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O F 

O N D O N. 

V O L. LXXV. For the Year 1785, 





^ *DAII8ia.B 




[ iii ] 


TH E Committee appointed by the Royal Society to dire^l the pub- 
lication of the Fhilofophical 'TraJifatlions, 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 Tranfdclions, that the printing of them was 
always, from time to time, the fingle aft of the refpeftive Secretaries, till 
the Forty-feveuth Volume : the Society, as a Body, never intereflingthem- 
ielves any further in their publication, than by occafionally recommending 
the revival of them to fome of their Secretaries, when, from the particular 
circumflances 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 foj- the improvement of knowledge, and benefit of: 
mankind, the great ends of their firfl: inflitution 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 advifable, that a Committee 
of their members fliould be appointed to reconfider the papers read be- 
fore them, and feleft out of them fuch, as they fhould 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 fingularity of the fub- 
3 efts, or the advantageous manner of treating them; without pretending 
to anfwer for the certainty of the fafts, or propriety of the reafonings, 
contained in the fevtral papers f© publiflied, which muft dill reii on the 
credit or judgment <:f their refpeftive authors* 

A 2 It 

E iv 1 

It ]s likewife neceiTary on this occafion to remark, that it is an efla--- 
bliflied rule of the Society, to which they will always adhere, never to 
give their opinion, as a Body, upon any rubje6t, either of Nature or Art,. 
that comes before them. And therefore the thanks, which are fre- 
quently propofed f\-om 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 refpefi iliewn to the Society 
by thofe communications. The like alfo is to be faid with regard to 
the fever al projects, inventions, and curiofities of various kinds, which 
are often exhibited to the Society ; the authors whereof, or thofe wh^ 
exhibit thera, frequently take the liberty to report, and even to certify 
in the public news-papers, that they have met with the highefl applanfe 
and approbation. And therefore it is hoped, that no regard will here-- 
after be paid to fuch reports, and public notices ; which in fome inftances? 
have beert too lightly credited, to the diflionour of the Society, 


■'"■■"* ■■• ■ '■" ' -.—-,.- . ,. ... - ■ »- — ^ ^ 


O F 

O L. LXXV. Part I. 

I* ^'^ Account of an arttficial Spring of Water. By Eraf- 

mus Darwin, M. T>. F. R, S, page i 

-IL An Account of an Englifli Bird of the Genus Motacilla, 

fuppofed to be hitherto unnoticed by Britiih Ornlthologljis ; 

obferved by the Rev. John Lightfoot, M. A. F. R. S. In a 

Letter to Sir Jofeph Banks, Bart, P. R. S. p. 8 

III, An Account of Morne Garou, a Mountain In the JJland of 
St. Vincent, with a Defcrlptlon of the Volcano on Its Summit. 
In a Letter from Mr. James Anderfon, Surgeon^ to Mr. 
Forfyth, His Majefiys Gardener at Kenlington ; commtml" 
cated by the Right Honourable Sir George Yonge, Bart. 
F.R.S. p. i6 

IV. A Supplement to the Third Fart of the Paper on the Sum- 
mation of Infinite Series, In the Philofophical Tranfa6llons 



for the Tear 1782. By the Rev, S. Vlnce, M. A; 
commu?ilcated by Nevil Mail'Celyne, D, D, F, R, S, a?id 
Aflronomer Royal, P* 32 

V. Defer iption of a Plant yielding Afa fcetida. In a Letter 

from John Hope, M. D. F. R. S. to Sir Jofeph Banks, 

Bart, P. R S, p. 36 

V!. Gifahgue of Double Stars, By William Herfchel, Efq, 
F. R. S. p. 40 

VII. Obfervations of a new Variable Star, In a Letter from 
Edward Pigott, Efq, to Sir H. C. Englefield, Bart.F. R, S, 
a?]d A. S. P« 127 

Vill. Afironomical Obfervations^ In two Letters from M. 
Francis de Zach, Profeffor of Mathematics^ and Member of 
the Royal Academies of Sciences at Marfeilles, Dijon, and 
Lyons, to Mr. Tiberius Cavallo, F. R. S. p. 137 

IX. Obfervations of a new Variable Star. By John Goodrlcke, 
Efq. ; communicated by Sir H. C. Englefield, Bart. F. R. S, 
and A. S. p. I ^"^ 

X. On the Motion of Bodies affeSicd by FriSlion, By the Rev, 
Samuel Vince, A.M. communicated by Ainhony Shepherd, 
D. D. F. R. S, Plumian Profejfor of Afrommy and experi' 
77icntal Philofophy at Q^rcihn^gQ. P* ^^5 

XL Obfervations and Experiments on the Light of Bodies in a 
State of Combuftion. By the Rev. Mr. Morgan ; communicated 
by the Rev. Richard Price, LL.D. F.R.S. p. 190 

XII. On theConjlrudiion of the Heavens, P^'WIUIam Herfchel, 
Efq. F.R.S. p. 213 

XIII. Remarks on fpecifc Gravities taken at different Degrees of 
Heat^ and an eafy Method of reducing them to a common Stan- 
J/ird. By Richard Kirwan, Efq. F.R.S. p. 267 

XI V, 



XIV. Ele5frical Experiments made in order to ajcertain the non- 
condubling Power of a perjedl Vacuum^ &c. By Mr. Wil- 
liam Morgan ; communicated by the Rev. Richard Price, 
LL.D. F.R,S, p. 272 

XV. Experiments and Ohfervations relating to Air and Water ^ 
By the Rev. Jofeph Prieftley, LL.D. F.R,S. p. 279, 

THE Prefident and Council of the Royal Society adjudged, 
for the Year 1784, the Medal on Sir Godfrey Copley's 

Donation, to Edward Waring, M. D. Lucafian Profeflbr 
pf the Mathematics at Cambridge, for his Mathematical 
Communications to the Society* 



I. An Account of an artificial Spring of IFatev, By Erafmus 

Darwin, M, D, F. R, S, 

Read November 4, 1784. 
To the Prefident and Fellows of the Royal Society. 

GENTLEMEN, Derby, July 16, 1 784. 

CONFIDENT that every atom which may contribute to 
increale the treafury of iifeful knowledge, whicli you are 
fo fuccefsfully endeavouring to accumulate, will be agreeable 
and intei^fting to the Society, I fend you an account of an 
artificial fpring of water, which. I produced laft fummer near 
the fide of the river Darwent in Derby. 

VoL.LXXV. B Near 

2 . Z)r. DAU'WiirSi'/^ccoufn of 

Near thy houfe was an old well, about one hundred yards 
from the river, and about four yards deep, which had been 
many years difufed on account of the badnefs of the water, 
w^hich I found to contain much vitriolic acid, with, at the 
fame time, a flight fulphureous fmell and tafte ; but did not 
Carefully analyfe it. The m.outh of this well was about four 
feet above the furface of the river ; an<l the ground, through 
which it was funk, confifted of a black, loofe, moiit earth, 
which appeared to have been very lately a morafs, and is now 
Covered with houfes built upon piles. At the bottom was 
found a bed of red marl, and the fpring, which was fo ftrong 
as to give up many hogfheads in a day, oozed from between 
the morafs and the marl : it lay about eight feet beneath the 
iurf ice of the river, and the water rofe within two feet of the 
top of the well. 

