the Depth of the Mines in the Hartz. 415
mountain, and in the vents and pits by which they com-
municate with eachother. The day I entered them, was a
day of reft for the miners ; and there was no other fire but
that which Mr. roeder, their principal, was kind enough
to order to be lighted, that I might form an idea of this
method of working mines. Notwithftanding this, I could
perceive here and there fulphureous vapours, which in
fome places were even ftrong enough to occafion a very
troublefome fenfation of fuffocation. In fome places I
felt the remainder of the heat communicated to the rock
from whence thefe vapours were exhaled; and in fome
caverns, where the fire had only been put out the even-
ing before, Fahrenheit’s thermometer rofe to r 1 o°. But
this very heat is a moft powerful ventilator, as it makes,
the external air circulate in thefe mines. Indeed the cur-
rents of air are fo rapid in them, that one is obliged to

have

foupiraux par iefquels ces cavernes communiquent les unes aux autres. Le jour
que j’y entrai etant un jour de repos pour les mineurs, il n’y eut de feu dans les-
mines, que celui que. Mr. roeder leur chef eut l’honnetete de faire allumer
pour me donner une idee de cette exploitation. Cependant j’apper^evois £a et;
la des vapeurs de fouffre; etfouvent merae elles etoient aflez fortes, pour m’oc-
cafioner un fentiment de fuffocation tres penible^ Quelquefois aufli j’eprou-
vois les reftes de la chaleur communiquee au rocher d’ou ces vapeurs s’exha-
loient : et dans quelques cavernes ou le feu n’etoit eteint que des la veille, le ther-
mometre de Fahrenheit, monta jufqu’a iio°: mais cette chaleur meme ell
un ventillateur tres puiffant, pour faire circuler Fair exterieur dans ces- mines*
Auili les courants d’air y font-ils ii rapides, qu’on ell oblige d’avoir des portes a
5 I’entree

4 i 6 M. -de luc’s Barometrical Obfervations on

■ t - r ^ ~ * r r ** r ••• .

Rave doors at the entrance of each gallery, and fome-
times many of them one after an other, without which it
would not be poflible to keep any lamps lighted in
thefe fubtdrraneous regions.

It is probably to this conftant renewal of the air, that
the miners of Ramelfberg are- indebted for the good
health they enjoy, notwithffcanding the prodigious heat
they feel while they are at work, and the quantity of ful-
phur which exhales ;from every part; and it is likewife
probably from this caufe that my barometrical obferva-
tions gave me the heights more exactly than I could
have expected from thefe circumftances. The following
are the refults of thefe obfervations, the particulars of
which you likewife have fubjoined.

Height

I’entree de toutes les galeries; et quelquefois meme plufleurs de fuite; fans quoi
il ne feroit pas poflible de tenir les lampes allumees dans ces fouterrains.

C’eft fans doute a ce renouvellement continuel de Pair, que les mineurs du
Ramelfberg doivent la bonne fante dont ils jouiflent, malgre la chaleur prodi-
gieufe qu’ils eprouvent pendant le terns de leur travail, et la quantite de fouffre
qui s’exhale de toute part: et c’efl: aufli probablement la caufe, de ce que mes
obfervations du Barometre, me donnerent les hauteurs, plus exa<Aement que je
ne l’attendois d’apres ces circonftances. Void, Monfleur, les refultats de ces
obfervations, dont vous avez aufli les details ci-joint.

Hauteur

the Depth of the Mines in the Hartz. 417

French toifest

Height of the gallery of Breitling, above the ]
bottom of the pit of Kaunkuhl,

Height of the entry of the mines, above the j
gallery of Breitling,

Height of the top of the pit of Kaunkuhl,'
above the entry of the mines, by external >
obfervations,

44*4*

27>04

41*27

Depth of the pit of Kaunkuhl, meafured in
three parts, one of them without the mines,

* 112,72

Depth of the fame pit, determined by imme-'
diate obfervations made at the top and the *
bottom,

H3*i3

I could not get the geometrical meafures the fame
day, becaufe there wras not time enough left to look for

them

Toif. de Fr*

Hauteur de la galerie de Breitling, fur le fond de puits de Kaunkiihl, 44,41

Hauteur de l’entreedes mines, fur la galerie de Breitling, 27,04

Hauteur du haut du puits de Kaunkuhl, fur l’entree des mines, par des 1

s 4 1 , 2 7

obfervations exterieures, 1

Profondeur du puits de Kaunkuhl, rnefure en trois portions, dont une
a l’exterieur des mines,

Profondeur du meme puits, determinee par des obfervations imme-
-diates, au fond et au haut,

Je ne pus pas avoir d’abord lesmefures geometriques; parce qu’il ne refta pas
You LXYIL lii alfez

)

1 1 3?1 3

j 112,72

4i 8 M. de luc’s Barometrical Obfervations on
them then. But the day after Mr. roeder fent them to
Mr. de usler, Comptroller of the treafure, who had been
kind enough to accompany me to Ramelfberg, and in
all my fubterraneous rambles. Mr. roeder likewife
came with us; he took notes of the places where the
obfervations were made, and fent the following mea-
fures, which I have reduced into French toifes.

French toifes. .

Height of the gallery of Breitling, above the
bottom of the pit of Kaunkuhl,

Height of the entry into the mines, above the
gallery of Breitling,

Height of the top of the pit of Kaunkuhl,
above the entry of the mines,

' ’ f

) i i ; > , i ; r v Jwi*

1 13>94
Hence

affez de terns pour les chercher le meme jour. Mais des le lendemain M.
roeder les envoya a M. de usler, Controleur du trefor, qui avoit eu la
bonte de me conduire au Ramelfberg et dans toute ma route fouterraine. M.
roeder nousy avoit accompagnes; il avoit pris note des lieux ou s’etoient faites
les obferva* ions; et il envoya les mefures ci-apres, que j’ai feulement changees
en Toiles de France.

Hauteur ds la galerie de Breitling, fur le fond du puits de Kaunkuhl, 46,86
Hauteur de l’entree des Mines fur la galerie de Breitling,

Hauteur du hautdu puits de Kaunkuhl fur Pentree des mines, 4I,32

I 46,86

J 25*76
| 41*32

113*94

n

the Depth of the Mines in the Hartz. 4x9
Hence it follows, that in the meafurement of the
total height of the pit, the barometrical meafure dif-
fered from the geometrical one by 0,81 toife, or about
~ in defeat; that in the meafurement of a part only of
this height, made without the mine, it differed only
by 0,05, or about—, likewife in defeat ; but that in the
two other portions of the height, taken within the mine,
it differed in the one by — in defeat, and in the other
by f in exeefs : and hence we obferve, that the ab-
folute errors are only of toifes and toife; and that
thefe fmall differences may have arifen from fome fault
in the obfervation, as well in fmall heights as in greater
ones: and in this cafe, where the errors are in defeat
and exeefs, it is probable that they arife from fome fuch
caufe; and that the fulphureous vapours have little or
nothing to do with them.

Having

11 refulte de la, que fur la hauteur totale du puits, la mefure barometrique a
differe de la mefure geometrique, de o,8 1 toife, foit d’environ tto, en defaut ;
que dans la mefure d’une partie de cette hauteur, faite en dehors des mines,
elle n’a differe que de 0,05, foit d’environ jis, auffi en defaut: mais que dans
les deux autres portions de la hauteur, prife fans l’interieur de la mine, elle a
differe dans l’une d’T’¥ en defaut, et dans Pautre d’ ti en exces. Sur quoi il
faut remarquerj que les erreurs abfolues ne font que de i\ toifes, etd’ 1 \ toife;
et que ces petites differences peuvent refulter de quelque defaut dans l’oblervation,
auffi bien fur de petites, que fur de grandes hauteurs. Et dans ce cas-ci, ou
les erreurs font en exces et en defaut, il eft bien probable qu’elles tiennent a ce'a,
et que les vapeurs fulfureufes n’y entrent pour rien de fenfible.

I i i 2 Apr.s

4ao M. de luc’s Barometrical Obfervations on

Having made thefe experiments within the mines, I
was defirous of making fome in the open air, which I
had foon a very agreeable opportunity of doing; for
having communicated my defire to Mr. reden, he and
Mr. rausch, the principal of the fubterraneous geome-
ters, were fo good as to be of the party. The latter had
had occafion to determine moft accurately the height of
two external points of the Hartz, relatively to the mines
of Claufthal and Zellerfeld. Nothing more, therefore,
was required but to obferve the Barometer at the entry
of a certain mine, which was a fixed point, and to
obferve it again at thefe two external points; one of
which was about 3000 toifes horizontal diftance, beyond
a fmall hill; and the other, 5000 toifes off, entirely
without the Hartz.

We

Apres avoir fait ces experiences dans Tinterieur des mines, je defirois beaucoup
d’en faire aufti en plein air. L’ayant temoigne a M. i>e reden, il m’en fournit
un moyen tres agreable ; car lui meme, et M. rausch chef des geometres fou-
terrains, furent de la partie.. Ce dernier avoit eu befoin, a Toccafion d’un projet
de galerie d’ecoulement, de determiner avec la pl-us grande exa&itude la hauteur
de deux points exterieurs au Hartz, relativement aux mines de Claufthal et de
Zellerfeld. II ne s’agiftoit done que de faire l’obfervation du Barometre a l’entree
d’une certaine mine, qui etoit un point fixe ; et de Taller faire enfuite a ces deux
points exterieurs; dont Tun etoit a environ 3000 toifes de diftance horizontal,
au de la d’une eolline, et l’autre a 5000, toifes, entierement au dehors du
Ha.tz,

5

Nous

the Depth of the Mines in the Hartz. 421
We carried this project into execution on the 30th of
October, when I found the following heights by the
calculations hereunto annexed-

French toifes,.

Height of the entry of the mine, called Alte"

Seegen, above a certain point in the valley > 102,18
of Bremeke,

Height of the entry of the fame mine, above'

another point near Lasfelde, in the valley * 173,81
of Olierode,

After I had calculated thefe obfervations, Mr. rausch
was fo good as to give me a profile of our rout, on which
the points above mentioned were marked. Their heights,
reduced to French toifes, are as follow :

The

Nous executames ce projet le 30 O&obre; et je trouvai les hauteurs fuivantee
par les calculs ci joints de nies obfervations,

Toifes de Fre

Hauteur de l’entree de famine, nominee Alte Seegen, au delfus d’unT IQ2
certain point dans la vallee de Bremeke, J

Hauteur de la meme entree de mine, au delfus d’un autre point presl m
de Lasfelde, dans la vallee d’Ofterode, J

Apres que j’eus calcule ces obfervations, M. rausch eut la bonte de me
donner un profil de la route que nous venions de faire, ou les points ci-delfus
etoient marques. Leur hauteur, reduite en Toifes de France, eft comme fuit^

Le

42 1 M. de luc’s Barometrical Obfervations on

100,85

That of the vale of Oft erode, 173,56

Confequently, one of thefe barometrical meafures,
taken in open air, was found to agree very nearly with
the geometrical meafure ; and the other differs only ij
toife in excefs.

The only thing that remained to be enquired into was,
whether the geometrical meafures could really be relied
on; but I foon found that I might truft to the impor-
tance they were of to the miners, as well as to the daily
experience of the truth of them; although they be
made in fo very Angular a manner, that one does ftand
in need of this experience, to be perfuaded of their
exaftnefs.

A twifted

Le point de'la vallee de Bremeke, au deffous d’Alte Seegen, 100,85

Celui de la vallee d’Ofterode, 1 73» 5^

Ainli, Tune de ces mefures barometriques fakes en plein air, s’eft trouvec
prefqu’ entierement femblable a la mefure geometrique; l’autre n’en difFere que
d’une toife et un tier en exces.

II ne s’agilToit plus que d’examiner, li les mefures geometriques etoient vrai-
ment dignes de confiance. Mais je vis bientot, que je pouvois me repofer a cet
egard fur l’importance dont il eft pour les mineurs qu’elles le foyent; et fur
1’experience qui les verifie tous les jours. Cependant elles s’executent d’une
maniere ft finguliere, qu’il faut reellement cette experience, pour fe perfuader
qu’elles font exa&es.

The point of the valley of Bremeke below Alte
Seegen,

the Depth of the Mines in the Hartz. 423
A twilled brafs wire five toifes long, two puncheons,
a femi-circle, and a compafs, are all the inftruments made
rife of by the fubterraneous Geometer.. By means of his
two puncheons, he extends his wire in the direction of the
way which he is meafuring : and by practice he acquires
a habit of always llretching it to the fame degree. His fe-
mi-cirele, which is very light, being fufpended at the mid-
dle of the wire, fhews him its inclination. By this means
he has a right-angled triangle, of which the hypothenufe
and angle at the bafe are known. He has confequently
the vertical height and horizontal diftance gone over.
After this he fufpends his compafs to the wire, in order
to find out its declination, and confequently the direction
of his horizontal line. It is in this manner that, he draws
the plan and fedlion of thefe fubterraneous labyrinths. It
is likewife by this means that he goes over hills and vales,

in;.

Un fil de leton tordu de 5 toifes, deux poin£ons,un demi-cercle, et vine boufible,
font tous les inftrumens du Geometre fouterrain. II etend fon fil, par ]e moyen
de fes deux poin^ons, dans la dire&ion du trajet qu’il mefure; l’habitude le lui
fait tendre toujours au merne degre. Son demi-cercle, qui eft fort leger, etant
fufpendu au milieu de ce fil, lui en montre I’inclinaifon; il a par ce moyen un
triangle re&angle, dont l’hypothenufe et d’angle fur la bafe iui font connus :
il a done la hauteur verticale et la diftance horizontale parcourues. . II fufpend
enfuite .fa bouffole au meme fil, pour en connoitre la declinaifon, et par confe-
quent la dire£lion de fa ligne horizontale. C’eft ainft qu’il tire le plan et la
coupe de ces labyrinthes fouterrains : et c’eft ainft encore qu’il va chercher au
3 dehors •

424 M. de luc’s Barometrical Obfervatiom on
in order to determine points correfponding to his pits
and galleries.

But is this a method that may fafely be depended
upon ? The fail anfwers, and faves us the trouble of long
reafonings. A miner, i'olely upon the faith of his Geo-
meter, and in the abfolute obfcurity of the entrails of
the earth, undertakes a labour that is to coft him years,
in daily boring through a rock. Another miner fets out
to meet him from fome other mine, or from without. At
the end of a determined meafure, the Gnomes begin to
hear each other, and at length they meet. I have ob-
ferved fome of thefe points of rencounter in the galle-
ries ; it is fometimes difficult to perceive the fmall wind-
ing which has been neceflary for their meeting end to
.end.

It

dehors, a travers les vallees et les collines, des points correfpondants a fes gale-
ries et a fes puits.

Eft-ce done la une methode dans laquelle ou purffe vraiment prendre con-
fiance? Le fait parle ici, et epargne les raifonnemens. Le mineur, fur la foy
de fon Geometre, s’avanture a entreprendre, dans l’abfolue nuit des entrailles de
la terre, un travail qui lui coutera des annees, en per^ant journellement le
rocher. On vient a fa rencontre, de quelqu’autre mine, ou du dehors. Aulxmt
de la mefure determinee, nos Gnomes viennerft a s’entendre; et enfrn iris fetrou-
vent. J’ai vu plulieurs de ces points de rencontre dans les galeries; on a peine
qtfelquefois a apper^evoir le petit evafement qu’il a fallu faire, pour qu’elles fe
joignent bout a bout.

II

the Depth of the Mines in the Hartz. 425
It remains, sir, that I communicate to you fome other
barometrical obfervations, not verified by geometrical
furvey ; by which I have determined the height of fome
points of the Hartz relatively to the plain, and chiefly ^
the higheft point.

This greatefi: elevation, called the Blocklberg or
Brocken, is fituated in the eftate of Count de vernigue-
rode. It was my firft excurfion on my arrival at the
Hartz, and I made it in the company of Mr. redem.
We fat out from Claufthal at ten o’clock, and arrived at
Oder-bruck, a hamlet fituated at the foot of the Brocken,
at half an hour after two in the morning. We intended
fetting out at day -break, in order to reach the top of the
mountain by fun-rife, becaufe that is the moll favourable
moment for feeing the great extent of country, which is
difcoverable from this eminence ; the vapours, which by
degrees tarnifli the picture, not having yet rifen. O11

this

II me refle a vous communiquer, Monfieur, d’autres mefures barometriques,
non verifiees, par lefqu’elles j’ai determine la hauteur de quelques points du
Hartz relativement a la plaine, et principalement le plus haut point.

Cette fommite la plus elevee, nommee le Blockfberg ou Brocken* eft fituee
dans les terres de M. le Comte de verniguerode. Cet fut ma premiere courfe
lorfque j’arrivai au Hartz; et M. le Baron de reden la fit deja avec moi. Nous
partimes a 10 h. du foir de Claufthaul, et nous arrivames a 2§ h. du matin a
Oder-brucke, hameau fitue aupied du Brocken. Notre intention etoit de nous
mettre en marche a la pointe du jour, pour arriver au lever du foleil au fommet
de la montagne; parceque c’eft le moment le plus favorable pour voir Timmenfe
pays que Ton decouvre de cette hauteur: les vapeurs qui peu a peu ternilTent le
o l . LXVII. ' K k k tableau,

42,6 M. de luc’s Barometrical Obfervations on
this occafion, however, other vapours rendered our noc-
turnal courfe ineffectual. Clouds refted on the top of
the mountain, and we hefitated a long time whether or
not we Ihould put off the party to another day. At length
a ray of hope having broke forth at Oder-brucke, we de-
termined to let out for the mountain. It was then nine
o’clock in the morning, and, had we had fair weather, an
hour would have been fufficient to have carried us to the
top ; but the clouds growing thicker and thicker, we loll
our way, notwithstanding we had guides ; and, had it not
been for a map and compafs which M. de reden had
provided himfelf with, we fhould not probably have ar-
rived at the top of the Brocken that day, having been for
fome hours wandering round it, without drawing nearer
to it. We did at length reach it at noon, being ourfelves
as well as the mountain covered with ificles. The wind

was

tableau, n’etant pas encore elevees. Mais d’autres vapeurs rendirent inutile
notre courfe de nuit: les nuages s’emparerent du haut des montagnes; et long-
tems nous hefitames li nous ne renverrions pas la partie a un autre jour. Mais
entin un rayon d’efperance ayant lu;t a Oder-brucke, nous nous derermi names a
partir pour la montagne. II etoit 9 h.du matin ; etuneheure eut fuff t pour nous
rendre au fommet, fi nous avions eu beau terns. Mais les nua-es s’etant epaiflis
toujours d’avantage, nous nous egarames malgre nos guides; et fans une boulfole
et une carte de ces montagnes dont M’. de reden avoit eu la precaution de fe
munir, nous ne ferions peut-etre pas arrives de tout le jour au Brocken, autour
duquel nous tournions, fans le trouver. II etoit midy lorfqu’enfm nous l’attei-
gnimes; etant nous memes couvers de verglas, corame toute la montagne. II

faifoit

the Depth of the Mines in the Hartz. 427
was very high, the thermometer Hood at 3 1 \ of fahren~
heit; and the clouds, chafed by the wind, covered every
thing with a cruft of ice that formed itfelf perceptibly to
the eye.

I had taken with me a new hygrometer, conftrufted
upon the principles of that I had the honour to prefent
to the Royal Society four years ago, but corrected in many
things where experience had taught me better. I was in
hopes, by taking it to the Hartz, of being able to repeat the
experiment of the great drynefs of the fuperior regions
of the air, which I had made formerly on the Alps ; but
it happened quite otherwife, and I was not forry for the
contrail. Being arrived at the top of the Brocken, I fuf-
pended my hygrometer on the outlide of a fmall hut,
which M. de verniguerode has had the humanity
to ere£l for the benefit of fuch obfervers as Ihould

come

faifoit un vent afTez fort, le thermometre etoit a Fahrenheit; et les

nuages charies par le vent, couvroient tout d’une croute de glace, qui fe formoit
a vue d’oeil.

J’avois porte avec moi un nouvel hygrometre, conftrult fur les principes de
celui que j’ai eu l’honneur de prefenter a la Societe Royale il y a quatre ans;
mais ou j’ai corrige pluheurs des defauts que l’experience m’a deja fait decouvrir
dans ma premiere tentative, j’efperois en le portant au Hartz, de repfter 1’ ex-
perience de grande fechereffe des couches fuperieures de i’air, que j’avois faite ci
devant fur l’une des fommites des Alpes. Mais il en arriva tout autrement: et
je ne fus pas fache du contrafte. Arrives done enfin au fommet du Brocken, je
fufpendis mon hygrometre au dehors d’une petite hute, que M. de vernigue-
rode a eu l’humanite de faire batir pour fervir de refuge aux curieux dans le

Kkk 2 niauvais

428 M. de luc’s Barometrical Obfervations on
come there in bad weather. In an inftant the ivory, of
which this new inftrument as well as the former is con-
ftrudted, was covered with ificles ; and what merits fome
attention as to the matter of the humor , the hygrometer
was by that means brought very nearly down to the
point of extreme humidity.

I ffiall not here detain you with accounts of feveral
other obfervations made with this inftrument in the
courfe of my journey. I am much better pleafed with it
than with the firft, for many reafons ; however, I have
not got over all the difficulties, but luckily alfo I have not
exhaufted all the refources.

I likewife obferved the Barometer on this eminence ;

I had done it at fetting out from Oder-brucke, and did it
again on my return. I had likewife correfponding obfer-
vations at Claufthal,and during the whole of my journey

I had

mauvais terns. En un inftant Eyvoire, dont ce nouvel inftrument eft fait
coniine le premier, fut couvert d’une couche de verglas; et ce qui merite quel-
que attention dans la matiere de /’ humor , l’hygrometre fut reduit par la a tres
peu pres au point de Phumidite extreme.

Je ne m’arraterai pas ici fur quelques autres obfervations que j’ai faites avec
cet inftrument pendant mon voyage* J’en ai ete plus content que du premier a
divers egards. Cependantje ne fuis pas au bout des difficulties : mais heureufe-
ment non plus, je ne fuis pas au bout des refources*

Je fis auffi Pobfervation du barometre fur cette hauteur. Je l’avois faite en
partant d’Oder-brucke, et je la fis au retour. J’avois auffi des obfervations cor-
relpondantes a Claufthal : i’en eus pendant tout mon voyage de journailleres, a

c Claufthaij

the Depth of the Mines in the Hartz. 429
I had daily ones regiftered at Claufthal, at Gottingen, and
at Hanover. From all theft obfervations I computed the
height of Oder-brucke above all the above-mentioned
places, by calculations which I have annexed.

French toifes*

The fmall hut, at the fummit of the Brocken]

above Oder-brucke, j I72)93

Oder-brucke above Claufthal, 91,39

Claufthal above Gottingen by 17 obfervations'
correfponding as to time, between Profeflor
erxleben and myfelf,

Gottingen above Hanover by 1 6 fimilar obfer-
vations, between Mr. erxleben and M. de

HINUBER,

i

2 TO, 2 I

56,4S

Total elevation of the Brocken above Hanover, 530,98

It

Claufthal, a Gottingue, et a Hanovre. De toutes ces obfervations j’ai conclu
la hauteur da Brocken furtous les lieux ci-deftus, par. les calculs ci-joints, dont
voici l’extrait*

Toifes de Fr*

La maifonetie au fonimet du Brocken, fur Oder-brucke, 1 72,93

Oder brucke fur Claufthal, 91,39

Claufthal fur Gottingue, par 17 obfervations correfpondantes pour 3e
terns, entre M. le Profefteur erxleben et moi,

Gottingue fur Hanovre, par 16 femblables obfervations entre M.

ERXLEBEN et M. DE HINUBER,

n

j 210,
1 56,

21

Hauteur totale du Brocken fur Hanoyre*

53°;98

k

430 M. de luc’s Barometrical Obfervations on

It will be eafy to come at the elevation of Hanover
above the level of the fea, in order to compleat this mea-
furement: correfponding obfervations of the Barome-
ter will be fufficient for that purpofe. In the mean time
it is eafy to eftimate either by the Barometer itfelf (the
mean height of which during the month of October was
30,1 Englifh inches on afecond floor) or by the fmall decli-
vity of the rivers between Hanover and the fea, that the ele-
vation of Hanover above that level is not very confiderable.

Such, sir, are the meft interefting obfervations of this
kind which I have been able to make in the Hartz. It
appears to me, that they are of a nature that fhould en-
courage us to examine more and more into the phyfical
principles on which they depend : principles, the exten-
five confequences of which promife new fteps in our
inveftigation of nature, not only upon our globe but alfo
in the heavens.

A Be-

II fera aife de favoir la hauteur de Hanovre fur le niveau de la mer, pour
ccmpletter cette mefure. Des obfervations correfpondantes du barometre, fuffi-
ront pour cela. Mais en-, attendant, il.jeft.. aife de juger, foit par le barometre lui
meme, dont la hauteur moyenne le matin, pendant le mois d’O&obre, fut 30,1
pouces Anglois a un feconde etage-; foit par le peu de pente des rivieres jufques a
la mer; que l’elevation de Hanovre au delfus defon niveau n’eft pas bien grande.

Voila, monfieur, les obfervations les plus interelfantes de ce genre, que j’aie '
faites dans le Hartz. II me femble qu’elles font propres a donner le courage
d’examiner de plus pres tous les principes phyhques fur lefquels elles fe fondent;
principes, dont les confequences tres etetidues, nous promettent de nouveaux
pas dans l’etude de la nature, non feulement fur la terre, mais dans le ciel.

Defer iption

43i

the Depth of the Mines in the Hartz,

A Detail and Calculations of Barometrical Obfervations
made at the Hartz in October 1776.

Obfervations in the Mines of Claufthal.

October 26, 1776, at twenty minutes paft eleven in
the morning, I obferved my Barometer at the entrance
of the pit of the mine call ;d Dorothy, and found it (after
the allowance made for the heat both in this and all the
following obfervations) 26 in. 4. 1. ~ French meafure.

Syndic leyser’s Barometer being placed near mine,,
and obferved every quarter of an hour throughout the
whole day, fell a quarter of a line, between half and three
quarters of an hour after twelve, and did not vary fenlibiy
till four o’clock. It then had a tendency to rife, for it-
was ftationary, though the Thermometer fell ; fo that, on

coming

Defer iption et Calculs des Obfervations du Baronietre faites au Hartz, cn

October 1776.

Obfervations dans les Mines de Claufthal.

Le 26 O&obre, 1776, a 1 1 h. 20 m. du matin, j’obfervai mon baromhre a,
l’entree du puits de la mine nommee Dorothee; et je le trouvai (la correction
etant faite pour la chaleur ici, et dans toutes les obfervations fuiv antes)
26 p. 4I. xg- de France,

Le barometre le M. le Sindlc leyser etant place aupres du mien, et obferve
enfuite pendant tout le jour de quart d’heure en quart d’heur , deicendit d’ J de
ligne de midi \ a midi f ; et ne varia plus lenfiblement juiqu’a 4 heures. Alors
il tendit a remonter; car il fut ftationaire quoique le thermometre baihait:

tellement

432 M. de luc’s Barometrical Obfervations on
coming out of the mines, my Barometer, after the cor-
rection for the Thermometer, was much at the fame
point as when I went in.

I had not made any obfervations in the mines before
this firft variation, fo I will look upon a 6 in. 3 1. as
being the height of the Barometer at the top of the pit
of the Dorothy during my obfervations in the internal
part of the mines till three o’clock. But at fix o’clock I
lhallfuppofe it at 26 in. 3f|.

At

tellement qu’au fortir des mines mon barometre, apres la corre&ion pour le ther-
mometre, fe trouva prefque au meme point que lorfque nous y etions cntres.

Je n’avois point encore obferve dans les mines avant le terns de cette premiere
variation : ainfi je regarderai 26 p. 3 1. t|- comme etant la hauteur du barometre
au haut du puits de la Dorothee pendant mes obfervations dans l’interieur des
mines jufqu’a 3! h. Mais a 6 h. je la fuppoferai a 26 p. 3

A 1 h.

the Depth of the Mines in the Hartz. 433

In. L. i6ths of Lines. Log.

At 1^ h. at two feet'

from the bottom of the > 27 4 —=5260 37209,857

well of the Dorothy,

At the top of the pit, 26 3 13 = 5053 37°35>493

Difference, — — •

The thermometer on the outfide of the
building which is over the mine was at - 2 2
of my fcale for the dilatations of the air ; but
this external temperature reached a very little
way into the mine. At the bottom of the h
pit the thermometer was -15. I reckon the
mean temperature — 1 5^-, and confequently 1
am to deduct from the height found by
the log, — • — — •

174)3

64

5»4°5

Depth of the Dorothy pit in French toifes, 168,959

At

P. L. 16 de Lig. Log.

Dofothi' * 2 piedidu fond f!uei du e de ,a } 27 4 n = 5260 37209,857
Au haut du puits, — — 26 3 13 = 5053 37°35>493

Difference, — — — 174,364

Le thermometre au dehors du batiment qui couvre la mine etoitl
a — 22 de mofl echelle pour les dilatations de Pair.- Mais cette |
temperature exterieure s’etendoit bien peu avant dans la mine. Au *
fond du puns, le thermometre etoit — 15. Je fuppofe la tempera- j ^

ture moyenne — 15J, et en consequence je dois deduire de la
hauteur trouvee par les log, — — — ~

Profondeur du puits de la Dorothee, en toifes de France, — - 1 68 959

Vol. LXVII.

L 1 1

A 3§ h.

434 M. de luc’s Barometrical Qbfer nations on

In. L. 1 6th of Lines. Log.

At 3LI1. at a foot and!

a half from the bot-
tom of the laft ladder
of the Caroline, - j
At the top of the pit
of the Dorothy

4 13= 526i 37210,683

the pit l ,

J26 3 13 = 5053 37035*493

Difference, — — 175,190

In the pit of this mine my thermometer
flood at -11 of the fcale for the dilatations
of the air. But the outfide thermometer being :• 4,455'

then at — 23L, I reckon the mean temperature
at — 1 3, and confequently I dedudt

The bottom of the pit of the Caroline
below the entrance of the pit of the Doro-

170,735

At

P. L. i6deLig.

A q§ h. a pied du bas de la dern. echelle ] ,

de la Caroline, - _ ] 27 4 *3 = 52^1

Au haut du puits de la Dorothe'e, — 26 3 13 = 5053

Log.

37210,683

37°35?493

Difference, — — —

Dans le puit&de cette mine, men thermometre fe tenoit a — 11
de rechelle pour les dilatations de fair. Mais le thermometre etant
alors au dehors a — 23I, j’eflime la temperature moyenne a — 13.
Et confequemment je deduis —

175^9°
4? 45 5

Le fond du puits de la Caroline au deiTous de l’entree du puits de 1 . m

laDorothee, — — — — 1 / *1°>?3S

3

A 6 h#

the Depth of the Mines in the Hartz ,

In. L. 1 6th of Lines.

At 6 o’clock at the'i
bottom of the lowed: |

435

Log.

fearching gallery
the Benedict,

At the top of the^g
pit of the Dorothy, - j

ry of |

7 a 14=5230 37185,017

3 15= 50SS 37037^12

Difference, 147,805

At the place of obfervation in the mine the '
thermometer was at - 8|, higher by 2~ than
at the pit of the Caroline. But as this gal-
lery communicates with the fame pit, and
that confequently the column of air contained 1 3,843

in it is part of that which weighs upon the air
of the gallery, I am only to eftimate the tem-
perature of the pit. I therefore deduct
as in the preceding obfervation, • — -

The gallery, 8cc. of the Benedict, below"] ,

the entrance of the Dorothy, — J

Obfer-

P. L.

A 6 h. au fond de la galerie de recherche la 1 _ , „ _

plus baffe de la Benedi&e, — — J 27 2 H — S23

Au haut du puits de la Dorotliee,

i6deLig. Log.

37 1 ^5501 7
26 3 JS = S°SS 37°37>212

Difference,

Au lieu de 1’obfervation dans la mine, le thermometre etoit a — 8j,1
plus haut de 2^ qu’au puits de la Caroline. Mais comme cette I
galerie communique au meme puits, et que par conlequent la co-
lonne d’air qu’il renferme, fait partie de celle qui pefe fur l’air de la
galerie, je ne dois avoir egard qu’a la temperature du puits. Je
xleduis done T§lt> comme dans ^obfervation precedente, —•

:47>8o5

b843

La galerie, &c6 de la Benedi&e, audeffous l’entreede la Dorothee, 143,962

LI 1 2

Obftr-

436 M. de Luc’s Barometrical Observations on

Obfervations at the Ramelfberg.

On the a 8th of Oitober, at 9! h. I obferved
the barometer under the cover of the entrance
of the mines, two feet and a half above the I 3

aperture of the pit, and found it at — J

At 2| h. when I left the mines, it was at - 2728

Confequently it had rifen -^ths of a line in five
hours; whence, not having made any regular obferva-
tions during this interval, I will fuppofe the variation to
have been equable, that is, ^th by the hour, during the
time I flayed in the mines.

At

Obfervations faites au Ramelfberg.

Le 28 OrRobre, a 9J h. du matin, J’obfervai le Barometre fous le-j
couvert de l’entree des mines, 2^ pieds au defTus- de l’ou-verture du >27 2 3
puits, et je le trouvai a — — — J

A 2j h. au fortirdes mines, il fe trouva a — — 27 2 8

II avoitdonc monte de de lignes en 5 heures; etn’ayant pas eu d’obferva-
tions fuivies pendant cet intervalle, je fuppoferai la variation graduelle, et ainli
par heure, durant Je terns cpie je reftai dans les mines.

Log.

27 7 14=53*° 37250,945-

the Depth of the Mines in the Hartz. 437

In. L. 1 6th of Lines.

At n| h. at the''
bottom of the pit of
Kaunkuhl, —

At 1 2j h. at the
entrance of the gallery
of Breitling 27 4 85127 4 7 = 52.55 37'2°5>7S9

confequently an hour

before at 1 1

Difference, —
At the bottom of the
pit, therm. — — -5

Near the gallery, - -13J

45,218

- 9 mean, dedudtl

-c-- - -4L f

i o o o 9 ' J

therefore 8 '

813

Height of the gallery of Breitling above the 1

bottom. of the pit of Kaunkuhl,

J

y 44,405

At

P. L. i6deLig. Log,

A x if h. au fond puits de Kaunkuhl, — 27 7 14 = 5310 37250,945

A midi \ , a l’entreede la galerie de Breitling; 1 .

27 4 8; done 1 h. plus tot, foil 1 1| h. * — } 27 4 7 — 525$ 37205’72i

Difference, — 45,218

Au fond du puits, therm.' — cl , TS v 1 1 • o

Aupres de la galerie, . - , 3 } “9 nloye"> donc ^ a dedu.re, , ,&i 3

Hauteur de la galerie de Breitling^ fur le fond du puits de Kaunkuhl, 44,405

A mid:

438 M. de luc’s Barometrical Obfer vat ions on

In. L. 1 6th of Lines. Log.

At 1 h. at the

entrance of the gallery . n £ ^

. „ . .. & . J\ 27 4 8 = 5226 37206,554

of Breitling, near the ^ 3 3

pit, — — J

Under cover of the
mines, at the fame
time, — —

• 27 2 6=5222 37178,369

Difference, — — 28,185

Therm, in the pit -13, deduct therefore 732

Deduft the elevation of the barometer 1

above the entrance of the mines,

~ J

27,453

416

The height of the entry of the mines above')
the gallery of Breitling, — — >27,°j7

At

P. L. i6deLig. Log.

A midi i a l’enttee de la galelie de Breitling, 1 g _ 6 37206,554

ipres du puits, — j / j jj

Sous le convert des mines, a cette heure la — 27 2 6 = 5222 37178,369

Difference, — — 28,185

Thermometre dans le puits — 43 ; done -rife a deduire, — ,732

27,453

A deduire ce dont le barometre etoit plus haut que l’entree des mines, ,4.16
•tfauteur de Fentree des mines, fur la galerie de Breitling, •«- 27,037

A aj h.

the Depth of the Mines in the Hartz. 439

In, L. 16th of Lines, Log*

At <iX h. under the 1 0 „

% , . >27 2 8 = 5224 37180,032.

cover of the mines, j

At 2|- h. at the top

of the pit of Kaun-

kuhl, —

26 11 6 = 5174 37138,264

Difference, - — — 41,768

Thefe two obfervations were made on the'
outfide of the mines, the heat of the air being f 419
-II, deduct therefore -ffhzr —

Add the elevation of the barometer under!

the cover, above the entrance of the mines,
Height of the top of the pit of Kaunkuhl!

40,850

918

above the entrance of the mines,

!• 41,266

At

A 2J h. fous le couvert des mines, —
A 2f h. au haut du puits de Kaunkiihl,

P, L, i6deLig. Log.

27 2 8=5224 37180,032

26 11 6 = 5174 37138,264

Difference, — — • 41,768

Ces deux obfervations furent faites au dehors des mines^ la chaleur 1 ~

de Pair etant - — 1 1 $ done a deduire, . — . — - J ’91

40,850

A ajouter ce dont le barometre fous le couvert, etoit au deffus de\ ,

Pentree des mines, — . — . . — . — j 9 41

Hauteur du haut du puits de Kaunkiihl, fur l’entree des mines, 41,266

A- iif h..

44° M. be luc’s Barometrical Qbfcrvations on

In, L. 16th of Lines, Log.

At i iy h. at the'
bottom of the pit of
Kaunkuhl as above,
At 2^ h. at the top'
of the pit 26 11 6,
confequently at 1 1 jh.

27

26

7 14=5301

11 3=Si7i

37250,945

37135)745

Difference,
At the bottom of the
pit, therm. —5

At the top, —13.

115,200

— 9, confequently]
-rw to dedu£f,' j

2,074

Total depth of the pit of Kaunkuhl, — 1 1 3,1 26

Obfer-

p.

A n\ h. an fond du puits de Kaunkuhl, 1
comme ci-deffus, — — J 27

A 24 h. au haut du puits 26 11 6, doncl ,
anil,. - - J 26

L. i6deLig. Log.

7 14 = 531° 37*5°>94S
n 3 = 5i7i 37!35»745

Difference, — —

Au fond du puits, therm. — cl ,

Au haut, — 10 } 9’ donc^adedmre,

1:1,5,20°

2,074

Profoncleur totale du puits de Kaunkiihl,

113,126

the Depth of the Mines in the Hartz.

44*

Obfervations at two Points geometrically determined on
the outjide of the Mountain , relatively to the Mine of

Alte Seegen.

On the 30th of October, at 10 in the
morning, I obferved the barometer under the
cover of the mine called Alte Seegen near
Zellerfelt, and found it at — — j

At half an hour paft feven at night, at my 1

In.

>21 71 2

return from thefe obfervations, it was at

j-2 6 6 8

Confequently in nine hours and a half the barometer
fell j|ths of a line ; and by obfervations made by Syndic
Leyser, this fall was gradual.

At

Obfervations en deux Points dete mines geometriquement a F cxtericur de la Mon -
iagne , relativement a la Mine d’Alte-Seegen.

Le 30 Oftobre, a io h. du matin, j’obfervai le barometre fous 1cm P. L.
convert de la mine nominee Alte Seegen, iituee pres de Zellerfeld, ew 27 71 2
je le trouvai a — — — — '

A 7 1 h. du foir, au retour des obfervations ci apres, il fe trouva a 26 6 8

Ainfi en 9§ h. le barometre baiffa de if de ligne. Et par des' obfervations
faites d’heure enheure par M. le Sindic leyser, cet abbaiffement fut gra.dueK

im<

Vol. LXVII,

M m m

442 -M. de Luc’s Barometrical Obfervations on

In.

At 1 2 h. in the val-
ley of Bremeke, half a ^
toife lower than a cer-
tain determined point,
At Alte Seegen, two"!
hours after the firft j”
obfervation, — J

27

27

L. 1 6th of Lines. Log*

3 2 = 5234 37188,357

7 0 = 5104 37079,107

Difference, — —— 109,230

Heat of the air -30, confequently to deduct 6,554

102,676

Dedudl the half toife above mentioned, — 500

French toifes, — - 102,176

At

P. L. i6deLig. Log*

A midi, dans la vallee de Bremeke, £ toife 1 __ . . QQ _

|>lus bas qu’un certain point determine, J 27 3 2 — 5234 37 1 >3 37

S“E“’ -■ ‘P“ “ »b- j 26 , 0 = 5104 37079,10,

Difference, — — 109,230

■Chaleur de Pair —30; done Tfl^ a deduire, ~ — 6*554

A deduire la demi toife ci-deffus,

Toifes de France,

102,676

,5°°

102,176

A if h*

443

the Depth of the Mines in the Hartz.

In. L. 1 6th of Lines. Log.

At 1 1 h. atLasfelde )

without the Hartz, inf _ ,

, „ , , 27 8 10= 5322 37260,74a

the valley of Ofterode, f 1 30 3

at a determined point, j
At Alte Seegen,
about four hours after 1 27 8 10=5102 37077,403

the firft obfervation,

183,344

Heat of the air - 26, confequently to deduct 9,534

French toifes,

173,810

Obfer-

P. L. i6deLig. Log.

’-7 8 10 = 5322 37260,7

JLSiZaZ “”°-4 “• >P F''h 6 *4=5"* 37077>4°S

* »=*** 37460,749

Chaleur de Fair — 26 ; done Tllo a deduire,
Toifes de France*

183,344

9>534~

173,810!

M m m 2

Gbfer-

444 M. de lug’s Barometrical Obfervations on

Obfervations to determine the height of the Brocken with
refpetl to Gottingen and Hanover.

The 25th of October, on fetting} In-
out from Oder-brucke for the /

K 2r q q

Brocken, at three quarters part eight f “ 5 J
in the morning, — j

In returning, at 3^ h. — 25 8 14

Difference, — 00 10

Obferved at the Brocken at Noon and at 1 o’clock, the
mean, at about 1 a|h. makes nearly half the fpace of time
above mentioned ; confequently the height of the baro-
meter at Oder-brucke at that hour may be reckoned at
25 9 3-

Sindic

Obfervations pour determiner la hauteur du Brocken relativement d Gottingue

et dr Hanovre.

) On the
[ firft floor

1m the
Inn.

P. L.

Le 25 O&obre, en partant d’Oder-brucke pour le 1 « Au premier

Brocken, a 8J h. du matin, — — J 25 9 letage du Ca«

En reyenant, a 3J h. ~~ — 25 8 i4Jbaret.

Difference, - — — - o o 10

Obferve au Brocken a midi et a 1 heure. Le milieu, midi f , fait a peu pres
ta moitie de Pintervalle de terns ci-deffus; et par confequent on peut evaluer
h hauteur du barometre a Oder-brucke a cette heure la, 25 9 3.

M. le Sindic

the Depth of the Mines in the Hartz. 445
Sindic leyser obferved the barometer at his houfe at
Claufthal, in the morning and at noon; when inftead of
falling, as at Oder-brucke, it rofe half a line, and re-
mained at that point till the evening. The only caufe to
which I can afcribe this difference between his obferva-
tion and mine, is the increafe of heat in his room : but
there was no obfervation with the thermometer to correct
the effeft of this caufe; I fhall therefore content myfelf
with my own obfervation for this meafure, though I
employ Mr. leyser’s for the following one.

M. le Sindic leyser obferva le barometre chez lui a Claufthal le matin et
a midi: et au lieu de baiffer, comme a Oder-brucke, il monta de § ligne, et
refta a ce point jufqu’au foir. Je ne faurois attribuer cette difference entre 1’ob-
fervation de M. leyser et la mienne, qu’a ce que la chaleur augmenta dans la
^chambre: mais il n’y eut point d’obfervation du thermometre pour corriger
Feffet de cette caufe. Je m’en tiens done a mon obfervation feule pour cette
mefure-ci; quoique j’employe celle deM. leyser pour la fuivante*

A midi

446 M. de luc’s Barometrical Obfervations on

In. L. i6thof Lines. Log*

At 1 h. the baro-1

meter at Oder-brucke I25 9 3 = 4947 36943,419

muft have been at, J
At the Brocken,

at 1I1. 5 m. % 8 f } mean 29 8 3 = 4739 36756,867

Difference, — —

On fetting out from 1
Oder-brucke the heat > — 3 4^- 1
of the air was at - J

At our return, - -31^-

At the Brocken, —

>-33

-40

-36^

confeq.

Lll. to

1000

deduct,

186,552

► 1 3,6i S

Height of the Brocken above Oder-brucke, 172,934

By

P. L. i6deLig. Log.

A midi | le barometre devoit etre a Oder- brucke,25 9 3 == 4947 36943,419

Au Brocken, | ? T'h.^ m. 24 8 1 } moyen> 24 8 3=4739 36756)867

Difference,-

—

—

186,552

En partant d’Oder-brucke, l&chaleur de 1
I’air etoit* — — J

Au retour, - — —

Au Brocken, — * — —

~ 341 1

—3*i J

'—33
— 40-

) -361 '

>donc -r lbs
J a deduire*

| 1 3)6 1 8-

Hauteur du Brocken fur Ockr-brucke,,

—

—

172,934

Par

the Depth of the Mines in the Hartz. 447

By the above mentioned obfervations of Mr. de ley-

ser’s, and by the comparifon between his barometer

and mine, 1 have reafon to conjecture, that at the time of

the mean obfervation of the barometer at Oder-brucke,

In. L. 1 6th of Lines. Log.

it flood at Claufthal at, 26 4 3 = 5059 37040,647

Mean height ob-'i ,

ferved at Oder-brucke, j ^ 3-4947 3 943>4I9

Difference, — -

The mean heat of the air muft have been a
little greater than at Oder-brucke ; I compute •
it at -30, confequently to deduct,

97,228

5?-834

Height of Oder-brucke over the firft floor ^
of Mr. DE leyser’s houfe at Claufthal, or
what comes to the fame nearly, above the firft-
floor of the Crown Inn, where I lodged, -

f- 91,394

The

Par les obfervations ci-deffus de M. leyser, etpar la comparaifon faite de fon
barometre avec le mien, j’ai lieu de conjedturer, que lors de 1’ obfervation moyenne

P. L. ibde big. Log.

du barometre a Oder-brucke, il etoit a Claufthal, 26 4 3 “5059 37040,647

Hauteur moyenne obfervee a Oder-brucke, 25 9 30=4947 36943,419

Difference, — 97?

La. chaleur moyenne de Fair devoit etre.un.peu plus grande

Oder-brucke0 Je la fuppole a — 303 done

60

1000

qu

dec! u ire.

} 5,834

Hauteur d’Oder-brucke fur le premier etage de la rnailbn de o'!

LEYSER a Claufthal, ou, ce qui revient -a peu pres au meme, fdr ie > 91.394
; premier etage de Fauberge de la Couronne ou j’etois ioge, *■'

44 8 -W. de luc’s Barometrical Obfervations on

The mean term betwixt 1 7 obfervations of the baro-
meter, made at Gottingen from the 24th of October to
the 1 ft of November, by Profeffor erxleben, cor-

In. L. 1 6th of Lines. Log.

rented for the heat, 27 9 3 = 5331 37268,09

The mean term of
17 obfervations made
upon the firft- floor of

the Crown Inn at j. 26 4 8 = 5064 37044,94

Claufthal, correfpond-
ing for the time to
thofe of Gottingen,

Difference,

during the obfervations
at Gottingen,

At Claufthal,

~\

**

.-06I

- 29 confeq.

"tHo deduct. |

1

-31b

J

— 223,15

12,94

Height of Claufthal above Gottingen ,

210,22

Le terme moyen entre 17 obfervations du barometre faites a Gottingue, da
24 au 21 O&obre, par M. Ie Profeffeur erxleben, corrigees aulli pour la

P. L. i6deLig. L og.

chaleor, — — _ — 27 9 3 = 533l 37268>°9

Le terme moyen de 17 obfervations faites air
premier etage de la Cauronne a Claufthal, corre- 1 A 0_ c
fpondantes pour le terns avec celles de Got- > 2 ^ — 5° 4 3/°44>94

Differ

*enee.

22

Chaleur moyenne de Pair pendant les obfervations^ ^ 1

4 Gottingue, _ - -26f j I2’94

""" 3 D j

De meme a Claufthal,

Hauteur de Claufthal fur Gottingue,

210,21

Le

the Depth of the Mines in the Hartz. 449

Mean term of 1 6 obfervations made at Hanover, from
the 24th of October to the ift of November, by Mr.
de hinuber, with a barometer of Mr. dollond’s made

to agree with mine,
That of the corre-
fponding obfervations
for the time, made by
Mr. ERXLEBEN,

In.

L.

1 6th of a Line.

Log.

28

2

3= 5411

37332,775

27

9

9= 5337

37272,972

Difference,

Mean heat at Hano-~

1

! ]

ver, at the time of the

"~a9r !

[-28, confeq. 1

obfervations,

1 1

! -0-0-0 to dedudt

The fame at Gottingen, - 26^]

1 J

Height of Gottingen above Hanover,

59>8o3

3*349

56,454

Le terme moyen de 16 obfervations faites a Hanovre, du 24 O&obre au
I- Novembre, par M. de hinuber, avec un Baremetre de M. dollond, mis.

P. L. i6deLig.. Log.

d’accord avec le mien, « — — 28 2 3 zr 5411 37332,775

CeJuides obfervations correfpondantes pour lei ........

terns, faites par M. ERXLEBEN, — • J 7 9 9 5o3/ 37 7 >97

Difference, — — ~ 59, 803

Chaleur moyenne a Hanovre au terns des ob-y og > y

fervations, — — — ss - >

De meme a Gottingue, —

Hauteur de Gottingue fur Hanovre,

2p j liiv a deduire,j

> 3-349!

56>45+

Vol. LXVII.

N n a

[ 45® ]

XXIII. tfhe general Mathematical Laws which regulate
and. extend Proportion univerfally, or , a Method of
comparing Magnitudes of any Kind together , in all the
pojfible Degrees of Increafe and Decreafe. By James
Glenie, A. M. and Lieutenant in the Royal Regiment of
Artillery,

Read March 6, / g ^HE do&rine of proportion laid down

1777* fa

by euclid, and the application of it
given by him in his Elements, form the bails of almoft
all the geometrical reafoning made ufe of by mathema-
ticians both ancient and modern. But the reafonings of
geometers with regard to proportional magnitudes have
feldom been carried beyond the triplicate ratio , which is
the proportion that iimilar folids have to one another
when referred to their homologous linear dimeniions.
This boundary, however, comprehends but a very
limited portion of univerfal comparifon, and almoft va-
niilies into nothing when referred to that endlefs variety
of relations, which muft neceflarily take place between
geometrical magnitudes, in the infinite polfible degrees
of increafe and decreafe. The firft of thefe takes in but

a very

Mr . glenie’s Method , &c. 451

a very contracted field of geometrical comparifon;
whereas the laft extends it indefinitely. Within the
narrow compafs of the firft, the ancient geometers per-
formed wonders, and their labours have been pufhed
Hill farther by the ingenuity and indefatigable induftry
of the moderns. But no author, that I have been able to
meet with, gives the leaft hint or information with re-
gard to any general method of expreffing geometrically,
when any two magnitudes of the fame kind are given,
what degree of augmentation or diminution any one of
thefe magnitudes rauft undergo, in order to have to the
other any multiplicate or fub-multiplicate ratio of thefe
magnitudes in their given ftate; or any fuch ratio of
them as is denoted by fractions or furds ; or (to fpeak ftill
more generally) a ratio which has, to the ratio of the
firft-mentioned of thefe magnitudes to the other, the
ratio of any two magnitudes whatever of the fame but
of any kind. Neither have I been able to find that any
author has fliewn geometrically in a general way, when
any number of ratios are to be compounded or decom-
pounded with a given ratio, how much either of the
magnitudes in the given ratio is to be augmented or di-
minished, in order to have to the other a ratio, which is
equal to the given ratio , compounded or decompounded
with the other ratios. To invefcigate all thefe geome-

N n n 2 trically,

45 2 Mr. olenie’s Method of comparing
trically, and to fix general laws in relation to them, is
the object of this paper ; which, as it treats of a fubjedt
as new as it is general, I flatter myfelf, will not prove
unacceptable to this learned Society. It would be alto-
gether fuperfluous for me to mention the great advan-
tages that muft neceffarily accrue to mathematics in ge-
neral, from an accurate inveftigation of this fubjedl, fince
its influence extends more or lefs to every branch of ab-
ifradt fcience, when any data can be afcertained for rea-
soning from. I fhall, in a fubfequent paper, take an op-
portunity of fhewing how, from the theorems after-
wards delivered in this, a method of reafoning with finite
magnitudes, geometrically, may be derived, without any
eonfideration of motion or velocity, applicable to every
thing to which fluxions have been applied; and fhall
now proceed to the fubje£t of this paper, after premifing
the two following definitions.

DEFINITION I.

Magnitude is that which admits of increafe or decreafe.

DEFINITION II.

^Quantity is the degree of Magnitude.

By magnitude, befides extenfion, I mean every thing
which admits of more or lefs, or what can be increafed

or

Magnitudes of any Kind together . 453

•or diminifhed, fuch as ratios , velocities, powers, &c. As
1 fhall frequently, for the fake of concifenefs and con-
■veniency, be obliged to make ufe of particular modes of
expre fling geometrical magnitudes, I here obferve, once

for all, that by fuch expreflions as thefe a. a.-~b >

A. ? , a.———, &c. I mean refpeftively a third pro-

portional to B and a ; a fourth proportional to b, a, and
the difference of A and b ; a fourth proportional to d, a,

and the' difference of c and d ; a fourth proportional to b,
- £

a. — — and a-b, Sec.

To proceed then in the order in which I firft invefti-
gated thefe theorems ; let a, b, c, d, e, f, g, h, See. be
any number of magnitudes of the fame kind, taken two

y z s R

A

I X

T

Q.

C—I>

A.— —

D

-E

A

C F

B

V K M L M NO

.and two from the firft ; and let mm, no, nr, op, refpec-
stively reprefent a, b, c, d. Let nr, op, be drawn per-
pendicularly

454 -Mh glenie’s Method of comparing

pendicularly to vo, or otherwife if in the fame angle ; and
let the redtangles or parallelograms MR, np, be com-
pleted. Let lm be a fourth proportional to op, mn and
nr- op; and let the rectangle or parallelogram LQ.be
completed.

Then (14. e. 6.) lt is equal to tr, and confequently
LQ_to mr. But (23. e. 6.) mr has to np the ratio com-
pounded of the ratios of mn to no and nr to op. There-
fore (1. e. 6.) ln has to no the ratio compounded of the
ratios of mn to no and nr to op. But ln is equal to

mn+ mn.NR0?w, or A + A.ppp by conftru&ion. Whence
it appears, that a magnitude of the fame kind with a
and e, which has to b the ratio compounded of the ratios

of a to b and c to d, is expreffed by a + a.

In like manner let e, f, be reprefented by rn, op, re-
fpedtively, and let lk be a fourth proportional to op, ln,
and qr. Then (14. e. 6.) kx is equal to xr or tr and xs
together. But fince ln hath already been fhewn to be

equal to a + a.^~ , lk is a fourth proportional to F, e-f,

and a + a.— — ; that is equal to a,— ^— + A. -p-* — — • by
conftrudtion. Wherefore kn being equal to lk + ln is

equal to a + a.— + a. — - + a. • * And fince

1 D F D F

XQ. is equal to lr, kn has to no a ratio compounded of

the

x

Magnitudes of any Kind together. 45 5
the ratios of ln to no and nr to op ; that is, of the ratios
A to B, c to D, and e to F. Therefore a magnitude of the
fame kind with a and b, which has to b the ratio com-
pounded of thefe ratios is expreffed by a+ a. + a.

C — D E — F v

+ A’ ~T~ ' T-0

Again, if nr, op, be fuppofed to reprefent g, h, re-
fpedtively, and kv a fourth proportional to op, kn, and
qr; vQ.will be equal to kr (14. e. 6.) and confequently
vn will have to no a ratio compounded of the ratios of
kn to no and nr to op ; that is, of the ratios a to b,
c to D, E to F, G to H. But vk is by conhruchion equal to

G H C — D G — H E — F G — H C — D E — F G — H

Ai T3 A® _ • 77 A* “ ” • ~ “I” A» ~ • ' ~

And this added to kn above found gives a + a.

H

C — - D
D

> E — F G — H C D E-

+ A. — - + A. — h A.

G— H

+ A.—

H D

F H D

C— — D E — F G — H
F H *

•F C— D G H E — F

- + A.— .— + A.—

for the magnitude of the fame
kind with A and b, Vvhich has to b the ratio compounded
of the ratios a to b, c to d, e to f, g to h ; whence the
law of continuation is manifefh

The fame conclufions may be derived from (e. 5.);
fo that no principle can be Ampler or more geometrical
than that here made ufe of.

Thus then thefe magnitudes will hand.

a- a+ a. when two ratios are compounded.

a. A

45 6 Mr. glenie’s Method of comparing

C— D E F C — D E F , -

2. a+ a. — + a.—- + a. — . — , when three are

compounded.

3. AH- A.— - +

0 D

C D E F G — H C — D G — F C — D*

A-— + A.— + A. — --7“ + A.—

G — H E — F G — H

+ A.

H

— n C D E F G H , r

— + a. — - . — . — - , when four ratios

ri D r H *

are compounded, 8cc. See.

By continuing this operation much farther, I found
upon examination that the number of terms in which A
is connected with the differences c-d, e-f, g-h, See.
taken one by one, two by two, three by three, Sec. if p
denote the number of ratios compounded, is expreffed

refpedtively by *=-r> ^ ^ ^=-3> 8cc. Thus

if the ratio of a to b be fuppofed equal to the ratios of
c to d, e to f, g to h, 8cc. refpe&ively, thefe exprefiions
will give the following ones.

2 — I A — B

I. A + .A.

l B

2 1 A B 2 — I 2 — 2 A — B>

2. A+- . A.— i“— — . .A.——

I B I 2 B

0 , . -4—i « „ A~ e1 , 4-i 4—2 4—3

3» A 4- • A. t . • A . 4“ " • •

u 1 B12 b 1 2 2

A— i)

a. — — ; for magnitudes of the fame kind with A

and b, which have to b refpedlively the duplicate,
triplicate, and quadruplicate ratio of a to b ; where p
is fucceffively equal to a, 3, and 4. And univerfally,
by the fame geometrical reafoning, it is found, that

A +

> 1 A B

—.A.——

+ 8ec.

A.

has to

B fuch

Magnitudes of any Kind together . 4 57

b fuch a multiplicate ratio of a to b as is expreffed by
the number /*.

In the reafoning above I fixed on b as the magnitude
to which the reft were to be referred ; but I might as well
have fixed on a or any of the other magnitudes. Thus,

r „ p — I B A p 1 p 2 B aT ^

for mltance, b+ -—.b, — + — - . - — .b. + &c.

2 A I Qi A

B.— — — - has to a fuch a multiplicate ratio of b to a

as is expreffed by the number p; or a has to b +

p 1 B A p— I p— 2 B — a! Z -

- — b. - — * b. + &c. b. the ratio

I A I 2 A A

A E

c 'p — I A — B p — I p — 2 o

of At- — .A. + — .A.— : + & C. A.

A — B

ip— I

tOB

that is, fuch a multiplicate ratio of a to b as is expreffed'
by the number p. Each of thefe, indeed, I demonftrated
feparately from the fame fort of geometrical reafoning ;
but for the fake of brevity I omit fetting down thefe
feparate demonftrations, as they are both contained in
general reafoning above, which furnifhes likewife a great

variety of other expreffions, according as certain num-
bers of the ratios c to d, e to f, g to h, &c. are fuppofed
to be refpedtively equal to, greater or lefs than, the ratio
of a to s.

Vo l. LXVII.

O o o

[ 458 ]

XXIV. 'The Cafe of Ann Davenport. By Mr. Fielding
Bell F ynney, Surgeon at Leek, in Staffordfhire ;
communicated, to Thomas Percival, M. D. F. R. S. and
by him to Sir John Pringle, Bart. P. R. S.

TO SIR JOHN PRINGLE, BART. P. R. S.

ST u Mancheftcr,

A April 8,

Head Apni io, TT TOOK the liberty, a few days ago, of
tranfmitting to you, by a private hand, a
Singular cafe, fent me by Mr. f. b. fynney, an ingenious
furgeon, who is fettled at Leek in Staffbrdfhire. He de-
fires that it may be laid before the Royal Society ; and I
Shall think myfelf much obliged by your compliance
’wifla Ms requefh

TO

Mr. fynney’s Account , &c.

459

TO DR. PERCIVAL.

q T n I^eekf

s 1 March iot 177 7.

UPON May 16, 1775, being defired to vifit ann
davenport, a native of this town, I beheld a truly rai-
ferable object, with the mo ft cadaverous countenance I
had ever feen, emaciated to the laft degree by a hectic
fever, and profufe colliquative fweats. She had a con-
tinual thirft, her appetite was totally gone, and ftie was
ahVays in the extremes of being too loofe or too bound.

Her mother informed me, that fhe was then in her
twenty-firft year; and that ihe had been a ftrong and
fprightly child from her birth, until fhe was about five
■years of age, from which time fhe had been a ftranger to
health, and every now and then had been feized with
excruciating fits of the colic, efpecially whenever fhe
ate or drank any thing the leaft acid.

The young woman told me, that about a year ago
fire had firft perceived a fwelling on the right fide of
her belly, juft above the groin; which, if at any time
fhe attempted to ftretch out her thigh, .gave her inex-
preflible pain, as if fomething {tabbed her in that part:

O o 0 2, that

46o Mr. fynney’s Account of

that therefore Hie was always obliged to keep up her

knees, more or lefs, towards her bread:, by which means

fhe had, in fome degree, loft the power of extending her

limbs.

I ordered her to take half a drachm of powdered
bark in a little red port wine every four hours ; and, as
matter had already formed within the tumor, I defired
that a maturating poultice might be applied every night
and morning ; for I imagined that nature, without fuch
afliftance, could never bring the abfcefs to a head in her
weak condition.

July i oth, the matter pointing at the upper end of
the tumour very near the os ilium , I made a large open-
ing, from which was difcharged an amazing quantity of
pus ; but, as the tenlion Was ftill great, I applied a linfeed
poultice over the common dreffings : neverthelefs, in a
few days a fecbnd, abfcefs began to form towards the ver-
tebra of the loins, between the falfe ribs and the as ilium y
which was rapid in its progrefs, for it was brought to
maturation, and opened on the 26th.

On the 31ft I was alarmed with a gangrenous ap-
pearance of the whole integuments of the abdomen : for
this fhe took one drachm of powdered bark in red-port
every three hours ; but, as vefications and every fym-

s ptom

the Cafe of ann davenport. 461

ptom of a fphacelus continued to increafe, I likewife ufed
the bark externally, in the two following forms, every
morning and evening:

Ei Final. Cort. Peruv. Simp. % ij

Myrrh. Comp. ? j

Sp. Sal. Ammon.

Mell. AEgypt. aa. ^ ff. m.Jiat embrocat.

Free. Cerevif. acid. Ibj

Farin. Avenac. q. s. coque ad confiflentiam Cata-
plafmatis , et adde Pulv. Cort. Peruv. ^ j
01. Olivar. rec. § iv m.Jiat Cataplafm.

This treatment foon put the mortification to a ftand,
and the parts Houghing off largely left three holes, at
nearly equal diftances one from another, betwixt the fir ft
opening and the left os ilium , befides feveral ones in dif-
ferent parts of the belly ; but as the difeharge was immo-
derate, I looked upon the patient to be in the utmoft
danger. However, the fame courfe was perfevered in,
and at the latter end of Auguft another abfeefs appeared
lower down, towards the right groin; I ordered it to be
poulticed, and left it to open of itfelf, which it did on the
21ft of September. I was immediately called to her;

and,

462 Mr. fynney’s Account of

and, upon carefully examining the part, I found a hard

fubitance deeply feated, which I directly extradled'^.

It was making its way towards the integuments from
the extremity of the appendix vermiformis of the cecum,
which probably, and fortunately, by former inflamma-
tions had adhered to the peritoneum. The large end
came firft, and the fmall end was within the appendix
vermiformis of the cecum at the time I took it out ; for,
immediately upon the extraction, fome excrements fol-
lowed, and among them fome dark brown particles
which I difcovered to be filings of iron, which the patient
had formerly taken in a large quantity, as flie had never
been regular like other women. On a careful examina-
tion I found fome of thefe filings quite reduced to ruft,

(a) See plate IX. the figures 1. and 2. are different views of the external
furface of this irregular fubftance, and of fo much of its nucleus as proje&s out
of the round part, exaddy as both appeared on being taken out of the body*.
The whole was of a dufky brown colour, and had a great relemblance to a
fmall fhrivelled pear. Fig. 3. is a fe£lion of the round part, which feemed to
be formed of fine fibrous fubftances, clofely cemented together by an earthy
matter, and of die peg of crab-tree wood, its nucleus . This figure likewile
fhews how far the peg went in, and alfo an incruftation of (tony matter upon it.

The nucleus , I believe, is the fmaller end of that part of a fillc engine called
a flar, at which machine the patient had been employed before fhe was five
years of age, therefore it muff have been lodged at leafl fixteen years within
the appendix vermiformis of the ccecum, as fhe remembers nothing of fvvallowing
and as during that courfe of years file had frequently been afflidled. with tke
feyere colics before-mentioned.

but

tie Cafe of ann davenport. 463

tut ftill retaining their form as they came from under
the file.

Some feces came through this laft wound daily, fre-
quently moil copioufly; and fometimes (though the ex-
ternal orifice was large) by being confined with the
dreffings, they infinuated themfelves between the inte-
guments of the abdomen, and came through the other
openings. About the middle of February 1776, the
difcharge of the excrements by thefe openings was fen-
fibly diminifhed; and the wounds were all healed, except
one, by the latter end of the year, through which a fmall
quantity of excrements ftill continue to pafs now and
then.

Her health Is, within this fhort time, furprizingly
improved; fhe is now very flefliy and ftrong, has had
the catamenia, and I have the greateft reafon to expect
that fhe will be perfectly cured. Strict regard was all
along paid to the non-naturals.

As the cafe above is a very uncommon one, I prevailed
on the reverend Mr. Rogers, minifter of this place, to
vifit the patient along with me; and he was fo fully
•fatisfied of the truth of the account, as to give me the
fallowing certificate.

I hereby

464 ryNNEYrs Account , &c.

I hereby certify, that I faw, this 27 th day of Decem-
ber, 1775, Mr. fielding best fynney drefs his patient
ann davenport, and was an eye-witnefs to pure faces
coming out of the wound from which he had extracted
an irregular fubftance on the 21ft of September laft.

As witnefs my hand,

J. ROGERS,
Minifter of Leek.

'

[ 4«5 ]

KB

XXV. An Account of the Kingdom of Thibet. In a
Letter from John Stewart, Efquire , F. R. S. to Sir
John Pringle, Bart . P. R. S.

London,

S I Rj March 20, 1777.

Read April 17, 1 'VQRING my late refidence in India, a
1 7 7 7» S JP

■* — * tranfadtion took place in Bengal,
which, in its confeqnence, led to a new and more inti-
mate knowledge of a vaft country, hitherto unexplored
by Europeans, and hardly known to them but by name.
As every difcovery of this fort tends to the advancement
of natural knowledge, I have thought a fhort notice on
the fubjedt might prove no difagreeable communica-
tion to the Society ; and therefore take the liberty, with
your approbation, to fubmit it, in this manner, to them.

The kingdom of Thibet, although known by name
ever lince the davs of marco paolo and other travellers

J

of the twelfth and thirteenth centuries, had never been
properly explored by any European till the period of
Vol. LXVII, P p p which

466 Mr. stewart’s Account of

which I am now to fpeak. It is true, fome ftraggling
miffionaries of the begging orders had, at different times,
penetrated into different parts of the country ; but their
obfervations, directed by ignorance and fuperftition,
placed in a narrow fphere, could give no ideas but what
were falfe and imperfecSt. Since them, the Jefuits have
given the world, in duhalde’s Hiftory of China, a fhort
account of this country, collected, with their ufual pains
and judgement, from Tartar relations, which, as far as it
goes, feems to be pretty juft.

This country commonly paffes in Bengal under the
name of Boutan. It lies to the northward of Hindoftan,
and is all along feparated from it by a range of high and
fteep mountains, properly a continuation of the great
Caucafus, which ftretches from the ancient Media and the
fhores of the Cafpian fea, round the north-eaft frontiers
of Perfia, to Candahar and Caflamire, and thence, con-
tinuing its courfe more eafterly, forms the great northern
barrier to the various provinces of the Mogol empire,
and ends, as we have reafon to believe, in Affam or Ghina.
This ftupendous Tartar bulwark had ever been held im-
palpable by the Mogols, and all other Muflulman con-
querors of India : and although in the vallies lying be-
tween the lower mountains, which run out perpendicular
to the main ridge, there refide various Indian people,
1 whom

the Kingdom of Thibet. . 467

whom they had occafionally made tributary to their
power, they never had attempted a folid or permanent-
dominion over them. It was on occafion of a difputed
fucceffion between the heirs of one of theRajah’s or petty
fovereigns of thofe people, that the Boutaners were called
down from their mountains to the affiftance of one of
the parties ; and our government engaged on the oppofite
fide. The party affifted by us did not fail in the end to
prevail; and in the courfe of this little war two people
became acquainted who, although near neighbours, were
equally Grangers to each other. At the attack of a town
called Cooch Behar, our troops and the Boutaners firft
met; and nothing could exceed their mutual furprize in
the rencounter. The Boutaners, who had never met in
the plains any other than the timid Hindoos flying naked
before them, faw, for the firft time, a body of men, uni-
formly cloathed and accoutred, moving in regular order,
and led on by men of complexion, drefs, and features,
luch as they had never beheld before : and then the ma-
nagement of the artillery, and inceflant fire of the muf-
quetry, was beyond any idea which they could have con-
ceived of it. On the other hand, our people found them-
felves on a fudden engaged with a race of men unlike
all their former opponents in India, uncouth in their ap-
pearance, and fierce in their aftault, wrapped up in furs.

P

P P

and

a

468 Mr. stewart’s Account of

and armed with bows and arrows and other weapons

peculiar to them.

The place was carried by our troops, and a great many
things taken in the fpoil, fuch as arms, cloathing, and
utenlils of various forts. Images in clay, in gold, in fil-
ver, and in enamel, were fent down to Calcutta; all
which appeared perfectly Tartar, as we have them repre-
fented in the relations and drawings of travellers; and
there were befides feveral pieces of Chinefe paintings
and manufactures. Whilft thofe things continued to be
the fubjeCt of much converfation and curiofity to us in
Bengal, the fame of our exploits in the war had reached
the court of Thibet, and awakened the attention of the
Tayfhoo Lama, who (the Delai Lama being a minor)
was then at the head of the Hate. The Dah Terriah, or
Deb Rajah as he is called in Bengal (who rules imme-
diately, over the Boutaners, and had engaged them in the
war) being a feudatory of Thibet, the Lama thought it
proper to interpofe his good offices, and in confequence
lent a perfon of rank to Bengal, with a letter and pre-
fents to the governor, to folicit a peace for the Dah, as
his vaffal and dependant.

Mr. Hastings, the governor, did not hefitate a mo-
ment to grant a peace at the mediation of the Lama, on
the moft moderate and equitable terms; and, eager to

feize

the Kingdom of Thibet. 469

feize every opportunity which could promote the intereft
and glory of this nation, and tend to the advancement
of natural knowledge, propofed in council to fend a per-
fon in a public character to the court of the Tayfhoo
Lama, to negotiate a treaty of commerce between the
two nations, and to explore a country and people hitherto
fo little known to Europeans. Mr. bogle, an approved
fervant of the company, whofe abilities and temper ren-
dered him every way qualified for fo hazardous and un-
common a million, was pitched on for it. It would be
foreign to my purpofe to enter into a detail of his pro-
grefs and fuccefs in this bufinefs : it will be fufficient to
fay, that he penetrated, acrofs many difficulties, to the
center of Thibet ; refided feveral months at the court of
the Taylhoo Lama ; and returned to Calcutta, after an
abfence of fifteen months on the whole, having executed
his commiffion to the entire fatisfadtion of the admi-
niftration. I have reafon to believe that Mr. bogle will
one day give to the world a relation of his journey thi-
ther, accompanied with obfervations on the natural and
political ffcate of the country. I only, in the mean time,
beg leave to mention a few particulars, fuchas my recol-
ledtion of his letters and papers enable me to give.

Mr. bogle divides the territories of the Delai Lama
into two different parts. That which lyes immediately

contiguous

470 Mr. stewart’s Account of

contiguous to Bengal, and which is called by the inha-
bitants Docpo, he diftinguilhes by the name of Boutan ;
and the other, which extends to the northward as far as
the frontiers of Tartary, called by the natives Pu, he
flyles Thibet. Boutan is ruled by the Dah Terriah or
Deb Rajah, as I have already remarked. It is a country
of fteep and inacceffible mountains, whofe fummits are
crowned with eternal fnow; they are interfered with
deep vallies, through which pour numberlefs torrents
that increafe in their courfe, and at laft, gaining the
plains, lofe themfelves in the great rivers of Bengal.
Thefe mountains are covered down their fides with forefts
of ftately trees of various forts ; fome (fucli as pines, Sec )
which are known in Europe ; others, fuch as are pecu-
liar to the country and climate. Tire vallies and fides of
the hills which admit of cultivation are not unfruitful,
but produce crops of wheat, barley, and rice. The in-
habitants are a ftout and warlike people, of a copper
complexion, in fize rather above the middle European
ftature, hafty and quarrelfome in ther temper, and ad-
dicted to the ufe of fpirituous liquors; but honeft in
their dealings, robbery by violence being almoft unknown
among them. The chief city is Tafley Seddein fituated
on the Patchoo. Thibet begins properly from the top of
the great ridge of the Caucafus, and extends from thence

in

the Kingdom of Thibet. 47 r

In breadth to the confines of Great Tartary, and perhaps
to fome of the dominions of the Ruffian empire. Mr.
bogle fays, that having once attained the lummit of
the Boutan mountains, you do not defcend in an equal
proportion on the fide of Thibet ; but, continuing ftill
on a very elevated bafe, you traverfe vallies which are
wider and not fo deep as the former, and mountains that
are neither fo heep, nor apparently fo high. On the
other hand, he reprefents it as the moh bare and defolate
country he ever faw. The woods, which every where
cover the mountains in Boutan, are here totally un-
known; and, except a few draggling trees near the vil-
lages, nothing of the fort to be feen. The climate is
extremely fevere and rude. At Chamnanning, where
he wintered, although it be in latitude 3 1 0 39', only 8°
to the northward of Calcutta, he often found the ther-
mometer in his room at 290 under the freezing point by
Fahrenheit’s fcale; and in the middle of April the
handing waters were all frozen, and heavy fhowers of
fnow perpetually fell. This, no doubt, muft be owing
to the great elevation of the country, and to the vah
frozen fpace over which the north wind blows uninter-
ruptedly from the pole, through the vah defarts of Si-
beria and Tartary, till it is hopped by tins formidable
wall.

The

472 Mr. stewards Account of

The Thibetians are of a fmaller fize than their
fouthern neighbours, and of a lefs robuft make. Their
complexions are alfo fairer, and many of them have even
a ruddinefs in their countenances unknown in the other
climates of the eaft. Thofe whom I faw at Calcutta ap-
peared to have quite the Tartar face. They are of a mild
and chearful temper; and Mr. bogle fays, that the
higher ranks are polite and entertaining in converfation,
in which they never mix either brained compliments or
flattery. The common people, both in Boutan and Thi-
bet, are cloathed in coarfe woollen fluffs of their own
manufacture, lined with fuch ikins as they can procure ;
but the better orders of men are dreffed in European cloth,
or China filk, lined with the fineft Siberian furs. The
ambaflador from the Deb Rajah, in his fummer-drefs at
Calcutta, appeared exactly like the figures we fee in the
Chinefe paintings, with the conical hat, the tunick of
brocaded filk, and light boots. The Thebetian who
brought the firft letter from the Lama was wrapped up
from head to foot in furs. The ufe of linen is totally
unknown among them. The chief food of the inhabi-
tants is the milk of their cattle, prepared into cheefe, but-
ter, or mixed with the flour of a coarfe barley or of peas,
the only grain which their foil produces; and even thefe
articles are in a fcanty proportion : but they are furnifhed

with

of the Kingdom of Thibet. 4.73

with rice and wheat from Bengal and other countries in
their neighbourhood. They alfo are fupplied with fifh
from the rivers in their own and the neighbouring pro-
vinces, falted and fent into the interior parts. They have
no want of animal food from the cattle, fheep, and hogs,
Which are raifed on their hills; and are not deftitute of
game, though I believe it is not abiindant. They have a
lingular method of preparing their mutton, by expoling
the carcafe entire, after the bowels are taken out, to the
Sun and bleak northern winds which blow in the months
of Auguft and September, without froft, and fo dry up
the juices and parch the Ikin, that the meat will keep un-
corrupted for the year round. This they generally eat
raw, without any other preparation. Mr. bogle was
often regaled with this dilh, which, however unpalatable
at firft, he fays, he afterwards preferred to their drelfed
mutton juft killed, which was generally lean, tough, and
rank. It was alfo very common for the head men, in the
villages through which he palled, to make him prefents
of lheep fo prepared, fet before him on their legs as if
they had been alive, which at firft had a very odd ap-
pearance.

The religion and political conftitution of this country,
which are intimately blended together, would make a
conliderable chapter in its hiftory. It fuffices for me to

Vol. LXVII. Q q q fay,

474 Mr. stewart’s Account of

fay, that at prefent, and ever fince the expnlfion of the
Eiuth Tartars, the kingdom of Thibet is regarded as
depending on the empire of China, which they call
Cathay; and there actually refide two mandarines, with
a garrifon of a thouiand Chinefe, at Lahaffa the capital,
to fupport the government; but their power does not
extend far: and in fa<ft the Lama, whole empire is
founded on the fureft grounds, perfonal affection and
religious reverence, governs every thing internally with
unbounded authority. Every body knows that the Delai
Lama is the great object of adoration for the various
tribes of heathen Tartars, who roam through the vaft
tradt of continent which llretches from the banks of the
Yolga to Correa on the fea of Japan, the moll extenlive
religious dominion, perhaps, on the face of the globe.
He is not only the fovereign Pontiff, the vicegerent of
the Deity on earth ; but, asfuperftition is ever the ftrongeft
where it is moft removed from its object, the more re-
mote Tartars abfolutely regard him as the Deity himfelf.
They believe him immortal, and endowed with all know-
ledge and virtue. Every year they come up from dif-
ferent parts, to worfhip and make rich offerings at his
fhrine; even the emperor of China, who is a Mantchou
Tartar, does not fail in acknowledgements to him in his
religious capacity, and actually entertains at a great

expe nee,

the Kingdom of Thibet. 475

expence, in the palace of Pekin, an inferior Lama, de-
puted as his Nuncio from Thibet. It is even reported,
that many of the Tartar chiefs receive certain prefents,
eonfifting of fmall portions of that, from him, which is
ever regarded in all other perfons as the molt humiliating
proof of human nature, and of being fubject to its laws,
and treafure it up with great reverence in gold boxes,
to be mixed occafionally in their ragouts. It is, how-
ever, but juftice to declare, that Mr. BOOLE ftrenuoufly
infills, that the Lama never makes fuch prefents; but
that he often diflributes little balls of confecrated flour,
like the pain benit of the Roman catholics, which the
fuperflition and blind credulitity of his Tartar votaries
may afterwards convert into what they pleafe. The or-
thodox opinion is, that when the grand Lama feems to
die, either of old age or of infirmity, his foul in fa<5t only
quits an actual crazy habitation to look for another
younger or better, and it is difcovered again in the body
of fome child, by certain tokens known only to the
Lamas or Priefts, in which order he always appears.
The prefent Delai Lama is an infant, and was difcovered
only a few years ago by the Tayfhoo Lama, who in au-
thority and fanclity of character is next to him, and con-
fequently, during the other’s minority, a efts as chief. The
Lamas, who form the mofl numerous as well as the mo ft

Q q q 2 powerful

476 Mr. STEWART’S Account of

powerful body in the ftate, have the priefthood entirely
in their hands ; and, befides, fill up many monaftic orders
which are held in great veneration among them. Celi-r
bacy, I believe, is not pofitively enjoined to the Lamas ;
but it is held indifpenfable for both men and women,
who embrace a religious life : and indeed their celibacy,
their living in communities, their cloyfters, their fervice
In the choirs, their firings of beads, their fafts, and their
penances, give them fo much the air of Chriftian monks,
that it is not furprizing an illiterate capuchin fhould be
ready to hail them brothers, and think he can trace the
features of St. Francis in every thing about them. It is
an old notion, that the religion of Thibet is a corrupted
Chriftianity; and even Father disederii, a Jefuit (but
not of the Ghinefe million) who vifited the country
about the beginning of this century, thinks he can re-
folve all their myfteries into ours; and aflerts, with a
true myftical penetration, that they have certainly a good
notion of the Trinity, fince, in their addrefs to the Deity,
they fay as often Konciok-oik in the plural as Konciok
in the lingular, and with their rofaries pronounce thele
words, Om, ha, hum. The truth is, that the religion of
Thibet, from whence-ever it fprung, is pure and fimple
in its fource, conveying very exalted notions of the Deity,
with no contemptible fyftem of morality; but in its

progrefs

the Kingdom of Thibet, 477

progrefs it has been greatly altered and corrupted by the
inventions of worldly men, a fate we can hardly regret in
a fyftem of error, lince we know that that of truth has
been fubjedt to the fame. Polygamy, at leaft in the fenfe
we commonly receive the word, is not in practice among
them ; but it exifts in a manner ftill more repugnant to
European ideas; I mean in the plurality of hufbands,
which is firmly eltablilhed and highly refpedted there.
In a country where the means of fubfifting a family are
not eafily found, it feems not impolitic to allow a fet of
brothers to agree in railing one, which is to be main-
tained by their joint efforts. In fliort, it is ufual in Thi-
bet for the brothers in the family to have a wife in com-
mon, and they generally live in great harmony and com-
fort with her; not hut fometimes little difienfions will
arife (as may happen in families conflituted upon dif-
ferent principles) an inftance of which Mr. bogle men-
tions in the cafe of a model! and virtuous lady, the wife
of half a dozen of the Taylhoo Lama’s nephews,, who
complained to the uncle, that the two youngeft of her
hulbands did not furnifh that fhare of love and benevo-
lence to the common Hock which duty and religion re-
quired of them. In lhort,. however ftrange this cultonv
may appear to us,, it is an undoubted fad! that it prevails
in Thibet in the manner I have defcrihed.

47 8 Mr. stewart’s Account of

The manner of beftowing their dead is alfo Angular :
they neither put them in the ground like the Europeans,
nor burn them like the Hindoos; but expofe them on
the bleak pinnacle of fome neighbouring mountain, to
be devoured by wild beafts and birds of prey, or wafted
away by time and the viciffitudes of weather in which
they lie. The mangled carcafes and bleached bones lyc
fcattered about; and, amidft this fcene of horror, fome
miferable old wretch, man or woman, loft to all feelings
but thofe of fuperftition, generally fets up an abode, to
perform the difmal office of receiving the bodies, affign-
ing each a place, and gathering up the remains when too
widely difperfed.

The religion of Thibet, although it be in many of its
principal dogmata totally repugnant to that of the Bra-
mins or of India, yet in others it has a great affinity to
it. They have, for inftance, a great veneration for the
cow ; but they transfer it wholly from the common fpe-
cies to that which bears the tails, of which I ffiall fpeak
hereafter. They alfo highly refpedt the waters of the
Ganges, the fource of which they believe to be in Hea-
ven; and one of the firft effects which the treaty with
the Lama produced, was an application to the governor-
general, for leave to build a place of worffiip on its
banks. This it may be imagined was not refufed; and,
7 when

the Kingdom of Thibet, 479

when I left Bengal, a fpot of ground was actually af-
figned for that purpofe, about two or three miles from
Calcutta. On the other hand, the Sunniaffes, or Indian
pilgrims, often vilit Thibet as a holy place, and the Lama
always entertains a body of two or three hundred in his
pay. The refidence of the Delai Lama is at Pateli, a vaft
palace on a mountain near the banks of the Barainpoo-
ter, about feven miles from L ah aha. The Tayfhoo

Lama has feveral palaces or caftles, in one of which Mr.
bogle lived with him five months. He reprefents the.
Lama as one of the moll; amiable as well as intelligent
men he ever knew; maintaining his rank with the ut-
moft mildnefs of authority, and living in the greateft pu-
rity of manners, without ftarchnefs or affectation. Every
thing within the gates breathed peace, order, and digni-
fied elegance. The caftle is of ftone or brick, with many
courts, lofty halls, terraces, and porticos; and the apart-
ments are in general roomy, and highly finifhed in the
Chinefe ftile, with gilding, painting, and varnifli. There
are two conveniencies to which they are utter ftrangers,
ftair- cafes and windows. There is no accefs to the. upper
rooms but by a fort of ladders of wood or iron ; and for
windows they have only holes in the cielings, with pent-
houfe covers, contrived fo as to fhut up on the weather-
iide. Firing is fo fcarce, that little is ufed but for culinary

purpofes ;

48o Mr. stewart’s Account of

purpofes ; and they truft altogether for warmth in their
houfes to their furs and other cloathing. The Lama, who
is compleatly converfant in what regards Tartary, China,
and all the kingdoms in the Eaft, was exceedingly inqui-
litive about Europe, its politics, laws, arts and fciences,
government, commerce, and military ftrength ; on all
which heads Mr. bogle endeavoured to fatisfy him, and
actually compiled for his fervice a brief flats of Europe
in the Hindoftan language, which he ordered to be tran-
flated into that of Thibet. The Lama being born at
Latack, a frontier province next Caflamire, is fully matter
of the Hindoftan language, and always converfed with
Mr. bogle in it; but the people, who are perfuaded he
underftands all languages, believed he fpoke to him in
Englifti, or, as they call it, the European tongue. The
Ruffian Empire was the only one in Europe known to
him : he has a high idea of its riches and ftrength, and
had heard of its wars and fuccefs againft the Empire of
Rome (for fo they call the Turkifh ftate); but could not
conceive it could be in any wife a match for Cathay.
Many of the Tartar fubjects of Ruffia come to Thibet;
and the Czar has even, at various times, fent letters and
prefents to the Lama. Mr. bogle faw many European
articles in his hands; pictures, looking-glafles, and
trinkets of gold, filver, and fteel, chiefly Engliih, which

he

tb? 'Kingdom of. Thibet, ' 48’ t

lie. had received that way, particularly^ graham’s re-
peating watch, which’, kkl been, xliifcly-’ as they . laid, . for
■tome time. While he was: there, feveral Mongols and
Galmucs arrived from. Siberia, with whom he converfed.