Having obferved that a very copious fpring, called Saint 
Alkmund's well, rofe out of the ground about half a mile 
higher on the fime fide of the Darwent, the level of which I 
knew by the height of the intervening wier to be about four or 
five feet above the ground about my w^ell ; and having obferved, 
that the higher lands, at the diftance of a mile or two behind 
thefe wells, conlified of red marl like that in the well ; I 
concluded, that, if I fhould bore through this ftratum of marl, 
i might probably gain a water fimilar to that of St. Alkmund's 
well, and hoped that at the fame time it might rife above the 
furface of my old well to the level of St. Alkmund's. 

With this intent a pump was firft put down for the 
purpofe of more eafily keeping dry the bottom of the old well, 
and a hole about two and an half inches diameter was then 
bored about thirteen yards below the bottom of the well, 
till fome l^-^nd w^as brought by the auger. A wooden pipe, 
^ which 

an artificial Spri^ig of lValct\ j 

wliicli was previoufly cut iu a conical form at one end, an 4 
armed with an iron ring at the other, was driven into the top of 
this hole, and flood np about two yards from the bottom of 
the well, and being furrounded with well-rammed clny, the 
new water afcended iu a fmall ftream through the wooden 

.Our next operation was to build a wail of clay againil: the 
moraiiy fides of t]ie well, with a wall of well-bricks inter- 
nally, up to the top of it. This completely flopped out every 
drop of the old water; and, on taking out the plug which 
had been put in the wooden pipe, the new water in two or 
three days role up to the top, and flowed over the edges of the 

Afterwards, to gratify my curiofity in feeing how high the 
new fpring would rife, and for the agreeable purpofe of pro- 
curing the water at all times quite cold and frefh, I directed 
a pipe of lead, about eight yards long, and three-quarters of 
an inch diameter, to be introduced through the wooden pipe 
defcribed above, into the flratum of marl at the bottom of the 
well, fo as to fland about three feet above the lurface of the 
ground. Near the bottom of this leaden pipe was fewed,. be- 
tween two leaden rins-S or {l^iieties,? an inverted cone of iliff 
Ipatherjriiatp.jyhich fome wool was, fluffed to ftretch it out, fo 
that, after having pafled through ttje \yopden pipe, it might 
'^completely fill .up the perforatipn of the clay. Another, leaden 
ring or flanch was foldered round the leaden pipe, about two 
yards below th;e fqrface of the ground, wdiich, with fome dou- 
bles of flannel placed under it, was nailed on the top of the 
-wooden pipe, by w^hich means the water was perfedlly pre- 
cluded froni rifing between the wooden and the leaden pipes. 

B 2 Tliis 

4 Dr, Darwin's Account of 

This being accompllfhed, the bottom of the well remained 
quite dry, and the new water quickly role about a foot above 
the top of the wdll in the leaden pipe ; and, on bending the 
mouth of this pipe to the level of the furface of the ground, 
about two hogfheads of water flowed from it in twenty- four 
hours, which liad fimilar properties with the water of St. Alk- 
mund's well, as on comparifon both thele waters curdled a 
folution' of foap in fpirit of wine, and abounded with calca- 
reous earth, which was copioufly precipitated by a folution of 
fixed alkali; but the new water was found to poffefsa greater 
abundance of It, together with numerous imall bubbles of 
rlVial acid or calcareous gas. 

The new water lias now flowed about twelve months, and, as 
far as 1 can judge, is already increaied to almoft double the quan- 
tity in a given time ; and from the rude experiments I made, I 
think it is now lefs replete with calcareous earth, approaching 
gradually to an exact correfpondence with St. Alkmund's well, 
as it probably has its origin between the lame ftrata of earth. 

As many mountains bear inconteftible marks of their having 
been forcibly railed up by fome power beneath them ; and 
other mountains, and even iflands, have been lifted up by fub- 
terraneous fires in our own times, we may fafely reafon on the 
lame fuppoiition in refpedt to all other great elevations of 
ground. Proofs of thefe circumftances are to be feen on both 
fides of this part of the country ; whoever will infpe£l, with 
the eye of a philofopher, the lime-mountain at Breedon, on 
the edge of Leicefierfhire, will not heiitate a moment in pro- 
nouncing, that it has been forcibly elevated by fome power 
beneath it ; for it is of a conical form, with the apex cut off, 


{in cirUficial Spring of Water. o 

and the ftrata, which compofe the central parts of it, and 
which are found nearly horizontal in the plain, are raifed 
almoft perpendicularly, and placed upon their edges, while 
thofe on each fide decline like the furface of the hill ; fo that 
this mountain may well be reprefented by a bur made by forc- 
ing a bodkin through feveral parallel flieets of paper. At Rou- 
ter, or Eagle-ftone, in the Peak, feveral large mafies of grit- 
ilone are ieen on the fides and bottom of the mountain, which 
by their form evince from what parts of the fummit they were 
broken off at the time it was elevated ; and the numerous loofe 
ftones fcattered about the plains in its vicinity, and half buried 
in the earth, muft have been thrown out by explofions, and 
prove the volcanic origin of the mountain. Add to this the 
vafb beds of toad-flone or lava in many parts of this county, 
fo accurately defcribed, and fo well explained, by Mr. White- 
hurst, in his Theory of the Formation of the Earth. 

Now as all great elevations of ground have been thus railed 
,by fubterraneoiis fires, and in a long courle of time their fum- 
mits have been worn away, it happens, that fome of the more 
interior ftrata of the earth are expofed naked on tiie tops of 
mountains; and that, in general, thole flrata, which lie up- 
permoft, or neareft to the fummit of the mountain, are the 
loweft in the contiguous plains. This will be readily con- 
ceived if the bur, made by thrufling a bodkin through feveral 
parallel fheets of paper, had a part of its apex cut off by a pen- 
knife, and is fo well explained by Mr. Michell, in an inge- 
nious paper on thePhasnomena of Earthquakes, publifhcd a few 
years ago in the Philofophical Tran factions. 

And as the^ more elevated parts of a country are fo much 
colder than the vallies, owing, perhaps, to a concurrence ot 


S T)r, Dar wind's Account of 

two or three caufes, but particularly to the lefs condenfed fmte 
:of the air upon hills, which thence becomes a better condu£lor 
■of hiCat, as well as of eleclricity, and permits it to efcape the 
fafler ; it is from the water condenfed on thefe cold furfaces of 
mountains, tliat our common cold Iprings have their origin ; 
and which, (liding between two of the ftrata above defcrlbed, 
•defccnd till they find or make themfelves an outlet, and will la 
confequence rife to a level with the part of the mountain where 
•they originated. And hence, if by piercing the earth you gain 
a fpring between the fecond and third, or third and fourth 
flratum, it mufl: generally happen, that the water from the 
loweft ilratum will rile the higheft, if confined in pipes, be- 
'Caufe it comes originally from a higher part of the country in 
its vicinity. 

The increafmg quantity of this new fpring, and its increafing 
purity, t fuppofe to be owing to its continually diffolving a 
part of the earth it palles through, and hence making itfelf a 
wider channel, and that through materials of lefs folubility. 
Hence it is probable, that the older and flronger fprings are 
generally the purer ; and that all fprings were originally loaded 
with the foluble impurities of the flrata, through which they 

Since the above-related experiment was made, I have read 
with pleafure the Ingenious account of the King's wells at 
Sheernefs, In the laft volume of the Tranfadions, by Sir 
Thomas Hyde Page, in which the water rofe three hundred 
feet above its fource in the well ; and have alfo been informed, 
that in the town of Richmond, in Surrey, and at Infhip near 
Preflon in Lanca(hire, it is ufual to bore for water through 
a lower ftratum of earth to a certain depth ; and that when it 


an artificial Spring of Water, j 

is found at both thofe places, it rifes lb liigli as to overflow the 
furface of the well : all thefe fads contribute to eftablifli the 
theory above-mentioned. And there is reafon to conclude, 
that if fimilar experiments were made, artificial fprings, 
rifing above ground, might ia many places be thus produced 
at fmall expence, both for the common purpofes of life, 
and for the great improvement of lands by occafionally water* 
ing them. 

E 8 ] 

J I. .In Accoimt of an Engllfli Bird of the Genus Motacllk, 
fuppofed to be hitherto unnoticed by Britifli Ornithologijis ; 
obferved by the Rev, John Llghtfoot, M. A, F. R, S. In a 
J ,etter io Sir Joieph Banks, Bart. P. R. S. 

Read November 1 8, 1784. 

SIR, Uxbridge, Nov. 20, 1783. 

AS every dilcovery in natural hiftory is efteemed worthy the 
notice of that Society which was inftitiited on purpofe to 
improve natural knowledge, I have taken the liberty to fend 
you a defcription and drawing of a bird which haunts the 
reeds of the river Coin, in the neighbourhood of Uxbridge, 
and wliich feems to have hitherto efcaped the notice of writers 
on Britifh Ornithology; and therefore fome account and de- 
fcription of it will not, I trud:, be unacceptable to the Society 
over which you lb laudably prefide. 

The neft and eggs of the bird I am about to defcribe firjd: 
attrafted my attention, and led to the difcovery of the bird 
itfelf. They were repeatedly brought by a fifherman on the 
Uxbridge river, in the parifh of Denham, to her grace the 
Duchefs Dowager of Portland, who firft communicated them 
to me. They were fuppofed by the fiflierman to belong to the 
Sedge-bird of Pennant, or MotacilU Salicaria of Li N n^eu s ; but 
being well acquainted with the nefl and eggs of this, I was very 
fure he was miftaken, though he actually produced this bird as 
the true proprietor of the fubje6ls in queftion. The flru6lure 
and pofition of the nefb having a fingular appearance, and both 


Mr» Lightfoot''s Account of a new Englifli Bird, ^ 

that and the eggs belonghig to a bird unknown to me, I became 
defirous of finding out the fccret architect, and to that end made 
life of fuch means as I thought mod likely to promote the? 

Ill a fhort time my expedations were gratified ; for on the 
26th day of July, 1783, intelligence was brought me, that 
fuch a neil: as I wanted was found. I had given pre- 
vious direction, that it fliould not be diiturbed before I had 
leen it. Upon examination, I inflantly perceived it to be of 
the fame kind and flru£lure with that under enquiry, contain- 
ing two eggs, and two young ones juft excluded from the fhell. 
One of the old birds was fitting at this time upon the neft, 
which a perfon in company attempting to feize, it flew at him 
with fo much refentment and acrimony, as to draw blood from 
the hand that dared to moleft its inflinclive operations. Both 
the parent birds continued hovering about their neft with much 
watchful care and anxiety, while I made feveral attempts to 
take them alive ; but, finding all endeavours in vain, left I 
(hould lofethe opportunity of examining them with accuracy, 
I at length, with relu£lance, caufed them to be (liot. From 
thefe fpecimens the following defcriptions were made, which, 
with an accurate drawing of one of them, together with its 
neft and egg, are humbly fubmitted to your notice. 

From the generic chara(9:ers delivered by LinnjEus, our bird 
m^ft evidently be reduced to the family of his Motacilh, for it 
has a weak, flender, fubulate bill, almofi: ftraight ; the man- 
dibles nearly equal ; the noftrils oval and naked, or not covered 
with briftles ; the tongue lacerated at the extremity ; the legs 
{lender; the toes divided to the origin, except that the exterior 
one is joined, at the under part of the lafl joint, to the middle 
toe ; the claws of nearly equal length. 

Vol. LXXV. " C The 

ID -W'' Light foot's Account of ■ 

The male and female have the fame coloured plumage, fo 
that one delciiptlon will ferve for both. They differ a little in 
fize, but their external appearance is the fame. They are both 
larger than the Pettycbaps defcribed by Willoughby j fmaller 
than the White-throaty and nearly of the fame lize with the 
JVilloW'Wren ; but to be maore particular. 

The cock-bird weighed, when jufl killed, exadly (ewtn. 
pennyweights and nine grains ; the hen fix pennyweights and 
nine grains, or one pennyweight lefs. 

The males meafured, from tip to tip of the extended wings, 
feven inches and a half; the female fix and three-quarters. 

From the end of the bill to the extremity of the tail, th& 
cock meafured five inches and a half; the hen only five 

The bill in both meafured half an inch, which is longer 
in proportion than in mofl: of this genus. The tipper mandi- 
ble is of a dark horn colour, (lightly incurved near the extre- 
mity, with a minute indenture on either fide near the point ; 
the lower is pale red or flefh- coloured, with a fhade of yellow ; 
the inlide of the mouth deep orange-coloured ; the tip of the 
tongue cloven and ciliated ; the noflrils oval, and deflitute of a 
briftly covering ; but at the bafe of the upper mandible, on 
either fide, near the angle of the mouth, arife three fhort vi- 
b7'iffce pointing downwards, black at their fummits, white at 
their bales ; a circumfl:ance common to many others of this 
genus. The iris of the eye is olive-brown ; the pupil black. 
The fhort feathers of the orbits or eye-lafhes are of a dirty 
white colour. From the corner of each eye to the noflril is a 
broad flroke or band of tawny-white feathers, lying ov^er each 
other, and running narrowefl: towards the bill ; this affords an 
excellent mark to diftinguifh the fpecies^ 


a ficw ^ngWih Bird. ji: 

♦ The feathers of the head, neck, back, coverts of tiie wings nr.d 
rump, are of an olive-brown, with a flight tinge; of green. The 
quill and tail feathers are all of a darker hue, orfimply brown ; 
their outward edges of a paler fhadc. The tall is two inches. 
long, nightly cuneated, the middle feathers being a little longer 
than the reft, the others gradually fliorter ; all of one uniforin 
(kin-brown colour edged with paler brown, and a little wedge-- 
fhaped at their ends. - . ; .fj[ 

The chin is white ; the throat, breafl, belly, and parts about' 
the vent, are white with a (light fhade of buff or tawny -, 
but all thefe feathers (as in feveral others of this genus) when 
blown afunder, or clofely examined, are found to have their 
bafe or lower half black, except the fhafts, which .are' 
white throughout, .:rj 

, The ridge and under coverts of the exterior angle of the 
wing are of a yellowifh-tawny colour, as are alfo the feathxcrs 
of the thighs ; but thofe of the knees are a fhade darker, or a 
pale yellowilh brown. 