The city of Lab. ail a, which is the capital, is of no incon-
fiderable iize, and is reprefented as populous and fioit-
rilhing. It is the refidenee of the chief officers of go-
vernment, and of the Ghinefe mandarins and their fuite-.

It is alfo inhabited by Chinefe and Gaffemirian mer-
chants and artificers, and is the daily refort of number-
lefs traders from all quarters, who come in occafional
parties, or in ftated caravans. The waters of the Great
River, as it is emphatically called in their language, wafh.
its walls. Father duhalde, with great accuracy, traces
this- river, which he never fufpedts to be the Baram-
pooter, from its origin in the Gaffemirian mountains
(probably from the fame fpring which gives rife to the
Ganges) through the great valley of Thibet, till, turning
fuddenly to the fouthward, he lofes it in the kingdom of
Aflam; but ftill, with great judgement and probability of
conjecture, fuppofesit reaches the Indian feafomewhere
in Pegu or Aracan. The truth is, however, that it turns
fuddenly again in the middle of Aflam, and, traverfing
that country wefterly, enters Bengal towards Ranga-
matty, under the above-mentioned name, and thence
Vo L. LX VII, Rrr bending

48 a Mr. Stewart’s Account of

bending its courfe more foutherly, joins the Ganges, its
lifter and rival, with an equal, if not more copious,
ftream ; forming at the conflux a body of running frefh
water, hardly to he paralleled in the known world, which
difembogues itfelf into the Bay of Bengal. Two fuch
rivers uniting in this happy country, with all the beauty,
fertility, and convenience which they bring, well entitles
it to the name of the Paradife of Nations, always be*
flowed upon it by the Moguls.

The chief trade from Lahafla to Pekin is carried on
by caravans that employ full’ two years in the journey
thither and back again j which is not furprizing, when
we confider that the diftance cannot be lefs than two thou*
fend Engliih miles ; and yet it is to be-obferved, that an ex-
prefs from Lahafla reaches Pekin in three weeks, a cir-
cumftance much to the honour of the Chinefe police,
which knows to eftablifh fo fpeedy and effectual a commu-
nication through mountains and defarts for fo long away.
The trade with Siberia is carried on by caravans toSeling,
which is undoubtedly the Selinginfky of the Ruffian tra*
vellers on the borders of Baykal lake. And, this accounts
for air extraordinary fa<ft mentioned by bell;, that, on
the banks of the river of that name, he one day found
a man bufy in redeeming, from fome boys who were
angling,, the fifh they caught, and. throwing them into.

the

the Kingdom of Thibet. 483

the water again; and from this circumftance, and the
mark on his forehead, knew him to be an Indian, On
converting with him, he found his conjecture to be right.
The man told him, he came from Madrafs, had been two
years on his journey* and mentioned by name fome of
the principal Engiifh gentlemen there. This Indian, no
doubt, muft have travelled as a Faquier or Sunniaffy
through Bengal into Thibet, and from thence paffed
with the caravan to Selinginfky, where bell found him.
It is proper to remark, that the Indians have an admira-
ble method of turning godlinefs into great gain, it being
ufual for the Faquiers to carry with them, in their pil-
grimages from the fea-coafts to the interior parts, pearls*
corals, fpices, and other precious articles, of fmall bulk*
Which they exchange on their return for gold-duft,
mulk, and other things of a firnilai' nature, concealing
them eafily in their hair and in the cloths round their
middle, and carrying on, confidering their numbers, no
inconfiderable traffic by thefe meanst The Gofleigns are
alfo of a religious order, but in dignity above the F aquiers ?
and they drive a more extenfive and a more open trade
with that country >

A particular account of the commerce would be fo-
reign to the purport of this letter; but, as it would leave
the information which I wifh to convey very incom-

R r r a pleat,

484 Mr. STEWART’S Account of

pleat,, did i not mention the four.ces from which this
country, fo apparently poor and unfruitful, draws afup-
ply of the foreign articles of convenience and luxury,
which I have occafi.on.aliy faid they : poffefs t I fliall juft
obferve, that,.befides their lefs traffic with their neigh-
bours in horfes, hogs, rock -fait, coarfe cloths, and other
articles, they enjoy four ftaple. articles, which are fuffi-
cient in themfelves to procure every foreign commodity
of which they lfand in need; all of which are natural
productions, and deferve to be particularly noticed. The
firft, though the leaf! confiderable, is that of. the cow-
tails, fo famous all over India, Perfia,.and.the other, king-
doms of the Eaft. It is produced by a fpecies of cow
or bullock different from what I believe is found in any
other country. It is of a larger fize than, the common
Thibet breed, has fhort horns, and no-hump on its back.
Its. ficin is covered with whitilh hair of a filky appear-
ance ; but its chief Angularity is in its tail, which fpreads
out broad and long, with flowing' hairs, like that of a
beautiful m are, but much finer and far more gloffy. Mr.
roole fent down, two of this breed to Mr. Hastings,
but they died before they reached Calcutta. The- tails fed'
very high, and are ufed, mounted on filver handles, for
Chrowras, or brufhes, to chafe away the flies ; and nft
map of cQnfequence, in India ever goes out, or fits in>

d form

the Kingdom of Thibet. 48'5,

form at home, without two Chowrawbadars, or hr u fliers,
attending him, with i'uch inftruments in their hands.

The next article is the wool from which the Sharif,
the moll delicate woollen manufacture in the- world, fo
much prized in the Eaft, and now fo well known in Eng?
land, is made. Till Mr. bogle’s journey our notions on
that fubject were very crude and imperfeCt. As the
Shards all come from Caffemire, we concluded the ma-
terial from which they were fabricated to be alfo of that
country’s growth, it was faid to be the hair of a particu-
lar goat, the fine under hair from a camel’s bread:, and a
thoufand other fancies but we now know it for certain
to be the produce of a Thibet flreep. Mr. Hastings had
one or two of thefe in his paddock when 1 left Bengal.
They are of a fmall breed, in figure nothing differing
from our flieep, except in their tails, which are very
broad; but their fleeces, for the finenefs, length, and

beauty of the wool, exceed all others in the world. The

*

Caifemirians engrofs this article, and have factors efta-
blifhed for its purchafe in every part of Thibet, from
whence it is fent to, Caflemire, where it is worked up,
and becomes a fource of great wealth to that country, a$
well as it is originally to Thibet-

Mufk is another of their ftaple articles, of which it

will be needlefs to fay much, as the nature, quality, and

jl . valuer.

486 Mr. stewart’s Account of

value of this precious commodity are fo well known in
Europe. I ffiall only remark, that the deer which pro-
duces it is common in the mountains ; but being excel*
lively fliy, and frequenting folely the places the molt
wild and difficult of accefs, it becomes a trade of great
trouble and danger to hunt after. We have the muik
fent down to Calcutta in the natural bag, not without
great rifle of its being adulterated; but Hill it is far fupe-
rior to any thing of the kind that is to be met with in
fale in Europe.

The laft of the articles which I reckon llaple is gold,
of which great quantities are exported from Thibet. It
is found in the fands of the Great River, as well as in
moll of the fmall brooks and torrents that pour from the
mountains. The quantity gathered in this manner,
though conliderable with refpedt to national gain, pays
the individual but very moderately for the labour be-
Itowed on it. But, belides this, there are mines of that
metal in the northern parts, which are the referved pro-
perty of the Lama, and rented out to thofe who work
them. It is not found in ore, but always in a pure me-
tallic ftate (as I believe it to be the cafe in all other mines
of this metal) and only requires to be feparated from the
fpar, Hone, or flint, to which it adheres. Mr. Hastings
had a lump fent to him at Calcutta, of about the lize of

a bullock’s

the Kingdom of Thibet. 48-7

a bullock’s kidney, which was a hard flint veined with
folid gold. He caufed it to be fawed in two, and it was
found throughout interlarded (if I may be allowed the ex-
preflion) with the pureft metal. Although they have
this gold in great plenty in Thibet, they do n-ot employ
it in coin, of which their government never ftrikes any ;
but it is ftill ufed as a medium of commerce, and goods
are rated there by the purfe of gold- dull, as here by mo-
ney. The Chinefe draw it from them to a great amount
every year, in return for the produce of their labour
and arts.

I could with to add to this account fomething refpedt-
ing the plants and other botanical productions of this
country ; but I would not prefume to offer any thing but
what is authentic and exaCt, as far as my knowledge
goes. Mr. bogle will no doubt be able to fatisfy the
learned in that branch, reflecting many things of which
I have at prefent no information. He fent down to Cal-
cutta many feeds, grains, kernels, and fruits, part of
which only arrived fafe. Of the laft I tailed feveral, they
were chiefly of the European forts, fuch as peaches,
apples, pears, 8cc. and therefore more defirable for us in
Bengal; but they were all to me infipid and bad.

I am now, sir, to clofe thefe remarks with craving
your forgivenefs for having thus flarted a new fubjeCl of

6 curioiity.

4#8 stivWa tit's 4ccmnt vf

curiofity, without the means of giving more com pleat
light concerning it. Time and opportunity may put more
in my power on my return to India. In the mean time, I
hope the Society will accept as a rarity, the tranflation of
the original letter which the Tayfhoo Lama wrote to Mr.
Hastings, by -the envoy whom he fent to foiicit a peace
for the Deb. Rajah. It came into my hands in the courfe
of my office, and by the permiffion of the Governor
general I retained a copy.

The original is in Perllan, a language which the Lama
was obliged to employ, that of Thibet, although very
elegant and expreffive, as it is Laid, being totally unin-
telligible in Bengal. A letter under the fanclion of a
character fo long talked of in the weftern world, but fo
little known, alone renders it an objedt of curiofity; but,
when it is found to contain l'entiments of juftice, bene-
volence, and piety, couched in a fimple ftyle, not with-
out dignity, and in general exempt from the high-flown
compliments and ftrained metaphors fo common among
the other people of the Eaft, I have no doubt of its
being received with approbation ; at any rate, it will ferve
as a fpecimen of the way of thinking and writing among
a people whofe country and manners I have made the
fubjedt of the foregoing fketch.

'Tranflation

the Kingdom of Thibet,

489

Ir {inflation of a Letter from the Tayfhoo Lama to Mr.
Hastings, Governor of Bengal, received the 29th of
March, 1774*

THE affairs of this quarter in every relpeft flouriftr:
I am night and day employed for the increafe of your
happinefs and profperity. Having been informed, by
travellers from your quarter, Of your exalted fame and
reputation, my heart, like the bloffom of fpring, abounds
with fatisfa&ion, gladnefs, and joy. Praife God that the
ftar of your fortune is in its afceniion. Praife him, that
happinefs and eafe are the Turrounding attendants of
myfelf and family. Neither to moleft or perfecute is
my aim : it is even the charafteriftic of our fed. to de-
prive ourfelves of the neceffary refrefliment of deep,
fhould an injury be done to a Angle individual; but in
juftice and humanity, I am informed you far furpafs us.
May you ever adorn the feat Of juftice and power, that
mankind may, in the fhadow of your bofom, enjoy the
bleftings of peace and affluence ! By your favour I am
the Rajah and Lama of this country, and rule over a
Vo L. LXVII, S f f number

49© Mr. stewart’s Account of

number of fubje&s; a particular with which you have
no doubt been acquainted by travellers from thefe parts.
I have been repeatedly informed, that you have been
engaged in hoftilities againft the Dah Terria, to which
it is faid the Dah’s own criminal conduit, in committing
ravages and other outrages on your frontiers, gave rife.
As he is of a rude and ignorant race, paft times are not
deftitute of the like mifconduit which his avarice
tempted him to commit. It is not unlikely but he has
now renewed thofe inftances, and the ravages and plun-
der which he may have committed on the fkirts of the
Bengal and Bahar provinces, have given you provocation
to fend your vindictive army againft him. However, his
party has been defeated, many of his people have been
killed, three forts have been taken from him, and he has
met with the punifhment he deferved. It is as evident
as the Sun that your army has been victorious ; and that,
if you had been defirous of it, you might in the fpace of
two days have entirely extirpated him, for he had not
power to refill: your efforts. But I now take upon me to
be his mediator ; and to reprefent to you, that, as the faid
Dah Terria is dependant upon the Dalai Lama, who
rules in this country with unlimited fway (but, on account
of, his being in his minority, the charge of the govern-
ment.

the Kingdom of Thibet. 49 j

ment, and adminiflration for the prefent is committed to
me) ihould you perfift in offering farther moleftatioir to
the Dah^ country, it will irritate both the , kama and. all
his fubjefts againft you. Therefore, from a regard to
our religion and cuftoms, I requeft you will ceafe. all
hoftilities againft him; and in doing this you will confer
the greateft favour and friendfhip upon me. I have re-
primanded the Dah for his paft conduit ; and I have ad-
moniflied him to defift from his evil practices in future,
and to be fubmiflive to you in all things. I am per-
fuaded he will conform to the advice which I have given
him; and it will be neceffary that you treat him with
companion and clemency. As to my part, I am but a
Faquier ^ ; and it is the cuftom of my feel', with the rofary
in our hands, to pray for the welfare of mankind, and for
the peace and happinefs of the inhabitants of this coun-
try ; and I do now, with my head uncovered, intreat that
you may ceafe all hoftilities againft the Dah in future.
•It would be needlefs to add to the length of this letter,
as the bearer of it, who is a Gofeign^, will reprefent to

( a ) The original being in Perfiad, this Wofd is ufed, which can only be
applied with propriety to a per fen of the MulTulman faith : here it can only
mean a religious perfon in general. Perhaps monk would have been the belt
tranflation.

(b) This means a religious perfon of the Hindoo fed,

S f f 2

you

49‘J iWh stewart’s Account, Me.

you all particulars ; and it is hoped you will comply there-
with.!. la this country, worship of the Almighty is the
profeflion of all. We poor creatures are in nothing equal
to you; having, however, ,a few things in hand, I fend
them to you by way of remembrance, and hope for your
acceptance of them*

L 493 3

XXVI.- Of the Degrees and Quantities of Winds requijite
to move the - heavier- Kinds -of Wind Machines, In a
Letter from John Stedman, M. D. Fellow of the Royal
College of Phyficians- at Edinburgh, to the Reverend
Samuel Horfley, LL.D. Secretary to the Royal Society . .

s I R,

Edinburgh,
March 27, 1777,

Read Apr. 24, \r I "'HE irregularity and uncertainty of winds
in this country have been found a con-
liderable difcouragement to ere£t wind machines. It
hath frequently happened, that the proprietors of coal
and other works, after having reared thefe kinds of en-
gines, and having found them inefficient for the in-
tended work, have been obliged to open mines, or to
erect fire machines. This is chiefly owing to the under-?-
takers reckoning upon more winds of a efficient power,
to move thefe machines, than we commonly have in this
country. .

Thefe machines are rarely erected with us, unlefs
where a confiderable moving power is neceflary. This
is always the cafe where the larger kind of pump-work
is to be kept in motion, or where water is to be extracted

from.

494 Br. stedman on the Degrees and Quantities
from deep pits. Having enquired of many people con-
cerned in fuch works, what may be the- proportion of
time in which wind machines may be kept in motion, to
that in which they cannot move from a defeCt of wind,
I found thefe people differing widely in their conjectures.

Having, however, met with one gentleman of ob-
fervation and accuracy, who had eredted a wind ma-
chine for draining his coal ; he told me that, by the belt
computation he had been able to make, he never could
depend upon more than fifty-three or fifty-four hours of
wind fufficient for moving that machine, in a week,
taking the year round. This is below what is commonly
believed to be the proportion ; but, fo far as this can be
rated by an eftimate in the following manner, it will be
found to be much about what may be depended upon
for the heavieft kinds of machines ; flill making allow-
ance for the differences of expofures, and for the ftrength
and frequency of winds in one part of the country more
than in another. We may here take notice of a circurn-
ftance favourable to the draining of coal-pits; that is,
that the periods of the year in which the greateft quan-
tities of rain fall, are like wife obferved to abound with
winds of the higher degrees. This feldom fails to hold
in hilly countries, and particularly iji thofe of high lati-
tudes ; that is, where the differences of heats in fummer

and

7

of Winds requijite to move heavy Wind Machines. 49 5
and of colds in winter are very confiderable. The periods
of the year here meant will generally be found to fall
near the Equinoxes.

The only method of bringing the matter to a proper
eftimate is, by comparing the quantities of winds fuffi-
cient for moving thefe machines, with thofe of winds be-
low that degree, and calms. This computation can only
be drawn from journals in which the degrees of winds
are noted. In the meteorological regifter of the Medical
E flays of the Edinburgh Society, there is a column of
winds, and four degrees are noted. This divifion is fuf-
ficient for the purpofes for which that regifter was in-
tended ; but, when we confider the wind as a power
adting upon machines, that number of degrees will be
found too fmall. ,

Thus, from the fecond in that regifter to a hurricane,
there is but one intermediate degree. As the fecond de-
gree, which is very moderate, is infuffxcient for moving
thefe machines ; the third is more than juft enough for
that purpofe. A degree, therefore, which is a mean be-
twixt thefe two, will be found to be the loweft that is
fufticient for. moving machines of the heavier kinds, par-
ticularly fuch as are ufed for pumping water out of
coal-pit s» ,

Thefe-

496 Dr. s ted man on the Degrees and Quantities

Thefe tljree degrees of wind, that is the fecond and
third of the Edinburgh regiiler, and an intermediate de-
gree, are very diftinguifhable even by the fenfes, and
without the alii fiance of any inllrument, by thofe who
are attentive and have been accuftomed to make obfer-
vations of this nature.

To afcertain proportions of this nature, a longer term
of years would have been more fat is factory ; but, in cafe
others Ihould afterwards purfue this kind of computa-
tion, the proportions are digefted in two. tables at the end
of this elfay, and may be confulted occafionally.

In making up thefe tables, viz. one of the fecond de-
gree and above, and the other of the third and upwards,
hurricanes are included, though that degree of wind be
too high for any machine. But, as the obfervations were
taken twice in twenty-four hours, and as winds fufficient
to move thefe machines may be fuppofed to have hap-
pened fometimes between the times of obfervation,
though at thefe times the wind might have been below
the mean; to compenfate this defect, hurricanes are in-
cluded in the computation.

From thefe tables then we have the following propor-
tions of the two degrees of winds and upwards, to thofe
below; and likewife of the mean betwixt thofe two
degrees.

Winds

of Winds requijite to move heavy Wind Machines. 497

^ I |2 vr- J A . r ’ r • • ' ' " .% f ,

> Days.

degree and upwards in')

> 4.283

Winds of the fecond
each week,

Calms and winds below the fecond degree,

Winds of the third degree and upwards,
Calms and winds below the third degree,

Winds of a mean proportion between the two
preceding degrees, — ■ —

Calms and winds below the mean degree,

)

2.717

0.902

6.098

2.592

4.408

The proportion of thefe winds in the year comes out
in weeks and fractional parts thus :

Weeks.

Winds of the fecond degree and upwards in
the year, ■ — • — ■ —

Calms and winds below the fecond degree,

Winds of the third degree and upwards,
Calms and winds below the third degree,

Winds of a mean proportion between the two
preceding, — — —

Calms and winds below the mean, —

3i-9°3

20.239

6.719

45-423

19.307

2.83

From this computation we have 2.592 days in a week,
or 19,307 weeks in a year, in which wind machines of
Vol. LXVII. T t t

the

498 Dr. stedman on the Degrees and Quantities
the heavier kinds, and of confiderable fridtion, may he
fuppofed to he kept in motion; which, to the times
wherein they cannot go, is as j o to 17.

It may he obferved, that the refiftance to the machine,
or its weight and fridtion, being diminifhed, though in a
fmall degree, will add confiderably to the frequency and
length of times in which it can go ; fince it often happens
that there are winds immediately below the lowed: de-
gree in the preceding eftimate, fufficient to keep the
lighter machines in motion. Hence thofe who have
machines which are not abfolutely of the heavieft kind,,
will be apt to conclude this computation erroneous. Be-
ll des, there are few who make allowance for, or attend
to, the univerfal law which obtains in mechanics, that in
larger machines, their power doth not increafe in a pro-
portion fo high as their bulk and the refiftance ariling
from their fridtion.

Computations of this nature, if carried on for a fuffi-
cient length of time, might be of Ibme ufe in regulating
infurances, or in pointing out the rilks of nautical ad-
venturers, when made in the fame climates with the
calculation of winds.

Here I fliould have concluded ; but having, after writing
what is above, committed thefe tables and obfervations
to the examination of a learned member of your So-
7 ciety,

of Winds requifite to move ■ heavy Wind Machines. 499
cietv, much converfant in thefe matters, I had the fatif-
faCtion to find that he thought them worthy to be
communicated to the Royal Society ; but remarked, that
the materials, which I had proceeded upon, were not fo
applicable to the purpofe as could have been wifhed.
He thinks, that the degrees of winds, being only dif-
tinguifhed into four in the journals from whence thofe
tables have been compiled, are much too few to take in
thofe of the weaker kind, that will however turn well-
conftructed wind-mills. Indeed I regretted that the table
from which I made my eftimate contained fo few de-
grees; but it was for that reafon I calculated an inter-
mediate degree between the fecond and the third of our
meteorological regifter. Now as all the degrees above
that intermediate degree are fufficient to move the hea-
vieft machine, and the degrees below it infufficient for
that purpole, fo far as I have been able to obferve, it
comes to be the fame as if the table, from which I made
the eftimate, had confifted of eight degrees, fuppofing a
mean proportion to be found between the other degrees :
thus, o, j, 1, iy, 2, 2y, See. this laft number 2y, being
the loweft degree which I find fufficient for the heavieft
machines, would have been 5, had thefe fractional parts
been integers in the table, fo that the higheft degree, in-
ftead of 4 would have been 8. The mean, therefore,

T t t 2 between

500 Dr. stedman on the Degrees and Quantities
between i and 3 being found, will, if I miftake not,
anfwer the preceding objection.

This worthy member, at the end of his obfervations,
fays, a mill fo conftru<5ted may be expected to go the half
of the year; that is, I prefume, a wind-mill conftrudted
in the neateft and molt ingenious manner. But this, I
have reafon to believe, is far from being the cafe with
wind-mills in this country, they being for the molt part
clumfy. I doubt not but wind-mills, the conftrudtion of
which this ingenious gentleman hath directed, though
of the fame fize and confiding of the fame numbers
with thofe I have feen here, will neverthelefs be moved
by a lower degree of wind, and confequently will go a
greater proportion of time, though they have the fame re-
fiftance to overcome as others lefs artificially conftrudled.
Indeed the fame wind machine, as is well known, will
require a degree of wind confiderably higher when
its joints are dry or become gummy, than when they are
fufficiently greafed. In my eftimate I have all along had
an eye to the wind machines which have the greateft
refiftance to overcome, and confequently the machines
themfelves of the largeft kind. But when, the learned
gentleman fuppofes a machine to go one half of the
year, : he may perhaps not underftand one abfolutely of

the

of Winds requijite to move heavy Wind Machines. 501
the largeft kind. Now as the powers of limilar ma-
chines, but of different magnitudes, are as their cubes,
but the refiftance ariling from their weight and friction
as the fourth power; it follows, that a fmall difference in
the fize of two or more wind machines will require con-
fiderable differences in the winds neceffary for their
movements.

I am, See.

TABLE

5 o a Dr, stedman on the Degrees and Quantities

TABLE I.

Shewing the Proportion of winds of the fecond degree
and upwards, to thofe of the firft and below, for five
years.

Proportion
;f*winds of
[he zd degree
to thofe of
the firft, &c.
n 1731 and
1732.

>roportion,
tec. in 1732
md 1733*

Proportion,
&c. in 1733 1
and 1734.

Proportion, 1
See. in 1734 :
and 1735. 5

Proportion, 1
kc. in 1735 1
\nd 1736.

Sum ot each
month for
five years.

Winds.

O

Pf>

3

CO

Vi

l —

Winds, i

Calms,

&c.

Winds.

O

P? *L

p g

CO

Winds.

c
Pf* 5L

0 s

Winds.

Calms,

&c.

Winds.

1

r
p? **
° 5*

CO

June

16

44

46

14

26

34

24

41

*9

153

147

July

7

55

44

18

39

23

29

33

43

*9

162

148

A u gull

8

54

27

35

20

42

28

34

47

J5

13°

180

September

30

30

24

36

40

20

34

26

34

26

162

138

O&ober

26

36

J3

49

36

26

31

31

35

27

141

169

November

39

21

18

42

51

9

16

44

33

25

157

141

December

43

29

33

33

24

46

16

41

21

197

1 *3

January

55

7

43

l9

35

27

53

4

45

*7

236

74

February

45

H

46

10

48

8

47

9

42

16

228

56

March

39

23

50

12

40

22

53

9

46

16

228

82

April

44

16

34

26

42

18

46

►

46

14

212

88

May

54

8

28

34

36

26

55

7

57

5

230

80

Sum of years *1
and months, J

406

326

> 402

328

45i

279

263

1 51°

22c

> 2236

1416

TABLE

of Winds requi/ite to move heavy Wind Machines. 503

TABLE II.

Shewing the proportion of winds of the third degree
and upwards, to thofe of the fecond and below, for
five years.

Proportion,
of winds of
the 3d degree
to thofe of
the firft, &c.
in 1731 and
1732*

Proportion,
& c. i 1732
and 1733.

Proportion,
&c. in 1733
and 1734.

Proportion,
&c. in 1734
and 1735.

Proportion;,
&c. in 1735
and 1736.

Sum of each
month ;
five yaars.

Winds.

Calms,

&c.

Winds.

O
P? EL

P 5

CD

Winds.

8° £L

O p

CD

V

Winds.

n

9? EL
P 5

CD

s*

Winds.

■ O

Pf EL

P 3

CD

V#

Winds.

C
P? EL
P 3

CD

Vi

June

1

59

-

60

3

57

2

58

1

59

7

233

July

I

61

7

55

1 1

5T

5

57

1

61

25

285

Auguft

-

62

62

8

54

3

59

-

62

48

252

September

1 3

47

9

51

10

50

8

52

8

52

1 1

299

October

9

53

1

61

12

5o

1 1

5i

2

60

35

275

November

1 1

49

8

52

l9

4i

2

58

6

54

46

254

December

17

45

4

58

12

5°

9

53

4

58

46

264

January

5

57

1 1

5i

9

53

18

44

6

56

49

261

February

24

34

20

36

24

32

12

44

7 ,

5i

87

*97

March

12

5°

10

52

18

44

6

56

5

57

5i

259

April

9

51

5

55

9

5i

8

52

5

55

36

264

May

7

55

-

62

9

53

10

52

4

58

3°

280

Sum of years J
and months, j

109

623

75

6S5

144

586

94

636

49

683

47i

3i83

XXVII. Be-

[ 5°4 1

XXVII. Defer iption of the Jefuits Bark 'Tree of Jamaica
and the Caribbees. By William Wright, M. D. Member
of the Philofophical Society of America, and Surgeon-
general in Jamaica. Communicated by Jofeph Banks,
Ffquire , F. R. S.

Read April 24, t H ^ HIS fpecies ot Jeluits bark grows on
1777. I

ftony lands near the fea-fhore, in the
parilhes of St. James and Hanover, on the north-lide of
Jamaica; and I found one fmall tree, at a little diftance
from the fort, at Martha Brae in the parifh of Trelawny.
The tree is called the Sea-fide Beech, and rifes only to
twenty feet. The trunk is not thick in proportion, but
hard, tough, and of a yellowifh- white colour in the infide.
The branches and leaves are oppofite; the leaves are of a
rufty green, and the young buds of a blueifh green hue.
It blofloms in November, and continues in flower till Fe-
bruary, having on the fame tree or fprig, flowers and
ripe pods. The flowers are of a dufkifh yellow colour,
and the pods black: when ripe they fplit in two, and are,
with their flat brown feeds, in every refpect fimilar to

thofe

Dr. wrjght’s Defcription , &c. 505

thofe of the Cinchojia officinalis as depidted in a plate fent
out by Mr. banks.

The bark of this tree in general is fmooth and grey
on the outfide, though in feme rough and fcabrous.
When well dried, the infide is of a dark-brown colour.
Its flavour at firit is fweet, with a mixture of the tafte of
horfe-radifh and of aromatics of the Eaft; but, when
fwallowed, of that very bitternefs and aftringency which
charadterifes the Peruvian bark. It yields thefe qualities
ftrongly to water both when cold and in decodtion. Half
an ounce, boiled from two pounds to one pound of water,
made as ftrong a decodtion as three times its weight of the
Cinchona vera. The colour was brown, but not turbid.

I have had many opportunities of trying its effedts,
efpecially in remittents, which are the moft common
and fatal fevers in thefe climes. A vomit or gentle
purge, if neceflary, was firft given; and then imme-
diately this bark fo foon as they operated. I obferved
that it ftrengthened the ftomach, checked retching and
vomiting, corredted morbid humours in priina via, and
conquered fpeedily the difeafe. My fuccefs in fuch a
dangerous malady leaves not a doubt on my mind, but
that it will prove equally efficacious in every other cafe
where a tonic and antifeptic medicine is indicated.

Vox. LXVII. U u u

C I N-

506 Dr. wright’s Defer iption, Me.

s

CINCHONA J AMAICENCIS, fetl CARIBBEAN A,

cinchona caribAlA, Linn. Spec. Plant. 245.

fol. ovata, integerrima, acuta, enervia, oppofita.

flor. iingulares, axillares.

cal. Perianthium monophyllum, fuperum, quinque-
fidum, minimum, periiilens, campanulatum, obfo-
letiflime quinquedentatum.

cor. monopetala, infundibiliformis. Pubus cylindraceus,
longiffimus : Limbus quinquepartitus, tubo equa-
lis: Laciniis ovatis, oblongis, reflexis, quandoque
pendulis.

stam. Fiiamenla quinque, filiformia, eredta e medio tubi,
longitudine corollce. Anther ce longiffimae, obtufae,
erect a; fupra bafin exteriorem, affixae in fauce corollae.

caps, bipartibilis in duas partes diffepimento paralello,
latere inferiore dehifeens.

sem. plurima, compreiTa, marginata, oblonga.

Philos, 'frans. Vol.JLX.VJI. Tab. A’.p.joO' .

C 5°7 ]

XXVIII. Defer iption and Ufe of the Cabbage-bark ’fret
of Jamaica. By William Wright, M. D.; commu-
nicated by Richard Brocklefby, M. D. F. R. S-

Read May i, ^TT^HE Cabbage-bark tree, or Worm-bark

I777. i

tree, grows in moft parts of Jamaica,
and particularly abounds in the low Savannahs of St.
Mary and St. George. It rifes to a con fider able height,
but no great thicknefs, fending off branches towards the
top of a ftraight, fmooth trunk. The leaves are, when
young, of a light-green hue; when full-grown, of a
dark-green colour; and before they drop, of a rufty ap-;
pearance.

The flower-fpike is long and beautifully branched.
The flowers are numerous ; their calyces of a dark pur-
ple ; their petals of the colour of the pale-rofe ; the nec-
taria muft contain much honey, as thoufands of bees,
beetles of various kinds, butter- flies, and humming-birds,
are continually feeding thereon.

The pericarpium is a green, hard fruit, of the fixe of
the fmaller plumb. The fkin is of the thicknefs of a
crown-piece ; and taftes very auftere. The kernel is
covered with a brown fkin like that of other nuts ; it is
Very hard, and taftes aftringent.

U u u a

The

508 Dr. wright’s Defcription of

The wood is hard, and takes a good polifh. It is
however fit only for rafters or other parts of fmall build-
ings ; but this tree i3 valued chiefly for its bark, which
externally is of a grey colour, and the infide black and
furrowed.

Freih cabbage-bark taftes mucilaginous, fweet, and
infipid. Its finell, however, is rather difagreeable, and it
retains it in the decoftion ; hence by fome called the
bulge-water tree.

Mr. peter duguid', formerly of this ifland, feem's to
have been the firft that gave any account of the virtues
of this bark, in the Edinburgh Effays, Phyfical and Li-
terary, vol. II. The experiments he promifed have never
yet appeared. It is certain it has powerful effects, and its
anthelmintic quality is eftablifhed by the experience of
feveral ages. It is at prefent in general ufe here, and
begins to be known in Europe. No defcription having yet
appeared, I have fupplied that defect as far as my abi-
lities in Botany reached. It remains now to proceed
to its exhibition, and the purpofes it is meant to anfwer
as a medicine.

Cabbage-bark may be given in different forms ; as in.
decoction, fyrup, powder, and extract. I have ufed them
all, and fhall fpeak of them feparately.

a,.

The:

the Cabbage-bark "Tree of Jamaica. 509

The deception. Take frelh-dried or well-preferved
cabbage-bark, one ounce. Boil it in a quart of water, over
a flow fire, till the water is of an amber colour, or rather
of deep coloured Madeira wine ; ftrain it off, fweeten it
with fugar, and let it be ufed immediately, as it does not
keep many days.

Syrup of Cabbage-bark. To any quantity of the
above decoction add a double portion of fugar, and make
a fyrup. This will retain its virtues for years.

The extract of cabbage-bark is made by evaporating
the ftrong decoition in balneo maria to the proper con-
fluence ; it muft be continually ftirred, as otherwife the
refinous part rifes to the top, and on this probably its
efficacy depends.

The powder of well-dried bark is eafily made, and
looks like jallap, though not of equal fpecific gravity.

This bark, like moft other powerful anthelmintics,
has a narcotic effeit; and on this account it is always
proper to begin with fmall dofes, which may be gra"
dually increafed till a naufea is excited, when the dofe for
that patient is afcertained. But by frequent ufe we can
in common determine the dofe, though we ehufe to err
rather on the fafe fide.

A ftrong healthy grown perfon may, at firft, take four
table fpoonfuls of the decoition or fyrup, three grains
of the extrait, or thirty grains of the powder for a dofe.

A- youthr

510 Dr. wright’s Defcription of

A youth, three table fpoonfuls of the decodtion or fy-
rup, two grains of extradt, or twenty grains of powder.

A perfon of ten years of age, two table fpoonfuls of
the decodtion or fyrup, one grain and a half of extra#,
or fifteen grains of the powder.

Children of two or three years old, a table fpoonful of
the decodtion or fyrup, one grain of extradt, or ten grains
of the powder. Children of a year old, half the quantity.

Thefe may he increafed, as above oblerved, till a nau-
fea is excited, which will depend on the ftrength, fex,
and habit of body of the patient.

Care muft be taken that cold water be not drank during
the operation of this medicine, as it is in this cafe apt to
occafion ficknefs, vomiting, fever, and delirium. When
this happens, or when an over large dofe has been given,
the ftomach muft be wafhed with warm water : the pa-
tient muft fpeedily be purged with Caftor-oil and ufe
plenty of lime-juice beverage for common drink; vege-
table acid being a powerful antidote in this cafe, as well
as in an over dofe of -opium.

The decodtion is what is moftly given here, andfeldom
fails to perform every thing that can be expected from
an anthelmintic medicine, by deftroying worms in the
inteftines, and bringing them away in great quantities.
55y frequent ufe, however, thefe animals become famfe

liarized,

the Cabbage-bark Tree of Jamaica. 5 1 1
liarized, and we find it neceflary to intermit it, or have
recourfe to others of inferior merit.

The writers of the Edinburgh Medical Commentaries
take notice, that the decoflion of cabbage-bark always
excites vomiting. We find no fuch effect from it here,
and may account for it by their receiving it in a mouldy
ftate. A fyrup, therefore, is given there with better ef-
fect, They obferve alfo that it has a diuretic virtue,
which we have not taken notice of here.

This bark purges pretty brilkly, efpecially in powder,
thirty or forty grains working as well as jallap by ftool;
but in this way it does not feem to kill worms fo well as
in decodlion.

Five grains of the extract made a ftrong man fick, and
purged him feveral times j but, by frequent ufe, he took
ten grains to produce at length the fame effect.

It mull: not be concealed that fatal accidents have hap-
pened from the imprudent adminiftration of this bark,,
chiefly from over-doling the medicine. But this cannot
detract from the merit of the cabbage-bark, fince the belt
medicines, when abufed, become deleterious ; . and even
our bell aliments, in too great quantity, prove deftrucSlive.
Upon the whole, the cabbage-bark is a moll valuable
remedy, and I hope will become an addition to the ma-
teria medica ..

U u u 4

GEOFfRjEA

5 1 2, Dr. wright’s Defcription , &c.-

6 E OFFR£A J A M A I C E N C I S I N E R M I S.

eol. oppofita, oblongo-ovata, ternata, acuminata, fu-
perne glabra, inferne enervia, petiolis brevibus.
cal. Perianthium monophyllum, campanulatum, le-
viffime quinquepartitum, laciniis ovatis, brevibus.
cor. papilionacea : Vexilluni fubrotundum, concavum:
Ahe obtufe, concavae, longitudine vexilli. Carina
ovata, patens, in duabus partibus leviffime divifa.

ST AM. diadelpha, decern, filiformia, in calyce infertaj .

longitudine alarum. Anther ce fubrotundae.
fist, fubulatum, filiforme. Stigma nullum. Germen
ovato-oblongum, compreffum.
per. Drupa fub-ovata, magna.

SEM. Nux fub-ovata, fub-lignea, fulco utrinque longi-
tudinali, bivalvis.

The botanical reader will fee liow nearly this agrees
with the Geoffraa fpinofa of linnalus. The Genera o£
plants are fufficiently multiplied, and it was thought beft
to make this a fpecies only.

-Philos : Trans : Vol. IjXVH Tah. JPp. .

Geoffrvea ® /amaicensis

'

«

’

-

’

[ 5T3 ]

XXIX. Obfervations made in Savoy, in order to aj certain
the height of Mountains by means of the Barometer ;
being an Examination of Mr. De Luc’s Rules , deli-
vered in his Recherches fur les Modifications de 1’At-
mofphere. By Sir George Shuckburgh, Bart. F. R, S.

Eead May 8 and 15, the courfe of my tour into Italy in
2 7 7 7» h

“*■ the years 1775 and 1776, I made
fome ftay at Geneva; which being in the neighbour-
hood of the Alps, and on that account a convenient
home, induced me to make fome obfervations upon
thofe mountains, which have been defervedly objects of
attention to the molt incurious traveller. I was particu-
larly defirous of verifying the experiments with the ba-
rometer, in taking heights of different fituations; a
method that has been long known to the ingenious,
though but rarely praitifed, and capable of but little
precifion till within thefe few years ; and perhaps at pre-
fent not fo generally known as the convenience and
utility of the method feems to require. I had provided
myfelf with a confiderable collection of inftruments, or
a kind of portable pbilofophical cabinet, which I had had

Vol. LXVII.

X x x

made

514 Sir george shuckburgh^s Obfervations
made exprefsly in London and Paris, in order to make
fuch experiments as might prefent themfelves to me en
courranf, and which, either from want of acquaintance
with the fubjedt, want of time, or want of money, be-
come rarely the objedt of travellers; but remain wholly
unknown till princely munificence and philofophic zeal
(of which we have a recent inftance) unite in producing
them to the world. After the very celebrated and inge-
nious labours of Mr. de luc, farther inveftigation of
the fubjedt of barometrical meafurement might feem
unneceflary, if not invidious; but, furnifhed as I was
with an apparatus every way fufficient for the inquiry,
finding myfelf in the country which had been the fcene
of his operations, and pofleffing fome fhare of his own
zeal, I could not but gratify the euriofity I had to verify
and repeat his experiments: if therefore in the purfuit
of this inquiry I fhould be led to a conclufion fomething
different from the- refult of his own obfervations, I am
convinced that this diftinguilhed obferver, of whofe
candour and talents I have an equal opinion, will im-
pute it wholly to a love for truth; as with me the
precept applies as ftrongly to the philofopher as to the
hifiorian, Nequid-falji audeat , ne quid veri non audeat
dicer e.

6

But

in order to afcertain the height of Mountains . 515

But to proceed. The inftruments. I made ufe of in
thefe operations were, two of ramsden’s barometers^;
three or four thermometers detached from the barome-
ters, w'hofe boiling and freezing points I had examined
myfelf; an equatorial inftrument, the circles of which
were about feven inches diameter, made by ramsden;
a fifty-feet iteel meafuring chain; and three three-feet
rods, two of deal and one of brafs,, in order to examine
and correct the chain, thefe latter made by baradelle
at Paris. Befides thefe I took with me a little bell-tent,
which I found of great ufe, as it defended me from the
wind and fun.; and I may remark, that the obfervations
of the uppermoft barometer were made in the tent.

My firft feries of obfervations I propofed to be on
Mont Saleve <b\ one of the Alps, fituated about two

( a ) It may not be improper to remark, that the fpecific gravity of the quick-
lilver of thefe barometers with 68° of heat was 13,61; the diameter of the
bore of the tube 0,20 inch; and that of the refervoir 1,5 inch.

(b) Mont Saleve-extends near nine miles -in length.; is not quite 3300 feet
in height above the Lake. That fide of it which is next Geneva is for the
1110ft part a barren rock, the north-eaft end of it being almoft a perpendicular
precipice; the other fide of the mountain is lefs rude, of a more gentle accli-
vity, covered with trees, fhrubs, and herbage, as is alfo the top, where is fome
of the finefl paflure in the world. It is inhabited only by a few fhepherds, who
pafs the fummer months here with their cattle, in little miferable huts or
'barns-; the remaining part of the year, .viz. for about four or five months, it
is covered with fnow. This -mountain contains chiefly a calcareous ftone ;
and there is reafon to believe that there is an iron ore in it, at leaft in fome
parts of it, as a piece Mr. de luc, the brother, .picked up near the fouth-wefl
end, I found, fenfibly affe&ed the magnet.

X x x a

leagues

5 1 6 Sir george shuckburgh’s Obfervatioas
leagues fouth of Geneva, and precifely on the fame point
where Mr. de luc had made his higheft or fifteenth fta-
tion : this fpot I learnt from his brother, whofe civilities,
both then and fince, I fhall frequently have occafion to
remember and mention.

The place where I meafured my bafe was in a field
near the villages of Archamp and Neidens, not quite
three miles in a horizontal line from the top of the rock
whofe height was to be determined (lee the chart that
accompanies this account). At the end of the bafe a
I intended to place one of my barometers; and the other
at the top of the rock, called the Pitton, at c ; and with
the above inftruments meafure the triangle abc. The
angles were taken both on the horary circle, which was
brought parallel to the horizon, and alfo on the azimuth
circle of the equatorial inftrument; this made it, as it
were, two different inftruments independant of each
other. The angles were moreover doubled, tripled, and
quadrupled, on each arch; by this means the error of
the center or axis of the inftrument vaniflied ; the poffi-
ble error in the divifions, in the reading off, and in the
coincidence of the wires in the telefcope (which magni~
filed forty times) with the fignals placed at each angle of
the triangle, wasdeflened in proportion to the number
of times the obfervation was repeated; and finally the

mean

in order to afcertain the height of Mountains . 517

mean of all was taken. The fame was done with each
angle at a, b, and c, horizontal as well as vertical, viz,
the elevation of c above a and b was taken ; and alfo the
depreflion of a and b below c. The advantage of this
method was, that the error of the line of collimation, the
effedt of refraction, and of the curvature of the earth’s
furface, all became equal and contrary ; by thefe means
the little errors were diminifhed, and great errors abfo-
lutely avoided^. I {hall, however, beg leave to fetdown
the operation at length refpedting this one triangle, in
order to fhew the precilion that may be expected from
fuch a geometrical procefs; to remove the fcruples of
thofe gentlemen who fufpedt that accuracy is only to be
obtained by large quadrants ; and laftly, to do juftice and
fatisfadtion to the celebrated artift who invented and
made this valuable inftrument.

(c) I muff acknowledge here, that the attra£lion of the mountain-creeps into
the account uncorre&ed for, but only half of this quantity influences the mean
refult, as at the top it was nothing, and at the bottom of the mountain it could
not exceed 10" in the dire&ion ac, as I find from a rough computation, the half'
of which zz 5" would give only four inches for the corre&iom

5i8 Sir ceorge shuckburgh’s Obfervations

Determination of the Bafe .

71*

76

73I

•

60

Ch. Ft. In. Temper.

Length of the bafe ab (fee the Chart) by the chain, \

fifttime, - - — 1 55 10 o

Ditto, fecond time, — — — 55 9 9J

The mean, — - — 55 9 10-87

Pt. In.

By frequent previous obfervations I determined C 4) the length

of the chain by comparifon with the brafs ftandard rod | 50 O o
reduced to 6o° of heat, — — ^

Correction for 13!° of heat from expanfion, — +0 o 05

Diameter of the pins or arrows, one of which was ufed at -j

each chain, and in fuch manner, that this correction be- r + 0 o 16
came always -j- — — —

Correct length of the chain as it was ufed in meafuring the 1

bafe, ° _ _ - - I 5° 0 21

Multiply by the number of entire chains in the bafe, — 55

2750 11 55

Add the parts of a chain, — — + 9 10 87

True length of the bafe, as it was meafured, — 2760 10 42

Correction for the defeCt of level, taken with an inftru- 1 _ Q

ment made on purpofe, each time the chain was placed, J

The true horizontal diftance between a anda becomes, 2760 9 66

Deter-

(d) It may ‘be required, to what precifion I could determine the length of
•my chain? I think certainly to within of an inch, or of the whole
length. The common Gunter’s chain of the fhops is always fubjeCt to fpring
and ftretch confiderably; mine was made of hardened fteel, on purpofe to avoid
this defeCt. It however ftill preferved fome degree of elafticity, for when
pulled with a force of about ten pounds, it feemed =0,12 inch longer than
iwhen laid gently on the floor without being flretched at all : the affumed length
vf the chain was fuch as feemed to me probable from a moderate tenfion in

^common

in order to afcertain the height of Mountains . 519

"Determination of the angles hy the equatorial.

2

-

On the azimuth
circle.

On the equat. circle, the"
horary being converted
into gradual divihons.

& A by the iff obfervation —

0 / //

58 27 30

0 / //

- 58 28 30

2d, — —

29 O

— 27 3°

3d, — —

— 2& 30

— 29 13

4th, — —

— 3° *5

— 29 15

fL taken four times over on the arch, —

233 54 i5

“ 233 54 3°

The mean, — *

58 28 49

58 28 37I

Laftly, the mean of all

from the

two circles

58° 28' 43^' = at a..

£

b by the i ft obfervation, —

m 54 45

~ HI 53 0

2d, - —

51 3°

52 3°

3d, - —

50 30

50 45

jL

taken three times over on the arch, —

335 36 45

- 335 36 15

Mean, — —

hi 52 15

- hi 52 5

Mean of all from the two circles = m° 52/ 1
= £- at r.

common ufing it. It may perhaps not be out of place to remark here, that the
rods with which the chain was examined, agreed exactly with the fcales of the
barometers;, at lealt the difference in nine inches, taken in different parts of the
fcale, did not appear to exceed of an inch.

(e) The precaution in taking the inclination of the chain every time, if the
bafe be nearly a plain, as is the cafe in many meadows, feems to be unneceffary";1’
for this fame corre£tion, deduced from the inclination of the bafe oblerved a c
a and b,. comes out "—0,99 inela, only 0,2 3 inch different, a quantity wholly
»confiderabke ■

§20 Sir george shuckburgh’s Obfervations

On the azimuth
circle.

On the eauat. circle*

C c by the iff obfervation, — *

2d, — — ■

0 tit

9 39 0

- 39 0

0 / tr

9 38 30
- 38 >5

3d> — —

- 38 45

- 39 45

4. taken four times over on the arch, —
Mean, — —

38 35 45
9 38 561

- 38 34 45

9 38 41 |

Mean of the two circles, =:

9° 38' 48 y

= t- at c.

By attual obfervation.

Angles finally corre£tc4>

4 at a,

— 58 28 43I ^ Thefe angles corre&ed by”! r§ 28 40I

— — III C2 IO I W ;to each (the 1 ^ „ Jg*

B> 111 *q- f fum of their errors, or

Z. at C, — - — 9 3° 4*4 | defe£t, from 1800 being

J _l8".) '

5*

9 38 544

Sum of the three angles ~ 179 59 42
Taken from 180 o o

7 become,

Sum, 180 o

Leaves the difference zr 1 ^

fum of the errors, J

It is highly curious and fatisfa&ory to fee the amazing
correfpondency of thefe obfervations, made with an in-
•ftrument of only 3^ inches radius, whereon an, angle of
one minute is about equal inch; and I think we
may fairly conclude, that the corrected mean refult of
thefe obfervations is true to within 6" or 8"^; which, as

(f) I may have a future occaiion to fpeak of the accuracy of this inftrument
for aftronomical purpofes; but I cannot omit this opportunity of mentioning
one, viz . in taking the latitude of the city of Amiens in Picardy, where I had
thirteen obfervations by the {tars and Sun, the mean of which differed 25" from
the extremes, and only 3" from the refult of Mr. Cassini’s obfervations,
-made, I believe, with a nine- feet zenith fe£tor, as related in La Mtridienne is
fyris verifies, 5

may

in order to cifc&rtain the height of Mountains. 5 2 t

may be proved hereafter, would occaiion an error of
only three feet in the diftance of the mountains, and
feven inches in the height. I proceed next to the ver-
tical angles.

Determination of the inclination of the Jides ac, bc, and
ab, with the horizon ; the height of the eye at the in-
Jlrument being four feet above the ground.

Altitude from below at a.

o / /j

Inclination of ac, — 10 33 2

Corre&ien for the part of

the fignal which was f — 1 38
obferved, 9

Correction for the line of | __ Q
collimation, — i 59

Correct for the refraCtion, — 027

True Altitude of c from a, 10 29 58

Deprefiion from above at

o / />

IO 29 18

CorreCt for the fignal, — +16

— — for the line of col- \

limation, — J + 59
— — for refraCtion, -f 27

True deprefiion of a from c, 10 31 o
Arch intercepted between, J

or curvature.

2 30

True altitude of c from a*|

deduced from the obfer- IO 28 30
vation alt c, J

Mean corrected altitude of c from a = io° 29' 14"^.

{g) If the computation were to be made from either of the obfervations take®
feparately, the difference would amount to only three feet in the height of c|
and this may either be in the correction of the line of collimation, the effeCfc
©f refraction, or in miftaking the part of the fignal that was obferved : for,
whilft I was gone to the top of the mountain, fome peafants pofTeffcd themfelves
of the handkerchiefs I had fixed to the fignals below in order to haye a
tonfpicuous and determined point.

YU

VOL. LXVII

Incli-

2 a Sir george shucks urgh’s Obfer vat ions

Altitude from below at b.

o / //

Inclination of bc, — 1 1 20 26

Correct for the part of the 1 ~

fignal obferved, — J 1 3
Error of collimation, — o 59

Correct for refradlion, — o 26

Depreflion from above at c.

o / //

II 19 47

Corre£t for the fignal, ■ — • — 59

Error of collimation, — +59

Effedt of refradlion, — +26

True altitude of c from b, 1 1 1 7 23

True deprefiion of e from c, 1 1 20 18
Arch intercepted, or cur- J 2 iS

vature,

True altitude of c from b,
deduced from the

fervation at c.

rom b, -j
ie ob- f

1118 o

Mean of the two, or corrected altitude of c front b

ii° 17' 41^'.

Altitude at a.

P 4- 44—

o

JL of inclination of abI
the bafe, — v J 7
Error of the line of col- 1

_ J — ° 59

limation.

Corredl altitude of b from a, o 26

Error of collimation.

Depreflion at

o / //

o 27 4
+ 0 59

Corredl depreflion of a 1 «

from b, — j 0 2 o

Arch intercepted, — — o 27

Altitude of b from a de-’j

duced from the obfer- f O * 2 7 36
vation at b, _

Mean of the two, or corrected altitude of b. from a
= o° 26' 49"

(h) It fhould feem from thefe two obfervations, that the error of the line of
collimation had been afiumed too great; it has however, as I have before
©bferved, nothing to do with the mean refalt: and this is, perhaps, one of the.
bell means of difcovering the error of collimation, and the very method Mr,.
de luc ufed, to adjull his level, though, as I have been informed by his brother,
without taking into the account the effe£t of curvature, which, if his hori-
zontal marks were 2000 feet diftant from each other, would amount to 20", and
the error to half that quantity,

s

I have

in order to af certain the height of Mountains. 523
I have thus, in a manner rather prolix, given a detail
of the methods ufed to afcertain the quantity of the dif-
ferent angles. It may he of ufe on a like occafion, and
will at leaft ferve to determine within what limits the er-
ror of the final refult may be expected to lye, as on the
precifion of the geometrical operations all the compa-
nions of the barometrical ones depend. This procefs
once mentioned will exempt me and the reader from the
trouble a fecond time, when he is informed, that the
fame fidelity and pains were employed (where the cir-
cumftances would admit) in all the trigonometrical ob-
fervations, of which the annexed chart is a fummary. I
proceed now to the determination of the fides, the com-
putations of which are too well known to enter into this
paper.

Feet.

Side ab 2760.8

AC 15286.4

BC 1404I.7

Thefe with the angles give for the height of c above A, —

The height of c above b, — — • — ~

The height of B above a, * — — «

Thefe two added give the height of c above deduced from the

obfervation at b, — ■ — — -

But the height by aft ual obfervation at a was, — —

Then the mean of the two, — —

which is probably within three or four feet of the truth,
or about one foot in a thoufand.

Y y y 2

Feet.

2835.07

2806.27

22.18

2828.45

2835.07

2831.76

Having

524 george shuckburgh’s Obfervations

Having thus the perpendicular height, as I think,
very accurately afcertained, it remained for me to take
the altitude of the barometer at each ftation a and c, and
if poffible with equal precilion. Thefe obfervations it
would be too tedious to fet down at length. I lhall, how-
ever, premife the following particulars. Every obferva-
tion of the barometer was triple ; that is, the height was
read off three different times, and the mean taken ; but
from once, reading only I could. be fure of the height to.

of an inch, excluftve of the error of the divifions*
which in fome places might amount to that quantity;,
this the nonius would itfelf difcover and even correct by
eftimation. At every feries of obfervations the float at the?
bottom was readjufted, fo that I could conftantly be fure.
of an alteration of the weight of the. atmofphere ex--
prefled by 0.00a inch of quickfilver, if not of half that
quantity. Finally, the difference of the two barome-
ters (>1 was conftantly taken, after being left three-quar-
ters

(1) It may be concluded, that-this difference fhould be. conHant, and always the
fame ; but, from what caufe I know not, it did not appear fo to me. In my journal
Jcor the. weather for 1.775, ^ find the following note: from a mean of feventeen
obfervations between AuguH 12th and Sept, before, at, and after, my>

expedition to Mont Saleve and the Mole, I find the difference between my two
barometers —,0042 inch, N° 1. Handing the higheft; in thefe comparifons,
however, the extremes fometimes differed from the mean ~,oo6. And in my
paffage over Mont C'enis* Dec. barometer N? i. Hood lower than N° 2.

In order to afcertain the height of Mountains. 525
ters of an hour or more in the fame place, to acquire the
true temperature of the air, and this before and after
every expedition. The fra&ional parts of a degree on
both the attached and detached thermometers were
noted only by eftimation, but written down to ioths,
being more convenient in the computation ; for I may
remark, that one-third of a .degree on the attached ther-
mometer is equal to about T5^ inch on the barometer;
this attention, therefore, to the fub-divifions of the de-
grees became neceffary. I conclude, laftly, with pre-
fuming, that the weight (k) of any column of air may be,
meafured with thefe barometers to ,008 inch, though all
the errors fhould lye the fame way. .

Leaving Geneva about half paft fix in the morning,
Auguft 20th, I arrived at the place a of my bafe a little
before eight; near to which there happened to.be a
Ihepherd’s houfe, in which I left one of my barometers,
(N° 1.) with a fervant, to examine and-obferve it every
five or ten minutes, for near nine hours fucceflively,

by — ,013 inch: It is difficult to account for this. May 1 oth, 1776, at Rome,
N° 1. flood loweft by ~,ooi. June 1 2th, at Naples, N° 1. flood loweft by
*— ,008. Sept. 10th, in London, N° 1, flood high eft by -p.006. Thefe,
apparent variations may poftibly arife from fome, alteration in the frame-work
of the barometers, through moiflure, &c.

(Jk) I muft not be underftood to mean, that the length of any column of air
may be meafured to an equal accuracy, even though our theory , fhould be pevr-
fe£t; this will.be the fubje£l of inquiry in its proper place0

until

1,

£ 2 6 Sir george shuckburgh’s Obfervations
until I returned; the. windows and doors of the room,
in which the inftrumerit was placed, being left open, by
which means there was a free communication with the
outward air, and the barometer not expofed to the Sun.
The detached thermometer was hung on the window
towards the' north-eaft, where there was neither direcSt
nor reflected- heat from the Sun n> . The two barometers

(1)1 have thought proper to mention this, as it is almofl the only circum-
ftance wherein my method of obferving differed from. Mr. de lug’s, whofc
thermometers (if I miftake not) were hung always in the Sun, and probably
for this reafon, becaufe the column of the atmofphere between the two baro-
meters, whofe mean heat is to be determined, is (if the Snn fliine) all expofed
to the Sun. I have, however, always preferred hanging them in the fhade,
and I give the following reafons : all fpurious and local heat from refle&ion is
more eafily avoided ; no concentrated and falfe heat is acquired by the mounting,
and thence communicated to the tube, even though the ball fhould be infulated;
and, finally, becaufe I fufpeft the real temperature of the atmofphere in the
Sun and in the fhade to be the fame, or at leaf! infenfibly different. This may
be thought to be advancing too much; but, to be fatisfied of the pofition, I made
no lefs than four-fcore obfervations with four different thermometers of very
different mounting, hung alternately expofed to the Sun’s rays, and fereened
from them by the fhade of a tree, in an open plain at fome diftance from the
town of Geneva. The refult was, that my beft thermometer, with the ball
infulated, differed only 2°’ in the different fituations; the others, more or lefs,
as they were more or lefs conne&cd with the frames in which they hung. One
of them, inclofed in a glafs tube, rofe 12° higher than the true temperature,
which was 7 70. It fhould feem then, that the variety in the mounting occa-
fioned this difference; and this effedt of the materials, of which the inflru-
ment is made, cannot be wholly avoided, as the glafs itfelf, which conflitutes
the ball of the thermometer, will acquire and contain more or lefs, in proportion
to its thicknefs and opacity. If a thermometer were perfeft, it would refleft
all the rays that it receives. More might be added to corroborate this idea,
but it would fwell this note to an unwarrantable length.

were

in order to af certain the height of Mountains . 527,

were here compared; and at a quarter after nine, begin-
ning my walk, I arrived, not without fome fatigue, at
the top of the mountain about noon.. The view from
thence was incredibly beautiful. Every object, that from
Geneva was ftriking, from thence appeared with an ad-
ditional effect. The mountains feemed higher and
nearer; the plain appeared a more perfect level, the fmall
inequalities from this height becoming infenfible ; and
a larger portion of the lake prefented itfelf: behind me
an innumerable collection of naked points and precipices,
all new objects, that from below are hid by the mountain,
afforded frefh and moft aftoniihing ideas of this very
lingular part of the creation. The clouds however (for
it was a little hazy) unfortunately prevented my feeing
Mont Blanc and the Glacieres, which were Hill farther
behind. Some of the clouds were below me, and very
near; exhibiting to me; at that time, a very lingular phe-
nomenon of the thunder grumbling under my feet. I
was occupied here between four and five hours with dif-
ferent obfervations. The barometrical ones I am now
going to relate ; and I lhall at the fame time give the
computations of them according to Mr. de luc’s me-
thod, or rather according to Dr. Horsley’s reduction of
it to the fcales and meafures of this country (vide
Philof. Tranf. vol. LXIV.) with this, difference, that I

have

528 Sir george shu cic burgh’s Obfervations
have reckoned the equation for the expanfion of quick-
filver =,00323 inch for every degree of Fahrenheit’s
thermometer in a column of 30 inches, inftead of ,003 1 2
which Mr. de luc ufed; the former I had collected from
fome of my own experiments made at Oxford in the
beginning of the year 1773: this difference will not,
however, occafion an alteration in the refult of any one
of my obfervations of more than five inches, and may
therefore be confidered as of no account. Of the real
value of this correction I fhall fpeak more hereafter.

The barometer was fet up on the mountain at one
o’clock, and left an hour and a quarter to acquire the
temperature of- the tent in which it was placed, before
the firft- regular feries of obfervation was taken. The
fucceeding obfervations were made at intervals of near
an hour each. I have ventured to fet down the height
of the barometer to ,0001 inch; but this is only the
mean from three or four readings off. It feems that the
heat of the tent was confiderably greater than that of the
external air.; this, however, can only influence the ex-
panfion of the quickfilver, Ihewn by the attached ther-
mometer, and not the preffure of the atmofphere.
Laftly, the. true difference in the height of the refervoirs
of the two barometers, by comparifon with a and c, was
-found equal 2831.3 feet geometrically.

Com*

in order to etfcertain the height of Mountains . 529

Comparifon of the jirjl feries*

Obfervations at jthe top of the mountain at c.

Barom. N° 2. Therm. Therm,

above at c. attached, detached.

In. Pts. 0 o

25.7120 78.0 6$,q

Correct for the diff. of the! ^ ^

2 attached therm. 5°.g? J

Barometer at the top, 25.6958 Log.

— — — below, 28.3951 Log.

4098621

4532434

D"ssI”;f,,lof,he) 433.S.3 {'Sfftof8-

Correct for 29°*7 heat, — — + 28.728

Corre£t height in fathom, — •*-

462.54?

x 6

Height in Englifh feet by the barometer, -
Height by the trig, method, — - —

- 2775.246
2831.3

Difference, or error of the barometer

— 56-1

Obfervatioris below at a.

Barom. N° 1. Therm,

below at a, attached.

In. Pts. 0

28.3990 72.1

Corre£t for the diff. *1

Therm.

detached.

73*9

65.0 heat at c.

or tne oaromecer, j 0

28.3951

69.4 mean heat of the air/

_ f {land. temp, according
39*7 I to Dr. HORSLEY.

-

■4 29.7 difference.

A detached thermometer in the tent flood at 7 oP,

Vol. LXVIL

Z z z

Com-

530 Sir george shuckburgh’s Obfervations

Comparifon of the fecond Series.
Obfervation at the top of the mount at c.

Correct for the Diff. of
the two attached therm,

Barometer at the top,

- below, —

Barom. N° 2.

Therm.

Therm.

above at e.

attached.

detached.

In. Pts.

0

0

27.7025

734

64.0

.1 -50

25.6975

Log. 4098908

28.3901

Log. 4531669

Difference, or fall of the \ , -r^rr r r f approx, height in

quickfilver, - ) 2.6926 MTof Log. 43*75* { £ngiifh feW.

Corre& for 28°.8 of heat, — — 4- 27.787

Corre&ed height in fathoms, — —

Height in feet by the barometer —

■ — by the trig* method, —

Difference, or error of the barometer

4 6°.538
x 6

2762.228

2831.3

— 68.i

Obfervation below at a.

Barom. N° 1
below at a.
In. Pts.
28.3940

Correa for the diff. 1 ___

of barometer, S 39

Therm. Therm,
attached, detached.

0 /■
71.6

28.3901

7 3-° ,

64.0 heat at ce

68.5 mean heat.

39.7 ftandard temperatures

4- 28.8 difference.

A detached thermometer in the tent flood at 69°.
During thefe obfervations the wind was S.W.; the
weather hazy, accompanied with a little thunder..

Cont

in order to af certain the height of Mountains. 531

Comparifon of the third feries.

Obfervations at the top near c.

Barom. N° 2<
above at c.
In. Pts.
25.6900

Correft for the difF. of the 1 «

2 attached therm. i°.4, / + 3

Therm.

attached,

69.7

Therm.

detached,

o

62.0

Barometer at the top, 25.6938

below, — - 28.3896

Difference, or fall of the \

Log. 4098283
Log. 453*593

f Approx, height in

- t 2-6958 Die of Log. 433.3.0 rc:

Correct for 2J°,5 of heat, — — -4 26.582

Correct height in fathoms.

Height in feet by the barometer,
— by the trig, method.

— 459-892

x 6

Difference, or error of the barometer

2759-352

2831.3

— 71.9

Obfervations below near to A.

Barom. N° I,
below at a.
In. Pts.
28.3935

Correct for the diff. "1

of barometer, J 39

28.3896

Therm.

attached.

o

71. 1.

Therm.

detached.

©

72.5

62.0 heat at c.

67.2 mean heat.

39.7 ftandard temperature.

+ 27.5 difference.

A detached thermometer in the tent flood at 65®.

Z z z a

Thefe

532 Sir george shuckburgh's Obfervdtiotu

Thefe obfervations then feem to prove that the baro-
metrical rules were a little defective as to the true ratio be-
tween the gravities of air and quickfilver, •viz. in the
value of an inch of quickfilver in the torricellian tube,
exprefled in inches of the atmofphere with a given tem-
perature. The firft comparifon gives for this error in
Refect -19.8 feet in every 1000 feet; the fecond, 24.0
feet; and the laft, 25.4 feet: the mean of the three is
23.1 feet; and by fo much we may conclude that thefe
rules, in greater heights alfo, will give the difference of
elevation too little, viz. by ~ nearly (m>. But it will be
fair to make the experiment.

(m) Left any fufpicion fhould arife of a difagreement between the a£lual
meafures taken by Mr. be luc and myfelf, I may obferve, that the mean refult
of three obfervations, which I made independently of each other on the height of
the Pitton or point c above the lake of Geneva, agree with the mean refult of
Mr. de luc’s operation from the levelling and the quadrant, to lefs than twelve
inches ; a greater correfpondency than which cannot be expelled : and this was
the true reafon why I chofe the fame fpot he had pitched upon. <c Le rocher
*c ifole , qui domine toute la montagne As a further confirmation, I compared his
ftandard fteel rod of twelve Paris inches, which his brother obligingly furnifhed
me with, with my brafs one, and found twelve inches on Mr. de luc’s rule
was on my rule, with 710 of heat, — — 12.784 Eng. inches.

Correflion for the difference of expanfion between! ,

brafs and fteel with 163 of heat, — — J + °7

Length of Mr. de luc’s French foot with 55°, — 12.7847

True length of the French foot ( vide Phil. Tranf.) 12.7890

Error or difference from the true Paris foot — — ,0043 =: jdxrs nearly.

I

The

in order to af certain the height of Mountains. 5 S S

The Mole is a convenient, infulated mountain,
fituated about eighteen miles eaft of Geneva, and riling
near five thoufand feet above the lake, much higher
than any body, that I know of, has ever made thefe ex-
periments at, with the required precifion. On this fum-
mit I determined to confirm or cor re 61 my difcovery, and
communicated my intentions to Mr. de saussure, a very
ingenious gentleman of this place, and well fkilled in
various parts of natural and experimental philofophy,
who gave me all the information neceffary, and obligingly
promifed to accompany me, as did alfo Mr. trembley,
afliftant to Mr. mallet, well known in the aftronomical
world. This expedition was undertaken in the latter end
of Auguft and beginning of September. I lhall here
beg leave to fet the reader down at the bottom of the
mountain, and flatter myfelf he will accompany me to
the top. It was about five in the afternoon when we left
St. Joire, a wretched little village at the foot of the moun-
tain to the eaft, and where we had dined in a moft mi-
ferable auberge , preparing to afcend the fummit on foot,
being feven or eight in company, including guides and
fervants, who carried my inftruments, provifions, &c. ;
the former confifting of the equatorial, the barometer,
different thermometers, ele6trical balls, an hygrometer,
and a dipping-needle; together with another barometer

of-

534 S*r george shuckburgh’s Obfervatiom
of Mr. de luc’s conftruction, a variation-needle, a level
belonging to Mr. de saussure, and a tent. Thus accou-
tered we proceeded up an afcent, not however very fteep,
for three hours and a half without intermifiion, the path
leading in a fpiral kind of direction, very rugged and full
of loofe pieces of rock that are brought down with the
melting fnows, palling through romantic woods of fine
firs and other trees, interfperfed here and there with a
thin foil of excellent pafture. Before we arrived at the
hut, where we were to lleep (for our intention was to lay
upon the mountain that night, in order to have the more
time the next morning for our operations) having
walked on a little too far before, we loft fight of our
guides. We called feveral times, but were never an-
fwered: — the night was now coming on; a kind of fog
appeared, with fmall rain; our fituation became fome-
what embarraffing. We called again, but were anfwered
by nothing but an echo, the place being a moft profound
folitude. We began now to confider ourfelves as loft.
Mr. DE saussure, though, he had been feven or eight
times before upon the mountain, found himfelf in doubt
concerning the way ; but after a fliort dilemma thought
it belt to proceed. We did ; and now began to perceive
at a diftance fome little huts or hovels indiftin£tly : a few
more lieps allured us we were right, and about nine

o’clock

in order to afcertain the height of Mountains. 535.
o’clock we had the good luck to find ourfelves at the very
hovel, where we were to reft that night. I own I now
found myfelf quite contented, though I did not at all
know what kind of place I was going to enter. It proved
to be a little hut made of boards, confiftingof one apart-
ment only, eighteen or twenty feet fquare, and about
twelve high in the center, without any windows or
chimney for the fmoke, except what was made by the
holes in the roof, and the interftices between the boards-
at the fides, which were rudely put together, fcarce
clofer than park-palings, affording an equal entrance to
the wind, rain, and fnow; for as thefe hovels are inha-
bited only for about four months in the fummer, they
are conftruCted without the leaft mortar or cement in
the world an humiliating, witnefs this, how fimple the
architecture which nature and neceffity fuggeft. On en-
tering we found a comfortable fire, and the littl q cabana
inhabited by a couple of Alpine Ihepherdefles and their
two cows, on whofe whey and fome very coarfe bread
they wholly fubfifted, not difcontented but even proud of
their lot ; and who, out of a lingular fpecies of contempt,
call the inhabitants of the plain mange-rotis,t hat is, eaters of
roaft-meat. Their language too was different ; not French
nor Italian, but partaking fomething of both ; or, as I have
been fince informed, a corruption of the ancient Celtic,
c A few

536 Sir george shuckburgh’s Obfervations
A few minutes after our arrival our guides rejoined us :
it was now night, and in this rather too artlefs habitation
we were obliged to lay in a little loft over the cows, our
beds fome leaves and clean hay, and my bolfter my port-
manteau1fnJ. I had had the caution to bring fome fheets
with me, and, being a little tired with my walking, flept
five hours pretty foundly, though much ftarved, having
no other curtains than what this wooden canopy afforded,
through which the ftars fhone moft brilliantly. Between
four and five we arofe; found the heavens beautifully
ferene, and, having eaten fome of our provifions, left
this habitation, which might be fituated about two-thirds
of the way up the mountain ; and beginning our march
about half after five reached the fummit a quarter before
feven; but not without a good deal of climbing, and
fometimes up an afcent of near 40° for feveral hundred
feet. One of my fervants, before he got half way, found
his head turn round, and himfelf fo giddy, at the height
and precipices (a frequent effect in thefe fort of places)
that he was obliged to return to the hut. In the
afcent I faw the Sun rifing behind one of the neigh-

(ft) * Frigida parvas

Prseberet fpelunca domos, ignemque, laremque,

» Et pecm, et dominos communi clauderet umbra ;

Sylveftrem montana torum cum fterneret uxor
Frondibus et culma. juv. Sat, vi.

bouring

in order to afcertain the height of Mountains. S31?
houring alps with, a moil beautiful effect, and the fhadow
of the mountain we were then upon extended fifteen or
twenty miles weft. We had now reached the fummit ; and
there my curiofity finifhed in aftonifhment. I perceived
myfelf elevated 6000 feet in the atmofphere, and {landing
as it were on a knife-edge, for fuch is the figure of the
ridge or top of this mountain ; length without breadth, or
the leaft appearance of a plain, as I had expe£ted to find.
Before me an immediate precipice, a pic, of above 1000
feet, and behind me the very fteep afcent I had juft now
mounted. I was imprudently the firft of the company :
the furprize was perfedt horror, and two fteps further
had fent me headlong from the rock.

On this fpot, with fome difficulty, we fixed the inftru-
ments, and commenced our operations, after fome time
fpent in admiration at the profpedt, and familiarizing my-
felf to the fcene. Before me, at fome diftance, was fpread
the plain in which lay Geneva and the lake; behind it
rofe the Dole, and the long chain of Mont Jura as far as
the fort La Glufe, which we entirely commanded, as well
as fome of the country beyond it. A little to the left, and
much nearer, lay Mont Saleve, which from this height
appeared an inconfiderable hill : to the right and left no-
thing but immenfe mountains, and pointed rocks of every
poflible fhape, and forming tremendous precipices. In the

Vol. LXV1I. 4 A vale

53B Sir george shuckburgh’s Obfervations
vale beneath, feveral little hamlets, and the molt beautiful
pafturages, with the river Arve winding and foftening
the fcene ; from whence arofe a thick evaporation, col-
lecting itfelf into clouds, which on the lake, that was
quite covered with them, had the appearance of a fea of
cotton, the Sun-beams playing in the upper furface of
them with thofe tints that are feen in a fine evening.
To the fouth-weft appeared the lake of Annecy; be-
hind us, taking up one-fifth of our horizon, lay the
Glacieres, and amongft them, towering above all the reft,
flood Mont Blanc. The circumference of the horizon
might be about 200 Englifh miles; and, though not one
of the moft extenfive, yet certainly one of the moft varied
in the world. From this fpot the clouds had a ftriking
appearance to an inhabitant of the plain; very few of.
them at above one- fifth of the height that we were now
at; not governed by the wind, but moving in every pof-
lible direction ; fome of them feemed creeping along the
ground, whilft others were riling perpendicularly be-
tween the hills. And I may here remark, that from
Geneva I have obferved the clouds were, generally three
days in the week below the fummit of Mont Saleve; fo
that the ordinary region of thefe vapours feems to be at
that height in the atmofphere, where the barometer:
would Hand at about 2 6 inches in this climate.

7

While

in order to af certain the height of Mountains . 539

While at the top of the Mole, I was very fenfible of
the cold, there being a brilk wind, which, though, fouth,
came over the mountains of ice, and was very keen;
infomuch that, about two hours after I had been there,
I nearly loft the ufe of my fingers, and found my lips
much affected and parched from the tranfition, having
been a good deal heated in afcending with two waiftcoats
and a great coat on. The thermometer, however, when
I firft mounted, flood no lower than 48°. I muft here
afk pardon for this long digreflion, which I have ven-
tured to tranfcribe from my journal written upon the
fpot.

To return then to the obfervations. After what has
been faid refpeiting thofe on Mont Saleve, it will l'uffice
here to mention, that by repeated meafurements I de-
termined the horizontal length of the bafe 1 , 2 (fee the
chart) to be = 1 2 5 o ft. 3.9 inch; the L. at 1 = 95° 37'28;/;
z. at 2 = 7 70 48' 53"; and the z. at 3 = 6° 33' 49'''. The
mean corrected angle of elevation of 3 from 1
= 2i° 29' 34"; ditto of 3 from 2-210 3' 41"; and laftly,
the elevation of 2 from i=o° 47' 24".

4 A 2

Thefe

540 Sir george shuckburgh’s Obfervations

Feet.

Thefe obfervations give for the length of the fide i9 3, — 10691.9

— — — • — 2, 3, — 10886.7

Height of 3 above i, — — 4212.8

3 above 2> — — — — 4194.8

2 above i, — — — «_ 17

And confequently, 3 above 1 deduced from the obfervation at 2, — 42 1 2.0

And laftly, the mean height of 3 above 1 from the determination at!

each end of the bafe, — j 4212.4

The difference in height, however, between the two
barometers was only 421 1.3 feet.

Here follow the barometrical obfervations and their
reduction. .

(0) Made between the hours of eight and twelve, in the open air and not in
the tent, which could not be pitched on accout of the fmallnefs of the plain at
the furamit; a briik fouth wind, but fair. The barometer was fereened by an
umbrella.

Com*

in order to afcertain the height of Mountains. 541
Cornparifon of the JirJl feries on the Mole,

Obfervation at the top at 3.

Barom, N° 2.
above at c.
In. Pts.
24.1437

Dorre& for tbe Diff. of the 1 1 gg

two attached therm. 3°.4, J

Barometer at the top, 24. 1 525

■— below, — ■ 28.1253

Difference, or fall of thel

Therm.

attached.

o

57-o

Therm*

detached*

54-8

Lost.

Log;

6. 3829621

4490971

f approx, height in

quickfilver, - ) 3-97*8 Diff. of Log. 661.350 j fathoms>

Correct for i8°.6 of heat, • — — » 4- 27.431

Corre£led height in fathoms, — •

688.781
x 6

Height in feet by the barometer — > 4132.686

^ by the geometrical meafurement, 42 1 1 .3

Difference, or error of the barometer,

78.6 —

Obfervation below at i .

Barom. N° i.
below at 1.
In. Pts.
28.1205

Correal for the diff, 1 ___

of barometer, j

28,1253

Therm. Therm,

attached, detached* •

° o

60.4 61.9

54.8 heat at 3*

58.3 mean heat.

39.7 flandard temperature

4- 18.6 difference*

Com-

542 Sir GEORGE shuckburgh’s Obfervations
Comparifm of the fecond Series*

Obfervation at the top at 3.

Barom. N° 2.
above at 3.
In. Pts.
24,1420

Correa for the diff.of the 1
two attached therm, 3°.5, J

24. 15 11

28.1258

Therm. Therm,

attached. detached.

o ®,

56.9 56.0

Log. 3829369
Log. 4491049.

Difference, or fall of the j Diff. of Log. 661.680 *

quicknlver, — J Q

Corred for I9°.2 of heat, — + ab‘33°

Correa height in fathoms.

690.010
x 6

Height in feet by the barometer,

« by the geom. method.

Difference, or error of the barometer.

4140.06

42U.3

— 71 2 — ji&hr*

Obfervation below at i.

Barom. N0-i.
below at i.
In. Pts.
28.1300

Correa for the diff. 1
of barometer, J

42

28.1238

Therm. Therm,

attached. detached.

60.4 6°i.8

56.0 heat at 3.

r8«9 mean heat.

39.7 ffandard temperature.

— 19.2 difference.

in order to afcertain the height of Mountains. 543

Comparifon of the third Series.

Obfervation at the top at 3.

Therm. Therm,

attached. detached.

o o

56.0 56.0

o 57.5 W

Barom. N° 2.
above at 3.
In. Pts.
24.1670

Correa for the diff. of the 1
two attached therm. 4°9. J I2?

24.1797

28.1278

Log. 3834509

Log- 449 r358

Difference, or fall of the 1
quickfilver,

Gorreft for I9°8 of heat, — —

j 3.948 1 DiCof Log. 656.849 { AS^Sht

Correal height in fathoms, —

Height in feet by the barometer,

by the geom. method,

Difference, or error of the barometer.

4- 29.0

685.849
x 6

41 15*°94
421 1.3

96.2 — 01

Obfervation below at i *

Barom. N° 2.

Therm.

below at 2.

attached.

In. Pts.

~ 28.1320
Correa for the diff. 1

60.9

of the barometer,. J 42

28.1278

Therm.

detached.

62.0

56.0 heat at 3.

59.5 mean heat.

39.7 ftandard temperature,

19.8 difference. „

. (f ) In tW*:«>tomn for the detached thermometer at the toppf the mountai
d t.ie following obfervations, are inferted two numbers; the upper 01
expreffing the heat in the lhade; and the lower one, with this mark © prefix*

at 1.1 the Sun. The computation, however, is made .from the forme
tbis may ierve to fhew the difference.

Com -

544 Sir george shuck burgh’s Obfervatiom

Comparifon of the fourth feries.
Oblervation at the top at 3.

Barom. N° 2.
above at 3.
In. Pts.
24.1780

Corre£l for the cliff, of the 1
two attached therm. 4°6, J 1 *9

Therm.

attached.

o

57-z

Therm.

detached.

*0

56.0
0 57-5

24.1899

28.1318

Log. 3S36341
Log. 4491976

3-94.9Diff.ofU8. 655.63s (XS2**
Correct for 20°.3 of heat, — — -f 29 678

in

Corredl height in fathoms.

Height in feet by the barometer, —
by the geom. method, —

Difference, or error of the barometer.

685.313
x 6

41 11.878
42H.3

99.4 — TOWS*

Obfervation below at i.

Barom. N° 1.

Therm.

Therm.

below at 1.

attached.

detached.

In. Pts.

rs

O

28.1360

61.8

63-9

ff.l

r, 1 42

56.0 heat at 3.

60.0 mean heat.

28.1318

39.7 ftandard temperature,

+ 20.3 difference.

Com-

in order to ascertain the height of Mountains. 545

Comparifon of the fifth feries.
Obfervations at the top at 3.

Barcm. N° 2«
above at 3.
In, Pts.
24.1840

Corre£t for the difF. of the 1
2 attached therm. 20. 8, J + '3

Therm.

attached.

59-6

Therm.

detached.

o

57-°

0 59-3

24.1913

28.130S

Log.

Log.

3836592

4491820

Difference, or fall of the 1 „ cr q 1 approx, height in

quickfilver, j 3-9395 D«ff. of Log. 655.228 J ^thom6j »

Correct for 20°. 8 of heat, — — -f 30.391

Corre£t height in fathom.

Height in feet by the barometer,

— by the geom. method,

Difference, or error of the barometer,

686.619

x 6

41 i3*7i4
4*11-3

- 97.6 -

TO TO T »

Obfervations below at i.

Barom. N° i.

Therm.

Therm.

below at 1.

attached*

detached.

In. Pcs.

o

O

28.1350

62.4

64.0

r. 1

j —42

57.0 heat at 3.
60.3 mean heat.

28.1308

39.7 flandard temperature.

-f- 20.8 differencec

Vol. lxvii.

4b

CQv/I—

546

Sir george shuckburgh’s Obfervations

Comparifon of the Jixth feries.

Obfervation at the top at 3.

Barom. N° 2.
above at 3,
In. Pts.
24.1900

CorreCt for the diff. of the 1
two attached therm. i°6, J ^ 1

Therm. Therm,

attached. detached.

61.0 57.0

O 60.0

24.1941 Log. 3837095

28.1268 Log. 4491204

Difference, or fall of the 1 _ rvrr ct c

quickfilver, } 3-93*7 Diff. of Log. 654.157 (

Correction for 2Q°6 of heat.

— +30.048

approx, height in
fathoms.

CorreCt height in fathoms.

684.157
x 6

Height in feet by the barometer,

by the geom. method

4104,942

Difference, or error of the barometer,

— IO6.4 —

Obfervation below at i .

Barom. N° r.

Therm.

Therm.

below at i.

attached.

detached.

In. Pts.

28 131a

62.6

63.6

CorreCt for the diff. 1

57,0 heat at 3.

of the barometer, J ^

60 3 mean heat.

28.1268

39 7 Itandard temperature.

20.6 difference.

To

in order to af certain the height of Mountains. 547
To collect thefe laft experiments in one point of view.

Feet.

The 1 ft feries gives for the error on every 1 000 ft.

4th, — — —

5th, — — —

6th, — — ■ —

( 8 . 7
1 6.9
22.8

23-5

23.1

25.2

The mean error,

21.7

which agrees within two feet in a thoufand with the de-
termination on Mont Saleve. This refult then juftifies
my conclufion (in p. 556.) and proves that either the
proportional gravity of air and quickfilver is now dif-
ferent from what it was, when M. de luc made his
experiments, viz. from 1756 to 1760; or that his or
my obfervations are defective. That my trigonometrical
meafurements were fufficiently exa£t, viz. to within two
or three feet, I think I have already fliewn ; and even that
his were alfo. Within what limits my barometrical er-
rors are to be found is not difficult to determine from
what has been before premifed. That the fcale of Mr.
de luc’s barometer was lefs accurate than mine, is, I
think, without a doubt; and indeed he never attempted
a divifion lefs than ^th of a French line, or about

4 B 2 °f'

548 Sir george shuckburgh’s Obfervations
of an inch Englifh : and yet when I confider the number
of his obfervations, and the unexampled diligence and
care with which he made them, I am obliged to attribute
the difference of our refults to fome other caufe than that
of inaccuracy. If then future experience fhould demon-
flrate, that the denfity of the atmofphere with a given
heat is invariable, or nearly fo ; while the preffure of a
whole column of it continues the fame, we may perhaps
fearch for the caufe of our difagreement from hence,
viz. the barometers of Mr. de luc were not fufficiently
near each other in an horizontal direction: mine were
feparated from two to three miles ; and his, I believe, at
double or triple that diftance. It may be fufpeited, I am
well aware, that the fyphon conftrudtion of Mr. de luc’s
barometer might occafion this difference : let us fee whe-
ther this be the cafe. Mr. de saussure (whofe inftru-
ment was of Mr. de luc’s conftrudtion, and made, as I
underffood, under his infpedtion) obferved at the top of
the Mole, or at leafl nearly on the fame level with my.
barometer, as follows :

in order to ajcet.tain the height of Mountains. 549

Barometer
In. L. i6ths.

22 8 o

Therm attached.
de luc’s fcale.

4 I° +

Therm. det.
re a u m. fcale.

+ IO°«

And in Englifh meafure and fahren-
heit’s fcale, — — . . :

Mr. de saussure’s barometer ordinarily
ftands higher than mine N* 2. by (9),
Corredt for the diff. of our attached therm, T,

24. 1 5 7 a*

— .0117
4 26

56

Mr. de saussure’s barometer corre died, 24.H79

My barometer ,N° 2, fee the firft feries, 24.1437; — 57

54-2-

54 B?

Difference, — 4 .0042 wholly inconfiderable.

Our barometers may therefore be faid to have agreed;
exactly.

Mr. de saussure made a fecond comparifon juft
before we left the top of the mountain, which proved as

follows,.

-

Barometer

Therrm attached.

Therm.

In. L. i6ths.

de Due’s fcale.

detached.

22 8 8

+ 4°

+ iii°

Or reduced to Englifh meafure and fcale, 24.2014
Mr. de saussure’s barometer hands 1 __
higher than mine N° 2. — J * ‘

Corr. for the diff. of our attached therm. 0°.7, — .001B

6l.7

57-9

Mr. de saussure’s barometer corredted, . 24. 1 879

My barometer N° 2. fee the lixth feries^. 24,190.0.

Difference, — - — — 00021 *

61.O

57

So that, in the firft comparifon, his barometer at the
top of the Mole flood higher than. mine by + ,004 inch
and in the laft, lower by —,002 ; the mean is higher by

(q) This we found by comparifons at the bottom, of the mountain.

4,001

I

550 Sir george shuckburgh’s Obfervations
+,ooi, equal to about io inches in deducing the height
of the mountain, a quantity wholly to be negledted.
Finally, the mean of Mr. de saussure’s obfervations
gives the defe6t of Mr. de luc’s rules 21.9 in a thou-
fand. The conftrudtion of the barometer had therefore
no influence on this difference. But further, while Mr.
de saussure obferved the height of the barometer on
the Mole, Mr. de luc, the brother made a correfponding
obfervation with a fimilar inftrument at Geneva. I ill all
relate this obfervation, computed after Mr. de luc’s
manner.

Mr.

in order to afcertain the height of Mountains. 551

Mr. de s aussurEj. at 4 feet -v
below the fummit of the ?
Mole, — J

Mr. de saussure’s barom.
ftands higher than Mr. de ?
luc’s ordinarily by, J
Thermometer attached + i°.

Mr. de lug, 78 feet above \
the lake, — ■ i

Therm, attahced 4-6°, —

Difference of the Log.

In.

L.

i6ths.

22

8

0

+

Heat' of the air.

—

Of

1 6ths of a line.

Log.

6387587

f T

REAUM. DE LUC’S

Therm. Therm.

+ 10 —15!

22

8

o| =435*4

27

0

O

—

6

26

11

10

7141620

+ 15 — 4

ig°| x 2JJAA2 zz the corre£lion for the temperature,
Corre£l height in French toifes, — •

754 ‘°33 Sum —T9f
-14.854

739^79

x 6

Height in French feet, — *— 4435-°74

Mr. de luc’s barometer above the lake of Geneva, 4-78.

Mr. de saussure’s barometer below the fummit of \

the Mole, — — — j -r 4*

And confequently, the fummit of the Mole above \
the lake, in French feet, — • — J^-> 7°

Which reduced to Englifh feet is, — — 4814

But, by a mean of my trigonometrical operations, ^
this height is ( vide chart) — ■ —

]4883.

Difference, or error of the barometrical rules.

—69. zz

To 00*

This laft obfervation ferves at leaft to fhew, that the
error I am contending for is on the defective fide, though
it gives the quantity of it fomewhat lefs, but by no means
deferves that confidence which the other companions do;
for, befides that this fingle obfervation may be concluded

lets

552 Sir george shuckburgh’s Obfervations
lefs decifive, the trigonometrical meafurement is alfo lefs
accurate from the diftance; and, laftly, to fuppofe the
flate of the atmofphere precifely the fame with refpedt
to weight in two places twenty miles afunder, is, I am
afraid, a pojlulatum too hazardous to grant. I therefore
fay, that all thefe obfervations confirm the fame truth,
that the atmofphere is lighter than Mr. de luc prefumed
it. What had already been done may feem fufficient for
the eftablifhment of this fadt; for I have always held,
that a few obfervations, well made and faithfully related,
do more in the interpretation of nature, than a multi-
tude of crude, carelefs, and immethodical experiments.
But I have not done: I wiflied to put this matter out of
all doubt, and accordingly undertook another expedition
to the fummit of Mont Saleve, on the 18th of Septem-
ber, and in a colder temperature : the experiments then
made, with their refults, were as follows :

The difference of adtual height by the two barometers
was 2828.9 feet> the barometer N° 1. ftanding higher
than N0 2. by +,0038 inch, when compared at the bot-
tom of the mountain.

Com-'

in order to af certain the height of Mountains. 553

Obfervation at the top of
the mountain.

Comparifon of the firjl feries.

Obfervation at the bottom.

Barom,N°2. Therm. Therm,

at the top. attached. detached.

In.

2S-65 33 58-° 56.2

Barom. N® i. Therm. Therm,
below. attached, detached,

Q O

28.4040 58.1 58.8

Feet.

This gives for the height barometrically, 275 5.6
But the true height was, — 2828.9

Difference, or error of the barometers, -73.3

15,

I OOOO

Comparifon of the fecond feries.

Obfervation at the bottom.

Obfervation at the top of
the mountain.

Barom. N° 2. Therm. Therm.

Barom. N° i.

Therm.

Therm.

at the top. attached. detached.

below.

attached.

detached.

In

In.

0

0

25.6550 56.2 57.O

28.4040

5 8 *5

Feet.

60.8

This gives for the height barometrically, 27 54.9

But the true height was,

—

2828.9

Difference, or error of the barometers,

-74.0

""" I0000f

4C

Vol. LXVII.

Com -

5.54 $r george shuckbuPvGH’s Ol/fervations

Comparifon of the third feries.

Obfervation at the top of Obfervation at the bottom,
the mountain.

Barom. N° 2.

Therm.

Therm.

Barom. N° 1.

Therm.

Therm.

at the top.

attached;

detached.

below.

attached.

detached.

In.

0

0

In.

0

0

25.6620

56.2

28.4040

59*3

Feet.

62.0

T his gives for the heightbarometrically, 2748.9
The height by the trigon. method was, 2828.9

Difference, or error of the barometers, - 80.0

Comparifon of the fourth feries.

Obfervation below. .

Obfervation at the top of
the mountain.

Barom. N° 2. Therm. Therm,

the top. attached., detached.

In.

25.6600 56.4 57.4

Barom. N° 1. Therm. Therm,

below. attached. detached.

o o

28.4040 59.3 62*4

Feet.

This gives for the height barometrically, 2752.8
But the true height was, 2828.9

Difference, or error of the barometers, -76.1 = 7469

0000®

In thefe companions I have not inferted the whole of
the computation, as that may eafily be made by any
perfon at leifure. Finally, the mean of thefe four laft

feries

in order to ajcertam the height of Mountains. 553
feiies gives for the error on 1000 feet, 26.8. I think I
have now fhewn, that the error actually exifts; it re-
mains that we determine precifely the quantity of it.
For this purpofe it will be proper to colled! all the pre-
ceding observations in one point of view.

Table of the refult of all the barometrical experiments,

Place of obfervation.

Mont Saleve,

At the Mole, <{

Mont Saleve,

r 1

True height
irigonometri-
caily.

2331.3

4211. 3

2828.

Height by
the barome-
ters.

2775.2

276-5.2

27S9 4

4132.7
4140.1

41 IS'1

4111.9

4ii3-7

4104.9

275S-6

2754-9

2748.9

2752.8

Mean

heat.

69.4

68.5

67.2

58- 3
58.9

59- 5

60.0

60.5

60.3

57*5

58.9

59-6

59-8

Error in
feet.

— 56-1

— 68.1

— 7 1 -9

— 78.6

— 71.2

— 96.2

— 99*4

— 97-6

I06. I

— 73-3

— 74-o

— 80.0

— 76.1

Error in
1000 feet.

— 19.8

24.O

—25.4
— 18,6
— 16.9
—22.8
—23.5
—23,1
—25.2
-^25.9
— 26 2
— 28.2
— 26.9

Mean error in
1000 feet.

} -2-1

7 — 21-7

—26.8

Mean of all, 23.6, and the temperature 61°. 4.

The Mole, from two ob-

fervations of Mr. de
saussure, —

The fame by Mr. de
•saussure, and Mr. de
euc, at Geneva,

According to Mr. the Mole,
obfervation s, fee

DE LUC’S own 1 the Dole,

Recherches

i’Atmofpher

fur } Buet,

Mc Blanc,

4211. 3

—

92.

— 21.8

4S83.

4814.

—

— 69.

— J-4*

*

4882.8

4860.

—

— 22.8

— •47

4292.7

4210.

— -

— .82.7.

—19-5

8893.6

8770.

— *

—123 7

— J3 9

I 14432-5

14093.

—

—33 93

-23.5

16.2

The

4 C 2

556 Sir george shuckburgh’s Obfervations

The titles of the columns are fufficiently clear to make
a farther explanation of this table unneceflary; and it
appears, I think inconteffably, upon taking a mean of my
thirteen obfervations (and I fhall here confider only my
own) on Mont Saleve and the Mole, that this error is
about 23-i feet on every thoufand; that is, the rules of
Mr. de luc give the height by l'o much too little. At
the bottom of the foregoing table 1 have fubjoined fix
other comparifons, fome of them from Mr. de luc’s
own obfervations, as recorded in his valuable work;
which however I muft add, are certainly of lefs autho-
rity in this inquiry, as they were made with barometers
a great way diflant from each other, viz. near thirty
miles: befides which, the geometiical heights are, for
the fame reafon, not fo accurately afcertained. I have,
however, ventured to make what ufe I could of them,
viz. to fhew that thefe two give a refult on the fame
fide, though not exactly the fame ; and to urge the ne-
ceflity of a certain vicinity in thofe obfervations from
whence a theory is to be deduced.

Shall I be permitted to adduce another proof, in con-
firmation of what has been advanced ? When I firft took
up the confideration of meafuring altitudes in the atmo-
fphere with the barometer, and had heard only of Mr.
de luc’s labours, it occurred to me, that there was a
6 much

in order to af certain the height of Mountains. 557
much more Ample method of arriving at this theory,
than either he or I have fince purfued. It was this; to
determine hydroftatically the fpecific gravities of air^
and quickiilver, with a given temperature and preffare ;
the increafe of volume, or change of gravity, with a
given increafe of heat being fuppofed to be known by
the experiments of boerhaave and hawkesbee (,\
which might be farther examined by fimilar ones ; and
prefuming that the geometrical ratio in the air’s den fity, as
you advance upwards from the earth’s furface, had been
fufficiently demonftrated^. For the proportional gra-
vity of quickiilver to air will exprefs inverfely the length
of two equiponderant columns of thefe fluids, that is,
when the columns are taken infinitely fmall {x). With

thefe

(r) It may feem particular that I ftiould propofe an experiment fuppofed to
be very well known, and which hardly any elementary treatife on chemiftry or
experimental philofophy will not furnilh us with an example of; the weight of
a given quantity of air. boyle, halley, hawkesbee, hales, each of
them have tried it, and many others fince their time : but the misfortune is, all
thefe experiments have been but grofs approximations, without due attention to
the heat ; and yet the determination of hawkesbee feems to have b:en followed
by one half of Europe in Pneumatical refearches. Indeed I only know of one
experiment that has the leaft title to precifion, and that is Mr. caven-
dish’s, briefly related in the LVith volume of the Philofbphical Tranfa&ions. *

(5) Elementa Chemise.

(t) Phyfico-mechanical Experiments.

(u) cotes’s Hydroftat. Leflures, et alibi .

(x) I am not forry to anticipate the reader’s remark here, that this obfer-
vation is not new; fince I find that I have been treading the fame fieps with

Mr,

-Sir oeorge shuckburgh’s Obfervathm
■fchefe ideas I made the following experiment. I caufed a
glais veflel to be blown fomething like a Florence flafk,
or rather larger; to the neck of this was adapted a brafs
cap with a valve opening outwards, and made to fcrew
en or off, together with a male fcrew, by which it was
fixed to an excellent pump of Mr. nairne’s conftrudlion,
and exhaufted of its air, or at lead rarified to a known
degree: the veflel was then carefully weighed with a
fenfible balance, and again after the air was re-admitted;
the difference gave the weight of the air that had been
exhaufted. After having repeated this two or three
times, the veflel was exadily filled with water as far as
the valve, which had been the term of capacity for the
air ; this was done by fcrewing on the cap till the fuper-
fiuous water oozed all out, and upon inverting the veflel
there appeared not the leaft fign or bubble of air; I
therefore concluded, that the volume of water was pre-
cifely. the fame as had been the volume of air, a circum-
ftance that fhould be accurately attended to. It was then
carefully weighed, and compared with its weight when
full and deprived of its air. It will readily be feen, that
I had then the fpecific gravity of the two fluids, upon
fuppofition that the figure of the glafs had not altered

Mr. boyle and Dr. halley, who both made ufe of this method ; the one with
a -view to determine the limits of the atmofphere; and the other the height of
Snowden.

-2 by

in order to af certain the height of Mountains. 559

by preifure during the experiment; and this effeCt may-
be prefumed to have been the moil fenfible, when the
veil'd was filled with water, the preifure at that time
being from within. To alfure myfelf of this, I let in a
fmall quantity of air, which formed a bubble of about
one-third of an inch in diameter, and upon immerging
the glafs in another veifel of water, whereby the pref-
fure within was counterpoifed by a preifure without, the
bubble feemed, to contrad itfelf by a quantity, as I found
afterwards, equal to about tyro grains in weight, or — ^
of the whole contents. I therefore concluded, that this
correction was hardly worth taking notice of, and ftill
lefs the effeCt from external preffure when the glafs was
exhaufted. At every operation the height of the baro-
meter and, thermometer (placed clofe to the veffel when
the air was weighed) was noted down, together with the
height of the pump-gage, which, compared with the
barometer in the room, fhewed the quantity exhaufted.
The refult of the experiment was as follows, the baro-
meter in the room Handing at 29.27 inches, and the .
heat of the room 53°.

The •

560 Sir george shuckburgh’s Qbfervations

Feet.

The bottle empty or exhaufted till the gage Hood at 29 15 inches]

weighed (determined from four different tnals, and the balance 1 2657.40

turning with tV of a grain) — — — J

Increafe of weight when filled with air, from four trials certain

But the bottle was exhaulted only in the proportion
of 29.15 inches to 29,27 inches; therefore if a perfect
vacuum could have been made, the difference of weight
would have been 1 6.22 grains inftead of 16.1 3 grains.
Again, the water was colder than the air by 20; the one
being 530, and the other only 5 t 0 : now water, from
former experiments, I find to expand about —0|^ with
20 of heat; therefore, if the water had been of the fame
temperature with the air that was examined, the weight of
an equal volume would have been only 13558,5 grains ;
and laftly, 13358.5 divided by 16.22 gives 836^, and
by fo much is water heavier than air in thefe circum-
ftances.

(y) hawkesbee’s experiments made the air 850 lighter than water, the baro-
meter being at 29 7 , and Drt halley iuppoiei ii about S.oo. lVir. caven-
dish, in weighing 50 grains of a r, when the barometer was at 29}, and the
thermometer at 50% concluded the fpeciiic gravity of air to be about 800 alfo.
Now my experiment, reduced to the fame eircumftances with his, would give
817 for this gravity, no great difference in an affair oi inch delicacy.

to do of a grain — —

Bottle filled with water, whole heat was 5 1
Weight of the water, exclufive of the b ttle,

16220.00

13562.60

By

m order to afcerfain the height of Mountains* 561

By former experiments I find the fpeciiic gravity of the quick- ^

filver of my barometers, compared with rain-water in 63° r 13.60610 1
of heat, as, — — — —

And 68 — 53°m5°, corre£l therefore for 15° of expanfion ofl Q1g
quickfilver, — — - — i

Corre£t for 15° of expanfion of air, — — — • °3r

True fpecific gravity of quickfilver, with 530 of heat, 1 3*594

Which multiplied by the ipecifie gravity of air, — x 83^

Feet*

And laflly, A>th of an inch of quickfilver, when the barometer {lands at^
29.27 inches (viz, from 29.22 inches to 29.32 inches) with the tern- r 94.7
perature 53°, is equal to a column of the atmofphere of, • — ■ J

This quantity, according to my barometrical obfervations, is,. — » 93-83

• -to Mr. de luc’s rules, — - — 91.66

wjjfCJr 1 - s' . f ' ‘ • .

We fee here then that the ftatical experiment agrees
with the refult of my barometrical ones to within about
11 inches in ioo feet, and I am not fure that it is not
ffill capable of much farther precifion ; and though per-
haps alone it might carry with it, to fome perfons, a lefs
conclufive teftimony, who reluctantly reafon from the
little to the great, yet, in conjunction with what has been
before Ihewn, I think it has confiderable weight; and I
am the lefs inclined to rejeCt fuch an indirect method of
proof, as I have the great authorities of halley and
newton on my fide'H.

I have

(z) “ Ce qu’il y a d?effentlel a obferver ici,M fays Mr. de luc, “ et vrai-
<c ment digne de remarque, c’eft que par la feule connoiffance des pefanteurs
iC fpecifiques de Fair et du xnercure, halley eft parvenu a une regie ties
Vol. LXVII. 4 D u approchante

5^2 Sir george shucksurgh’s Obfervations

I have thus endeavoured to fhew then that the error
of the theory is — ^411^ when the temperature of the
air is 6i°.4 (fee the table of the refult of the obferva-
tions). It remains therefore, finally, that we deduce a
rule, the error of which fhall be nothing, viz. to find
the temperature wherein the difference of the loga-
rithms of the heights of the barometer, taken to four
places of figures, will give the true difference of eleva-
tion in Englifh fathoms. Previous to this invefligation,
with which I intend to conclude this paper, it will be ne-
ceffary to remark, that by repeated experiments with the
barometer, I find a fmall difference in the equation for
the expanfion of air by a change of temperature, and
even in that of quickfilver from the fame caufe, from
what Mr. de luc’s obfervations have given iSa>. I fhall

s< approchante de celle, qu’u n grand nombre d’obfervations du barometre dans
“ les Cordelieres ont didte depuis a M. bouguer : cependant malgre l’appui
** 1ue ces experiences fe pretent reciproquement, on verra qu’elies etoient encore
“ bien eloignees de fournir une regie generale.” Recherches fur l’Atmofphere,
left. 267.

(a) He indeed made his experiments on the atmofphere itfelf with the
barometer, in order to determine the variations of its denfity ; but fince it
appears that the abfolute denfity of this fluid is different from what he flip-
ped it, it is no bold conjefture to prefume that the degree of its variation
fhould be different alio; and to afcertain this point, I have preferred the
inftrument above-mentioned to the method ufed by Mr. de luc, how direft
foever his may feem; for in determining minute quantities or equations, we
muff not embarrafs ourfelves with the compound effedt of too many caufes at a
tisae.

wot

in order to afcertain the height of Mountains. 563

not here trouble the reader with the experiments at
large, too Ample in themfelves to deferve fuch a detail,
unlefs a future occation fhould render that neceffary, as
the methods here ufed may be met with amongft
hawkes bee’s or Mr. boyle’s experiments; and content
mvfelf with relating only the refult of the different
trials.

1000 parts of air of the temperature of freezing and
preffure of 30^ inches, increafed in volume by an add!-
dition of 1 degree of heat on Fahrenheit’s thermo-
meter as follows :

Number of de-

Expanfion for

i°

-

Obfervations.

grees the air was
heated.

in ioooths
the whole.

of

^ I

I4.6

2.30

2

32.2

2.43

3

40.3

248

With the firft ^

4

46.6

2.45

Mean from the firft

manometer.

5

49*7

2.48

* manometer 2.44.

6

51. 1

2*51

7

23'7

2.36

. e

2.24

r 9

22.0

2.38

\

With another

10

28.0

2.SO

1 Mean from the fecond

manometer, <

1 1

2.34

r manometer 2.42

12

30.1

2.44

1

j

‘ U ,

lI3

22.6

2.44

4D2

The

564 Sir george shuckburgh’s Obfervations

The mean of thefe two forts of obfervations, made
with different infer uments, is 2.43, viz. 1000 parts of
the air at freezing become by cxpanlion from i° of heat

Pts. Pts.

equal 1002.43 or 1002.385 with the ftandard tempe-
rature 39®. 7. Mr. de luces experiments reduced give

Pts.

this quantity equal 1002.23^ (fee Tranf.). It may
be imagined, that I fhould have had a more accurate con-
clulion by making thefe obfervations in greater dif-
ferences of temperature than what is fhewn in the fe-
cond column of the above table ; but it did not appear
fo to me. On the other hand, I found that it was abfo-
lutely neceffary that the lame heat fhould be kept up for
fome hours together, in order that I might be fiire that
the air within the inftrument, the glafs tube that con-
tained it, and the air without it, all had acquired the fame

(h) It has generally been fuppofed, that air expands with each degree of
the thermometer, commencing from the mean temperature 55°; and, in confe-
quence of this, aftronomers have computed tables for correcting their meaa
refraCtions; but, upon reducing the refult of my obfervations to the temperature
55°, we fhall have the correction, of the refraCtion for i° z= totVW or ttt*
Now according to Mr. d_e luc this equation is totjVf — tst? which would
produce a difference of about 4" in the corrected refraCtion, upon an altitude of
S°j with the temperature 3.5 If my numbers may be fnppofed -to deferve equal
confidence, ihe error of the tables in common ufe, in the above- circumftances,
would amount to only half that quantity, and therefore probably will be
thought fcarce worth correcting. I have mentioned this in order to obviate the
tcquc Lu£q.&s that have been drawn by fome perfons from Mr.DE luc’s theory.

uniform

in order to afcertain the height of Mountains . 565

uniform temperature, which in my room I found not
very eafy to effect in heats greater than 70° or 8o°. I
have therefore preferred repeating the experiment with
fmall differences of heat; but fuch, however, as will in-
clude almoft all the temperatures in which barometrical
obfervations are likely to be made, viz. from 320 to 83°,
Xt has been fufpefled, in confequence of fome experi-
ments made by a very ingenious member of this Society,
that air does not expand uniformly with quickfilver ; or
that the degrees of heat fhewn by a quicklilver-ther-
mometer would be expreifed on a manometer, or air-
thermometer, by unequal fpaces in a certain geometrical
ratio. I do not deny this propofition ; but I have alio
very little reafon to aflent to it, if I may trull my own
experiments, which certainly evince that this ratio, if
not truly arithmetical, is fo nearly fo as to occalion no,
fgnfible error in the meafuring of heights with the ba-
rometer; and that is all I contend for. The fmall dif-
ferences that are feen in the above table of this expan-
fion, deduced from a mean of 14° or of 40°, I would
attribute rather to the errors of obfervation than to any
a,6lual irregularity in nature. If, however, this progrei-
fion be infilled upon, it fhould feem, that the. degree of
the air’s expanlion increafes with an increafe of heat;
and that the difference of volume or denfity ' torn 1 : ot

5 66 Sir george shuckburgh’s Obfervations
heat, any where within the limits above-mentioned,
would be about one .part in five thoufand from what I
t take it at a mean. I ihould not have infilled fo long on
this circumltance, but in refpeft to the known accuracy
of the author of this hypothefis. Neither do I find any
reafon to believe, ' that the expanfion of air varies with
its denfity. I have tried air whofe denfity or preflure
was equal to 23f inches, and alfo to forty inches; but the
dilatation, with equal volumes and equal degrees of heat,
was very nearly the fame in both cafes. I might add a
great deal more on thefe manometrical experiments, but
I am afraid it would be more tedious than ufeful. I pro-
ceed therefore to the expanfion of quickfilver.

This experiment was made with a tube, fomething
like a thermometer, but confiderably larger than the or-
dinary fize, and open at one end; it was filled with
quickfilver to a certain height, and then expofed to the
temperatures of freezing and boiling repeatedly, the ba-
rometer being at 30 inches : the difference of the volume
in each inftance was determined afterwards by accu-
rately -weighing the contents. I thus found, that if the
quickfilver at freezing be fuppofed to be divided into
1 31 19 parts, the increafe of volume by a heat of boil-
ing water became equal to 208 of thefe parts = and
~ x ~ - TT~~ ; and fuch would be the expanfion for

each

2

in order to afcertain the height of Mountains . 567

each degree of the thermometer, commencing from the
freezing point, =0,00262 inch on a column of 30
inches of the barometer, if the glafs had fuffered no ex-
pan fion during the experiment. This, however, has
been found to be with 1 8o° of heat = ~ in folidity
(viz. the cube of its longitudinal expanfion) and
_ — x— — = — - — =0,0004.2 inch, for the effedt of the
expanfion of the glafs for i° upon a column of 30
inches ; this added to the quantity before found, which
was only the excefs of the greater expanfion above the
lefs, gives for the true equation for each degree 0,00304
inch when the barometer ftands at 30 inches (c>. Mr. de
luc’s correction in this cafe was 0,00312; a difference
fo fmall that I fhall take no notice of it as to its influence
upon our obfervations. It may deferve a remark here,
that this equation rigoroufly taken is variable according
to the height of the thermometer; for i°, which at

(c) It lias been fufpe&ed, and I believe will appear from very good obferva-
lions, which however I never made myfelf, that the expanfion of quicklilver in
the barometer is not direCtly as the heat fhewn by the thermometer, but in a
ratio lomething different, owing to fame of the quicklilver being converted
into an elaftic vapour in the vacuum that takes place at the top of the Torri-
cellian tube, which preffesupon the column of quickfilver, and thus counteracts
in a fmall degree the expanfion from heat. It does not, however, appear to be
a conliderable quantity, not amounting to above one fixteenth of the whole
cxpanlion in a range of 40° of temperature; I Ihall therefore venture to con-
sider this equation as truly uniform^ lines the error on ten thoufand feet would
mot amount to five.

freezing

^63 Sir GEORGE shuckburgh’s Qb/ervations
freezing is = ~7 of the whole volume, at the tempera-
ture 82° becomes ^4— , a difference indeed that may
fairly be neglected, and which I neglect myfelf; yet I
cannot help obferving, in juftice to Mr. de luc, that his
method of reducing his barometers always to the fame
ftandard temperature, was free from the error I am
fpeaking of.

To conclude, the defeat of Mr. de Luc’s rules being
fuppofed ylll 5, or, which comes to the fame thing, the
correction being + when the temperature of the

air is 6i°.4, and the true expanfion of the air for each
degree being when the heat is 39°-7 ; required to

find the temperature wherein the difference of the loga-
rithms fhall give the true height in Englifh fathoms,
that temperature, according to Mr. de luc, being 39°.74,
and the expanfion r-0“300.

Let t be the temperature 6i°.4; s Mr. de lucts
ftandard temperature; e the expanfion for i°; e the fame,
according to Mr. de luc; a the fuppofed correction of
the rules, and x the temperature fought. We have then
the following formula, t-s x e- e(i> — a = s-x, wherein
proceeding with the above numbers s-x comes out

(d) This fign is negative> becaufe the alTumed 'expanfion e is lefs than the
true one e, and confetjuently tended to increafe the apparent error of the rules;,
had it been greater, « would have been 4- .

in order to af certain the height of Mountains. 5 6-g
8°. 50, and confequently ^=31°. 24 the temperature re-
quired: which, if it fhould be thought convenient, may
be confidered as the freezing point.

In the whole of-hhe above inquiry I have taken no
notice of the effedt of gravity upon the particles of the
air at different diftanees from the earth’s center, which
fhould douhtlefs enter into the account, and which would
occafion the denfity of the atmofphere to decreafe in a
ratio fomething greater than the prefent theory admits
of. In a height of four Englifh miles Dr. hoesley finds
(Phil. Tranf. vol. LXIV.) that the diminution of denfity
or volume from the accelerative force of gravity would be
only ~ part of the whole, or about 48 feet; and I may
add to this, that this eflfedt will be in the duplicate ratio
of the heights, fo that at one mile high it becomes only
three feet. A like effedl takes place alfo below the fur-
face of the earth, as in meafuring the depths of mines,
8cc. with this difference, that here it is but half the quan-
tity; in the former inftance gravity within the earth
being limply as the diftance from the center; they are
both of them, however, circumftances that deferve no
attention in practice.

This would be the place for me to enumerate the
many defiderata, befides thofe already hinted at, that ftill
remain for the perfection of this theory ; fuch as the

Tol. LXVII. 4 E laves

570 Sir george shuckburgh’s Obfervations
laws of heat, that obtain in the different regions of the
atmofphere ; the effedts of moifture, winds, the eledfric
fluid, together with the weight and qualities of the air in
different countries* &c. ; that at the fame time that I am
congratulating the prefent age on one of the molt bril-
liant difcoveries in natural philofophy, I may be under-
flood alfo to encourage every lover of fcience to flill farther
enquiries in a branch of knowledge no lefs ufeful than
ingenious; particularly in a kingdom wherein, from its
commercial interefts, and in confequence its many inland
navigations, every improvement in hydroflatics, the art
of levelling, or geometry, cannot but tend confiderably
to the public benefit. The fources of fcience are not
eafily exhaufted;. multitudes of then? remain wholly
unexplored. If novelty can afford a charm, the path I
am fpeaking of, till of late, has been the leaft frequented ;
witnefs the frefh, important truths in Pneumatical re-
fearches that, from zeal and fafhion, every day’s expe-
rience affords. I might here offer too a tribute of applaufe
(and am fure in concert with this whole affembly) jufliy
due to the indefatigable labours of him whole fleps I
have purfued ; but I arn convinced he will rather hear
me acknowledge our obligations to the ancients than any
panegyric of himfelf. Be the benefit we receive from
them our encouragement to proceed.

7 .

Multum

in order to afcertain the height of Mountains. 571
Multurn egerunt , qui ante nos fuerunt , fed non per ti-
ger unt: mult uni adhuc reflat operis , multumque rejlahit\
nec ulli nato pofl mille facula pracludetur occafto aliquid
adhuc adjiciendiP sen. Epift. 64.

PART II.

I N the fubfequent pages, which I have now the ho-
nour of laying before the Royal Society, I have drawn
up, and I hope in a form the moft commodious, the ne-
ceffary tables and precepts for calculating any acceffible
heights or depths from barometrical obfervations, and
without which I thought the preceding memoir would
be incomplete ; referring, however, to that for the proofs
or elements from whence the tables have been com-
puted. And herein I have endeavoured to adapt myfelf
to the capacity of fuch perfons as are but little conver-
fant with mathematical computations, but who may have
frequent opportunities of contributing fomething to the
advancement of fcience by experiments with this ufeful

4 E 2 inftru-

572 Sir george shuckburgh’s Obfervations
inftrument, which is now become nearly in as common
polfeffion as a pocket watch, I have induftrioufly
avoided the method of logarithms, propofed by Dr. h al-
ley, and adopted by Mr. de luc, both becaufe fuch
tables are not in the hands of every body, and becaufe I
have perceived that many perfons of a philofophical
turn, though dulled only in common arithmetic, have
been frightened by the very name : a method lefs popu-
lar, however elegant, would have been lefs generally
ufeful. To thefe tables is fubjoined a lift of feveral alti-
tudes, as determined by the barometer : this will ferve to
fhew the ufe I have made of the inftrument, and will at
the fame time exhibit the level of a great numbfer of
places in France, Savoy, and Italy, and, as I think, be no
improper fupplement to exemplify the rules. It might
have been expected that I fhould have faid fomething on
the theory of barometrical obfervations, and have laid
down the laws and principles on which it depends ; but
as that has been fo amply done by other writers of in-
contefted authority, I fhall content myfelf with inferring
only the following propofitions.

i ft, The difference of elevation of two places may be
determined by the weight of the vertical column of the
atmofphere intercepted between them.

3

ad, If

in order to ascertain the height of Mountains .■ 573

2d, If then the weight of the whole atmofphere at
each place can be afcertained, the weight of this column,
viz. their difference, will be known.

3d, But the height of the quickfilver in the barome-
ter expreffes the total weight of the atmofphere in the
place of obfervation; the difference, therefore, of the
height of the barometer, obferved in two places at the
fame time, willexprefs the. difference of elevation of the
two places.

4th, But further, the weight of this column of the
atmofphere is liable to fome variations, being diminifhed
by heat, and augmented by cold; and again, a fimilar
alteration takes place in the column of quickfilver,
which is the meafure of this weight.

5th, If then the degree of thefe variations can be de-
termined, and the temperature of the air and quickfilver
at the time of obfervation be known, the weight of this
column of air, or the difference of elevation of the two
places, will be concluded as certainly as if the gravity of
thefe two fluids, with all heats, remained invariably the
fame: this is the whole myftery of barometrical mea-
furement.

A

574 <S» george shuckburgh’s Obfervatiom

APPLICATION.

The height of the barometer in Englifh inches at any
two places at the fame inftant, and the heat (according
to Fahrenheit’s thermometer) to which it is expofed,
being known, together with the temperature of the air
at each place, obferved with a limilar inftrument; re-
quired the difference of elevation of the two places in
Englifh feet.

RULE.

Precept the iff, With the difference of the two thermo-
meters that give the heat of the barometer (and which,
for diilinCtion fake, I iliall call the attached thermome-
ters^) enter table I. with the degrees of heat in the
column on the left hand, and with the height of the

barometer in inches, in the horizontal line at the top; in
the common point of meeting of the two lines will be
found the correction for the expanlion of the quicklilver

(e) It is fcarce necelTary to remark, that, in order to make good conclufive
obfervations, it is proper to be furnifhed with two barometers, and four ther-
mometers; viz. one attached or inferted in the frame of each barometer; and
the other two detached from them, in order to take the heat of the open air;
for it will feldom be found, that the thermometer in the frame of the barometer
and that in the air will Hand at the fame point, and for a very evident realon.

in order to afcertain the height of Mountains. 575
by heat, expreffed in thoufandth parts of an Englifh
inch; which added to the coldeft barometer, or fubtradted
from the hotteft, will give the height of the two barome-
ters, fuch as would have obtained had both inftruments
been expofed to the fame temperature.

Precept the 2d, With thefe corrected heights of the ba-
rometers enter table II. and takeout refpedtively the num-
bers correfponding to the neareft tenth of an inch ; and if
the barometers, corrected as in the firll: precept, are found
to Hand at an even tenth, without any further fradtion, the
difference of thefe two tabular numbers (found by fub-
tradting the lefs from the greater) will give the approxi-
mate height in Englifh feet. But if, as will commonly
happen, the corredt height of the barometers fhould not
be at an even tenth, write out the difference for one.
entire tenth, found in the column adjoining, intitled
Differences’, and with this number enter table III. of pro-
portional parts in the firft vertical column to the left-
hand, or in the j ith column, and with the next decimal
following the tenths of an inch in the height of the.
barometer ( viz. the hundredths) enter the horizontal
line at the top, the point of meeting will give a certain
number of feet, which write down by itfelf; do the fame
by the next decimal figure in the height of the barome-
ter ( viz. the thoufandths of an inch) with this difference,

(hiking

%

57 6 Sir gegrge siiuckburgh’s Obfermtiom
ftriking off the laft cypher to the right hand for a frac-
tion; add together the two numbers thus found in the
table of proportionable parts, and their fum i'ubdudt
from the tabular numbers juft found in table II.; the
differences of the tabular numbers, fo diminifhed, will
give the approximate height in Englifh feet.

Precept the 3d, Add together the degrees of the two
detached or air-thermometers, and divide their fum by
2, the quotient will be an intermediate heat, and muft
be taken for . the mean temperature of the vertical co-
lumn of air intercepted between the two places of ob-
servation: if this temperature fhould be 31°^ on the
thermometer, then will the approximate height, before
found, be the true height ; but if not, take its difference
from 3 10^, and with this difference feek the correction
in table IV . for the expanfion of air, with the number of
degrees in the vertical column on the left hand, and the
approximate height to the neareft thoufand feet in the
horizontal line at the top; for the hundred feet ftrike off
one cypher to the right hand ; for the tens ftrike off two ;
for the units three: the fum of thefe feveral numbers
added to the approximate height, if the temperature be
greater than 31°^, fubtra&ed if lefs, will give the correCt
height in Englifh feet. An example or two will make
this quite plain.

example

in order to afcertain the height of Mountains . 577

EXAMPLE I.

Let the height of the barometer, obferved at the bot-
tom of a mountain be 29.4 inches, the attached ther-
mometer 50°, and the heat of the air 450; at the fame
time that at the top of the mountain the barometer is
found to hand at 25.190 inches, the attached thermo-
meter at 46°, and the air-thermometer at 39°^; re-
quired the height of the mountain in Englifh feet.
Set the numbers down in the following order;

4 F

Vol. LXVII.

Obfer-

Sir George sHucKBtrRGH’s Obfervatioirt

Obfervation at the bottom.

Barometer. Therm.

attached.

In.

29400 50°

46

DifF. of the two attached thermometers, 4

Therm,
ki the air.

45*

Obfervation at the top.

Barom. '‘Therm. Thferrti.

attached. in the air.

In.

^ 25.190

Corre£l for the cliff, of the 1
two attached therm, viz. 40, J ^ 10

Height of the uppermoft^
barometer, reduced to the I
fame heat as the lowermoft, f25-200
viz. 56°, — — J

46° 39°i

45

2)841(42! mean heat.

31! ftandard heat.

11 difference.

Tabular number, fee tab. II.

correiponding to, —
The fame, correfponding to

Approximate height in feet*
■CorrettLn for u°of heat on 4016 feet, add, —

Correct for 1 1°, fee tab. IV.
on 4000 feet 106.9

on 16 — 4-3

or on 4016 4- 107.4

In. Feetsu

J 25.200 =-6225.0
29400 = 2208.2

4016.8
— 1074

Correct height of the mountain — — — 4124.2

Now the difference of the attached thermometer 50°
and 46° is - 40; and againft this number, in table I. in
the column for 2 5 inches (being the height of the baro-
meter in this cafe) I find 10, which added to 25.190, as
this barometer was the coldeft, gives 25.200 inches for
1 the

in order to af certain the height of Mountains, 579
the height of the uppermoft barometer reduced to the
fame heat as the lowermoft: and in table II. oppofite to
25.200 inches and 29.400 inches, 1 find refpeCtively
6225.0 and 2208.2; their difference 4016.8 is the ap-
proximate height in feet. The degrees on the ther-
mometer in the open air, 39°^ and 45 0 being then added
together, and afterwards divided by 2, give for the mean
temperature of thefe obfervations 42°^, or n° above
the ftandard temperature, 3 1°| : and laftly, the correction
for 1 1°, in table IV. on 4000 feet I find = 106.9, and
on 16 feet = 0.5; that is, 107.4 f'eet e(lua^ ^ie whole
correction, which added to 4016.8 gives 41 24.2 feet for
the correCt height of the mountain.

EXAMPLE 11.

Suppofe the height of the barometer at the top of a
rock had been obferved at 24.178, the attached ther-
mometer at 570. 2, the air-thermometer at 56°; the ba-
rometer below at 28.1318 inches, the attached thermo-
meter 6i°.8, the detached one 63°. 9 ; what is the height
of the rock?

4 F 2

Obfer-

5 Bo Sir George shuckburgh’s Obfervations
Obfervation at the bottom.

Barometer, Therm. Therm.

attached. detached*
In.

28.1318 6i°.8 63°.9

57*2

Difference of the two attached thermometers, 4.6

Obfervation at the top.

Barom.

In.

241780

CorreCt for the diff. of ^

the two attached therm. I 01 1 2

viz. 40. 6, — J

Height of the uppermoft ^
barom. reduced to the I Q
fame heat as the lower- r24 iy92
moft, namely 6ic.8, J —

Therm. Therm,

attached. detached.

57°.2 56.0

63-9

2)II9*9(59*95 mcan

31.24 ftandard temp.

28.71 difference.

Tabular number, cor- 1
relponding to, J 2 4* 1 000

The famey-fee tab. III. 800 86. o

90 9-7

.2

24.1892

T abular number, cor- 1 n
refponding to, ) 28.1000

The fame, fee tab. III. 300 28.0

10 0.9

— — 8 0.7

28- 1318

And 33570 feet taken from —

Leaves the approximate height in feet.
Correction for 2$°7 of heat on 3935 ft.

CorreCt height of this .mountain,

Feet.

Diff.

7388.0

107.9

]-95 9

7292.1

3386.6

)

92.6

29.6

CorreCt for 28°.7, fee tab. IV.

)

•j 3000 = 204. 1

28° on !> 900=: 61.2

33 57 °

J 35= 2.4

7292. i-

3Co° — : 5-1

0.7 on !> 900= 1.5

3935-1

j 35=

+ 274-3

28.7 on 3935 274 3

4209-4

This

in order to afcertain the height of Mountains. 581

This laft obfervation was actually made, and the
height geometrically was determined to be 421 1.3 feet,
not quite two feet different. In this example it will be ob-
ferved, that as the height of the barometer is fet down to
four places of decimals; the tabular numbers, anfwering
to every tenth only, are corrected by means of table III.
of proportional parts, for the remaining decimals 8, 9,
and 2, in one place; and 3, 1, 8, in the other; and their
fum is fubducted from the numbers found in table II.
And laftly, that in finding the correction for 2 8°. 7 of
heat, the fraction fz is confidered as fo many units, and
another decimal is ftruck off; thus the correction on
3000 feet for 70 is 51; but for ^ it becomes 5.1, and
fo of the reft.

EXAMPLE III.

In the upper gallery of the dome of St, Peter’s church
at Rome, and 5 o feet below the top of the crofs, I ob-
ferved the barometer, from a mean of feveral obferva-
tions, 29.5218; the thermometer attached being at
56°. 6, and the detached one at 570; at the fame time
that another, placed on the banks of the Tyber one foot
above the furface of the water, flood at 30.0168, the
attached thermometer at 6o°.6, and the detached one at
6o°.2; what was the total height of this building above
the level of the river?

Obfer-

$}> GEOB.GF. SnUCKBURQH’s 0 hfwVCTtiOM

Cbfervation beteiw, at one foot above the Tyber,

Bare, vr'er.

Therm,

attached,

60.6
566

.difference of the two attached thermCmctcts, 4.0

In.

30-0168

Therm,

detached,

6o°.2

Obfervation above, in the gallery of St. Peter's church.

Correft for the diff. of J
rm. J

29.5218

the, two attached therm. J *"*"

120

TIeightof the uppermofl 1
bardm- .reduced to the
'heat of the lowermofl
viz. 60.5, —

29-5338

56.6 57.0

6o.-2

2)1 17.2(58.60 mean heat.

31.24 flandard temp.

2.7.36 difference,

Tabular numbers cor- 1
refponding to, — J 29*5°°°
200 26.4

3° 2

8 *

Feet.

2119.7

.6^ — 29.7

Diff.

«8.2

29-5338

Tabular numbers cor-
refponding

numbers cor- 1
ling to, — J 3°-

0000

100 8.7

60 5

8

:l}-

7J

2090.0
f 68 1.7
14.6

86.7

30.0168

1667.1
2090.0

Approximate height, 422.9

Corre&ion for 2 7°4 of heat on 42 2 feet, -f 28.0
Difference of height of the barometers, 450.9

Loweft barom. flood 1 foot above the river, -f 1.0
Top of the crofs above the gallery was, -f 50.0
Total height of the top of the crofs \

above the river Tyber, J 5OI»9

The fame meafured the fame day geo- "1
metrically was, — * —

Gonedlion for 2 7°.4
„0 J 400 zr 26.2
*7 °n { 22 = ..4
0.4 on 400- z: .4

27^4 on 422= 28.0

502.2

When

in order to af certain the height of Mountains. 583
\vhen the difference of the heights of the quickfilver
in the two barometers happens not to exceed -f or even
3^of an inch (and this will frequently be the cafe in level-
ling flat countries, or meafuring fmall heights) in fuch
circumftances the moft convenient way of reducing the
obfervations will .be by means of the column of differences
only; thofe numbers exprefling the length of a column
of the atmofphere which correfponds to -f of an inch of
quickfilver, at any afligned height of the barometer.

EXAM P L E IV.

Suppofe the following obfervations had been made at
the top and bottom of any eminence ; viz. at the top,
barometer 29.985 inches,, attached thermometer 70'f.
detached thermometer 76°; and below, barometer at
30.08 2, attached thermometer 71 rt, and the detached •
one 68° ; what was the height of the eminence ?

Obfer-

584 Sir george shuckburgh’s Obfervations

Obfervation below.

Barometer.

Therm.

Therm.

attached.

detached.

In.

30.0820

71.0

68.0

70.5

Difference of the two attached therm.

Obfervation at the top.

Barometer.

Therm.

Therm.

attached.

detached.

In.

<?

0

„ „ , 29.9850

7°. 5

76 .a

Correct for o°.5 of heat, 4- .00 1 5

68.0

Take — - — 29.9865

2)144.0(72.0 mean heat.

From — — 30.082a

31.2 ftandard temp,

Remains the difference -j

4-40.8 difference.

or fall of quickfilyer in > 0.0955

the barometer, — J

The difference for at 30 inches z:

86.7 feet.

Correction for 41°.

\

Feet. Ft.

Feet.

o r 80 — 8.0

Therefore, for 0900 — .

78.0

41 on i 2.7= .3

0050 — _

4-3

— ■ . - . —

0005 — —

0.4

410 on 82.7=8.3

Therefore, 0955.111011 of quickfilyer, —
Correction for4i° on 82.7 feet.

82.7 the approximate height.
+ 8.3

Giv

res

— 9 1 .0 zz the true height.

Now this was the height of the Tarpeian rock, or the
weft-end of the Capitol-hill in Rome, above the con-
vent of St. Clare, in the Strada dei fpeccbi.

The preceding rules for determining heights above
the furface of the earth will, I prefume, anfwer equally
well. for meafuring depths below it.

TABLE

in order to af certain the height of Mountains . 585

table 1. For the expanfion of quickfilver by heat,

fee p. 574.

Degr.

Height of the barometer in inches.

Therm.

20

21

22

23

24

25

26

27

28

29

3°

31

32

I

2 0

2.1

2.2

2*3

2.4

2.5

2-6

2.7

2.8

2.9

3*°

3*i

3*2

2

4*1

4-3

4*5

4*7

4-9

5*i

5*3

5*5

5*7

5*9

6.1

6*3

6*5

3

6.1

6.4

6.7

7.0

7*3

7*6

7*9

8.2

8*5

8.8

9.1

9.4

9*7

4

8.1

8.5

8.9

9*3

9*7

IO.I

10.5

1 1 .0

11.4

11.8

12.2

12.0

13.0

5

IO.I

10.6

1 1. 1

11.6

12. 1

12.7

13.2

i3*7

14.2

14.7

X5*2

x5*7

16.2

6

12.2

12.8

x3-4

14 0

14.6

15*2

15.8

16.4

17.0

17.6

18.2

18.8

*9*5

7

14.2

14.9

15.6

1 6.3

17.0

x7*7

18.4

19.2

19.8

20.6

21.3

22.C

22.7

8

l6.2

17.0

17.8

18.6

x9*4

20.2

21.0

21.9

22.7

23*5

24*3

25.2

25*9

9

l8.2

19.2

20. 1

21.0

21.9

22.8

23*7

24.6

25.6

26.5

. 27.4

28.3

29.2

10

20.3

21.3

22.3

23-3

24.3

25-3

26.3

27.4

28.4

29.4

3°*4

3r,4

32.4

11

22.3

23*4

24-5

25.6

26.7

27.8

28.9

30.1

3 1#2

32*3

33*4

34-5

35- 6

12

24*3

25. 6

26.8

28.0

29.2

3°-4

31.6

32,9

34* 1

35*3

36.5

37-6

38.9

13

26.3

27.7

29.0

3°-3

31-6

32-9

34-2

35-6

36-9

38.2

39-5

40.8

42.1

14

28.4

29.8

3x-2

32,6

34-o

35 4

36.8

38-4

39-8

41.2

42.6

43-9

45-4

i5

3°*4

3l-9

33-4

34-9

36-4

37*9

39-4

41. 1

42.6

44.1

45-6

47.1

48 6

16

32*4

34- 1

35 6

37*2

38.8

40*5

42.0

43-8

45 4

47*o

48.6

5°-3

5X*8

17

34-5

36.2

37-9

39*6

4i-3

43-°

44-7

46.6

48-3

50.0

5i*7

53-4

55*1

18

36-5

38-3

40.1

41.9

43-7

45*5

47-3

49-3

Si-i

52.9

54*7

56.5

58*3

x9

38-5

40.5

42.3

44.2

46.I

48.1

49-9

52.1

54-°

55*9

57-8

59-7

61.6

20

40.6

42.6

44.6

46.6

48.6

50.6

52.6

54-8

56.8

58.8

60.8

62-8

64.9

21

42.6

44-7

46.8

48.9

51.0

53*2

55-2

57 5

59.6

61.7

63 8

65-9

68.1

22

44.6

46.9

49* 1

S!-3

53-5

55*7

57-9

60.3

62.5

64*7

66.9

690

7 x*4

23

46.6

49 0

5X*3

53-6

55-9

58.2

00.5

63.0

65-3

67,6

69,9

72.2

74.6

. O

24

48.6

Si-*

53’5

55-9

58*3

60.8

63.1

65.8

68.2

70.6

73-0

75 4

77.0

25

S°*7

53-2

55-B

58.2

60.7

63.2

65-7

68.5

71.0

73*5

76 0

78*5

81. 1

26

52.7

SS-4

50.0

60.. 5

63.1

65*8

68.3

712

73-8

76.4

79°

81.6

84 *3

27

54-7

57-5

6°.3

62.9

65.6

68.3

7 1.0

74.0

76.7

79'4

82.1

84.8

87-5

28

56.8

59-6

62.5

65.2

68.0

70.8

73-6

76.7

79-5

82.3

85.1

87.9

9°-7

29

58.8

61.8

64.7

67-5

70.4

73*3

76.2

79-5

82.4

85-3

88.2

91.1

94.1

3°

60.8

63-9

66.9

69.9

72.8

75*9

78.9

82.2

85.2

88.2

912

94.1

97-3

31

62.8

66,0

60.1

72.2

75-2

784

81.5

84.9

88 0

91. 1

94.2

97*4

100.5

32

64.8

68. 2

71.4

74-6

77*7

81.0

84.2

87.7

90.9

94.1

97 3

100.5

103.8

33

66.9

70.3

73-6

76 9

80. 1

83*5

86.8

90.4

93-7

97.0

100.3

103.6

IOJ.O

34

68.9

72.4

75-8

79.2

82.5

86.1

89.4

93-2

96.6

100.0

l03*4

106.7

I 10-3

35

70.9

74-5

78.0

81.5

84.0

88.6

92.0

95-9

99.4

102.9

106.4

109.9

11 3 5.

O

36

7 3.0

76.7

80.2

83.8

86.4

91. 1

94.6

98.6

102.2

105.8

109.4

113.1

1 10.0

37

75-°

78.8

82.5

86.2

88.9

93*6

97 3

IOI.4

105. 1

108.8

112.5

I 10.2

120.0

38

77.0

80.9

84.7

88.5

9X*3

96.2

99.9

IO4. I

107.9

1 1 1.7

ii5*5

1 x9*3

123.2

39

79.0

83.1

86.9

9O.8

93*7

98.7

102.5

I06.Q

1 10 8

U4.7

i 18.6

122.5,

126.5

40

I81. 1

85.2

89.2

93 2

97.2

101.2

105.2

IO9.6

113*61

|i!7.0

12 1 .6

i2«; 6|

VOL. LXVII. 4G , TABLE

586 Sir george shuckburgh’s Obferva tiorts

table ii (f>. Giving the approximate height in Englifh
feet, adapted to the temperature 3i°24 of Fahren-
heit’s thermometer.

Height
of the
Barom.

Height.

Diff.

Height
of the
Barom.

Height.

Diff.

Height
of the
Barom.

Height.

Diff.

Inch.

1. —

2. —

3- —

4- —

5-
6.—

7-—

'8. —

9* —

10. —

11. —

12. —
J3-“-

15.00

Feet.

90309.0
72247.2

61681.8
54185 4

48370.8

43619-9

39603.1
.36123.6

33°54-4

30309.0

27823.4

2555s-1

23472.4

21541-3

r9743-5

18062

10565

7496

5814

4761

4017

348.0

3069

2745

2484

2267

2086

1931

1798

Inch.
16. 10
20
30
40
50
60
70
80
90
16.00
10
20
30
40
5°

Feet.

1 957°-4

19398.4

19227.5

19°57-7

18889.1

18721.5

18555-0

18389.6

18225.2
1 806 1.8

17899.4

17738.1

17577-7

17418.4
17260.0

I73*1

172.0

17°*9

169.8
168.6
167 6
166.5

165.4
164*4

1634

162.4

161.3

160.4

*59-3

158.4

Inch.
16.60
70
80
90
17 00
10
20-

3°

40

5°
60
70
80
90
1 8.co

Feet.

17102.5

16946.0
16790.4
^635.8

16482.1
16329-2
1 6 1 7 7-3

16026.2
15876.0

15726.7
!5578-2

15430.6

15283.8
I5137-8
14992 6

I57*5
*56 5
*55-6

154.6

1 53 7
r52*9

151.1

150.2

149-3

148.5-

147.6
146.8
146.0
145.^

(f) This table bears Tome analogy to the tables of logiftical logarithms, being
nothing more than the differences of the logarithms of the height of the
barometer from the logarithm of 32 inches multiplied by fix%, I have chofen
the logarithm of 32 for my term, of comparifon, that being the greateft pro-
bable height that the barometer will ever be feen at, even at the bottom of the
deepeft mines. Had I taken the mean height of the quickfilver at the level of
the lea, it is true the numbers in the table would have more truly reprefented
the heights in the atmofphere, correfponding to the given height of the quick-
iilver; but then, in computing fmall depths or heights from the furface of the
iea, we Ihould have been obliged fometimes to have changed the IT ns in the
operation, which appeared to me lefs convenient. The mean height of the
barometer at the level of the fea, from 132 observations in Italy and in Eng-
land, is 30.04 inches^ the heat of the barometer being 550, and the air 62°;
-fo that the term of comparifon in this table, viz. 32 inches, correfponds to an
imaginary point within the earth at 1647 ^eet Eslow the furface of the fea.

TABLE

in order to ascertain the height of Mountains. 587

table 11. continued.

Height
of the
Barom.

Height.

Diff.

Height
of the
Barom.

Height.

Diff.

Height
of the
Barom.

Height.

Diff. :

Inch.

18.10

20

30

40

5°

60

70

80

90

19.00
10
20
30
40

5°

60

70

80

90

20.00

IQ

20

30

40

50

60

70

80

90

21.00
IO
20
30
40-
50
bo
70
80

9°

Feet.

14848.3
i47°4-7

14561.9

•44I9-9

14278.7
14138.2

13998.5

•3859-5

13721.3
•3583-8

13447.0

13310.9

13175.6
•3°4i-i

12906.9
12773 6

12641.0
$25,09:. 1

1233.7.0
$2247.2

12117.2

1 1987.9
i 1859.2

11731.2

11603.8
II477 O

1 1350.0

1 1225.2
1 1 100.2
10975-8

10852. 1

10728.8

10606.2

1 0484. 2

10362.7

10241.8

10121.4
10001.6

9882.4

144-3

143.6

142.8

142.0

141.2
•4°-5
•39-7

139.0

1 28.2

•37-5

136.8

136. 1

•35-3
•34-5
• 34- 2

•33-3

132.6

131.9

•31 3

130.6
130.0

129.3

128.7
128.0

127.4
126.8

126.2
125.6
125.0
124-4
123.7
123-3
122.6
122.0

121.5

120.9
120.4
1 19 8

1 19.2

Inch.

22.00
10
20

3°

4°'

5°

60

70

80

90

23.00
10
20

3°

40

50

60

70

80

90

24.00
10
20

3°

40

5,0

60

70

80

90

25.00
10
20
3°
-4°
50
60
70
80

Feet.

9763.6

9645.5

9527.8

9410.7

9294.1

9178.1
9062 .5:
8947.4

8832 9

8718.9

8605.3

8492.3

8379-7

8267.6

8156.0

8044.9

79343

7824.1

77 !4-4

7605.1

7496-3

7388.0

7280.1

7172.6

7065.6
6959.Q

6852.9

6747.2

6641.9

653 7 °

6432.6

6328.6

6225.0

6121.8

6019.0

5916.6

5.814.6

57 •3-°

561 1.8

1 18.8

1 18. 1
117-7

117.1

r 1 6.6

1 16.0

115.6

115.1

• 14-5

1 14.0

113.6

1 1 3.0

1 12.6

112. 1

1 1 1.6

1 1 1 . 1

1 10.6

1 10.2

109.7

109-3

108.8

108.3

10 7-9

107.5

107.0

106.6

106. 1

105.7
io5-3

104.9
104.4-

104.0

103.6

103.2

102.8

102.4

102.0

101.6

101.2

Incli.

25.90

26.00
10 :
20

' 3°

40

5°

60

70

80

90

27.00
10
20

3°

40

5°

60

70

80

90

28.00
10
20

3°

40

50

60

70

80

90

2Q.OO

10

20

3°

40

50

60

7°

Feet.

55u-°

5410.4

5310.6
521.0.9

5 1 1 1.6

5012.8
4914.2

4816.1

47i8-3

4620.9

4523-9

4427.2

4330-8

4234-9

4139.2
4044 0

3949.0

3854-5

3760.2

3666.3

3572-7

3479-5

3386.6

3294.0

3201.8

3109.9

3Dl8-3

2927.0

2836.1

2745*4

2655.1

2565.1
2475-4
2386.0

2296.9
2208 2
2H9.7 |

2031.5 j
i943-& 1

ioq.8

100.6

99.8
99-7
99-3 i

98.8

98.6
98 I
97 8

97 4

97.0

06.7

96.4
9-5-9
95-7
95-2

95.0

94-5
94-3
93 9
93 6
93-2
92 9
92.6
92 2
9I*9

91.6
9I-3
9°*9

90.7

9°*3

90.0

89.7

89.4

89.1

1 B8.7

; 88.5
8S 2

S/-9
|

4 G s

TABLE

588 Sir george shuckburgh’s Obfervations

table 11. continued.

Height
of the
Barom.

Height.

DifF.

Height
of the
Barom.

Height.

DifF.

Height
of the
Barom.

Height.

DifF.

Inch.

29.80

90

30.00

10

20

30

40

SQ

Feet.

1856.0

1768.7

1681.7

*S95-o

1508.6
1422.4

1236.6

1251.0

87.6

87-3

87.0

86.7
86.4
86.2

85.8
85.6

Inch.

30.60

70

80

90

31-00

10

20

3°

Feet.

1165.7

1080.7
996.0

91 1*5
827.3

743-4

659-7

5763

85-3

85.0

84.7
84-5

84.2

83-9

83.7
83-4

Inch.

3!-40

5°

60

7°

80

90

32.00

Feet.

493 2
4104
327-8

245.4

163.4
81.6
00.0

83.1
82.8
82 6
82.4

82.0

81.0
81.6

TABLE

in order to af certain the height of Mountains. 589 ,

table hi. Gf proportional parts.

Diff.

2

3

4-

5

6

7

8

9

Diff.!

1 1

1 2

3

4

5

6

1

8

9

81

*1

l6

24

32

40

49

57

6S

73

106

1 1

21

32

t-2

53

6474

85

95

82

l6

25

33

4i

49

57

66

74

107

1 1

21

32

43

53

64

75

86

96

83

8

n

25

33

41

50

S8

66

75

108

1 1

22

32

43

54

65

76

86

97

84

8

li

25

34

42

5°

59

67

76

109

11

1

22

n -■

oz

44

54

65

76

87

98

85

8

17

25

34

42

5i

59

68

76

1 10

11

lo

I

33

44

55

66

77

88

99

86

9

17

26

34

43

52

60

69

77

hi

1

22

33

44

55

67

78

89

100

s?

9

17

26

35

43

52

61

7°

78

112

22

34

45

56

67

78

90

IOI

88

9

18

26

35

44

53

62

70

79

1 13

1 1

23

34

45

5^

68

79

1

90

102

89

9

18

27

36

44

53

62

7i

80

114

1 1

23

34

46

57

68180

j

91

i03

90

9

18

27

36

45

54

63

72

81

“5

1 1

23

34

46

57

69 80

92

103

91

9

18

27

36

45

55

64

73

82

116

12

23

35

46

58

7081

93

104

92

9

18

28

37

46

55

64

74

83

117

112

23

35

47

58

70 82

94

105

93

9

l9

28

37

46

56

65

74

84

1 18

12

24

35

47

59

7 1 83

94

106

94

9

19

28

33

47

56

66

75

85

ri9

12

24

36

48

59

7I|S3

95

107

95

9

*9

28

38

47

57

66

76

35

120

12

24

36

48

60

72!84

96

108

96

10

*9

29

38

48

58

67

77

86

121

12

24

36

48

60

73 85

97

109

97

10

*9

29

39

48

i8

68

73

87

122

12

24

37

49

61

73;SS

98

I 10

98

10

20

29

39

49

59

69

78

88

J23

12

25

37

49

61

7486

93

III

99

10

20

3°

40

49

59

69

79

89

124

12

25

37

50

62

00

“4-

99

II 2

100

10

20

3°

40

5o

60

70

80

90

-25

12

25

37

50

62

75

87

ICO

I 12

IOI

10

20

30

40

50

61

71

81

9i

126

*3

to c

3£IS°

63

76

88

IOI

il3

102

IO

20

3i

41

I5-1

61

71

82

92

127

|25

38

51

63

76

89

102

114

103

IO

21

31

41

i*1

62

72

82

93

128

|

*3

26

38

5i

64

77

9°

102

“5

'104

IO

21

3 1

4*j52

62

73

83

94

129

33

26

39

52

64

77|9°

103

1 16

io5

10

21

31

42 'S'2

63

73

84

94

130

*3

2fc

39I52

io5

1781

91

104

1 17

table

5Q0 Sir george shuckburgh’s Observations

table xv. For the expanfion of the ah, or correc-
tion of the uppermoft height, fee p. 576.

i

Deg-

-

Approximate height in feet

•

-

O

1000.

2000.

3000.

4OOO. !

1

I 5°°°-

6000. |

7000.

8000. ‘

9000.

I

2.4

4.9

7-3

9-7

12-1

146

17.0

19.4

21.9

2

4.9

9-7

14.6

194

24-3

29.2

34 0

38-9

43-7

3

-7-3'

14.6

21.9

29.2

36-4

| 43-7

5x-°

58.3

65.6

4

9-7

19.4

29.2

38.9

48.6

58 3

68.0

77.8

87-5

5

12. 1

24-3

36-4

48.6

60.7

72.9

85.0

97.2

I09*3

6

14.6

29.2

43-7

58.3

72.8

87-5

102.0

1 16.6

I31,2

7

17.0

34-°

51.0

68.0

85.°

102. 1

1 19.0

136.1

i53°

8

19.4

38.9

58-3

77.8

9-7- 1

1 16.6

136.0

*55-5

174.9

9

21.9

43-7

63.6

87-5

I09*3

I31-2

i53°

I75-0

196.8

10

24-3

48,6

72.9

97.2

121.5

i45 8

170. 1

194.4

218.7

u

26.7

53-5

80.2

106.9

!33 6

160.4

187.1

213 8

240.6

12

29.2

58-3

■87-5

I l6.6

145.8

*75-0

204.1

233-3

262 4

*3

31-6

63.2

94.8

126.4

!5 7-9

1 89 5

221. 1

252.7

284.3

14

34-o

68.0

102. 1

136.1

I70.I

204.1

238.1

272.2

306.2

i5

36-4

72.9

I09-3

145.8

l82.2

218.7

255-1

291.6

328.0

16

38.8

77.8

1 16.6

JS5-5

194*3

233-3

272.1

3‘LO

349*9

- H

41*3

82.6

123.9

165.2

206.5

247.9

289.1

33°-5

371-7

18

43-7

87.5

131.2

i75-o

2 1 8.6

262.4

s°6. 1

349 9

393*6

19

46.1

9^-3

*38-5

184.7

230.8

277.0

323-J

3^9-4

4I5*5

20

48.6

97.2

145.8

194.4

243 o

291.6

340.2

388 8

437*4 |

21

5 1 -°

102.1

204.1

255-1

306.2

357-2

408.2

459*3

22

53*5

106 9

160.4:

213.8

267.3

320.8

374 2

427.7 1 481.I

23 ’

55*9

III $

167.7

223.6

279.4

335*3

391.2

447 1

5°3.o

24

58.3

I l6*6

I75-°

233*3

291 6

349-9

408.2

466.6 I

524-9

25

60.7

121. S

i8o.2

243.0

3°3-7

364 5

42S 2

48 6 0 J

54^-7 !

TABLE

in order to aj certain the height of Mountains. 591

table IV; continued.

Deer,

O

Approximate liei

glit in feet.

0

1000

2000.

3000.

4000

‘ 5000.

6000.

7000,

8000.

9000.

26

63.1

126.4

189.5

252.7

3!5-8

379* 1

442.2

5°5- 4

568.6

27

65,6

131.2

196.8

2-6 2.4

328.0

393-7

459 2

524-9

59°-4

28

6s.o

136.1

204 1

272.2

340.1

408 2

476.2

544*3

612.3

29

70.4

140.9

211.4

281.9

352 3

422.8

493-2

565.8

634.2

3°

72.9

145.8

218.7

291 6

364-5

437 4

510.3

583.2

656.1

3i

75-3

IS°-7

226.0

301.3

376.6

452.0

527-3

602.6

678.0

32

77.8

*55 5

233-3

31 1-°

388.8

466.6

544-3

622.1

699.8

33

80.2

160.4

240 6

320 8

400. 9

480. 1

56i-3

641.5

721.7

34

826

165.2

247.9

330-5

4131

495-7

578-3

661 0

743-6

35

85 0

170.1

255-x

340.2

425-2

510.2

595-3

680.4

765-4

36

87.4

1 75-°

262.4

349-9

437-3

524.8

612.3

699.8

787-3

37

89.9

179.8

269.7

359-6

449-5

539-4

629.3

7 1 9-3

809. 1

33

92-3

184.7

277.0

369 4

461.6

553-9

646.3

738-7

831.0

39

94-7

189.5

284.3

379*1

473- 8

568.5

663.3.

738-2

852.9

40

97.2

194.4

291.6

388.8

486.0

583-2

480.4

777.6

874-8..

41

99 6

J99-3

298 9

398 S

498.1

597-8

697 4

797-0

896.7

42

102-1

204.1

306.2

408.2

5IO-3

6l2 4

714.4

816.5

918.5

43

104-5

2O9.O

3*3 5

418.0

522.4

626.9

931-4

835-9

940.4

• - 44

106.9

213.8

32° 8

427.7

5.34-6

641-5.

748-4

8554

962 3

45

2l8.7

328 0

437-4

546.7

6-56..I

765 4

874.8

984.1.

46

5-1 1..7

223 6

335-3

447. 1

558.8

670.7

782 4

894-2

; 1 00.6 ■ G

47

1 14.2

228.4

342 6

456 8

571-0

685.3

799-4

923-7

IIO27.8

4B

1 16.6

233-3

349-9

466.6

583-r

699.8

8164

933-i

!i°49-7

49

1 19.0

238.1

357-2

476.3

595-3

7.I44

833-4

952.6

1071.6 .

- 50

121.5

243,0

364-5

48.6.0

6.07.5

729.O

850.5

972.0|I093.5,

Table

592- Sir george shuckburgh’s Obfervations

Table of heights taken by the barometer, See.

4- or — the

Above the

Lake of Geneva.

Mediterranean.

Feet.

Feet.

The Lake of Geneva, from iB obfervations, —

0

1230 CgJ

Greateft depth of the Lake, — —

— 393

Clufe, at the Croix Blanche, firft-floor, (b) 2,

+ 351

1581

Chamouny, ground-floor of the inn near the foot of j
Mont Blanc, 4 — — — i

+ 2137

3367

The Montanvert, at the Chateau, 1 —

+ 5001

6231

The fource of the river Arveron, at the bottom of the!
Vallee de Glace, 1 — — — I

+ 2426

3656

Salenche, at the inn, fecond-floor, 1 —

+ 664

1941

La Bonne-Ville, a la Ville de Geneve, fecond-floor, 1

+ 245

1475

Chatlaino, country houfe near Geneva, ground-floor, g

+ 178

The ball on the higheft, or fouth-weft, tower of St. 1
Peter’s church in Geneva, c — — J

+ 249

St. Joire, in a fleld at the foot of the Mole, g — -

+ 671

1901

Summit of the Mole, — — — —

+ 4883

6113

Pitton, higheft point of Mont Saleve, g —

3284

45i4

The Dole, higheft fummit of Mont Jura, G —

+ 4293

5523

The Buet, g — « — — — —

+ 8894

IOI24

Aiguille d’Argentiere, g — — —

+ I2I72

13402

Mont Blanc, g — — —

+ 14432

15662

Frangy, at the inn, firft- floor, below the Lake,

— 166

Aix, a la Ville de Geneve, firft floor, below the Lake,

— 378

Chambery, au St. Jean Baptifte, firft-floor, below the Lake, — 352

Aiguebelle, at the inn, firft-floor, below the Lake,

190

LaChambre, at the inn, firft-floor, above the Lake,

+ 337

St. Michael, at the inn, firft-floor, —

+ 11 13

2343

Modane, at the inn, firft-floor, — - —

-f 2220

3450

(g) More corre&ly 1228 feet, but I have taken

it at 1230

in round

numbers.

(h) The figures at the end of fome of the names fhew the number of obfer-
vations that were madej and the letter G indicates fuch obfervations to have
been geometrical.

Table

in order to afcertain the height of Mountains . 593

Table of heights, &c. continued.

4~ or — the
Lake of Geneva.

Feer.

Lannebourg, the foot of Mont Cenis, at the inn, firfl-floor, 4- 3 1 7 ^

Mont Cenis, at the Poll , — — —

■ — • at the Grande Croix, — *—

Novalefe, the foot of Mont Cenis on the fide of Italy,!

at the inn, firfl-floor, — — J

Boucholin, on the firfl- floor, —

St. Ambroife, on the firfl-floor, below the Lake,

Turin, a l’Hotel d’Angleterre, fecond-floor, 4
Feliffano, near Alexandria, firfl-floor, 1 —

Piacenza, St. Marco, firfl-floor, 1 — —

Parma, au Paon, firfl-floor, 3 — *

Bologna, au Pelerin, firfl-floor, 3 - —

Loiano, a little village on the Appenines, between \
Bologna and Florence, — — J

The mountain Raticofa, the highell point of the Ap-

+ 5°3 1
+ 4793

+ 1511

213
— 40

— 289

— 671

— 967

— 923

— 831

he mountain Katicoia, the higheit point ot tne
penines the road pafies over, miles beyond File- r -f
caije in going to Covigliaje, — • — ■ ^

Florence, nel Corfo dei Tintori, 50 feet above the\
Arno, which was 1 8 feet below the wall of the quay, 3 J

Pifa, aux Trois Demoifelles, fecond-floor, 4 —

Leghorn, chez Muflon, fecond-floor, 2 — r

Siena, aux Trois Rois, fecond-floor, 2 —

Redicoffani, at the Poll, firfl-floor, above the Lake,

the

top of the tower of the old fortifica- 1
tion on the fummit of the rock, — J

Viterbo, aux Trois Rois, firfl-floor, on the Ciminus 1
of the Ancients, — - — — J

Rome, nel Corfo, 61 feet above the Tyber, 7

— 99°

— 1228

— *244

— 164
4- 1240

1830

+ 29

— 1084

A.bove the
Mediterranean.

Feet.

4408

6261

6023

2741

941

263

307

399

2391

1671 29O1

4-240

+54!
+ 38
1066
2470
3060

*259

94

(1) The rocks on each fide the plain, where the pofl-houfe flancls, are at leaf!
3000 feet higher than this fituation; and* it is from the fnow on the tops, and
through the crevices, that the lake on this plain is formed, which gives rife to
the Dora, and may be called one of the fources of the Po.

Vol. LXVIL 4. H

Table

594 <SVr george shuckburgh’s Obfervations

Table of heights, 8cc. continued.

Above the
River Tyber.

Feet.

The Level of the river Tyber, — — .

The top of the Janiculum, near the Villa Spada, — 260

AventineHill, near the Priory of Malta, — 117

In the Forum, near the arch of severus, where thel

ground is raifed 23! feet, — — j 34

Palatine Hill, on the floor of the Imperial palace — - 133

Celian Hill, near the claudia n aqueduff, — 125

Bottom of the canal of the claudian aquedufl, — 175

Efquiline Hill, on the floor of St. M. Major’s church, 154

Capitol Hill, on the Weft- end of the Tarpeian rock, 118

In the S trad a deiSpecchi, in the convent of St. Clare, 27

On the union of the Viminal and Quirinal Hills, in the 1
Carthuflan’s church, diocles. Baths, — J I^1

Pincian Hill, in the garden of the Villa Medici, — 165-

Top of the crofsof St. Peter’s church, — 502

The bafe of the obelifk, in the center of the Periftyle, 31

The fummit of the mountain Sora&e, lying about 20§ 1
geog. miles N. of Rome, g — — J

The fummit of Monte Velino, one of the Appenines, \
covered with fnow in June, about 46 geog. miles f
N.W. of Rome, and which is probably the higheft f
of the Appenines, g — — — J

Above the
Mediterranean!

Feet.

33

*4 or — the
Lake of Geneve*

Naples, Cafa Ifolata on the Chiaia, 27 § feet above!
the fea,, 5 — — — J

Mount Vefuvius, mouth of the Crater from whence 1
the Are iffyed in 1776, — — 1

11 97

2271

ssa7

3938 w

Table

(k) Sir william Hamilton informed me, that the height of Vefuvius, as-
taken by Mr. de saussure of Geneva in 1772, with only a barometer of Mr.
j>E luc’s conft'rudtion, and according to his rules, was 3659 J French feet z:
3900 Engliih, which agrees pretty well with mine. But the Padre della
iroRRE pretends to have found the height of Vefuvius in 1752 (fee p. 44. of

his-

in order to af certain the height of Mountains . 595

Table of heignts, See. continued.

4- or *— the Above the
Lake of Geneva. Mediterranean*

Mount Vefuvius, at the bafe of the cone, — ■ — 2021

Top of the mountain Somma, — — 373^

The fummit of Mount /Etna, — — 10954^7

The following heights are determined from correfponding obfervations by
Mr. messier at Paris, whofe barometer is fuppofed 108 feet above
the fea.

Barberino di V aldenfa, between Boggebonri and Tavernelle,

Modena, a l’Albergo nuovo, — —

Montmelian, at 20 feet above the river, — * — 9

Monte Vifo, by an obfervation from Jurin, by means ]
accurate, g — — — i

Monte Rofa, as meafured geometrically by the Father ^
beccari a, being the fecond mountain of all the f

Alps, — ~ — J

Pont Beauvoifin, — —

La tour du Pin, 4 — — —

Verpilliere, — " *— • —

974

2*4
81 1

9997

15084

7°i
938
56 6

his Hiftory of this Mountain) “ 1677 French feet only, the difference of his
barometer at the top and at the level of the fea being no more than 23 \ French
lines zz 2.065 Englifh inches, which was certainly a miftake of little lefs
than 2000 feet in the refult. The Abbe nollet in 1749 found the fall of the
quicklilver 40 lines : zz 3.55 inches Englifh; and, if this obfervation is to be
depended upon, the fummit of this volcano has rifen within thefe 27 years
more than 330 feet perpendicular.

(I) I have ventured to compute the height of this celebrated mountain from
my own tables, though from an obfervation of Mr. de saussure’s in 1773,
which that gentleman obligingly communicated to me. It will ferve to fhew,
that this volcano is by no means the higheft mountain of the old world ; and
that Vefuvius, placed upon Mount ./Etna, would not be equal to the height of
Mont Blanc, which latter I take to be the moil elevated point in Europe, Alia,
or Africa.

The circumference of the vifible horizon on the top of Mount /Etna, allowance
being made for refraCliun, which I cflimate at 6', is 1093 Englifh miles.

4 H 2 Table

59^ Sir george shuckburgh’s Obfervations
Table of heights, See. continued.

-for — the
Lake of Geneva,

Lyons, at the Hotel Blanc, 50 feet above the Saone,

St. Jean le vieux, — — — . »

Cerdon, near the poft-houfe at the foot of the rocks,
Nantua, 10 feet above the Lake, — . —

Chatillon, at the Logis Neuf, — — .

Colonges, —

St. Genis, apparently on a level with the foot of Mont Jura,
Geneva, at 100 feet above the Lake, 5 —

Macon, at the Parc, 24 feet above the Saone —
Dijon, a la Cloche, the firft- floor, — —

Mountain of Maraifelois C»), 4! miles beyond Viteaux 1
towards Dijon, — J

Lucy-le-bois, — —

Auxerre, 50 feet above the river, — — .

Sens, at the Pod, — — —

Fontainbleau, at the Grand Cerf, fecond-floor, —

Above the
Mediterranean

449

695

854

*4*3
1629
1626
1501
I 268 (

5X4

710

1677

645

283

163

242

(m) From this comparifon with Mr. Messier’s obfervations at Paris, which
makes the Lake of Geneva only 1168 feet above the level of the fea (whereas
from 18 obfervations in Italy, near the fhore of the Mediterranean, it appears
to be 1228, viz* -f 60 feet different) I am inclined to believe, that Mr. Mes-
sier’s place of obfervation is about 50 feet higher than I have fuppofed it, viz*
160 feet above the fea indead of 108, as deduced from three obfervations only at
Boulogne, Calais, and at Dover. If this be allowed,, the fame number of feet
mull be added alfo to all the other heights that are determined by comparifon
with Mr. Messier’s obfervations. I am,, however, by no means fure of this,
but leave it to future obfervers.

(n) On one fide of this mountain is a little dream called Aman^on, that
joins the Yonne and the Seine, and thusgoe^to the Atlantic; while on the
other lide is found the Ouche, which, uniting with the Saone and the Rhone,
Tuns to the Mediterranean; this part of Burgundy then feems to be one of
the higheft, in France.

Table

in order to af certain the height of Mountains . 597

Table of heights, Sec. continued.

-|- or — the
Seine at Paris.

Above the
Mediterraneans

t is, quand les* j
fur FechelU du ?

3&i

Paris, mean height of the Seine, that is, quand les-
eaux fe trouvent a 13 pieds 9 pouces
Pont Royal felon M. de la lande,

Place of my own obfervatibns in the Rue Jacob, fecond- "1
floor, — — - — J

Mr. Messier’s obfervatory, at the Hotel de Clugny, 1
flrfl floor, — * — — J

Mr. de la l and e’s ditto, at the College Royal, flrfl- floor.

Place of Monf. le Pere cottes’s obfervations at Mont- 1
morency, io miles North of Paris, ■ — > J

Stone -gallery of the Church on Mont Valerien,

Depth of the cave of the Royal Obfervatory at Paris"!

below the pavement, — — J

The fame, according to Mr. de la lande, by a£hial\
meafurement, — — — /

Height of the north tower of the church of Notre 1
Dame above the floor, — — J

— by a£tual meafurement, — —

Chantilly, — — —

Clermont, • — — - — - — ■

Amiens, RuedeNoyon, flrfl-floor, —

Abbeville, flrfl-floor, — - — -

Below the mean
height of the Seine

Boulogne, mean level of the fea, from one obferv. only,

Calais, ditto, from one obfervation, — —

Dover, ditto, from three obfervations made two years!

preceding thofe at Calais and Boulogne, — J
Mean height of the river (°) Thames at London above 'j
the mean height of the river Seine from five direct
comparifons with Mr. messier, —

And confequently the Thames at London above the fea,

Warwick, mean level of the river Avon, —

Shuckburgh-houfe, in Warwickfhire, —

(o) By the mean height of the river Thames is underflood when the wat ei

is feet below tke pavement in the left-hand arcade at Buckingham-ftairs*.

+ 57

72

IOI

333

473

98!

98

220|

2l8|

JI9

329

147

79

—33-9

-38.8

—36.6

*

+ 6.8

43

*55

—

560

[ 598 ]

XXX. An Account of the Bramin’s Obfervatory at Benares.
By Sir Robert Barker, Knt. F. R, S. ; in a Letter to
Sir John Pringle, Bart. P. R. S.

SIR,

Read May 29» T3 E N A RES in the Eaft Indies, one of the
*777- JTj

principal feminaries of the Bramms or
priefts of the original Gentoos of Hindoftan, continues
ftill to be the place of refort of that fe<5t of people;
and there are many publick charities, hofpitals, and
pagodas, where fome thoufands of them now refide.
Having frequently heard that the ancient Bramins had a
knowledge of aftronomy, and being confirmed in this by
their information of an approaching eclipfe both of the
Sun and Moon, I made inquiry, when at that place in
the year 1772, among the principal Bramins, to endea-
vour to get fome information relative to the manner in
which they were acquainted of an approaching eclipfe.
The moft intelligent that I could meet with, however,
gave me but little fatisfaftion. I was told, that thefe
matters were confined to a few, who were in poffeflion
of certain books and records ; fome containing the myf-

teries

• Tab:.l'/.

tenes

Sir Robert barker’s Account , &c. 599

teries of their religion, and others the tables of altro-
nomical obfervations, written in the Skanlk-irrit lan-
guage, which few underftood but themfelves : that they
would take me to a place which had been conftru£ted for
the purpofe of making fuch obfervations as I was in-
quiring after, and from whence they fuppofed the
learned Bramins made theirs. I was then conducted to an
ancient building of Hone, the lower part of which, in its
prefent lituation, was converted into a liable for horfes,
and a receptacle for lumber; but, by the number of
court-yards and apartments, it appeared that it mull once
have been an edifice for the ufe of fome public body of
people. We entered this building, and went up a Hair-
cafe to the top of a part of it, near to the river Ganges,
that led to a large terrace, ‘where, to my furprize and
fatisfadlion, I faw a number of inllruments yet remain-
ing, in the greatell prefervation, llupendoully large, im-
moveable from the fpot, and built of Hone, fome of them
being upwards of twenty feet in height; and, although
they ar.e faid to have been erected two hundred years
ago, the graduations and divifions on the feveral arcs ap-
peared as well cut, and as accurately divided, as if they
had been the performance of a modern artill. The exe-
cution in the conftruftion of thefe inllruments exhibited
a mathematical exaftnefs in the fixing, bearing, and

fitting

£00 sir ROBERT barker’s Account of

fitting of the feveral parts, in the neceffary and fufficient
fupports to the very large ftones that compofed them,
and in the joining and fattening each into the other by
means of lead and iron.

The fituation of the two large quadrants of the m-
ftrument marked a in the fir ft plate, whofe radius is
nine feet two inches, by their being at right angles with
a gnomon at twenty-five degrees elevation, are thrown
into fuch an oblique fituation as to render them the moft
difficult, not only to conftru<5t of fuch a magnitude, but to
fecure in their pofition for fo long a period, and affords a
ftriking inftance of the ability of the architect in then
conftruftion; for, by the fhadow of the gnomon thrown
on the quadrants, they do not appear to have altered in
the leaft from their original pofition; and fo true is the
line of the gnomon, that, by applying the eye to a fmall
iron ring of an inch diameter at one end, the fight is
carried through three others of the fame dimenfion to
the extremity at the other end, diftant thirty-eight feet
eight inches, without obftrutfion; fuch is the firmnefs
and art with which this inftrument has been executed.
This performance is the more wonderful and extraor-
dinary when compared with the works of the artificers of

Hindoftan at this day, who are not under the immediate

direction

the Bramin’s Obfervatory at Benares. 601
direction of an European mechanic ; but arts appear to
have declined equally with fcience in the Eaft.

Lieutenant-colonel Archibald Campbell, at that
time chief engineer in the Eaft India Company’s fervice
at Bengal, a gentleman whofe abilities do honour to his
profeflion, made a perfpedtive drawing of the whole of
the apparatus that could be brought within his eye at
one view ; but I lament he could not reprefent fome very
large quadrants, whofe radii were about twenty feet,
they being on the fide from whence he took his
drawing. Their defcription however is, that they
are exadt quarters of circles of different radii, the
largeft of which I judged to be twenty feet, conftructed
very exadtly on the fides of ftone walls built perpendi-
cular, and fituated, I fuppofe, in the meridian of the
place: a brafs pin is fixed at the center or angle of
the quadrant, from whence, the Bramin informed me,
they ftretched a wire to the circumference when an ob-
fervation was to be made; from which it occurred to
me, the obferver muft have moved his eye up or down
the circumference, by means of a ladder or fome fuch
contrivance, to raife and lower himfelf, until he had dif-
covered the altitude of any of the heavenly bodies in
their paffage over the meridian, fo exprefled on the arcs of
thefe quadrants : thefe arcs were very exadtly divided into

Vol. LXVII. 4 I

nine

6o % Sir Robert barker’s Account of

nine Targe fedtions; each of which again into ten, making
ninety lefler divifions or degrees; and thofe alfo into
twenty, exprefling three minutes each, of about two-
tenths of an inch afunder; fo that it is probable, they
had fome method of dividing even thefe into more mi-
nute divifions at the time of obfervation.