The legs arc a light olive ; the foles of the feet bright yel- 
low, with a tinge of green, which foon fades after the bird is 
dead. The inflep is covered with feven large imbricated fcalesy> 
and five fmaller on the toes, as in others of the genus. The 
toes {land three before, and one behind ; the claws are nearly 
of equal length and curvature; but the hindmofl: is thickefl 
and itrongefl. 

From the foregoing remarks it is evident, that the bird men- 
tioned is a fpecies of Moladlla, which, as I can find no fucli 
defcribed by any fyftematic writer, I fliall venture to name, 
after the Linnjean manner, 

Motacilla {arundinaced) fupra olivaceo-fufca, fubtus al'bida, 
lori? ^t Qrbitis fufco-albefcentibus, aagulo carpi fubtus 

C ^ luteo- 

12 Mr, Lightfoot's Account of 

Juteo-fulvo, Cauda fubcuneata fufea, plantis luteo- 

In regard to fynonyms, the only author I can find who can 
be fufpeded of having noticed this bird is Sepp, who, in a late 
fplendid work, in the Dutch language, Intituled, Nederl'andfche 
Vogelen ffol. chart. max,) p. i o i , has defcribed and figured a bird, 
under the name of Turdus arundinaceus minimus^ called . in Hol- 
land Karrakietje, which in many refpe£ls agrees with our bird ; 
but as the colour of the wings in that figure is made a reddifh 
brown, inflead of an olive-brown, and the tawny- white Lor a 
(a moft effential chara^lier to diflinguifh the fpecies) are not at 
all exprefled j and the eggs are made to be of a pale-blufh colour 
with dark fpots, inftead of a dirty-white with olive fpots ; I. 
cannot pronounce for certain, that the bird there intended by 
that writer is the fame which we have now defcribed; though, 
if fome allowance be made for ill- colouring, and other omif* 
iions, it may poffibly have been ddigned for the fame fpecies. 

As we have already a bird, called In Engllfli. the Willow^ 
wren ; ours, being nearly of the fame lize and fhape, as well as 
the fame genus, may, from, its haunts, not improperly be 
denominated the Reed-wren. 

It frequents the banks of the river Cola near Uxbridge, as . 
far as from Harefield-Moor down to Iver, about the. fpace of. 
five miles, and very probably moil other parts of the fame..= 
river, though not as yet obferved. 

It is alfo certainly found in the neighbourhood of Dartford 
in Kent, from:whence a nefl -and eggs were communicated by . 
the ingenious Mr,. Latham of that place, but without knoww. 
ledge of the bird to which they belonged ; fo that there: is 
little doubt but. that it . may .be found in many parts of the 



a new Engllfh Btr^, 12 

Its food Is infedls, at leaft in part, for I obferved it catching 
flies. It hops continually from fpray to fpray, or from one 
reed to another, putting itfelf into a ftooping pofture before it 
moves. 1 heard it make no other than a fingle note, not un- 
like the found of the word peep, uttered in a low plaintive 
tone ; but this might probably be only a note of diftrefs, and 
it may have, perhaps, more pleafing and melodious ones at 
other times, with which I am unacquainted. 

The neft of this bird is a moft curious flru6lure, unlike that 
of any other I am acquainted with, enough to point out the 
difference of the fpecies, if every other charader was wanting. 

It may not be amifs here to obferve, that there is fuch a' 
manifefl diverfity in the materials, locality, and formation of 
nefts, and fuch variety of colours in the eggs of many birds 
(in other refpe6ts hard to be diftinguiflied), that it is pity this 
part of Ornithology has not been more attended to. I am well 
convinced, that as many fpecies of infedis, nearly allied to each 
other in colours and fhape, and reputed to be only i;^r/V//V/, are 
frequently, from a due attention to their larvae (which are often 
extremely different), difcovered to be fpecies totally diflindt ; fo, 
amongft birds- of fimiiar genus and feather, their true differences 
may be often found by carefully obferving their nefts and eggs,, 
when other characters, are fo miimte, in the birds themfelves,. 
as .to be diftingullhed with difficulty. By experience I have 
found this to be remarkably verified in fome of the Lark kind. - 
But to return to the neff. I was going to defcribe. It is com- 
pofed externally of dry flalks of grafs, lined, for the mofl 
part, with the flowery tufts of the common reed, or Arundo 
'Dallatoria, but fometimes with fmall dead gralles, and a few 
black horfe-hairs to cover them. This neft is ufually found 


14 Mr, LiGHtFOoT's Account of 

fyfpfended or faftened on,- like a hammock, between three -or 
four fl'alks of reeds, below the panicles of -flowers, in fueh a 
manner that the ^flalks run • through the fides of the nefts' stt 
nearly equal dlftances ; or,' to fpeak more properly,^ the i^'efl^ 
Jb tied -on to the rfeeds with^^i?^(^^r^j-,'sn-dfometiiiaes {as beiftg^ 
mSfe eligible' when'' ?t -can be had) eVeil' with thread iM\di pack-'^- 
/j6rf^<3',''emiil3ting'thfe work of a fempftrefs, as was the cafe of" 
the nelt exhibited in the drawing. The bird, however, though 
generally,' does ilot always confine her building to the fupport 
df reeds; fometimes flie fixes it on to the branches of thc^ 
lVater^dock\ and, in one inftance only (that here delineated), 
it was found faftened to the trlfurcated branch of a SyrtngOt 
bufh, or Philadelphia^ growing in a garden hedge by the river ' 

She lays commt)nly four eggs'; the ground colour a dirty 
white, ftained all over with dull olive-coloured fpots, but 
chiefly at the greater end, where are generally ittn two or 
three fmall irregular black fcratchcs ; but thefe are fometimes 
fcarcely viflble. 