My time would only permit me to take down the par-
ticular dimenfions of the moft capital inftrument, or the
greater equinoctial Sun-dial, reprefented by figure a,
plate 12. which appears to be an inftrument to exprefs
folar time by the fhadow of a gnomon upon two qua-
drants, one fituated to the eaft, and the other to the weft
of it; and indeed the chief part of their inftruments at this
place appear to be conftrudted for the fame purpofe, ex-
cept the quadrants, and a brais inftrument that will be
defcribed hereafter.

Figure b is another inftrument for the purpofe of de-
termining the exact hour of the day by the fhadow of a
gnomon, which ftands perpendicular to and in the cen-
ter of a flat circular ftone, fupported in an oblique fitua-
tion by means of four upright ftones and a crofs-piece;
fo that the fhadow of the gnomon, which is a perpendi-
cular iron rod, is thrown upon the divifions of the circle
defcribed on the face of the flat, circular ftone.

5 Figure

the Bramin’s Obfervatory at Benares. 603,
^Wigure c is a brafs circle, about two feet diameter,
moving vertically upon two pivots between two ftone
pillars, having an index or hand turning round horizon-
tally on the center of this circle, which is divided into
360 parts; but there are no counter divifions on the
index to fub-divide thofe on the circle. This inftrument
appears to be made for taking the angle of a ftar at fet-
ting or rifing, or for taking the azimuth or amplitude of
the Sun at riling or fetting.

The ufe of the inftrument, figure D, I was at a lofs to
account for. It confifts of two circular Walls ; the outer
of which is about forty feet diameter, and eight feet
high; the wall within about half that height, and ap-
pears intended for a place to ftand on to obferve the divi-
fions on the upper circle of the outer wall, rather than
for any other purpofe ; and yet both circles are divided
into 360 degrees, each degree being fob-divided into
twenty lefler divifions, the fame as the quadrants. There
is a door-way to pafs into the inner circle, and a pillar in
the center, of the fame height with the lower circle,
having a hole in it, being the center of both circles, and
feems to be a focket for an iron rod to be placed perpen-
dicular into it. The divifions on thefe, as well as all the
other inftruments, will bear a nice examination with a
pair of compafles.

4 I a

Figure

6c>4 Sir Robert barker’s Account of

Figure e is a fmaller equinoctial Sun-dial, conftrudt‘£
upon the fame principle as the large one a.

I cannot quit this fubjedt without obferving, that the
Bramins, without the affiftance of optical glaffes, had
neverthelefs an advantage unexperienced by the ob-
fervers of the more Northern climates. The ferenity
and clearnefs of the atmofphere in the night-time in the
Eaft Indies, except at the feafons of changing the mon-
foons or periodical winds, is difficult to exprefs to thofe
who have not feen it, becaufe we have nothing in com-
parifon to form our ideas upon : it is clear to perfection, a
total quietude fublifts,fcarcely a cloud to be feen ; and the
light of the heavens, by the numerous appearance of
the ftars, affords a profpedt both of wonder and con-
templation.

This obfervatory at Benares is faid to have been built
by the order of the emperor ackbar; for as this wife
prince endeavoured to improve the. arts, fo he wiffied alfo
to recover the fciences of Hindoftan, and therefore di-
rected that three fuch places ffiould be eredted; one at
Delhi, another at Agra, and the third at Benares.,

Some doubts have arifen with regard to the certainty
of the ancient Bramins having a knowledge in aftro-
nomy, and whether the Perfians might not have intro-
duced it into Hindoftan when conquered by that people ;

but

tie Bfamin’s Obfervatory at Benares. 605
but thefe doubts I think muft vanifli, when we know
that the prefent Bramins pronounce, from the records
and tables which have been handed down to them by
their forefathers, the approach of the eclipfes of the Sun
and Moon, and regularly as they advance give timely in-
formation to the emperor and the princes in whofe do-
minion they refide. There are yet fome remains in evi-
dence of their being at one time in polleffion of this
fcience. The ligns of the zodiac, in fome of their
Choultrys on the coaft of Coromandel, as remarked by
john call, efq. f. r. s. in his letter to the Aftronomer
Royal, requires little other confirmation. Mr, call fays,
that as he was laying on his back, refting himfelf in the
heat of the day, in a Choultry at Verdapetah in the Ma-
dura country, near Cape Commorin, he difcovered the
ligns of the zodiac on the cieling of the Choultry : that
he found one, equally compleat, which was on the ciel-
ing of a temple, in the middle of a Tank before the pa-
goda Teppecolum near Mindurah; and that he had often
met with feveral parts in detached pieces. See Philof,
Tranf. 1 7 7 2, p. 3 53. Thefe buildings and temples were
the places of relidence and worlhip of the original Bramins,
and bear the marks of great antiquity,, having perhaps
been built before the Perfian conqueft. Befides, when
we know that the manners and cuftoms of the Gentoo

religion

606 Sir Robert barker’s Account of
religion are fuch as to preclude them from admitting
the fmalleft innovation in their inftitutions ; when we
alfo know that their fafhion in drefs, and the mode of
their living, have not received the leaft variation from
the earlieft account we have of them ; it cannot be fup-
pofed they would engrave the fymbolical figures of the
Perfian aftronomy in their facred temples ; the figns of
the zodiac muft therefore have originated with them, if
we credit their tradition of the purity of their religion
and cuftoms.

Mr. fraser, in his Hiftory of the Mogul Emperors,
fpeaking of time fays, u the Lunar year they reckon
“ 354 days, 22 gurris, i pull; the Solar year they
“ reckon 365 days, 15 gurris, 30 pulls, 2 2\ peels; 60
“ peels making 1 pull, 60 pulls 1 gurri, and 60 gurris
“ 1 day. This is according to the Bramins or Indian
il priefts, and what the Moguls and other Mahomme-
“ dans in India chiefly go by.”

Thus far Mr. fraser; and it ferves to ftrengthen the
argument for fuppofing that the Bramins had a know-
ledge of aftronomy before the introduction of Maho-
metanifm into Hindoftan.

Dimenfions

the Bramin’s Obfervatory at Benares. 607

Dimenlions of the larger equinoctial Sun-dial, plates

1 3. and 14.

Feet. In.

Length of the gnomon at the bafe bb, 34 8

Oblique length of the gnomon cc, — 3 8 8

Radius of the quadrants a a, — — 9 2

Height of the gnomon at d, ■ — > — 22 3

Breadth of the quadrants — — 5 10

Thicknefs ggy — — — 1 o

Breadth of the gnomon hh, — — • 4 6

Whole extent of the inftrument //, — — 37 4

Latitude of the place taken by double altitude 250 1 o'.

lam, Sec.

£ 608 ]

XXXI. A Jhort Account of Dr. Maty’s Illnefs , and of the
appearances in the dead Body , which was examined on
the $d of July, 1776, the Day after his Deceafe. By
Dr. Hunter and Mr. Henry Watfon, FF. R. S.

Read May I, A BOUT two weeks before he died, he

was taken with a fit of violent oppref-
five pain, juft above the pit of the ftomach, which made
him feel as if he was very near dying. He was bled,
and gradually recovered; yet fo imperfedtly, that any
motion of his body, or any preflure upon that part with
the point of a finger, inftantly brought on fuch oppref-
five pain, that he was convinced the leaft addition to what
he had feveral times felt, muft have put an end to his
life. He had an idea that there might be a collection of
matter behind the fternum, which might be difcharged
by fome chirurgical operation.

Upon examining the part, which with the whole
body was very much emaciated, there was no protrufion
or difcolouration. All thoughts of making any perfora-
tion were laid afide ; and it was thought probable, that
there was fome inflammation or adhefion of the pericar-
dium

J‘/u/0t\Jr(ws. Vol.Uloai7ab.^ai.J)^o8.

Philos.Thnris.VoLzxvii.Ta6. TCJII. jr.Tetf-

*

Dr. hunter and Mr. Watson's Account , See. 609
dium, or of the heart itfelf, at its anterior part, juft above
the diaphragm. His cough was almoft inceflant in the
night fince he had left off the ufe of opium, to which he
had been long accuftomed. For feven or eight years, he
faid, he believed he might have had twenty purging
ftools in every twenty-four hours, from a complaint in
his bowels, the principal feat of which he pointed out lb
exactly in his emaciated ftate, that it was obferved at the
time it muft be in the colon, where it pafles down on the
outfide of the lower end of the left kidney. It was there-
fore thought probable that there was contraction with
internal ulceration of the gut at that place : and about
three years ago, with this complaint, which always con*
tinued in his bowels and left fide, he had a fiftula in ano,
for which he was cut, and thereby cured of that diforder ;
but from that time, he was always fenfible that the
lower part of the reCtum remained in an awkward, un«
eafy ftate, fo that it was difficult and painful to pafs a
common glifter-pipe into it.

His medical friends were of opinion, that no more
could be done for him than to palliate, and to procure
eafe and ileep. He returned to his opium, of which he
took one grain twice a day; and at times was thereby
much relieved and comforted.

Vol. LXVII. 4 K

The

6i o Dr. hunter and Mr. watson’s Account

The heart and lungs were examined with great care*
but there was hardly any appearance of diforder in either,
contrary to what was expected.

The conjecture that had been formed about the com-
plaint in the bowels proved to be perfectly juft. The
fmall inteftines were apparently pretty found ; the caecum
and beginning of the colon were much diftended with
air, but not inflamed. The arch, or tranfveife turn of
the colon, was likewife much diftended, and its blood-
veflels were fo loaded, that there was, at firft light, the
outward appearance of an internal inflammation. The
enlarged part of the colon terminated at the lower end of
the left kidney, where there was an annular ftriCture on
the outfide of the gut, and there the gut felt hard and
flefhy. The enlarged part being flit up, was much in-
flamed and fuperficially ulcerated on the inlide, and
more in proportion towards the low'er end. At the ftric-
ture there was but a very linall paflage left, winding ir-
regularly through an inch and an half of hard ulcerated
gut. Below this, where the colon pafies over the pfoas
and iliac veflels, it was in its natural ftate ; but the reCtum
had been at fome former time very much difeafed, and
for a finger’s length to within two inches- of the anus
was contracted to almoft a goofe-quill fize, and of a livid
colour ». The lower, two -inches were not- fo much con-
tracted,.

of Dr. maty’s lajl Illnefs , See. 6 1 1

trailed, but of the fame livid colour, and the furface of
the gut there was almoft as unequal as the fafciculated
furfaces in the heart ; the effeit, probably, of univerfal
ulceration there, which had been a part of, or a compa-
nion to, the fiftula, of which he had been cured by the
operation; for, on that part, the villous coat of the in-
teiiine was deftroyed.

TO this account, more particularly of the two laft
weeks of Dr. maty’s illnefs, and of the appearances upon
opening the body, as drawn up by Dr. hunter, I lhall
beg leave to add the few following remarks.

The heart and lungs were indeed neither of them
eflentially difeafed ; yet there was a whitilh fpot, about
the breadth of a fix-pence, upon the right ventricle of
the heart, near its apex ; a rough border on the left fide
of the diaphragm, as if the lungs had been glued to that
part and torn off again; a partial adhefion of the lungs
to the pleura; and a little purulent fluid within the peri-
cardium. Certainly thefe were fome figns of a flight in-
flammation having attacked the membranes inverting
the contents of the thorax. Neither can we fuppofe fuch
appearances to have exifted without occafioning fome
uneafinefs : they were, perhaps, fufficient to account for

4 K 2, that

6 1 a Dr. hunter and Mr. watson’s Account
that great tendernefs and opprefiive pain which the
doctor felt from the leaft preflure on the fternum, or
upon any part of the breaft near it.

The principal feat of the difeafe which proved fo te-
dious, and in the end fo fatal, was, no doubt, confined to
the colon only % and it was entirely within the gut. The
part firft affe£ted muft have been that portion of the
canal in which we obferved the moft mifchief. The fu-
perficial extent of the difeafe over fo large a furface as
the whole arch of the colon, and the more formidable
appearance of it, in only a few inches of the fame gut,
diftinguiihed the part where the difeafe firft began, and
where it muft have had its longeft duration.

The caufe of all this mifchief was conje<£tural with.
Dr. maty himfelf. Had it arifen, as he fufpefted, from
having bruifed his fide with the hilt of his fword, we
then fhould have found the gut injured from without
inwards. But is it not moft likely,, that a little bit of
bone, the ftone of fruit, fome fharp or hard body, in
palling, had injured the gut fo much, as to lay a founda-
tion for all the growing corhplaints ? Nearly the fame
appearances have been obferved in the oefophagus from
only a hard cruft of bread lodging for a time in the paf-
fege i which, after being forced down,, was fucceeded by
gyeat forenefs,, inflammation, ulceration,, and at length

e fo

of Dr. maty’s lajl Illnefsy 8cc. 613

fo complete an obftrudtion, as to occafion the death of the
patient ; of which I once faw a very deplorable inftance.

The ulcerated inteftine is a difeafe generally, as in the
cafe before us, flow in its progrefs, but certainly fatal.
An accumulation of acrid matter, confined air, folid in-
gefta, in ftiort any thing capable of ftretching, irritating,
or hardening the gut, will fpread and increafe the difeafe.

The fafciculated appearance in the re£tum is what I
have once met with in a very found gut, where the vil-
lous coat was not in the leafl injured; it is therefore
fometimes an original conformation, but apparently un-
neceflary, as the gut, we may prefume, would perform
its office much more agreeably without it.

H. WATSON*

c 614 ]

XXXII. An Account of fome Experiments made ’with an
Air-pump on Mr. Smeaton’s Principle ; together with
fome Experiments with a common Air-pump. By Mr.
Edward Nairne, F. R. S.

V

Stead June 12, a g the following experiments were made
principally to try the performance of
Mr. smeaton’s pear-gage, it may be proper to defcribe
it, which I fhall do in his own words, taken from the
Phil. Tranf. for the years 1751 and 1752, vol. XL VII.

jp* ij. 20*

u I have found,” fays Mr. smeaton, “ the gages that
li have been hitherto made ufe of, for meafuring the
“ expanfion of the air, very unfit to determine in an ex-
“ periment of fo much nicety; I have therefore con-
u trived one of a different fort, ■which meafures the ex-
“ panfion with certainty to much lefs than the 1 oooth
“ part of the whole. It confifts of a bulb of glafs, fome-
■“ thing in the fhape of a pear, and fufficient to hold

“ about

Mr. nairne’s Account , See. 615

tr about half a pound of quickfilver : it is open at one
*( end, and at the other is a tube, hermetically clofed
“ at the top. By the help of a nice pair of fcales I found
ic what proportion of weight a column of quickfilver, of
« a certain length, contained in the tube, bore to that
u which filled the whole veflel : by thefe means I was
u enabled to mark divifions upon the tube anfwering to
u a 1 oooth part of the whole capacity; which being
** about one-tenth of an inch each, may, by eftimation,
“ be eafily fub-divided into fmaller parts. This gage,
“ during the exhaufting of the receiver, is fufpended
“ therein by a flip wire. When the pump is worked as
“ much as fhall be thought neceflary, the gage is pufhed
** down till the open end is immerged in a ciftern of
“ quickfilver placed underneath ; the air being then let
“ in, the quickfilver will be driven into the gage till the
M air remaining in it becomes of the fame denfity with
“ the external, and as the air always takes the higheft
** place, the tube being uppermoft, the expanfion will be
“ determined by the number of divifions occupied, by
u the air at the top;

“ The degree to which I have been able to ratify the
a air in an experiment, has generally been about 1000
**■ times, when the pump- is put clean together; but the
3, s< moifture.

616 Mr. nairne’s Account of

“ moifture that adheres to the infide of the barrel as
“ well as other internal parts, upon letting in the air, is
(( in the fame fucceeding trials worked together with the
t{ oil, which foon renders it fo clammy as to obftruft
“ the actions of the pump upon a fluid fo fubtil as the
<( air when fo much expanded ; but in this cafe it feldom
(< fails to a<5t upon the air in the receiver till it is ex-
<c panded 500 times.” Thus far Mr. smeaton’s ac-
count.

The pump with which the chief of the following ex-
periments were made, had the leather of its pifton foaked
in oil and tallow (and oil in the barrel) and every pre-
caution was taken that no water fhould get into the
working parts of the pump, except what might arife in
vapour from the fubftances which were under the
receiver.

EXPERIMENT 1.

Having provided a pear-gage agreeable to Mr. smea-
ton’s defcription, on which the fpace of a 4000th part
of the whole capacity was two-tenths of an inch; this
gage, together with a glafs cup which ferved as a ciftern

to

fame 'Experiments made with an Air-pump. 617
to hold the quickfilver for it, was put under a receiver;
which receiver was placed on a leather foaked in oil and
tallow, on the plate of the pump.

I muft obferve here, that the foot of the glafs cup,
which held the quickfilver for the pear-gage, being
broken off by an accident, another foot, made of a piece
of box-wood, was cemented to it. The reafon of men-
tioning this circumftance, which may feem trifling, will
appear in the fixth experiment. The pump was then
worked, and the pear-gage was pufhed down till its
open end was immerfed in the quickfilver in the cup :
the air being then let into the receiver, it forced the
quickfilver into the gage till it was filled within a 4000th
part of the whole, fo that by this gage the pump ap-
peared to have expanded the air 4000 times. To what
it might be owing that this pump, which was on Mr.
smeaton’s principle, fhould expand the air 4000 times
inftead of only iooq as Mr. smeaton’s, I could not even
furmife.

Having the pleafure of knowing Mr. smeaton, and
being well acquainted with his great abilities in practice
as well as theory, I could not imagine that this apparent
fuperiority could proceed from our having executed the
various parts of the pump in a more perfect manner than

Vol. LXVII. 4 L he

618 Mr. nairne’s Account of

he had done. I therefore determined, for greater cer-
tainty, to fee if the fault might not be in the gages; and
for that purpofe I repeated the experiment with the
fyphon-gage, and both the long and fhort barometer-
gages, and found that the feveral degrees of exhauftion
indicated by thefe, were very different from that which
the pear-gage had indicated: no conclufion, therefore,,
could be drawn from this experiment.

I determined next to compare again this pear-gage
with the long and fhort barometer-gages with all the ac-
curacy I was matter of: and firft, left the tubes of thefe
barometer-gages might not be perfectly clean and free
from moifture, I had fome tubes made at the glafs houfe ;>
and as foon as they were brought home, which was
within an hour after they were made, two of them, which
were of the fame fize, were filled with diftilled quickfil-
ver; and then the quickfilver was carefully boiled in the
tubes the whole length, which was about thirty-fix inches :
I then cut off about fix inches from the fealed end of one
of the tubes, and took care to keep it perfectly full of the
boiled quickfilver; it was then inverted into a glafs cittern
containing boiled quickfilver; and a piece of very thin
ivory, about half an inch in length, with divifions on its
edge, was- put over the tube, fo as to float on the fur face

of

fame Experiments made with an Air-pump . 619

of the quickfilver in the ciftern, by which means the dif-
ference of the two furfaces could be feen to a great nicety.
This kind of gage is called the fliort barometer-gage.

The other tube, which was cut off to thirty-three
inches, being perfectly full of the boiled quickfilver, was
alfo carefully inverted into a glafs ciftern containing
boiled quickfilver, to fuch a depth that from the furface
of the quickfilver in the ciftern to the top of the tube was
twenty-nine inches; this had likewife a piece of ivory,
with divifions on it, put over the tube, fo as to float on
the furface of the quickfilver in the ciftern, in the fame
manner as the other.

This long tube and the fhort barometer-gage being-
put both of them at the fame time under the receiver,
which was carefully cemented to the plate of the pump ;
the pump was then worked for ten minutes, and the fur-
face of the quickfilver in both the tubes came down very
nearly to within one-twentieth or five hundredth parts of
an inch of the furface of the quickfilver in their refpec-
tive citterns.

The air was then let in, and the receiver being taken
from the pump, the long tube was raifed up fo far in the
ciftern as to let the quickfilver come down from the top
of the tube, fo that it now became a common barometer,

4 1/ 2 and

620 Mr. nairne’s Account of

and its height from the furface of the quickfilver in the
ciftern meafured thirty inches; which agreed exadfly
with an open ciftern-barometer I had in the room. The
quickfilver in the tube of this barometer was alfo boiled,
and the meafure the fame.

The quickfilver was then emptied out of this long
tube, and the fealed end being cut off, it was then ce-
mented to a piece of brafs,by which means it was fcrewed
to the air-pump; and the lower end being immerfed in a
cup of boiled quickfilver, it then made that kind of gage
where the air is taken from the top of the tube, and
which is called the long barometer-gage. This gage
being fixed to the pump, and the fhort barometer-gage
put on the plate of the pump under a receiver, the re-
ceiver was cemented to the plate of the pump, and the
pump worked for ten minutes as before. The quickfil-
ver in the fhort barometer-gage fell now nearly to within
one-twentieth or five hundredth parts of an inch of that
in the ciftern, and the quickfilver in the long gage rofe
nearly to within a twentieth or five hundredth parts of an
inch of the height it was at when it was made as a com-
mon barometer.

Gages made with thefe precautions feem to me to be
the moil to be depended upon, in determining the actual:

diminution.

fotm Experiments made with an Air-pump. 621
diminution of the preflure on the furface of the quick-
filver in the tube of the long gage, and alfo on the fur-
face of the quickiilver in the ciftern of the ihort gage.
But of thefe two gages the long barometer-gage was
chiefly ufed in the following experiments, as being fixed
to the pump: however, having now made thefe two
gages with as much accuracy as I was matter of, and
finding that they agreed pretty nearly, I proceeded to
repeat my firft experiment.

EXPERIMENT II.

I put the fhort barometer-gage, and the pear-gage
with the glafs cup having a wooden foot,, both toge-
ther under the receiver, which receiver was placed on a
leather foaked in oil and tallow on the plate of the
pump ; the pump was then worked for ten minutes, and
the quickiilver was brought down in the ihort barome-
ter-gage to about one-tenth of an inch of the furface of
the quickiilver in the ciftern, and rofe in the long baro-
meter-gage to within one-tenth of an inch of the height
of the quickiilver in my ftandard barometer, which was
at that time at thirty inches; by which it appeared, that

the

622 Mr. nairne’s Account of

the preffure on the furface of the quickfilver in the
ciftern, and in the tube of the long barometer-gage, was
diminifhed to about a three-hundredth part : the pear-
gage being now pufhed down till its open end was im-
merfed under the furface of the quickfilver in the cup,
the air was then let in, and the pump appeared by that
gage to have exhaufted all but a fix thoufandth part of
the air; or, in other words, the degree of exhauftion by
this gage appeared to be fix thoufand times.

Finding (till this difagreement between the pear-gage
and the other gages, I tried a variety of experiments ; but
none of them appeared to me latis factory, till one day in
April 1776, fhewing an experiment with one of thefe
pumps to the honourable henry cavendish, Mr.
smeaton, and feveral other gentlemen of the Royal
Society, when the two gages differed fome thoufand
times from one another, Mr. cavendish accounted for
it in the following manner. “ It appeared,” he faid,
“ from fome experiments of his father’s, Lord charles
“ cavendish, that water, whenever the preffure of the
“ atmofphere on it is diminifhed to a certain degree, is
“ immediately turned into vapour, and is as immediately
“ turned back again into water on reftoring the pref-
“ fure. This degree of preffure is different according to
“ the heat of the water: when the heat is 720 of faii-

“ renheit’s

Jome Experiments made with an Air-pump. 623
“ renheit’s fcale, it turns into vapour as foon as the.
“ preffure is no greater than that of three quarters of an
“ inch of quickfilver, or about one-fortieth of the ufual.
“ preffure of the atmofphere ; but when the heat is only
“ 4.1 °, the preffure mult be reduced to that of a quarter
“ of an inch of quickfilver before the water turns into
“ vapour. It is true, that water expofed to the open air
“ will evaporate at any heat, and with any preffure of
“ the atmofphere;. but that evaporation is intirely owing
“ to the adfion of the air upon it: whereas the evapora-
“ tion here fpoken of is performed without any affiftance
“ from the.air. Hence it follows, that when the receiver
“ is exhaufted to the above-mentioned degree, the moif-
“ ture adhering to the different parts of the machine
“ will turn into vapour and fupply the place of the air,
“ which is continually drawn away by the working of
“ the pump, fo that the. fluid in the pear-gage, as well as
“ that in the receiver, will confift in good meafure of var
“ pour. Now letting the air into the receiver, all the
“ vapour within the pear-gage will be reduced to water,
“ and only the real air will remain uncondenfed; confe-
“ quently the pear-gage flrews only how much real air
“ is left in the receiver, and not how much the preffure
“ or fpring of the included fluid is diminifhed, whereas

«• the

624 Mr. nairne’s Account of

“ the common gages fhew how much the prefllire of
“ the included fluid is diminiflied, and that equally,
“ whether it conlift of air or of vapour.”

Mr. cavendish having explained fo fatisfa£torily the
caufe of the difagreement between the two gages, I con-
fidered, that, if I were to avoid moifture as much as pofft-
ble, the two gages fliould nearly agree: this induced
me to make the following experiment.

EXPERIMENT III.

The plate of the pump being made as clean and as
dry as poflible, there was then put on it the before-
mentioned fliort barometer-gage, alfo the pear-gage
with a ciftern entirely of glafs which held the quick-
lilver; they were then covered with a receiver, round
the outfide of which was laid a cement which per-
fe£fly excluded the outward air; every part, before it
was put under the receiver, as well as the receiver itfelf,
being made as clean and as free from moifture as poili-
ble^. The pump was then worked for ten minutes,

(a) It may be proper here to take notice, that the pump in every experiment
hereafter mentioned was worked ten minutes, and the fame receiver continued
cemented to the pump-plate, except where it is otherwife mentioned. The top
part of this receiver was made to open, in order to put in different things.

3 and

fonu Experiments made with an Air-pump, 625
and the barometer-gages indicated a degree of exhauftion
nearly 600; the air was then let into the receiver, the
pear-gage indicated a degree of exhauftion, but very
little more than 600 alfo. The near agreement of the
pear-gage with the barometer-gages in this laft experi-
ment, in which I had been fo careful to exclude the
moifture as much as poflible, feemed to prove beyond a
doubt, that their difagreeing in the firft and fecond ex-
periments mull have been owing (as Mr. cavendish fup-
pofed) to the moifture which in them had not been fo
carefully excluded. But I began now to fufpedt alfo, that
there might arife a vapour from fome moifture that
might be contained in the leather foaked in oil and tal-
low, or in the wooden foot which was cemented to the
glafs cup, both ufed in the firft and fecond experiments :
thefe fufpicions induced me to try the following experi-
ments,

EXPERIMENT IV.

A piece of leather dreffed in allum, knowh by the
name of white Iheep-fkin, of about four inches diame-
ter, which had been foaked in oil and tallow about a year
ago (fuch as was ufed to place the receiver on in the firft
and fecond experiments') was put into the receiver; the

Vol. LXVII. 4 M pump

626 Mr. nairne’s Account of

pump was then worked, and the barometer-gage indi-
cated a degree of exhauftion of nearly 300 ; but on the
admiffion of the air the pear-gage indicated a degree of
exhauftion of 4000,

EXPERIMENT V.

The piece of leather being taken out, the pump was
then worked, and the degree of exhauftion appeared by
both the barometer and pear-gages to be about 600, as
in the third experiment.

EXPERIMENT VI.

A cylinder made of a piece of box wood (which I had
kept by me for more than a year) one inch in diameter
and three inches in length, was put into the receiver
(this piece of wood was of the fame kind as that which
was cemented to the foot of the glafs cup ufed in the firft
and fecond experiments) the pump was then worked,
and the degree of exhauftion appeared by the barometer-
gage to be 300, but by the pear-gage 16,000.

Thele experiments have often been repeated, but the
refult was leldom the fame. When leather foaked in oil
and tallow has been put into the receiver, the pear-gage
has fometimes indicated a degree of exhauftion of

2O3O00,

fome Experiments made -with an Air-pump. 627
20,000, and fometimes no more than 500; it likewife
differs very much with the box wood, which may per-
haps be owing to different degi'ees of heat and moifture.

From thefe experiments it is evident, that there, arises
an elaftic vapour from the leather dreffed in allum and
foaked in oil and tallow, and alfo from the piece of box
wood, when the weight of the atmofphere has been
partly taken off by the adfion of the pump ; and that this
vapour prefTes upon the furface of the quickfilver in the
tube of the long barometer-gage, and of that in the cif-
tern of the fhort one ; and that, confequently, the tefti-
mony of both thefe gages muft be influenced by this
vapour, as well as by the fmall remainder of common
air : but as it is the nature of the pear-gage not to give
its teftimonv till the remaining air contained in it is
preffed, fo as to become of the fame denfity of the atmo-
fphere; and as this vapour cannot fubfiff in the form of
vapour under that preffure, this gage is not at all in-
fluenced by it, but indicates the remaining quantity of
permanent air only.

Seeing thus what a confiderable quantity of vapour
arofe from the compound of leather, allum, oil, and tal-
low, my next objedt was to find out from which of thofe
fubftances it chiefly arofe ; how far I have fucceeded will
appear by the following experiments.

4 M 2

Sub-

628 Mr . nairne’s Account of

Subftances put Into the receiver.

Weight
when put
into the
receiver.

Degree of exhauf-
tion according to

Barom.

gage.

Pear-

gage-

EXP. VII. Tallow, — —

2 ounces

43 1

600

exp. yin. Oil, - — —

2 ounces

377

480

exp. ix. Allurn, — —

Exp. x. A piece of leather as it came from the \

2 ounces

37&

58°

leather-fellers, — — - — J

exp. xi. The fame piece of leather foaked

1 00 grains

152

100,000-

in the fame two ounces .of tallow and oil i
melted together, — — J

43*

800

From thefe experiments it appears, that the elaitic
vapour which caufed fo great a difference in the tefti-
mony of the gages, arofe principally from the leather,,
and but little from the tallow, oil, or allum : it even ap-
pears by the tenth experiment, that it came from the
leather, and fupplied the place of the exhaufted air lb
faff, that I could not (at leaft in the ten minutes) make
the barometer-gage indicate a degree of exhauftion of
of more than 159.

To determine whether it was the moiffure in the lea-
ther from which the vapour arofe, I made the following
experiments.

Sub-

feme Experiments made with an Air-pump. 629

Subfiances put into die receiver.

Weight
when put
into the
receiver.

Degrees of exhauf-
tion according to

Variation in
weight
during the
experiments.

f

Barom.

gage-

Pear-

gage.

100 grains

i‘34

100,000

left 2 grains.

80 grains

26 8

280

gained 2 grs*

1O0 grains

H7

100,000

loft 2 grains*

exp. xii. A piece of white lea--*
ther, frefh from the leather- >
fellers, — — J

exp. xiii. The fame piece of *1
leather, dried by the fire till
it would lofe no more of its
weight,. - — - —

exp. XiV. The lame piece of
leather held in che fteam of
hot water till it had regained
the 20 grains it had been de-
privedof, • — •- —

In this laft experiment it was full three quarters of an
hour before the leather regained the twenty grains of
weight, although it was held very near the furface of
the hot water.

Whenever I have allerted, that the degree of exhaus-
tion, according to the pear-gage, was fo great as 1 00,000,
I only gueffed it to be thereabouts, for my gage is not
graduated to more than 4000; but, that it may be feen
what reafon I had to fuppofe it at 100,000, I have
brought my pear-gage filled in this laft experiment, for
the infpedlion of the gentlemen prefent.

EXPERIMENT XV..

The fame piece of leather ufed in the eleventh expe-
riment was put into a damp cellar, where it was left till

the

630 Mr. nair.ne's Account of

the next day; it was then. put again into the receiver,
and the degree of exhauftion, according to the barometer-
gage, was 300, and according to the pear-gage 3500.

Being now perfectly fatisfied that the variation in the
teftimony of the pear and barometer-gages was occa-
iioned by the moifture contained in the fubftances I had
put into the receiver afluming the form of vapour; I
determined next to try what would be the effedt of the
vapour which might arife from fmall quantities of dif-
ferent fluids, and from fome other fubftances containing
moifture of various kinds.

Subfiances put into the receiver.

jjxp. xvi. Water in a waich-glafs,
EXP. xVhi. Water in a glais cup, 1
diameter two inches, — J
exp. xviii. Spirit of wine ini
the fame cup, — J

exp. xix. Vitriolic acid, —
exp. xx. A piece of the infidel
of a china orange with fome f
of the rind, • — J

Exp. xxi. A piece of the infidel
of an onion, - — J

exp. xxii. A piece of tainted beef,
exp. xxiii. A piece of frefh beef,
exp. xxiv. Spirit of turpentine,
exp. xxv. Pearl-afh, —

Exp. xxvi. The fame pearl-afh 1
made very hot, — J

-exp. xxvii. A lighted candle S
held in the receiver till it went j
out, - — . — . J

Weight |
when put j
in.

Degree of exhauft-
in^ according to

O O

Change in
weight
during the
experiment.

f

Barom.

gage-

Fear-

gage.

3 grains

148

24,000

loft i| grain.

i oo grains

89

8000

loft 2 grains.

i oo grains

54

6000

loft 9 grains.

ioo grains

340

220

gained 1 gr.

ioo grains

160

100,000

Iolt 2f grs.

ioo grains

160

100,000

loft 1 J grain.

ioo grains

152

100,000

loft 2j grs.

ioo grains

1 36

100,000

loft 2f grs.

ioo grains

o

3°i

1800

loft 2 grains*

2 ounces. ^

1 1 B

5000

198

420

j 297

1800

Sub-

Jome Experiments made with an Air-pump. 631

Subfiances put into the receiver.

Weight
when put

Degrees of exhauft-
ing according to

Change in
weight
during the
experiment,.

•Ul,

r —

Barom.

gage.

Pear-

gage-

exp. xxviii. A piece of charcoal,
exp. xxix. The receiver heatecU
by holding feveral pieces of
lighted charcoal in it, and
then the above piece being }>
thoroughly lighted was put
into the receiver, and the
pump worked^ - — ^

ex p. xxx. Cam phi re, —

exp. xxxi. Sulphur made to burn”]
on a piece of brafs, — J

1 00 grains

129

650

3°4

247

.1

1 Boo
600

520

320

-

| loft barely
1 1 a grain*

Obferving by thefe experiments that the fmall quan-
tity of moifture which exhaled from the fubftances un-
der the receiver prevented the pump from exhaufting it
to any very conliderable degree, I began to fufpedt that
whenever wet leather had been ufed to connect the re-
ceiver with the plate, there mull have rifen fo great a
quantity of vapour as to have prevented the degree of
exhauition from being near fo great as in fome of the
foregoing inftances. Thefe fufpicions induced me to
make the following experiments.

632

Mr. nairne’s Account of

EXP. xxxii. The receiver was taken off, and after the -j
cement was wiped clean from it, and every part made I
perfe&ly dry, it was put again on the pump-plate, J
and a little oil only was poured round the outfide edge, J
Exp. xxxiii. The receiver was taken off again, and in-^
Head of the oil it was fet on a piece of leather, l
which had been foakcd two days in water, — J
exp. xxxiv. The laft experiment repeated with the 1
fame piece of leather, — —

exp. xxxv. The laft experiment repeated again with
the fame piece of leather, — —

exp. xxxvi. The receiver was taken off, and inftead of
the leather foaked in water, there was put on a piece of I
the fame fort of leather, foaked in a mixture of water |
and fpirit of wine, fuch as Mr. smeaton ufed, J
iExp. xxxvii. The laft experiment repeated with the!

fame leather, — — ; — J

exp. xxxviii. The laft experiment repeated again with^
the fame leather, — —

j

Degrees of exhauf-

tion according to

Barom.

£aSe*

Pear-

gage.

nearly 600

full 600

16,000

5l

1500

Sl

IOOO

47

12,000

47

1150

47

500

The great difference in the teftimony of the pear-gage
in thefe fix laft experiments appeared to me exceedingly
aftonifhing, for the leathers feemed each of them to be
as moift at laft as at firft.

By thefe experiments I was convinced how effe&ually
the ufe of leather foaked in water, or in water and fpirit of
wine, prevents the pump from exhaufting to any confi-
derable degree. I have made a number of experiments of
the fame kind as thefe ; but have never been able to ex-
hauft, under fuch circum fiances, to a greater degree than
between 50 and 60, when the heat of the room was
2 about

fome Experiments made with an Air-pump , 63 3

about 570 by a thermometer of Fahrenheit’s fcale : but
the following experiments will fhew how much fome
different degrees of heat affeil the degree of exhauftion.

Height
of the
Therm.

Degrees of exhauf-
tion according to

Barom.

gage.

Pear-

gage.

exp xxxix. Receiver fet on leather, which had 1
lain all night in water, — J

exp. xl. Receiver fet on a leather foaked alU
night in two parts water and one of fpirit of >
wine, — — — ■ J

46

46

84

76

20,000

8000

The pump having been put in a room of the heat of
57° of Fahrenheit’s fcale for feven hours together,
with the leathers put in the fame water and the fame
fpirit of wine and water which they had been foaked in
all night, and which had been ufed in the two laft expe-
riments, the following experiments were made.

Height
of the
Therm.

Degree of exhau£*
tion according to

(

Barom.

Pear-

gage-

gage.

exp. xli. The receiver fet on the leather]
foaked in water, — — J

57

S6

1 6,000

Exp. xui. Receiver placed on a leather foaked ]
in water and fpirit of wine, - — J

1

57

49

1200

The following table will fhew the comparative excel-
lency between the pump on Mr. smeaton’s principle
with which the chief of thefe experiments have been
Vol. LXVII. 4 N tried,

634 Mr. nairne’s Account of

tried, and one of my common double barreled table air-
pumps under the fame eircumftances. The leather on
the piftons of both was foaked in oil and tallow, and the
receiver cemented down to each plate \ the pumps were
both of them fireih oiled.

^xp.xLiiii. A pieceof leather, weigh-
ing ioo grains, as it came from
£he leather- filers, was pu£ into
the receiver of each pump, both
pieces being cut from the fame
fkin clofe by each other,, —
exp. xliv* The fame piecesr of* lea-
ther dried by the tire till they
would lofe no more of their
weight, — —

The following experiments will fliew the effedt of
water ufed in the barrels of pumps to make the piftons
move air tight in them.

I took the fame common air-pump ufed in the laft
experiment, and having taken off the leathers leaked in
oil and tallow from the piftons of this pump, and wiped
the barrels as clean as poffible, I then put new leathers,
which had been foaked in water, and new bladder valves ;
the receiver was then cemented to the pump-plate as
before.

Pump on Mr. smea-
ton’s principle.
Degrees of exhauf-
tion according to

Common pump.

Degrees of exhaus-
tion according to

Barom.

gage.

Pear-

gage-

Barom.

gage.

Pear- ’

gage-

152

100,000

108

22,000

506

520

160

165,

3

EXP.

fame Experiments made with an Air-pu np. 635

r

Degrees of exhauf-
tion according to

f

Barom.

gage-

Pear-

gag9.

exp. xl v. The pump was then worked as ufuai, —
Exp. xlvi. The lail experiment repeated with another n
common pump, the leathers of the piftons of which >
were alfo foaked in water, — • — J

37

34

38

37

From thefe experiments it evidently appeals, that the
air-pump of otto guericke, and thofe contrived by
Mr. gratorix, and Dr. hooke, and the improved one
by Mr. pappin, both ufed by Mr. boyle, alfo hauks-
BEe’s, s’gravesande’s, muchenbrook’s, and thofe of all
who have ufed water in the barrels of their pumps, could
never have exhaufted to more than between 40 and 50,
if the heat of the place was about 5 7 ; and although
Mr. smeaton, with his pump, where no water was in
the barrel, but where leather fcaked in a mixture of water
and fpirit of wine was ufed to fet the receiver on the
pump-plate, may have exhaufted all but a thoufandth or
even a ten thoufandth part of the common air, according
to the teftimony of his pear-gage; yet io much vapour
muft have arifen from the wet leather, that the contents
of the receiver could never be lefs than a feventieth or
eightieth part of the denfity of the atmofphere : never-
thelefs, it does not feem that any deficiency in the con-
ftru&ion of Mr. smeaton’s pump was the caufe of his

4 N 2 not

636 Mr. nairne’s Account of

not being able to exhauft beyond the low degrees of 7 o
or 80. Had he been aware of the bad effects of fetting
the receiver upon leather foaked in water and fpirit of
wine ; and had he made ufe of the precaution to free all
parts of his pump as much as poffible from moifture, I
make not the leaft doubt but the air-pump, which he
executed himfelf, would have exhaufted to as great a
degree, as that pump has been feen to have done with
which the chief of thefe experiments were made.

Having read the principal part of this paper to Mr.
smeaton, and fliewn him fome of the experiments;
one in particular, where the pear-gage, as he obferved
himfelf, was filled to no left than 100,000th part of the
whole content; he remarked from memory, that he had
in feveral trials exceeded 1000 times, and once, as he
remembered, near or about 10,000 times; but as he
never could account how this happened, which appeared
to him perfectly accidental, and therefore could not de-
pend upon doing it at pleafure, he contented himfelf with
putting down 1000 times, as being wffiat (under the cir-
cumftances mentioned in his papers) he had a tolerable
certainty of.

I mull here again obferve, that if we only wilh
to knoW the quantity of permanent air remaining
in the receiver after it is as much exhaufted as poffi-
ble,

fame Experiments made with an Air-pump. 6 37
ble, it feems, that it is by Mr. smeaton’s gage only
that we can know it. Again, when by the afliftance of
his gage and the barometer-gage together, we have dif-
eovered that there is a vapour which arifes and occupies
the place of the permanent air which is exhaufted, it
feems that it is by the means of his gage only that we
can difeover what part of the remaining contents of the
receiver conlifts of this vapour, and what part of perma-
nent air..

An account of fome further experiments made with the-
fame air-pump on Mr. sMEATON’r principle, the refults-
of which were different from the former. ~

AFTER I had made the foregoing experiments, and
thought to have done with the fubjedt (for feme time at
leaft) in reviewing them for the laft time, I perceived one
or two, the extraordinary refults of which (though not
unnoticed by me before) I now thought I had, not paid
fufficient attention to. Experiment the 19th (in which
I found that when vitriolic acid was put into the receiver,
and the pump worked for the ufual time, the pear-
gage indicated a much lefs degree of exhauilion than the

barometer--

0. 5 ? Mr. nairne’s Account of

barometer-gage) feemed to me now fo furprizing, that it
was impoffible not to wilh to repeat this experiment with
all the care poffible, and to endeavour to recoiled! all the
circumftances which I thought could any way influence

the refult.

The vitriolic acid I made ufe of in the following ex-
periments was fome that I had had by me for fome time;
it had been kept in a phial, flopped with a glafs-ftopper,
and tied over with a bladder. The thermometer in the
room was at 5 9% and the weather remarkably dry.

t ■ - ■ 1

Weight
when put
into the
receiver.

Degrees of exhauf-
tion according to

A_

Variation of
weight
during the
experiment.

Barom.

gage-

Pear-

gage.

ixp. xlvii, Vitriolic acid in al
glafs cup, two inches diameter, J
Exp. xlviii. The laft experi-*}
ment Repeated with the fame >
vitriolic acid in the fame cup, J
Exp. xlix. The former experi- >
meat repeated again with the 1
fame vitriolic acid in the fame j

100 grains

10 1 grains

ioif grs.

602

502

502

380

350

3S°

gained i gr.
gained \ a gr.

cup, — — J

Exp. L. The former experiment^
repeated the fourth time in >
every refpe£l as before, J

ioif grs.

502

340+

/ gained a J
l of a grain.

The generation of vapour in the exhaufted receiver
which Mr. cavendish had fuppofed, and which I
feemed, by my former experiments, to have proved, ap-
peared fatisfadlorily to have accounted for the pear-

gage’s

fome Experiments made with an Air-pump. 639
gage’s indicating a greater degree of exhauftion than the
barometer-gage : but what to fuppofe could poffibly
make it indicate a lefs,! was entirely at a lofs; for after
having made thefe furprizing, experiments on the vitrio-
lic acid,. I wiihed once more to try if I could repeat, with
the lame refult, fome of my former experiments, in
which the pear-gage had indicated fo nearly the fame
degree of exhauftion as the barometer-gages. Accord-
ingly I took away the vitriolic acid from under the re-
ceiver; the pump was then frefh oiled, and I was very
eareful to wipe clean and dry the receiver and pump-
plate, and then cemented down the receiver as ufual.

EXPERIMENT £l.

The pump was then worked, and the degree of ex—
hauftion appeared by the barometer-gage to be 43 2, ; but
by the pear-gage to be but 370.

I know of no circumftance attending this experiment
that differed from thofe in which my former experi-
ments were made when' the gages agreed fo nearly, un-
lefs it were that of the weather : 1 recoiled; that it was*
then very damp,, and now it had been very dry for fome
time. How this circumftance could make fo great an
alteration in the refult of thefe experiments,! cannot pre-
tend

640 Mr. nairne’s Account of

tend to fay; but fome of the following experiments will

fhew that the pear-gage ftill continued in many cafes to

indicate a lefs degree of exhauftion than the barometer-

gage.

In all the preceding experiments the pump was
worked for ten minutes, and the pear-gage was at the
end of that time pufhed down fo as for the mouth to be
immerfed in the ciftern of quickfilver, and the air then
let in according to the manner of uling this gage; but
now that I found that the teftimony of this gage fo fel-
dom agreed with that of the barometer-gage, I wifhed to
try, whether they might not agree when the receiver was
exhaufted only in part, though they did not when it was
exhaufted as much as poflible. For this purpofe I had
the fame receiver fitted with two pear-gages, fo that I
now could immerfe the mouth of one of them in the
ciftern of quickfilver when I had exhaufted the receiver
in part only, and not immerge the mouth of the other
till the receiver was exhaufted for the ufual time of ten
minutes ; in which time I found 1 could always raife the
quickfilver in the barometer-gage as high as if I were to
work the pump much longer.

EXP.

fame 'Experiments -made with an Air-pump. 64c

"Exp. l 11. The receiver cemented ]
to the pump -pi ate, — J

E*x-p. l hi. The receiver unce-%
mented, wiped clean from
the cement;, and put on the -
pump-plate, with a little oil
round the outlide, —

Exp. liv. The receiver .put on a]
leather foaked in oil and tallow, i

Degree's of exhauftion when the pump
had been worked

Five minutes;
according to

Ten’ minutes,;
according; to

O

Barom.

gage-

Pear-

gage*

1 —

Barom,

gage*

! Pear-

gage*

43°

CO

0

0

430

360

502

360

502

360

502

320

323

500

This laft experiment feemed very extraordinary; for
after having worked the pump for five minutes only, the
barometer-gage indicated a degree of exhauftion of 5 o 2 ;
hut by working the pump five minutes more, it indicated
a lefs degree of exhauftion, viz. 3 23. This effect I have
obferved to happen more than once.

1

Degrees of exhauftion when the pump
had been worked

■

;

r

P4ve minutes ;
according to

Ten minutes;
according to

i

Barom.

gage*

Pear-

gage.

1

Barom.

gage*

Pear-

gage*

Exp. lv. Receiver put on a leather 1
foaked in water for one night, J
Exp. lvi. Receiver put on a leather -j
foaked for one night in a mixture {
of two parts water and one fpi- j
rit of wine, — — » J

47

48

380

3o°

63

5°

8000

1200

Vol. LXVII. 4 O The

642 Mr. nairne’s Account of

The receiver was then taken off from the pump-plate,
and a blank fcrew fcrewed into the hole in the pump-
plate.

EXPERIMENT LVII.

The pump was then worked for ten minutes without
any receiver on the pump-plate. The barometer-gage
alone being afterwards connedted with it, the gage indi-
cated a degree of exhauftion of 50 only, which was the
fame as in the laft experiment; fo that the (bad effects of
ths mixture of the fpirit of wine and water ftill con-
tinued.

I then poured about two fpoonfuls of oil down the
hole in the pump-plate, and the piftons were worked
gently till molt of the oil had paffed through the pump
into a relervoir made to receive it. A blank fcrew was
then fcrewed into the hole in the pump-plate as before,
and after the pump had been worked for a minute or
two, four or five times, the air being let in between
each time, the oil had then wafhed fo much of the moif-
ture out of the infide of the pump, that I was now able
to exhauft to 430 inftead of only 50 times, as before the
oil had been made to pafs through it.

During the courfe of thefe experiments on the air-
pump it appeared, by the teftimony of the pear and baro-
3 meter-

fonts Experiments made with an Air-pump. 643
meter-gages, that the remaining contents of a receiver,
when exhaufted as much as poffible, was at different
times of different kinds ; fometimes it feemed to confift
entirely of permanent air, as when a little vitriolic acid,
&c. was put in the receiver; and fometimes moftly of
vapour arifing from moifture, and but a very fmall pro-
portion of permanent air, as when a bit of damp leather,
Sec. was in the receiver. I was now therefore defirous of
feeing what appearance the eledtric matter would exhibit
in thefe different rarified media.

For this purpofe I had a glafs tube made, of an inch
bore, and four feet and a half in length. This tube was
connedted to the receiver of the air-pump by means of
an elbow-piece of brafs,to which it was cemented ; which
elbow-piece was inferted perpendicularly in the top of
the receiver : as the elbow made a right angle, the tube
itfelf was of courfe horizontal.

Moreover, at that end of the glafs tube which was
cemented to the brafs elbow-piece, there was fixed, on
the infide, a piece of brafs wire, about three inches and
a half long, filed to a point, and pointing towards the
other end of the tube. At the other end of the tube was
cemented a brafs fcrew fitted to a brafs cap, which
fcrewed on it; and in this brafs cap was fixed a brafs
wire, three inches and a half long, which pointed towards

40a the

644 Mr. nairne’s Account of

the brafs point ; at the other end of the tube, and at the

end of this wire, was a brafs ball, eight-tenths of an inch

diameter.

The brafs cap at this extremity of the tube which is
fartheft from the receiver was made round, and placed fo
as to be in contact with the prime conductor of an elec-
trical machine.

I now firft put fome vitriolic acid into the receiver, as
a means of being able to make the remaining contents
-of the receiver, when exhaufted as much as poffible, to
confift of permanent air only, unadulterated with va-
pour ; and as the receiver was the fame I had ufed in my
foregoing experiments, there were two pear-gages fitted
to It, which pear-gages I pufhed down into the cifterns
of quickfilver at different times, and the pump was
worked as in my former experiments for ten minutes :
heat of the room 590.

The electrical machine was worked during the whole
. of the experiments.

E X P E»

fame Experiments 'made with an Air-pump. 645

experiment lviii*

-Electrical appearances exhibited.

Light began firft to appear in dallies, — — •

Light appeared the whole length of the tube in ftriae.
Tube was filled with an uniform body of pale light.
The pump had now been worked five minutes.

The pump was then worked five minutes more.
The tube was ftill filled with a uniform body of pale
light, — — — —

'Degrees of exhaus-
tion according to

Barom.

Pear-

gage.

gage.

5

8

74

3S

269

230

The conductor being then removed to a diftance from
the tube, it was made to approach it by degrees till a
fpark ftruck it, which was at the diftance of two inches ;
the light in the tube now appeared like a compact body
of fire, of a vivid purple colour, tending to a red.

Objects were feen through the tube when filled with
this body of the electrical light, no lefs diftinCtly than
if there had been no fuch light in the tube^.

The vitriolic acid being taken out of the receiver, I
put a piece of leather of 100 grains, as it came from the
leather-fellers, into that end of the tube which was next
to the conductor of the eleCtrical machine, and fartheft
from the receiver of the air-pump. I put the leather in

(a) This circumftance has been before remarked by Dr. HAMJLTON-in his
conje£tures on the tails of comets.

a

646 Mr. nairne’s Account of

at this end of the tube rather than into the receiver, to
be fure that the tube might be filled with the vapour
arifing from the damp leather rather than with the com-
mon air. The pump and electrical machine were then
worked as before.

EXPERIMENT LIX.

Ele£trical appearances.

Degrees of exhauf-
tion according to

Barom.

Pear-

Light began firfl to appear in flafhes, — —

Light appeared the whole length of the tube in ftrise,
Light vanifhed fcarce to be feen, — — —

The pump had now been worked feven minutes. The
conductor was now removed from the tube, and the
greateil If r iking diftance was found to be one inch,
The tube now appeared luminous, but the light wash
faint and white. The condu&or was then again put
in contaft with the tube, and the machine worked: >
the pump was alfo worked for three minutes more,
but fcarce any light appeared, — —

gage.

gage.

12

22

90

IOO

148

20,000

The conductor was then again removed from the
tube, and the ftriking diftance was found to be only one
inch and four-tenths: the tube at the time of ftriking
was luminous as before, and the light was of the fame
faint white colour.

Having lately received from my friend Dr. lind fome
aether prepared by the ingenious Mr. wolfe, I was very
defirous to try whether I could produce any confiderable
; ? degree

Jome Experiments made with an Air-pump. 647
degree of cold by the evaporation of aether under a re-
ceiver whilft exhaufting. For this purpofe I put the
aether into a phial, the neck of which was fufficient to
admit the ball of a thermometer : this being placed on
the air-pump, under a receiver which had a plate at the
top, with a wire palling through a collar of leathers; to
this wire the thermometer was fixed, by which means
I could eafily dip the ball of the thermometer into the
aether.

EXPERIMENT LX.

The pump was now worked, and whilft the receiver
was exhaufting, the ball of the thermometer was often
dipped into the aether; and when the degree of exhauf-
tion by the barometer-gage was 65 (which was the ut-
moft in this cafe that the pump would exhauft to) the
degree of cold indicated by the fall of the quicklilver iir
the thermometer was 48° below o on Fahrenheit’s
fcale ; fo that there was a degree of cold produced 103°
colder than the air in the room where the experiment
was made, the thermometer in it being at 55° degrees
above o. The pump was kept continually working for
half an hour, and the ball of the thermometer often
dipped into the aether ; but no greater degree of exhaul-
tion or cold could be produced. The air being let into

the

Mr. is’ atrne’-s Account of

the receiver, the quickfilver in the thermometer rofe

i o°, viz, to 38° below o.

-EXPERIMENT LXI.

Frefh aether being put into the phial to what was re-
maining, the thermometer rofe to 30° above o : the pump
was then worked again conftantly for half an hour; yet
by the barometer-gage the degree of exliauftion was
now not more than 1 6, and the degree of cold produced
did not exceed the nth degree below o, as appeared by
the quickfilver in the thermometer. The air being let
into the receiver, the remaining aether was examined,
and there were found feveral pieces of ice at the bottom
of the phial, fome of them as big as large peas, which,
when the aether became nearly of the heat of 320 or
freezing point of water, were intirely diffolved.

The air-pump with which thefe experiments were
•made exhaufted above 400 times before the aether was
jmt under the receiver.

i 649 1

XXXIII. On the Culture of Pine-apples . An extraB of a
Letter from William Baftard, Efq. of Kitley in Devon-
ihire, to Samuel Mufgrave, M. D. F. R. S. dated
Kitley, March 15, 1777. Communicated to the Society
by Dr. Mufgrave.

Read June »9>T3EFORE I enter into the particulars of
railing pine-apples in water, it will be
mecefiary to tell you that my hot-houfe is covered with
the belt crown-glafs, which I apprehend gives more
heat than the common fort of green glafs generally ufed
for hot-houfes. In the front part of the houfe, and in-
deed any where ih the lowelt parts of it, the pine-apple
plants will not thrive well in water. The way in which I
treat them is as follows. I place a lhelf near the high eft
part of the back wall, fo that the pine-plants may hand
without abfolutely touching the glafs, but as near it as
can be : on this fhelf I place pans full of water, about
feven or eight inches deep,; and in thefe pans I put the
pine-apple plants, growing in the fame pots of earth as
they are generally planted in to be plunged into the
Vol. LXVII. 4 P bark-

650 Mr. bastard on the

bark-bed in the common way ; that is, I put the pot of
earth, with the pine-plant in it, in the pan full of water,
and as the water decreafes I conftantly fill up the pan. I
place either plants in fruit, or young plants as foon as
they are well rooted, in thefe pans of water, and find they
thrive equally well : the fruit l'eared this way is always
much larger, as well as better flavoured, than when ripened
in the bark-bed. I have more than once put only the
plants themfelves without any earth, I mean after they
had roots, into thefe pans of water, with only water fuf-
ficient to keep the roots always covered, and found
them flourifh beyond expectation. In my houfe, the
fhelf I mention is fupported by irons from the top,
and there is an intervening fpace of about ten inches
between the back wall and the fhelf. A neighbour of
mine has placed a leaden ciftern upon the top of the back
flue (in which, as it is in contaCf with the flue, the water is
always warm when there is fire in the houfe) and finds
his fruit excellent and large. My fhelf does not touch
The back flue, but is about a foot above it; and confe-
quently the water is only warmed by the air in the
houfe. Both thefe methods do well. The way I account
for this fuccefs is, that the warm air always afcending to
the part where this fhelf is placed, as being the higheft
5 part

Culture of Vine-apples.

part of the houfe, keeps it much hotter than in any
other part. The temperature at that place is, I believe,
feldom lefs than what is indicated by the 7 3d degree of
Fahrenheit’s thermometer, and when the Sun fhines it
is often at above 1 oo° : the water the plants grow in feems
to enable them to bear the greateft heat, if fufficient air
be allowed ; and I often fee the roots of the plants grow-
ing out of the holes in the bottom of the pot of earth,
and fhooting vigoroufly in the water.

My hot -houfe (the dimenfions of which it may be
proper to know) is fixty feet long, and eleven feet wide
the flues included; fix feet high in the front, and ele-
ven feet at the back on the infide of the houfe. It
is warmed by two fires. A leaden trough or ciftern on the
top of the back flue is preferable to my flielf, as in it the
pine-plants grow much falter in the winter, the water
being always warmed by the flue : of this I have feen the
great benefit thefe laft two months in my neighbour-
hood. It is not foreign to this purpofe to mention that,
as a perfon was moving a large pine-plant from the hot-
bed in my houfe laft fummer, which plant was juft
fhowing fruit, by fome accident he broke off the plant
juft above the earth in which it grew, and there was
no root whatever left to it: by way of experiment I

4 P 2 took

6$ 2 Mr. bastard on "Pine- apples.

took the plant, and fixed it upright in a pan of water
(without any earth whatever) on the fhelf; it there
foon threw out roots, and bore a pine-apple that weighed
upwards of two pounds.

C «5S 3:

XXXIV. Experiments and Obfervations made in Britain^
in order to obtain a Rule for meafuring Heights with

the Barometer . By Colonel William Roy, F. R. S.

: Read June 12 and 19, and Nov. 6 and 1 3, 1777.

I N T R O D U C T I O N.

T N philofophical inquiries of every kind, where any
-*• point is to be afcertained by experiments, thefe can-
not be repeated too often, nor varied too much, in order
to obtain the truth: for even when the utmoft precau-
tion hath been ufed, and the greateft pains have been
taken, it rarely happens, that they agree fo exactly, as
to leave no room for doubt. Were it poffible at all
times, to have experiments made in circumftances per-
fectly fimilar, a confiderable degree of confiftency
might naturally be expected among the refults, where-
of the mean would determine the point in queftion;
but different men, making ufe of different inftru-
ments, have different modes of conducting their ope-
rations, each purfuing the traCt that feems to him the
moft likely to infure fuccefs. Hence it is that a variety

of

Col. roy’s Experiments for

of refults arife, and that things fometimes appear contra-
dictory, or at leaft prefent themfelves under new forms,
difficult at firft fight to be accounted for, and therefore
apt to miflead, till by a farther inveftigation of the mat-!
ter, the true caufes are difcovered. Even irregularities of
this fort are worthy of being communicated, that others
may know what hath happened before, and what, in like
cafes, they may expert to meet with, in the courfe of
their future inquiries. Improvements of every kind ad-
vance by flow degrees ; and it is not until things have
been viewed in every poffible light, that the errors,
even of our own experiments, are difcovered, the points
in queftion ultimately afcertained, and the branch of
philofophy depending upon them, gradually brought
nearer to perfection.

Ever fince the difcovery made by Torricelli, the
barometer hath been applied, by different perfons, in dif-
ferent countries, to the meafurement of vertical heights,
with more or lefs fuccefs, according to the more or lefs
perfect ftate of the inftruments ufed, and the particular
modes of calculation adopted, by the obfervers. But of
all thofe who have hitherto employed themfelves in this
way, none hath bellowed fo much time and pains, or
fucceeded fo well, as Mr. de luc, of Geneva, f. r. s. In
two quarto volumes, publilhed fome years fince, that

gentleman

meafuring Heights by the Barometer, 655.
gentleman hath given us the hiftory of the barometer
and thermometer, with a very curious and elaborate de-
tail of many years experiments, made by him, chiefly on
the mountain Saleve. It would be totally fuperfluous
here to enter into any circumftantial account of the me-
thod he makes ufe of, fince that hath already been fo
fully illuftrated by two Fellows of the Royal Society,
who have at the fame time given formulae and tables,
adapted to the meafures of this country, (Phil. Tranf. for
1774, voL-LXV. N° xx. and xxx.) that nothing farther
can be defired on that head.

It may neverthelefs be neceflary juft to call to remem-
brance that the rule, deduced from the obfervations on
Saleve, confifts of three parts, ift, The equation for the
expan lion of the quickfilver in the tube, from the effecft
of heat, whereby the heights of the columns, in the in-
ferior and fuperior barometers, are conftantly reduced-
to what they would have been in the fixed temperature
of 54°~ of Fahrenheit, independant of the preflure
they refpeftively fuftained. 2d, When the mean tem-
perature of the column of air to be meafured, is 69°. 32,
as indicated by thermometers expofed to the Sun’s rays
at its extremities; then the difference of the common
logarithms, of the equated heights of quickfilver in the

two

:6 c; 6 Col. roy’s Experiments for

two barometers, gives the altitude intercepted between
them, in toifes and thoufandth parts, reckoning the three
figures to the right hand decimals, and the others inte-
gers, the index being neglected. This temperature of
69°. 32, when the logarithmic differences give the real
height without any equation, is reduced to 39°.74, the
new zero of Mr. de luc’s fcale, when his formula is
adapted to Englifh fathoms and thoufandth parts, inftead
of French toifes. And laftly, when the mean temperature
jaf the air is above or below 39°.74,an equation, amount-
ing to t<56~oo parts of the logarithmic height for each de-
gree of difference, is, in the firft cafe to be added to, and
in the laft fubtra&ed from, that refult, in order to obtain
the real altitude.

In Mr. de luc’s book, the experiments for afcertain-
•ing the expanfion of the quickfilver, are not given in
detail; neither are the particular temperatures of the
barometers fpecified. The winter feafon was however
chofenforthepurpofe; one being left in a cold room, and
the ether in a clofet, heated as high as could conveniently
be fuffered. The operation having been repeated feveral
'times without any effential difference in the refults, this
•general conclufion is drawn, that between the tempera-
lures of melting ice and boiling water, the expanfion of

the

measuring Heights with the Barometer. 657
the quicksilver is exactly fix French lines, or .532875
decimal parts of an Englifh inch. But it is to be ob-
ferved, that the barometer flood then at 28.77525 ;
whereas, if it had flood at 30 inches, it would have been
• 555556, becaufe the expan lion is in proportion to the
length of the column. Farther, the interval between the
freezing and boiling -points in all thermometers, varies
with the height of the barometer, or weight of the atmo-
fphere; and it is the cuftom in England to make thermo-
meters when the barometer Hands at 30 inches; that is
to fay, 1 . 2 2 5 or 1 3 . 8 Fi'ench lines, higher than when Mr,
de luc’s boiling point was fixed : and fince from his ex-
periments it appears, that each line of additional height
in the barometer, raifes the boiling point TJE-4-th part of
the interval between that and freezing, it follows that
ttj4 = 0.158 x 13.8= 20. 2, will denote the number of
degrees, that Mr. de luc’s boiling point is lower than
- that of Englifh thermometers, which reduces it to 209.8
of Fahrenheit, and makes the interval between freez-
ing and boiling only 177.8 degrees. Hence the expan-,
fion .555556, formerly found, muft be increafed in the
proportion of 177.8 to 180, which gives for the total
.5624297 or .56243, on a difference of temperature of
1 8o°. Thus the expanfion for each degree, fuppofing it
Vol. LXVII. 4 Q to

658 Col. roy’s Experiments for

to be arithmetical, or uniformly the fame in all parts of

the fcale, will be .00312461 (a>.

Having now fhewn the expanfion of quickfilver in the
tubes of barometers refulting from the Geneva obferva-
tions, I fhall next proceed to give fome account of thofe
I made for that purpofe. They derive their origin from
my having very accidentally obferved, that a fmall de-
gree of heat, and of fhort duration, fenfibly affedted the
length of the column in Mr. rams den’s portable baro-
meter, whereof a view is given in plate XVI. The
principal parts of this inftrument are a fimple ftraight
tube, fixed into a wooden ciftern, which, for the conve-
niency of carrying, is fhut with an ivory fcrew, and, that
being removed, is open when in ufe. Fronting this aper-
ture is diftindtly feen, the coincidence of the gage-mark,
with a line on the rod of an ivory float, fwimming on the
furface of the quickfilver, which is raifed or deprefled by
a brafs fcrew at the bottom of the ciftern. From this, as
a fixed point, the height of the column is readily mea-
fured on the fcale attached to the frame, always to

(a) This paper having lately been communicated to Mr. de luc, he hath
informed me, that the difference of temperature in his -experiments, amounted
to about 3 1° of reaumur, or 720 of Fahrenheit,, above freezing : where-
fore, .00312461x72=1.225 nearly, will denote the rate of expanfion from
which he deduced that for ’8o°; and within thefe limits, it will hereafter be
ound to differ very little from the refult of the prefent experiments.

T

part

Th>/of.T)vns. Vol.ZXn/.rab.Xi:j>. fad .

meafuring Heights with the Barometer . 659

part of an inch, by means of a nonius moved with rack-
work. A thermometer is placed near the ciftern, whofe
ball heretofore, was ufually inclofed within the wood
work, a defedt that hath been lince remedied. The three-
legged Hand, fupporting the inftrument when in ufe,
ferves as a cafe for it, when inverted and carried from
place to place. Two of thefe barometers, after the quick-
filver in them hath been carefully boiled, being fuffered
to remain long enough in the fame fituation, to acquire
the fame temperature, ufually agree in height, or rarely
differ from each other more than a few thoufandth parts
of an inch, which were conftantly allowed for in calcu-
lating altitudes, as well as in eftimating the rate of expan-
fion, in the courfe of the following experiments.

SECTION I.

. Experiments on the expanjion of quickjilver.

THE experiments made for this purpofe were nu-
merous as well as various, and were therefore fubdivided
into feveral claffes. To give a minute detail of them all,
would be extremely tedious, and now wholly ufelefs,
hnce it was from thofe of the third dafs alone, that the
" 4 O 2 . rate

'C 6 o Col. roy’s Experiments for

_rate as well as maximum of expanfion was afcertained :

• •

wherefore thofe of the two preceding claffes need only
be mentioned in a general way.

The firft fet of the firft clafs comprehended fuch as
were made with one barometer in a cold room, or in the
open air, and the other in a room on the fame level with
the former, where there was conftantly a fire, which was
occafionally increased, in order to augment the difference
of temperature. When the heated barometer had re-
mained feveral hours in an angle of the room, the dif-
ference of temperature of its quickfilver above that of
the coldeft, as indicated by their refpedtive attached ther-
mometers, rarely exceeded i o or 1 2°, which, from a
mean of many obfervations, gave an expanfion of .0333
decimals of an inch, for the 1 o° comprehended between
32 and 42°of Fahrenheit’s thermometer. So far the re-
fult ariling in this way, from fmall differences of tem-
perature, will be found to agree with the third clafs of
^experiments.

But when, in the fecond fet of this firft clafs, the dif-
ference of temperature was augmented to 20 or 30°, by
expofing the barometer within doors to a greater heat,,
or placing the fuperior one on the leads, whereby it re-
ceived the direift and reflected rays of the Sun through-
out the greateft part of the day, while the other was kept

meafuring Heights with the Bafmieter. 66 x
in the cold area underneath, the rate of expan fion for
the firft io° exceeded that formerly found nearly in
-the proportion of three to two, while that for the fecond
and third terms, of io° each, diminifhed progreflively.

The chief, though not the only caufe of this great
difference, as will appear hereafter, arofe from the peti-
tion of the ball of the thermometer, originally inclofecl
within the wood-work of the frame, which prevented it
from receiving the heat fo readily as the quickfilver in;
the tube ; at the fame time that it retained it longer, and;
confequently produced refults in fome degree fallacious..

Finding, from the firft clafs of experiments, that much;
uncertainty remained with regard to the rate of expan-
fion of quickfilver affedted by thefe fmaller degrees of"
heat, and that it was utterly impoffible, from them, to.
determine its maximum for the i8o° between freezing
and boiling; I refolved to try, .how much a column of 30
inches of quickfilver, carefully boiled in a tube, would,
lengthen, the fame being placed with the open end rip-
wards in a tin veifel, occafionally filled with pounded ice.
and water, and afterwards brought to boil, by means of a
charcoal fire placed underneath ? In this fecond clafs, it
was eafy to fee, that the expan fion of the tube containing
the quickfilver,. was neceffarily to be taken into the ac-
count, and added to that apparently found by experi-
•2 menh.

662 Col. roy’s 'Experiments for

merit. This was of courfe to be done, either by fuch dif-
ferences as I could difcern and meafure, or by thole that
had refulted from the experience of others.

The nature of the apparatus, employed in this clafs of
experiments, will be ealily underftood from plate XVII.
where it is reprefented, as it was ufed in tbofe of the third
clafs. In its firft ftate it was not quite lb long, and a
chafing-dilh with a charcoal fire, occupied the place of
the ciftern holding the quicklilver below By means of
a circular bit of tin, foldered edgeways in the center of
the bottom, and an aperture in the middle of the lid, the
tube was kept lleadily in the axis of the vefiel. Other open-
ings in the lid, ferved for the admiffion of the thermo-
meter, and the application of a deal rod clofe to the fide
of the tube, when its height was to be meafured. The
longitudinal expanfion of the glafs was marked by a
fcratch thereon with a fine edged file at the top of the
deal rod, when refpectively at the temperatures of freez-
ing and boiling. The apparent dilatation of the quick-
filver was in like manner marked, by the coincidence of
its furface with the lower edge of a brafs ring embracing
the tube.

It having been found impoffible to procure tubes
whofe bores were truly cylindrical, or of any uniform
figure, the experiment was repeated, as often as poffible,

in

meafuring Heights with the Barometer . 663

in both ends of the fame tube, that the mean might be
taken. But it frequently happened that the tube, which
had undergone one or more experiments in one end,
broke before any could be made with it in the other. In
this cafe, the rate of expan fion in the lafl: end was taken
from that given by fuch another tube, where it had fuc-
ceeded in both. The mean of five refults with the bell
tubes, taken in this way, gave .4901 for the apparent
expanfion of 30 inches of quickfilver, on 180° of Fah-
renheit, between freezing and boiling, which being
augmented by the apparent longitudinal dilatation of the
glafs .0356X 3 = .io68, the real expanfion is .5969; ex-
ceeding Mr. de lug’s by more than ~ths of an inch. If,
however, Mr. s me aton’s dilatation of glafs, (.023 x 3 =
.075) be fubftituted, inftead of that refulting from thefe
experiments, the real expanfion of 30 inches of quick-
filver will be .5651, which does not exceed it quite
parts of an inch.

In this clafs of experiments, having attended as dili-
gently as poffible to all the circumftances, it feemed to
me, that tubes with a fmall bore, and whofe glafs was
thick, lengthened more than thole, which had a larger
bore and whofe glafs was thin: whence I was led to
fuppofe, that folid glafs rods would dilate more in pro-
portion, and confequently, fhew a frill more perceptible

difference.

664 “Co!, roy’s Experiments for

difference. With the view of afcertaining this point, I
procured four glafs rods near three feet long each, and of
different diameters, the largeft being of the lize of the
little finger, and the fmalleft about the thicknefs of a
quill. One end of each, was fomewhat larger than the
other, and was made perfectly fmooth, as that on which
they were to reft when feverally meafured with the deal
rod. They were then all placed in the tin veflel, in fuch
a manner, as to admit pounded ice rammed very clofe
around them, and the interftices to be filled with water.
Having remained in that ftate a full half hour, they were
feverally meafured with the deal rod, whofe length of
3 2j inches was fcratched on each with the fharp edge of
the file. This being done, the ice thrown out, and the
veffel carefully wafhed, all the rods were replaced in it,
immerfed in water, which afterwards was brought to boil.
The fire being kept up, and the ebullition rendered as vio-
lent as poffible for half an hour, the glafs rods were then
feverally meafured, by applying them one after another
to the deal rod, Handing with them in the boiling water.
The experiment was repeated three times, on as many dif-
ferent days, without its being poffible to difcern, that any
of the glafs rods had dilated more than that of deal, from
a difference of temperature of 1 8o°. In all of them, the
freezing mark feemed accurately to coincidewith the top

of

meafuring Heights with the Barometer . 665

of the deal rod ; whereas the dilatation of the tubes, by
the fame degree of heat, was always very vifible lb) .

Finding from the fecond clafs of experiments, whereof
the general refult hath now been given, that glafs rods
feemed not to lengthen more than deal; and that tubes
of different bores, and probably too of different forts of
glafs, were fufceptible of different degrees of extenfion,
which rendered it impoflible, by this means, to afcertain
the longitudinal expanfion of the quickfilver they con-
tained; I thought it neceffary to recur once more to the
barometer, and to try whether it could not be fo con-
trived as to a£t in water of different temperatures, from
freezing to boiling. This led me to the experiments of
the third clafs : and in order to comprehend them tho-
roughly, it feems neceffary to point out fome few altera-
tions which the apparatus underwent.

The center of the bottom being pierced on purpofe, a
brafs focket was prepared for it, wherein a hole was bored
conically, to receive the ground-end of a barometer tube,
of the ordinary length of 3 3^ inches ; the tube having
been firfl ground in a feparate piece of brafs, and ulti-

(b) Since thefe experiments were made, tlie relative expanfion of 18 inches
©f one of the tubes and one of the rods that had been formerly employed, was
found to be, by Mr. cumming’s pyrometer, nearly as 4 to 1, from a heat
approaching to that of boiling oil.

Vol. LXVII. 4 R mately

666 Col. roy’s Experiments for

rnately in the focket itfelf, fitted it fo exactly, as to fuffer
no water to pafs. The focket being inferted into the
aperture at the bottom of the veffel, was firmly foldered
to it for the reception of the tube, which was fo ground
as to reach a full inch and a half below the furface of
the brafs. It could not defcend farther, the ground parts
in both being of the figure of the fruftum of an inverted
cone. From the view in the plate it will appear, that un-
derneath the veffel, a feparate Hand was placed, in order
to fupport the iron cittern containing the quickfilver.
The diameter of the cittern was fuch, that its ttand being
occafionally moved, fo as to bring one fide of it clofe to
the ground part of the tube, the other fide projected be-
yond the bottom of the veffel; and confequently per-
mitted the rod of a float, retting on the furface of the
quickfilver, to rife freely and parallel to the axis of the
tube. The rod was of deal, f^th of an inch fquare, car-
rying on its top a fcale, whofe zero lay in the lower fur-
face of the float, and whereof the fix uppermott inches,
from 2,8 to 34, were divided into zoths.

That the whole column of quickfilver might alter-
nately be covered with the freezing mixture and water
of different temperatures, and yet permit its furface to
be feen, two eyes of plate glafs were fcrewed into fockets,
foldered for that purpofe oppofite to each other, near the

top

meafuring Heights with the Barometer. 667
top of the veffel, which, in the firft fet of the third clafs
of experiments, was little more than 29 inches high.
The top of the tube palling through the aperture in the
lid, one and a half or two inches of the vacuum gene-
rally rofe above the veffel. That the expanlion of the
column might be meafured as nearly as poflible in that
part of the tube fronting the center of the eyes, more or
lefs quicklilver, according to the It ate of the atmofphere,
was occalionally put into the cittern, to raife or deprefs
the furface of the column to the proper height. A thin
brafs ring, whofe lower parts were made to fpring, em-
braced with fufficient force the upper part of the tube,
permitting it at the fame time to be moved freely with
the hand. It carried along with it a nonius index, pro-
jecting as far as the center of the rod, and confequently
applying itfelf to the divilions of the fcale, which was
kept in its proper polition by palling through a flit fitted
for it in an arm attached to the lid. The divilions on the
nonius being the fame with thofe of the barometer for-
merly defcribed, the height of the quickfilver could
always be read off to — th part of an inch.

The quickfilver having been carefully boiled, as on
former occafions, in the tube ; and that being filled com-
pletely, and held with its open end upwards; the tin
veffel was inverted over it, and lowered gradually, till the

4 R 2 ground

668 Col. roy’s Experiments for

ground end could be inferted into the focket with fuch a
degree of force as to prevent it from being too eafily re-
moved. The finger being then applied clofely to the
open end of the tube, the whole apparatus was turned
up, and placed over the ciftern into which the quickfilver
had previoufly been put, great care being taken not to
remove the finger till the lower extremity of the tube
was fairly immerfed into the quickfilver; when that in
the tube was permitted to defcend into an equilibrium
with the atmofphere. In the firft experiment it was
found that the water iffued by the eyes, and running
down the fide of the veflel, fell into the ciftern. In order
to remedy this inconveniency, a circular piece of tin was
foldered round the upper part of it, immediately below the
eyes ; and a flat fpout, projecting from it, ferved as a gut-
ter to throw off the water from the ciftern, and from the
lamps made ufe of to bring that in the veflel to boil. Six
lamps, each with a double light, were fufpended around
the trunk of the veflel, to heat the water as equally as
poflible; though any irregularity of this kind was fuffi-
ciently guarded againft, by conftantly mixing it during the
operation. Another lamp of the fame kind flood under
the ciftern, whereby the quickfilver there was kept at
the temperature of the water in the veflel, each having
its proper thermometer: this laft lamp was placed

and

meafuring Heights with the Barometer. 669
and difplaced frequently, during the courfe of every ex-
periment ; for the heat was very expeditioufly commu-
nicated to the iron cittern, and thence to the quickfilver
it contained ; and both were found to cool very faft, after
the lamp was removed. Such was the ftate of the appa-
ratus, when the firft fet of this third clafs of experiment*
was made. In thofe of the fecond fet, its height was far-
ther augmented by tin foldered to the top, that a tube of
the ordinary length might be wholly immerfed in boil-
ing water. The third and laft alteration confifted in the
occalional application of a detached tin cafe, equal in
diameter to the upper part of the veffel, having a hole in
its bottom to admit the top of a long tube to pafs. This
cafe was fo contrived, that its bottom flood two inches
and a half higher than the lid of the veffel, thereby al-
lowing room for the hand to move the index up or
down. In this ftate the apparatus is reprefented in the
view; and its various ufes will be beft underftood from
the account of the experiments, which were fubdivided
into four lets.

Thofe of the firft fet were made with tubes of a large
bore, upwards of three-tenths of an inch in diameter, of
the ordinary length, with a vacuum over the quickfilver
of two inches and a half or three inches, part of which
reached above the top of the veffel. The mean of three

expert-

670 Col. roy’s Experiments for

experiments gave .5258, for the total dilatation of 30
inches of quickfilver, on 1 8 o° between freezing and boil-
ing; that, anfwering to the firft 20% between 320 and
5 20, was .0688; that, for the 20° in the middle of the
fcale, between 1 1 20 and 1 3 20, was .058; and the rate for
the laft 20°, between 1920 and 212°, was only .041.
From this firft fet of the third clafs of experiments, it ap-
-peared evident, that the expanfion of 30 inches of quick-
iilver in the barometer, fuffering a heat equal to 1 8o° of
Fahrenheit, inftead of exceeding Mr. de luc’s, as ap-
peared to be the cafe from the refults of the open tube,
really fell ftiort of it : and inftead of being arithmetical or
uniformly the fame, for equal changes of temperature, was
aftually progreftive ; the expanfion anfwering to the lower
part of the fcale, being greater than that correfponding to
the middle; which again exceeded that for high tempe-
ratures. In thefe experiments, when the water had ac-
quired aheat 2 o or 3 o degrees greater than that of the open
air, a certain duftinefs was perceived in the vacuum of
the tube. At ioo° of Fahrenheit, or thereabout, this
appearance had fo far increafed, as to fhew clearly, that
it could proceed from no other caufe than a vapour ari-
fing from the furface of the heated quickfilver, quite in-
vifible, till, by its condenfation in the cold part of the
tube, it was formed into balls, every where adhering to

its

meafuring Heights with the Barometer . 671

its fides and fummit. Thefe globules were very fmall
near the furface of the water, augmenting gradually as
they approached the top of the tube, where they were
greateft : their bulk increafed with the heat ; and when
the water was at or near boiling, they would fometimes
unite, and defcend by their own gravity, along the fides of
the tube, into the general mafs. Hence the progreffive di-
minution of the rate of expanfion of the column of quick-
filver in the barometer, perceptible even in the firft clafs
of experiments, is eafily accounted for by the refiftance
of the elaftic vapour^, acting againft the top of the tube^
which was here colder than the reft.

But in the application of the barometer to the mea-
furement of heights, the whole inftrument is of the fame
temperature ; wherefore, in the fecond fet of this third
clafs of experiments, the tin veflel was heightened, that;
tubes of the ordinary length, placed in it, might be wholly
immerfed in boiling water. The mean of four experi-
ments, which agreed very nearly among themfelves,.,
gave .5117 for the total expanfion between freezing and
boiling; for the a o°, between 1120 and 132^059; and
for the laft ao°, between 1920 and 21a0. 046. In thefe-

(c) Having mentioned the circumftances to Mr. ramsden, it firft occurred-
to him, that the refiftance of the elaftic vapour was the caufe of the diminu-
tion in the rate of expanfion.

expert- -4

672 Col. roy’s Experiments for

experiments, the tube being wholly covered with boiling
water, no condenfation of vapour took place in the va-
cuum; and therefore no particles of quickfilverwere feen
adhering to the upper part of the tube. When the wa-
ter boiled, the refiftance of the vapour was greater than
in the preceding fet, and the total expanlion lefs. Thefe
two refults ferve ftrongly to confirm each other: it is,
however, the laft that furnillies the data for conftrudting
the table of equation depending upon the heat of the
quickfilver in the barometer, of which table we fhall
give an account hereafter.

Finding, from the comparifon of thefe two fets of ex-
periments with each other, that the maximum and rate
of expanfion feemed to vary with the length of the va-
cuum above the quickfilver, I was advifed to try^ what
might be the refult, when the vacuum was much longer
than in the common barometer.

The third fet of experiments of this clafs was there-
fore made with a tube fomewhat narrower in the bore
than the former, and whofe vacuum was 1 \\ inches in
length, whereof 1 reached above the top of the veflel.
The mean of three obfervations gave .5443 for the total
expanfion on 1 8o°; that for the firfi: 20° wras .067 ; for

(d) Dr. blagdeNj who afterwards affifted in fome of the hrft experiments
with the manometer, propofed that with the long tubf .

the

meafuring Heights with the Barometer. 673
the 200 in the middle of the fcale .058 ; and for the 11 p-
permoft 20°. 065 : whence the mean rate for every 20%
is nearly .0605 (eK In this fet, the condenfation in the va-
cuum of the tube was particularly attended to: it began,
as in thofe of the firft fet, immediately above the furface
of the boiling water, which was always kept an inch or
two above the top of the column : the lowermoft glo-
bules were very fmall, increafing gradually till they got
without the lid of the veflel, where they were the largeft;
thence they diminifhed uniformly upwards, and dilap-
peared entirely three or four inches below the top of the
tube. Though the rate for the middlemoft ao°, in thefe
laid experiments, be below the mean, probably from fome
inaccuracy in obfervation ; yet, being compared with the
former fets, they ftill ferve to corroborate each other : for
in thefe with the long tube, the vacuum feems to have
been either completely maintained, or nearly fo; and we
accordingly find the maximum of expanfion increafed,
and its rate rendered nearly uniform, as will be farther
confirmed from what follows.

(e) Mr. cavendish, who affifted in the firft part of the experiments with
the open tube, informed me, that, in thofe made by his father Lord Charles,-
the difference between the expanfion of quickfilver and glafs, from 180° of heat,
was .469. If to this we add Mr. smeaton’s dilatation of giafs, the total
expanfion of 30 inches of quickfilver will be .544, which agrees with the
experiments in the long tube, and gives a rate of only .003022 for each degree,

4 S

Vol. LXVIL

I have

674 Col. roy’s Experiments jor

I'have already had occafion to mention that a detached
tin cafe was fometimes applied above the veffel, in which
ftate it is reprefbnted in the view. This method was
thought of during the operations with the long tube, in
order to try whether the vacuum was completely main-
tained by the temperature of the open air? For this pur-
pofe the cafe was placed on the ftones of the yard, with
a fmall tube inferted in it, to preferve an open paffage.in
the middle: it was then rammed full of a compofition.
of fait and ice; and afterwards fixed on the top of the
long tube. The degree of cold thus applied round the
greateft part of the vacuum, muft have been very great,
probably near the zero of Fahrenheit; yet it produced
no vifible alteration in the height of the column of

O

quickiilver, which ftill remained in boiling water below,
and lhould have rifen, if the vacuum had been formerly
incompleat. As it would have occafioned much trouble
to have lengthened the feveral parts of the apparatus fo
as to have kept the long tube wholly in boiling water,
the counterpart of this laft experiment was not made in
the accurate manner it ought: neverthelefs, the tin cafe,
being emptied of its cold compofition, was placed on
the tube as before, and filled with boiling water; which,
joining with the intermediate fteam arifing from that in
the veffel below, muft have kept the whole nearly in the

fame

meafuring Heights with the Barometer. 675
fame temperature. The confequence of this, application
was, that the column fhortened about -^ths of an inch;
which feems to prove, that the quicklilver vapour now
reached the fummit of the tube, and, acting againft it,
overcame, by fo much, the preffure of the atmofphere.

Ifhould nowproceed to give feme account of the fourth
fet of this laft clafs of experiments, made on the con-
denfation of the quicklilver, by means of artificial cold,
below the temperature of the air. Previoully however
to this, it may not be improper to take notice, in a more
general way, of fome others that were made on expan-
fion; as tending, with certain circumftances yet to be
mentioned, not only to confirm thofe already deferibed,
but likewife to account for many irregularities that occur
in operating with barometers.

In the courfe of the preceding experiments, from ac-
cidents of various kinds, it was often necefiary to reboil
the quicklilver; and in that operation, many tubes were
broken. The frequent removal of the focket from the
bottom of the veflel, in order to get others ground for it,
became at laft very troublefome ; and made more caution
neceflary, in boiling fuch as were ground, efpecially in
frofty weather, which happened to be the cafe in the laft
days of March, 1775: wherefore it was thought bell in the
interim to try, what might be the expanfion of a column

4 S 2 of

6 j6 Col. koy’s Experiments for

of quickfilver, carefully put into the tube, but not boiled
therein ?

With this view, the ftandard barometer and apparatus
were left out during the night of the 29th, that they
might acquire the fame temperature, which was found
next morning to be 34°7; the unboiled quickfilver Hand-
ing -^oth of an inch higher than that which had been
boiled. The lamps being applied to the velfel, the
lengthening of the unboiled column was perceived, on
the whole, to be more irregular, and the progreffive di-
minution quicker, than in former experiments ; fo as to
give, for the maximum of expanfion, only .443 for 1 8o°.

On the morning of the 31ft, the unboiled column,
which on the preceding day had been the higheft, was
lower than the other by near—ths of an inch, the tempe-
rature of both being 3 i°~. As the water acquired heat
from the. application of the lamps, the rate of expanfion
diminifhed; and,. at boiling, was only .405 fori8o°. The
operation of the 30th feems to point out, in a manner
fufficiently conclufive, that the air contained in the un-
boiled quickfilver, rendered its fpecific gravity lefs, than
that which had been boiled even a great while before ;
fince it required a longer column of the firft, to counter-
balance the weight of the atmofphere. And though the
vacua might poflibly, at the beginning, have been equally

compleat

meafuring Heights with the Barometer . 677

compleat in both ; yet they could not continue long fo :
for the air ettaping gradually from the unboiled quick-
lilver, its elafticity increaling with the heat, and uniting
with the quickfilver vapour, mull have refilled the dila-
tation of the column, and rendered it lefs than on for-
mer occafions; which actually appeared from experi-
ment. This is farther confirmed by the obfervations of the
fubfequent day ; for now the unboiled column was be-
come the Ihorteft, owing no doubt to more air having,
attended, and rendered the vacuum Hill more incom-
pleat. Thus, the caufes of refiftance increaling, the di-
latation is leflened in a fuperior degree.

The other circumttances to be mentioned, occurred on
the 1 2th of April. After finilhing one of the experiments
of the fecond clafs, and when the water had cooled to 19 2°,
the vettel, by accident, received a fudden jolt, whereby
the mouth of the tube mull have been raifed, for a mo-
ment, out of the quickfilver in the cittern. In a few mi-
nutes after this, intending to obferve how far the column
had fbortened from the decreafing heat, I was furprized
to find, that the quickfilver had wholly difappeared in
the tube, and was funk fo lo w as not to be feen by looking
obliquely down at the eye of the vellel. It was then cer-
tain that air, and probably a particle of moifture along
with it, had attended into the upper part of the tube,

whereby

678 Col. roy’s Experiments for

whereby the vacuum was deftroyed in fo remarkable a
degree. Since this accident made it neceffary to reboil
the quickfilver, the water (then between 1 8o° and 1 90°)
was let out by the cock fixed for that purpofe at the
bottom of the veflel; but before it could be intirely
drawn off, the tube and its contents, had fo fenfibly felt
the condenfing force of the furrounding atmofphere,
then about 48°, that the quickfilver had rifen again, and
prefented itfelf oppofite to the eye of the veflel, fome-
thing lower indeed than where it formerly flood. On
this difcovery, and as foon as water could be boiled for
the purpofe, the veflel was filled again, when the quick-
filver fubfided, as before, quite out of fight ; and on draw-
ing off the water a fecond time, it rofe anew, feemingly to
its former height.

The appearance, which this accidental circumftance
produced, was fuch, as naturally fuggefted that farther
experiments might have been made, varied as much as
pofiible from each other, by the admiflion of different
quantities of air, or of air and moifture intermixed. But
the nature of the vefiel rendering it impoflible to fee,
and confequently to meafure, the motion of the quick-
filver, occafioned by the alternate expanfion and conden-
fation of the elaftic vapour contained in the upper part
of the tube, and which could not have been accom-

plifhed

meafuring Heights with the Barometer. 679
plifhed without many troublefome alterations in the ap-
paratus, therefore nothing of the kind was attempted.
From the circumftances juft now mentioned, it will be
readily conceived, how much care is neceflary in ope-
rating with barometers for the meafurement of heights,
that the vacua be as nearly as poflible compleat; and par-
ticularly, that no moifture get up into the tube. I now
proceed to the fourth and laft fet of experiments.

Having found, from the two firft fets of this clafs, the
rate of expanfion of a column of quickfilver, in the tube
of a barometer of the ordinary length, to be progreffive
and not arithmetical ; and that its maximum, for the 1 8o°
comprehended between feeezing and boiling, was lefs
than had been fuppofed; I thought it proper to try, by
means of artificial cold, whether the condenfation, for the
3 20 below freezing, followed nearly the fame law ?

For this purpofe the tin veflel, containing the ground
tube, was rammed quite full of pounded ice and fait, as
well as the tin ftand holding the iron cittern below. In
this operation, twelve pounds of ice and four pounds of
fait were employed, whereby the mean temperature of
the mixture was reduced to + 40 of Fahrenheit. But be-
fore the eyes of the veflel could be fufficiently freed
from the compofition, fo as to permit the furface of the
column to be diftincftly feen and read off; it had rifen to
5 + 14°

68o Col. roy’s Experiments for

+ 1 4° ; the temperature of the air, and alfo of the ftandard
barometer, being at the fame moment 49°^-. The ob-
ferved condenfation, arifing from this difference of 350-',
was JtLths of an inch; or .1189, when reduced for the
height of the barometer, which then flood at 30.296.
Hence the condenfation for 3 20 is .1072, or .00335 for
each degree. In this day’s experiment, when the tempe-
rature of the mixture had rifen to 3 20, that of the air
and ftandard barometer was 52°^; whence the reduced
difference, for the 20° between 320 and 52°, was found
to be .0664, anfwerable to former experiments.

The fame experiment was repeated two days after,
with great care, the veffel being filled no higher than the
furface of the quickfilver. The mean temperature of the
mixture was now + 4% and that of the ftandard barome-
ter 490’-. The obferved condenfation, arifing from this
difference of 45°^, was or .1594, when reduced for
the height of the barometer, then ftanding at 30,416:
hence the rate for 320 is .1127, or .003,522 for each
degree. When the temperature of the mixture had
rifen to 320, that of the air was 510: whence the aug-
mented rate for the 2 o°, between 320 and 5 20, was found
to be .0662.

From the mean of thefe two experiments it appears,
that the condenfation of a column of 30 inches of

quickfilver

T kilos. Thins. Vol.TXVll.TaiJTVI. A ffStf .

meafuring Heights with the Barometer. 6 8 r

quickfilver in the barometer, affected by the 3 2° of cold
below freezing, is .1099: and that the expanfion from
20° of heat, between 320 and 520, is .0663, a number
agreeing perfectly well with former refults. If the con-
denfation .1099 thus found, be added to the expanfion
• 5117 arifing from the fecond clafs of experiments, we
fhall have .6216 for the total difference of height of the
columns of quickfilver in two barometers, fulfaining the
fame preffure, but differing from each other in their tem-
peratures ai2° of Fahrenheit’s thermometer.

The feries of numbers exprefled in the annexed table,
agreeing in all effential refpects with the expanfions
found by experiment, will therefore fhew that which
correfponds to any intermediate temperature, for every
I o° of the fcale.

4T

Vol. LXVII.

Rate

68a

Col. Roy’s Experiments for

Rate of expanfion of a column of quickfilver in the tube

of a barometer.

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Con

rneafuring Heights with the Barometer . 683

ConJiruBion and application of the table of equation, for
the expanfton of the quickfilver in the tubes of baro-
meters.

Ia the introduction to this paper there was occafion to
remark, that in the application of the barometer to the
meafurement of heights, various modes of calculation
had been adopted. The eafiefl and bell method feems
however to be, by means of the tables of common loga-
rithms, which were firft thought of by Mr. mariotte,
and afterwards applied by Dr. halley, Mr. bouguer,
Mr. de luc, and others. They have all proceeded on
the fuppolition, that air is a truly homogeneous and elas-
tic fluid, whofe condenfations being proportionable to
the weights with which it is loaded, its dilatations are in
the inverfe of the weights; and in confequence of this
law, that the heights of the atmofphere afeended, are in
geometrical progreflion, while the correfponding fuc-
ceffive defeents of the quickfilver in the tube of the
barometer, are in arithmetical progreflion.

Mr. de luc makes ufe of an arithmetical or uniform
equation for the heat of the quickfilver in his barome-
ters, whereby their relative heights are reduced to what
they would have been in the fixed temperature of 54°^

4 T 2 of

684 Col. roy’s Experiments for

of Fahrenheit. In the formulae adapting his rule to
Englifh meafures (Phil. Tranf. vol. LXVII. N° xx. and
xxx.) hath been fhewn, that the eafieft and fimpleft me-
thod is, to make the difference of temperature of the two
barometers the argument for the equation ; and that it is
fufficient to reduce either column to what would have
been its height in the temperature of the other. But
whatever may heretofore have been the method of ufing
the equation for the heat of the quickfilver, while it was
con fide red as arithmetical ; now that it hath been fhewn,
from the preceding experiments, to be progrelfive, there
feems at leaft to be propriety in applying to each baro-
meter the equation anfwering to its particular tempera-
ture. And though, for this purpofe, any fixed tempera-
ture might have been affumed at pleafure, as that to

which both barometers were to be reduced; yet, the

(

freezing point being fundamental in all thermometers,
and that being likewife the zero of the fcale for the equa-
tion depending on the heat of the air, as will be fhewn
hereafter, it hath been preferred to any other.

From the experiments it appears, that a column of
quickfilver of the temperature of 320, fuftained, by the
weight of the atmofphere, to the height of 30 inches in
the barometer, when gradually affected by different de-
grees of heat, fuffers a progreffive expanfion ; and that,

having

mea/uring Heights with the Barometer. 685
having acquired the heat of boiling water, it is lengthened
t<to"6^o parts of an inch : alfo, that the fame column, fuffering
a condenfation by 3 a° of cold, extending to the zero of
FAHRENHEIT, is fhortened parts, the weight of the
atmofphere remaining in both cafes unaltered; but that,
in the application of the barometer to the meafurement of.
altitudes, fince the preffure and length of the column
change with every alteration of vertical height, the
equation, depending on the difference of temperature of
the quicklilver, will neceffarily augment or diminifh by
a proportionable part of the whole. Thus, if the weight
of the atmofphere fhould at any time be fo great as to
fuftain 3 1 inches of quicklilver, the equation for dif-
ference of temperature will be juft T~th part more than
that for 30 inches; at 25 inches it will be {ths ; at 20
inches yds; at 15 inches^; and at 10 inches only |d of
that deduced from experiment.

It is upon thefe principles that the annexed table of
equation hath been conftructed, for differences of tem-
perature extending to 102° of the thermometer, and for-
heights of the barometer from 1 5 to 3 1 inches ; beyond
which limits, it is not probable, that many barometrical
obfervations will be made. The firft or left-hand co-
lumn, fhews the height of the barometer for every half
inch, from 31 to 25 ; thence for every inch downwards

to

686 Col. Roy s Experiments for

to 20; the 15th inch being half of the obferved expan-
llon. The five next columns towards the right, compre-
hend the additive equation for condenfations, anl'wering
to o°, 120, and 220, with their intermediate differences;
thofe that are progreffive, as aiiiing from difference of
tempei'ature, being ranged horizontally; and thofe that
are arithmetical, as depending on the height of the ba-
rometer, being placed vertically. The temperature of
3 20 requires no equation, and the thirteen columns from
thence towards the right hand, contain the lubtradfive
equations for expanfion, correfponding to every io° as
far as 102°, with their progreffive and arithmetical dif-
ferences ranged as before. By means of thefe differences,
the equation for intermediate temperatures may readily
be taken out by infpedtion. Hence is deduced the firft
part of the rule for meafuring heights by the barometer.
When the temperature of the quickfilver is below 320 of
Fahrenheit, add the correfponding equation for con-
denfation to the obferved heights of the columns reflec-
tively; when above 320, fubtradt the equation for expan-
fion from the obferved heights of the columns refpec-
tively; with which equated heights of quickfilver, ex-
preffed in 1 oooth parts of an inch, the tables of loga-
rithms are to be entered.

Table

[ 687 ]

Table, {hewing the equation to be applied to the obferved height of quickfilver in the barometer, from 15 to 31 inches; and for differences of
temperature extending to 10 2° of Fahrenheit : whereby the column is reduced to the height it would have flood at in the .temperature of 320.

Oblerved I

height of Condenfation below 320; Equation to be added to the
quickfil- height of the quickfilver in the barometer,

Expanfion above 320; Equation to be fubtraaed from the height of the quickfilver in the Barometer.

Barom.

o°

Diff.

12°

Diff.

22°

32"

42°

Diff.

52°

Diff.

62°

Diff

720

Diff.

82°

Diff. '

|92°

Diff.

102°

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SECTION

meafuring Heights with the Barometer .

SECTION II,

Experiments on the expanfion of air in the Manometer *

WITH refpedl to order of time, the manometrical
experiments were made fubfequently to the chief part of
the barometrical obfervations, from which alone an ap-
proximate rule had previoufly been deduced for the mea-
furement of heights : neverthelefs, in this paper it feemed
to me belt, that what related to the expanfion oS air in
one inftrument, fhould immediately fucceed the expan--
lion of quickfilver in the other.

The thermometer made ufe of in thefe experiments
is above four feet long. Its- fcale extends from - 40 to
+ 224° of Fahrenheit, each degree being more than
•i;ths of an inch : when the barometer flood at 30 inches,
its boiling point was fixed in the tin veffel formerly de-
fcribed. Mr. ramsden’s thermometers generally rife in-
the fame veffel 21 3°f; and the long thermometer, being
placed in the veffel he makes ufe of to fix his boiling
points, rifes only to 2,10°.

The manometers were of various lengths, from four
to upwards of eight feet: they confifled of flraight tubes,

whole

,■}

-690 Col. roy’s Experiments for

whofe bores were commonly from T'-th to -Tth of an
inch in diameter. The capacity of the tube was care-
fully meafured, by making a column of quickfilver, about
three or four inches in length, move along it from one
end to the other. Thefe fpaces were feverally marked,
with a fine edged file, on the tubes ; and transferred from
them to long flips of paftc-board, for the fubfequent

conftrudlion of the fcales refpedlively belonging to each.

*

The bulb, attached to one end of the manometer at the
glafs houfe, was of the form of a pear, whofe point being
occafionally opened, dry or moifl: air could be readily ad-
mitted, and the bulb fealed again, without any fenfible
alteration in its capacity.

The air was confined by means of a column of quick-
filver, long or fhort, and with the bulb downwards or
upwards, according to the nature of the propofed expe-
riment. Here it muft be obferved that, from the adhe-
fion of the quickfilver to the tube, the inftrument will
not a<5t truly, except it be in a vertical pofition; and even
then-, it is neceflary to give it a fmall degree of motion,
to bring the quickfilver into its true place ; where it will
remain in equilibrio, between the exterior preflure of
the atmofphere on one fide, and the interior elaftic force
of the confined air on the other.

All

meafuring Heights with the Barometer. 691
All the experiments were made when the barometer
was at, or near, 30 inches. When the bulb was down-
wards, the height of the barometer at the time of obfer-
vation, augmented, and when upwards, diminifhed by
the number of inches of quickfilver in the tube of the
manometer, expreffed the denfity of the confined air.

Pounded ice and water were ufed to fix a freezing
point on the tube ; and by means of fait and ice, the air
was farther condenfed, generally four, and fometimes
five or fix degrees below zero. The thermometer and
manometer were then placed in the tin yeflel, among
water which was brought into violent ebullition ; where
having remained a fufficient time, and motion being
given to the manometer, a boiling point was marked
thereon. After this the fire was removed, and the gra-
dual defcents of the piece of quickfilver, correfponding
to every 20 degrees of change of temperature in the ther-
mometer, were fucceffively marked on a deal rod ap-
plied to the manometer. It is to be obferved, that both
inftruments, while in the water, were in circum fiances
perfectly fimilar; that is to fay, the ball and bulb were
at the bottom of the veffel.

In order to be certain that no air had efcaped by the
fide of the quickfilver during the operation, the mano-
meter was frequently placed a fecond time in melting
Vol. LXVII. 4 U

ice.

<5 9 a Col. roy’s Experiments for

ice. If the barometer had not altered between the be-
ginning and end of the experiment, the quicklilver al-
ways became ftationary at or near the fir ft mark. If any
fudden change had taken place in the weight of the at-
mofphere during that interval, the fame was noted, and
allowance made for it in afterwards proportioning the-
fpaces..

Long tubes, with bores truly cylindrical or of any
uniform figure, are fcarcely ever met with. Such how-
ever, as were ufed in thefe. experiments, generally tapered
in a pretty regular manner from one end to the other.
When the bulb was downwards, and the tube narrowed
that way, the column of quicklilver confining the air
lengthened in the lower half of the fcale, and aug-
mented the prefiure above the mean. In the upper half,
the column being fhortened, the preflure was diminifhed
below the mean. In this cafe, the obferved fpaces both
ways from the center, were diminifhed in the inverfe
ratio of the heights of the barometer at eachfpace, com-
pared with its mean height. If the bore widened to-
wards the bulb when downwards, the obferved fpaces,
each way from the center, were augmented in the fame
inverfe ratio; but in the experiments on air lefs denfe
than the atmofphere, the bulb being upwards, the fame
equation was applied with contrary ligns : and if any
& extra-

meafuring Heights with the Barometer. 693
extraordinary irregularity took place in the tube, the cor-
responding fpaces were proportioned both ways from
that point, whether high or low, that anfwered to the
mean.

The obferved and equated manometrical fpaces being
thus laid down on the pafte-board containing the mea-
fures of the tube; the 2 t 20 of the thermometer, in exadh
proportion to the fedtions of the bore, were conftrudted
along-fide of them : hence the coincidences with each
other were eafily feen; and the number of thermome-
trical degrees anfwering to each manometrical fp'ace,
readily transferred into a table prepared for the purpofe.

I have already had occalion to remark that, from the
operations of the barometer alone, an approximate rule,
or mean equation, had been obtained for the meafure-
ment of heights; but as, among the refults, irregularities
were now and then met with, doubts naturally arofe,
whether the equation, inftead of being considered as uni-
form, might not follow an increafing or diminishing pro-
gression? Without an infinite number of observations,
in very different temperatures above and below the zero
of the fcale, this point could not poffibly be determined
by the barometer : wherefore the firft and chief thing
propofed to be difcovered by the manometrical experi-
ments was, whether common air, occasionally rendered

4 U 2 more

694 Co/. roy’s Experiments for

more or lefs denfe, by the addition or fubtraCtion of
weight, expanded equally with quickfilver, when af-
fected with the fame degrees of heat? According to the
ratio that took place between the expaniion of quickfil-
ver and air, above and below zero, I intended to regulate
the barometrical equation already found, without re-
garding the proportion of the bulb to the bore of the
manometer; or in other words, without paying any at-
tention to the aCtual expanfion of the air confined in that
inftrument..

But after a great number of thefe firft experiments
had been made, it was judged proper to compute the
aCtual expanfion of 1000 equal parts of air in the ma-
nometer, from a heat of 2 1 20 ; wherefore, in the lalt, the
accurate capacity of the bulb, with refpect to the bore,
was determined ; at the fame time that the original mode
of comparing the thermometrical with the manometrical
fpaces, was ftill adhered to.

It is eafy to conceive in experiments of this very de-
licate nature, part of which, namely thofe on air lets
denfe than the atmofphere, were extremely difficult and
even laborious, that mathematical exactnels was not to be
looked for; and that, notwithftanding every poffible pre-
caution was taken, irregularities w'ould occur. Thefe,
however, were not fo numerous as might have been
i expeCled,,

meafuring Heights with the Barometer. 695:
expected, nor any way fo great as to render the refearch
fruitlefs : for a few of that kind being thrown out of the
total number, the mean of the others, which were very
confiftent among themfelves, ferved to prove beyond the
poffibility of doubt, that the expanfions of common air
did not keep pace with the dilatations of quickfilver.,
The manometrical fpace, anl'wering to the 20° of the
thermometer between 5 20 and 7 20, was always found to
be greater than any other 20° of the fcale. Here it is to-
be underftood, that I do not pretend to have afcertained
the exaft point in that fpace where the maximum falls :
the mean correfponds to the 6 ad degree, and yet I am
inclined to think that it is fomewhat lower, perhaps it
may be about the 57th: from this point, the condenfa-
tions of air downwards, and its expanfions upwards, fol-
low a diminilhing progreflion, compared with the con-
denfations and dilatations of quickfilver. The mano-
metrical are equal to the thermometrical fpaces, in two
points of the fcale; namely, at or near the freezing tem-
perature on one fide, and between the ua° and 13 ad
degrees of the fcale on the other. At the zero and boil-
ing point they are lefs than the thermometrical fpaces.
Whether this maximum of expanfion of air, compared ,
with that of quickfilver, be owing to moifture, or any

thing

>696 Col. roy’s Experiments for

thing elfe mixed with the former, which is brought into
its greateft degree of add ion, about the temperature of
570 of Fahrenheit, muft be left to the inveihgations
of future experimenters : I only relate things as I found
them after many repetitions, without being able to dif-
cover any material difference in the refults, even when
the air was rendered more or lefs denfe by an addition
to, or l'ubtradtion from, the weight wherewith it was
loaded. The thermometrical, compared with the mano-
metrical fpaces, will therefore appear as in the following
Sable,

Spaces

nteafuring Heights with the "Barometer . 697

Spaces of the quicldilver
thermometer, Fahren-
heit’s fcale.

Spaces of the manometer,
meafure! in degrees of
FAHRENHEIT,

r>

212

©

212

20

17.6

I92

20

194.4

l8.2

172

20

176.2

18.8

552

20

157-4.

19.4

I32 '
20;

138.0

20.0

112

1 18.0

2Cr

20.8*

92

20

97.2

21.6

72

20

75-&

22.6

52

20

53-0

21.6

32

2Q_-

3x*4

20.0

12

1 1.4

O'

a '

1 1.4

a '

698 Col. roy’s Experiments for

Experiments , for determining the actual expanjion of com-
mon air , in the manometer , affected by the heat of 2 1 20.

For this purpofe it became neceffary to afcertain, in
every manometer, the exaft proportion between the ca-
pacity of the tube and that of its bulb. This was done,
by weighing the quickfilver that filled them refpedlivelv,
in a balance that was fenfible to a very fmall fraction of
a grain. The contents of the bulb, and that part of the
tube between it and zero, exprefled in grains, wras called
the air in experiment. The apparent expanfion of that air
was meafured, by the grains that filled the feveral feftions
of the tube between zero and the boiling point ; the fum
being the total expanfion or increafe of volume, from a
heat of 2 1 20. The apparent expanfion, thus found, was
again augmented for the dilatation of the tube, on the
following principles.

In the firft part of this paper I have fhewn, that folid
glafs rods dilate much lefs than barometer tubes. The
mean betw'eenMr. smeaton’s and my experiments, gives
of an inch for the longitudinal extenfion of every
foot of thefe tubes, by 2 1 20. From the rate of going of
a clock, for near a year, whofe pendulum rod is folid
glafs, its dilatation feems to be one-third part of a fteel rod,

or

meafuring Heights with the Barometer. 699

or r-^oo on a f°ot> by ai2°. Now, as the manometers re-
ferable folid rods much more than they do barometer
tubes, it is probable their dilatation, even allowing for the
greater extenlion of the bulb, would not exceed -dL-ths of
an inch on a foot, or -j^th part on every two inches. In
this ratio I have therefore augmented the apparent, to
obtain the true, capacity of each manometer. The equa-
tion, amounting to about T~th part of the whole, being
lefs than the common error of fuch complicated obfer-
vations, might in fail have been entirely omitted, with-
out producing any material alteration in the refults.

Having, in this manner, computed the total increafed
volume of any number of equal parts of air (according
to the capacity of the bulb and tube in grains) and very
often likewife the partial expanlions for intermediate
temperatures, expreffed by the contents of the corref-
ponding fedtions of the tube, I then found the ratio
anfwering to 1000 equal parts, which, being divided by
the degrees of difference of temperature, gave the mean
rate for the whole fcale, or the particular rate for any
intermediate fedtion of it.

The experiments, confidered in this way, are diftributed
into four dalles, whereof the refults are comprehended
in the four following tables. The firft Ihews the expanlion
of air, whofe denlity was much greater than that of the

Vo l. LXVII. 4 X

common

7 oo Col. roy’s Experiments for

common atmolphere. The fecond, which is divided into
two fets, contains thofe on air that fuftained a preflure
lefs than the atmofphere. In the third clafs, a very fhort
column of quickfilver being employed to confine the
air, its denfity differed little from that we commonly
breathe in : this clafs is likewife fubdivided into two fets,
and it will hereafter be made ufe of to regulate the equa-
tion depending on the temperature of the air, in the ap-
plication of the barometer. The fourth and laft clafs of
experiments, were made on air of the common denfity,
artificially moiftened by the admiflion, fometimes of
fteam, and at others of water, into the bulb; it is accord-
ingly diftinguifhed into two fet9,

table i. Refults of experiments on the expanfion of air,
whofe mean denfity was equal to 2^ atmofpheres.

K°

Height of
the baro-
meter.

Inches of
quickfilver
confining
the air.

Denlity

in

inches.

Total expan-
fion of 1000
equal pans of
air by 2 1 z°.

Mean rate
for each
degree.

1

29.7

+72.

101.7

45*-54

2.12991

2

29.7

+62.6

92.3

423 23

1.99637

3

29.62

+50.84

80.46

412.09

1.94382

4

29.66

+24.88

54-54

439-87

2.07486

5

29.66

4- 20.05

49-7i

443-24

2.09075

Mean,

75-74

434.00

2.04717

T’ ABLE

table ir. Refults of experiments on the expansion of air of the denfity of five-fixths of the
common atmofphere; and of others on air that was extremely rare, being only prelfed with
about one-fifth of an atmofphere.

meafuring Heights with the Barometer. 703

table hi. Refults of experiments on the expanlion of
air of the denfity of the common atmofphere.

Nc

3

Firft fet; common

air. " 4

5

6

7

:econd fet; common <j ^
air heated red-hot 1 9

height
of the
barom.

Inches of
quickfilver
confining the
air.

Denfity

in

inches.

Total cxpanfion
of 1000 equal
parts of air by
ziz°.

Mean rate
for each
degree*

29.95

+ *•57

31-52

483.89

2.28250

30.07

+ 0.70

3°*77

482.IO

2.27406

29.48

•+0.42

29.90

480.74

2.26764

29.90

+ 0.83

3Q*73

485.86

2.29182

29.96

+ 0.96

30.92

4894s

2.30870

29.90

+ 0.65

3°-55

476.04

2.24547

29.95

+ 0.65

30.60

487-55

2.29976

3007

+ °-53

30.60

482 80

2.27736

29 48

+ 0 52

30.00

489.47

2.30871

Mean

30.62

484.21

2.28401

The total expanlion 484.21 being divided into parts
proportionable to the manometrical fpaces, meafured in
degrees of the quickfilver thermometer, as already given ;
we have the following expanlions for intermediate tem-
peratures, the rates for every 1 o° below 920 being found
by interpolation.

4X2

Ther-

*j 04 Col. roy’s Experiments for

! Thermo -
metrical
fpaces.

Manome-

trical

fpaces.

Total Expan-
nons for degrees
above zero,
1000 parts.

Difference
of expan-
fions, 1 000
parts.

Rate for each
degree, 1000
parts.

0

212*

0

2 1 2.

484.210

40.199

2.00995

l!92.

194.4

444.01 1

41-559

2.07795

172.

176.2

405.452

42.949

2.14745

152.

■157-4

359 5°3

44*310

2.21550

I32.

138.

3I5*I93

45.680

2.28400

1 12.

1 18.

269.513

47*5°7

2*37535

92.

97.2

222.006

24.21 1

2.42 1 10

82.

86.6

197*795

25.124

2.51240

72.

75-6

772.671

25.581

2.55810

62.

64.4

147.090

26.037

2.60370

52.

S3-

12 1.053

25.124

2.51240

42.

42.

95-929

24.21 1

2.421 10

32*

31 4

71.718

23-297

2.32970

22.

21.2

48.421

22.383

2.23830

12.

0.

1 1.4

226.038

26.038

2.16983

Hence2 2 2.oo6— 26.038= 195. 968 =2. 4496, ora. 45,
is the mean rate of expaniion for the 8o° comprehended
between 1 a0 and 920 of Fahrenheit.

TABLE

I 70s ]

-table iv. Remits of experiments on the expanfion of air, artificially moiftened, by the admiflion of Ream, and fometimes water, into the bulb

of the manometer.

N°

Height
of the
barom.

Inches oi
quickliver
confining
the air.

Denfity

in

inches.

Total expanfion
of 1000 equa
parts of air by

Mean rate
for each
degree.

Expanfion for intermediate temperatures.

from zero
to 320.

32°
to 520

52°
to 7 2°

72°

to 9 2°.

92°

to 112°.

112°
to 1320

*32°
to 152 .

1520
to 172°

I720

to 1920

I920
to 212°

r1

30.16

+ 1.6

3I-76

—

2.059375

2.60700

3.02650

3.38050

4.183OO

6.48000

8.67750

11.93600

16.85050

Firft fet: fleam ad- 2

29.97

+ 2.2

32.17

1409.04

6.64642

2.20250

2.59250

2.90950

3.67650

5.16700

6.9330°

10.17500

10.64200

16.57850

8.25400

roitted into the | 3

30.00

+ 2.2

32.20

1350.10

6.36840

2.26875

2.59100

3.04900

3- 7755°

4.369OO

7.60500

8 94400

10.42950

n.92200

1 1.69000

bulb before it was •{
fealed.

3°-43

+ 1.92

32-35

„

—

2.20875

2-5*450

2.74700

3-25500

3.73700

5-9*350

9 18950

11-5755°

25.88650

—

u

30.2

+ x.6

31.80

*999-7 1

9-43259

2.361875

2.51300

2.96400

3.84750

5.761OO

7.19450

12.29850

16.69750

19.29500

25-23550

(.6

30.32

+ 2.37

32.69

2576.16

12.15169

2.16250

2-5535°

3.11600

3.72300

5-53600

7.83900

I2.74IOO

16.74600

27-8435°

45.25000

Second fet: a drop of r 7

30.2

+ i-3

3i-5o

x 135.48

5.35604

2.22594

2.74450

2.90500

3-4775°

5.41 9CO

6. 1 6650

7.98850

8.58950

10.93600

4.98600

cold water admitted I g
into the bulb before J

30.06

+ 3.2

33-26

—

2.54062

2.63350

2.80850

3.78700

4.60750

Tube broken.

—

it was fealed. *- 9

3° 32

+ 1.6

31.92

- *538.3*

7.25618

2.02156

2.54250

3.22500

3.76500

5 41700

6.79250

9-14350

9.71100

*3-7555°

*9 9327°

Mean,

32.18

1668.13

7.86854

2.22799

2.58800

2.97228 .

3-63*94

4.91072

6.86550

9.89494

12.04087

17.88344

19.22470

Mean of the fecond, third, and feventh.

31.96

1298.20

6.12362

2.23239

2.64267

2-9545°

3-643*7

4.985OO

6.90150

9-03583

9.88700

I3-I4550

831000

Mean of the fifth, fixth,

and ninth, .

32-14

2038.06

9.61349

2.18198

2-53633

3-,0*67

3.77850

5-57*33

7-27533

**.39500

14.38483

20.29800

3°- *394°

By N° 1. the total expanfion for 192° is 1208.72, whence the mean rate is 6.29542.
4. — — 192° 1367.05, — — 7.12005.

8. — _ 1120 358.03, — — 3-19669;

From

I?

'

meafuring Heights with the Barometer . 707'

From the experiments of the firft clafs it appears, that
10 jo equal parts of common air, loaded with two at-
mofpheres and a half, being affected with a heat of 2 1 20,
expands 434 of thofe parts; that is to fay, in its dilated
ftate, it occupies a fpace bearing, to that which it origi-
nally filled, the proportion of 1434 to 1000 : hence the
mean rate of expanfion of air of that extraordinary den-
fity is 2.047 1 7 for each degree.

From the firft fet of the fecond clafs of experiments
it appears, that 1000 equal parts of air, prefled only with
|ths of an atmofphere, and buffering a heat of 21 20, ex-
pands nearly 484 of thofe parts, whereof the mean rate
for each degree is 2. 2 8 1 40 . The maximum correfponds
to that fedtion of the fcale between 5 20 and 7 20; and the
rate for the extremes is lefs than the mean.

But in the fecond fet of this clafs, when the confined
air was rendered fo extremely rare as to be prefled with
only one-fifth of an atmofphere, in which cafe there was
a neceflity for heating it red-hot before it was poflible
to make the quickfilver hang in any tube of a moderate
length, the expanfion of 1000 equal parts of air is, by
the feventh and eighth experiments, diminilhedfo about
two-thirds of the ufual quantity ; and by the ninth, it is
confiderably lefs, amounting only to .141.5 for the 1 8 o~
a. com--

708 Col. roy’s Experiments for

comprehended between freezing and boiling, or 0.7 8 6 1 3
for each degree. The maximum ftill correfponds to the
fpace between 520 and 720; and the minimum is con-
ftantly at the boiling point.

From thefe three laft experiments it would feem, that
the particles of air may be fo far removed from each
other, by the diminution of preflure, as to lofe a very
great part of their elaftic force ; fince, in the ninth ex-
periment, the heat of boiling water applied for an hour
together, could only make it occupy a fpace which, com-
pared with what it filled at freezing, bears the propor-
tion of 1 141.5 to 1000.

From the third clafs of experiments it appears, that
common air, prefled with a Angle atmofphere, whether
taken into the manometer in its natural ftate, or heated
red-hot therein, has the fame expanfion with air of only
five-fixths of that denfity: for 1000 equal parts of this
air expanded 484.21 from 2120 of heat, whereof the
mean rate is 2.28401 for each degree. By comparing
this refult with that of the firft clafs, and again with that
deduced from the fecond fet of the fecond clafs, it would
feem, that the elaftic force of common air is greater than
when its denfity is confiderably augmented or dimi-
niftxed by an addition to, or fubtraftion from, the weight

6 with

meafuring Heights with the Barometer. 709
with which it is loaded for, in the firft cafe, it bears
the proportion of 484 to 434; and in the laft, it is (from

the

(f) This difference between the elaftic force of common air, and that which
is artificially rendered more or lefs denfe, by the addition or fubtra&ion of
weight, particularly the latter, is truly remarkable, and contradi&s the expe-
rience of boyle, marriotte, &c. It could not arife from the adhefion of
the quickfilver to the tube, though in the denfe experiments a column of 72
inches was once made ufe of; becaufe the conftant motion given to the mano-
meter before the fpaces were marked, muft either have prevented any irregu-
larity whatever, or made the apparent expanfion fometimes too great, and at
others too little. But the rare experiments ferve to put this matter out of
doubt; for if the adhefion of the quickfilver to the tube had tended to leffen
the apparent expanfion of the air, beneath the truth in one cafe, it muft have
had a direft contrary effe£t in the other, and augmented it above the truth, ,
which it evidently doth not.

Thefe experiments on the expanfion of air lefs denfe than the atmofpliere,
were extremely difficult and troublefome; and it was not till after feveral
fruitlefs attempts that, with the afliftance of Dr. lind, an apparatus was pre-
pared for making them with fufficient accuracy. The vefiel employed for this
purpofe was made of the brafs tube of a large telefcope, near four inches in
diameter; it was divided into four pieces, which, when fcrewed together, made
a pot of fix feet in height. This was mounted on a platform laid over the
area rails, for the reception of the manometer, which was placed therein, with
the bulb uppermoft, the lower extremity of the tube palling through’ a focket at
the bottom of the vefiel, and then through a collar compofed of many thick -
neffis of flannel. By means of a brafs plate and three long ferews, the collar was
made to embrace the tube fo clofely, as to fuffer very little water to pafs: fuch as
did iflue, oozed off along the fides of a paper funnel, bound round the end of
the tube, without entering into the bore. In this pofition, it required fome degree
of force to pufti the manometer up, or draw it down, till the top of the quick-
filver confining the air, juft appeared without the collar, fo as to admit the
fpaces to be meafured, from a fixed point marked on the tube. The vefiel being
filled with boiling water, was kept to that temperature by means of lamps fui~

7'io Col. rov’s Experiments for

the mean of three experiments) as 484 to 252, when

prefied with only one-fifth of an atmofphere.

The

i pended around it. Two thermometers were made ufe of; the long one, whofc
ball flood at the bottom; and a fhort one at the top, that defcended no lower
than juft to be immerfed in the water. By fome of the firft of thefe experi-
ments, the lamps not being placed dire£lly at the bottom, water was perceived
to be a very bad conductor of heat; for it would boil violently at the top, and
the fhort thermometer there would mark 21 2°, while the long one would only
mark 185° or 190° at the bottom. By flow degrees the heat would neverthelcfs
defeend, and in the fpace of fifteen or twenty minutes the whole column would
become of the fame uniform temperature. But when the apparatus was adapted
for experiments on air denfer than the atmofphere, in which cafe a plate of tin
was foldered over the hole at the bottom, that it might be placed on a flrong
fire, the heat was then greatefl below, and the long thermometer wrould mark
upwards of 2150, while the fhort one flood at 209° or 210°. By defifling from
blowing the fire, or removing a part of it, the particles of water fullering the
greatefl heat would afeend, mix with the reft, and for fome little time make
the whole column of an uniform temperature. But the fire being totally
removed, the top of the column in cooling was always hotteft; wherefore, in all
thefe experiments, whether on denfe or rare air, great care wTas taken to mix the
water thoroughly.

From Mr. de luc’s book it appears, that M. amontons found the effe£l of
heat on the air confined in his thermometer, which feems to have been the fame
fort of inflrument with the manometer, proportionable to the weight with
which it was loaded. By this he could not mean that, being of a double den-
fity, it had twice the expanfion. I apprehend it mull here be underftood, that the
fpaces the air occupied, were inverfely as the weights. That being preffed with
a double weight, it only filled half the fpace; or with half the weight, a double
/pace. This is no doubt nearly, though not accurately, the law that it follows.
F rom thefe experiments it appears, that there is little difference in the a£lual ex-
panfion or elaftic force of air, preffed with an atmofphere -f- or — one- third part:
yet, when it is rendered extremely rare, its elafticity is wonderfully diminifhed.
*1 here feems likewife to be a vifible diminution in its expanfion, when loaded
with two atmofpheres and a half. Some of the tubes that I ufed were near nine

feet

meafuring Heights with the Barometer . 7 rt

The total expanlion 484.21 refulting from the third
clafs of experiments, which are very confident among
themfelves, being divided into parts proportionable to
the manometrical fpaces, as meafured in degrees of the
quickfilver thermometer, we have the expansions for in-
termediate temperatures, expreffed at the bottom of the
third table, where, it is to be obferved, the rates for every
io° below 9 20 were found by interpolation.

Now as barometrical obfervations will probably never
be made in a temperature higher than 920 in the Shade,
nor in one lower than 120, if we fubtradt 26.038, the
expanfion anfwering to 1 20, from 2 22.006, that which
correfponds to 92°, we Shall have 195.968 for the
80 intermediate degrees; or 2.45 for the mean rate
on each. This equation, compared with Mr. de luc's,
hears the proportion of 245 to 210, which is a difference
of y^qq'qq on every degree, or one-feventh part of the
whole : and though this rate will be found hereafter to

feet long. Had It been pofiible to have managed them of double or triple that
length, fo as to have admitted the air to be prefied with a column of 18 or 20
feet of quickfilver, I am perfuaded the diminution in the expanfion of air of
that extraordinary denfity would have been much more perceptible.

Mr. amontons found, that the condenfation of air in his thermometers
kept pace with that of fpirit of wine, which we are told follows a decreafing
progrefiion with refpe£l to quickfilver: wherefore his experiments agree wita
thefe, in making the condenfation of air below 570 follow a decreafing pro-
grefiion, when compared with that of quickfilver.

Vol. LXVIL 4 Y

exceed

7i2 Col. roy’s Experiments far

exceed that deduced from the operations of the barome-
ter in extreme temperatures; yet they agree exceedingly
well with each other for the mean heat of the air, when
the barometer will come moft frequently into ufe.

The fourth clafs of experiments are all that now re-
main to be mentioned. The bare infpedfion of table.
iv. will fhewr how greatly fuperior the elaftic force of
moift is to that of dry air. It is true indeed, that two
kinds of irregularities prefent themfelves among the re-
fults: firft, with regard to the total expanlion for 212’;
and fecondly, as to the greateft exertion of the elafiic
force, which fometimes feems to have taken place before
the air has acquired the heat of boiling water. The
firft is eafily accounted for : it muft have arifen from dif-
ferent proportions of moifture being admitted into the
fame quantity of air, which there was no pofiibility of
afeertaining, the bulbs and their apertures being of very
different dimenfions. With regard to the fecond irregu-
larity, I am rather inclined to think that it may have
proceeded from error of obfervation, it being difficult to
determine the accurate temperature near boiling; efpe-
cially when any part of the air rofe above the top of the
veffel, which was fometimes the cafe, notwithftanding its
extraordinary height. Be that as it may, a very uniform
encreafing progreffion will be perceived to take place,

from

meafuring Heights with the Barometer. 713
from the zero of Fahrenheit, as far as 1 5 20 or 172°;
and even to the boiling point, in thofe which I efteem the
heft experiments. By adhering to the mean refult it will
appear that air, however moift, having that moifture
condenfed or feparated from it by cold, its expanlion dif-
fers not fenlibly from that of dry air. Thus the rate for
320 below freezing 2.22799, is nearly the fame as in dry
air; but no fooner doth the moifture begin to diflblve
and mix with the air, by the addition of 20° of heat,
than the difference is perceptible : for inftead of 2.4667 5,
the rate for 20° above 320 in dry air, we have 2.588 for
that which is moift. In the next ftep of 20°, the rate for
dry air is 2.5809; whereas that for moift is 2.97. In
this manner the progreflion goes on continually encreaf-
ing, fo as to give 7.86854 for the mean rate on each de-
gree of the 2 1 20, which is near three times and a half
the expanlion of dry air. And laftly, the rate for the
20° between 1920 and 2120, is twice and one-half the
mean rate, and about nine times that which correfponds
to the zero of the fcale : but if the comparifon is drawn
from the mean of the fifth, fixth, and ninth experi-
ments, as being probably neareft the truth, the total ex-
panfion of moift, will be more than four times that
of dry air ; and the rate for the temperature at boiling,

4 Y 2 will

714 Col. roy’s Experiments for

will be nearly fifteen times that which correfponds to

the zero of Fahrenheit.

I am aware it will be alledged, that the proportion of
moifture admitted into the manometer in thefe experi-
ments, is greater than what can ever take place in nature ;
and therefore, in order to be able to judge of the degrees
of expanfion the medium buffers in its more or lefs denfe,
and more or lefs moift ftates, that not only air near the
furface of the earth, but likewife that found at the top of
fome very high mountain, fhould have been made ufe of.
I grant all this : but on the other hand it mult be remem-
bered, that thefe experiments are very recently finifhed;
that a good hygrometer (if fuch can ever be obtained)
a great deal of lcifure time, and the vicinity of high
mountains, were all neceffary for the carrying of fuch
a fcheme into execution. t

It is for thefe reafons, and in hopes that other people
will, fooner or later, inveftigate this matter ftill farther,
not only by experiments made on the expanfion of air,
taken at different heights above the level of the fea in
middle latitudes, but likewife on that appertaining to the
humid and dry regions of the atmofphere towards the
equator and poles, that I have been induced to haflen the
communication of this paper. In the mean time having
proved, beyond the poflibility of doubt, that a wonderful
2, difference-

meafuring Heights with the Barometer. 715,
difference doth exift between the elaftic force of dry and
raoift air, I may be allowed hereafter to reafon by ana-
logy, on the probable effects this will produce, in mea-
furing heights with the barometer ; leaving it to others,
much better qualified, to confider how far it will affeCt
aftronomical refractions. In the following feCtion I 111 all
therefore give an account of the barometrical obferva-
tions made in Britain, and compare them with fome:
others made in d iff ant countries.

SECTION III.

An account of the barometrical obfervations made in Bri-
tain, wherein they are compared with fome others of the
fame kind made in dijlant countries.

THE revival of the inquiries into that curious and
nfeful branch of philofophy, whereby vertical heights
are determined to a great degree of exaCtnefs, by the
preffure of the atmofphere alone, we owe to Mr. be luc ;
who hath undoubtedly removed many of the difficulties
that formerly occurred in the application of the barome-
ter, and thereby encouraged others to attempt to over-
come, fome part at ieaft, of fuch as remain.

77 'i f> Col. rov’s Experiments for

If the rule deduced from the obfervations on Saleve
•had been abfolutely free from exceptions, and if there
had not been particular points in the theory concerning
which the ingenious author himfelf leems to have enter-
tained doubts, it would probably have been univerfally
adopted, without undergoing any very fcrupulous invef-
tigation ; but the obfervations made at Sun-rifing on Sa-
leve, gave ref ults that were defective, or lefs than the
real height. In certain cafes, the equation for high tem-
peratures, remote from the zero of the fcale, appeared to
follow a diminiftiing, and in others an increafing pro-
gfeffion. Hence arofe fome caufes of uncertainty, with
refpeCt to the fpecific gravities of quickfllver and air, and
the relative expanfion of one compared with the other;
efpecially when the atmofphere happened to have more
or lefs moifture diffolved in it. It was doubtlefs from
confiderations of this fort, that Mr. de luc, in his book,
fo ftrongly recommends the making of numerous fets of
obfervations, in different countries; that, by the united
labours of all, this interefting part of natural philofophy,
might be brought ftill nearer to perfection.

With this general object in view, I am now to give an
account of the principal barometrical obfervations that
have been made in Britain, on heights determined geo-
metrically with great care. Thefe heights are claffed in

the

meafuring Heights with the Barometer. , 717

the following lift in fix fets, according to the diftrifts
of the country wherein they are fituated, and nearly in.
the order of time in which the obfervations were made..

Height in feet.

"St. Paul’s Church-yard (g), North-fide, and iron gallery "j R
over the dome, — • — - — J 2 1

Top of PaulVflairs, and the faid gallery, — 324

Top of Scotland -yard wharf, and the dining-room of]
the Spaniard on Hampfcead-heafh, - — J 422

Great Pulteney-flreet, and the faid dining-room, — - 352

Pagoda in Kew gardens, — ______ 1 i6|f

Gun wharf in Woolwich Warren, and uppermoft floryl
of Shooter’s- hill inn (b)y — — — — j 444-

(g) Mr. banks, affifted by other gentlemen, meafured very accurately with
a line the height of the ball of St. Paul’s above the floor of the church, which
was found to agree, exceedingly near, with that taken from the engraved fefllort
of the building. The diffance of the ball from the dining-room of the Spa-
niard, was found by a bafe meafured on Hampflead-heath ; and their relative
heights by the angle of depreffion of the ball, taken with the agronomical qua-
drant from the faid dining-room. The heights of Paul’s- flairs and Scotland-
yard wharf, with refpedl to each other, were found by meafuring from them
feverally to the furface of high water in the Thames. And the relative heights
of the church-yard and floor of the church with refpedl to the Labs, and ■ of
Pulteney-flreet with regard to the wharf, were obtained by levelling to them
refpe&ively.

(h) The height of Shooter’s-hill inn, above Woolwich, was found by a bale
meafured in the meadows from the Warren eaftward. Lord mulgrave, Mr. .
banks, and Dr. solander, aflifled in the geometrical operations; as did
Dr. blaqden, MelT. de luc and lloyd, in the barometrical obfervations.

N°

N° 1.

Heights in
and near ]
London.

”7-1 5 Col. roy’s Experiments for

N° 2.
tnear Tay-
-b ridge in
-Perthfhire.

Fccr.

^Station at the Eaft-gate of Caftle Mcnzie’s gardens 1 M t

near the village of Weem, and top of Weem Craig, j / w+

The faid ftation, ancl top of Bolfracks Cairn, — 1076*

The faid ftation, and top of Dull Craig, — 1244J

The faid ftation, and top of Knock farle, — 1364I

< The faid ftation, and that at the rivulet of Glenmore,! T

below the South obfervatory on Schihallien, — J /y+
The faid ftation, and South obfervatory, — — 2098

The faid ftation, and Weftcrn fummit of Schihallien, 3281
Station at the rivulet of Glenmore, and the South ob- 003
- fervatory, — — — — J 1 *

•near Lanark,

f Level of the Clyde at Lanark-bridgc, and ftation in 1
1 the garden at Lanark, — — J

J Ditto level, and top of Stonebyre hill, — —

j Robinhood's welJ, before Carmichael-houfe, and top\
of Tinto, four feet below the fummit of the Cairn, J
^Ditto well, and Weft end of Carmichael-hill, —

3621

654

16421

45Ji

N° 4.
near Edin-
burgh.

* Leith pier-head, and top of the Calton-hill, —

Leith pier, and fummit of Arthur’s Scat, — —

Leith pier, and Kirk-yetton Cairn, on the Eaft-end of
the Pentland hills, — — —

Calton hill, and ditto Cairn, — — • —

Level of Hawk-hill ftudy, and top of Arthur Seat,
Hawk-hill obfervatory, and bottom of the little rock
on Arthur Seat, feet below the fummit, —
-Hawk-hill garden-door, and ditto little reck, —

344

803

1544

I2CO

702j

684

73°+

N° 5.

near Lin-
houfe.

'Linhoufe, and Eaft Cairn-hill, 5 feet below the fummit,
Ditto, 1 8 feet below the top, — —

Linhoufe, and Weft Cairn-hill, 1 1 feet below the top,

' Ditto, and Corftown hill, 4 feet below the top, —
Corftown-hill, and Weft Cairn-hill, — — -

Ditto, and Eaft Cairn-hill, — — —

1 x76£

uySI

386i

N* 6.

near Carnar-
von in North
Wales.

} Carnarvon Quay, and Snowdon Peak,
Ditto, and fummit of Moel Eilio,

To enter into a minute detail of the geometrical ope-
rations, whereby the whole of thefe vertical heights

were

tneafuring Heights zvrtb the Barometer. 7 \ 9
were determined, would be extremely tedious and unin-
terefting. That fome idea may however be formed of
the degree of accuracy with which they were afcertained,
it will be fufficient to obferve, that the requifite angles
were taken with an aftronomical quadrant of a foot ra-
dius, made by Mr. sisson, and curioufly adapted for the
meafurement of horizontal or bale angles; which, as well
as thofe of the vertical kind, might always be determined
thereby to within ten feconds of the truth. The bafes
were meafured with care ; and, in order to afcertain the
diftances, the three angles of each triangle were, as
often as poffible, actually obferved with the quadrant.
That the variation of the line of collimation of the in*
ftrument, which was found to alter in carrying, might
occalion no error, one or more of the angles of elevation,
at each ftation, were taken on the arc of excefs, as well as
on the quadrantal arc. I11 all cafes, the ufual <,) allow-
ances were made for curvature and refraction : and for
the correction of the la ft, fometimes the angles of de-

(1) If the fquare of the diflance be divided by the diameter of the earth, the
quotient will give the curvature of the globe on that diflance, or the excefs of
the apparent above the true level : and, by Mr. maskelyne’s rule, the fquare of
the diflance being divided by the diameter of the earth, augmented by one-
fourth part, we have the allowance for curvature and refraction; which laft is
fuppofed to raife the objeCt, by an angle equal to that of a great circle fubtended
by one-tenth part of the diflance.

4Z

VOL. LX VII.

preffion

, io Col. roy’s Experiments for

preffion as well as of elevation were taken. When time
would permit, the geometrical operations were repeated
at the firft ftations ; or the angles of elevation were ob-
ferved from fome new point connefted with the firft,
and whofe relative height, with refpect to the others, was
known. Small altitudes were occafionallv determined by
levelling from one ftation to the other.

To prove that the vertical heights, aftigned to the places
in the preceding lift, are exceedingly near the truth, I need,
only mention the following inllances, by way of confirma-
tion. In 1771, with the afliftance of Dr. lind and his
friend Mr. hoy, I meafured a bafe from the obfervatory
of Hawk-hill weftward, whereby the height of the fum-
mit of Arthur’s Seat, above the telefcope of the Hawk--
hill quadrant, in its horizontal pofition, was found to be
685.66 feet. In 1775, thefe gentlemen levelled, three
feveral times, from the fummit downwards to the laid-
telefcope; and found the- vertical diftance to be, by the
firft operation, 686.47 feet; by the fecond, 684.43;
and by the third, 685.25. This 1 aft, which, from the
great care that was ufed, they confidered as the beft, dif-
fers only three-tenths of a foot from the geometrical re-
fult. They afterwards continued the operation of level-
ling from Hawk-hill to the pier of Leith, and having
repeated it twice, with a difference of only two inches

between

tmafuring Heights with the Barometer. 721
between the refults, they found the mean defcent to be
117.38 feet : hence Arthur’s Seat is above Leith pier, by
the mode of levelling, 802.66 ; and by the mixed me-
thod 803 feet.

In 1774, when the aftronomer-royal was carrying on
the Society’s experiments for afccrtaining the attraction
of Schihallien, I found, from my own geometrical opera-
tions, depending on a bafe meafured in the plain near
Tay bridge, the Weltern fummit of the mountain to be
1 1 83 feet above the South obfervatory.

Of this height, the effeCt of curvature and refraCtion
amounted to 28.86 feet, on the diftance of Bolfracks
Cairn from the obfervatory; and to 38 feet, on the dif-
tance of the faid Cairn from the fummit of Schihallien.

The refult of thefe operations I communicated to Mr.
maskelyne, before his trigonometrical operations were

begun. From the data which he hath fince been fo
obliging as to furnifh me with, depending on the bale m
Glen more at the bottom of Schihallien, and the angles
of elevation taken from the Southern extremity of that
bafe, the Weftern fummit of the mountain is t 186.6
feet above the South obfervatory. But if the triangle
that ferved to connect the itation of the barometer in
that valley with the others, and the angles of elevation
taken from the lame Itation are made ufe of, the aif-

4 Z 2

:erence

722 Col. roy’s Experiments for

ference of height will be 1183.33 feet. Laftly, Mr.
maskelyne’s refult, from the triangles on the North-fide
of the mountain, makes it 1180. The mean of thefe
three 1183.31 feet, is the height of the Weftern fummit
of the mountain above the South obfervatory, which only
exceeds my height by one-third of a foot. Here it is to
be obferved, that from the vicinity of thefe triangles to
the mountain, and the fhortnefs of the fxdes, the greateft
curvature amounted only to 1 6 or 1 7 inches, which con-
fequently made the effedt of refradtion next to nothing.
This near agreement between the refults feems there-
fore to prove, that the mode of computation for curva-
ture and refradtion, made ufe of in the Tay bridge obfer-
vations, is juft.

By the firft angles of elevation, taken from the ftation
of the barometer in Glenmore, the Weftern lummit of
Schihallien is 2001.88 feet above it; from which, if we
dedudt 1 1 83.33, there remains 815.55 for the height of
the South obfervatory above the faid ftation : but if the
laft angles of elevation at the ftation of the barometer
are made ufe of, the height between it and the obferva-
tory comes out 818.97, whereof the mean is 818.76
feet. Though thefe inftances are of themfelves fuffi-
cient to prove, that the geometrical heights may be fafely
depended upon ; yet, as an example of the method that

was

measuring Heights with the Barometer . 723'

was always made ufe of, I fhall annex to this paper, a
plan of the triangles and detail of the operations for ob-
taining the height of Snowdon; becaufe that mountain,
at the fame time that it is the higheft I have meafured,
is, from its fituation, more likely to be vifited, and to
have experiments repeated upon it, than the remote hills
of the North. I now proceed to give fome account of
the barometrical obfervations.

The heights in and near London being fo very incon-
fiderable, it was eafily forefeen, that nothing conclufive
could be drawn from obfervations made on them alone.
It was, however, natural enough to try, even on thefe,,
whether the rule we had been furnifhed with would an-
fwer? A fmall height of 41 feet 4 inches, which, with-
out inconveniencv, could be recurred to at all times of
the day, and all feafons of the year,, was the firft that
%vas made ufe of. St. Paul’s, Hampftead, Kew pagoda,
and Shooter’s-hill, were the next. The mean refults of
many obfervations on the three firft, and of feveral on
Shooter’s-hill, were found to be defective. In general
the coldeft obfervations, made in the morning and even-
ing, when the temperatures at the two ftations differed,
lead from each other, anfwered bed. In the hotted part
of the day, when that difference was the greated, the
refults were nioft defective.

Some

724 Co/. roy’s Experiments for

Some months fpent in Scotland in the dimmer of
1774, afforded opportunities of makihg barometrical ob-
fervations on hills of various heights, from three or four
hundred, to upwards of three tlioufand feet, as hath been
exhibited in the preceding lift. That feafon was re-
markably cold and wet; wherefore, in thel'e obfervations,
the mean temperature of the air in the fliade was com-
monly about 550. The hotted never exceeded 63° in
the plain; and the coldeft, namely thofe on the highelt
mountains, were generally from 430 to 48°.

From the defect found in the refults of thefe obferva-
tions, which, with refpect to temperature, correfpond to
the mean and hotted of thofe made at Sun-riling on Sa-
leve, and without any exception whatever, I could ealily
difcover, either that a much greater equation than what
the rule directed, mud be applied for each degree of heat
above the zero of the fcale; or, that the zero itfelf would
fall con fiderably dower than 39°74, where Mr. de luc's
formula, adapted to Englifh meafures, hath fixed it.
This fil'd dep towards a correction of the rule, naturally
pointed out the fecond thing to be aimed at, namely, the
obtaining of a fufficient number of cold obfervations,
near the zero, and as far as poffible below it, that the
equation might difappear entirely, and even come to be
applied with the contrary fign. Of this kind the winter

leafons

1

meafuring Heights with the Barometer. 725.
feafons of 1774 and 1775 afforded a few on the frnall
heights in and near the metropolis; but the bell I have,
been furnifhed with are thofe which Dr. lind, a flitted
by Mr. hoy, was fo obliging as to make on Arthur’s Seat
near Edinburgh ; and thofe which Captain calderwood.
has fi nee favoured me with on the Cairn-hills, being a.
part of the Pentland range to the South-wett of that city.

By comparing thefe fets of obfervations together, it
appeared from all of them, that when the air was at or
near the freezing temperature, the logarithmic differ-
ences gave the real height, in Englifh fathoms and thou-
fandth parts, without any equation; and when confidera-
bly below that point, the equation was to be fubtradfed, or
applied with the fign - inftead of + . It was farther per-
ceived, that the fame general conclufion might be drawn
from the coldeft, not only of the Sun-rifing, but even
of the ordinary obfervations on Saleve, fome reduction of
the temperature being in certain cafes made, on account
of the expofure of the thermometer to the Sun’s rays :
hence I was led to fuppofe, that the morning obferva-
tions, inftead of being made exceptions from the rule, ,
were thofe, which, it might be prefumed, would form
the belt bafis for deducing the equation depending on
the heat of the air; becaufe the mean temperature of the
column was then found to differ leaft from that of its

ext re-

726 Col. roy’s Experiments for

extremities; whereas in thehotteft time of the day, that
difference was generally the greatefl.

Having been enabled, by means of the cold obferva-
tions, to form fome judgement whereabout the zero of
the fcale would fall, below which the equation was nega-
tive, and above it affirmative; it followed of courfe, that
the next principal thing to be fought for, was the maxi-
mum of equation, or that correl'ponding to the higheft
temperatures the climate of our ifland would afford. It
was partly with the view of obtaining thel'e that I went,
injuly 1775, to Snowdon in North Wales. On this expe-
dition Captain calderwood was fo obliging as to accom-
pany me, and lend me his affiffance in the operations for
determining the geometrical height of that remarkable
mountain. At that particular period, the weather proved
unfavourable for obtaining hot barometrical obferva-
tions ; but, in other refpedts, they were very fatisfadtory,
as being in general conliftent among themfelves, and
agreeing fufficiently near with thofe of the preceding
year in Scotland ; at the fame time that they were made
on a height, as formerly mentioned, greater than any
■other hitherto meafured, with equal care, in Britain.
During the fummer of 1776, Dr. lind obtained fome
more hot obfervations on Arthur’s Seat ; and in the begin-
ning of the following winter, Captain calderwood
5 made

meafurlng Heights •with the Barometer . 727

made others of the cold kind, on the Cairn-hills in his
neighbourhood. From the combination of the whole of
thefe obfervations taken together, and a comparifon of
them with Mr. de luc’s, as far as they are fimilar, I
mean to drew the agreement or otherwife, between the
equation for the heat of the air, as deduced from the ba-
rometer and manometer; but lince the Britifli obferva-
tions, in certain cafes, differ confiderably in their circum-
ftances from thofe on Saleve, it is necefiary, in the firft
place, to point out wherein this difference chiefly con-
flfts.

In the obfervations in Britain, the barometers and de-
tached thermometers have been,almoft conftantly, placed
in the open air in the fhade, and fuffered to remain there
generally half an hour, and fometimes a great deal
longer, before the correfponding obfervations were be-
gun, that the quickfilver might have time to take the
temperatures of the fituations refpedtively . They were
then obferved four times, ufually at intervals of ten mi-
nutes, the mean of the four being that which is calcu-
lated, and called a Angle obfervation. If the time did not
admit of fb long an interval, the fame number of obfer-
vations were taken at diftances of five minutes from each
other. In either cafe, the extremes never differed above
a few thoufandth parts of an inch from the mean, fo as to

Vol. LXVII. 5 A render

728 Col. roy’s Experiments for

render the computations of them feparately wholly un-

neceffary.

Except in very fmall heights, and chiefly in London,
where it was impoflible to fcreen the upper barometer fo
effectually from the Sun during the time of obfervation
as that below, which generally flood in the fhade of fome
building, the temperature of the quickfilver in the fu-
perior ll:J hath been colder than that in the inferior baro-
meter. The difference was commonly found to be two
or three degrees; fometimes it would amount to fix
or feven; rarely, in heights that were confiderable, to
nine or ten; and in one inflance only to thirteen, where
the vertical diftance of the inftruments was great.

Whether in the plain or on the tops of the higheft
mountains, the detached thermometers, indicating the
temperature of the air, have generally flood fomething

( k) I have fometiaies found, particularly in -frofty. weather, that a thermo-
meter placed on the pavement of the North-fide of St. Paul’s Church-yard,
elofe to the wall of the. building, would Hand two degrees lower than that which!
was expofed on the North-fide of the iron gallery over the dome. The firft, no
doubt, felt the cold produced by the evaporation from the fiones, while that
above might be affefted by the afcending fmoke. But the moft remarkable,
balance °f this kind. occurs in one. of Dr-, lino’s obfervations, on the breaking
up of the hard froft January 31, 1776: at Hawk-hill, at ioh 45" A.M. the
temperature of the open air was 14°, while that at the fummit of Arthur’s Seat
was 20°. The frpft that remained in the ground kept the air extremely cold,
below, though it had already felt the effefls of the thaw at the top of the
mountain.

lower

tneafuring Heights zvith the Barometer. 729
lower than thofe attached to their refpedtive barometers,
until they had remained a confiderable time in the fame
fituation, equally lhaded from the Sun, when they always
agreed: whence it followed, that in thefe obfervations,
the mean temperature of the air, and equation depending
upon it, might always have been determined very near
the truth, from the temperature of the quickfilver in the
tubes, as fhewn by the attached thermometers, without
ever confulting the detached ones. Let us now fee what
were the circumftances attending the obfervations on
Saleve.

Mr. de luc’s lowermoft barometer flood in the
ground-ftory of a houfe near Geneva, where it remained
unaltered during the whole of his experiments ; while
the detached thermometer, indicating the temperature
of the air, was expofed on a fmall eminence, at a little
diftance, directly to the Sun’s rays : hence we find that, in
the obfervations of high temperatures, the bottom of the
column of air is often 1 a° or 1 50, and in one cafe x 8°,
hotter than the quickfilver in the tube. And even in the
loweft temperatures, the bottom of the column of air is
generally hotter than the quickfilver within doors, con-
trary to common experience in this country: for in Eng-
land, in winter, the exterior air in the lhade is always
colder than the interior air. This circumfiance gives

rcafaa

5 A 2

7 ^0 Col. roy’s Experiments for

reafon to apprehend, that the thermometer fuffcred not

only diredl but reflected heat.

The fuperior barometer was fhaded with a parafol
from the Sun, while its correfponding detached thermo-
meter was expofed to his rays : wherefore, in the obfer-
vations of high temperatures, the top of the column of
air is ufually four or five degrees hotter than the quick-
iilver in the barometer Handing in the fame air; and the
mean heat of the column often exceeds very confidcra-
bly the mean heat of the quickfilver in the tubes.

In many of the coldeft of Mr. de luc’s obfervations,
as well as in thofe of mean temperatures of about 50° or
550, the fuperior barometer is often the liotteft of the
two, even when the furrounding atmofphere at the top is
colder than at the bottom. This circumftance is ealily
accounted for: Wood is known to be a bad conduc-
tor of heat, to receive it flowly, and retain it long : that
barometer, which was moved about from place to place
upon the mountain, with a very fhort interval between
the obfervations (as is fufficiently evident from the great
number of ftations it pafled through in a limited time)
mufi have acquired and retained heat fuperior to that of
the atmofphere, and communicated it to the tube with
which it was in contadl. Some difference would no
doubt arife from this caufe, if the temperatures of the

quickfilver

meafuring Heights with the Barometer. 731
quickfilver in the tube and attached thermometer did not
keep exactly pace with each other.

The laid point to be mentioned is {till more remarka-
ble tha the reft ; it is briefly this : in the obfervations at
Sun-ri ing on Saleve, though the fuperior quickfilver is
the cold eft; yet the top of the column of air is commonly
five or fix, arid fometimes eight or nine degrees, warmer
than the bottom.

Having thus fhewn the fteps that were taken, for ob-
taining the coldeft and hotteft barometrical obfervations
that the climate of this ifland would afford, the mode of
obferving, and wherein the circumftances attending them
differed from thofe on Saleve, I fliall now point out the
general refult. In order to avoid repetitions as much
as poffible, it is neceffary, once for all, to remark, that
the computations of the Britifh obfervations, by the rule
hereafter to be given, are fubdivided into their refpefilive
claffes. Each table contains 1 5 columns, which their"
titles fufficiently explain, that the principles from which
the rule was deduced, the refult and error, might all ap-
pear in one view. The laft column towards the right-
hand fhews the ratio of the weight of quickfilver to air,
the columns of the firft in the barometers being feve—
rally reduced to the mean temperature of the laft.

2

By

73 - Col. roy’s Experiments for

By comparing the tables it will be found, that the ob-
fervations for extreme temperatures belong to the Edin-
burgh clafs of obfervations (N° 4.) it being thought belt,
in this cafe, to omit the few hot ones obtained on the in-
confiderable heights near London : the mean of the
coldeft, anfwering to the temperature of 2 1°.7 5, make
the logarithmic excefs and the mean of the hotteft,
correfponding to the temperature of 69°. 6, give adefedt
of tw* Now the fum of the two equations being di-

vided by the difference of temperature 47°.85, we have
nearly 2.3 for the mean rate of the equation on each
degree, which is lefs than that refulting from the opera-
tions of the manometer. Again, from the mean of the
very beft obfervations, as being made on the greateft
heights, ivhen the temperature of the air is 520, it ap-
pears, that the defeat is from — - \ or 2. t for each
degree nearly, which agrees perfectly well with the ma-
nometrical expanfion. In this cafe, the ratio of the
weight of quickfilver to air is as 1 1 3 7 7 to 1 ; greater very
confiderably than 1 1 232 to 1, affigned to them by Mr.
de luc, when the temperature is 69°. 3 2, anfwering to
the zero of his fcale, without any allo wance for the di-
minution of preffure on his columns, which llioi Id have
rendered air ftill comparatively lighter. From the Bri-
tifh obfervations, made on the moft confiderable heights,

it

1

measuring Heights with the Barometer. 733
it appears, that when the temperature of the air is 2 8°. 2,
the ratio of its weight, with refpeft to that of quickfil-
ver, is as 1 to 10552: hence the increafe of the weight
of air, on every degree of difference of temperature be-
tween 2-8°. 2 and 5 2°. 5, amounts to 34.4; and hence we
have 5 20.5-4°.2=4&°.3 for the temperature of the air
in Britain, when its weight would be rn-jr of that of
quickfilver ; and confequently agree with Mr. de lug’s,
though the heat would differ from his 210. It will no
doubt be remarked, that the equation for the air, refult-
ing from the operations of the barometer, falls fhort of
that given by the manometer. Part of the difference, I
apprehend, may arife from the fmall number of baro-
metrical obfervations obtained in- extreme temperatures.,
I fhall, neverthelefs, adduce reafons hereafter for hippo-
ling, that it really fhould diminifh, becaufe of the drier
and lefs elaitic flate of the fuperior air, compared with
that taken into the manometer at the earth’s furface. In
the mean time, fihce both inftruments agree in the equa-
tion for 5 20, which is a heat that the barometer will very
frequently be ufed in, itfeems beft to adhere to the mean
manometrical refult 2.45, in fixing the zero of the fc'alej,
which is obtained in the following manner.

Divide the excefs or defect, expreffed in x oooth parts'
of the logarithmic refult, by 2.45, the mean expanfion or

air;

734 -Co/, roy’s Experiments for

air for each degree of the thermometer ; the quotient
will give the number of degrees, in the firft cafe, to be
added to, and in the laft fubtradted from, the tempera-
ture of the air in the observation ; the fum or difference
anfwers to the zero of the fcale, or that temperature
when the logarithmic refult gives the real height in
Englilh fathoms and 1000th parts.

According to this mode of computation, we have,
from the aggregate of the feveral clafles of Britilh ob-
servations, the place of the zero as follows :

Zero,

By the i ft clafs of obfervations in and near London,
between the temperatures of — —

2d, near Taybridge, — —

3d, near Lanark, — —

4th, near Edinburgh, — —

5th, near Linhoufe, — —

6 th, near Carnarvon, — —

25.5 and 71.2 at 32.2

46.1 — 62.9 - 31,1

44. — 62. - 32.8

x7« — 7°*7 “ 3l 3

26.1 — 46.5 - 29.9

49.1 — 62.3 - 32 9

Mean place of the zero at

3'-7

The number 3i°.7 differing fo very little from 3 2°,
we may hereafter confider that remarkable point of fah-
renheit’s thermometer, as the zero of the fcale depend-
ing on the temperature of the air; and hence is deduced
the fecond part, of the rule for meafuring heights with
the barometer. When the mean temperature of the co-
lumn of air to be meafured is at 3 1° of Fahrenheit, the

difference

■ fneafuring Heights "doitb the Barometer. 735
difference of the common logarithms of the equated
heights of quickfilver in the inferior and fuperior baro-
meters, expreffed in 1 o o oth parts of an inch, gives the real
height in fathoms and 1 oooth parts, the three figures
towards the right-hand being decimals, and the reft in-
tegers; which, being multiplied by fix, gives the refult
in feet.

Let us next confider, in a general way, how far this
will correfpond, or otherwife, with Mr. de luc’s obfer-
vations in extreme temperatures.

I have already had occafion to remark, that when the
temperature of the air was at 69°. 3 2, as indicated by
thermometers expofed to the Sun’s rays, Mr. de luc
found that the differences of the common logarithms of
the heights of the barometers at the two ftations, gave the
altitude between them, in French toifes and 1 oooth
parts : in which cafe the fpecific gravity of quickfilver to
air was as 1123a to 1. When his formula is adapted to
Englifh meafures, the zero of the fcaie necefiarily de-
fcends to 39.74, where the Englifh fathom bears the
fame proportion to the modulus of the common loga-
rithms, as, in the former cafe, the French toife did to char
modulus, the equation for the intermediate tempers a -
being now applied with the contrary fign. As it i r
been fhewn, that the Britifh obfervat ions differ in their
Vol. LXVII. 5 B

circum

736 Col. roy’s Experiments for

circumftances from thofe on Saleve, and require a greater
equation, it is unneceffary to enter into any minute com-
parifon of the two fets : neverthelefs, that fome idea may
he formed of the caufe, of part at leaft, of the difference
that takes place between them, I have colle&ed into one
view, the computations of fuch as were made in extreme
temperatures ; namely, the coldeft of thofe at Sun-riling
(though the whole of that clafs were conlidered as ex-
ceptions from the rule) the coldeft and hotteft of the
ordinary obfervations ; alfo thofe on the Doler/', at Genoa,
and at Turin, whereby the heights of the lake of Ge-
neva and of Turin, above the fea at Genoa, were ob-
tained. In the table it will be obferved, that there is a
column for the reduced temperature of the air, on ac-
count of the expolition of the thermometer to the Sun’s

(!) Having recomputed the whole of Mr. de luc’s obfervations on Saleve,
and claffed them according to the months in which they were made, I intended,
at one time, to have given a general table, comprehending the mean refults of
all of them : however, this is now become unneceffary, fince a very refpe£lable
and ingenious member of this Society hath had opportunities of making many
curious and interefting obfervations on thofe very heights, which cannot fail of
being perfectly fatisfa£lory ; and who, * at my requeft, was fo obliging as to
determine the height of the Dole geometrically. On this mountain Mr. de luc
had made barometrical obfervations, whofe refults differing confiderably from
the altitude, 4182 feet above the lake of Geneva, as taken by Mr. fatio de
duillier, made me fufpeft there was an error. In fa£t it appears, from the
laft meafurement, that the fummit of the Dole is 4293 feet above the furface of
the lake, which gives for the vertical diftance of Mr. de luc’s barometer
4210 feet,

rays::

meafuring Heights with the Barometer. 737
rays : I apprehend that I have not exceeded, hut rather
fallen fhort, in the reduction, to what would have been
indicated by thermometers in the fhade, perfectly free
from direft and reflected heat, and with fufficient time
allowed between the obfervations. Be this as it may, it
is of no importance, as no other conclufion is drawn
from thefe obfervations, than that of Brewing what, in
my apprehenfion, might probably have been the cafe, it
another mode had been adopted.

From the table it appears, that when the temperature
of the air is at 290. 5, the logarithmic excefs is ~o5 and
at 7 50. 5 reduced temperature, the defect is The

-fum of the twro equations ™V being divided by the dif-
ference of temperature 46°, we have, as in the Britifh
obfervations, nearly 2.3 for each degree-, which is greater
than that applied by Mr. de luc’s rule, in the proportion
of 2 3 to 2 1 . That too fmall an equation hath been made
ufe of in thefe hotteft obfervations, fuppofing the origi-
nal zero and temperature to remain, is fufficiently evi-
dent: for being divided by 420 the difference of
temperature, we have, as before, 2.3 very nearly for the
equation anfwering to each degree.

Farther, if we confider the ratio of the weight of
quickfilver to air, actually refulting from the obferva-
tions themfelves, the fame kind of error (for I cannot fee

5 B 2 lt

738 Col. roy’s Experiments for

it in any other light) ftill exifts. Thus, in the coldeft of
the morning, as well as in the ordinary obfervations, when
the temperature is at or near freezing, the mean ratio of
the weight of quickfilver to air, is about 10850 to 1.
When the obferved and reduced temperatures are re-
fpeftively 41 0 and 3 5 °, the ratio between them is that
of 1 1 295 to 1, anfwering nearly to what hath been af-
figned to them when the heat is 69°. 3 2. Again,
in the hotteffc obfervations of the 14th and 15th of
July 1759, and 20th of July 1760, on the higheft,
and confequently the bell ftations, when the obferved
and reduced temperatures are refpeftively 8i°.7 and
7 5°. 6, quickfilver is to air as 12650 to 1. Now if we
reduce this number 1 2 6 5 o by a proportionable part, for
the degrees of difference between Mr. de luc’s zero
6 90. 3 2, and the obferved and reduced temperatures re-
fpeftively, we fhall have, in the firft cafe, 12200; and
in the laft, 1-2390 to 1, for the ratio of the weight of
quickfilver to air; either of which exceeds very confi-
derably 11232, which hath been affigned to them.

With regard to the obfervations on the Dole, the de-
left is anfwering to the obferved temperature of'
66°. 6, and which is only reduced to 65°. 2. On this
great height, the ratio of the weight of quickfilver to

j meafuring Heights with the Barometer . 739

air^ is that 0f 12595 to 1. Mr. de la caille’s obfer-
vations at the Cape of Good Hope, annexed to the table
containing Mr. de luc’s, give a defeat of when the
temperature feems to have been about 5 8°, in which cafe
quick lilver was 11687 times heavier than air.

Now if, from the aggregate of thefe obfervations, the
fame method be adopted, as was made ufe of in the Bri-
tifh, for finding the zero of the fcale, we ftiall have it as
follows : .

By the manometrical equation
and reduced temperature.

O o O

from 25.2 to 30.5 at 33.12

— - 26. - 35. - 32'9?

— 73-5 ~ 77- " 36-32

— 58. - jo. - 32.

75- - 79- 3340

- — 58. ~ 33*33

Zero at 3 3- 5 2

(m) It will even be found, though the calculations are not inferted in the
table, that the hotted; of Mr. de luc’s morning obfervations, June 8th, 1758, at
the 15th ftation, anfwering to the mean temperature of 57°*5? anc^ which L
conftder as the beft, becaufe no redu£lion is neceftary for the expolition of the
thermometer, agree with the manometrical experiments, in requiring a greater
equation than is wanted in extreme temperatures: for in this cafe, ... tne*

mean of two obfervations gives a defe£l of for 25°»5 above freezing, which.

is 2.57 for each degree the ratio of the weight of quickfilver to air being that
of 12196 to 1 «

By Mr. de luc’s equation for the air and
obferved temperature.

Coldeft of the morn- 0 0 0

ing obfervations, > 25.2 to 30.5 at 33.7
from - — d

Coldeft of the ordi-J . T ^ „

nary obfervations, j 4 *9 o *7

Hotteft of the ordi- 1 , o . - ^ «

nary obfervations, j 7 4*5 3. »•

On the Dole, — 59.2 - 71.5 - 27.6

Light houfe of Genoa, 75. - 79. - 26.

DE LA caille’s, 58. - 30.

Zero at

32-°3

From

74© Col. roy’s Experiments for

From the mean of tliefe obfervations, though the re-
fults are irregular among themfelves, it appears fufli-
ciently evident, that if the morning obfervations on Sa-
leve had been retained, inftead of being made exceptions
from the rule, the zero of the fcale would have de-
pended about 8°; viz. from 69°. 3 to 6i°-4 of Fahren-
heit, fuppoling always the equation 2.1 for each degree
of temperature, and the French toife, as the ftandard
meafure, to have been adhered to : for the French toife
hears to the Englilh fathom, the proportion of 106575
to 100000 ; wherefore -Ail i_=ii^2= 29°.4+32°= 69°.4,
^denotes the relative pofitions of the two zeros, the inter-
mediate equation (>C— being to be fubtradled, when the
toife is made ufe of. But it hath been fhewn, that the
mean expanlion of air is really greater, for fuch tempe-
ratures at lead; as the barometer can be applied in, than
what Mr. de luc fuppofed it, in the proportion of 245 to
210; whence it follows, that ^=2 5°.i 8 + 32°= 57°. 18,
will denote the relative politions of the two zeros ; which,
inftead of almolt 30°, are only diftant from each other a
little more than 25°.

From what hath been Paid it is eafy to fee, that in cal-
culating heights according to Mr. de luc’s rule, when
the temperature of the air is below his zero, which we

may

meafuring Heights with the Barometer. 741;
may take at 40°, the Englifh meafure being ufed, the
common error in the refult will be equal to the fum of
the two equations, 2.1 + 2.45 = 4.55 for each degree;
which amounts to ^ pai+s for the 8° that the zero is too
high. Above 40°,the former error ^ will be augmented
by the difference of the equations for each degree that
the temperature is above his zero, viz. 2.45- 2.1 =^l..
In either cafe it is to be obferved, that the progreflive
rate of equation for the heat of the quickfilver is not
here taken into the account; becaufe it will not produce
any material difference, unlefs one barometer is much
hotter than the other, at the fame time that their verti-
cal diftance is very great. Thus the gad degree of Fah-
renheit, or freezing temperature, which is fundamen-
tal in all thermometers, happens, fomewhat remarkably,
to be the zero of the fcale, when the Englifh fathom
bears fuch proportion to the modulus of the common lo-
garithms, as that their difference, in computing heights
by the barometer, brings out the refult in fathoms. No
other proportion of a meafure will do it: for if we fup-
pofe twenty-four of different lengths, between ours
and the French toife, each furpafling the othei by riSho
of that toife, the zero of the fcale, in computing heights
by thefe meafures refpedtively, will afcend a ffngle de-

743 Col. roy’s Experiments far

gree on each; and the French toife being the 25th, will
have its zero nearly at the 57th degree: about which
temperature the expanfion of air appears, from the ex-
periments, to be at its maximum. From that point,
therefore, the equation will diminifh both ways, though
by a quicker progreffipn for condenfation, than it doth
for dilatation.

Having thus compared, in a general way, the refults
of the Britifh obfervations with thofe of Mr. de luc,
pointed out what feem to be the chief caufes of the con-
ftant defe£t found in his rule, and thereby obtained, it is
hoped, fome corrections tending to improve the theory
of the barometer, when applied to the meaiurement of
heights in middle latitudes ; it remains to ftiew the prin-
ciples, whereon the table for the equation of the air hath
been conftruCted. Previoufly however to this, it may be
proper to compare, with as much brevity as podible,
thefe obfervations, with others that have been made To-
wards the Pole and at the Equator: from which it will
appear probable, that the rule which aniwers in middle
latitudes, will not in the frigid and torrid zones.

In i7735 Captain phipps, now Lord mulgrave, com-
manding two of his Majefty’s fhips then lent on difcove-
ries towards the North Pole, meafured geometrically, with
g;reat care, the height of a mountain in Hakluyt’s Ifland

near

meafuring Heights with the "Barometer. 743
near Spitzbergen, and found it to be 1503 feet above
the level of the fea. On the morning of the 1 8th of Au-
guft, the following obfervations, at the fea-lhore and top
of the mountain, were made with a fingle barometer,
wherein the quickfilver had not been boiled.

At 6 h. A.M. Barometer at the fir ore, — ■ — 30.040 therm. 50*

7 h, 45' A.M. Ditto at the top of the mountain, 28.266 — - — 4^

8 h. 45' A.M. Ditto at the top of ditto, — 28.258 — — - 42

11 h. 45' A.M. Ditto at the fea-fhore, — 30.032 — — - 44

Whence we have the following computations, equated
for the times correfponding to the two obfervations at
the top.

From thefe obfervations it appears that, inftead of the
ufual equation to be added to the logarithmic re-
fult, in order to obtain the true height in Britain, when
the temperature is 42°, there is an excefs of tIIq: and,
inftead of the ufual ratio of the weight of quickfilver to
columns of air, of equal altitude and temperature in
Britain, namely about moo, we have that of 10224
to 1.

Vol. LXVII, 5 G

Mean 1577.1—+ 47

1000

Thus

744 Co/. hoy’s Experiments for

Thus air at Spitzbergen feems to be fpecifically hea-
vier, than that affected with the fame heat and preffure
in the middle latitudes: whence it follows that, inftead
of 3 a0 which is found to be the zero of the fcale about
the middle of the temperate zone, we fhall have —
1 90. 2+42,°= 6i°.2 for the zero at Spitzbergen, within
10° of the North Pole.