I muft not omit, that both "the neft and eggs which I have 

no^ defcribed, whether defigned for the fame or not, are well 

exprefled by Sepp, in the work above cited, under the article 

iJurdus Calamoxenus, or Rietvhick, p. gj.-, but as the bird there 

reprefented is evidently the Motacilla Sylvia, Lin. or common 

White-throat (which is known to make a very different nefl), I 

am inclined to believe, that the author, by miflake, placed a 

bird and nefl in the fame plate which do not belong to each 


J have reafon to think, that the bird I have been charac- 

.teriz.iiig is a bird of migration ; for the inhabitants on the iides 

2 of 

rii,i^,Tn,„> r. /./.xxi'ui) \./, 14. 

a new 'EngWih Birc^, 15 

of the Coin do not recolle£l ever to have feen it in the winter 
months ; and its food being infers, it is probable, it muft be 
obliged to fhift its quarters for a warmer climate at the ap- 
proach of a {eveti feafon ; bat this at prefent is only matter of 
conjedlure, and not certainty. 

I am, &c. 


t '6 3 

III, Aa Recount of Morne Garqu, 4i Mountain tn the IJland tf 
St. Vincent, with a JOefcription of the Volcano on its Summit, 
In a Letter from Mr, James Anderfon, Surgeon^ to Mr. 
Forfyth, His Majejlfs Gardener at Kenfington ; communis 
cated. by the Right Honourable Sir George Yonge, Bart. 
W* R. S, 

Read November i8, 1784, 

THE many ridges of mountains which interfed this ifland 
in all directions, and rife in gradations, one above the 
other, to a very great height, with the rivers tumbling from 
their lides over very high precipices, render it exceeding difficult 
to explore its interior parts. 

The moft remarkable of thefe mountains is one that termi- 
nates the N.VV. end of the ifland, and the higheft in it, and 
has always been mentioned to have had volcanic eruptions from 
it. The traditions of the oldeft inhabitants in the ifland, and 
the ravins at its bottom, feem to me to vindicate the aflertioii 
As I was determined, during my ftay in the ifland, to fee as 
much of it as I could ; and as I knew, from the altitude of 
this mountain, there was a probability of meeting with plants 
on it I could find in no other part of the ifland ; I fliould 
have attempted going up if I had heard nothing of a volcano 
being on it. But viewing the mountain at a difl:ance, the 
ftrufture of it was different from any in the ifland, or any I had 
feen in the Wefl Indies. I could perceive it divided into many 
2 different 

Mr. Anderson's Account of a Volcanic MouHiain^ 6cc, ty 

different ridges, feparated by very deep chafms, and its fum- 
mit appeared quite deflitute of any vegetable produ£lion. On 
examining leveral ravin s^ tliat run from the bottom a great way 
up the mountain, I perceived they were quite deftitute of water, 
and found pieces of pumice-ftone, charcoal, feverai earths and 
minerals, that plainly indicated there mufl: be fome very fingu- 
lar place or other on fome part of the mountain. I alfo recol- 
leded a flory told by fome very old men in the ifland, that 
they had heard the captain of a (hip fay, that between this 
ifland and St. Lucia he faw, towards nieht, flames and fmoke 
ifiliing from the top of this mountain, and next morning his 
decks were covered with afl'ies and fmali ftones. This, you 
may readily imagine^ was excitement enough to examine it, if 1 
pofiibly could ; but I was much difcouraged upon being told, 
it was impoflible to gain the fummit of it; nor could I get 
cither white men, Carribbee, or Negro, that would undertake 
to conduct me up for any reward I could offer ; nor could I get 
any information relative to it. But as difficulty to attain in- 
hances the value of the obje-fl, fo the more I was told of the 
impoflibility of going up, the more was I determined to 
attempt it. 

After I had examined the bafis of it, as far as I could for the 
fea and other mountains, to find the moft probable place to 
commence my journey, I obferved an opening of feverai large 
and dry ravins, that leemingiy ran a great way up ; but I was 
not fure if they were not interfered by fome rocks or preci- 
pices I could not get over. I came to Mr. Maloune's, about 
a milediftant from the mountain, but the nigheft houfe to it 
I could flay at all night. Here I met with a friendly recep- 
tion and great hofpitality. After communicating my inten- 
tions to him, he told me, he would give me every afliftance 
Vol. LXXV. D he 

l8 Mr. Anderson's Account of a 

he could, by fending fome trulliy negroes with me, and wiihed' 
he was able to go with me himfelf. This was a kind offer to 
ine, in my then fituation, as negroes were what I only wanted, 
having only one boy belonging to Dr. Young with me. I 
knew, if I had great difficulties in the woods, he and I both 
fhoujd be inadequate to the talk, as in a fhort time we fhould be 
ic wearied as to be unable to proceed : from what I had feen of 
the mountain, I knew I muft be tuider the neceffity of carrying- 
water with me; and from the great diftance to the top, and' 
obitrudions w^e might naturally expe6l, I fhould at leaft 
require two days to accomplifh it. 

By examining the fide of the mountain towards me with a 
good glafs, I imagined I faw two ridges 1 might get up. I per- 
ceived they were covered great part of the way with thick 
wood; yet 1 hoped, with a little cutting, I fliould be able to 
, fcramble through them. I appointed next morning to begin, 
my route by one of thefe ridges. 

February 26, 1784, I left Mr. Maloune's about fun-rife,, 
with two flout negroes and Dr. Young's boy ; each of us hav- 
ing a good cutlafs, as well to clear our way through the woods, 
as to defend us in caf6 we fhould be attacked by Carlbbees or/ 
run-away negroes. We arrived at the bottom of the mountain 
a little before {tVQU. in the morning. To get to either of the^ 
ridges, we found we had a rock to climb above forty feet 
high: it was with great difficulty we fcrambled up, affifl-?- 
ing one another in the befl manner we could ; here we found it' 
neceiihry to contra<!:l: our baggage. After getting up this rock,. 
I found myfelf in the bottom of a narrovy and -deep ravin.. 
Having afcended this ravin a little way, I faw fome cleared , 
ground on Its fides, with tobacco growing. This I conjec- 
tured: was the habitation of fome Caribbees; but I was much, 

^: . furprifed 

Volcanic Mountain in St. Vincent's. iq 

furprifed when one of the negroes I had with me told me, it 
was the habitation of a Mr. Gasco, a Frenchman. What 
could induce a ftout healthy man in the prime of life, and a 
good mechanick, with feveral negroes, to take up his refidence 
among rocks and precipices, excluded from the whole world, 
is a my fiery to me. Befides, by ev^cry torrent of rain that 
happens, he may expe6t hlmfelf and all his habitation to be 
wafhed over the rocks into the ocean. Notwithftanding his 
fingular fituation, I found him an intelligent man^ and I expe- 
rienced every hofpitality his poor cottage could afford. 