It is much to be regretted, that the French academi-
cians, when employed in meafuring the degrees of the
meridian in Peru, were not fupplied with better barome-
ters, and that they made not obfervations at correfpond-
ing times ; fince the fcene of their operations was un-
doubtedly preferable to any other on the furface of the
globe, for determining many curious points with refpedt
to the modifications of the atmofphere in the torrid
zone : neverthelefs, by attending diligently to what Mr.
bouguer ,n> hath told us, of the fteadinefs of the baro-
meter

( n ) He fays, that at the South Sea, Reaumur’s thermometer, in the morn-
ing before Sun-rifing, flood at 19°, 20°, or 21°; and in the afternoon at 26°,
27 , or 28 . T. he refpeftive means correfpond to 76°^ and 92T of Fahren-
heit, and make the mean heat of the day 84T At Quito the temperature
continued at i4°or 1 50, anftvering to 65°- of Fahrenheit. At the fummits
of Corajon and Pichincha, the thermometer flood in the morning feveral
degrees below freezing, and varied 170 in the heat of the afternoon; whence
the mean temperature at thefe higheft Rations, would probably be about 43° j of
Fahrenheit. He farther fays, that in the torrid zone, whatever may be the

mean

meafuring Heights with the Barometer , 745

meter throughout the year ; the uniformity of the mean
temperature in every affigned ftation ; and his mode of
computing, by means of the tables of common loga-
rithms, the altitudes of the Cordillero mountains above
the valley that extends itfelf between them ; it will be
no difficult matter to difcover, nearly at leaft, what fort
of equation became neceffary ; and what were the rela-
tive weights of quickfilver and air of the mean tempe-
rature, not only in that high region of the atmofphere,
but alfo at the level of the fea.

Thus, by infpefting the table of computations, it will
appear, that columns of air, whofe bafes were removed
fix or eight thoufand feet from the level of the fea, and
whofe heights equalled that diftance, when the tempera-
ture was 550 of Fahrenheit, as determined from the
mean between the coldeft of the morning and hotteft of
the afternoon, the mean logarithmic defedt was only ^ :
whereas, in meafuring heights near the level of the fea,
in middle latitudes, the common equation for that tem-
perature is about The mean ratio of the weight of

quickfilver to air, on thefe long columns comprehended
refpedtively between Carabourou and Quito, and the

mean heat in any affigned ftation, it continues uniformly the fame throughout
the year. In this rough eftimation of the temperature in Peru, it feented unn~
eeflary to examine, whether the true thermometer of reaumur. was uieJ or no.,
as it could produce no material difference, except at the very hotteft Hattons.

F c r, fummits

746 Col. roy’s Experiments for

fummits of Pichincha and Coracon, is that of 16793
to- 1 . On the altitude of 1534 feet, intercepted between
Carabourou and Quito, which fhort fection of the co-
lumn is about half-way between the level of the fea, and
the fummits of the Cordilleros, the mean temperature
being 66°, the ratio is that of 15089 to 1: hence it
feems probable, that quicklilver would have to the dif-
ferent fedtions of the general column of air, compre-
hended between the fea and the top of Coraqon, nearly
the following ratios :

T emp*

At the level of the South Sea, 84^-

Half-way from thence to Carabourou, 7 5^
At Carabourou, — — 66~

Half-way from thence to Coracon, 5 5

At the fummit of Coraqon, — — 43J-

13100 to 1

14100

15100

16100

17100

Whereof the mean is, — 65 15 100

Mr. bouguer tells us, that the barometer in the tor-
rid zone varies not at the fea-lhore above two and a half,
or at molt three lines throughout the whole year. At
Popayan, its variation is only a line and a half; and at
Quito a Angle line. Now let us fuppofe, that an altitude
had been meafured with the barometer at the level of

the

meafuring Heights with the Barometer. 747
the S.outh-fea, where the defcent of quickfilver at the
upper ftation was exactly an inch in the mean heat of
the day, anfwering to 84°^. On the former fuppofition
of the weight of quickfilver to air, the height would be
13 1 00 inches or 109 1.7 feet.

Hence 8+|-i69^9-76i| = 8 6

^28.930 84|-l69=28.76l j

the logarithmic refult, which is defective 201.1, or
nearly parts. Now this equation being divided by
2.45 the mean expanfion of air, we have nearly 920
for the difference between 84°^-, the temperature of the
obfervation, and the zero of the fcale, which reduces it
to ~7°| of Fahrenheit. If it fhould be thought that I
have fuppofed the air to be too light at the level of the
fea under the equator, let it be taken to quickfilver only,
at a mean between 13 100 and 12672, which feems to
have been the ratio of their weights at Genoa, when Mr.
de lug’s temperature was 79% and we fhall have
12881 inches, or 1073.4 feet of air, for the counter-
poife to the inch of quickfilver in the barometer : hence
1073.4-890.6=^— ^=8 3°.7, will denote the number
of degrees that the zero of the fcale would, in that cafe, be
below the temperature of the air, which brings it to within
lefs than a degree of the cypher of Fahrenheit. But in

middle latitudes the zero of the fcale is at 320, anc^ ^ie
a equation

74B Col roy’s Experiments for

equation, applicable at the level of the fea for the heat of

84*1, is at moft only f^-inftead of

Mr. bouguer found, that the rule which his expe-
rience had furnifhed him with, for computing heights
with the barometer between the ranges of the Cordil-
leros, namely, that of deducing ~th part from the
number of toifes expreffed by the logarithmic dif-
ferences, which agrees nearly with the equation which

1 have made ufe of in the table of computations, would not
anfwer when he came to apply it at the level of the fea.
He tells us, indeed, that the elafticities of the air, above
and below, are there, as well as in Europe, exactly pro-
portionable to its condenfations ; and even, that the in-
tenfity of the elaffcic force, or fpring of the air, is every
where equal in all places of the torrid zone that are con-
fiderably elevated. The real condenfations in each place
are proportionable to the weights of the fuperior columns
caufing the compreffion ; thefe condenfations being in
geometrical, the heights are in arithmetical progreffion.
But below the fame law doth not take place ; becaufe the
intenfity of the elaftic force is really confiderably lefs at
the level of the fea, than it is at one or two hundred
toifes above it, notwithstanding the effe£t of the heat,
which fhould render it greater. It is to be obferved, that
Mr. BOUGUERhath not given us the obfervations whereon

he

meafuring Heights with the Barometer . 749

lie founded this laft deduction ; and his note on the text,
which I apprehend, neverthelefs, conveys his true mean-
ing, is contradictory to it : for there he fays, that the di-
latation occafioned by the heat throughout the day,
changed the diftribution of the weight with regard to
all the places lituated within the Cordilleros, as well as
on other mountains, and made the lower fections of the
columns contain lefs and the upper fections more air,
than they ihould have done, had it been a perfectly
elaftic fluid.

Having now mentioned all the barometrical obferva-
tidns that have come to my knowledge, tending any way
to throw light on this very intricate fubjeCt, it remains to
ium up, from the whole, the general principles whereon
I have proceeded in conftruCting the table of equation
for the heat of the air.

It will be remembered, that I have more than once re-
marked, that in the Britilh obfervations, when the tem-
perature was 5 20, the defeCt was the lowermoft

barometer ftanding at or near the level of the fea; but
in the obfervations on Tinto, a confiderable hill apper-
taining to the third clafs, whofe bafe is elevated 700 feet
above the level of the Clyde at Glafgow, when the tem-
perature was 5 20, 1 found the equation to be little more
than Again, thefe two faCts being compared with

the

2

75© Col. roy’s 'Experiments for

the aggregate refult of Mr. de luc’s obfervations, where
the lowermoft barometer flood about 1300 feet above
the fea, the equation for the fame temperature feemed
n6t to exceed Laftly, thefe circumftances being

confronted with the refults of Mr. bouguer’s obferva-
tions, where the lowermoft barometer flood from 6000
to 8000 feet above the fea, the mean equation for 55’
was only &L, which gives for the heat of 5 20. Now
thefe Peruvian obfervations, which I believe to be ex-
ceedingly good from the fteadinefs of the barometer in
that part of the world, being fubllituted in lieu of thofe
not yet obtained in our own quarter of the globe, there
feemed to me to be a neceflity for concluding, that the
equation for middle latitudes, with any afligned tempe-
rature above or below the zero of the fcale, diminifhed
as the height of the place above the fea increafed ; which
confequently implied, that the magnitude of the loga-
rithmic terms increafed fafter than the dilatations of the
air. But when tire comparifon was carried yet farther, and
the obfervations in Peru and at Spitzbergen were fairly
brought into one view, there appeared to be fufficient
grounds for fufpecting, if not abfolutely for concluding,
that there could be no fixed zero for the fcale depending
on the temperature of the air; but that it would change
with the denfity of the atmofphere appertaining to the

latitudes.

meafuring Heights with the Barometer. 751
latitudes, climates, or zones of the earth, where the ob-
fervations were made. On this fu ppo fit ion it was natural
for the mind to form to itfelf fome general hypothefis,
which might ferve to account for the appearances ; and
the firft that prefented itfelf was the following : that the
atmofphere furrounding our globe might poffibly be
compofed of particles, whofe fpecific gravities were
really different; that the lighted: were placed at the
equator; and that the denfity of the others gradually in-
creafed from thence towards the poles, where the hea-
vieft of all had their pofition (a> .

It is a well known and eflablifhed fact, that in the
middle latitudes, a North or North-eaft wind conftandy
raifes the barometer, and generally higher as its con-
tinuance is longer. The contrary happens when a South
or South- weft wind blows; for I believe it is commonly
loweft when the duration and ftrength of the wind front

(t) It was fuggefted by Dr. george fordyce, that equatorial and Green-
land air might be brought bottled up, and weighed in this country in air of the
refpe&ive temperatures, by means of a curious balance whereof he is poffeffed,
in order to fee whether any difference could be difcovered in their fpecific
gravities. A thought of the fame kind, but more ealily put to experiment,
occurred to Lieutenant glenie, of the Royal Artillery, namely, that of
weighing equatorial and polar fea-water. To this gentleman I am obliged for
his aflillance in part of the manometrical experiments, as well as in feveral of
the computations .

Vol. LX VII. 5 D

that

7 5 2 Co/. roy’s Experiments for

that quarter have been the greatefh Thus the
North-eaft wind, by blowing for any length of time,
brings into the middle latitudes a mafs of air heavier
than that which naturally appertains to the region, and
raifes the barometer above its mean height. The con-
tinuance of a South -wefter carries off the heavy air, de-
ports a much lighter body in its Head, and never fails
to fink the barometer below its mean height: hence,
in the middle parts of Europe, there is a difference of
about two inches and a quarter between the higheft and
lowed: flates of the barometer. But fuppofing it to be only
two inches, the difference of preffure ff ill amounts to
77th part of the whole weight of the atmofpliere. Now
it is evident from the Peruvian obfervations, that the
greateft fluctuation of the barometer, which is at the
level of the fea, doth not exceed 0.226 of an inch, or
~d part of the whole prelfure ; and if the change fhould
be no greater at the poles, which I think not impro-
bable, it follows, that the meafurement of heights by
means of the barometer, in middle latitudes, will be
more precarious and uncertain than in the torrid and
frigid zones.

Such in general were the firft ideas which the compa-
nion of the operations of the barometer with the effeCls

meafuring Heights with the Barometer . 753

of the North-eaft and South-weft wind^ on that inftru-
ment, fuggefted with regard to the different denfities of
the atmofphere in the different zones of the earth.

But fince the experiments on the expanfion of moift
air have fhewn its elafticity to be fo much greater than
that which is dry, I apprehend, that the fimple principle
of heat and moifture may fuffice to account for all the
phenomena. Thus it is univerfally admitted, that there
is a greater degree of humidity and heat in the air, near
the earth’s furface, than there is in the higher regions of
the atmofphere. The elafticity or expanfion of the
lowermoft fecftion (q) of every column of air, whether

long

(p) I. have been well informed, that in China the North- weft wind raifes
the barometer mold, and is highly electrical; it is at the fame time the drieft
and the coldeft; and at Canton, under the Northern tropic, there is frequently
ice. On the Eaft-coafts of North America the feverity of the North-weft
wind is univerfally remarked ; and there can fcarcely be a doubt, that the inha-
bitants of California, and other parts on the Weft-fide of that great Conti-
nent, will, like thofe on the Weft of Europe, feel the ftrong effeCts of a North-
eaft wind. The extraordinary drynefs and denfity of the wind from the ..North
pole, feems therefore to be occafioned by its palling over the Continent ot
Europe and Alia on one fide, and that of North America on the other. I hole
who live on the Eaft and Weft-coafts of South America, will find the drieft
and coldeft winds come to them refpeCtiveiy from the South-weft and South-
ealt. As the winds feem to be colder, drier, and denfer, in proportion to the
extent of land they pafs over from the poles towards the equator, fo they appear
to be more moift, warm, and light, in proportion to the -extent of Ocean they
pais over from the equator towards the poles. Hence the humidity, warmth.

and lightnefs, of the Atlantic wind to the inhabitants of Europe.
(q) Mr. de luc feems to have fnfpeded fomething of this k

5 D 2

kind towards the
end

754 C<5/. rot’s Experiments for

long or fhort, will confequently be greater than the up-
permoft fedlion of it; for the heat, by diflolving the
moifture, produces a vapour lighter than air, which mix-
ing with its particles, removes them farther from each
other, increafes the elafticity of the general mafs, and
diminifhes its fpecific gravity comparatively more than
it doth that of the fedlion immediately above it, where
there is lefs heat and lefs moifture. Hence I infer, that
the equation for the air, in any afligned vertical, will
gradually diminifh as the elevation of the place above
the fea increafes, and that it will vanifh at the top of the
atmofphere. This is in fome refpedt confirmed by the
experiments on the expanfion of rare air; for from them
it appears, when the particles are very far removed
from each other, by a great diminution of preflure, as is
undoubtedly the cafe in the higher regions of the atmo-
fphere, they lofe a great part of their elaftic force. Thus
the equation, anfwering to any particular temperature,
above or below the zero of the fcale, at different heights
above the furface, will, I apprehend, be exprefled by the
ordinates to a curve of the hyperbolic order, whofe cur-

end of his 8th chap, fur les difficulty a vainer e: and in that which follows, he
gives proofs of the lightnefs of vapours with regard to air, faying, that they
point out fire to be their vehicle. He afterwards quotes newton with refpe<3?
to the lightnefs of a humid atmofphere compared with one that is dry-

| vature

meafuring Heights with the Barometer. 755
vature may be fuppofed to change fail near the furface
of the earth, and differ infeniibly from a flraight line at
great heights above it.

With regard to the latitudinal equation, the fame
principle of heat and moifture feems to make it proba-
ble, that fuch will become neceffary in operating with
the barometer; for it is well known, that there is a great
degree of humidity in the air between the tropics; and,
on the contrary, that the polar atmofpheres are very dry.
The heat and moifture being greateil at the equator, there
the elafticity or equation will likewife be the greateil at
the level of the fea; and the zero of the fcale will neceffa-
rily defcend to a lower point of the thermometer, than
that to which it correfponds in middle latitudes. As the
elafticity of the air at the level of the fea, or equal
heights above it, with the fame degree of heat, will al-
ways be proportionable to the quantity of moifture dif-
folved in it, therefore it will gradually diminifh from the
equator towards the poles ; that is to fay, the zero of the
fcale will afcend in the thermometer, coincide with the
3 ad degree in the middle latitudes, and, in its motion
upwards, will give the equation to be applied with the
contrary flgn in high latitudes. Hence I infer, that every
latitude, climate, or zone, will not only have its particu-
lar zero, but alfo its particular curve, whofe ordinates

will

756 Col. roy’s Experiments for

will, always meafure the equations applicable in the rc-
fpeftive fituations. The equatorial curve will probably
change the faff eft, and the others become gradually flat-
ter, as they approach towards the poles, where the
greater, but more uniform, denfity of the atmolphere
may occafion it to differ little from a ftraight line. I ap-
prehend, however, that even at the pole fome fmall di-
minution might be found to take place in the equation,
was it poflible, in that region, to prove it by experiments
at a fufflcient height above the level of the fea.

The table of the equation, depending on the heat of
the air, annexed to this paper, is conftrudted for middle
latitudes. It extends to temperatures from 1 2° to 92° of
Fahrenheit; and for fituations fo greatly elevated
above the fea, as to make the mean barometer between
the two ftations ftancl no higher than 19 inches. As the
equation correfponding to the lower parts of the atmo-
fphere, contained in the right-hand columns, will come
more frequently into ufe than that appertaining to the
higher regions, comprehended in thofe on the left;
therefore, in the firft, it is given for every half; and in
the laft only, for every whole inch of defcent of quick-
lilver in the tube.

1 he equation found in the column of 29 inches, cor-
xefponds exactly with the expanfion of air refulting from

the

1

meafuring Heights with the Barometer. 757
the manometrical experiments ; and the ratio of diminu-
tion, in the temperature of 5 20, hath been taken from
the Peruvian obfervations, fuppofing it to decreafe uni-
formly on each inch, or on the eight inches be-
tween 29 and 21. For the fake of fimplicity, as well as
from the want of fufficient data for afcertaining the
lengths of the ordinates of the curve, the arithmetical
hath been preferred to any progreffive diminution that
might have been adopted, though by this mode the re-
fults would have agreed better with fome of my own, as
well as Mr. d e luc’s obfervations. In each of the co-
lumns the equations for particular temperatures, com-
pared with that for 120 or 920, are reciprocally propor-
tionable, fo that the maximum of the rate always cor-
refponds to the fpace between 5 20 and 7 20, as indicated
by the manometer. It will be obferved, that though the
equation in the table is only given for every io° of dif-
ference of temperature, yet, by the intermediate rates for
lingle degrees in the columns refpeclively, and the ratio
of diminution for the height of the mean barometer
above the fea, expreffed in that towards the right-hand-,,
the equation for any particular temperature may be rea-
dily obtained. The application of this table makes the
third part of the rule, for meafuring heights with the
barometer. When the mean temperature of the column

758 Col. roy’s ’Experiments for

of air is above 320 of Fahrenheit’s thermometer in the
fhade, add the equation correfponding to the tempera-
ture and height of quickfilver in the mean barometer to
the logarithmic altitude; when below 320, fubtradt the
equation from the logarithmic altitude ; the fum in the
firlt cafe, and difference in the laft, gives the real height.

Befides the table of equation for the air, adapted to the
meafurement of the greateft acceflible heights the baro-
meter can poJTibly be applied to in middle latitudes, I
have annexed, for the ufe of thofe who may prefer fim-
plicity, and frill doubt of the vertical diminution, a ther-
mometrical fcale of the equation, fuited to Englifh and
French meafures, with their refpedtive thermometers. It
will readily be conceived, that the divifions, expreffing
the 1 oooth parts in this fcale (r\ are unequal, fince they
follow the inverfe ratio of the thermometrical compared
with the manometrical degrees. Where thefe laft are
the greateft, as between 5 20 and 7 20, the divifions ex-
preffing the equation are the fmalleft, becaufe a greater

(r) Any fcale of this kind, tinlefs it had been mechanically divided by a
•mathematical inflrument-maker, could not be rendered very exa£l ; and it may
be expected, that the imperfections in the original will be augmented in copy-
ing by the engraver, notwithftanding the utmoft care on his part : wherefore,
on the left-hand fide of the plate, I have annexed tire number of degrees and
decimal parts of Fahrenheit, below the temperature of 9i°.88, correfponding
to every xlgjrth parts of the equation, by which means the unequal fcale may,
at any time, bo divided with fufScient accuracy.

number

meaf wring Heights with the Barometer. 759
number of them correfpond to the fame thermometrical
fpace. When the height is required in fathoms, the
zero of Fahrenheit correfponds to -71.72, and the
boiling point to +412.49: the fum of the two equa-
tions 484. 2 t is the actual expanfion of common air from
the heat of 212°. When the French toife is made ufe
of as the meafure, the zero of the fcale hath been fhewn
to coincide with 57°.i8 of Fahrenheit, or +n°j of
reaumur. The negative equation i34°.72 anfwering
to -14°^ of reaumur, and the pofitive 349°.49 cor-
refponding to +8o°, or the boiling point, being added
together, make again 484.21.

In order to convey a more diftindt idea of the effedt
which heat produces in the dilatation of different kinds
of air, compared with quickfilver, along with the fcale
for the equation I have placed another, expreffing the
adtual and relative expanfions, refulting from the mean
of the experiments, for every 20° of difference of tem-
perature. This fcale is intended to give a comparative
view of the manometrical with the thermometrical
Ipaces, mentioned in the fecond fedtion.

I fhall now clofe this paper, which hath already
greatly exceeded the limits I wiflied to have been able to
prefcribe to it, with a few remarks on the error of the rule,
perceivable in the tables of computation, and the mea-

Vol. LXVII. 5 E lures

760 Col. roy’s Experiments for

fures that fhould, in my opinion, be taken to bring the
theory of the barometer to a ftill greater degree of per-
fection, fuch as I believe it to be really capable of.

By infpeCtion of the tables containing the computa-
tions of the Britifh obfervations, it will be fcen, that the
error of the rule is in general very fmall. In the Lon-
don clafs it is greateft on Shooter’s-liill, making the
height five feet too little. In thofe at Tay bridge, one of
the obfervations on Schihallien gives a defective refult of
29^ feet; but this is eafily accounted for, as it certainly
arofe from the fhort time given to the barometer to lofe
the heat it had acquired in carrying upwards, thofe
deftined to obferve at the fummit arriving there too late,
that is to fay, towards the expiration of the whole hour
which the inferior barometer had been obferved in. One
of the obfervations on Carmichael-hill, though a fmall
height, is defective eight feet, which I afcribe to the
South-weft wind and humidity of the air. From the
fame caufe I would account for the uniform defeCt in
, the firft part of the Edinburgh obfervations : in the laft
part of thefe, the circumftances having changed, the er-
ror hath the contrary fign. In the Linhoufe clafs ol ob-
fervations, the fame caufe of defeCt appears on the ift
of December, 1775, an(f on t^ie 20th of November,
and 1 7th of December, 1776. The only refult which I

confider

meafuring Heights with the Barometer. 761
contider as very irregular, and do not pretend to account
for, is that for the height of Moel Eilio, a hill fituated
between Carnarvon and Snowdon: the real altitude
2371 feet, is exceeded by the barometrical refult 2 1 feet,
though the circumftances were fuch as, in other cafes,
generally make it fall fhort.

At the bottom of the tables of computations I have
occafionally fubftituted Mr. de luc’s equation for the
air, in calculating one or more of the greateft heights,
that the difference between the two methods might be*
come more obvious. Thus the firfl: obfervation on Schi-
hallien is defective feet; the mean of thofe on Tinto
29 feet; Moel Eilio 41 feet; and Snowdon 81 feet.

With refpedt to the refults that the rule produces on
Mr. de luc’s heights it will be obferved, that it anfwers
very well in the cold obfervations, which, with his rule,
were often defective 60 or 70 feet; but gives too much
in thofe that are hot. If, however, the whole of thefe
hot obfervations had been included, the apparent error
would have been lefs; for the mean defedf was taken at
■~s for the hottefl temperature, whereas it fometimes
amounts to Ty^. On the height of the Dole the rule errs
indefedt; and on the mean of Mr. de la caille’s ob-
fervations, at the Cape of Good Hope, it exceeds the
truth. By fubftituting Mr. de luc’s equation for the air,

7 6 a Col. roy’s Experiments for

in the computations of the Dole and Table-hill, the re-

fpedtive refults are defective 96 and 62.6 feet.

To the Britifh obfervations a table is annexed, con-
taining the barometrical computations of altitudes not yet
determined geometrically. In the chief part of thefe the
inferior barometer flood at Belmont-caftle, the feat of the
lord privy-feal for Scotland, by whofe directions the cor-
refponding obfervations were made. This table likewife
comprehends Mr. banks’s obfervations in 1772, for the
height of the South-pap of Jura, above Freeport in the
ifland of Ifla, and thofe he made the fame year, to ob-
tain the height of Mount Hecla, above Hafniford in
Iceland,

X-aftly, it is to be obferved, that in the application of
the table, the equation found in the columns 29J, 30,
and 30C, will never come into ufe, except in the mea-
furement of fhort columns of air, whofe bafes fland at,
or not much above, the level of the fea^. In an ifland,

whofe

(s) Having been accufiomed, from the beginning, to call the ftation of the
inferior barometer the place of obfervation, and to fuppofe the mean height of
its quickfilver to denote V e elevation of the place above the fea, for the fake
of fimplicity I adapted the formula to the height of quickfilver in that baro-
meter, and made all the computations in the tables accordingly. But it having
Ven fuggefted to rae, firft by Sir george shuckburgh, and afterwards by
iVIr. de iatc, that this mode, though the ealieft, was not flri£Uy accurate, nor
with the principles whereon a vertical diminution of the equation for

the

meafuring Heights with the Barometer. 763
whofe climate is fo very variable as that of Britain, fet-
tled weather fhould be chofen as the belt time for obfer-
vations. With any fudden fall of the barometer, in any
affigned ftation below its mean height, it is apprehended
that the rule will have a tendency to give defective re-
fults ; and the contrary lhould happen when, from the
increafed weight of the atmofphere, it rifes much above
the mean height.

From what hath been faid in the courfe of this paper,
it will be perceived, that though the error of the rule is
in general very fmall, yet now and then fuch irregulari-
ties do occur as plainly fhew, that fomething ftill remains
to be done, in order to perfect the theory of the baro-
meter.

The exigence, or otherwjfe, of a latitudinal equation
being a point of the greateft confequence, lhould be de-
termined with fo much care as to leave no doubt remain-
ing on that head. And as this can only be effected by
differences that are extremely obvious, the obfervations
for that purpofe fhould be made at the equator, and as
near as poffible to the poles'^. Peru is no doubt the beft

lituation

the heat of the air was founded, I have iince changed it to the mean barometer,
or middle of the column of air intercepted between the two ftations. In this
way all the great heights have been re-computed : the fmaller altitudes, not
being fenfibly affe&ed by the alteration, continue as at firft.

(t) Some idea may be formed what altitudes on the furface of the globe are

accellible

764 Col. Roy’s Experiments for

fituation on the globe for conclufive equatorial obferva-
tions; but as it would be found very difficult to carry any
fcheme of that kind into execution, fuch as may be more
eafily obtained in our Weft India iflands, which have the
higheft mountains, would be very fatisfactory with re-
fpe£t to the expanfion and weight of moift air, at dif-
ferent heights above the lurface. At the tops of the
mountains in the torrid zone, the obfervations would
always be fufficiently cold; but it would be of ufe like-
wife, to have the coldeft poflible at the level of the fea,
under or near one of the tropics, when the Sun was ip
the other.

With regard to obfervations in the frigid zones, Spitz-
bergen feems to be as proper a fituation as any ; though
others may no doubt be found in the Northern parts of
the Ruffian empire: and it is prefumed, that the Pe-
terfburg academy would direct the experiments to be
made.

acceflible to man, by confldering the height above the fea of the inferior line
of perpetual fnow. In the middle of the torrid zone it appears, from Mr.
bouguer s obfervations, to be elevated 5201 yards, and 4476 about the tro-
pics. In middle latitudes there is eyerlafting fnow on the mountains at the
height of 3300 yards. In the latitude of 8o° North, Lord mulgrave found
the inferior line of fnow to be only about 400 yards above the fea: whence we
may conclude, that the furface of the earth, at the pole itfelf, is for ever
covered with fnow.

5

The

meafunng Heights zvitb the Barometer . 765

The Peak of Teneriffe, ./Etna, the mountains of Au-
vergne and Rouffillon, as well as Hecla in Iceland, are all
very proper for obfervations in intermediate latitudes.

Within the ifland of Great Britain, Ben Nevis feems
to be the belt mountain for barometrical obfervations,,
becaufe of its great height, its vicinity to the fea, and
that there is very good ground clofe to its foot (which is
rarely the cafe in the Highlands) for the meafurement
of the bale, that would be made ufe of in the geometrical
operations.

One of the chief caufes of error in barometrical com-
putations, I apprehend, proceeds from the mode (though
limplicity is in its favour) of eftirnating the temperature
of the column of air from that of its extremities, which
mull be faulty (m> in proportion as the height and dif-
ference of temperature are great. Where very accurate
conclufions are expedited, fimultaneous obfervations, at
different times of the day, and different feafons of the
year, fhould be made with feveral barometers, placed at
different heights, each accompanied with a thermometer
and manometer. By this method, the progreffion of
temperature, as well as the law of diminution of the
equation, from the pofition of the inferior barometer
above the fea (if fitch diminution doth really take place)

(u) This is taken notice of by Mr. de luc.

would

766 Col. roy’s Experiments for

would be obtained with certainty. Suppofing, forin-
ftance, Ben Nevis was divided into four feCtions, five ba-
rometers, with as many obfervers, would be neceflary.
This number may feem great, but the expence of peo-
ple employed in that way would be inconfiderable. And
if it fhould be judged proper, there could not furely be
any great difficulty in providing reafonable accommoda-
tion for an obferver, who fhould live a whole year at the
top of the mountain, while another made correfponding
obfervations below.

But the perfecting of the theory of the barometer is not
the only advantage that would accrue from a combina-
tion of thefe obfervations; for, while they were carry-
ing on in different climates, or zones of the earth, good
opportunities would offer of determining the refractions,
as well as the force of gravity and figure of the globe,
from the vibrations of the pendulum.

The mean expanfion of common air is already found
to be greater than what was formerly fuppofed ; where-
fore the mean refraCtion will be altered proportion ably.
And fince the expanfion of moift air is found to be fo
much greater than that of common air, a larger field for
inquiry and inveftigation is now laid open.

With refpeCt to the experiments with the pendulum,
Mr. bouguer feems to have been the only perfon, fo far

as

meafurmg Heights with the Barometer. 767
as I know, who hath taken the denfity of the medium
in which it performed its vibrations into the account, and
given us its length at the equator in vacuo. But if w©
are to judge of the denfity of the air in the frigid zone
from the barometrical obfervations at Spitzbergen, the
pendulum there muft have loft fo much of its weight, as
to have leffened confiderably the number of vibrations
below what they would have been in vacuo, in the fame
temperature. Having confidered the effect that this
would produce, I collected the bell experiments that
have hitherto been made with the pendulum into one
view, and having applied the equation that the denfity
of the air, in which they feverally vibrated, feemed ta
require; I found from computation, that the ratio of the
diameters of the earth is (as Mr. bouguer fuppofed it)
nearly that of 178 to 179, inftead of 229 to 230, as
edimatedby Sir Isaac newton, and which agrees very
nearly with the mean refult from the meafurement of
the degrees of the meridian. The experiments with the
pendulum are fo fimple and eafy, may be repeated fo
often in all fituations, and are fo much more confident
with each other, than the meafured lengths of degrees
of latitude, that it appears to be incomparably the bed
method for determining the figure of the earth. And it
it fhould really be found fo flat a fpheroid as the pendu-
Vol. LXVII. SF him

7 68 Col. roy’s Experiments for

him feems to make it, both parallaxes and refractions,

will require correction.

Upon the whole, though I wifhed to be concife in the
recital of the experiments and obfervations contained in
this paper, yet I found it neceflary at the fame time to be
explicit. Some of them were either entirely new, or ma-
naged in a different manner from what they had for-
merly been. This forced me into a comparifon of many
minute circumftances attending the operations, and to a
tedious, though neceflary, combination of the various
refults. Without taking a comprehenfive view of the
whole matter, and ftating every thing with fairnefs and
candour, I could not convey to others the ideas I enter-
tained of it myfelf; nor enable them to judge, how far I
had been juft in the conclufions already drawn, or con-
fiftent in my fuppofitions concerning fucli points as are
yet left doubtful. If I have been obliged to differ from
Mr. de luc, it is becaufe the Bri'tifli obfervations, as well
as his own (confidered by their extremes) feem to autho-
rize it: he is himfelf too candid to fuppofe, that I have
had criticifm in view, or indeed any other objeeft, than
that of contributing my mite towards the difeovery of
the truth, from the very good foundation which he hath
already laid for it. I am aware it may be alledged, that
I have rendered the theory of meafuring heights by
c the

meafufing Heights with the Barometer. - 769
the barometer fo much more complicate and difficult,
as perhaps to deter others from applying it to ufeful
purpofes. To this I arifwer, that though it feem utterly
impoffible to render what is really intricate in its na-
ture, extremely fxmple ; yet that the bell and furell
method of arriving at limplicity at laft will, in the firft
place, be to afcertain the limits of deviation of the
rule, by a proper number of good obfervations, made
in circumftances and fituations as different as poffible
from each other. In the prefent flate of the matter, I
doubt not but the barometer will be found to give re-
fults fufficiently near the truth for all ordinary purpofes,
the nicer bulinefs of levelling alone excepted. It is the
only inftrument by which the relative heights of places,
in very great and diftant trails of country, can eafily and
fpeedily be obtained, by the preffure of the atmofphere
alone. The method of tiling it is attainable by all, re-
quiring only a little habit, and fome degree of attention
to prevent the admiffion of air into the tube. Few peo-
ple are qualified for the tedious and very laborious ope-
rations of accurate geometrical meafurements. Moun-
tainous countries rarely afford bafes of fufficient length,
which, to avoid error, muff be meafured again and
again with the utmoft care. Inftruments of the moil ex-
penlive kinds mull be employed to take the angles ; at
the fame time that a thorough knowledge of their ule,

5 F 2 and

77 o

Col. roy’s Experiments , &e

and a fcrupulous attention to their various adjuftments,
become indifpenfably neceffary, In fhort, the facility of
one method, compared with the other, is fo exceedingly
obvious as to need nothing elfe to recommend it as a
fubject very curious and ufe'ful, and therefore well wor-
thy of the refearches of philofophers, till, by their united
labours^ it hath been brought to perfection.

N° i:

[ 77i ]

Table fhewing the equation depending on the temperature of the column of air, and its elevation above the fea, as denoted by the mean height of quickfilver in the

inferior and fuperior barometers.

Mean

equated height of quickfilver in the inferior and fuperior barometers.

Equation in thoufandth parts of the logarithmic altitude.

*

Rate of di-
minution for

sfl-a

Inches

9

20

21

22

23

24

25

26

26|

27

271

28

28 i

29

292

30

3®l

whole and
half 'inches.

92°

3

89.364

95-456

101.548

107.640

H3-733

119.825

125.918

132.010

I35-057

138.103

141.149

_

144.195

147.242

150.288

2.38

153-334

156.381

159-427

[ 6.0925

T3

3

*2

1.44

i-73

2.0 3

2.13

2.18

2.22

2.27

2.32

2-37

2.42

2.47

2.52

2-57

l 3.04625

;§

82

74.967

80.078

85.189

O
O
c n
6
O'

95-41 1

100.522

105.633

•

1 10.744

—

113.299

—

115-855

—

118.411

—

120.966

—

123.522

—

126.077

—

128.632

—

131.188

—

1 33-743

r 5.111

n

1.49

1.80

2.10

2.21

2.26

2.3I

2.36

2.41

2.46

2.51

2.56

2.61

2.66

L 2.5555

•3

72

-£j

60.028

64.120

68.213

72-305

—

76.398

80.491

'84-583

—

88.675

—

90.722

—

92.768

94.814

—

96.860

—

98.907

—

100 953

102.999

105.047

—

107.093

—

r 4.09250

J

’*5

1.52

1.83

2.14

2.25

2.30

2-35

2.40

2.45

2.51

2.56

2.61

2.66

271

1 2.04625

62

jf

44.818

47-873

50.928

53-983

57-°39

60.094

'63.150

66.205

—

67-733

—

69.261

70.789

—

72.316

—

73-844

75-372

—

76.900

—

78.427

—

79-954

j 3-°555

0

i-55

1.87

2.18

2.29

2.34

*•39

2-45

2-50

2-55

2.60

2.66

2.71

2.76

1 !-52775

4>

52

0

29-335

1.49

31335

33-335

35-355

1.80

37-335

39-335

41-335

2.10

43-335

2.21

44-335

2.26

45-335

2.31

46-335

2.36

47-335

2.41

48.335

2.46

49-335

2.51

5°-335

2.56

51-335

2.61 j

52-335

2.66

f 2.000000
( I. OOOOOO

0

42

14.394

25-376

16.358

17-34°

—

18.321

i9-3°3

20.284

—

21.266

—

21-757

—

22. 248

—

22.739

—

23.229

—

23.720

—

24-2 1 1

24.702

—

25-193

—

25.684

—

r O.981625

TO

3

<

1.44

i-73

2.O3

2.13

2.18

2.22

2.27

2.32

2-37

2.42

2.47

2.52

2-57

j O.4908 1 2

<1

32

When the mean temperature

of the column of air to be m

leafured is at 320, the differences of the logarithms give the real height in

fathoms and i-oooth parts.

ol

1-39

1.67

i-95

2.05

2.09

2.14

2.19

2.24

i.z 8

2-33

238

2.42

2.47

.

e 4

22

I3-852

H-796

15-74I

16.685

—

17.630

i8.575

I9-5I9

20.463

—

20.936

2 1 .408

—

21.880

22-353

22.825

—

23.297

23 769

—

24.242

—

24.714

1 O.47225

£ 1

i-33

1.60

1.88

1.97

2.01

2.06

2.10

2.15

2.19

2.24

2.28.

2*33

2-37

l O.94450

12

J

2 J2

27.162

29.014

30.866

32.718

.34 569

36.421

38.273

40.125

41.651

41.976

42.902

~

43.828

44-754

45.680

2.17

46.606

47*53 2

48.458

| O.925875
11-85175

I. Compu-

f

l J}y Means' of nt///i7>cnr ca-fire/sing f/ic

oo ^ ^ ^ | f1 £ a ^ 1° ^ ® ^ J?/g?r&y of Fahrf below gitf# an/ivering

gSP 4* fe 8 5 '« 8 «• S i & 8 g £ o S> U S S> g ¥ § 3 t £ S B S I '? ^ 5 £ ■$■ % 3 g g 8 \ ^ g g. a “ 1 aeryjiUfiarh ?/ a.r^mtionjirjh^ir,

• • ’ • * * * '■ * • • ••••»••• V, tfie unequal <j cult trt ay be divided .

‘Ilotf

Gun-wharf of
Woolwich-warren,
and upper ftory of<
Shooter’s-hill inn,
444

i if i ns

in ' in '» . ml

a,

&

f

I

I' ■

i* it mm * nil $ 3 s i* ir j s® i i i & j

a b} k & 1 1 *fc Ifl! ¥t # i? 4 1 'j

^ H iniu i K TETC WTWl i iWt

s

1 ,

p

Yf

41* $£ o

“J? 13 8

o va
>

III II 8 III III ill ill! III! Ill 1! Ill

Obfcrved heights
of th. inferior
and fuperior ba-

a « m H S-a ££ 33 — S.S - as &S H £S U. ““ S& »£ m *5

Temperature of

U H U U H U ii si ii 8= ii-rii It II i= ii i= is. it M i= ii

Equation for the

>S«S ££ sS
g-S 8

O0 CO - Ux

1 ii it ii %m ii if n ii p |t it ii i inm ii-ii

wa

IT:

f T ¥ T T T.f T T T 1 T 1 i T T i T 1 1

Logarithmic
refult in feet.'

ill ill ill hi it | ill ill ill nV ill ill ill nl n+ ill ill ill nl nl nT ill iT+

H Is ?i »■ 'tr es H zt Jr? H 12 it z? zi zz zv -iH zz ® 1

Logar. excefs
or defeft in
ft. and alfo in
iooothparts.

££ i- H s& H ££ *p ££ H, &S E& EE ££ £3

II

1

J. 8. £ 1. £ ° a. $ I £ t ° I £ « a ¥ £ * - I |

F

11+ H+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ III II + . II + 11+ 11+ II +.11+ 11+11 +

hh ii tl ** 1? If If tZ 2Jr -g> zs ti t? p^ & ** 22 -*■. g.il?

EST„li;ih

■ s.“aalfo

! 1 1 I I !.!!!!! 1 ! ! ! !.! till t

rf

ni

.

e

J *

! 1

i i i i i ii ^ i i i i i i i «g i J & i

i i i i i i Z i i 1 1 » i i bs i i _£ i

1

: i

i i n .: :."i:

a?

1 II !

Ratio of. the

Yver to° a?r“,ICaii
being.

N° I. Computations of barometrical obfervations made on heights in and near London.

N° IV.

Mean of the obfervations on Tinto, with Mr. de luc's eqt
for the air, — — _

Station at Weem,
and top of Weem- ?
craig, 700J feet. J
Ditto ftation, and ")
top of Bolfrack’s
cairn, 1076*- feet. J
Ditto ftation, and 1
top of Dull-craig, h
1244? feet. J

Ditto ftation, and 'j
top of Knock- farle, f
1 364s feet. J

Ditto ftation, and')
that in Glenmore, >

1279s feet- J

Ditto ftation, and q
South obfervatory on }•
Schihallien, 2098 ft J
Ditto ftation, and f
Weft furnmit of J
Schihallien, 328 1)
feet.. [

Station inGlenmore, r
and the South obfer-J
vatory, 818 76. (.

The obfervation
equation for th

Level of the Clyde
at Lanark Bridge,
and the ftation at'
the garden, 362*
feet.

Level of the Clyde, "j
and Stonebyre-hill, j

Carmichael-well, .
and Weft-end of .
Carmichael-hill,
45*1 feet.

Carmichael-well,
and top of Tinto,
four feet below the '
furnmit of the
Cairn, 1642.5 ft.

S,i

rt\

f

r

1

s. 1 si 1 ,J I. |i-§ f f f i 1 j *s ! ! 1 ! ? f 3 i!N

i H K ’ t { t lit ; ; : 5 a ,t !.J JDS R’S

1

1

F

f

i

I

‘H^s si w « s»s -s-s « ^ -s-s s-iT-ss •; M sa er; s 4 ats kjs

it it at fi u b at n « n n «hh 't a* 5? is u =-» ss if ig st

Obfervcd heights
of the inferior

3 -0 53 33 H ££.8* ,t> bb n p B *£ *£ g H *2. B 3> 2*2®

Temperature of

II It II il ia II II II II II II II li 1! 's II ii tl il II ii it Mil

Equation for the
heatofthc-quick-
filver. ^

si it 11 a 11 11 a s 11 11 11 a 11 11 i j a a it a g g s an

p

53-

+

to

1 f Ilf I ! t ! ! I ! I i I fill 1 ! 1 i 1 f

to r-

' 1 ^

iT TT 11 1 nT 11 1 11 1 11 1 VT 11 1 V7 11 1 11 1 11 1 Vi s f ri VI n i Vi 11 1 Vi Vi VT Vi

%l H H It Vr 2s tt £2 tt tl ti p. *. $fi $| if 1?'??

Logar. excefs
or -defeft in g.
ft. and alfo in D.
1 oooth parts. 0

j ~ HL SS Lv k53 £& kb ti; ££ H »» ~ ■&>«; t% '|>s 3 s g'g

'If

i jj

- a a « * £ a * 4 * 1. - “ » g .* s a, 3. .a a - a $

f

ii + i

H 2

I+ H4- 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+ 11+41+ 11+ 11+ 11+ 11+ 11+11 +

it p n n ft p 1? n-n i* 22 p it i? 22 ?* h Is 1? f?

parts, .datfo

i 1 1 1 j I i_i 1 u .i i_j j 1 1 m 1 11 j T

d

tt

-1

r

t 1

- i i i i t i i i r i

1 1 - P' 1 till 1 w 1

. £ . . t - 1

'J

1 1 S ' ''Si ' t ■ i. 1 i I 1 , + . 1 +

* • . “i i i> , * i S S S “ -S' ■ “ ' r

?lir

— « — • — 7 — r

2 t B ? 1 1 p & si £££.£*?£

Ratio of the

safj'jfit

[ 775 ]

N° II. Computations of barometrical obfervations made on heights near T^ybridge in

and N° III. of thofe near Lanark.

*

.

■v 4 I r fl

:

.

Leith Pier-head, and
Calton-hill,344feet.-

‘Was]

LefthPkr-head^and
Kirk Yetton cairn, f

Cafton-hiU*andKirk- -|
Yetton cairn, 1200 f
feet. J

Level of Hawk-hill
ftudy, and bottom
of Small-rock, 7.4 ,
ft. below the top of
Arthur’sSeat, 702.4
feet.

Bafe of Hawk-hill

sirs a.

Small-rock on
Arthur’s Seat, 684

Hawk-hill garden-
door, and bottom
of the rock on Ar- ,
thur’s Seat, 730.8
feet.

In thefe two laft 0
for the i

s

g

s

s

t

If 1 iMUniNJ W & 9 1 1
%l 1 g? t i 2. I? S i g? & $ is it g* h

ff 5 \ 1 l * £ •=- H t \ H i* n n *'

k % ? = .2 3. § % * S £ S ^ S-S 5-2 & 0,

J

1

8

J s 11 it it 11 11 i s n i a « a. 1 s a si

Obferved heights
of^the inferior

-i- -a is ss it H U l.i H «» H H 81 88 &_

Temperature of

| »€ II ii II =i II II II II II ! I II il II II il ii

. Equation for the

! ’ is it » tt ii 1 1 si it a a it -» a is si a

W'at

! ! TiiT 1 T 1 ii ? 1 ! T » V T i

Logarithmic
refult in feet.

1 t 5 11 11 3 M 3 f 1 rt f? s :: s ii s 5 11 8

Logar. excefs
or defeft in
ft. and alfo in
1 oooth parts.

* f 2 5 ; 5 2““ 2 252225ES 2

n

];|

1 P a & l t » ~ i & l I t 1 - E & £

f

n+ nt 11+ 11+ 11+ 111 11+ ii| ii| 11+ ii| ii| hi 11+ 11+ 11+ 11+ 11+ m +

tt ti H Zi ts F tz ts F II <S£ ^ P F F F s§:?

"TSSM

fnfeSe,andalf°

I I ! g ! .1 ! ! f# I I I i 1 r | | !

4

■1 1
. . ^
g-

j I-

1,1 ‘S' « 1 1 & 1 1 1 •g ' 1 1 , ' 1 £ '

1 ' f \ £ i . 1 1 £ . . .S' ' > ' ' .S'

1

i I : :* ; : : :i: : : t : i i i ■ :i :

ill

1 1 1 1 1 1 ! 1 1 I- ! ! ' i 3 1 4

Ratio of the

sa^rt

being T.

P mm

am mm

It S KiS Hi m

If £1 irk?*?*- #!?• Hi

W

S

If

II

if I I

f f

I I i

l If f f

* S ': H

£ ^

I | l-l irl

H. S. "*> H.

? Pin? u

i -- •- •- rn HI s.Hris *•?

r i S I a ti n it « t m

i t? ts' £% t's. n &§* && §• ss sj;

i i

iwwwwwwwm

i ii ii

i U3

ill

!!!'!!! : 111

II II I II I II I

5 n h n

ii i ii i ii i ii i ii i ii I ii l

s? h t! sf n t? ii

t II ££ £3 ££ ‘CS' $£ iff £§

r T

2. % * s S'

ii ii ii + ii +

i i i& fo

H + ii + ii +

» n Is

ii+ ii+ n+ n+

I ? |.j iH

I f 1 f 1!M ! : ! I I

1 1

IT

$

r in nl +1

s. rf fg Jl

\ ^ 3 3

? TTT

ii + ii + H + M +

U ■?£ % ¥£

ss •?& -s&T

g? is s

as £» stsi

Ii H

§

§S ^ §& H

? ..? S S «?

4>. 0^00

II I II + II + II I II I

C£ p S. *?

1 5 I

11+ II I 11+ 11+ 11+ II II II I II I

SS S£ £•” !* tl 4* P

i l ! ! ! ! I

r sr

I I

00 J*

n

mi

III!

I l ME

and N° VI. of thofe near

liotteft of the ordinary oblervations on the higheft ftations. Coldeft of the ordinary oblervations. Coldeft of the Sun- riling oblervations.

■ 5^

If If If If If If If If I* fp i» if |f If U ff If H H 1 =

■ f\

j

f!

i L

!'| I l!4 Hi 1

K i ?? K ^ R KUK-% & I

£ p £ £ -sp % N 5? ? ^

i i i f i ' f f f ! f f oT4

\ % $ % % l K ii k/k K ^

II
'f •

£S $$ fS H IS IS B WIi SI it Ji IS IS E 2

'SS gig g'S, -S& 8& &s t'S £ S S

4 11 If .11 1 II II !l II II H II

Oolcmd heights

H. SS ~S H S2 I- H S- H -£ -S SSL H S* SS "-a S* £§. ““ 4* S3 *3 *3 “°£ H S&

Temperature of

r M M Wjm Jl & H B S B U H U IF ii ii H 1 1 li iilTTi li li U U

Equation for the
heatofthequick-

1 1| If || If || |l |f || || !1 11 f| || |{ f| f

1 1! 11 ii It ill II #Ǥ?!

WiSffi

J ?• f ! 1 F T l H ! ! H | I I ? 1 i f 1 ! ! I t ! l

Logarithmic
vefutt in feet.

ii ^ hi hi hi mi hi hi hi hi ii 2 ii i hi n+ hi hi ni n+ n+ ii+ n+ ii+ n+ n+ n+ ii+ n+ n +

§~ S3 $*, s| S£ si 3? *8 ^ rf r« 2S pp oa + «« So rr pp yt ^

**> ^ CO -J io OJ OU4 -»•*■» 'JCOtn^t'JO OW oj tn VJ . o » NS Os In la In O' In O' » « oo -J la OS In O' St1 p

Logar. excels
or deleft in
ft. and alfo in
ioooth parts.

1 KI ^■8 BS 22 &g, yg ?3 gg ys 3S SS, a- 3- “1 “$ ““ f & “3 Sa “a S3 “3 Hs

tr

l!

-i

O. 2 Sat ~ £ ° g a £ &. 2. & £ % * 3 4 ° S 4 4.. 5

j

?| - s - s - a/ ^ « u g, a , & ; £ £ g js . s £ $h & 1 I i 1 i I

tr

i] + ii+ ii+ -11+ n+ n+ ii+ n+ n +. n + n+ n+ n+ ii+ n+ n+ n | ii 1 ii I ii 1 ii 1 ii 1 ii 1 ii l ii 1 ii l 11 1

^ PP ^ °° P?j 'I'r +* r p ’cv r r rr '?'? £* +V* + + ££ ^

W M M N s: io io C3 S3 io 5s fs KS » 5; 3 — — — "

f f s ! I ! ! ! I 3 ? ? ! ! 1 » ? 1 3 1 i ! ! f r 1 I

4

I

. *?•
i ^

.i

| | | | ^ -
+ O' M ii 1 ^ 1 1 1 1 | I 1 1 1 1 1 1 [ 1 1 1 oo 1

l}

+ + + + , + , + + + + + + + +, I + II++I + I

1 £ i ' 1 . str*-t>sr

mi.

I 1 i 1 III illilillllit till

Ratio
freight o

^ >•

of the
f quitk-
air, air

Computations of part of Mr. DE luc’s barometrical dbfervations, anfweiring to tire coldeft and botteft tern]

of the air:

fJfii mi m s sf

7\ is i *

F i

If if

sf

$ o

S'g,

ii +

fr

k f I

K

7% ?■ ? .ns E

Ss s § as 5

I’ f I f-

I

i

uo.

1

II

?

)

$

>• i

* ?

*3

s

O S

*&

%

1 1

!

+

j

II +

f f

p1

**

4

II

* a

F*
s ;
s »

§i
1 1

If

n

T

i:

ii

ft

- 3

^S*

»*S.

11?

I

ifiilfrtl!

J *1 ,i p P p J -i

** *. * F; II .fe £? K, I

-■ £ NN- NH N> » Q. 'P

t* -8

sH*

'll US

S ** S«8 J

S' 55 5; £S 1

3 1! 1! I

It 1 1 n |l

5 #Hf t

III HI If

gST g- 8, 8,8-

Si! I

I

— s

I i.

M!

? I , ft

$ 8

I

I M

£

r

ir

if

IS DfS

#

II Ii M IT

ii %i tt

T f T ff ff

S 4*

I

3f U 2* SS ^

+ «, + & *a, *a,

s£ H ^ £1

I

i s

1 t t

I! I II I II

•SB -4 >3

II I

II I II I

4

f|r

1

Logar excefs
or defeft in
ft. and alfo in

M i i | ii ii ii n ii ‘sa 4 ^ p.

Parti-

cular.

Temperature
of the air,

a a W - - s - a 1

1 1 3 St S .2 .5s % o qo

I?

11+ II + 11+ II. + 11+ 11+ ill + 11+ 11+ 11+ Jl +

5? P | «| J| ||- f p. fl #| #? If |5!S

%u«hm by the

1 ! 1 4 f ! ! ? ^ ! 1

4

Refult by the rule.

1 1 ft 1

r.

— 16.
Mean

+ o.6

trror
of the
rule in
feet.

1 1,1 1 1

Ratio ot the

jStSJft

Continuation of Mr. de luc’s barometrical obfervations.

[ 78s ]

Computations of barometrical bbfervatlons made on heights that have ndt been determined

geometrically.

|.|J

■8 S

a 4

|i

U =

Temperature

«.S5

g

Pate.

J.1-2

jJ

III

’iJi

.a .S

of the

air.

jj

-•s'!

meters.

1:11

o°gs

is*

§1

H

•g° .
if ° “

1

Parti-

cular.

Mean.

.1“ 8^

•g-g 1

lil

r

Level of the fea at Inver- 1

29.932

54°

—072

19.860

| 181.3

/ 54° 1

- ,° jr

+ i

191.1

gourie, and Belmont- r

29-734

57

— 081

29-653

1 54 }

54 {

=9-8 f-J

io?

1

caftle. J

y

1773' Juh 8-

f

L

Superior barometer, 1
Top of Kinpurney- ]

29.988

28.974.

6s

62

—108

—095

29.880

28.879

} 8S7.9

(in

6° |

951-

2!

1776, Sept. 12.

{

hill.

Ditto. |

30331

29.27s

S6|

51

—080
— 061

30-251

29.214

} 908.9

if}

53? {

&.}

955-3

959-7

2*

{

Caftle Menzies. {

29.756

29.674

60J

64!

O92

IO4

29 .64
29.570

} 82.7

U)

62 {

±?u

88.8

28f

Sept. 11.

i

1

a

Top of Farragan. j

29.794

27-344

631

52|

— 102
—062

29.692

27.282

1 2205.8

Ut]

57l{

+62.4-1

=137-8.;

2343.6

29

Sept. 17.

{

1

Top of Ben Lawers. j

29.800

25.830

SS

S8

—075

-017

29.725

25-813

J 3677-

ui

45 {

+30. i

=uo. ;

3787-

42

{

Top of Ben More, j

30.000

26.148

SSi

42

-077

—029

29.923
26. H9

} 3542-9

isin

44? {

+3r-0]
=109.8 ;

3652.7

53i

Sept. 12.

{

0

3

Top of Ben Gloe. j

29.712

26.142

62

48

—097

— O4I

29.615

26.101

} 329i-3

nn

53! {

+ 5i- 1
=167.9;

3459-2

27}

Sept. 13.

{

c

Blair of Athol-lawn. |

29.636

29.380

60

58

=31

29-545

29.297

J 219.6

{ lo|}

S9h{

+ 67. 1

= 147-7 J

234-3

3°

Aug. 22.

{

h

Top of King’s Seat, j

29.904

28.791

68

66|

— 116
— 108

29.788

28.683

1 985.

J

651 {

+ 84.3 1
=83- J

1068.

6|

1775, Sept. 5.

{

Hill of Barry. j

29.870

29-343

62

56

—098

—076

29.772

29.269

J 444-

{*}

*■!

+64. -1

=28.4 j

4724

4i

Sept. 5.

{

Dunfinane-hill, j

29.784

28.913

62

59

—097

-086

29.687

28.827

| 766.

1 s-}

6of {

+ 7*-5 \
=54 8 ;

820.8

H

1 774» Aug. 29 and',
30. mean of three L
obfervations. J

Quay at the new bridge ->
of Glafgow, and ftation J>
at Lanark. J

29.560

28.850

55?

sh

—077
— 066

29.483

28.784

J 625.2

{ !H}

« {

+50.0 -i
=32-3 ;

656.5

22|

1772, Aug. 6.

2h f

Freeport in the illand of-.

•

P.M.

J

Ilia, 19 feet above the 1

30-224

67

—1 14

30.110

| 2300.2

r 60 i

581 {

466.3 1

>772j Sept. 25.
25' A.M.

1

fea, and fummit of the f
South-pap of Jura, J

27.642

57

— 076

27.566

i 57 }

=152.5;

2452.7

4i

r{

Hafniford in Iceland, at-,
the fea fhore, and fum- l
mit of Mount 'Hecla. J

29.859

24.722

'?■

— 056
— 016

29.803

24.706

j 4886.8

U)

33l {

+ 34 1
=16.6 ;

45b3 4

76

Cbmpti-

I 7*7 3

Computations of Mr. bouguer’s obfervations in Peru, fuppofing them to have been made at correfponding times, and in the
mean temperature of the day, between the coldeft of the morning and hotteft of- the afternoon.

Stations

of the baro- j

meters.

, with their •

Relative heights of the. Rations,
with reipeft to the South-fea,

geometrical diftance -

in feet

15833 ]

[ South-fea',
[ Corajon,

Heights of the columns of

. ^564 •

r South-fea,
[ Pichincha,

air. whofe bafes Rood at *

the fea,

r South-fea,
9374>| Quito,

7840

r South-fea,

[ Carabourou,

is 6

'Cora^on,.

L5833 1

7993'

r Carabourou,

Carabourou,..

7840 J

[ Corajon,

!|

Pichincha,

Carabourou,

15S64 1

7840]

7724 •

r Carabourou,
[ Pichincha,

f -J

Cora^on,

>5833 \

6459

r Quito,

■6 'o

Quito,

9374]

[ Coraypn,

11

Pichincha,

Quito,

15564 I
9374/

6190

f Quito,
[Pichincha,

Mean of the l

four fuperior [

l-s1?

columns, J

sl’S-s

Quito,

9374]

1534'

f Carabourou,

3

SO

.Carabourou,

7840 /

[ Quito,

SS A

u. c

£Jt

2 A
“1

I-s •

an heights
of the
rometers.

.a s

'B-S.S »

u 1

- J!.Sg-

-g 0

4>

Ratio ’

of the

iS!|

sl

ft

p

1 •§«■

! II-

J s

: S S.

“S -0 -s

!:?§

ft

§ 2

Equation for
heat of the
in 1 oooth pa;
and in feet.

fS

O

O 2

weight of quick-
filver to air,

SU

1 3

S3.
§ 2-3

w

Particular

Mean.

29.930

16.808

841°

43/

— 169
— 022

29.76!

16.786

} 23-27

14922.

J 64°

/

l =919. ft.

j 15841.

+ 8.0

14590 ■)

14553

16.963

84/

44/

—024

29.761

16.939

} 23.35

14685:6

r —878.4
| = 60.

} 64/

r + 62.

[ =920.4

1 15606.

+ 42.

14517 J

21.403

841

651

—078

29.761

21.325

}, 25-54

8685.5

r —688.5
1 = 80.

} 75

r + 90.
1=781.7

f +96-5
1 =698.7

} 9467-2

+ 93.2

13273-)

13120

22.625

841

661

— 084

29.761’

22.541

J 26.15

7240.5

{=T3:5

} 75/

} 7939’2

+99-2

12968 J

—

661

43s

—

22.541

16.786

J 19.66

7681.6

r— 3H-4
l = 4° 5

}55

/ + 35-a

l =274.4

} 7952.

—4i.

16623 -v

16565

—

66i

44s

—

22.541

l6-939

} 19-74

7445-1

f -278.9
1 = 37-3

} 55/

{ + 3'6.5
l =271.7

} 7716.8

- 7.2

16597 J

' —

65I

43/

21.325

16.786

} I9-°5

6236.5

T —222.5
l = 35-7

r— 189.9
1= 31-6

} 54/

/ + 33-2
l =207.

} 6443-5

— 1 5-5

171491

17021

_

65!

44/

—

21-325

*6*939j

} 19-13

6000.1

} 55

f + 34-
l =204.

J 6204.1

+ 14. 1

16893 J

_

36.J

55

16793

—

661

65/

22.541

2I.325I

} 21.93

1445-

r— 89.

[ = 61.6

} 66

r + 61.
1= 88.

} 1533-

I.

15089

dent*

*

r/u/,lsT,tlos.v,,//,xvi/.T,,/,^Kvnr.p.708.

GE OME TRJ CAL OPER A TIONS

The D afe AB , situated on ^perfectly levdTlaih^as meafired Grice in
contrary directions, be/ween theD arracks ofAbcrmcnai and t/re bottom
ofDmas Di/lflc , an ancient Dnti/h fortification, on the Sea- Sho/r .

The length ofthcJron (Train made use of on (hit occasion am* ascertain'd
by means of accurate Deal Hods, applied, to it everyAforning ( YTrcnin g,
before and a/ler the operation of the Field . The two measurements agr-
eed to within iff than a* Toot, and made (he length- of the Dase —
jjojtrT ThisDase AB f was aflerwards prolonged to C , the Top of
the Dinas bp means of the side DaseHY 411 y fid . Thus the di/lancr
BC , being 482.2 feet/ the tota/ fase A C amounts to 14J6 8 2 feet .

~R,Aigh Watermark Heap Tide . J) . a small JEminence called the Di-
god , T, the Toot JIM of Carnarvon . S , The Teak of Snowdon . J5 , A
Cairn of Stones on Jfoel Tilio .

Thefatitude of Carnarvon was found to be S3 -A 4 7 > tmd the Va-
riation of the JVeed/c, by two Azimuths of the Sun, taken on the zjfof
Aug*, at 2.2 and .fir. T.Af. 22. 18. 30 we/lcrly .

The FTeight ofhfoel, T ilia above Carnarvon tfu/i)' 2371 Feet, result-
ing from the simplest operation on the Digod, the nearest point to
the Adi, is to be preferred to that deduced from the Angles ofT/eva -
turn taken from A .

Angli

Triangles

DEB ana DAE
For t/te dfrfanc y
Moci Fiiio from
Hand A. .

CAT ,/ort/u-
di/lancr o/ thr
TootJTM frvmA..

Angles

For t/d I \

from C Hep S' ro.04.zO || . Altiludt gf j )

S no tv don I

above Hand the |

Sea at Carnarvon}

am. The time not admitting of any actual Survey of the Environs of Carnarvon CfSnowdon to be made .theVtan is only V

to be consider'd as a flight Sheitir attended merely to convey a general Idea of the nature of the Country where the Triangles nerr/Uurued .

and 1 j
Deprefrioni

\ j

Relative Heights-

Tor the ~
^Altitude of
Snore doll
above Yt arrdU .

5 above B Trigonometricall)'
r/ure CSjRe/raction- ....

Aright of the Jnftrumrnt . .

5 above'H

C above's TYigZ- 07-8

Inflrume/rt, ..4A

C abovcJS tor -0

C abovclSTrigC rJ4 • 8

Tnflrumenl .4.6

above tf *00-7

J/cnce HaboveH

Sjtowflon above- the Sea atTS

8 above D TrigC

Curvature CP Re faction

Inflrument

6 above D ..

D above Forth Angie of
Carnarvon (Tuny bydeveffd
fertuat Srpa/irr ofthrBanmte/rrj
(tuny above High Water tPTide
Snowdon above the Sea 3se«. 7\

38fP£_

JJJf'. J

17- ‘
338), ■

Relative Heights"

((

Tor t/ie Altitude 1

E above D TtigC

Curvature CP. lie fraction ...
lttflrument

218s ■ 8
1C. 3

4- c

ofMoel Tilio \ j
above D , and (

( E above D

1 D above far nan- ore Ouay

XZ047

id 6. 3

the Sea, at I1

Carnarvon . 1

Vertical defiance otBtuvm-7. .

Ouay above Meap Tide,

( Mod Tilts above the Sea- . . -

28 7c 0
13

l

*384.
2331 ■ 6

£ / ve A Trig '

1

! Curvature C "Refraction ....

Tnftrurncnt

1 effort Tilio above A

ty.i

4-d

13 da- 3

Tor the Altitude 1|
vfMoclTilw I
above A, a/rd <
the Sea at
Crmari'on .

1 T above AJrtgC -

\ Curvature & Refraction

tnfn/tnent

\ T above A

T above Carnarvon Ouay .

178.6
46
4.6

187.7
16 6. a

\ Quay above A

i Tlencc the /'ertieal di/bmee I
of the Barometers f

M. x/Tibb a hot cJVeap Ade.^

*384-*

||

Sarirr Sndp ' .

P L A I

OF THE

Triangle s

■ made up o/p/r obtaining

the Geometrical Diltance and Altitude
Op SJVO PfA) OJST mufMOEL Eizio
lord/ n/pect to /tie Sea aP
C A R J\r.A R VO JV .
Augfiygs.

Scale of Teet .

[ 789 ]:

XXXV. Account of a new Micrometer and Megameter
By the Abbe Bofcovich,

Read June ? 9, T_TAV ING heard that the Abbe rochon
■*i •*" had exhibited a kind of micrometer,
which, by means of a prifm of rock cryftal whofe angles
could be varied, gave two images of the fame object, and
changed their diftances by the circular motion of one of
the two parts which compofed it; I told fome of my
friends, and among others the celebrated Abbe fontana,
that I faw very well how the thing was done ; but that a
confiderable improvement would be made in it if the dif-
tance from the prifm to the focus of the eye-glafs were

made -

Memoire fur un nouveau Micrometre et Megametre. Par Mr
1' Abbe Bofcovich, DireSieur d'Optique de la Marine.

OUAND j’ai feu que M. 1’Abbe rochon avoit fait voir une efpece de
micrometre, qui, par le moyen d’un prifme de criflal de roebe a angles
variables, do'nnoitdeux images du meme objet, et en cnangeoit les diftances par
un mouvement circulaire d’une des deux parties qui le compofoient ; je dis a
quelques-uns de mes amis, et entre autres au celebre M. l’Abbe fontana, que je
voyois bien comment cela fe faifoitj mais qu’if y auroit beaucoup pins a ga-
gner^ fi Ton rendroit variable la alliance du prifme au foyer de la lunette: j’ai
3 ajoute .

79° Abbe boscowich’s Account of

made variable. I added that the fame effect might be
produced without the double refraction of the rock
cryftal, with a prifm made of common glafs, only fmal-
ler than the aperture of the objedt-glafs. The rays
which pafs through the prifm would then form an image
which would be feen out of its natural place; and thofe
which pafs without would give another image, in the
fame place it would have appeared in, if the prifm had
not been there.

A few days after, the Abbe fontana was told, that
the Abbe rochon had thought of another micrometer
with a prifm of rock cryftal, which, approaching more
or lefs to the focus of the objeft-glafs, had the advan-
tage of producing a very great effeft, and might be
achromatic; that having accordingly had his inftrument
executed, and made leveral obfervations with it, he had
prepared a paper on the fubjeft, to be read at the next

meeting

ajoute que Ton pouroit avoir le memc effet fans la double refraftion du criftal
de roche, en faifant un prifme a verre fimple, mais plus petit que Touverture
de Fobje&if. Les rayons qui paffent par le prifme, formeroient alors une image
deplacee defapolition naturelle, et les autres q\*i pafferoient dehors, donneroient
Fautre image, ala meme place qu’elle auroit, s’il n’y avoit point de prifme.

Quelques jours apres on a annonce a M. fontana que M. l’Abbe rochont
avoit imagine un autre micrometre a prifme de cridal de rocne, qui, s’ap-
prochant plus ou moins du foyer de Fobjeftif, avoit Favantage de produire un
effet tres grand, et de pouvoir etre acromatique: qu’ayant fait executer fon
inftrument, et fait avec lui plufieurs obfervations, il avoit prepare un memoire

fur

a new Micrometer and Megameter. 791
meeting of the Academy. This the Abbe fontana im-
mediately told me, and I repeated what 1 had laid to him
the firft time on the effedt of this micrometer; adding
at the fame time the precife meafure of the fcale for the
meafure of the fame effect, and the facility of obtaining
the fame thing without the rock cryftal; mentioning
likewife other advantages which might be derived from
the common glafs prifm not covering the whole aper-
ture of the objedt-glafs ; and, amongft others, that of
being able to meafure much greater angles by this means
than by the double refradfion of the rock cryftal.

The Abbe rochon did accordingly read his paper to
the Academy, and mention has been made of it in the
public prints : he has therefore the merit of having thought
of the fame thing, at the fame time with, or perhaps

before

fur cet obiet, pour lire a la prochaine feance de l’Academie. Mr. I’ Abbe fon-
tana eut la bonte de m’en avertir immediatement; ce fut pour lors.que je lui
repetal ee que j’avois eu 1’honneur de lui dire la premiere fois fur I’efFet de ce
micrometre, en y ajoutant la mefure precife de 1’echelle.pour la mefure du meme.
effet, et la faciiite d’obtenir la meme chofe fans le criiiai de roche, avec d’autres
ayantages que l’on pouvoit tirer du prifme a verre fimple, ne couvrant pas toute
1’ouverture de Tobje^lif, et entre autres celut de pouvoir mefurer par ce moyen
des angles beaucoup plus grands, que par la double refraction du criitai de
roche.

M. l’Abbe rochon a reellement lu a TAcademie fon memoire, et on en a fait
mention dans les gazettes: ainii il a le merite d’ avoir imagine la meme chofe.

792 -Abbe boscowich’s Account of

befoi'e me, without any knowledge whatever of my ideas
on the fubjeCt; he has been the firlf who announced it to
the world, who had it executed, and who made ufe of it :
I have thei'efore no pretenfions whatfoever on that head ;
he has the merit of a great dilcovery, and aftronomy has
the foie obligation of it to him.

But the Abbe rochon has only made ufe of the dou-
ble refraction of the rock cryltal for his micrometer, and
I am allured he has faid, that his prifm could give him no
more than fix degrees. Now it is well known, that pieces
of rock cryltal, large enough and pure enough for thefe
purpofes, are extremely rai'e; befides, the difficulty of
working them is great, that fubltance being harder than
glafs, and requiring the utmolt attention in cutting, in
order to obtain the difference defired between the two
refractions. I think therefore, that it will be doing an

effential

dans le meme terns, pent etre avant moi, et abfolument fans avoir en aucunecon-
noifiance de mes idees fur le meme objet ; de 1’ avoir annonce le premier au public,
de 1’avoir execute, et de s’en etre fervi le premier: ainfi je n’ai rien a pretendre
de ce cote la: il a le merite d’une belle decouverte, et l’afironomie lui en a
toute l’obligation.

Mais M. l’Abbe rochon n’a employe, pour fon micrometre, que la double
refraction du criftal de roche; et on m’a afiure qu'il a dit, que fon prifme ne
pouvoit lui donner que jufqu’a fix degres. On fait bien que les pieces afiez
orandes de cette matiere, et afiez pures, font tres rares; outre la difficult^ de la
travailler, etant plus dure que le verre, et quelle attention il faut avoir pour la
bien couper afin d’avpir la difference des deux refraCtions que Ton veut. Ainfi

a new Micrometer and Megameter. 793
effential fervice, to propofe another micrometer of com-
mon glafs, to explain the theory of it, and to extend it to
much larger angles, which may render it applicable to
the optical instruments made ufe of in the navy, in taking-
geographical latitudes and longitudes.

I had already made a prifm of this fort, and Ihewed
the Abbe fontana its effecit for the double image of the
Sun on his excellent little achromatic glafs : the two
images were procured by applying this prifm to the ob-
ject-glafs with the hand, in fuch a manner that it covered
only one-half of it : pufhing it more or lefs forward, occa-
fioned a change in the brightnefs of the light of the two
images, and fhewed that they might be made equally clear.
By changing the inclination of this piece, the diftance be-
tween the two images was varied, which did not alter

when

je crois rendre un fervice encore plus conftderable, enpropofant cette autre efpece
de micrometre a verre limple, en developpant fa theorie, en Tetendant aux
angles beaucoup plus grands, ce qui donne le moyen de l’appliquer aufli aux
inftrumens d’optique, que la marine doit employer pour ebferver les latitudes et
longitudes geographiques.

j’avois deja fait faire un prifme de cette efpece; et fis voir au meme M.
l’Abbe fontana fon eftet pour la double image du Soleil, fur fen excellente
petite lunette acromatique : on avoit les deux images, en l’appliquant a la main
fur l’obje£tif, de maniere qu’il n’en couvroit que la moitie. En le poulfant
plus ou moins avant, on changeoit la vivacite de la lumiere des deux images, ou
Ton voyoit qu’on pouvoit les reduire a une clarte egate; en variant l’inclinaifon
de cette piece on varioit la difiance des deux images, qui n’avoit aucune varia-
Vol. LXVIL ' 5 G tion

794 -Abbe boscowich’s Account of

when its diftance from the objeCt-glafs was varied with-
out the glafs. This piece was a common prifm, which
gave a refraction a little greater than the apparent dia-
meter of the Sun : I added another to it afterwards, of
the fame kind and equal, both of them having circular
bafes. Turning one of the two parts upon its axis, will
vary the angle from o, to double each in particular, which
occa lions the two images to approach to, or recede from,
each other. A much flower variation is obtained by the
greater or lefs diftance of the prifm from the objeCt-glafs ;
but there is a particular reafon for which one cannot give
it too large a one, the contraction of the pencil of rays
belonging to each point of the objeCt, not allowing that
diftance to be very great, for fear of weakening too much
the direCt image towards the middle of the field, by the

inter-

tion en changeant, hors de la lunette, fa diftance a l’obje&if. Cette piece etoit
un feul pFiftne limple, qui donnoit une refra&ion un peu plus grande que le
diametre apparent du Soleil : j’y ai fait ajouter apres un autre femblable et egal ;
l’un et l’autre ayant les bafes circulates: en tournant fur fon axe Tune des
deux parties, on variera l’angle depuis zero, jufqu’au double de chacun en parti-
culier, ce qui fait approcher et eloigner les deux images entre elles: on obtient
une variation beaucoup plus lente par l'eloignement plus grand ou plus petit
du prifme a Ifobjedtif; mais il y’a une raifon particuliere pour laquelle on ne
peut pas lui en donner un trop grand; car le retreciffement du pinceau de rayons
appartenans a chaque point de l’objet, ne permet pas de l’en eloigner trop, ce qui,.
versle milieu du champ, aftbibliroit trop Fimage dire&e, eninterceptantune trop

ffrandc.

o

a new Micrometer and Megameter. 795
interception of too great a part of the fame pencil, which
in the end would occafion its being altogether loft.

I have in hand, making for me, a rude machine in
which one of the pieces may be turned by the hand upon
its axis, to make the diftance between the two images
fomewhat larger than that which is intended to be mea-
fured, as for inftance the diameter of the Sun ; and by the
help of a moveable fcrew, one may carry the prifm, thus
compofed, to a diftance from the objedt-glafs, by a motion
fimilar to that of the fmall mirror of the telefcope. 1
have had it adapted to an ordinary glais of about four
feet, w'here its effect, for the Sun’s diameter, muft be
much greater than an inch of motion in a minute ; for the
other planets one may have ten or fifteen lines in a fecond,
or even more. Generally the fcale is the whole length of
the glafs for the total refradlion of the prifm, which like-

wife

grande partie du meme pineeau, et a la fin la feroit perdre totalement.

Je fais faire a&uellement une machine grolfiere, dans laquelle on peut tourner
une des deux pieces a la main, fur fon axe, pour rendre la difiance des deux
images un peu plus grande que celle que Ton veut mefurer, comme du diametre
du Soleil ; et a Faide d’une vis de rapel, on peut eloigner le prifme, ainfi compofe,
de Fobjedtif, par un mouvement femblable a celui du petit miroir des telefcopes.
Je Fai fait adapter a une lunette ordinaire de pres dequatre pies, ou fon effet, pour
le diametre du Soleil, doit etre de beaucoup plus d’un pouce de mouvement par
minute; et pour les autres planetes ou peut avoir 10 ou 15 lignes par feconde,
et plus encore. Generalement Fechelle efi toute la longuer de la lunette pour

5 G 2 la

796 Abbe boscowich’s Account of

wife is the cafe in the Abbe rochon’s prifm, for the dif-
ference of the two refractions. But one may vary the
angle by applying the prifm without the glafs near the
objeCt-glafs, and turning one of the parts upon its axis.
In that cafe, the fcale of the excefs of the fum of the re-
fractions of the two parts of the prifm above the difference,
will be in length no more than half the circumference of
a circle, though the circle may be made as large as one
pleafes ; but the difference of the diftance of the images,
will not be proportional to the difference of the arcs run
through by the index. In order to determine the relation
which the motion of the index bears to the variation of
the diftance between the two images, one muft have the
folution of a geometrical problem, which is eafily gained
by fpherical trigonomety ; but it will be always better to

deter-

la refraction totale du prifme, ce qui eft le meme pour la difference de3 deux
refractions dans le prifme de M. TAbbe rochon. Mais on peut varier Tangle
en appliquant le prifme hors de la lunette, a cote de TobjeCtif, en faifant tourner
une des deux parties fur fon axe. Alors Techelle de l’exces que la fomme des
refraCtions des deux parties du prifme a fur la difference, n’aura pour fa longueur
que la demi circonference d’un cercle, quoiqu'on puiffefaire ce ceixle aufti grand
<iue Ton veut> mais la difference de la diftance des images ne fera pas propor-
tioned a la difference des arcs parcourus par Tindex. Pour determiner la rela-
tion du mouvement de Tindex avec la variation de la diftance des deux images,
il faut refoudre un probleme de geometrie, et j?en ai la folution bien linrple par
ia trigonometric fpherique; mais il vaudra toujours beaucoup mieux determiner

ce

a new Micrometer and Megameter. 797
determine this relation by an atftual terreftrial obfer-
vation of a divided ruler, obferved at a given diftance.

When the angle happens to be a large one, the co-
lours would naturally be fuch as would greatly deform
one of the two images of the object, namely, that
given by the rays that pafs through the prifm ; but this
is eafily remedied, at leaft in a great meafure, by making
each prifm of two pieces, one of common and the other
of flint-glafs. One may multiply the compofed achroma-
tic prifms with variable angles by making the one give
degrees from 5 to 5, or from 2 to 2, and the other the
minutes. One may put two on the outfide near the ob-
ject-glafs, which u7ill change the diftance of the images
by the circular motion, and give the angle required a
little larger than the real one ;; and another within which

will

ce raport par une obfervation a&uelle terreftre d’une regie divifee, et obfervee a
une diftance donnee.

Quand il s’agit d’un grand angle, on auroit des couleurs qui deformeroient
beaucoup une des deux images de Fobjet, c’eft a dire celle qui eft donnee par les
rayons paftes a travers du prifme : on les evite aifement, au moins en grande
partie, en compofant chaque prifme de deux pieces, une de verre commun, et
Fautre de flint-glafs . On peut multiplier les prifmes compofes acromatiques et
ii angles variables, en faifant quel’un donne les degms de 5 en 5, ou de 2 en 2, et
Fautre les minutes: on peut en mettre deux dehors, pres de Fobjedlif, qui
changeront la diftance des images par le mouvement circulaire, et donneront-
Fangle cherche un peu plus grand que le veritable ; et un autre dedans, qui

donnera

798 Abbe boscowich’s Account , See.

-will exachly give the feconds. I have already thought of
the inllruments requifite for obtaining all thefe objects
with accuracy, as well as for the application of a variable
prifm to the common failor’s o chant, and have by me the
folution of the neceffary problems : this will be the ob-
ject of a wTork I am preparing. In the mean time I pub-
lifli this, to give others an opportunity of hitting on
fomething better concerning the mechanical conftruc-
tion of thefe inllruments.

donnera, avec toute precifion, les fecondes. J’ai deja imagine les inftrumens
neceffaires pour avoir avec exa&itude tous ces objets, comme aufli pour Impli-
cation d’un prifme variable a l’o&ant de marine ordinaire, ayant auffi la folution
des problemes neceflaires. Tout cela fera l’objet d’un ouvrage que je prepare
fur cette matiere. En attendant je publierai dans les differens journaux ce
Profpe£lus, pour donner plutot a tout le monde le moyen d’imaginer fur la
forme mechanique des inftrumens, quelque cliofe de mieux que ce qui m’eft
venu dans l’efprit fur ce fujet nouveau, et bien intereflant.

-

[ 799 1

XXXVI. Account of a new InJlrument for meafurin gfmall
Angles , called the priftnatic Micrometer. By the Rev.
Nevil Mafkelyne, D. D. F. R. 6V and AJlronomer -
Royal.

micrometer, for meafuring differences of right afcenfion
and declination: nor did it receive lefs advantage from
Mr. s avery’s moil ingenious invention of the divided
obje<fl-glafs micrometer, which has been rendered more
commodious by the late Mr. john dollond’s applica-
tion of it to the obje£t-end of a reflecting telefcope, or
the prefent Mr. peter dollond’s application of it to the
objeCt-end of an achromatic refracting one.

But, valuable as the objefr-glafs micrometer un-
doubtedly is, fome difficulties have been found in the
ufe of it, owing to the alterations In the focus of the eye,
which are apt to caufe it to give different meafures of the
fame angle at different times. For inftance, in meafuring
the Sun’s diameter, the axes of the pencils of rays, which
come through the two fegments of the object -glafs from

Read Dec. 18,

im-

R ACTICAL aftronomy was much be-
nefited by the invention of the wire

4

contrary

Soo Dr. maskelyne’s Account of

contrary limbs of the Sun, crolfing one another at the
focus of the telefcope under an angle equal to that ot
the Sun’s diameter, the union of the limbs of the two
images of the Sun cannot appear perfedt unleis the eye
be difpofed to fee objects diftindtly which are placed at
point of interfedtion. But if the eye be difpofed to fee
objects diftindtly, which are placed nearer the object -
glafs than the interfedtion is, the two limbs will appear
feparated by the interval of the axes of the pencils in
that place; anti if the eye be difpofed to fee objects dif-
tindtly, which are placed farther from the object-glafs
than the interfedtion is, the two limbs will appear to en-
croach upon each other by the diftance of the axes of the
pencils, after their croffing, taken at that place.

To explain this, let ov (plate XIX. fig. i.) reprefent
the centres of the two femi-circular glafles of the objedt-
glafs micrometer, feparated to the diftance ov from each
other, fubtending the angle oav, equal to the Sun’s dia-
meter, at the point a, which is the common focus of the
two pencils of rays having o a and v a for their axes,
namely, thofe proceeding from contrary fides of the Sun,
and paffing through the contrary femi-circles ; and let d
be the eye-glafs. It is evident, that if d be properly
placed to give diftindt vifion of objedts placed at the point
a, the rays oa,va, as well as all the other rays belonging

.

1

* j

, . 1

, - ri

!i « ^

■

■

a new prifmatic Micrometer. 801

to tliofe pencils, will be collected into one point upon the
retina of the eye; and confequently, the two oppolite
limbs of the two images of the Sun will feem to coin-
cide, and the two images of the Sun to touch one ano-
ther externally. But if the hate of the eye fhould alter,
the place of the eye-glafs remaining the fame, the eye
will be no longer difpofed to fee the image formed at the
point a diftindtly, but to fee an object placed at ef,
nearer to or farther from the objedt-glafs diftindtly ; and
therefore an image will be formed on the retina exactly
limilar to the fomewhat confufed image formed by the

rays on a plane perpendicular to their courfe at ef. Con-

/

fequently, as the two cones of folar rays, boa, cva,
formed by the two femi-circles, are feparated or en-
croach upon one another at this point of the axis by the
diftance ef, the two images of the Sun will not feem to
touch one another externally, but to feparate or to encroach
upon one another by the interval ef. The error hereby
introduced into the meafure of the Sun’s diameter will
be the angle erf, fubtended by ef at r the middle point
between o and v, which is to eaf or o av, the Sun’s ap-
parent diameter, as ae to er, or even to ar, on account
of the fmallnefs of ae with refpedt to ar.

Thefe conliderations concerning the caufe of a prin-
cipal error that has been found in the objedl-glafs micro-

Vo l. LXVII. 5 H meter,

So 2 Dr. maskelyne’s Account of

meter led me to inquire, whether feme method might
not he found of producing two diftinCt reprefentations of
the Sun, or any other objeCt, which fhould have the axes
of the pencils of rays, by which they are formed, diverg-
ing from one and the fame point, or nearly fo : and it
occurred to me, that this might be done by the refraction
of a prifm placed to receive part of the rays proceeding
from the objeCt, either before or after their refraction
through the objeCt-glafs of a telefcope. If the prifm be
placed without the objeCt-glafs, the rays that are re-
fracted through it will make an angle with the rays
that pafs belide it equal to the refraction of the prifm ;
and this angle will not be altered by the refraction of the
objeCt-glafs afterwards. Confequently, two images of an
objeCt will be reprefented, and the prifm fo applied will
enable us to meafure the apparent diameter of any ob-
ject, or any other angular diltance which is equal to the
refraCtion of the prifm. But if the prifm be placed
within the objeCt-glafs, that is to fay, between the objeCt-
glafs and eye-glafs, the angle meafured by the inftrument
will vary according to the diltance of the prifm from the
focus of the objeCt-glafs, bearing the fame ratio to the
refraCtion of the prifm, as the diltance of the prifm from
the focus bears to the focal length of the objeCt-glafs.