The difficulty of going through woods in the Weft Indies, 
where there are no roads or paths, is far beyond any thing an 
European can conceive. Befides tall trees and thick under- 
wood, there are hundreds of different climbing plants twifted 
together like ropes, and running in all diredions to a great ex* 
tent, and even to the tops of the higheft trees ; by pufhing on 
they cannot be broke, and many of them with difficulty cut ; 
befides a fpecies of grafs, the Schoenus Lithofpermos, with fer- 
rated leaves, that cuts and tears the hands and face terribly. 
With fuch obftruclions as thefe it was above two hours before 
we got on the ridge, where I was in hopes our paffage would 
have been eafier ; but I foon found my miftake, for I was fur- 
rounded with a thick foreft, much more difficult to get through 
than before, on account of the large piles of trees broken down 
by the hurricanes, to pafs which in many parts we were obliged 
to creep on our hands and feet to get below them, and in other 
places to climb a great height above the furface of the ground, 
to get over large trunks lying on one another, and thefe being 
frequently rotten, occafioned us to tumble headlong down to a 
great depth, among rotten wood and grafs, fo that it was with 
great difficulty I and the negroes could extricate ourfelves. By 

D 2 con- 

r^o M>"- Andersojs's Account qJ a 

^onftaiitly cutting to clear our way, I, as well as D^^y compa- 
nions, grew much tatigued, and they wilh^d much to return 
back. About four in the afcernoou \ could not prevail upon 
them to proceed farther ; if they did, tlicy could not return 
before dark, and they would not deep all night in the woods; 
but laid, if I ftayed they would return to me next morning. I 
faw it was impoffible to gain the iummit of the mountain with 
the boy only by that route : I likewife faW' the woods 
orowing; more difficult, mv w^ater alfo totally expended : 
from thefe conliderations I intended to go down to the French- 
man's, and remain there all night, and try another route with 
my boy next morning, hoping I might be fortunate enough to 
find an eaher pafiage. I arrived at Mr. Gasco's a little after 
fun-fet, being m.uch fatigued and thirfly, and never expe- 
rienced more hofpitality and kindnefs- than from this man rii 
his miferable cot ; for we ought not to judge of the value of the 
things received, but of the difpolition of t,he heart with which 
they are given. He parted with his hammock to me, and flept oil 
^ board hirnfelf. This I at firft refufed ; but he infjfted on it, 
telling me, from my hardfhips of the day I was much more 
tired than he. I took the hammock, but I found it was impoiliblc 
to clofe my eyes during the night with cold. His hut w'as 
built of rofcaux or large reeds,, between each of which a dog 
might creep through, and the top was covered with dry grafs. 
It is fituated in the bottom of a deep gully,, where the fun 
does not ihine till nine in the morning, nor after four in the: 
afternoon. It is furrounded by thick wood, /and during the 
night the whole of the mountain is covered with thick clouds, 
Irom which it frequently rains ; this makes the night air cxr 
ceedingly cold. I got ready to renew my journey next morn- 
ing, hav^iug only Dr. Younq's boy with ixie, who continued 

\ very 

Folarnic Mountain in St. Vincent's. li 

4fery faithful to me during this excurfion, being; very active and 
hardy: I do not knov/ it I could have gone through this fa- 
tigue had it not been for his affifl'ancc. 1 now determined to 
commence this day's route up the ravin, as it feemed to widen 
and apparently run a confiderable way up in the direction i 
wifhed for; and if I conld get out of it upon the other ridge, 
it would at leafl be two miles nearer than the way I had at- 
tempted yefterday, and probably, after getting out of it, I 
might find wood eafier of accefs. In this ravin I got up about 
a mile and a half, without meeting with any conhderable ob- 
flru6tion. Encouraged by getting fo fiir, although the ravin, 
was narrowing faft, with numbers of rocks and precipices to= 
climb over, w^ith vines and bullies difficult to get through, I 
was refolved to periifl in' this route, and determined by every 
poffible means to get to the objedl of my wifbes,. well knowing 
if I could not perform it this way, I might abandon it entirely,. 
After climbing over a number of difficult paffes, the ravin ter- 
minated at the bottom of a very high precipice ; how far it 
was to the fumimit I did not know, being covered toward the 
top with thick wood ; but from the bottom upwards it 
was loofe fand as for as I could fee, with ferns and tufts of 
grafs, which, as foon as I took hold of them, came out 
at the roots. The precipice being fo very flieep, with no trees 
or buffies on it to affift tnQ in getting up, I plainly faw the at- 
tempting to climb it' was at the rilk of my life: however, I 
was refolved to try it, and telling the boy to keep fome diftance 
behind me, in cafe I ffiould tumble and drive him down along 
with me, I began to afcend, holding the tufts cf grafs a-s 
lightly as poflibie, and digging holes with my cutlafs to put 
my feet in ; but I often loft my hold, and frequently Hipped 
dowu a confiderable diftance ; however, as it was nothing but- 


"22 . Mr. Anderson's Account of ti 

loofe f-aaJ, I could eafily pufli my 'cutlafs into it to the handle/ 
and by gi'^^phig it could recover myfelf again. Had I not 
taken the refolution before 1 began to afcend to diveft myfelf of 
fear, I could not poffibly have gone, for the terror of falling 
would have been the means of it every inftant. I got up to 
fome wild plantains, which I faw continued all the way to 
the place where the bufhes and trees began tto grow. I here; 
refted myfelf, and waited for the boy's getting to me, which 
he did much eafier than I, although he had the provilions and 
water, owing to the track I had made, and becaufc, being- 
much lighter, he could better trufl: himfelf to the grafs and 
ferns. After fome labour we arrived at the top of the preci- 
pice. I found myfelf on a very narrow ridge, thickly covered 
with wood, and bounded by two ravins, the bottoms of which 
I could not fee ; the defcent to them feemed to be nearly per- 
pendicular, yet all the way covered with thick wood. After re- 
frefhing ourfelves, we began our fatigue, the boy and I cutting, 
and carrying our water and provilions, alternately. When we 
had got fome way, I found Iwas on an exceeding narrow ridge, 
•in many parts not fix feet broad; on each fide a tremendous 
gulf, into one or other of which I was often in danger of fal- 
ling, fo that with great caution I was obliged to lie down on 
my belly, to fee through the bufhes how the ridge tended. Here 
I began to fmell fulphur, or rather a fmell like gunpowder. 
As I knew this fmell mufl come from the top of the mountain, 
being in the direction of the wind, 1 was in hopes we could 
not be far from it, as the fmell grew ftrongerandftronger as I 
afcended. I faw a rifing before me, and thought if I was once 
on it, if the top of the mountain was near 1 could have a view 
of it ; but having got on this rifing I could only fee a high peak 
®n the N.W. end of the mountain, andby appearance 1 thought 
^ myfelf 