Let

a new prifmatlc Micrometer. 803

Let acb (fig. 2.) reprefent the objeCt-glafs, and d the
eve-glafs of a telefcope, and fr a prifm placed to in-
tercept part of the rays coming from an object, fup-
pofe the Sun, before they fall on the objeCt-glafs. The
rays ee proceeding from the Eaftern limb of the Sun,
and refracted through the objeCt-glafs acb without paf-
fing through the prifm, will form the correfponding
point of the Sun’s image at e; and the rays ww proceed-
ing in like manner from the Wellern limb of the Sun
will be refracted to form the correfpondent point of the
Sun’s image at w. But the rays 2E, 2e, aw, zw, pro-
ceeding in like manner from the Eaftern and Welfern
limbs of the Sun, and falling on the prifm pr, and
thence refracted to the objeCt-glafs acb, will, after re-
fraction through it, form the correfpondent points of the
Sun’s image at ze, zw. Let the refraction of the prifm
be equal to the Sun’s apparent diameter : in this cafe, at
whatever diftance the prifm be placed beyond the objeCt-
glafs, the two images of the Sun we, zwze, will touch
one another externally at the point ezw; for the rays
2W, 2W, proceeding from the Weftern limb of the Sun
being inclined to the rays ee proceeding from the
Eaftern limb in the angle of the Sun’s apparent diame-
ter, will, after fuffering a refraction in palling through
the prifm equal to the Sun’s apparent diameter, emerge

5 H 2 . from

804 Dr. maskelyne’s Account of

from the prifm and fall upon the objedt-glafs parallel to
the rays ee, and confequently will have their focus zw
coincident with the focus e of the rays ee, and therefore
the two images of the Sun we, zzvze, will touch one
another externally at the point ez w, and the inftrument
will meafure the angle EC2W, and that only.

But if the prifm be placed within the telefcope, the
angle meafured by the inftrument will be to the refrac-
tion of the prifm as the diftance of the prifm from the
focus of the objedt-glafs is to the focal diftance of the
objedt-glafs : or if two prifms be ul'ed to form the two
images, with their refradting angles placed contrary
ways, as reprefented in fig. 3. and 4. the angle meafured
will be to the fum of the refractions of the prifms as the
diftance of the prifms from the focus of the objedt-glafs
is to the focal diftance of the objedt-glafs. For let acb
(fig. 3.) reprefent the objedt-glafs, and d the eye-glafs of
a telefcope, and pr, rs, two prifms interpofed between
them, with their refradting angles turned contrary ways,
and the common fedtions of their refradting planes
touching one another at r. The rays proceeding from
an objedt, fuppofe the Sun, will be difpofed, by the re-
fradtion of the objedt-glafs, to form an image of the Sun
at the focus; but part of them falling on one prifm, and
part on the other, will be thereby refradted contrary
ways, fo as to form two equal images we, zwze, which,

if

a new prifmatic Micrometer. 805

if the refractions of the prifms be of proper quantities,
will touch one another externally at the point eiw. Let
ecn be the axis of the pencil of rays ee proceeding from
the Sun’s Eaftern limb; and wco the axis of the pencil
of rays ww proceeding from the Sun’s Weftern limb ;
and the point n the place where the image of the
Sun’s Eaftern limb would be formed, and the point o
where that of the Weftern limb would be formed,
were not the rays diverted from their courfe by the
refractions of the prifms. But by this means part
of the rays ee, which were proceeding to n, falling
on the prifm PR, will be refracted to form an image of
the Sun’s Eaftern limb at e , while others of the rays ee,
which fall on the prifm rs, will be refraCted to form an
image of the Sun’s Eaftern limb at ie. In like manner,
part of the rays ww, which were proceeding to form an
image of the Sun’s Weftern limb at o, falling on the
prifm rs, will be refracted to form an image of the Sun’s
Weftern limb at iw coincident with e, the point of the
image correfpondent to the Sun’s Eaftern limb; while
others of the rays ww, which fall on the prifm pr, will be
refraCted to form the image of the Sun’s Weftern limb at
w. The two images we, zwxe, are fuppofed to touch one-
another externally at the point er w. The ray efr, which
belongs to the axis ecn, and is refraCted by the prifm
er to e, undergoes the refraCtion nr<?, which (be-

caufe

806 Dr. maskelyne’s Account of

caufe fmall angles are proportional to their fines, and the
fine of NR£ is equal to the fine of its fupplement nrc)
is to ncr as nc or ce is to nr or rc. In like manner, the
ray wgr, which belongs to the axis wco, and is refradted
by the prifm rs to 210 or e, undergoes the refraction or e,
which is to oce as oc or ce is to ro or rc; therefore, by
compofition, orn the fum of the reffadtions ORq nrc, is.
to ocn the fum of the angles oc e, ncc, or the Sun’s ap-
parent diameter, as ce to rc; that is, as the focal diftance
of the objedt-glafs to the diftance of the prifms from the
focus of the objedt-glafs.

Or let the prifms pr, rs, be placed with their refract-
ing angles p, s, turned from one another as in fig 4.:
the refraction of the prifm pr will transfer the image of
the Sun from on to we, and the refruCtion of the prifm
rs will transfer the image on to 2W2e, the two images
2W2e, we, touching one another externally at the point
2 £W. Let ecn, wco, be the axes of the pencils of rays
proceeding from the two extreme limbs of the Sun, and
N, o, the points where the images of the Sun’s Eaftern
and Weftern limbs would be formed by the objedt-glafs,
were it not for the refraction of the prifms ; the ray efr,
which belongs to the axis ecn, and is refraCled by the
prifm rs to 2c, undergoes the refraction nr 2c; and the
ray wgr, which belongs to the axis wco, and is refradted

bv

J

a new prifmatic Micrometer. - 807

by the prifm pr to w, undergoes the refraction oroty
Now Neat’, part of the angle meafured, is to nr2<?, the
refradtion of the prifm Rs, as R w to cot; and oc w, the
other part of the angle meafured, is to or ot, the refrac-
tion of the prifm PB,in the fame ratio of rot to cot : there-
fore ocn, the whole angle meafured, is to orn, the fum
of the refradtions of the two prifm s, as rot to cot;
that is, as the diftance of the prifm s from the focus
of the objedt-glafs to the focal diftance of the objedt-
glafs.

When the prifms are placed in the manner repre-
fented in fig. 3. the point e of the image we is illumi-
nated only by the rays which fall on the objedt-glafs be-
tween a and f, and the point zw only by the- rays which
fall on the objedt-glafs between b and g. Now the an*
gles crf, crg, equal to the refradtions of the prifms,
being conftant, the fpaces fc, cg, will increafe in propor-
tion as the diftances rf, rg, increafe, and the fpaces af,
gb, diminifh as much; and therefore, the images at the
point of mutual contadt ezw will be each illuminated by-
half the rays which fall on the objedt-glafs when the
prifms are placed clofe to the objedt-glafs; but will be
enlightened lefs and lefs the nearer the prifms are
brought to the focus of the objedt-glafs.

But.

8o8 Dr. maskelyne’s Account of

But when the prifras are placed in the manner fhewn
in fig. 4. the images at the point of contact, as the prifms
are removed from the obje<5t-glafs towards the eye-glafs,
will be enlightened with more than half the rays that
fall on the objeCt-glafs, and will be moft enlightened
when the prifms are brought to the focus itfelf ; for the
point ic of the image 2zvie will be enlightened by all
the rays ee that fall on the objeCt-glafs between b and f,
and the point w of the image we will be enlightened by
all the rays ww which fall on the objeCt-glafs between a
and g. But the difference of the illuminations is not
very confiderable in achromatic telefcopes, on account of
the great aperture of the objedl-glafs ; as the greateft
fpace fg is to the focal diftance of the objeCt-glafs, as the
fum of the fines of the refractions of the prifms is to the
radius.

There is a third way, and perhaps the beft, of placing
the prifms, fo as to touch one another along their fides
which are at right angles to the common feCtions of their
refracting planes. In this difpofition of the prifms, the
images will be equally enlightened, namely, each with
half the rays which fall on the objett-glafs, wherever
the prifms be placed between the objeCt-glafs and eye-
glafs.

From

a new prifmatic Micrometer . 809

From what has been fhewn it appears, that this in-
ftrument, which may be properly called the prifmatic
micrometer, will meafure any angle that does not exceed,
the fum of the refractions of the prifms, excepting only
very fmall angles, which cannot be taken with it on ac-
count of the vanifhing of the pencils of rays at the junc-
ture of the two prifms near the focus of the obje£t-glafs;.
that it will afford a very large fcale, namely, the whole
focal length of the object-glafs for the greateft angle
meafured by it; and that it will never be out of adjuft-
ment; as the point of the fcale where the meafurement
begins (or the point of o) anfwers to the focus of the
objedt-glafs, which is a fixed point for celeftial objects,,
and a point very eafily found for terreftrial objects. All
that will he neceffary to be done, in order to find the
value of the fcale of this micrometer, will be to meafure
accurately the diftance of the prifms from the focus
when the inftrument is fet to meafure the apparent dia-
meter of any object fubtending a known angle at the
centre of the objeft-glafs, which may be eafily found by
experiment, as by meafuring a bafe and the diameter of
the object obferved placed at the end of it, in the man-
ner pradticed with other micrometers : for the angle fub*-
tended by this object will be to the angle fubtended by a
celeftial objedt, or very remote land object, when the
Vol. LXVII. 5 I diftance

8lO Dr. MASKELYNE’s AcCOUtlt of

diftance of the prifms from the principal focus is the
fame as it was found from the actual focus in the ter-
reftrial experiment, as the principal focal diftance of the
objedt-glafs is to the actual focal diftance in the laid ex-
periment.

It will, I apprehend, he the beft way in practice, in-
ftead of one prifm to ufe two prifms, refradting contrary
ways, and fo divide the refradtion between them (as re-
prefented in fig. 3. and 4.). Achromatic prifms, each
compofed of two prifms of flint and crown-glafs, placed
with their refradting angles contrary ways, will un-
doubtedly be neceffary for meafuring angles with great
precifion by this inftrument : and I can add with plea-
fure, that I find by experiment made writh this inftru-
ment, as it was executed by Mr. dollond with achro-
matic prifms, ground with great care for this trial above
a twelve-month ago, that the images after refradtion
through the prifms appear very diftindl; and that obfer-
vations of the apparent diameters of objedts may be
taken in the manner here propofed with eafe and pre-
cifion.

Two or more fets of prifms may be adapted to the
fame telefcope, to be ufed each in their turn, for the more
commodious meafurement of different angles. Thus it
may be very convenient to ufe one fet of prifms for mea-

1 furing

a new prifmatic Micrometer. 811

faring angles not exceeding 36', and confequently fit for
meafuring the diameters of the Sun and Moon, and the
lucid parts and diftances of the cufps in their eclipfes *
and another fet of prifms to meafure angles not much
exceeding one minute, and confequently fit for meafur-
ing the diameters of all the other planets. This latter
fet of prifms will be the more convenient for meafuring
fmall angles, on account of a fmall imperfection attend-
ing the ufe of this micrometer, as before mentioned;
namely, that angles cannot be meafured with it when the
prifms approach very near the focus of the objeCt-glafs,
the pencils of rays being there loft at the point where
the prifms touch one another.

Upon the principles that have been here explained, a
prifm placed within the telefcope of an aftronomical in-
ftrument, adjufted by a plumb-line or level, to receive all
the rays that pafs through the objeCt-glafs, may conve-
niently ferve the purpofe of a micrometer, and fuperfede
the ufe both of the vernier fcale and the external micro-
meter; and the inftrument may then be always fet to
fome even divifion before the obfervation. Thus the
ufe of a telefcopic level may be extended to meafure
with great accuracy the horizontal refractions, the de-
preflion of the horizon of the fea, and fmall altitudes
and depreffions of land objects. Time and experience

5 I 2 will

8i2 Dr. maskelyne’s Account of

will doubtlefs fuggeft many other ufeful applications of

this inftrument.

A paper from the learned Abbe boscovich was read
before this Society the ninth of lad: June, defcribing a
fimilar contrivance as an invention of the Abbe rochon,
in which the Abbe boscovich himfelf alfo claims fome
fh are ; I therefore defire to acquaint this Society, that I
communicated this invention to Mr. dollond, and had
it executed by him ; and alfo fhewed the indrument itfelf,
fo executed, to my edeemed friend Alexander aubert,
efq. fellow of this Society, a gentleman very well quali-
fied to judge of things of this nature, above a twelve-
month before the communication of the Abbe bosco-
vich’s paper, as will appear from their written atteda-
tions, drawn up at my defire, defcribing the particulars
of the communication of this invention which I made to
them fo long ago. May I be permitted to remark, that
this indrument having been executed by my directions,
in feveral forms, by Mr. dollond, between the months
of March and Augud, 1776, and fet up and tried at his
houfe in the prefence of feveral of his workmen, could
not be confidered as an abfolute fecret concealed from the
public. However, I doubt not that the following atteda-
tions of Mr.- aubert and Mr. dollond will fufficiently
prove my title to this invention of the prifmatic micro-
6 meter ;

(t new prifmatic Micrometer . 813

%

meter; and I take this opportunity of exhibiting to the
Society the inftrument itlelf, mentioned in Mr. dol-
lond’s letter as executed by himfelf according to my di-
rections, and fent to the Royal Obfervatory in the month
of Auguft 1776.

Greenwich,

December 1 1, 1777.

TO THE REV. DR, MASKELYNE,

REV. SIR,

St. Paul’s Church-yard,
Nov. 22, 1777.

ACCORDING to your delire I fend the following
particulars of the experiments which were made by your
directions, for compleating a new kind of micrometer for
meafuring fmall angles. About the beginning of April
1776, 1 received your firlt directions refpeCting this mat-
ter, which were to make two prifmatic glalfes or wedges
of fuch angles that rays of light, which paifed through
them, fhould be refraCted about 1 8' of a degree : thele
were to be placed between the objeCt-glafs and eye-glafs
of an achromatic telefcope about 30 inches long. The
angular edges of the two prifmatic glalfes were to be
placed in contact with each other; they were to be
moved in a parallel pofition from the objeCt-glals to the

focus

8 14 DA maskelyne’s Account of

focus of tile eye-glafs, and to be of fuch a fize as to cover
the aperture of the objed-glafs when brought dole to it.
By the refraction of thefe wedges two images were
formed in the telefoope, which were at the greateft dif-
tance (about 36') when the wedges were dole to the ob-
jed-glafs, and approached as they were moved towards
its focus, where they united; lo that the whole focal
diftance of the object-glals was to be the length of the
fcale for meafuring the angular diftance of the two
images formed in the telefcope. When thefe wedges
were applied, as above defcribed, the two images were
found to be coloured to a great degree, occafioned by the
refradion of the wedges. This defed you di reded me
to remove by making the prifmatic glaffes or wedges
achromatic, on the fame principles as the achromatic
objed-glafles ; and, after fome difficulties, this was ef-
feded ; the two images formed in the telefcope appeared
free from colours and diftind. The above experiments
were made in a rough wooden tube, with an inconve-
nient method of moving the wedges by hand : in this
ftate it was when fliewn to Alexander aubert, efq.
F. r. s. towards the end of May, 1776 ; after which you
deftred to have it done in a more compleat manner, in a
brafs tube, with a means of turning the tube round to
take angles in different diredions, and a method of

moving

a new prifmatic Micrometer. 8

moving the wedges with a fcrew. This was compleated
about the middle of Auguft in the fame year, and then
felt to the Royal Obfervatory. I have the honour to be,

REVEREND SIR,

Your obedient humble fervant,

PETER DOLLOND.

I HEREBY certify, that in the month of May,
1776, the Rev. Mr. maskelyne, Aftronomer-royal,
produced to me, at Mr. dollond’s houfe in St. Paul’s
church-yard, and in his prefence, as a new invention of
his own, an inftrument for meafuring fmall angles, con-
lifting of two achromatic prifms or wedges applied be-
tween the objedt-glafs and eye-glafs of an achromatic
telefcope about 30 inches long, by moving of which
wedges nearer to, or farther from, the objedt-glafs, the
two images of. an object produced by them appeared to
approach to, or recede from, each other, fo that the focal
length of the obje<St-glafs became a fcale. for meafuring
the angular diftance of the two images.

London,
Hoy. 27, 1777.

ALEX*. AU.BE RT-

[ 8i6 ]

XXXVII. T’he Repopt of the Committee appointed by the
Royal Society to confider of the be/l Method of adjujling
the fixed Points of Thermometers ; and of the precau-
tions neceffary to be ufed in making Experiments with
thofe Injlruments.

Read June 19, and Dec. 28, 1777.

tT is univerfally agreed by all thofe who make and life
A Fahrenheit's thermometers, that the freezing point,
or that point which the thermometer Hands at when fur-
rounded by ice or fnow beginning to melt, is to be called
3 20 ; and that the heat of boiling water is to be called
2120: but for want of further regulations concerning
the manner in which this laft point is to be adjufted, it is
placed not lefs than two or three degrees higher on fome
thermometers, even of thofe made by our beft artifts,
than on others. The two principal caufes of this dif-
ference are, firlt, that It has never been fettled at what
height of the barometer this point is to be adjufted^;

and

XA) Fahrenheit found that the heat of boiling water differed according
to the height of the barometer; but fuppofed the difference to be much greater

than

Report of the Committee , 8c c. 817

and fecondly, that fo much of the quickfilver in the
thermometer as is contained in the tube, is more heated
in the method ufed by fome perfons, than in that ufed by
others. To fhew that this laft circumftance ought by no
means to be difregarded, fuppofe that the ball of a ther-
mometer be dipped into boiling water as far as to the
freezing point, and confequently that the length of the
column of quickfilver in that part of the tube which is
not immerfed in the water be 180°; and fuppofe that
the heat of that part of the column of quickfilver be no
more than 1 1 20. If the thermometer be now intirel y
immerfed in the water, the heat of this column will be
increafed ioo°; and confequently its length will be in-
creafed by ^ parts of the whole, as quickfilver ex-
pands -rfzz Part °f its bulk by each degree of heat; and

confequently the thermometer will Hand or ra-

ther more than i°~ higher than it did before.

Another thing to be confidered in adjufting the boil-
ing point is, that if the ball be immerfed deep in the
water, it will be furrounded by water which will be com-

than it really is, Mr. de lug lias fince, by a great number of experiments
made at very different heights above the level of the Tea, found a rule by which
the difference in the boiling point, anfwering to different heights of the baro-
meter, is determined with great exa&nefs. According to this rule the altera-
tion of the boiling point by the variation of the barometer from 29! to 30^
inches is i°.59 of Fahrenheit,

Vo l. LXVIL 5 K

preffed

8 1 8 Report of the Committee

preffed by more than the weight of the atmofphere, and
on that account will be rather hotter than it ought to be.

We are of opinion, that the quickfilver in the tube
ought, if poffible, to be kept of the fame heat as that in
the ball, and that the ball ought not to be immerfed deep
in the water. Thefe two requilites may be obtained by
ufing a veffel covered fo as to allow no more paffage than
what is fuflicient for carrying off the fleam; for then, if
the thermometer be inclofed in this veffel in fuch man-
ner that the boiling point ill all rife but a little way above
the cover, almoft all the quickfilver in the tube will be
furrounded by the fleam of the boiling water, and con-
fequently will be nearly of the fame heat as the water
itfelf: we therefore made fome experiments to deter-
mine how regular the boiling point would be when tried
•in fuch veffels, both when the ball was immerfed in the
water, and when it was expofed only to the fleam as re-
commended by Mr. cavendish ft)

The veffel ufed in thefe experiments is reprefented in
fig. i. KB&a is the pot containing the boiling water;
d d is the cover; e is a chimney for carrying off the
fleam ; m m is the thermometer fattened to a brafs frame ;
this thermometer is paffed through a hole f/ in the co-
ver, and refts thereon by a circular brafs plate G£ fattened.

(b) Phil, Trank vol. LXVI. p. 380.

to

for adjuftlng Thermometers. 819

to its frame, a piece of woollen cloth being placed be-
tween Gg and the cover, the better to prevent the efcape
of the vapours.

There were two pots of this kind ufed by us; one five
inches in diameter and nine deep; the other, 4- in dia-
meter and 23 deep. Two of the thermometers princi-
pally ufed were the fhort ones, the brafs plate (ay) being
placed only 3| inches above the top of the ball, and the
boiling point riling not much above that plate : the third
thermometer was much longer, the plate (g g) being 1 7
inches above the ball. They were all three quick; the
firft containing only i\ degrees to an inch ; the fecond
50; and the third io°. The firft had a cylinder inftead
of a ball i~ inch long and in diameter^; the two
others had fpherical balls, about | of an inch in dia-
meter.

On trying thefe thermometers in the above mentioned
veffels, with the water riling two or three inches above
the top of the ball, we found fome variations in the
height according to the different manner of making the
experiment, but not very confiderable ; for the moll part
there was very little difference whether the water boiled

(c) Ifi the two fhort thermometers the quickfilver would have defcended into
the ball when cold, had not the tube been fwelled a little, elofe to the ball, in
-order to prevent it.

5 K 2

fait

8 ao Report of the Committee

faft or very gently ; and what difference there was, was
not always the fame way, as the thermometer fometimes
flood higher when the water boiled faft, and fometimes
lower. The difference, however, feldom amounted to
more than -^th of a degree, unlefs a confiderable part
of the fides of the pot were expofed to the fire ; but in
fome trials which we made with the fhort thermometers
in the fhort pot, with near four inches of the fide of the
veffel expofed to the fire^, they conftantly flood lower
when the water boiled faft than when flow, and the
height was in general greater than when only the bot-
tom of the pot was expofed to the fire. This difference
however was not perceived in the trials of the long
thermometer in the deep pot, as there feemed very little
difference in the height whether the water boiled faft or
flow, or whether more or lefs of the fide of the pot was
expofed to the fire. The greateft difference obferved in
the fame thermometer, on the fame day and in the fame,
water, according to the different manner of trying the
experiment, was half a degree.

(d) In all our experiments, the water was boiled over a portable black-lead
fftrnace, covered with an iron plate, which had a hole cut in it juft big enough:
to receive the bottom of the pot; fo that, by palling the bottom through this
hole to a greater or lefs depth, we could expofe more or lels of the fides to the
fire. In the other experiments, not more than one inch of the fides was ever:
expofed to the fire.

We

for adjujling Thermometers-. 821

We made fome trials with the long thermometer in
the deep pot, to determine how much the height of the
boiling point was affected by a greater or lefs depth of
water above the ball. By a mean of the experiments it
flood ,66 of a degree higher when the water role 15
inches above the ball, than when it was only three inches
above the ball; fo that increafing the depth of water
above the ball by 1 1 inches, raifed the thermometer ,66
of a degree, that is ,06 for each inch.

We would by no means infer however from hence,
that it is a conftant rule, that the height of the boiling
point is increafed ,06 of a degree by the addition of each
inch in the depth of the water above the ball ; as per-
haps the proportion would be found very different in
greater depths of water or in wider veflels.

If this rule is conftant, it would lhew that, when the
preflure on that part of the water which furrounds the
ball is increafed by increafing the depth of water above,
the ball, the height of the boiling point is not altered
thereby more than half as much as by an equal increafe
of preflure produced by an alteration in the weight of
the atmofphere : for the preflure on that part of the wa-
ter which furrounds the ball is as much increafed by an.
alteration of 1 1 inches in the depth of the water above
the ball, as by an increafe of of an inch in the height

, 822 Report of the Committee

of the barometer; and fuch an alteration in the height

of the bai'ometer is fufheient to raife the boiling point

1 °»3*

It feems as if the height of the boiling point was in
•fome meafure increafed by having a great depth of wa-
ter below the ball, as in general the fhort thermometers
flood higher when tried in the deep pot than in the fhort
one; this effeft, however, did not always take place. In
the former of thefe cafes, the depth of water below the
ball was about 18 inches, in the other only 4; but the
depth of water above the ball was the fame in both
cafes.

It muft be obferved, that when there was a great
depth of water in the veffel, either above or below the
ball, the experiments were much more irregular, and the
quickfilver in the tube remained much lefs heady than
when it was fmall. When the depth of water in the
veffel is great, it is apt to boil in gufts, which feems to
be the caufe of this irregularity; though we could not
perceive any regular connexion between thefe gufts and
the riling of the thermometer.

In the experiments made with the water not riling fo
high as the ball, fo that the thermometer was expofed
only to the fleam, we very feldom found any fenlible
difference whether the water boiled fall or flow: but

whenever

' for adjujiing Thermometers . 823

whenever there was any, the greater height was when
the water boiled fait; the difference, however, never
amounted to more than ^th of a degree.

There was fcarce ever any fenfible difference whether
the fliort thermometers were tried in the fliort pot or the
deep one, though in the former cafe the ball was raifed
very little above the furface of the water, and in the lat-
ter not lefs than 14 inches : neither did we find any fen-
fible difference in trying them in the tall pot, whether
there was a greater or lefs depth of water in the veffel.

As it was neverthelefs fufpe£ted, that the heat of the
fleam might poffibly be lefs near the top of the pot than
lower down (for in thefe experiments the ball of the
thermometer was always at the fame depth below the
cover, though its height above the furface of the water
was very different) we made two holes in the fide of a
pot four inches deeper than the deepeft of the foregoing,
one near the top of the pot, and the other not far from
the bottom, and paired the ball of the thermometer
through one or the other of thefe holes, taking care to
flop up both holes very carefully, fo that no air could
enter into the pot by them : no fenfible difference could
be perceived in the height, whether the thermometer
was placed in the upper or lower hole, though in one
3.. cafe

g 24 Report of the Committee

cafe the ball was only three inches, and in the other 2 1

inches, below the cover.

The heat of the fleam therefore appears to be not
fenfibly different in different parts of the fame pot ; nei-
ther does there appear to be any fenllble difference in its
heat, whether the water boil fall or flow ; whether there
be a greater or lefs depth of water in the pot ; or whe- .
ther there be a greater or lefs diftance between the fur-
face of the water and the top of the pot; fo that the
height of a thermometer tried in fleam, in veflels pro-
perly clofed, feems to be fcarce fenfibly affected by the
different manner of trying the experiment.

Though, as was before faid, there was fcarce any dif-
ference in the height of the quickfilver, whether the
water boiled fafl or flow, yet, when the water boiled
flow, the thermometer was a great while before it rofe to
its proper height; and when it boiled very flow, it
feemed doubtful whether it would have ever rifen to it,
efpecially if the ball was raifed a great way above the
furface of the water: but when, by making the water
boil brifkly, the thermometer had once rifen to its proper
height, the water might then be fuflfered to boil very
gently, even for a great length of time, without the ther-
mometer finking fenfibly lower ^

All

(e) The reafon of this feems to be that, while any air is left in the pot, the

fteam

for adjufting ‘Thermometers . 825

All three thermometers were found to hand, in gene-
ral, from 30 to 65 hundredths of a degree higher when
the ball was immerfed a little way in the water (neglect-
ing thofe obfervations in which much of the Tides of the
pot were expofed to the fire) than when it was tried in
fleam : at a medium they flood higher, which is equal
to the difference produced by a variation of -—ths of an
inch in the barometer; fo that the boiling point, adjufted
at a given height of the barometer, with the ball im-
merfed a little way in the water, will in general agree
with that adjufted in fleam, when the barometer is TUhs
of an inch higher.

It muft be obferved, that in all thefe experiments a
piece of fiat tin plate was laid loofely on the mouth of
the chimney e, fb as to leave no more paffage for the
fleam than what was fufficient to prevent the tin plate
from being lifted up. In trying the thermometers in
fleam, this is by no means unneceftary; for, if the cover
of the pot does not fit pretty clofe, the thermometers will
immediately fink feveral degrees on removing the tin
plate; but, when their balls are immerfed in the water,
the removal of the tin plate has no fenfible effebt.

fleam cannot acquire its full degree of heat; and that when the water boils very
gently, the air is not eafily intirely expelled from the pot. That the fleam will
nqt acquire its full degree of heat while any air is left in the pot will appear
from the next paragraph but one.

Vol. LXVII. 5 L If

826 Report of the Committee

If this cover to the chimney had been heavy, the in-
cluded fleam might have been fo much compreffed
thereby, that the water and ftearn might have acquired a
coniiderably greater heat than they ought to have done;
but as this plate lay loofe on the chimney, and as its
weight was not greater than that of a column of quick -
fdver, whofe bafe is equal to that of the mouth of the
chimney, and whofe altitude is ^-th of an inch, the excefs
of thecompreffionof the included ftearn above that which
it would fuffer in an open veffel, could not be greater
than that which would be caufed by an increafe of ~th
of an inch in the height of the barometer, which is too
fmall to be worth taking notice of; for, if the excefs of
compreffion was greater than that, the tin plate mult
necefTarily be lifted up fo much as to afford a fufficient
paffage for the fleam to efcape faft enough, though
urged by no greater force than that.

Though in the different trials of the fame thermo-
meter in fleam, on the fame day, and with the fame
water, fo little difference was obferved, according to the
different manner of trying the experiment; yet there
was a very fenfible difference between the trials made on
different days, even when reduced to the fame height of
the barometer, though the obfervations were always
made either with rain or diftilled water. The difference,
4. however.

for adjuflirig ’Thermometers . 827

however, never amounted to more than a quarter of a
degree, except in one thermometer, in which there were
three obfervations out of eighteen which differed more
than that; one of them differed fo much as 0.65° from
fome of the reft. In the obfervations made with the ball
immerfed a little way in the water, there was a greater dif-
ference between the obfervations of different days, even
negledfing thofe in which much of the fides of the pot
were expofed to the fire. In two of the thermometers
the different obfervations differed about -ff of a degree
from each other; but in the other thermometer they
varied Jbths.

We do not at all know what this difference could be
owing to, efpecially in the obfervations in fteam. It
could not proceed intirely from fome unknown dif-
ference in the water; for, if it did, the difference between
the different thermometers fhould have been always the
fame, which was not the cafe, though in general, on
thofe days in which one thermometer flood high, the
others did alfo, efpecially in the trials in fteam. More-
over, as far as can be perceived from our experiments,
there feems to be very little difference between different
waters with refpecft to the heat which they acquire in boil-
ing. We could not be fure that there was any difference be-
tween rain or diftilled water and pump water, provided

5 L 2 the

828 Report of the Committee

the latter had boiled long: neither did any difference feerct
to arife from the water containing fuch fubflances as are,
difpofed to part readily with their phlogifton; for, on
trying the thermometers in the fleam of diflilled water,
their height was not fenfibly altered by pouring in a
fm'all quantity of a folution of liver of fulphur, or of
iron filings imperfedtly rafted. The thermometer, how-
ever, feemed to Hand fenfibly lower in pump water be-
ginning to boil, than in the fame water long boiled, but
the difference fcarcely exceeded -^th or jth of a degree.

We made fome experiments to determine the heat of
water boiling in open veflels. In general, when the
veffel was almoft full, and the water boiled fail, and the
ball of the thermometer was held from three-quarters to
two or three inches, under water, and alfo in that part
of the veffel where the current of water afeended up-
wards, that is, in the hottefl part of the water, its heat
was not much different from that of the fleam of water
boiling in clofed veffels, varying only from a quarter of a
degree more than that, to as much lefs ; but if the water
boiled gently, its heat would frequently be half or three-
quarters of a degree cooler than the fleam. If the ex-
periment was tried in the deep pot with fuch a quantity
of water in it that the furface was at leafl 14 or 1 5 inches
below the top, of the pot, fo that though the veffel was

open*

for adjujlhig thermometers. 829

open, yet the water was not much expofed to the air, its
heat then feemed fcarcely lefs than when boiled in clofed
vefTels.

In making thefe experiments we chiefly made ufe of
the two fhort thermometers, in which, as the quantity of
quickfilver contained in the tube was fmall, the error
arifing from that part of the quickfilver being not heated
equally with that in the ball, could be but fmall: for
example, in the fecontl of the fhort thermometers, the,
number of degrees contained in that part of the tube,
between the circular plate Gg and the ball was_i8°. In,
the experiments in fleam this part of the tube was heated
to the fame degree as the ball. Suppofe now, that in
open vefTels it was heated only to 1220, or was go°
cooler than the ball, it is plain, that the thermometer

would hand only or yth of a degree lower than i£-

did in fleam, provided the heat of the quickfilver in the
ball was the fame in both cafes. In the ether fhort ther-
mometer, as there were only half as many degrees to an
inch, the error was only half as great.

In feveral of the experiments, however, we made ufe
of the long thermometer; but then it was neceffary ta
make an allowance on account of the quickfilver imtha
tube being not heated equally with that in the ball. The

better

830 Report ' of the Committee

better to enable us to do this, we made ufe of a thermo-
meter tube, filled with quickfilver in the fame manner
as a thermometer, only without any ball to it, or a ther-
mometer without a ball, as we may call it. A fmall brafs
plate was fixed to the tube near the top of the column
of quickfilver, to fliew the heat as in a common ther-
mometer. In all our experiments with the long ther-
mometer in open veflels, this tube without a ball, was
placed by its fide ; whence, as the quickfilver in the tube
of the long thermometer could hardly fail of being
nearly of the fame heat as that in the tube without a
ball, we knew pretty nearly the heat of the quickfilver
in the tube of the former, and confequently how much
higher it would have flood if the quickfilver in its tube
had been of the fame heat as that in the ball. F or exam-
ple, on October 19, the long thermometer tried in an
. open veffel, the water boiling faft, flood x°.65 lower than
it did when tried in fleam the fame day, the quickfilver
in the tube without a ball Handing at the fame timfc at
to 90: we xnay therefore conclude, that the heat of the
quickfilver, in that part of the tube of the long thermo-
meter which was not immerfed in the water, was alfo
10 90; and confequently, as that part of the tube con-

;tained about 170°, the thermometer flood , or

i°52'

for adjujling 'Thermometers* 831

1 '.5 2 lower than it would have done if the quickfilver
in the tube had been of the fame heat as that in the ball ;
and, confequently, the quickfilver in the ball of the ther-
mometer was in reality .07 cooler than when tried in
fleam.

We examined the boiling points of feveral thermo-
meters, made by different artifts, by trying them in fleam
when the barometer was at 30.1, and finding what di-
vifion on the fcale the quickfilver flood at. The differ-
ence of the extremes was 3°^ ; but, by a mean of all, it
was found to Hand at e x 30. 1, and confequently wmuld
have flood at 2120, if the barometer had been at 29.4;
fo that if the boiling point was to be adjufted, either in
fleam, when the barometer is at 29.4, or with the ball
immerfed two or three inches in water, when the baro-
meter is at 29.1, it would agree belt with the mean of
the abovementioned thermometers. But as it feems to be
of no great fignification to make the boiling point agree
very nearly with the mean of the thermometers made at
prefent, when the extremes differ fo widely ; and as we
apprehend that it will be more convenient to the makers
that fome height fhould be chofen which differs lefs
from the mean, as thereby they will more frequently^
have an opportunity of adj tilling the boiling point with-
out the trouble and danger of millakes which attend the

making

‘83 a Report of the Committee

making a correction, we recommend, that the boiling
point fhould be adjufted when the barometer is at 29.8,
if the perfon clinics to do it in fleam; or when the baro-
meter is at 29Y, if he choofes to do it in clofe vcffels,
with the ball immerfed to a fmall depth under the water.
Our reafon for pitching upon this precife height is, that
thereby the boiling point will differ from Mr. de luc’s
boiling point, by a Ample fraction of the degrees of his
common fcale, namely three-quarters of a degree higher.

We are informed by Mr. de luc, that the method he
ufed in adj ufting the boiling point, though he forgot to
mention it in the Recherches fur les Modifications de V At ~
mofphere , was to wrap rags round the tube of the ther-
mometer, and to try it with the ball immerfed in water
in an open veffel, of the form deferibed in the above-
mentioned book, while boiling water was poured at dif-
ferent times on the rags, in order that the quickfilver in
the tube might be heated, if poflible, to the fame degree
as that in the ball. As well as we can judge from the
abovementioned experiments in open veflels, and from
the few trials we have made of this method, we are in-
clined to think, that the boiling point adj ufted this way
Will in general differ but little from that adj ufted in fleam
at the fame height of the barometer, efpecially if the
frrermometer be not very long, and do not extend a great

way

for adjufling 'thermometer's. 833

way below the freezing point (f>\ confequently, as Mr.
de luc’s boiling point was adjufted when the barometer
was at 27 Paris or 28.75 Englifh inches, it will hand
lower than that adjufted in the manner recommended by
us, by three-quarters of a degree of his fcale; or 8o°|
on de luc’s thermometer, will anfwer to 2120 on Fah-
renheit’s adjufted in the manner propofed.

Though the boiling point be placed fo much higher
on fome of the thermometers now made than on others,
yet we would not have the reader think that this can
make any confiderable error in the obfervations of the
weather, at leaft in this climate; for an error of i°r in
the pofition of the boiling point will make an error of
only half a degree in the pofition of 920, and of not
more than a quarter of a degree in the point of 62°. It
is only in nice experiments, or in trying the heat of hot
liquors, that this error in the boiling point can be of
much fignification.

(f) In order to fee how much the quickiilver in the tube of the thermometer
would be heated in this method of adjufting the boiling point, we took the
abovementioned tube without a ball, wrapped it round with rags, and poured
boiling water on it as above defcribed: the heat of the quickiilver therein was
found to be about 210 lefs than that of boiling water; and, therefore, the boiling
point of a thermometer, adjufted in this manner, fuppoling the thermometer to
be dipped into the water as far as to the point of 320, fhould Hand about one-
third of a degree lower than it would do if the quickiilver in the tube was heated
equally with that in the ball.

5 M

Vol. LXVII.

There

834 Report of the Committee

There is another circumftance that we have not yet
taken notice of, which, in ftridtnefs, caufes fome error
in thermometers, namely, the difference of expan lion of
the glafs tube and the fcale. But this error is in almoft
all cafes fo fmall as to be not worth regarding ; we have,
however, in the note below given a rule for computing
the value of it lsK

(g) The ufual way of adjutting thermometers is, to mark the boiling and
freezing points on the glafs tube, and not to fet off thofe points on the fcale till
fome time after, when the tube and fcale may both be fuppofed to be nearly of
the temper of the air in the room; confequently, when the thermometer is
' expofed to a greater heat than that, the fcale, if of brafs, will expand more
than the glafs tube, and the divifionson it will be longer than they ought to be;
but, if the fcale be of wood, it will expand lefs than the glafs tube, and the
divifions will be too fhort. Let now the heat of the air, when the divifions
were fet off on the fcale, be called a; let the degree of heat which the ther-
mometer ttands at in the experiment be called d; and let the degree anfwering
to that point of the fcale in which the thermometer is fattened to the fcale be
called F. Then, if all parts of the thermometer and fcale are heated equally,
and the fcale is of brafs, the thermometer will appear to ttand lower than it

ought to do by the part of a degree, obferving, that if d —f x d — a

is negative, it will ttand higher than it ought to do; but if the fcale is of wood,

it will ttand higher than it ought to do by the part of a degree.

If the thermometer be fattened to the fcale by the ball, or any part of the tube
lower than the obferved heat, the error will be the fame, whether that part of
the tube and fcale, which is above the obferved degree, be of the lame heat as
the ball or not : but if the thermometer is fattened to the fcale by the top of the
tube, as is frequently done, then the error will vanilh whenever that part of
the tube and fcale, which is above the obferved degree, is not much heated.
This rule is founded on Mr. smeaton’s experiments, who found, that wdiite
glafs expands x^oth of an inch in a foot by 180° of heat; that brafs wire
expands xlMoj and that wood expands fcarce fenlibly.

la

for adjufting thermometers. 835

In making experiments with thermometers, it evi-
dently is equally neceffary that the quickfilver in the
tube fliould be of the fame heat as that in the ball, as it
is in adjufting the boiling point: for this reafon, in trying
the heat of liquors much hotter or colder than the air,
the thermometer ought, if poffible, to be immerfed as
far as to the top of the column of quickfilver in the tube.
As this, however, would often be very difficult to exe-
cute, the obferver will frequently be obliged to content
himfelf with immerfing it to a much lefs depth. But
then as the quickfilver, in a great part of the tube, will
be of a different heat from that in the ball, it will be ne-
ceffary, where any degree of accuracy is required, to
make a correction, on that account, to the heat fliewn by
the thermometer. If the heat of the quickfilver in the
tube be known, the correction may readily be made by
help of the annexed table ; the only difficulty lies in efti-
mating what that heat may be. In all probability the
heat of the quickfilver in the tube will not be very dif-
ferent from that of the air which furrounds but as

that

(h) This mull evidently be the cafe, unlefs the quickfilver in the tube is
confiderably heated by its conta£l with that in the ball. To fee whether this
was the cafe, fome fand was heated in a fmall copper difh over a lamp to the
heat of about 2120, and the abovementioned tube, without a. ball, laid hori-
zontal with the end extending about half an inch over the fand; but, to prevent
its being heated thereby, a piece of wood, about a quarter of an inch thick,

5 M 2 was

836 Report of the Committee

that air will be affedted by the fleam of the liquor, and
the fire by which it is heated, it will commonly be of a
very different heat from the reft of the air of the room
in which the experiment is made ; but as no great nicety
is required in eftimating the heat of the quickfilver in
the tube, infomuch that a miftake of 250 therein will
caufe an error of only half a degree in the correction,
when the number of degrees in that part of the tube
which is not immerfed in the liquor is not more than
220°, it will commonly be not difficult to guefs at
the heat of the quickfilver in the tube as near as is re-
quired'"'7. But if the obferver is defirous of more accu-
racy^.

was laid between the fand and it. After it had remained a fufficient time in
this fituation, the divifion which the quicksilver flood at was obferved. The
piece of wood was then, removed, and the end of the tube laid in the fane!,
which was heaped over it fo that about half an inch of the column of quick-
filver was intirely furrounded by the hot fand, and muff therefore be heated to
nearly the fame degree as it. The quickfilver in the tube rofe very little higher,
than before, and feemingly not more than might be owing to the expanfion of
the half inch of quickfilver which was furrounded by the fand; fo that itfhould
feem, that heating one end of the. column of quickfilver does not communicate
much heat to the reft of the column; and confequently, that, when the ball of
a thermometer is immerfed in hot liquor, the quickfilver in the tube will not be.
much hotter than the furrounding. air.

(i) The better to enable the reader to guefs at the heat of the quickfilver in
the tube, in cafes of this kind, we. tried how much the quickfilver in the above-
mentioned tube, without a ball, would be heated when held over a vefiel of
boiling water. It is true, that thefe experiments cannot be of any great fervice
towards this purpofe, as the tubes will be very differently heated, according to

the

for adjujling thermometers. 837

racy, he may find the heat of the furrounding air by
holding the ball of a fmall thermometer near the tube

of

the degree of heat of the fluid, and’ the quantity of fleam which it furnifhes*
and according to the nature of the fire by which it is heated; yet as the
experiments may perhaps ferve in fome meafure to redlify our ideas on this head*
we will give the refult. When the abovementioned tube without a ball *, the
length of the column of quickfilver in which was 15 inches, was held perpen-
dicularly over the veflel of boiling water, with its bottom even with the fur face
of the water, the heat of the quickfilver was in all the trials we made from 68'
to 28° hotter than the air of the room. If the tube was held inclined to the
horizon, in an angle of about 30°, with the bottom of the column of quick-
filver reaching not more than three quarters of an inch within the circumference
of the pot, fo that the column of quickfilver was as little heated by the fleam as-
could eafily be done, it was from 30 to 70 hotter than the air. When a fhorter.
tube of the fame kind, in which the column of quickfilver was feven inches,,,
was ufed, the quickfilver was from 62 to 440 hotter than the air, when held-,
perpendicularly, and from 49 to 36° hotter when held inclined. The water in.
thefe trials frequently boiled pretty fafi, but never very violently. It was im
general heated over a portable black lead furnace placed in the middle of the room ;
but it was once heated over an ordinary chafing- difli, when the quickfilver in-
the long tube, held perpendicularly, was found to be 64° hotter than the air*
When the experiments were tried without doors, the heat of the quickfilver in*
the tube would vary very much, according as the wind blew the fleam and hot;
air from or towards the tube, but it fometimes rofe as high as it did within,
doors.

The moft convenient method we know of making thefe tubes without a ball is,
to fill a thermometer in the ufual manner,. and heat the ball till there is a proper
quantity of quickfilver in the tube, and then. to make the column of quickfilver
feparate.at the neck of the ball,., and run to the extremity of the tube, fo as to
leave a vacuum between the ball and the column of quickfilver, as is expreffed
in fig. 2. where the (haded part ad reprefents the column of quickfilver, and
ba that part in which there is a vacuum. The tube muff then be fealed fome.-

See p. 830. h 1,

where

8 o 3 Report of the Committee

of the thermometer with which he tries the heat of the
liquor; or, what will be much better, he may have a
tube without a ball, fuch as is above defcribed, fattened to
the frame of the thermometer, on one ttde of the tube ;
or if he has two fuch tubes, of different lengths, it will
be ftill more accurate.

To avoid the inconvenience of this correction, per-
haps it may be thought, that both in adjufting the boiling
point and in trying the heat of liquors, it would be better
that not much more than the ball cf the thermometer
fhould be immerfed, and that the tube ftiould be held in-
clined in fuch manner as to be heated as little as poflible ;
as it may be laid, that by this means you will find the heat
of liquors pretty nearly, without the trouble of making
any correction ; and that, though in ttricttnefs a correction
would be required in obferving the heat of the air with

where between b and a as at e, and cut off there; after which it mud be held
with the end d upwards, fo as to make the column of quickfilver run to the
extremity E : by this method of filling it is plain, that no fenfible quantity of
air can be left between e and the column of quickfilver; but yet the quickfilver
will be apt not to run fufficiently clofe to the extremity E, as the weight of the
column will be fcarcely fuflicient to force it into the narrow fpace which will
commonly be left in fealing the tube, efpecially when held nearly horizontal :
for this reafon it will be proper to open the tube at d, fo as to let in the air,
and then feal it again. It muff be obferved, that the fpace left between d and
the column of quickfilver ought not to be lefs than the tenth part of the length,
of the column of quickfilver, as otherwife the included air might be too much
compreffed by the expanfion of the quickfilver when much heated.

fuch

for adjujling 'thermometers. 839

fuch thermometers, yet the heat of the atmofphere never
differs fo much from the mean heat, as to make that cor-
redtion of much confequence a> . But, on the other hand,
this method of making and ufing thermometers is much
lefs exadt than the former, and therefore is unfit for nice
experiments ; and, befides, a corredtion would be as ne-
cefiary with this kind of thermometer in trying the heat
of air, artificially heated, or in finding the heat of large
quantities of hot liquors, in which it would be difficult
to prevent the quickfilver in the tube from being heated

(k) The degrees on all thermometers are intended to anfvver to equal por-
tions of the folid contents of the tube; and, confequently, if the quickfilver in
the tube is kept conflantly of the fame heat as that in the ball, the degrees will
anfwer to equal increments of bulk of the whole quantity of quickfilver in the
thermometer, that is of a given weight of quickfilver. But if only the quick-
filver in the ball is heated, and that in the tube is kept always of the fame heat,
the degrees will anfwer to equal increments of a given bulk of quickfilver; fo
that the fcale of the thermometers will be really different in thefe two methods
of proceeding, and in high degrees the difference will be very confiderable ; for
example, let two thermometers be made, and in the firfi: of them let care be
taken, both in adjufting the fixed points and in trying the heat of liquors, that
the quickfilver in the tube fhall be of the fame heat as that in the ball; and in
adjufling the fixed points of the fecond, and in trying the heat of liquors with
it, let care be taken that the quickfilver in the tube fhall remain always of the
fame invariable heat, and let the freezing and boiling points be marked 32 and
212 on both of them : then will the degree of 620 on the firfi: anfwer to that of
600 on the fecond; that of 406 to 400; that of 302 to 300; and that of
1 19.7 to 120; that is, a liquor which appears to be of 620° of heat by the firfi
will appear to be of 600 by the fecond, &c. It appears from hence, that it would
be improper to employ the latter method of adjufling and ufing thermometers
for ordinary purpofes, and the former for nice experiments.

3 by

840 Report of the Committee

by the fleam, as it is in finding the heat of liquors with
the other thermometer, whenever the ball is not im-
merfed to a fufficient depth ; fo that, on the whole, the
former method of making and uiing thermometers
feems much the beft.

A much better way of avoiding the trouble of making
a correction would be to have two fets of divifions made
to fuch thermometers as are intended for trying the heat
of liquors; one of which fhould be ufed when the tube
is immerfed almoft to the top of the column of quick-
ill ver; and the other, when not much more than the ball
is immerfed, in which laft cafe the obferver fhould be
careful that the tube fhould be as little heated by the
fleam of the liquor as conveniently can be. It is difficult
to give rules for conftruCting this fecond fet of divifions,
as the heat of the quickfilver in the tube will be very
different according to the temper of the air in the room,
the quantity and nature of the fluid whofe heat is to be
tried, the manner in which it is heated, and the other
circumftances of the experiment ; but, on the whole, we
think that, given in the following table, would be as pro-
per as any.

1

Degree

for adj lifting thermometers*

841

S N

Vol. LXVII.

To

anfwering to that point of the tube, which is two inches above the ball.

842 Report of tbe Committee

To make ufe of this table, feek in the uppermoft ho-
rizontal line the degree of the thermometer anfwering to
that point of the tube which is two inches above the
ball; and in the left-hand column feek the degrees of
the fecond fet of divifions; the correfponding numbers
in the table are the correfponding degrees of the firft fet,
or the degrees which they muft be fet oppolite to. The
right-hand perpendicular column fhews the heat which
the quickfilver in the tube was fuppofed to be of in
forming this table.

Though this fecond fet of divifions be far from accu-
rate, yet it is at Iealt as much fo as a thermometer ad-
jufted in the latter method can be ; fo that this double fet
of divifions pofiTeffes all the advantages which can be ex-
pected from that method of adjufting thermometers,
without the inconveniences..

A table

for adjufting thermometers .

843

A table for correcting the obferved height of a thermo-
meter, whenever the quickfilver in the tube is not of
the fame heat as that in the ball.

DifF.

of

Degrees not immeried in the liquors.

Heat

5°

100

150

200

230

3°°

35°

400

45°

500

550

600

. 650

0

0

75°

50

i

•4

•7

•9

1. 1

i-3

I,5

i-7

2.

2.2

2.4

2.6

2.8

3-1

3-3

100

-4

•9

i-3

1.8

2.2

2.6

3-o

3-5

3-9

4.4

4.8

5*2

5-7

6.1

6.6

•7

lt3

! 2.0

2.6

3*3

CO

4.6

5*2

5.9

6.5

7.2

7*9

8.4

9.2

9.8

200

•9

1.8

2.6

3*5

4.4

5-1

6. 1

7.0

'-X

00

CO

9.6

10

1 1

12

i3

250

<1.1

2.2

3*3

4*4

5-5

6.4

7.6

8.7

9.8

1 1

12

*3

15

16

300

2.6

3-8

5-1

6.4

7*7

9*1

10

12

13

14

16

*7

18

20

350

*•5

3^°

4.6

6.1

7.6

9-1

1 1

12

H

1S

*7

18

20

21

23

400

J-7

3-5

5*2

7*°

8.7

10

12

H

l6

17

l9

21

23

24

26

45°

2.

3-9

5.9

00

9-8

12

H

16

l8

20

22

24

25

27

29

500

2.2

4.4

6.5

CO

1 1

*3

17

20

22

24

26

28

31

33

55c

2.4

1 4-3

7.2

9.6

12

H

17

19

22

24

26

29

31

34

36

To make ufe of this table, in the left-hand perpen-
dicular column look for the number of degrees con-
tained in that part of the tube which is not immerfed in
the fluid whofe heat is to be tried, and in the upper ho-
rizontal line feek the fuppofed difference of heat of the
quickfilver in that part of the tube from that in the ball ;
the correfponding number in the table is the correction,
which muft be added to the obferved heat when the

5 N 2 quick-

844 Report of the Committee

quickfllver in the tube is cooler than that in the ball, and
fubtraCted when it is warmer : for example, let the ob-
ferved heat of the fluid be 47 50, let the thermometer be
immerfed in the fluid as far as to the degree of 250, or
to that part of the tube which fhould be marked 250 if
the divifions were continued long enough ; then is the
number of degrees in that part of the tube which is not
immerfed in the fluid 45 o ; and let the heat of the quick-
lilver in that part of the tube be fuppofed ioo°; and
confequently, the difference of heat of the quickfilver in
that part of the tube from that in the ball 375 ; then in
the left-hand perpendicular column feek the number
450, and in the upper horizontal line the number 375;
the correfponding number in the table, or the correction,
is 1 50, and therefore the true heat of the fluid is 49 o°.

This correction may be had very eafily without the
help of the table, only by multiplying the number of
degrees not immerfed in the fluid by the fuppofed dif-
ference of heat, dividing the produCt by 10000, and
diminifhing the quotient by one-eighth part of the
whole.

In the following pages we have thrown together the
practical rules, which we would recommend to be ob-
ferved in adjufting the fixed points of thermometers.

4 Rules

for adjujiing 'thermometers .

Rules to he obferved in adjujiing the boiling point .

The moft accurate way of adj ufting the boiling point
is, not to dip the thermometer into the water, but to ex-
pofe it only to the fteam, in a veffel clofed up in the
manner reprefented in fig. 4. where K&ba is the veffel
containing the boiling water, r> d the cover, e a chimney
made in the cover intended to carry off the fteam, and
mm the thermometer pafled through a hole in the cover.
Thofe who would make ufe of this method muft take
care to attend to the following particulars.

1 ft, The holing point muft be adjufted when the ba-
rometer is at 29.8 inches unlefs the operator is willing
to corredt the obferved point in the manner directed
below.

2dly, The ball of the thermometer muft be placed at
fuch a depth within the pot, that the boiling point fhall
rife very little above the cover; for otherwife part of the
quickfilver in the tube will not be heated, and therefore
the thermometer will not rife to its proper height. The
furface of the water in the pot alfo fliould be at leaft one
or two inches below the bottom of the ball ; as otherwife
the water, when boiling faft, might be apt to touch the
ball: but it does not fignify how much lower than that
the furface of the water may be.

846 Report of the Committee

3<ily, Care muft be taken to flop up the hole in the
cover through which the tube is inferted, and to make
the cover fit pretty clofe, fo that no air fhall enter into
the pot that way, and that not much fleam may efcape.
A piece of thin flat tin plate muft alfo be laid on the
mouth of the chimney, fo as to leave no more paflage
than what is fufficient to carry off the fleam. The fize
of this plate fliould be not much more than fufficient to
cover the chimney, that its weight may not be too great ;
and the mouth of the chimney fliould be made flat, that
the plate may cover it more completely. It muft be ob-
ferved, that when the tin plate is laid on the mouth of
the chimney, it will commonly be lifted up by the force
of the fleam, and will rattle till it has flipped afide fuffi-
ciently to let the fleam efcape without lifting it up. In
this cafe it is not neceflary to put the plate back again,
unlefs by accident it has flipped afide more than ufual.
If the artift pleafes, he may tie each corner of this plate
by a firing to prongs fixed to the chimney, and Handing
on a level with the plate, as thereby it will neceflarily be
kept always in its place (I>\ but we would by no means
recommend having it made with a hinge, as that might

(l) Fig. 3. is a perfpe£live view of the chimney and tin plate; abcd is the
plate; E the chimney; f/, G£, Mm, and Kn, the prongs fattened to the chim-
ney, to which the four corners of the plate are to be tied by the firings af, bg,
cm, and dn; the ends f, g, m, and n, of the prongs muft be on a level with
-the plate, and the firings fhould not be ftretched tight.

5

be

for adjujling ’Thermometers. 847-

■fee apt to make it ftick, in which cafe the included va-
pour might be fo much compreffed as to caule an error.
We would alfo by no means advife lining the tin plate
with leather, or any other foft fubftance, for the fake of
making it fhut clofer, as that alfo might be apt to make
it ftick. The chimney alfo ought not to be made lefs
than half a fquare inch in area: for though a fmaller
chimney would be fufficient to carry off the fteam, un-
lefs the veffel is much larger than what we ufed; yet the
adhefion which is apt to take place between it and the
tin plate when wet, might perhaps bear too great a pro-
portion to the power which the included fteam has to lift
it off, if it was- made much lefs. It is convenient that
the chimney be not lefs than two or three inches
long, as thereby the obferver will be lefs incommoded
by the fteam ; but it would be improper to make it much,
longer, for the longer the chimney is, the greater difpo-
fition has the air to enter into the pot between it and the
cover..

It is moft convenient not to make the cover fit on
tight, but to take on and off eafily ; and to wrap fome
fpun cotton round that part of the cover which enters
into the pot, in order to make it fhut clofer ; or, what
feems to anfwer rather better, a ring of woollen cloth
maybe placed under the cover, fo as to lie between the top
o£

S48 Report of the Committee

of the pot and it. Thefe methods of making the cover
fiiut clofe can be ufed more conveniently when the cover
is made to enter within the pot, as in the figure, than
when it goes on on the outfide.

There are various eafy ways by which the hole in the
cover, through which the tube of the thermometer is
paired, may be flopped up, and by which the thermome-
ter may he fufpended at the proper height. The hole in
the cover may be flopped up by a cork, which muft firfl
have a hole bored through it, big enough to receive the
tube, and be then cut into two, parallel to the length of the
hole. Another method, more convenient in ufe, but not
fo eaiily made, is reprefented in fig. 6. which exhibits a
perfpe£live view of the apparatus ; a a is the cover; h the
hole through which the thermometer is paffed ; b b a fiat
piece of brafs fixed upon the cover; and D(/e« a Aiding
piece of brafs, made fo as either to cover the hole h, or
to leave it uncovered as in the figure, and to be tightened
in either pofition by the fcrew s Aiding in the Ait m m ;
a femi-circular notch being made in the edge b Z>, and alfo
in the edge d d, to inclofe the tube of the thermometer :
pieces of woollen cloth fiiould alfo be fattened to the
edges b b and d d, and alfo to the bottom of the Aiding
piece p d'E e, unlefs that piece and the cover are made fuf-
ficiently flat, to prevent the efcape of the fleam. In

order

for adjujling i thermometers . 849

order to keep the thermometer fulpended at the proper
height, a clip may be ufed like that reprefented in fig. 7 .
which by the fcrew s mull be made to embrace the tube
tightly, and may reft on the cover. That part of the
clip which is intended to bear againft the tube, had belt
be lined with woollen cloth, which will make it ftick
tighter to the tube, and with lets danger of breaking it.
Another method, which is rather more convenient, when
the top of the tube of the thermometer is bent into a
right angle, in the manner frequently pradtifed at prefent
for the fake of more conveniently fixing it to the fcale, is
reprefented in the fame figure ; Gvy f / is a plate of brafs,
Handing perpendicularly on the cover, and l/n/z a piece
of brafs, bent at bottom into the form of a loop, with a
notch in it, fo as to receive the tube of the thermometer,
and to fuffer the bent part to reft on the bottom of the
loop; this piece muft Hide in a flit k£, cut in the plate
l/nzz, and be tightened at any height by the fcrew t.

4thly, It is beft making the water boil pretty brifklv, as
otherwife the thermometer is apt to be a great while be-
fore it acquires its full heat, efpecially if the veflel is very
deep. The obferver too flrould wrait at leaft one or two
minutes after the thermometer appears to be ftationary,
before he concludes that it has acquired its full height.

Vol. LXVIL 5 O sthly,

850 Report of the Committee

5thly, Though, as was faid before, this appears to be
the moft accurate way of adjufting the boiling point ; yet,
if the operator was to fuffer the air to have any accefs to
the inlkle of the velfel, he would be liable to a very great
error: forthisreafonwe ftrongly recommend it to all thofe
who ufe this method, not to deviate at all from the rules
laid down without alluring themfelves, by repeated trials
with a pretty fenlible thermometer, that luch alteration
may be ufed with fafety. But the covering the chimney
with the tin plate ought by no means to be omitted ; for
though, if the cover of the pot fits clofe, it feldom figni-
fies whether the plate is laid on or not, yet, if by acci-
dent the cover was not to fit clofe, the omitting the tin
plate would make a very great error. Making the chim-
ney very narrow would not anfwer the end properly;
for, if it was made fo fmall as to make the veffel fuffici-
ently clofe when the water boiled gently, it would not
leave fufficient paffage for the efcape of the fleam when
the water boiled fall.

Another way of adjufting the boiling point is, to try
it in a veffel of the fame kind as the former, only with
the water riling a little way, namely from one to three
or four inches above the ball, taking care that the boil-
ing point fhall rife very little above the cover, as in the
former method. In this method there is no need to cover

the

for adjujUng Thermometers, 851

the chimney with the tin plate ; and there is lefs need to
make the cover fit clofe, only it mnft be obferved, that
the clofer the cover fits, the lefs the operator will be in-
commoded by the fleam. The height of the barometer
at which the boiling point fhould be adjufted, when this
method is ufed, is 29^- inches, or three-tenths of an inch
lefs than when the former method is nfed.

It will be convenient to have two or three pots of dif-
ferent depths; for if a fliort thermometer is to be ad-
jufted in the fame pot which is ufed for a long one, it
will require a great depth of water, which, befides taking
up more time before it boils, makes the obfervation
rather lefs accurate, as the heat feems to be lefs regular
when the depth of water in the pot is very great, than
when it is lefs.

Perhaps fome perfons, for the fake of heating the
water more expeditioufly, may be inclined to ufe-an ap-
paratus of fuch kind that the fire fhall be applied to a
confiderable part of the fides of the pot as well as to the
bottom; we would, however, caution them againft any
thing of that kind, as the obfervations are confiderably
lefs regular than when little more than the bottom of
the pot is heated. If the pot is heated over a chafing-difh
or common fire, we apprehend that there can feldom
be any danger of too much of the fides being heated;

5 O 2 ' bu

ft

852 Report of the Committee

but if the operator fhoulil be apprehenfive that there
is, it is eafily prevented by fattening an iron ring an
inch or two broad round the pot near the bottom. This
precaution is equally neceflary when the thermometer is
adjufted in fteam, efpecially when there is not much
water in the pot.

The greateft inconvenience of this method of a dj lift-
ing the boiling point is the trouble of keeping a proper
depth of water in the pot, as to do this it is neceflary firft
to find the height of the boiling point coarfely by try-
ing it in an open veflel, and then to put fuch a quantity
of water into the pot that it fhall rife from one to three
or four inches above the ball, when the thermometer is
placed at fuch a depth within the pot that the boiling-
point fhall rife very little above the cover. The operator
mutt be very careful that the quantity of water in the
pot be not fo fmall as not intirely to cover the ball.

A third way of adjufting the boiling point is, to wrap
feveral folds of linen rags or flannel round the tube of
the thermometer, and to try it in an open veflel, taking
care to pour boiling water on the rags, in order to keep
the quickfilver in the tube as nearly of the heat of boiling
water as poflible. The beft wTay is to pour boiling water
on the rags three or four times, waiting a few feconds be-
tween each time, and to wait fome feconds after the laft
>n time

for adjujling thermometers. 853

time of pouring on water before the boiling point is
marked, in order that the water may recover its full
ftrength of boiling, which is in good meafure checked
by pouring on the boiling water.

In this method the boiling point fhould be adjufted
when the barometer is at 29.8 inches, that is, the fame
as when the firft method is ufed ; the water fhould boil
faft, and the thermometer fhould be held upright, with
its ball two or three inches under water, and in that part
of the vefTel where the current of water afcends^.

Whichever of thefe methods of adjufting the boiling
point is ufed, it is not neceffary to wait till the barometer
is at the proper height, provided the operator will take
care to corredt the obferved height according to the fol-
lowing table.

(m) In a veffel of boiling water one may almoft always perceive the current
of water to afcend on one fide of the veffel5 and to defcend on the other* .

Height

354

Report of the Committee

Height of the baro-
meter when the boil-
ing point is adjufted
according to,

Correction in
ioooths of the
interval be-
tween 12 'J and
212°.

Height of the baro-
meter when the boil
ing point is adjufted
according to,

Correction in
ioooths of the
interval be-
tween 32° and
212°.

<

lit or 3d
method.

1

2d

method.

XT

lit or 3d
i method.

1

2d

method.

30.64

1 *

1 O

w

| 29.69

29*39

I'

53

9

58

28

2

30.71

41

8

47

17

n

D

59

29

7

36

06

4

48

18

6

•

U

2 5

28.95

5

•

U

37

07

5

> %
O

!4

84

6

O

bp

25

29-95

4

r-H

03

73

7

H

14

84

3

C\

00

62

8

03

73

2

81

51

9

29.91

61

1

70

—

10

80

5°

0.

39

—

11.

To make life of this table, feelc the height which the
barometer is fouiid to Hand at in the left-hand column,
if the boiling point is adj ufted either in the fir ft or third
method, and in the fecond column if it is adjufted in the
fecond method ; the correfponding number in the third
column fliews how much the point of 2 1 2°muftbe placed
above or below the obferved point, exprefled in thou-
fandth parts of the interval between the boiling and
freezing point : for example, fuppofe the boiling point

is

for adjujling t thermometers . 855

is adj ufted in fteam when the barometer is at 29 inches,
and that the interval between the boiling and freezing
points is 1 1 inches; the neareft number to 29 in the
left-hand column is 29.03, and the correfponding num-
ber in the table is 7 higher, and therefore the mark of
2120 rauft be placed higher than the obferved point by

7333 of the interval between boiling and freezing, that is,

hy S’ or *°77 of an inch.

This method of correcting the boiling point is not
ftriCtly juft, unlefs the tube is of an equal bore in all its
parts ; but the tube is very feldom fo much unequal as to
caufe any fenlible error, where the whole correction
is fo fmall. The trouble of making the correction will
be abridged by making a diagonal fcale fuch as is repre-
fented in fig. 5 .

It is not very material what kind of water is ufed for
adjufting the boiling point, fo that it is not at all fait;
only, if any kind of hard water is ufed, it is better that it
fhould be kept boiling for at leaft ten minutes before it
is ufed. But we would advife all thofe defirous of ad-
jufting thermometers in the moft accurate manner for
nice experiments, to employ rain or diftilled water, and
to perform the operation in the firft mentioned manner,,
that is, in fteam..

8§6

Report of the Committee

On the freezing point.

In adjufting the freezing as well as the boiling point,
the quickfilver in the tube ought to be kept of the fame
heat as that in the ball. In the generality of thermome-
ters, indeed, the diftance of the freezing point from the
ball is fo fmall, that the greateft error which can arife
from neglecting this precaution is not very confiderable,
unlefs the weather is warmer than ufual; but as the
freezing point is frequently placed at a confiderable dif-
tance from the ball, the operator fhould always be care-
ful either to pile the pounded ice to fuch a height above
the ball, that the error, which can arife from the quick-
filver in the remaining part of the tube not being heated
equally with that in the ball, fhall be very fmall; or he
muft correft the obferved point, upon that account, ac-
cording to the following table :

Heat of the air.

Correction.

42°

.00087

52

.00174

62

.00261

72

.00348

82

•0043s

The

P/iihj.Tratuf;_LXnj: Tafi JCX. p.SsG.

for adjujling thermometers. 857

The firft column of this table is the heat of the air,
and the fecond is the correction expreffed in 1 oooth
parts of the diftance between the freezing point and the
furface of the ice: for example, if the freezing point
ftands feven inches above the furface of the ice, and the
heat of the room is 6 2, the point of 3 20 fhould be placed
7 x .00261, or .018 of an inch lower than the obferved
point. This correction alfo would be made more eafy by
the help of a diagonal fcale, iimilar to that propofed for
the boiling point.

On the precautions necejfary to be obferved in making ob~
fervations with thermometers.

In trying the heat of liquors care fhould be taken
that the quickfilver in the tube of the thermometer
be heated to the fame degree as that in the ball; or, if
this cannot be done conveniently, the obferved heat
fhould be corrected on that account: but for this we
refer to the former part, p. 835.

H. CAVENDISH.

W. HEBERDEN.
ALEXr. AUBERT.

J. A. DE LUC.

N. MASKELYNE.

S. HORSLEY.

J. PLANTA.

5 P

Vol. LXVII.

'

V

r f i - ■

;

-

. • ;

*

/

C «S9 )

PRESENTS

MADE TO THE

ROYAL SOCIETY

From Nov. 1776 to June 1777;

WITH

The NAMES of the DONORS.

Donors. > . Prefen ts.

Omitted in thelaft Volume.

John Reinhold Forfler, LL.D. F.R. S.
*776.

June 26. The Editor.

Mr. Valemont de Bomare.
Society of Antiquaries.

A large colle&ion of Birds and Fifhes, in
Spirits, chiefly nondefcripts, brought from
the South Sea and the Cape of Good Hope.

The 54th Vol. of the Philofophical Tranf-
a&ions, printed at Wittenberg, 4*

Mineralogie, ou expofition du regne mine-
ral,

Prints publifhed by them.

Sir W. Hamilton, K. B. F. R. S.

Obfervations on the Volcanos of the Two

Sicilies, 2 vols.

fol.

Mr. John Seiferth.

Metallurgic Chemiflry,

8°

Forbernus Bergman, F. R. S.

Commentationes Chemicae,

4°

Mr. Charles de Geer.

Memoires pour fervir a l’Hiftoire des In-

fe&es,

4°

Society of Phyficians in London.

Medical Obfervations and Enquiries,

8°

Mr. Bernoulli, F. R. S.

Recueil pour les Aflronomes,

8°

—

Lifte des Aflronomes connus a&uellement

vivans,

8 3

Ant. Maria Lorgna,

Specimen de feriebus convergentibus,

4°

Mr. D’Apres de Mannevillette.

Le Neptune Oriental,

fol.

Board of Longitude.

Nautical Almanack for 1778,

8°

Mr. Colombier.

Preceptes fur la fante des gens de guerre, 8°

- ■ — • — —

Code de Medicine Militaire, 5 vols.

12°

5 P 2

Nov.

[ 86o ]

1776. Donors.

Nov. 7. Academy of Stockholm.

Mr. Schaeffer. F. R. S.

M.Jout.Mar. de Moyrie deMayla,
Mr. Bailly.

L’Abbe Rozier,

Mr. Morand.

Mr. Dion du Sejour, F. R. S.
Bequeathed by the late Dr. Maty.

34. Dr. Avenbrugger.

Mr. de Lelyveld.

Ffelice Fontana.

Mr. Le Meunnier.

J. Bernard.

Mr. Geo. Atwood*

Dec, 5. Mr. Bowyer.

Mr. Nichols.

19th, Count ae Sails, F. R.S.

Mr. Wallott.

Mr. J. H. de Magellan, F. R.

Prefent*.

Swediih Tranfa&ions, N° 3, 4, of .1775, and
N® 1, 2, of 1776. 8°

Abbildung des befiaendigen Elle&ricitaettrae-
gers^ 40

Hiftoire Generale de la Chine, 4*

Hiftoire de PAftronomie Ancienne, 4°
Journal de Phyfique, for Jan. Feb. March,
April, May, June, 1776. 4*

Du Charbon de Terre, & des fes mines, fol*.
Effais fur les Phenomenes, 8*

Two Portraits, one of Defcartes, the other
of Fontenelle.

Experimentum nafcens de rcmedio fpecifca>
fub figno fpecifico in mania virorum, 8®*

Effai fur les moyens de diminuer les dan^
gers de la Mer, 8®"

Nouvelle vue fur la proportion du code d’ua
Quarre parfait avec fa diagonale, 8*^

Ricerche Filofofiche fopra la fifica animale,
tom. I. 4®

L’efprit des Ufages & descoutumes des dif-
ferens peuples, 3 vols. 8*

Several Medical Thefes, 40

Defcription of Experiments to illuflrate a
Courfe of Lettures, 8*

Differtation on the Epiflles of Phalaris, 8®

Supplement to Dr. Owen’s Critica Sacra, 8®

An Appendix to the firlt Edition of the Ori-

gin of printing, 8°

A Verfion of the Pfalms of David into the
language of Engadine, 8°

Methode dirette de demelir l’effet de la
variation de l’obliquite de l’Eliptique, 40
1. , Differtatio de monftris, 40

Thefis Univerfse Philofopbire, SQ

177-0

Ian. 9. , Mr. Bemetzneder,
Nic. Andria.
Giamb* Beccaria.

¥

Taite de Mufique, 8°

Trattato delle acque Minerali. 8®

Della Ellettricita. terreftre atmofpherica a
cielo fereno, 4®

Affemble'e publique de la SocieteRoyale des

Sciences de Montpellier, 4®

Tan*

[ 86i J'

Jan. 16*

23.

Feb. 6.

*3-
20.
JMarch 6,

23.

20.

Donors.

Board of Longitude*

Dr. Cullen.

Prince Bifcari,

Mr. Henry Home.

Felice Fontana.

Royal Academy of Pruftia.

The Archbifhop of Canterbury.
Mr. Lefcallier.

The Editor.

Mr. Needham, F. R, S.
Edinburgh Society.

L’Abbe Coyer, F. R. S*,.

Mr. Donne.

Prefen ts.

Defcription of an engine for dividing Mathe-
matical Inftruments,

Firft lines of the practice of Phyfick, 8®
Difcorfo Academico fopra un’ antica Ifcri-
zione, 4®

The Gentleman Farmer, 8*

Recherches Phyfiques fur Fair nitreux et fur
Pair dephlogiftique, S*

Recueil de Tables Aflronomiques, 8®

A lift of various Editions of the Bible, 8°
Vocabulaire des Termes de Marine, 40
The 55th vol. of the Philofophical Tranf*
printed at Wittenberg, 40

Idee Sommaire, ou vue generale du Syfteme
Phyfique et Metaphyfique, 8?

3 Vols of their Medical and Philofophical
Commentaries, 8®

Commentaire fur le Code criminel d’Angle-

terre,

Britifh Mariner’s Aftiftant,
Eftay on Book-keeping,
D® on Plane Geometry,

Cha. Pet. Layard, M. A.

Court of Diredl. of the E. I. Comp
Mr. Gibelin.

PAbbe Rozier.

The Biftiop of Oxford.

Mr. George Forfter, F. R. Sa,

Dr. Wolf.

Abb, Spallanzani.
April 10. Board of Longitude,
Mr. Lewis Lochee,

Daniel Titio,

8°
8°
8°
8°

D° on Vulgar and Decimal Afithmetick, 8°
A Sermon on the death of Dr. Maty, 40
, A Code of the Gentoo Laws, 4®

Experiences fur difterentes efpeces d’air,
tom. IL IIL 8°

Journal, de Phyfique, for July, Auguft,
Sept. Oft. Nov. Dec. 177 6, 40

The Life of William of Wykeham, 8°
An Account of a Voyage round the World,
in 1772, 3 & 4, 2 vols. 40

Many fpecimens of various Salts and Strata
of the Salt Mines in Poland.

Opufculi di Phyfica Animate, 2 vol. 8®
Nautical Almanack for 1779. 8°

Syftem of Military Mathematicks., 2 vols. 8°
Eftay on Military Education, 8°

Parus minimus Polonorum Remiz,Bononien-
ftum PendUlinus, deferiptus, 4°

17. Rev,.

[ 862 ]

1777* • Donors.

1 7. Rev. Dr. Prieftley, P. R. S.

Abbe Hondou.

J. Miller.

24. Hugh Brown.

Samuel Wegg, Efq. F. R. S.

May 8. John Howard Efq. F. R. S.

15. Rev. Mr. Tooke.

Captain Cook, F. R. S.

2 9. Board of Longitude.

Mr. J. Chandler, F. R. S.

June 12. Royal Academy of Sciences at
Paris.

Thomas Aftle, Efq. F. R. S.

19. Berlin Academy.

Mr. Bernoulli.

Le Baron Hupfch.

Mr. Cavallo.

Prefent*.

Experiments and obfervationi on different
kinds of Air, tom. III. 8°

Six Mathematical Tra&$# 8°

Botanical Prints, N* XV. fol.

True principles of Gunnery explained, 40
Meteorological Diary kept at York Fort,
Hudfon’s Bay, fol.

State of the prifons in England and Wales, 40
Pieces on Sculpture, and on the Statues of
Peter the Great, 4®

An Account of a Voyage round the World
in 1772, 3 & 4. 2 vol. 4*

Nautical Almanack for 1780, 8°

Meteorological Diary, fol.

Connoiffance des Temps, pour Pannee
1778, 8°

A Catalogue of the MSS. in the Cottonian
Library, 8°

Nouveaux Memoires. Annee 1774, 40

Nouvelles Literaires de divers pays, 8°
Relation de la decouverte d’un remede
efficace contre la maladie contagieufe
des betes a comes, 6 copies, 8*

A Treatife on Eleftricity, 8*

A N

C 863 ]

A N

INDEX

TO THE

SIXTY-SEVENTH VOLUME

OF THE

PHILOSOPHICAL TRANSACTIONS.

A.

yfBSG E S S, an account of a hard fubftance extra&ed from one, in a woman’s groin*

^ p. 461 — 463. The fubftance caufed by a peg of wood which fhe had fwallowed
fixteen years before, p. 462, n .

Ackbar, the emperor, faid to have built an obfervatory at Benares, p. 604. An account
of it, p. 598 — 607.

Adriatic , an account of its tides, p. 145—161.

ASther, degree of cold produced by its evaporation under the receiver of an air-pump
whilfl exhaufting, p. 646 — 648.

Africa , an account of a journey into Africa from the Cape of Good-Hope, and a de-
fcription of a new fpecies of cuckow, p. 38. Journey undertaken in Auguft 1775,
ibid. Seafon fo exceeding dry that the inhabitants quitted their country-feats, p. 39.
Cattle perifhed for want of grafs and water, ibid. Vegetables of all kinds burnt up,
ibid. Animals met with and hunted on the journey, p. 39, 40. Sec Sparrman, Cuckow .

Air, in what manner it may be affe&ed by rain, p. 244. An aftive folvent of water,
in proportion to its drynefs, p. 245. 257. Water may exifl in air in three hates,
p, 257. Remarks on thefe different hates of water exifting in air, p.257 — 259.
Concerning air in mines, p. 412. A comparative view of the temperature of the air
at Liverpool during the years 1772, 1773, 1774? and 1775, p. 247 — 250. Relative
weight of air and water, p. 560. Expanfions of common air do not keep pace with the
c dilatations

[ 364 ]

dilatations of quickftlver, p. 695. Elaftic force of moift air fuperior to that of dry,
p.705. 712 — 714. Concerning the elaftick force of air, p.748, 749. 755, 754. An
experiment to determine hydroftatically the fpecific gravities of air and quickfilver,
with a given temperature and prefibre, and remarks thereon, p. 557 — 570. Expe-
riments on the expanfion of air in the manometer, p.689—696. Thermometricai
fpaces compared with thofe of the manometer, p. 697. Experiments for determining
thea&ual expanfion of common air in the manometer affedcd by the heat of 212°,
P. 698—7:5.

Air-pump , an account of fome experiments made with one, on Mr. Smeaton’s principle ;
together with fome experiments with a common air-pump, p.614. Defcription of
Mr. Smeaton’s pear-g2ge, p.614 — 616. Air in the pump expanded 4000 times*
p.617. Enquiry from whence this .great fuperiority of expanfion could pro-
ceed, p. 617. Difagreement between the pear-gage and the other gages, p. 6i8#
622. Difagreemet accounted for, p. 622—644. Experiment in which the apparatus
was made as free from moilfure as pofiible, p. 624. Near agreement between the
pear-gage and the barometer, p. 625. To difcover whether a vapour from moifture
might not be contained in the fubftances ufed, p. 625 — 627. Elaftic vapours arofe
from the leather and box-wood ufed, and influenced the bc.rometcr-gages, p. 627.
Pear-gage not affedted by the vapour, ibid. Experiments on leather, allum, oil, and
tallow, to find from which the vapour chiefly arofe, p. 628. Arofe principally from
the leather, ibid. To determine that the moifture in the leather gave the vapour,
p. 629, 650. The eifedl of vapour arifing from fmall quantities of fluids, and from
fome fubftances, p.630, 631. Wet leather, ufed to connedl the receiver and plate,
prevents the pump from exhaufting to any confiderable degree, p. 652. Different
degrees of heat atfedl exhauftion, p. 633. Comparative excellency between the pump
on Mr. Smeaton’s principle, and a common one, p. 633, 634. The effedl of water
ufed in the barrels of pumps to make the piftons move air tight in them, p. 634,
635. Remarks concerning Mr. Smeaton’s pump not exhaufting to as great a de-
gree as the pump here ufed, p. 635 — 637. Further experiments made with the fame
air-pump, the refult of which were different from the former, p. 637 — 646. Degree
of cold produced by the evaporation of aether under a receiver whilft exhaufting,
646—648.

Alps. An account of Mont Saleve, p. 515, w. 527. An account of the Mole,
p. 533 — 539. Barometrical obfervations to afeertain the heights of the Alps,

P* 5 1 3>

Alte Segen , a mine in the Hartz, its height determined by barometrical obfervations,
p. 421, 422. 441—443.

Altitudes determined by the barometer, 515— 532* 53° — 54^* 549? 550, 552 — 554*
592 — 597. Rule for meafuring fuch heights, p/683. 687. 734, 735. 757, 758.
762, 763, k. The rule which anfvvers in middle latitudes will not in the frigid and

torrid

I 865 ]

torrid zones, p. 742— >756. Remarks on the error of the rule in the tables of com-
putation, and a method of bringing the theory of the barometer to greater perfection,
p. 759 — 770. Precepts and tables for making the calculations, p. 571 — 591.

Computations of barometrical obfervations made on various heights, p, 773 787.

Anetnouies, See Sea anemmies.

Angles, An account of a new infirument for meafuring fmall angles, called the prifmatic
micrometer, p. 799. See Micrometer,

Antelopes , an animal of that fort, frequently hunted in Africa, p.40

Apparatus, Defcription of one for further illufirating the Franklinian theory of the
Leyden bottle, p. 99, 100. A fimple ele&rical apparatus, by which almofi every
article may be examined with the utmoft facility, p. 1 18. Obfervations and pre-
cautions in the ufe of it, p.119, 120. The eleftricity of various fubilances dif-
covered with it, p. 122 — 126. Remark on the rubbers ufed, p. 127 — 129. Appa-
ratus for determining the annual evaporation in Liverpool, p. 245, 246.

Apples . Method of raifing pine-apples in water, p. 649 — 6^2.

Arabic . A tranfiation of a paifage in Ebn Younes ; with fome remarks thereon, p.23i«
See Ebn Younes.

Arcs, Computations of the lengths of circular arcs by means of infinite feriefes, derived
from their tangents, p. 194 — 199. Computations of an arch of thirty degrees,
p. 199 — 203. Computation of an arch of forty-five degrees, p. 203-— 214. Com-
putation of the feries which exprefies the time of the defcent of a pendulum through
the arch of a circle, p. 2 15 — 230.

Articles (mathematical) leading to a clear and fatisfa&ory consideration of the motion
of the earth’s axis, p. 267 — 288. How the joint centrifugal force of the particles of a
fpheroid or cylinder, having a rotatory motion about any momentary axis, is com-
puted, p. 289 — 295.

Afronomy , the ancient Bramins had a knowledge of it, p. 598. 601 — 606.

Atmofphere, obfervations on its ele&ricity, p. £o. A quantity of ele&ricity in the at-
mofphere at all times, ibid. The eledlricity of the atmofphere, and of fogs of the
fame kind, ibid. Evaporation confidered as a tefi of the moifiure or drynefs of the
atmofphere, p. 244. See Evaporation, Atmofphere of Peru confiantly obfcured
-with vapours during part of the year, and the whole country involved in thick fogs,
p. 257, 258. Depth of rain not a true index of the moifiure or drynefs of the atmof-
phere, p. 250 — 252. Why much rain gives no more moifiure to it than a little,
p. 251, Atmofphere amazingly clear in the Eaft Indies, p. 604.

Atmofpherical ele6lrometer , defcription and ufe of one, p. 48, 49.

Aubert , ( Alexander , Efq;) his attefiation concerning Dr. Malkelyne’s invention of the
pi ifmaric micrometer, p. 8i£.

Axis, the earth’s, mathematical articles leading to a clear and fatisfa&ory confideration
of its motion, p. 267 — 288. How the joint centrifugal force of the particles of a
Vol. LX VII. 5 fpheroid

[ 866 ]

fpheroid or cylinder, having a rotatory motion about any momentary axis, is com-
puted, p. 289 — 295.

B.

Barker (Sir Robert) his account of the Bramins’ obfervatory at Benares, p. 598. See
B rami ns' Obfervatory .

Barker (Thomas, Efq;) an extrad of his regiller of the barometer, thermometer, and
rain, at Lyndon, in Rutland, for the year 1776, p 350. See Lyndon.

Barometer . Experiments and obfervations made in Britain, in order to obtain a rule
for meafuring heights with a barometer, p. 653. Mr.De Luc the molt fuccefsful in
meafuring vertical heights with the barometer, p. 654, 655. Rule deduced from
his obfervations on Saleve, p. 655, 656. Expanfion of quickfilver in the tubes of his
barometers refulting from the Saleve obfervations, p.656 — 658. Defcription of the
barometer with which Col. Roy’s experiments were made, p. 658, 659. Experi-
ments on the expanfion of quickfilver, p. 659 — 681. Rate of expanfion of a column
of quickfilver in the tube of a barometer, p. 682. Conftrudion and application
of a table of equation for the expanfion of quickfilver in the tubes of barometers,
p, 683 — 686. The equation to be applied to the obferved height of quickfilver in
the barometer, from 15 to 31 inches; and for differences of temperature extending
to 1020 of Fahrenheit; whereby the column is reduced to the height it would have
flood at in the temperature of 320, p. 687. Experiments on the expanfion of air in
the manometer, p. 689 — 696. Thermometrical fpaces compared with thofe of the
manometer, p. 697. Experiments for determining the adual expanfion of common
air in the manometer affeded by the heat of 2120, p.698 — 715. An account of
barometrical obfervations made in Britain, wherein they are compared with fome
others of the fame kind made in diflant countries, p. 715 — 749. Principles on
which the table of equation for the heat of air was conflruded, p. 749 — 759. Re-
marks on the error of the rule in the tables of computation, and a method of bringing
the theory of the barometer to greater perfedion, p.759 — 770. The equation de-
pending oh the temperature of the column of air, and its elevation above the fea„ as
denoted by the mean height of mercury in the inferior and fuperior barometers,
p. 771. Computations of barometrical obfervations made on heights in and near
London, p. 773. Computations of thofe made on heights near Taybridge in Perth-
fhire ; and of thofe near Lanark, p.775. Computations of thofe made on heights
near Linhoufe ; and of thofe near Carnarvon in North Wales, p. 779. Computations
of part of Mr, De Luc’s barometrical obfervations, anfwering to the coldeft: and
hotteft temperatures of the air, p. 7 1 1—784. Mr. De la Caille’s barometrical obfer-
vations at the Cape of Good-hope, p.784. Computations of barometrical obfer-
vations made on heights that have not been determined geometrically, p. 785. Com-
putations of Mr.Bouguer’s obfervations in Peru, p. 787.

Barometer*

[ S67 j

Barometer, fiate of it at Lyndon, in Rutland, during the year 1776, p, 550. At Brit-
t°I, p. 353. At London, for each month throughout the fame year, p. 3 5 B — 301.
Created, lead, and mean height, in each month, p. 382. Heights determined by
barometrical obfervations. See Heights. Defcription of a portable barometer,
p. 658, 659. Eiredt of winds on the barometer, p- 751 — 753. Fixing the fcale of
barometers with citterns recommended, p. 405, 406. Obfervations made in Savoy,
in order to afcertain the height of mountains by means of the barometer ; being an
examination of Mr. De Luc’s rules, delivered in his Recherches fur ks Modifications de
V Atmofphere, p. 513. See Mountains. Rule for meafuring heights with the baro-
meter, p. 686, 687. 734, 733. 757, 758. 762, 763, n. The rule which anfwers
in middle latitudes, will notin the frigid and torrid zones, p. 742 — 756.

Barometer tubes dilate much more than folid glafs rods, p 663, 664.

Barometrical obfervations on the depth of the mines in the Hartz, p. 401. Correfponding
obfervations taken, p. 405, 428, 429. Obfervations in places where the height is
afcertained, p. 408 — 424. In the Dorothea, the Caroline, and the Benedift, in the
environs of Ciautthal, p.408 — 412. In the Kaunkuhl, at the Ramelfburg near
Goflar, p.417—419. At Alte Seegen, in the valley of Bremeke, p. 421, 422.
K ear Lasfelde, in the valley of Otterode, ibid. The fubterraneous geometer’s method of
finding the depths of mines, p. 423, 424. Obfervations determing the height of fome
points of the Hartz, not verified by geometrical furvey, p. 425—429. The height
of the Brocken above Oder-brucke, p. 429. That of Oder-brucke above Ciautthal,
ibid. That of Ciautthal above Gottingen, ibid. And that of Gottingen above
Hanover, ibid. Elevation of the Brocken above Hanover, ibid. Remarkon thefe
obfervations, p. 430. A detail and calculations of barometiical obfervations made
at the Hartz, in October 1776, p. 431—449. Obfervations on the mines of Clautt-
hal, p. 431 — 435. At the Rameliberg, p.436 — 440. Obfervations at two points
geometrically determined on the outfide of the mountain, relatively to the mine of
Alte Seegen, p. 441 — 443. Obfervations to determine the height of the Brocken,

with refped to Gottingen and Hanover, p. 444 — 449. Barometrical obfervations

made in Savoy, to afcertain the heights of mountains, p. 513, &c. Precepts and tables
for making thefe barometrical calculations, p. 571 — 597.

Bajlard, ( William , Efq;) on the culture of pine-apples, p. 649. See Bine-apples.

Beafis of prey, frequently feen in Africa, p. 39, 40.

Beech-trees . The flourifhing ttate of one that had been frequently walked and rubbed,
compared to others of the fame nature, p. 12 — 14.

Bee hives, wild, how men are conduced to them by the Hcney-Guide, a curious fpe-
cies of cuckow, p. 43— 45. See Cuckovj .

Bees , difcoveries on the fex of them, explaining the manner in which their fpecies is
propagated ; with an account of the utility that may be derived from thofe difcoveries
by the actual application of them to pradtice, p. 15. Mode of propagating their

5 Q~2 fpecies

[ 868 ]

fyecies yet undifcovered, p. 13, 16. Never deiefted in the aft cf copulation, p. 16.18.
Their fecundation is by an impregnation from the males, p. 17, 18. 20. Drones
have fome refemblances to the male organs of generation, p. 18. The different fexes
that conftitute the republic of bees, p. 19. Concerning the fex of the working-
bees, p. 19, 20. Drones difcovered as fmall as common bees, p. 21. 2 5. Drones
well furnilhed with feminal liquor, and fecundating organs, p. 22. Naturaliffs who
rejeft the ufe of drones in the propagation of bees had no knowledge of thofe fmall
ones, ibid. An experiment proving that the eggs of the queen-bee arc fecundated
by the males, p. 22, 23. How they are impregnated, ibid. Another experiment in
proof thereof, p. 24, 23. Drones have no fting, p. 25, 26. A third experiment, in
which the fvvarm was entirely cleared of the males, and in which the eggs of the
queen-bee produced nothing, p. 26. Bees all quit their hive on being difappointed
of their young, ibid. They attempt to enter the hive of another fwarm, and the
queen is fiain in the engagement, p. 26, 27. The great defire of perpetuating their
{pecies probably induces them to go to the other hive in fearch of males, p. 27. A
fourth experiment, (hewing that the male-bees muff impregnate the eggs to produce
young ones, p.27,28. Queen-bees produced from the common eggs, p. 28 — 30.
The working-bees have the power of making a queen of any worm in the hive,
p. 3 o, 31. The received opinion that the queen-bees are produced from a particu-
lar kind of egg, erroneous, p. 31. What advantages may accrue to the public from
thefe obfervations, p. 31, 32.

Benares, an account of the Bramins obfervatory there, p. 398. See Bramins * Ob/erva -
tory .

Benedict, a mine in the Hartz ; its depth determined by barometrical obfervations,
p.408—412. 43$.

Bengal , govornor of, grants a peace to the Boutaners, p. 46S. Enters into a treaty of
commerce with them* p. 469. Tranllation of the letter he received from the Tayihoo
Lama, p. 489 — 492.

Bi/on. The North American Bifon, the fame as the great buffaloe in the Wilds of
Africa, p. 40.

Bodies. A new theory of the rotatory motion of bodies affefted by forces dilturbing
fuch motion, p. 269 — 295, Singulur method of bellowing dead-bodies among the
Thibetians, p. 478.

Bogle (Mr.) fent to the court of Thibet, to negotiate a treaty of commerce with the
Boutaners, p, 469. His defcription of their country, &c. p. 469- — 472. And cha- -
rafter of the Tayihoo Lama, p. 479.

Boiling point, experiments to determine it in thermometers, p. 818 — 833. Rules to be
obferved in adjufling the boiling point of thermometers, p. 843 — 853.

Bofco'vich , Abbe, his account of a new micrometer and megameter, p. 789 — 79S.

812= — 815..,

Bottle

[ 869 ]

Bottle , Leyden, Dr. Franklin’s theory of it further illuftrated, p. ioo, &c.

Bouguer , Mr. Computation of his barometrical obfervations in Peru, p. 787.

Boutan , the kingdom of Thibet fo called, p. 466. An account of it, p. 465', &c.

Boutaners , .an account of their firft meeting with the Europeans at the attack of Cooch
Behar, p.467, Their great furprize at each other, p. 467,-468. The Boutaners,
conquered by the Europeans, fue for peace, p. 468.

Box-wood, itseffe# in experiments with the air-pump, p. 626.

Bramins’ Objervatory, at Benares, an account of it, p. 598. Ancient Bramins had a
. knowledge of agronomy, 593. 604 — 606, A number of curious inftruments in their-
obfervatory in the greateft prefervation, p, 599. Said to have been ere&ed two
hundred years ago, ibid. The confirmation and fituation of thefe inftruments, p. 599.
—601. Defcription and life of them, p. 601 — 604. 607. This Obfervatorv faid
to have been built by the emperor Ackbar, p, 604.

Brijlol, an extra# of a meteorological journal kept there for the year 1776, p. 373.
See Meteorological Journal .

Britain . Experiments and obfervations made in Britain, in order to obtain a rule for
meafuring heights with the barometer, p. 653. S qq Barometer.

Brocken in the Hartz, its height above Hanover determined by barometrical obfervations,
p. 429. 444—449.

Brownrigg , Dr. his obfervation on the evaporation of fome parts of England, p. 233.
Not correfpondent with that at Liverpool, ibid.

Buffaloes , great ones in the wilds of Africa, p. 40. The fame as the North American
Bifon, ibid.

Buildings . Some account of the Thibetian buildings, p. 479.

C,

Cabbage bark tree of Jamaica, its defcription and ufe, p. £07—^12.

Cantons electrometer. Experiments with Mr. Hemming’s electrical cylinder fome days
after ufing it, on the balls of Canton’s electrometer, p. 109 — 113. New eleCt ricai
experiments and observations j with an improvement of Mr. Canton’s electrometer^
p,. 383. See Eleclrical experiments.

Cape of Good- Hope, an account of a journey from thence into i\frica, and a defcription of a
newfpecies of cuckow, p. 38. Se£ African Cuckow. Mr. De la Caille’s barometrical
obfervations there, p. 784.

Cards , painted with different water-colours, electrical experiments on them, p. 392—
394-

Caribbees ... Defcription of the Jefuits Bark tree of the Caribbees, p. 504—506.

Carnarvon. Computations of barometrical obfervations made on heights near,
P- 779*

Caroline, a mine in the Hartz, its depth determined by barometrical obfervations,
p.408—412. 434.

Cafe of the falling woman in Rofsfhire, p. 1 — 1 1.

Cata

[ 37o ]

Cat . A coated phial may be charged with elettrical fparks from the back of a cat,
flrong enough to pierce a hole through a card with its difcharge, p. 396. A fpccies
of pole-cat (Viverra Putorius), found in Africa, p. 40.

Cavallo , Mr. Tiberius, his account of fome new ele&rical experiments, p. 48. Sec
Electrical experiments. His experiments and obfervations on Mr. Volta’s ele£lric I
machine, p. 116 — iiB. His new electrical experiments and obfervations ; with an
improvement of Mr. Canton’s electrometer, p. 388. See Ele&rical experiments.

Cavcndifoy Mr. accounts for a difagreement between the pear-gage and the other gjges
in an air-pump, p. 622 — 624.

Chocolate y on its electricity ; and the reftoration of that property to it, when loll, by
melting it together with a fmall quantity of olive-oil, p. 9 j. — 97.

Cijlerns. Fixing the fcale of barometers with citterns, recommended, p.405, 406.

Claujlhaly in the Hartz, depth of fome mines there determined by barometrical obferva-
tions, p.408 — 412. 431 — 435. Its height above Gottingen determined by the

barometer, p. 429. 444 — 449.

Clock, A pendulum-rod of folid glafs dilates much lefs than a fteel one, p. 698,
699.

Coated phial may be charged with eleCtrical fparks flrong enough to pierce a hole through
a card with its difcharge, from a piece of new flannel, a hare’s (kin, or a piece of
paper, p. 396.

Colours . An account of perfons who could not diflinguifh colours, p. 260. — Harris,
who had othervvife a good fight, difcoverecl a want of the idea of colours at four
years of age, p. 261. Why he might not obferve this defcCl earlier, ibid. Could
not difeern the difference of colour in cherries, p. 262. He could only guefs the
name of any colour, except diflinguifhing white from black, or black from any.light
or bright colour, p. 262, 263. Fie could diflinguifh a ftriped ribbon from a plain
one, but could not tell the colours, p. 26 2. Was very defirous cf undemanding the
nature of light and colours, p. 263. Fie had two brothers, who likewife had no idea
of colours, ibid. Account cf one of them, p. 263 — 265.

Colours . Ele&rical Experiments on water-colours, p. 392 — 394. On oil-colours,

p. 394, 393.

Committee . The report of the committee appointed by the Royal Society to confider of
the beft method of adjufting the fixed points of thermometers ; and of the precautions
neceffary to be ufed in making experiments with thofe inflruments, p. 816. See
Thermometers .

Cooch Behar . Europeans and Boutaners firft met at its attack, p. 467. Their great
furprize at each other? p. 467,. 468. Boutaners, conquered by the Europeans, fue
for peace, p. 468,

Copernicus , an account of a portrait of him, prefented to the Royal Society by Dr.Wolf,
p. 33. Copied from an original in the poffeflion of Mr. Fluflarzewfki, p. 33, 34*
A portrait of hirfi in the great church at Thorn, p. 34. Compared with Mr. Huf-

farzewfki’s,

[ 8-7 x 3

farzewfki’s, p. 34, 35. The latter is at lead 130 years old, ibid. Hidcry of this
portrait, p. 36, 37. Great likenefs between the copy and original, p. 37.

Copulation , bees never detected in that adt, p. 16. 18.

Coftard , Rev. Mr. George, his translation of a padage in Ebn Younes ; with fome re-
marks thereon, p, 231. See Ebn Younes,

Cove, the Thibetians hold it in great veneration, p. 478.

Covj-tails, remarkable ones produced in the kingdom of Thibet, p. 484. Their ufe,
p. 484, 485'. Defcription of the bead, p. 484.

Creek Fat crick, or Peter’s Rock, a volcanic-hill near Invernefs, an account of it3
p. 385—387.

Cruquius , his obfervation on the exhalation of water at Delft in Holland , p. 252.

Cuckonv, Honey-guide , or Cuculus Indicator, a curious fpecies of cuckow in the interior parts
of Africa, p. 43. Smaller than the European cuckow, ibid. Men and beads are
conduced to wild bee-hives by this bird, ibid. Its motive and method of difcovering
the bee-hives to men, p. 43 — 45, Accufed of fometimes conducting its followers to
wild beads and venomous ferpents, p. 45. Defcription of the Honey-guide’s ned,
p.45, 46. Defcriptio cuculi indicators, p. 46, 47.

Cuculus Indicatory or Honey-Guide, a curious fpecies of cuckow in the interior parts of
Africa, p. 43. See Cuckovo.

Cylinder . Experiments with Mr. Hamming’s eledlrical cylinder, for fome days after
ufing it, on the balls of Canton’s eledlrometer, p. 109 — 113.

Cylinder or fpheroid. How the joint centrifugal force of the particles of a fphefoid or
cylinder, having a rotatory motion about any momentary axis, is computed, p. 289

Davenport, Ann, her remarkable cafe, p. 438. Miferable date of the patient, p. 459.
460. An abfcefs in her groin opened, p, 460. A fecond formed, and opened, ibid.
Several holes in her belly caufed by a mortification, p. 461. A third abfcefs formed,
which was left to open of itfelf, ibid. A hard fubdance extracted therefrom, p. 462.
An account of the extraction, p. 462, 463. The fubdance taken from her caufed by
a peg of wood which fhe had fwallowed dxteen years before, p. 462, n. Patient in
a fair way of recovery, p. 463. The minider’s certificate of the truth of the cafe,
p. 464.

Days. Number of fair and frody days in Briftol in the year 1776, p. 354.

Dead bodies , a fingular method of bedowing them among the Thibetians, p. 478.-

Debravo, Mr. John, his difcoveries in the fex of bees, explaining the manner in which
their fpecies is propagated; with an account of the utility that may be derived from
thole difcoveries by the adtual application of them to pradlice, p. 15. See Bees .

Deer. Mulk deer common in the mountains of Thibet, p. 485, 486.

Be la Cailles , Mr. his barometrical obfexvations at the Cape of Good Hope, p. 784.

Dtlai -

I 872 1

Delai Lama, a defcription of his country, p.469 — 471. ^Ke is the great objett of
adoration of the heathen Tartars, p. 474—476.

Delft , in Holland, obfervation on the exhalation from waters there, p. 252.

De Lucy Mr. John Andrew, his barometrical obfervations on the depths of the mines
in the Hartz, p.401. See Barometrical obfervations . On the expanfian of quick-
silver in the tubes of barometers, p. 683, 684. Concerning his barometrical obfer-
vations on Saleve, p. 715, 7 16—729, See. Mr. De Luc the mod fuccefsful in
meafuring vertical heights with the barometer, p. 654, 655. Rule deduced from
his obfervations on Saleve, p. 655, 656. Iixpanfion of quickfilver in the tubes of
his barometers refulting from the Saleve obfervations, p. 656 — 658. Computations
of part of his barometrical obfervations, anfwering to the coldelt and hotted tem-
peratures of the air, p. 781 — 784. His method of adjuding the boiling point of the
thermometer, p. 832. An examination of the rules delivered in his Ruherches fur let
Modifications de V Atmoff>here> by obfervations made in Savoy, in order to afeertain the
height of mountains by means of the barometer, p. 513. See Mountains.

Depths of mines, ineafured by the barometer, p.401 — 409. The fubterraneous geo-
meter’s method of finding thefe depths, p. 423, 424. Precepts and tables for calcu-
lating any acceifible heights or depths from barometrical obfervations, p. 571 — 591-

De Saujfuret Mr. his barometrical obfervations to afeertain the height of the Mole,

P- 549’ £S°*

Diameters. The ratio of the diameters of the earth, p. 767.

Dicquemare, the Abbe, his third elTay on fea-anemonies, p. 56. See Sea-anemonies .

Dobfon, Dr. his obfervations on the annual evaporation at Liverpool ; and on evapo-
ration confidered as a tell of the moiiture or drynefs of the atmofphere, p. 244.
See Evaporation.

Dollondy Mr. his letter concerning Dr. Mafkelyne’s invention of the prifmatic micro-
meter, p. 813 — 815.

Dorotheay a mine in the Hartz, its depth determined by barometrical obfervations^

p. 408— 412. 431-4 35-

Drink. An account of a woman living without food or drink, p. 1. See Woman.

Drones have fome refemblances to the male organs of generation, p. 18- Drones as
fmall as common bees, p. 21, 25. Drones well furnifhed with feminal liquor, and
fecundating organs, p. 22, 23. They have a ftiare in the propagation of bees, p.
22 — 28. Drones have no ding, p. 23, 26.

Drynefs or moidure of the atmofphere ; evaporation confidere.d as a ted of it, p. 244,
See Evaporation.

£.

fLarth. Annual evaporation from the earth, only a fixth part of what it is from water,
p. 233. The exhalation from the earth is about a fixth part of what defeends in rain,
p. 234, Some mathematical articles leading to a clear and fatisfaftory confiaeration

of

[ 873 ]

of the motion of the earth’s axis, p. 267 — 288. How the joint centrifugal force of
-the particles of a fpheroid or cylinder, having a rotatory motion about any momen-
tary axis, is computed, p. 289 — 29-5. The ratio of the earth’s diameters, p, 767.
Bed method of determining the figure of the earth, ibid.

Eafi Indies . The atmofphere amazingly-clear there, p. 604..

Ebnfounes . Trandation of a paffage in Ebn Younes; with fome remarks thereon,
p. 231. Numbers in the manufcript fuppofed to be different from what they were
in the original tables, ibid. A midake in the Arabic letters and figures eafily made
by a perfon ignorant of his fubjeCt, p. 232. An indance of this fort, ibid. Dif-
ferences in the manufcript obfervations, and the calculations by modern tables ac-
counted for, p. 232 — 240. A translation of the Arabic paffage entire, p. 240—
24 3-

lulipfes of Jupiter’s firft fatellites, obferved during the lad ten years, relatively to the
difference of longitude at Paris and Greenwich refulting therefrom ; with a com-
parative table of the correfponding obfervations of the fird fateliite, made in the
principal obfervatories, p. 162 — 186.

Edinburgh , computations of barometrical obfervations made on heights near there,
P- 777-

Eleftrical Experiments , an account of fome new ones, p. 48. Defcription and ufe of the
atmofpherical electrometer, p. 48, 49. Part of a journal of obfervations on the
eledricity of the atmofphere, p. 50. A quantity of electricity is at all times in the
atmofphere, ibid. The electricity of the atmofphere or fogs is always of the fame
kind, ibid. The dronged eleCtricity is in thick fogs ; the weaked in cloudy weather,
ibid. Defcription of the electrometer for the rain, p. 51, 52. Experiments made
with a giafs tube hermetically fealed, and having fome quickfilver inclofed in its
cavity, p, 53—55'. New eleCtrical experiments and obfervations, with an improvement
ofMr, Canton’s electrometer, p.388. The giafs plate ufed in the following experiments
coated with fealing-wax, ibid. Experiments on Mr. Volta’s plates, commonly called
a machine for exhibiting perpetual eleCtricity, p. 389—392. Experiments on water-
colours, p. 392 — 394. On oil colours, p. 394, 395. Promifcuous experiments,
p. 396, 397. On a piece of new white flannel, tied round the globe of an elec-
trical machine, p. 397, 398. On a phial, the infide coating of which was duck
with varnifh, p. 398, 399. Defcripiion of a pocket electrometer, p. 399, 400.

Elettri cal machine, experiments and obfervations on Mr. Volta’s, p. 1 1 6— : 18. Ex-
periments on his machine for exhibiting perpetual eleCtricity, p. 389 — 392.

Electrical cylinder (Mr. Hemming’s), experiments with it on the balls of Canton’s elec-
trometer, fome days after ufing it, p. 109 — 113.

Electricity . Experiments and obfervations in EleCtricity, p. 85. Remarks on the

eifeCts of lamp-black and tar, or lamp-black and oil, as protectors of bodies from the
droke of lightning, p. 85—89. Similar effeCts produced by experiments in the artifi-
Voi. LX VII. 5 R cial

C S74 ]

cial elc&ricity, p. 8c— 9 r . Corollaries deduced from the above experiments and
observations, p. 91 — 94. On the eleftricity of chocolate, 94 — 96. The reftoration
of that property to it, when loft, by melting it together with a Small quantity of
olive-oil, p. 96, 97. Remarks on electricity, 97, 98. Obfervations on fome new
and Singular phenomena in excited and charged glafles ; with experiments made in
confequence of thefe phenomena, farther illuftrating the Franklinian theory of the
Leyden bottle, p. 98 — 1 16. A defeription of the apparatus conftrudled for that pur-
pofe by Mr. Henly1, p. 99, 100. Experiments and obfervations on Mr. Volta’s
machine, with remarks, p. 116 — 118. A Simple eleflrical apparatus, by which
almoft every article may be examined with the utmoft facility, p. 1 18. Obfervations
and precautions in the ufe of it, p. 1 19, 120. The eleflricity of various fubftances
difcoveredvvith.it, p. 1 22. Metals, ibid. Animal fubftances, p. 123. Vegetables,
p. 124, 125. Corallines, p. 125. Salts, ibid. Foflil and mineral fubftances,
p. 125, 126. Artificial fubftances, p. 126. Remark on the rubbers ufed, p. 127 —
129, Thoughts on the attion, influence, and effetts of electricity, p. 129 — 144.
Obfervations on the eledlricity of the atmofphere, p. 50. A quantity of eledlricity in
the atmofphere at all times, ibid. The eledlricity of the atmofphere and fogs of
the fame kind, ibid. Strongeft eledlricity is in thick fogs ; the weakeft in cloudy
weather, ibid. Eledlricity may be obtained by rubbing Smooth glafs with a rabbit’s
Skin, p. 397.

Eleffrometer, an atmofpherical one, its defeription and ufe, p. 48, 49. Defeription of
one for the rain, p. 51, 52. Defeription of a pocket one, p. 399, 400. Mr. Hem-
ming’s experiments with his eledlrical cylinder, fome days after ufing it, on the balls
of Canton’s electrometer, p. 109 — 113.

Emelman , Mr. his journey into Africa from the Cape of Good Hope, p. 38. See
Africa .

England , the evaporation of fome parts of it, p. 233. Not correspondent with that at
Liverpool, ibid.

Evaporation. Obfervations on the annual evaporation at Liverpool ; and on evaporation
confidered as a teft of the moifture or drynefs of the atmofphere, p. 244. Quantity
of rain failing not fo good a teft of the ftate of the atmofphere as evaporation, p. 244,
245. Method of determining the annual evaporation in Liverpool, p. 245, 246. Ex-
planation of the tables cf evaporation, p. 246. A comparative view of the evaporation,
rain, winds, and temperature of the air there, during the years 17 72, 1 773, 1774,
and 1775, p- 247—250. Depth of rain not a true index of the moifture or drynefs
of the atmofphere, p. 2£q — 252. Why much rain gives no more moifture to the
atmofphere than a little, p. 25 1. Annual evaporation at Liverpool, p. 252. Eva-
poration at London, p. 2 $2. Annual evaporation at London exceeds that at Liver-
pool, ibid. Exhalation from water at Delft in Holland, ibid. Evaporation of Some
parts of England, p. 253. Not correspondent with that at Liverpool, ibid. Annual
evaporation from water fix times as much as from the earth, ibid. Mere falls in

rain

rain than is raifed in vapour, fuppofing the whole a fur face of water, p. 254, The
exhalation from the earth is about a fixth part of what defcends in rain, ibid. How
the rain is collected and reftored to the fources from whence it came, p„ 254, 245.
Annual fall of rain between Lancafhire and York fh ire, p. 255. Exceeds that at
Liverpool, ibid. An experiment to afcertain whether the fad of evaporation, going
on equally well in an exhauded receiver, was not an unfurmountable objection to
that theory concerning evaporation which fuppofes a chemical folution of water in
air, p. 25 Air is a chemical folvent of water, and a catife of its evaporation,
p. 257. Heat is another caufe cf the evaporation of water, ibid. Water may exifc
in air in three Hates, ibid. Remarks on thefe different Hates of water exiiling in air,
p. 257 — 2:9. The degree of cold produced by the evaporation of aether under the
receiver of an air-pump whilfi exhauding, p. 646 — 648.

'Euclid, almoH all the geometrical reafonings of mathematicians are derived from him,
P- 450.

Evelyn, Mr. his advice of rubbing the Hems of trees to increafe their growth, put in
pradice, p. 12. The defign anfwered, p, 12 — 14.

Europeans , an account of their iirH meeting with the Bouteners, at the attack of Cooch
Behar, p.467. Their great furprize at each other, p.467, 468. Boutaners, con-
quered by the Europeans, fue for peace, p, 468.

Exhalation . See Evaporation.

Expanjion of quicldilver in the tubes of Mr. De Luc’s barometer, .refilling from the
Saleve obfervations, p. 656 — 658. Experiments on the expanfion of quickfilver,
p. 659 — 681. Rate of expanfon of a column of quickfilver in the tube of a baro-
meter, p.682. Confrrudion and application of a table of equation, for the expan-
iion of quickfilver in the tubes of barometers, p. 683—686. Experiments on the
expansion of air in the manometer, p. 689—696. Thermometrical fpaces compared
with thofe of the manometer, p. 697. Experiments for determining the adual ex-
panfion of common air in the manometer, affeded by the heat of 2120, p. 698—
715. Expanfion of the glafs tube and the fcale of the thermometers, their difference,
p. 834.

Experiments, proving thaf the eggs of the queen -bee are fecundated by the males, p.
22 — 28. Eledrical experiments, p. 48 —55. 83 — 144. 388—400. Barometrical

experiments, p. 401 — 449. 315 — 569. Experiments made with an air-pump, p.

614 — 648. Experiments to obtain a rule for meafuring heights with the barometer,
p. 653—788. Experiments to determine the boiling points of thermometers, p. 81S
—833.

F»

Fair, The number of fair and froHy days in Bridol in the year 1776, p. 334.

Farr, Dr. Samuel. Extrad of his meteorological journal for the year 1776, kept at
BriftoJ, p. 353. See Meteorological 'Journal,

5 R 2 FaJUng

[ 8;6 ]

Fafting woman, an account of her, p. 1 — 11.

Flannel . A coated phial may be charged with elettrical fparks from a piece of new
flannel, fufflciently to pierce a hole through a card with its difcharge, p. 396.
New flannel rubbed againft glafs will fometimes make it ele&ric, p. 397. An ex-
periment with a piece of dry or warm flannel tied round the globe of an eleftrical
machine, 397, 398.

Fogs, contain the fame kind of eleftricity as the atmofphere, p. 50. Thick fogs con-
tain the flrongeft electricity, ibid. The whole country of Peru involved in thick
fogs during part of the year, p. 258.

Food. An account of a woman living without food or drink, p. 1. See IFoman.

Franklin , Dr. his theory of the Leyden-bottle, further illuftrated, p. ico. &c.

Freezing point , concerning adjufting it in the thermometers, p. 856, 857.

Frojiy and fair days in Briflol in the year 1776, their number, p. 354.

Fynney, Mr. Fielding Bell, his account of the cafe of Ann Davenport, p. 458. See
Davenport,

G.

Ganges , its waters held in great veneration by the Thibetians, p. 478.

Gamas, (thick fogs) the whole country of Peru involved in them during part of the
year, p. 258.

Generation . Some refemblance of the male organs of generation in drones, p. iS.

Geometer . The fubterraneous geometer’s method of finding the depths of mines in the
Hartz, p. 423, 424.

Geometers, almoft all their reafonings derived from Euclid, p. 430. Their reafonings
with refpedt to proportional magnitudes very confined, p. 450, 451. An invefliga-
tion concerning it, p. 431 — 437.

Germany , barometrical obfervation-s on the depth of feveral mines there, p. 401. See
Barometrical olfervations.

Glafs. Obfervations on fome new and Angular phenomena in excited and charged glafs ;
with experiments made in confequence thereof, further illuftrating the Franklinian
theory of the Leyden-bottle, p. 98 — 116. Smooth glafs rubbed with a rabbit’s fkin
acquires eledfricity, p. 397. Will fometimes become ele&ric when rubbed with new
flannel, ibid. Solid glafs-rods dilate much lefs than barometer tubes, p.663, 664.
A'folid glafs pendulum-rod dilates much lefs than a fteel-one, p. 698, 699.

Glafs plates in ele&rical experiments, fealing- wax the bed coating for them, p.
389, n„

Glafs tube hermetically fealed, and having fome quickfilver inclofed in its cavity,
experiments made with one, p. 33 — 55. The difference of expanfion of the glafs
tube and the fcale of thermometers, p. 834.

GUnie , Mr. James, his general mathematical laws, which regulate and extend propor-
tion univerfally \ or, a method of comparing magnitudes of any kind together, m
ail the poffible degrees of increafe and decreafe, p. 450 — 457.

Gold,

[ 877 ]

Gold, , great quantities found in the kingdom of Thibet, p. 486, 487.

Good Hope, Cape of, Mr. De la Caille’s barometrical obfervations there, p. 784.

Gottingen in the Hartz, its height above Hanover determined by barometrical obfervations,
p. 429, 444—449.

Gravities. An experiment to determine hydroftatically the fpecific gravities of air
and quickfilver, with a given temperature and preffure ; and remarks thereon, p.
^57—570.

' Great River, in the kingdom of Thibet, fome account of it, p. 481, 482. Great quan-
tities of gold found in its fands, p. 486.

Greenvoich and Paris, concerning the difference of longitude there, refulting from the
eclipfes of Jupiter’s firfl fatellites, obferved during the lad ten years ; with a compa-
rative table of the correfponding obfervations of the firtt fatellite, made in the prin-
cipal obfervatories, p. 162— 186.

Groin. An account of a hard fubdance extradled from a woman’s groin, p. 461 — 46.3.
Caufed by fwallovving a peg of wood fixteen years before, p. 462. n.

Groot Vaaders Bofch , a wood in the interior part of Africa, a curious fpecies of cuckow
there, p. 43. See Cuckovo.

Grovjtb of trees, increafed by wafhing and rubbing, p. 12 — 14.

H.

Hadley , Mr. remarks on the defedls in his method of polifhing the fpeculum for reflec-
ting telefcopes, p. 318—320. A mote perfect method of polifhing and giving a
corredt parabolic figure to the metal at the fame time, p. 327 — 335,

Hales , Dr. his advice of wafhing the flems of trees to increafe their growth, put in
pradlice, p. 12. The defign anfwered, p„ 12—14. Dr. Hale’s calculation of the
annual evaporation in England, p. 253.

Halley , Dr. his obfervations on the exhalation of water in London, p. 252.

Hanover. The heights of Gottingen, Claudhal, Oder-brucke, and Brocken, above
Hanover, determined by barometrical obfervations, p. 429. 444 — 449,

Hare s-fkin, a coated phial may be charged with eledlrical (parks from one, fumciently-
to pierce a hole through a card with its difcharge, p. 396.

Harris, Mr. an account of him and his two brothers, neither of whom could difiinguifh
colours, p. 260 — 263.

Hartz , barometrical obfervations on the depths of mines there, p. 401. See Barometrical
obfervations.

Haf ings, Mr. governor of Bengal, grants a peace to the Boutaners, p. 468 ; and enters
into a treaty of commerce with them, p. 469. Tranflation of the letter he received
from the Tayfhoo Lama, foliciting for peace, p.489 — 492.

Heat , a caufe of the evaporation of water, p. 257.

Heights of mines meafured by the barometer, p* 401 — 449* The fubterraneous geo-
meter’s method of finding thefe heights, p. 423, 424.. Precepts and tables for cal-
culating

I s73 3

-cukaing any uecefiible heights or depths from barometrical obfeivations, p. 571 —
591 . Eafieit and beft method of determining heights by the barometer, p. 685— 686.

76 2, 763^ /?. Experiments and obfervations made ia Britain, in order to obrain a
rule for meafuring heights with the barometer^ p. 655. See Barometer. Heights de-
termined by the barometer, p- 5 1 5 — 532. 539—546. 549,550. 55 ^ — 55+. 59: —
597. Rule for meafuring foch heights, p. 686, 607. 734, 735. 757,758. 762,

763, n. The rule which an Avers in middle latitudes will not in the frigid and tor-

rid zones, p. 742 — 756. Remarks on the error of the rule in the tables of corrpu.
ration, and a* method- of bringing the theory of the barometer to greater perhd ion,
P 759 — 77°- Computations of barometrical obfervations on various heights,

P- 77d—787-

Hemming , Mr. Experiments with Ids eleflrical cylinder, fome days after ufing ivon the
bails of Canton’s electrometer, p. 109 — 113.

Heny, Mr. W illiam, his expei hnents and obfervations in ele£lricity, p. 85. See Elcc-
tricity . His remarks on fome experiments and obfervations on Mr. Volta’s e’.eflrical
machine, p. 117, 11S.

Hilly an account of a volcanic hill near In vernefs, p.383. See. Volcanic Hill.

Hills, mountains, and various other places, their heights taken by barometrical obfer-
vations. See Heights.

Honey-guide, or Cuculus Indicator, a curious fpecies cf cuckow in the interior parts of
Africa, p. 43. See Cuckow.

Honey-hunters, how conduced by the honey-guide to the wild bee-hives, p. 44. See

Cuckow.

Honig-wyzer , or honey-guide, p. 43. See Cuckow.

Hovel, a defeription of one on The Mole, one of the Alps, p. 535.

Huddart, Mr. Jofeph, his account of fome perfons who could not diftinguilh colours,
p. 260. See Colours.

Hunter , Dr. and Mr. Henry Vfotfon, their account of Dr. Maty’s illnefs, and of the
appearances in the dead body, p. 60S — 613.

Hufoands, a plurality of hulbands allowed among the Thibetians, p. 477.

HuJJ'arzewJki , a curious portrait of Copernicus in his po/Teffion, p. 33, See.

I.

Jackfon , Mr. his new method of foldering the piece of brafs to the back of the little
fpeculum of a telefcope, p. 346.

Jamaica , defeription of the Jefuits’ bark-tree of that idand, p.504 — 506. Defeription
and ufe of the cabbage-bark tree of Jamaica, p. 507 — 312.

Jefuits Bark Tree of Jamaica and the Caribbees, defeription of it, p. 504 — 506. .
ignesfatui explained, p. 142.

inquiries, philofophical ; concerning them, p. 653, 654.

* Injlru -

C S79 ]

hflruments , a number of curious ones in the Bramins’ obfervatory at Benares, p* 599,
In great prefervation, though ere&ed two hundred years ago, ibid. Conftruftiom
and fituation of them, p. 599—601. Their defcription and ufe, p. 601— 604.
607.

Iwernefs, an account of a volcanic hill near there, p. 385. See Volcanic HrlL

Journal, meteorological, for the year 1776, kept at the houfe of the Royal Society,
p. 357 — 384. See Tables .

Journey , an account of one into Africa from the Cape of Good Hope, and a defcription
of a new fpecies of Cuckcw, p. 38. See African Cuckovo.

Jupiter s hrfl fatellites, eclipfes thereof obferved during the laft ten years, concerning
the difference of longitude at Paris and Greenwich, refulting therefrom ; with a com-
parative table of the correfponding obfervations of the iirft fatellite made in the prin-
cipal obfervatories, p. 162 — j 86.

K.

Kaunkuhl , in the Hartz, its depth determined by barometrical obfervations, p. 417-^
419. 436—440.

U

Lahaffa , the capital of Thibet, fome account of it, p.481, 382. Its trade, p, 482-
—487.

Lamp-black and t2r, or lamp-black and oil, preferves the parts of mafis of fhips covered
with it from injury by lightning, p. 85, 86. A curious inflance of this kind,
p. 86—89. Experiments in artificial ele&ricity with lamp-black and oil,
p. 89—91.

Lanark , computations of barometrical obfervations made on heights near there,
P- 775-

Landen , Mr. John, his new theory of the rotatory motion of bodies affeded by forces
diflurbing fuch motion, p. 266—293.

I,ava, an account of fome difcovered near Invernefs, p. 385—387.

Lead-mines in the Ramelfberg near Godar, method of working them, p. 414,

Leather , its effect in experiments with the air pump, p. 62^, &c.

Leek in Staffordfhire, the remarkable cafe of a woman there, p, 458—464.

Leyden bottle , Dr. Franklin’s theory of it further illuflrated, p. 100, &c.

Lightning , parts of mads of fhips preferved from its injury by being covered with lamp^
black and tar, or lamp-black and oil, p. 854 86. A curious inftance of this kind,,
p. 86 — 89.

Linhoufe , computations of barometrical obfervations made on heights near there,
P- 779-

Unfeed --

[ 8 So 2

Lin/eed-oil , the thick fcum from its furface a very firong negarive elciftiic, p. 97, n.

Lions, and other beads of prey, frequently feen in Africa, p. 39, 40.

Liverpool, obfcrvations on the annual evaporation there 3 and on evaporation confidercd
as a ted of the moifture or drynefs of the atmofphere, p. 2^4. See Evaporation . A
comparative view cf the rain at Liverpool during the years 1772, 1773, J774> an£^
I775>P,247 — 250, ^ comparative view of the winds there during the fame time, ibid.
A comparative view of the temperature of the air there during the fame time, ibid.

London . The annual evaporation there, p.232. Exceeds that at Liverpool, ibid.
Meteorological journal for the year 1776, kept at London, p. 357 — 384. See Tables.
Computations of barometrical obfervations made on heights in and near London,

P* 773-

Longitude. Concerning the difference of longitude at Paris and Greenwich, refulting
from the eclipfes of Jupiter’s firll fatellites, obfervcd during the lait ten years 3 with a
comparative table of the correfponding obfervations of the firll fatellite, made in the
principal obfervatories, p. 162 — 186.

Lyndon , in Rutland, extradl of a regilter of the barometer, thermometer, and rain, kept
there, for the year 1776, p. 350. State of the barometer for that year, ibid. Of the
thermometer within and without, ibid. The quantity of rain which fell, ibid. A ge-
neral account of the weather during that year, p. 351, 352.

M.

Machines . Of the degrees and quantities of winds requifite to move the heavier kinds
of wind machines, p. 493 — 303. Experiments and obfervations on Mr. Volta’s
elettrical machine, p. 116 — ti8. Experiments on his machine for exhibiting per-
petual eledlricity, p. 389 — 392. An experiment with a piece of dry and warm

flannel tied round the globe of an ele&rical machine, p. 397, 398.

Mackenzie , Dr. his account of a woman living without food or drink, p. 1. See
Woman «

Mac Leod , Janet, the fading woman in Rofs-fhire, her cafe, p. 1 — 1 1.

Magnitudes . The general mathematical laws which regulate and extend proportion
univerfally ; or, a method of comparing magnitudes of any kind together, in all the
poflible degrees of increafe and decreafe, p. 450. The reafoning of geometers
with refpeft to proportional magnitudes very confined, p. 450, 451. An inveftigation
concerning it, p. 431 — 437.

Male organs cf generation, fome refemblances of them in drones, p. 18.

Manatee , one taken alive by the fea-fide in Africa, p. 40.

Manometer. Experiments on the expanfion of air in the manometer, p. 689 — 696.
Thermometrical fpaces compared with thofe of the manometer, p. 697. Experiments
for determining the actual expanfion of common air in the manometer afle&ed by the
heat of 2 1 2®, p. 698 — 715.

7

Maraidty

Maraldi, his notion concerning the propagation of bees, p. 17, 1 8. Drones as fmall as
common bees difcovered by him, p. 20, 21,

Marjkam , Mr. his account of the ufefulnefs of walking and rubbing the items of trees,
to promote their annual increafe, p, 12. See Trees.

Mary port , in Cumberland, an account of a perfon there who could not diitinguilh
colours, p. 260 — 265.

Maferes , Francis, Efq; his method of finding the value of an infinite feries of decreafing
quantities of a certain form, when it converges too fiowly to be fummed in the com'
mon way by the mere computation and addition, or fubtradtion, of fome of its initial
terms, p. 187. See Quantities.

Maskelyne, Rev, Dr. Nevil , an account of his new inftruraent for meafuring fmall angles,
called the prifmatic micrometer, p.799. See Micrometer.

Majls of fhips, thofe parts of them which were covered with lamp-black and tar, or
lamp-black and oil, have efcaped injury by lightning, p. 85, 86. A curious in-
fiance of this kind, p. 86—89.

Mathematical articles , leading to a clear and fatisfaRory confideration of the motion
of the earth’s axis, p. 267— 288. How the joint centrifugal force of a fpheroid, or
cylinder, having a rotatory motion about any momentary a^xis, is computed, p. 289
—295.

Mathematical laves, of thofe general ones which regulate and extend proportion univer-
rally ; or a method of comparing magnitudes of any kind together in all the poffible
degrees of increafe and decreafe, p. 450 — 457.

Mathematical problem, p. 283— 288. See Problem.

Mathematicians, almoft all their geometrical reafoning is derived from Euclid, p. 430*
Their reafonings with refpeR to proportional magnitudes very confined, p. 450, 45 r.
An inveftigation concerning them, p» 451— .437.

Maty, Dr. a fhort account of his illnefs, and of the appearances in the dead body,
p. 608 — 613.

Megameter and micrometer, an account of a new one, p. 789—798.

Metals. Directions for making the beft compofition for the metals of re fie Ring telef-
copes; together with a defeription of the procefs for grinding, poliffiing, and giving
the great fpeculum the true parobolic curve, p. 296. See TeleJcopes.

Meteorological Journal for the year 1776, kept at Briftol, 333. State of the barometer
during that year, ibid. An abridged table of the winds for that year, p. 334. Quantity
of rain which fell, ibid. Fair and frofty days, ibid. Monthly account of the wea-
ther, 354 — 336. Meteorological Journal for the year 1776 kept at the houfe of the
Royal Society, p. 357— -384. See Tables.

Micrometer and megameter, an account of a new one, p. 7 S9 — 798. An account of
anew infirumentfor meafuring fmall angles, called the prifmatic. micrometer, p.799.
Difficulties in the ufe of the objeft-glafs micrometer, p. 79-9 — 801. Method of car-
Vom LXVII. 3 S redting

[ 89o ]

reeling its error, p. 801, 802. Dercription of an inftrument for this purpoie, p. 803
— 80. Remarks concerning its ufe, 809 — 812. Dr. Malkelyne the firft inventor
of it, p. 812 — 813.

Mines. Barometrical obfervations on the depth of the mines in the Hartz, p. 401. See
Barometrical okfervaticns. Concerning the air in mines, p.412—416. Method of
working the lead-mines in the Ramellberg near Goflar; p. 417. The fubterraneous
geometer’s method of finding the depths of thefc mines, p. 423, 424.

Moijhtre or drynefs of the atmofphere, evaporation confidered as a tell of it, p. 244.
See Evaporation .

The Mole, one of the Alps, an account of it, p. 333 — 539. Barometrical obfervations
to afcertain its height, p. 539 — 546. 549, 550.

Molyneux , Mr. Remarks on the defeds in his method of pclifhing the fpeculum for
jefleding telefcopes, p. 318 — 320. A more perfect method of polilhing and giving
a corred parabolic figure to the metal at the fame time, p. 327 — 333.

Mont Salens, one of the Alps, an account of it, p. 515, ». 527. Barometrical obferva-
tions to afcertain its height, p. 515—332. 552 — 554. Concerning Mr. De Luc’s

obfervations thereon, 715, 716. 729, &c. Rule deduced from thefe obfervations,
p. 655, 656. Expanfion of quickfilver in the tubes of his barometers refulting from
the obfervations, p. 656—658.

Moon, its action upon the earth’s axis confidered, p. 267 — 288.

Mortification, The treatment to Hop a mortification, p. 460 — 46 u

Motion. A new theory of the rotatory motion of bodies affeded by forces dillurbirg fuck
motion, p. 266 — 2 95..

Mountains , obfervations made in Savoy, in order to afcertain their heights by means of
the barometer; being an examination of Mr. De Luc’s rules, delivered in his Re -
eh er ekes furies Modifications de V Atmofphere, 513. Initruments ufed on this occafion,
515. Firft feries of obfervations on Mont Saleve, ibid. Method of meafuring it,
p. 516, 517. Determination of the bafe, p. 518. Determination of the angles by
the equatorial, p. 519, 520. Determination of the vertical angles, p. 521, 522.
Determination of the Tides, p. 523. Method of making the barometrical obferva-
tions, p. 524— -528. Comparifon of the firft feries, p.52.9. Comparison of the
fecond feries, p. 530. Comparifon of the third feries, p. 531. Barometrical rules a
little defedive as to the true ratio between the gravities of air and quickfilver,
p. 532. Inftruments ufed for making barometrical obfervations on the mole, p-
53h 534’ Meafurement of this mountain, p. 539, 540. Comparifon of the firft
Series of observation, p. 541. Comparison of the fecond feries, p. 542. Compan-
ion of the third feries, p. 543. Comparifon of the fourth feries, p. 544. Comparifon
of the fifth feries, p. 545. Comparifon of the fixth feries, p.546. Barometrical
fules defedive by thefe experiments, p. 547. Remark thereon, p.547, 548. Ob-
fervations on the mole by M,.de Sauffure, making a defed of Mr. De Luc’s rules,.

P- 5+9 »

[ 3

F- 549? 550. Correfponding obfervation at Geneva, tending to prove the faid defeft,
p. 551, 552. Other experiments on Mont Saleve, p. 352. Comparifon of the fir ft
feries, 553. Comparifon of the fecond feries, ibid. Comparifon cf the third
feries, p. 554. Comparifon of the fourth feries, ibid. All proving the exiftence ■ f
the defedl in Mr. de Luc’s rules, p. 554, 535. Quantity of the defcd, from the refult
of all the barometrical experiments, p. 555, 536. An experiment to determine
hydroftatically the fpecific gravities of air and quickfilver, with a given tempeiature
and prefTure, p. 357 — 561. Statical and barometrical experiments nearly
agree, p.561. A fmall difference in the equation for the expanfion of air and
quickfilver, by a change of temperature, from what Mr. De Luc’s obfervations have
given it, p. 56 2 — 569. Remarks on the foregoing inquiry, p. c6 9, 570. Precepts
and tables for calculating any acceHible heights or depths from barometrical obfer-
vations, p. 571 — 597.

Mountains of Thibet, mulk-deer common there, p. 485, 486.

Madge, Mr. John, his dire&ions for making the belt compolition for the metals of re-
flecting telefcopes; together with a defcription of the procefs for grinding, polilhing,
and giving the great fpeculum the true parobolic curve, p. 296. See Telefcopes .

Musk-deer , common in the mountains of Thibet, p. 485, 486.

Mutton , the Thibetians Angular method of preparing it, p. 473.

N.

Nairne, Captain, his remarks on the parts of mails of fliips covered with lamp-black and
tar, or lamp-black and oil, efcaping injury by lightning, p. 85, 86.

Nairne, Mr. Edward, his account of fome experiments made with an air-pump on Mr.
Smeaton’s principle; together with fome experiments with a common air-pump
p. 614. See Air-pusnp .

Newton, Sir Ifaac , the flrft propofer of polilhing the metal for refle&ing telefcopes with
pitch, p. 344. Pitch fuppofed to be the only fubftance in nature, that is perfeCllv*
calculated for that purpofe, p. 345 — 347.

North American B if on, the fame as the great bufraloe in the wilds of Africa, p. 40.

O.

ObjtEl-glafs micrometer, an error in its ufe, p.799 — >801. Method of corredling the'
error, p. 801 — 812.

Ohfervatory . An account of the Bramins obfervatory at Benares, p. 598. See Brand ns
obfervatory .

Oder Brucke , in the Hartz, its height above Claufthal determined by barometrical obfer-
vations, p. 429. 444 — 449.

Oil and lamp-black, or lamp-black and tar, preferve the parts of malls of ihips covered,
with it from injury by lightning, p. 85, 86. A curious inllance of this kind,

5 S 2 p. 86—

[ 892 3

p. 86—89, Experiments in artificial electricity with lamp-black and oil, p. 89 — 91
The thick fcum from the furfacc of Linfeed-oil, a very flrong negative electric,
p. 97. «.

Oi .'•colours, ele&rical experiments on fome, p. 394, 395;.

Oil faint, over any fubftance, will defend it from a flight ele&rical fhock, p. 394^
393-

Qli<ve-oil, melted with chocolate, will reflore its electricity, p. 95,

P

Paint . Oil paint over any fubftance will defend it from a flight ele&rical fhock
P- 394> 395-

Painters. The old painters never gave that brightnefs to the eyes which the moderns
do in their portraits, p. 35. The former came nearer to nature than the latter,
ibid.

Paper , painted with different oil-colours, eleClrical experiments on it, p. 394, 393. A
coated phial may be charged with electrical fparks from a piece of paper, fuffciently
to Dierce a hole through a card with its difcharge, p. 396.

Paris and Greenwich, concerning their difference of longitudes, refulting from the
eclipfes of Jupiter’s fatellites, obferved during the lalt ten years ; w-ith a comparative
table of the correfponding observations of the firfl fatellite, made in the principal ob-
fervatories ; p. 162 — 186.

Pear-gage , defcription of Mr. Smeaton’s, p. 614 — 616. Quantity of permanent air re-
maining in the receiver of an air-pump when exhaufted as much as pofflble, can be
known only by this gage, p. 630, 637. The only means alfo of difcovering what
part of the receiver contains vapour, and what part permanent air, p. 637.

Pendulum. Computation of the lerieS which expreftes the time of the defcent of a pen-
dulum through the arch of a circle, p. 213 — 230. A pendulum-rod of folid glafs
dilates much lefs than one of fleel, p. 698, 699.

Perfins who could not diflinguifn colours; an account of three brothers, p. 260. See
Colours .

Peter's Rock, a volcanic hill near Invernefs ; an account of it, p. 38^5 — 387.

Peru , no rain ever in that kingdom, p. 257, Its atmofphere during part of the year
conftantly obfcured with vapours, and the whole country involved in thick fogs,
p. 257, 258. Computations of Mr. Bouguers barometrical obfervations in Peru,
p. 787.

Phial. A coated phial may be charged with ele&vical fparks fufficiently to pierce
a hole through a card with its difcharge, from a piece of new flannel, a hare’s fkin,
or a piece of paper, p. 396. An elettrical experiment on a phia*, the inflde coating
of which was ftutk with varnilh, p. 398, 399.

Philofopbical inquiries; concerning them, p. 398, 399.

i P ipe

[ Sp3 ]

Pine-apples, Extra& of a letter from William Ballard, Efq; on the culture ©f pine-apple^
p. 649. Method of raifing pine-apples in water, p. 649 — 652.

Pitchy Sir Ifaac Newton the firft propofer of policing the metal for refle&ing telefcopes
with it, p. 344. Suppofed to be the only fubftance in nature that is perfectly calcu-
lated for that purpofe, p. 345—347.

Pliny, his opinion concerning the propagation of bees, p. 16.

Pocket electrometer, defcription of one, p. 599, 400.

Pole . The furface of the earth at the pole for ever covered with fnovv, p. 764. n,

Pole cat, (Viverra Futorius) a fpecies of it found in Africa, p. 40.

Politics and religion of the Thibetians, p. 473 — 479.

Portrait of Copernicus, prefented to the Royal Society by Dr. Wolf ; an account of it?
p. 33. See Copernicus . A portrait of him in the great church at Thorn, p. 34.

Portraits . See Painters .

Precepts and tables for calculating any acceflible heights or depths from barometrical ob-
fervations, p. 571 — -^9 7 .

Pri/matic micrometer ; an account of a new inftrument fo called, for meafuring fmall
angles, p. 799. See Micrometer,

Problem (mathematical). Suppofe a given fpheroid, whilft revolving uniformly about its
proper axis, with a given angular velocity, to be fuddenly urged by fome percuffive
force to turn, with fome given angular velocity, about a diameter of its equator ;
it is propofed to explain the rotatory motion of the fpheroid confequent to the irn-
pulfe fo received, 283 — 288.

Proportion, The general mathematical laws which regulate and extend proportion uni-
verfally ; or, a method of comparing magnitudes of any kind together in all the
poffible degrees of increafe and decreafe, p. 450 — 457..

Pump . See Air-pump,.

Quantities (mathematical). A method of finding the value of an infinite feries of de
creafing quantities of a certain form, when it converges too flowly to be fummed in
the common way by the mere computation and addition, or fubtra&ion of fome of
its initial terms, p. 187. Differential feries, p. 187—190. Of the convergency of
the foregoing differential feries^ p. 190 — 19 1. Of the inveiligation of the foregoing
differential feries, p. 191 — 194, Examples of the ufefuinefs of the foregoing diffe-
rential feries in finding the values of infinite feriefes whole terms decreafe very
flowly, p 194. Computations of the lengths of circular arcs by means of infinite
ferieffes derived from their tangents, p. 194 — 199. Computation of an arch of 30
degrees, p. 199 — 203. Computation of an arch of 45 degrees, p. 203 — 215. Com-
putation of the feries which expreffes the time of the defcent of a pendulum through
the arch of a circle, p. 215 — 230.

[ *94 ]

^uetn-iees produced from the common eggs, p. 28 — 30. The working-bees have the
power of making a queen of any worm in the hive, p. 50, 31. The received opinion
that the queen-bees are produced from a particular kind of eggs, erroneous,
p. 31.

Qnickfil<ver. An experiment to determine hydroftatically the fpecific gravities of air
and quickfiiver, with a given temperature and preflure, and remarks thereon,
p. 557 — 570. Expanfion of quickfiiver in the tubes of Mr. De Lucs barometer, rc-
fulting from the Saleve obfervations, p.656 — 658. Experiments on the expanfon
of quickfiiver, p.659 — 68 r. Rate of expanfion of a column of quickfiiver in the
tube of a barometer, p. 6S2. Conftruclion and application of a table of equation,
for the expanficn of quickfiiver in the tubes of barometers, p. 683 — 686. The
equation to be applied to the obferved height of quickfiiver in the barometer,
from 15 to 31 inches; and for differences of temperature extending to 102* of Fahren-
heit; whereby the column is reduced to the height it would have ilood at in the
temperature of 32 degrees, p. 687. The expanfion of common air does not keep
pace with the dilatations of quickfiiver, p. 695.

R.

Rabbit's fkin, a coated phial may be charged with eleClrical fparks from one, fufficiently
to pierce a hole through a card with its difeharge, p. 396. Smooth glafs rubbed
with a rabbit’s fkin acquires electricity, p. 397.

Rain. Defcription of an electrometer for the rain, p. 31, 52. No rain ever in the king-
dom of Peru, p. 257. The quantity of rain falling not fo good a tell ot the ftate of the
atmofphere as evaporation, p. 244, 243. A comparative view of the rain at Liver-
pool during the years 1772, 177 3, 1774, and 1775, p. 247 — 250. Depth of the
rain not a true index of the moifiure or drynefsof the atmofphere, p. 250 — 252. Why
much rain gives no more moiilure to the atmofphere than a little, p.251. More
rain falls than is raifed in vapour, fuppofing the whole to be a furface of water, p.254.
Six times more defeends in rain than what is exhaled from the earth, ibid. How the
rain is collected and reftored to the fources from whence it came, p. 234, 233. An-
nual fall of rain between Lancafhire and Yorklhire, p. 235. Exceeds that of Liver-
pool, ibid. The quantity of rain which fell at Lyndon in Rutland during the year
1776, p. 330. What quantity fell in Briftol in the fame year, p. 354. State of the
rain for each month in London, throughout the fame year, p. 358 — 381. Quantity
which fell in each month, and in the whole year, p. 382.

Rain-gage, wrong method of fixing it, p. 253.

Rameljberg near Gollar, in the Hartz, method of working the lead-mines there, p. 414.
Depth of mines there determined by barometrical obfervations, p. 417 — 419.
436—440.

Ram/den , Mr. defcription of his portable barometer, p. 638, 659.

Rautnur ,

[ §95 3

Reaumur , on the propagation of bees, p. 1 6. 18. He difco.vered drones as fmall as
common bees, p. 21.

Recherches fur les Modifications de PAtmofpherey an examination of Mr. De Luc’s rules de-
livered therein, by obfervations made in Savoy, in order to afcertain the height of
mountains by means of the barometer, p. 513. See Mountains.

Religion and politics of the Thibetians, p. 473 — 479.

Report of the committee appointed by the Royal Society to confider of the befc method
ofadjufting the fixed points of thermometers ; and of the precautions necefiary tO'
be ufed in making experiments with thofe inftruments, p. 816. See Thermometers.

Republic of bees, the different fexes that conftitute it, p. 19, 20.

River, feme account of the great river in the kingdom of Thibet, p. 48 1, 482.

Rochon , Abbe;, the firff difeoverer of anew micrometer and megameter, p. 789 — 792..
See 812-— 8 1 5.

Rogers , Rev. Mr. his certificate of the truth of the remarkable cafe of Ann Davenport ,
p. 464.

Rome. Height of St. Peter’s church at Rome determined by the barometer, p. 582.
And of the Tarpeian rock there, p. 584.

Rofs-Jhire , an account of a woman there living without food or drink, p. 1. See
Woman .

Roy , Colonel William, his experiments and obfervations made in Britain, in order to
obtain a rule for meafuring heights with the barometer, p. 653. Firff part of the
Rule, p.686. Second part, p.734, 735. Third part, 737, 758. S ee Barometer.

Royal Obfer vat or ies at Paris and Greenwich, concerning the difference of longitude at
thefe places, refulting from the eclipfes of Jupiter’s firff fatellites, obferved during the
laff ten years ; with a comparative table of the correfponding obfervations of the firff
fatellite, made in the principal obfervatories, p. 162— 186.

Royal Society , a meteorological journal for the year 1776,' kept at their houfe, p. 337 —
384. See Tables . The report of the commitree appointed by the Royal Society to
confider of the beft method of adjufting the fixed points of thermometers $ and of the
precautions necefiary to be ufed in making experiments with diofe inffruments, p.8i6«
See Thermometers .

Rubbing and waffling the ffems of trees increafes their growth, p. 12 — 14.

Rule for meafuring heights with the barometer, 653. Firff part, 686, Second part^
73 4, 735. Third part, 757, 75.8- See Barometer. Roy .

S.

Saleve , Mont, an account of it, p. 3.13, «. 527. Barometrical obfervations to afcer-
tain its height, p. 315 — 332. 352 — 534. Concerning Mr. De Luc’s barometrical
obfervations thereon, p. 7 13, 716. 729, &c. Rule deduced from the Saleve obfer—
vations, p. 653, 656..

Satellites . Eclipfes of Jupiter’s firff fatellites, obferved during the laff ten years, con-
cerning the difference of longitude at Paris and Greenwich refulting therefrom ; with'

a com-

C 896 J

u comparative table of the correfponding obfervations of the firft fatellite made in the
principal obfervatories, p. 162 — 186.

Savoy. Obfervations made In Savoy, in order to afeertain the height of mountains by
means of the barometer, being an examination of Mr. De Luc’s rules, delivered in
his Recbercbesfur ies Modifications de l' Atmo/pbere, p. $1 3. See Mountains.

Scale of barometers, fixing them with cifterns recommended, p. 40$, 406. The fcale
and glafs tube of thermometers, their difference of expanfion, p. 834.

Sbirach, his accountofthe fex of the working bees, p. 19. 21.

Sea-anemonies , a third effay on them, p. 56. Obfervations on the generation of the fourth
fpecies of anemonies, p. 57 — 78. A further obfervation on the frit fpecies
p, 79—84.

Sealing-wax, the bed coating for glafs-plates in electrical experiments, p.389, n .

Sex of bees, difeoveries thereon, explaining the manner in which their fpecies is pro-
pa ;ated, with an account of the utility that may be derived from thofe difeoveries
by the aClual application of them to practice, p. 15. See Bees. The different fexes
that conilitute the republic of bees, p. 19, 20.

Shauls , an account of the fine wool of which they are made, p. 485. Produced from
the Thibetian fheep, ibid.

Sheep. An account of the fine wool produced from the Thibetian fheep, p. 4S5’. The
fhauls made of it, ibid.

Ships. Parts of their malls which were covered with lamp black and tar, or lamp black
and oil, have efcaped injury by lightning, p. 85, 86. A curious inftance of this
kind, p. 86 — 89.

Short, Mr. his method of furnifhing telefcopes with Metals, p. 239, 340.

Shuckburg , Sir George, his obfervations made in Savoy, in order to afeertain the height
of mountains by means of the barometer, being an examination of Mr. De Luc’s
rules, delivered in his Recherches fur les Modifications de /’ Atmofpbere, p. 515. See
Mountains .

Smeaton , Mr. an account of fome experiments made with an air-pump on his principle;
together with fome experimets with a common air pump, p. 614. S ez Air-pump.
Defcription of Mr. Smeaton’s pear-gage, p.614 — 616. Quantity of permanent air
remaining ‘in the receiver of an air-pump, when exhaufted as much as poffible, can
be known only by his gage, p. 636, 637. It is alfo the only m ans of difeovering
what part of the receiver contains vapour, and what part permanent air. p. 637.

Smith, Dr. defeats in the compofitions of metal recommended by him for the fpecula of
reflecting telefcopes, p. 297. 299. How this imperfe&ion in the metal may be pre-
vented, p. 300 — 303.

Snow, the furface of the earth at the pole covered with it, p. 764, n.

Span-man, Dr. Andreas, his account of a journey into Africa from the Cape of Good-
hope; with a defcription of a new fpecies cf cuckow, p. 38* S ee Africa
dduckoiJJ.

Speculum .

[ §97 3

Speculum « Directions for making the b.eft compofition fot the metals of reflecting tele-
fcopes ; together with a defcription of the procefs for grinding, polifhing, and giving
the great fpeculum the true parabolic carve, p. 296. See Telefcopes.

Spheroid . How the joint centrifugal force of the particles of a fpherotd or cylinder,,
having a rotatory motion about any momentary axis, is computed, p. 289—295.

Spouts . Water-fpouts occalioned by eledlricity, p.141.

St. Peter's church at Rome, its height determined by the barometer, p. 582.

Stedman , Dr. John, on the degrees and quantities of wind requifite to move the heavier
kinds of wind-machines, p. 493 — 503.

Steel. A fieel-pendulum-rod dilates much more than one of folid-glafs, p. 698, 699.

Stems of trees, the ufefulnefsof wafhing and rubbing them, to promote their annual in-
creafe, p. 12. See Trees.

Stewart, John, Efq. his account of the kingdom of Thibet, p. 465. See Thibet.

Sting, none in drones, p. 25, 26.

Strange , John, Efq. extradtof his letters ; with the Abbe Jofeph Toaldo’s letter to him,
giving an account of the tides in the Adriatic, p. 144 — 161.

Subjlance . An account of a hard fubflance extradted from a woman’s groin, p.461 —
463. Caufed by a peg of wood which Ihe had fwallovved fixteen years before,
p. 462, n.

Sun, its adtion on the motion of the earth’s axis confidered in iome mathematical arti-
cles, p/267 — 288. How the joint centrifugal force of the particles of a fpheroid or
cylinder, having a rotatory motion about any momentary axis, is computed,
p. 289—295.

Swammerdam , on the propagation of bees. p. 16. 18.

Ta

Tables*

Obfervations pn the eledlricity of the atmofphere, p. 50.

Experiments with Mr. Hemming’s eledtrical cylinder, ufor feme days after ufing it, on
the balls of Canton’s eledtrometer, p. 109— 1 13.

Eledlricity of various fubftances difeovered by a fimple electrical apparatus,
p. 122 — 126.

Concerning the tides in the Adriatic, p. 15 1. 153. dEllus medius annorum, 1751 —
175 c et 1760 — 1769. p. 155. JEitus medius ratione fitus Lunae, p. 158. Tabula
asftus maris, fecundum xn. figna zodiaci, quatenus refertur ad Lunam, p. 160.

Concerning the difference of longitude at Paris and Greenwich, refulting from the
eclipfes of Jupiter’s firft fatellites, obferved during the laft ten years 5 with a com-
parative table of the correfponding obfervations of the firft fatellite, made »in the
principal obfervatories, p. 163. 165. 167. 170 — 186.

A comparative view of the evaporation, rain, winds, and temperature of the air, dur-
ing the year 1772, at Liverpool, p. 247.

Vol. LX VII. 5T Com*

[ 89S J

Tables.

Comparative view of the fame for the year 1773, p. 248.

Comparative view of the fame for the year 1774, p. 249.

Comparative view of the fame for the year 1775, P* 25°*

State of the barometer, thermometer, with what rain fell, at Lyndon in Pvutland,
during the year 1776, p. 35'c.

State of the barometer at Briflol during the year 1776, p. 353.

An abridged table of the winds, &c. for Briitol, for the year 1776, p. 354.

Meteorological journal for the year 177 6, kept at the houfe of the Royal Society,
p. 357. State of the thermometer without and within, of the barometer, rain,
winds, and weather, for January, p. 358, 359. For February, p.360,361.
For March, p. 362,363. For April, p.364, 365. For May, p.366, 367. For
June, p. 368, 369. For July, p. 370, 371. For Augufl, p. 372, 373. For Sep-
tember, p. 374, 375. For October, p. 376, 377. For November, p. 378, 379.
For December, p. 380, 381. Greatefl, leafl, and mean height of the thermometer
without and within, and of the barometer, with the quantity of rain, in each
month throughout the year, p. 382. Variation needle, p.383. Dipping needle,
p. 384.

Barometrical obfervations determining depths and heights, p. 410 — 449.

The proportion of winds of the fecond degree and upwards, to thofe of the firft and
below, for five years, p. 502.

The proportion of fluids of the third degree and upwards, to thofe of the fecond and
below, for fiveyears, p. 503.

Barometrical obfervations to afcertain the height of mountains, p. 518 — 531.

£4° 555*

Obfervations on the expanfion of air, p. 563.

Precepts and tables for calculating any acceffible heights or depths from barometrical
obfervations, p. ^71 — 59 7*

Experiments with an air-pump, p. 628 — 635. 638. 641. 645, 646.

Rate of Expanfion of a column of quickfilver in the tube of a barometer,

p. 682.

The equation to be applied to the obferved height of quickfilver in the barometer,
from 1 ^ to 31 inches; and for differences of temperature extending to i02°of
Fahrenheit ; whereby the column is reduced to the height it would have flood
at in the temperature of 320, p. 687.

Thermometrical compared with manometrical fpaces, p. 697.

Refults of experiments on the expanfion of air, whofe mean denfity was equal to
two and a half atmofpheres, p. 700.

Refults of experiments on the expanfion of air of the denfity of five-fixths of the com-
mon atmofphere ; and of others on air that was extremely rare, being only preffed
with about one fifth of an atmofphere, p, 701.

Refult

1

t 899 ]

Tables.

Refults of experiments on the expaniion of air of the denfity of the common atmos-
phere, p. 703.

Expanfions for intermediate temperatures, p. 704.

Refults of experiments cn the expanfion of air, artificially moiilened, by the admifiion
of fteam, and fometimes water, into the bulb of the manometer, p. 705.

Heights -determined geometrically, p. 717, 78 r.

The equation depending on the temperature of the column of air, its elevation
above the fea, as denoted by the mean height of mercury in the inferior and fu-
perior barometers, p. 771.

Computations of barometrical obfervations made on heights in and near London,
P- 773-

Computations of barometrical obfervations made on heights near Tay bridge, near
Perthlhire, and of thofe near Lanark, p. 77^.

Computations of barometrical obfervations made on heights near Edinburgh, p. 777.
Computations of barometrical obfervations made on heights near Linhoufe; and of
thofe near Carnarvon in North Wales, p. 779.

Computations of part of Mr. De Luc’s barometrical obfervations, anfvvering to the
coldell and hotted: temperatures of the air, p.781 — 784.

Computations of barometrical obfervations made on heights that have not been de-
termined geometrically, p. 785.

Computations of Mr. Bouguer’s barometrical obfervations in Peru, p. 787.

For adjufting the boiling point of thermometers, p. 8^4,

For adj idling the freezing point of thermometers, p. 846.

Vails. Remarkable cow- tails produced in the kingdom of Thibet, p. 484. To what
ufe they are applied, p. 484, 485. The beak defcribed, p. 484.

Tar and lamp-black, or lamp-black and oil, have preferved the parts of mails of fhips
which were covered with it from injury by lightning, p. 85, 86. A curious in-
ftance of this kind, p. 86 — 89.

Tarpeian Rock at Rome, its height determined by the barometer, p. 584.

Tartars, heathen, who the great objed of their adoration, p. 474—476.

Tay bridge , in Perthlhire, computations of barometrical obfervations made on heights
near there, p. 775.

Tayjhoo Lama of the kingdom of Thibet, fome account of him, p. 468. 475. 479 481.

Tranflation of his letter to the governor of Bengal, foliciting a peace, p. 489 402.

Tele/copes Directions for making the bek compofition for the metals of receding tele-
fcopes ; with a defcription of the procefs for grinding, policing, and giving the
great fpeculum the true parabolic curve, p. 296. Enquiry concerning the compo-
fition for the fpecula of reflecting teiefcopes, p. 297 — 301. Hoiv to make the bell
metal for this purpofe, p. 302,503. Four tools only neceffary for grinding and
polifhing it, p. 304. Of rough grinding the fpeculum, p. 304 — 306. The manner

5 T 2 of

I! 1

of forming the brafs -grinding tool, p. 506, 307. How to form the bed of hones, or
the third too}, p. 307, 308. The manner of forming the bruifer, p. 308, 309. How
to procure walhed emery for the working of thefe tools, p. 309. Of grinding the
fpeculum, the brafs tool, and the bruifer together, p. 3C9 — 31 1. The manner of
figuring the metal upon the hones, p. 31 1 — 316. Remarks on Meflrs. Hadley and
Molyneux’s method of polifhing the fpeculum, p. 318 — 320.. Experiments which
led to a certain and eafy method of giving an exquifite polifh, and a correft para-
bolic figure to the metal at the fame time, p.321 — 327. How to polifh the fpe-
culum, p. 327—333. How to give the parabolic figure to the nuetal, p. 333 — 333.
To try the true figure of the metal, p. 338 — 341. Farther remarks on the procefs
of polifhing the fpeculum, p. 34: — 343. Teff of a good telefcope, p.343,344.
Sir Ifaac Newton firft propofed the polifhing with pitch, p. 344. Suppofed to be
the only fubllance in nature that is perfe&ly calculated for that purpofe, p. 343. 347.
Procefs for polifhing the little fpeculum, ibid. A new method of foldering the piece
of brafs to the back of the little fpeculum, p. 346. Explanation of the figures on :he
plate, p. 348, 349.

' Theory . Anew theory of the rotatory motion of bodies afTefled by forces di&urbing
fuch motion, p. 26 6.

Thermometer, flate of it at Lyndon in Rutland, during the year 1776, p. 350. State of
it without and within in London, for each month throughout the fame year,
p, 358 — 38 1 . Greateft, lead, and mean height in each month, p. 382. The report
of the committee appointed by the Royal Society to confider of the bell method of
adjufling the fixed points of thermometers ; and of the precautions neceflary to be
ufed in making experiments with thofe inflruments, p. 816. The quickfilver in the
cube and in the ball fhould be of the fame heat, and the ball not immerfed deep irr
the water, p. 818.833. Method of obtaining thefe requifites, p. 8 13. Experiments
to determine the boiling point of thermometers, p. 8 r 8 — 8-33. Cf the difference of
expanfion of the glafs tube and the fcale, p. 834. Concerning the correction necef-
lary to be made when the quickfilver in the tube is of a different heat from that in
the ball, p. 833 — 844. Rules to be obferved in adjufting the boiling point, p.845—
853. On the freezing point, p.856, 857. Precautions neceifary to be obferved in
making obfervations with thermometers, p. 857-.

Thibet, or Bout an, an account of the kingdom of, p. 465. Hardly known to Euro-
peans, ibid.. Its fituation, p. 466-. The war which led to a farther difeovery of this-
country, p. 467. The Europeans and Beutaners firft meet at the attack of Cooch-
Behar, ibid. Both greatly furprized at meeting with fuch a race of men, p. 467*
468. The Boutaners conquered by the Europeans, fue for peace, p. 468. The
governor of Bengal grants a peace* and enters into a treaty of commerce with
them, p. 468, 469, Defcription of the country, p.469 — 471. Of the inhabitants,
p. 470. 472. Their= drefs, p„ 472. Food, p. 472, 473. Their religion and pedi-

C 9or 1

tfcs? p 473—479. Some account of their buildings, p. 479. Of its capital arrdt
trade, p. 481 — 487. Tranflation of a letter from the Taylhoo Lama to the gover-
nor of Bengal, folioiting a peace, p. 489 — 492.

Them, a portrait of Copernicus in the great church there, p. 34*

friefes. An account of the tides in the Adriatic, p. 145 — 161..

9$me, the Bramins method of reckoning it, p. 606.

%>aldoi the Abbe Jofeph, his accountof the tides in the Adriatic, p. 14^—161.

Tloivnley, Mr. his obfervations on the annual fall of rain between Lancalhire and York-
Ihire, p. 255, It exceeds that at Liverpool, ibid. An error in fixing his rain-
gage, ibid.

Trees. On the uf&fulnefs of walking and rubbing the Hems of trees, to promote their
annual increafe, p. 12. Tree cleared of mofs and dirt with water and a brufh, ibid.
Walhed with a coarfe flannel, ibid. Walhings frequent in dry times, ibid. Flou-
rifhing ftate of the wafhed tree compared with others of the fame nature*
p. 12 — 14. Defcription of the Jefuits’ Bark-tree of Jamaica and the Caribbees,,
p, 304 — 506. Defcription and ufe of the Cabbage-bark tree of Jamaica*,

p. 507— 512,

v;.

Vapour t its effed in experiments with the,air*pump, p. 625,; &c. Its effed in the ex*~
panfion of quickfilver, p. 670, &c.

Vapours , the atmofphere of Peru conftantly obfeured with them during part of the year, ,
and the whole country involved in thick fogs, p.257, 258.

Vamijh. An eledrical experiment on a phial, the infide coating of which was ftuck
with varnifh, p. 398, 399.

Viverra Puioriousy a fpecies of pole-cat, found in Africa, p. 40.

Volcanic-hill t an account of one near Invernefs, p. 383. Named Creek Faterick, or<
Peter’s Rock, p. 386. Defcription of it, p. 386, 387. Evident marks of its having;
been a volcano, p. 386, and 387 n. No crater could be difeovered, p. 386, 387
Another hill near Dingwal, in this country, fuppofed to be volcanic, p. 387; .

Volta's eledrical machine, experiments and obfervations on it, with remarks, p. 116— *
1 1 8. Experiments on his plates, commonly called a machine for exhibiting per-*-
petual eledricity, p. 389 — 392.

Wo.

Wargentin , Mr. Peter, his letter concerning the difference of longitude of Paris and
Greenwich, refulting from the eclipfes of Jupiter’s firft Tatellites, obferved during the
laft ten years ; with a comparative table of the correfponding obfervations of the firft 1
fatellite, made in the principal obfervatories, p. 162 — 1 86.

Wajhing and rubbing the Items of trees increafes their growth, p. 12—14.

Water* .

[ 902 J

rJ'nter. Air an a&ive folvent of water, in proportion to its drynefs, p. 245— 25 7.
Heat, another caufe of the evaporation of water, p. 237. Water may exilt in air
in three dates, ibid. Remarks on thefe different dates of water exiting in airf
p/257 — 239. Water heavier than air, p. 560. On the exhalation of water in Lon-
don, p.252. And at Delft in Holland, ibid. Annual evaporation from water fix
times as much as it is from the earth, p. 233. The waters of the Ganges held in
great veneration by the Thibetians, p. 478. Method of railing pine apples in water,
p. 649—652.

Water-colours , elearical experiments thereon, p. 392— 394.

Water- -/pouts occafioned by elearicity, p. 141.

J-P at/on, Mr. Henry, and Dr. Hunter, their account of Dr. Maty’s illnefs, and of the
appearances in the dead body, p. 608 — 6 1 3.

Wax, great quantities loft yearly for want of bees to collea it, p. 31, 32. Rcrfons
forming fticks of wax frequently difeover elearic attraction , p. 94, tt. Sealing-wax
the beft coating for glafs-plates in elearical experiments, p. 389, «.

Weather , general ftate of it at Lyndon in Rutlandfhire during the year 1776, p. 351,
352. Monthly account of it in Briftol for the fame year, p. 354 — 356. State of the
weather in London for each month throughout the fame year, p. 358 — 381.

Weft, Thomas, efq. his account of a volcanic-hill near Invernefs, p. 383. See Volcanic -
bill .

Wild bee hives, how men are conduaed to them by the honey-guide, a curious fpecies
of cuckow, p. 43 — 45. See Cuckovs.

Winds, a comparative view of them at Liverpool, during the years 1772, 1773, 1774,
and 1775, p- 247 — 250. An abridged view of the winds at Briftol, for the year 1 776,
p. 354. State of the winds in London for each month throughout the fame year,
p. 3 ^8 — 381. Of the degrees and quantities of winds requifite to move the heavier
kinds of wind-machines, p. 493. The proportion of winds of the fecond degree and
upwards, to thofe of the firft and below, for five years, p. 502. The proportion
of winds of the third degree and upwards, to thofe of the fecond and below, for five
years, p. 503. EffeCt of winds on the barometer, p. 75: — 753.

Wind-machines . Of the degrees and quantities of winds requifite to move the heavier
kinds of wind-machines, p. 493 — 303.

Wolf, Dr. an account of the portrait of Copernicus, prefented by him to the Royal
Society, p. 33. See Copernicus .

Woman, An account of one in the fhire of Rofs, living without food or drink, p. 1.
The diforder brought on by epileptic fits, p. 2, 3. Her eye-lids loft their natural
power, ibid. Menfes difappeared, and (he monthly difeharged blood from her mouth
and nofe, ibid. Took to her bed, and rejected food, p. 3. Totally refufed food
and drink, and her jaw became faft-lccked, ibid. Loll her fpeecb, p. 4, 5. Senfible
of every thing that was faid or done, p. 5. Swallowed nothing but two draughts of

water

[ 9° 3 3

water for four years, Ibid. No evacuation by ftool, and fcarcely any by urine, for
three years, p. 3, 6. Her pulfe difiind and regular, flow and frnall, p. 6. Coun-
tenance clear and pretty frefh, and her features neither disfigured nor funk, ibid.
Her body felt like that of a healthy young woman, ibid. Her knees bent, and ham-
firings tight as a bow-firing, ibid. She fieeps much and quietly, but keeps a confiant
whimpering when awake, p. y. Her mouth foft and moift, ibid. State and con-
dition of the patient five years after the above account was taken, p. 8, A few
crumbs and a little moifiure her only fuftenance, ibid. Jaws ftili faft-locked, and
fhe never attempts to fpeak, p. 9. Her ham-firings tight as before, and eyes Ihut,
ibid. Her whole perfon rather emaciated, ibid. Still fenfible and tradable in every
thing, ibid. Great improvement in her looks and health, p. 11. Takes more food,
ibid. The account of this woman authenticated, p. 10, n.— -An account of a
hard fubfiance extraded from a woman’s groin, p. 4.61 — 463. Caufed by a peg of
wood which /he had fwallowed fixteen years before, p. 462. n.

Wood . An account of a hard fubfiance extracted from a woman’s groin, caufed by a
peg of wood which file had fwallowed fixteen years before, p. 461—463. The effed
of box- wood in experiments with the air-pump, p. 62 6, &c.

Wool . An account of the fine wool from which the fiiauls are made, p. 483. Produced
from a Thibet fiieep, ibid.

Worm-bark tree of Jamaica, its defcription and ufe, p. 507 — 512.

Wright, Dr. William , his defcription of the Jefusts’ Bark-tree of Jamaica and the Carib-
bees, p. 504 — 306. His defcription and ufe of the cabbage-bark tree of Jamaica,,
p. 507— 512.

T he End of the SIXTY - SEVENTH Volume

"The Number c/ Plates in this Volume is Twenty.

The fecond, containing two different fubje&s, is marked Tab. II. at
the Top, and Tab. III. below. The drawing of the eleventh
Plate, having been fent in too late to be numbered in the regular
feries, is marked Tab. X.

The letter-prefs tables fhould be bound in upon guards by the middle,
to avoid any folding out ; and in thofe which mufl be looked at
fide-ways, the page fhould lie towards the right-hand.

V

ERRATA,

[ 905 3

E “ R- R A T A.

Page Line' *

3S»

128,- •
W*

162 ,
165,
258,
258,
354>
47 5 >

518,

5 !9>

52°,

52J>

522i

53°>

54r>

5 45 >

546,

547 »

5 5^>
560*

562,

9. -/or commmunicate, read communicate,

15. for XL VIII, read LIV.

4. from the bottom, for -4{ and not all” read “ anf not at all" :

16 and 17* for (as the millers term it when no Iron is concerned) read (as the
millers term it) where no iron is concerned
6. for Satellites, read Satellite. -

9-

3-
2.
2.

z3-

7*

7-

4-

for ineptats, read ineptas
from the bottom, for but, read long T
from the botttom,- long* read but
for the year 1775, read the year 177 6t
for credul'iti tyfread credulity

7 T

from the bottom, for

read ■

2COO 20,000

for 233’. Sf, lf' readilf, sf. 15"

0 -0/ , rft

y > 3b >

Z. c by 4th obfervatio 112^:9°, 59', 1
2. for mountains, read mountain.-
2. for correal for the fignal 59'', 54"

5. for" 7025, 24,7025

4. fr above at C. read above at B'.

11. for correal height in fathom 686,619, read 685,619 j
8. /^ difference of Log. 654, 157, ^<2^654, 109 .

11. for (in p. 556), read (in p. 532) ,

17. for two, read too

1 . for feet, read grai ns

18. for 13348,5, read 13 558,5.

12. for barometer, read manometer *

T — S X K

568, 5. from thebottoni^r T — S X L — e-~uzzS—x> read

— b — x.

569,
57 8>
585>

586,

19.

S-

2.

the femicolon after quantity, and infert it after inftance
from the bottom/ the- attached Therm, read the two attached Therm*
ready fee p. 574 and 567

in the column for 25 inches, and againll 21 for 53,2, read 53,1
add , fee p. 568 and 569
In the 4th col. of the table at the top, for -16,10, read 15,10*

Vol. LXVIIi ^ 5 U ' _ 587,

[ 9° 6 ]

Page Line

587, in the 2d col. againft 19,90, for 12337,0, read 12377,8

20,70, for 11350,0, read 11350,8

588, 30,40, for 1236,6, read 1356,6
in the laft col .far 81,0, read 81,8.

590, 2. for uppermoft, read approximate

In plate XI. Ill col. of the table of the /f and Tides of the A* for End of the bafe 1. 2#
read End, of the bafe , 1.2.

In the fmall fcale of feet at the fide of the feftion of the mountains for 1500, read ■
15000 feet.

608, 3. for July, ran/Auguft

628, 4. from the bottom for 159, read 152

642, 13. for piftons were, read pi Hon was

658, 10. for plate XVI. read plate XV.

662, 5. for plate XVII. read plate XVL

15. after inverfe, infert ratio,

685, 5. a point after unaltered. And for but that in, read But in.

705, Tab. IVr. 9th experiment, column 132® to 152°, for 9,14350, read 9,14550
736, At the end of the note, fur Barometer, read Barometers
7 77, 1/74. December 10, weight of quickfilver to air, for 11445, re0i * I044£*

78r, 13th Station, obferved fuperior barometer, for 25,691, read 25,961
785, 3d Obfervation at Belmont Caltle, inferior equated barometer, for 29, 64. ,
read 29,664

819, 7. for were the Ihort, read were fhort

821, 5.. for 15 read 1 6. ,