Fblcan/c Alountain in St. Vincent's. 23^ 

myfelf very little nearer than when I was at the hottom. The 
woods now became very difficult to get through ; great quan- 
tities of fallen trees lying buried under long grafs and being 
rotten, when I thought myfelf walking on the ground, I was 
frequently buried a great depth among them. Being now 
about noon, and my turn to carry the baggage, and confe- 
quently my turn of reft, I was furprifed to hear a ruftling 
among the bufiies, and fomething like a human voice behind 
me. As we were now in^aplace where I had little reafon to 
fuppofe there had been a human foot before, and could not 
imagine there could be habitations of Caribbees or run- away 
negroes, iince from the barrennefs of the mountain they 
could notpoffibly find any provifions to fubfift on, I told the boy 
to ftandflill, and let us wait their coming up; for if they were 
Garibbees advancing with an intention to hurt us, there was no 
alternative but to defend ourfelves. You may imagine my fur- 
prife when I faw one of the negroes who had been with me the 
day before, with three others, which Mr. Maloune had fen t 
to my affiilance, with plenty of provifions. After rcfrefh- 
ment, with this afliftance, I renewed my labours with frefh 
fpirits, and thought I was fure of reaching the top before 
night. Having proceeded a little, I had a fair view of the 
ravin on my left, which was of prodigious depths and ran 
from near the top of the mountain to the fea ; its bottom 
feemed to be a rock of a colour nearly refembling lava, and 
appeared as if there had been vafl torrents of fulphureous mat- 
ter running in it feme time. I regretted much I knew not of 
this ravin before I commenced my excurfion, as by paffing a 
head-land in a canoe, and getting Into the ravin, I might have 
gained the fummit of the mountain, without experiencing the 
delays and difficulties I here encountered. It was now about 

24. Mr, AndeHSoj^'s Jccouni of a 

4 P.M. au'i I had no profpe6l of the mountain's top ; but itcrn 
the afcent of the ravin below, 1 knew it was a great way oit. I 
thought if I could get into the ravin before night, I could gec 
eafily up next morning. After cutting a great way througii 
wild plantains, the fun near fetting, I found myfelf almoU: 
over the verge of a precipice : by catching hold of Ibme ilirub^ 
I prevented myfelf from falling. We were now about half- 
wav down ; but all the way below us, as far as we could fee, 
was a perpendicular precipice of rock, feveral hundred feet 
high* to pafs which was impofllble. I had a view of fome part 
of the top of the mountain, which I law was yet far from me ; 
nor could I attempt any other way than the ridge I had left. 
Being now fun-fet, and the negroes very difcontented, becaufe 
they could not return that night, I found we mitft take up our 
night's refidence in the place where we were. It was a very 
tmfavourable one, there being nothing but plantains growing, 
which retaining the rain iongln their leaves, and being frequently 
agitated by the wind, were conflantly dropping, and kept the 
ground always moift. Being almoft dark, we had time to make 
us no other habitation, than placing two or three fticks againft 
an old fiump of a tree, and flightly covering them with plantain 
leaves. After getting together fome little wood to make a fire 
to keep us comfortable, it began to blow and rain violently, 
which continued ail night. We foon found our building 
afforded us no fhelter, and the wood would not burn, fo that 
we could not get any fire ; and the ground on which we were 
Situated would not allow the leafl exercife to keep us warm# 
From fuch a miferable night I experienced no mitigation for 
the fatigues of the day. I wiflied for the riling fun, to renew 
4jiy labours^ \vhich I at laft beheld with inex.prefiible joy, 


VoiciUtic Mountain In St. Vincent's- 35 

As foon as wc could fee, we returned to the ridge \vc left 
the night before, and began to work with alacrity, as we were 
rhnofl: chilled with cold. I puihed on as fall as podlble, and 
about ten o'clock found the woods began to grow thin. 1 
could not fee the top of the mountain, but had a view of fe- 
vcral ridges that joined it. F^om tlie wind flilHng, and the 
heat growing intenfe, I thought we muft then be under tlie 
cover of the fummit : I here found many new plant;;. About 
eleven A.M. I was overjoyed to have a full view of the fummit 
of the mountain, nearly a mile diftant from us, and that we 
were nearly out of the woody region. The top feemed to be 
compofed of fix or feven ditferent ridges, very much broken in 
the fides, as If they had fuffered great coavulfions of nature ; 
they were divided by amazing deep ravins, without any water 
in them. I obferved where the rklges meet the edge of a large 
excavation, as it feemed to be, on the higheft part. I imagined 
this might be the mouth of the crater, and dire.rred my courfc 
to a high peak which overlooked it. I found here a moft 
beautiful tree which compofed the latl: w^ood. After that I en- 
tered into a thick long- jrrafs, intermixed with fern, which 
branched and ran in every direction. To break it was impof- 
fible, and wdth great difficulty I could cut it ; {q that in clear- 
ing our way through this grafs, eight or ten feet high, there was 
equal difficulty as in the woods, and it feemed to continue 
very near to the top of the mountain. Being now about noon, I 
and the negroes were fo fatigued as hardly to be able to ftand ; 
our thirft very great, to allay which, as much as poffible, w^e 
chewed the leaves of the Begonia obliqua. Two of the negroes 
returned, and the others (liid they would go no farther w^ith 
me, as they mull perifh for want of water, and it would be 
impolfible to get to the bottom before night, and they muH: all 

Vol. LXXV. E die 

2 6 Mr. x'^ndersqn's Account of a 

die in the woods. The propriety of their reafoning was evi- 
dent to me ; yet I thought it hard, after the fatigues of three 
days and two nights, to be wltiiin half a mile of the top, 
and not be able to get up, and to know little more about it than I 
did at the bottom. As the negroes had not the fame motive 
for going up as I, all my reafoning was to them ineffectual ; I 
found I was obliged to return mvfelf, as I could not perfift 
alone. At half paft twelve we began to defcend the fame way 
we came. As there was now a clear path all the way to 
the bottom, we got down to Mr. Gasco's by fun fet. After 
fitting fome time here, I was hardly able to rife again, I wasfo 
tired ; and m.y feet were fo fore I could hardly ftand on them,, 
for, my ihoes being torn to pieces, I came down the whole way 
bare-footed. I continued my journey, however, to Mr. Mat- 
Loune's, where I arrived between fix and feven at night. 

March 4th, being the day I had fixed to finifli my excurfion, 
about four in the morning, I left the houfe of Mr. FraseRj 
who out of curiofity agreed to accompany me, of which I was 
very glad, as he was a fenfible young man ; and with the affift- 
ance of two negroes we purfued our journey. We found very 
little obftrudion in our way up, until we got to the place where 
I returned ; and there, for about a quarter of a mile, wc had 
conliderable difficulty to clear our way through grafs and ferns. 
After we came within a quarter of a mile from the top, we 
found ourfelves in another climate all at once, the air very cold, 
and the vegetable productions changed ; here was nothing but 
barrennefs over the whole fummit of the mountain. On the 
confines of the grafly region and the barren I found fome beau- 
tiful plants. Mofs grows here in fuch plenty, that I frequently 
funk up to my knees in it. This is the only place in the Weft 
Indies that produced any mofs that I have feen. About nooa 
1 we 

f^okanic Mountain in St. Viucent*;5. 2^ 

\Ve gaitied the top of the peak I had directed my conrfe to be- 
fore ; when, 111 an iiiAant, we were lurprifcd with one of the 
grandeft and mod: awful fcenes I had ever beheki. I .vas {truck, 
with it amazingly, as I could not have conceived fiich a very, 
large and fo finguiarly formed an excavation. It is iituated on 
the center of tlie mountain, and where the various ridces 

to • 

unite. Its diameter is fomething more than a mile, and its cir- 
cumference to appearance a perfe6l circle. Its depth from the 
»furrounding margin is above a quarter of a mile, and it nar-. 
rows a little^ but very regularly, to the bottom. Its fides are 
very Imooth, and for the moif part cov^ered with fliort mofb^ 
except towards the fouth, where there are a number of fmali 
holes and rents. This is the only place where it is poiTible to 
go down to the bottom. : it is exceedingly dangerous, owing to 
the numberlefs fmall chafms. On the weft fide is a fe£llon of 
red rock like granite, cut very fmoothj and of the fame decli- 
vity with the other parts. All the reft of the furrounding f.des 
feems to be compofed of fand, that looks to have undergone 
the adion of intenfe fire. It has a cruft quite fmooth, of 
about an inch thick, and hard almoft as rock ; after breaking 
through which, you find nothing but loofe fand. In the center 
of the bottom is a burning mountain of about a mile in cir- 
cumference, of a conic form, but quite level. On the fum^ 
mit, out of the center of the top, arifes another mount, eight 
or ten feet high, a perfed: cone ; from its apex ifllies a column 
of fmoke. It is compofed of large mafl'es of red granite-like 
rock of various fizes and fliapes, which appear to have been 
fplit into their prefent magnitudes by fome terrible convulfion 
of nature, and are piled up very regular. From moft parts of 
the mountain iffue great quantities of fmokej efpecially on the 
north fide, which appears to be burning from top to bottom, 

E 2 -an4 

23 M>'. A>)derson'3 Account of a 

nnd the heat is i"o intcnfe, that it is impofiible to go upon It. 
Going round the bafeis very dangerous, as large mafles of rock 
are conftantly fplitting with the heat, and tunibling to the bot- 
tom. At the bottom, ou the north- lide, is a very kirge rock 
fpiit in tu'o ; each of theie halves, which are ieparated to a- 
confiderable dlftance from each other, is rent in all directions, and- 
from the crevices iiilie efflorefcences of a glofly appearance, which- 
tall-e like vitriol, and nHo beautiful cryflallizatioi-s of lulphur. 
On ali'parts of the mountain are great quantities of fulphurin all 
llal'-s; alio alum, vitriol, and other minerals. From the external 
appearance of this mountain, 1 imagine it has only begun ta 
burn lately, as on feveral- parts of it I faw fmall Ihrubs ancl> 
grafs, which looked as if they liad been lately fcorched and'- 
burnt. Tiiere are ievtral holes on the fouth, from which iffues- 
fmoke, feemingly broken out lately, as the bufhes round are but' 
lately burnt. On two oppoiite iides of the burning mountain,. 
eaR and- wefl, reaching from its bale to that of the lide of the 
crater, are two lakes of water, about a ftone's throw in breadth ; appear to be deep in the middle; their bottom to be co- 
vered witlr a clay-like lubilance. The water leems pleafant to; 
the tafle, and is of a chalybeate nature. 1 fuppofe thefe lakes- 
receive great increafe, if they are not entirely fupported, by tho 
rain that tumbles down the fide of the crater. I obferved oii^ 
the north fide of the bottom traces of beds of rivers, that to 
appearance run great quantities of water at times to both thefe 
lakes. By the llones at their edges, I could perceive that either, 
ablbrption or evaporation, or perhaps both, go on fr.ft. The 
greater part of the bottom of the crater, except the mountain 
and two lakes, is very level. On the fouth part are feveral 
Ihrubs and fmall trees. There are many flones in it that feem 
to be impregnal'td with iDincrals : 1 law feveral pieces of pu- 
j mice- 

volcanic Mountain in St. Vincent's. 29 

mice-ftone. I alfo found many jftones about the llze of a man's 
fill, rough, on one fide blue, which appearance, I imagine, 
they have got from heat, and being in contadi witli fome 
ininerah Thefe ftones are fcattered over the whole mountain, 
one or two of which I have ferit you, with fome others. 

After I had got up from the bottom of the crater, I could not 
help viewing it with admiration, from its wonderful {Irudure 
and regularity. Here 1 found an excavation cut through the 
mountain and rocks to an amazing depth, and with as mucli 
regularity and proportion of its conflituent parts, as if it had 
been planned by the hand of the moft Ikilful mathematician. I 
wlfhed much to remain on the mountain all night, to examine 
its feveral ridges with more attention next day ; but 1 could not- 
prevall on my companion to f!:ay, and therefore thought it 
advifable to accompany him. 

I obferved the motion of the clouds on this m.ountain to be 
very fingular. Althongh there are feveral parts on it higher 
than the mouth of the crater, yet I faw their attra6lIon was 
always to it. After entering on its eafl: or windward fide, they 
funk a confiderable way into it ; then, n:iounting the oppofite 
fide, and whiiling round the north- weft fide, they ran along a. 
ridge, \vhich tended nearly north-eaft, and afterw-ards funk 
into a deep ravin, which divided this ridge from another on the- 
north-weft corner of the mountain, and the highefton it, lying 
in a diredllon nearly fbuth and north. They keep thecourfe of 
this ridoe to the fouth end, and. then whirl oiT weft in their, 
natural courle. 

I took my departure from the mountain with great reluctance,- 
Although I encountered many difficulties to get up, yet it 
amply rewarded me for all my toil ; but I had not time to 
examine it with- that attention I wifticd. When I got on the: 


j} 6 Mr . Anderson*s Account of a 

peak from which I hud my C\v^ vkw of k, and ffotn' which ! 
could Ice Its diffl?reut parts, I could not help reviewing it 
feveral times. After Imprinting its fl:ru(5lure on my mind, I 
rook my final adieu of it, and returned down, and got to Mr.. 
Fr ASER*s houfe about feven at night, much fatigued. 

I am forry I had no inftruments, to take the ftate of the air-^ 
'nor the exacl; dimenflons of the different parts of the moun-* 
tain; hut, I believe^ on raeafurement, they w4U be more than: 
i have mentioned. 

From the fituation of thefe iHands to one another, and to the 
continent of South Araeiica, I imagine there are fub-marine 
communications between the burning mountains or vokanoeg 
in each of them, and from them to the volcanoes on the high 
inoimtalns of America, The iflands, which are fituated next 
the continents feem to tend in the diredion of thofe moun- 
tains ; and I have obferved, that the crater in this ifland lies 
nearly in a line with Soufriere in St. Lucia and Morne Pelee in 
^Martinique, and I dare fay from Morne Pelee to a place of the 
fame kind in Donrfinique, and from it to the others ; as it is cer- 
tain there is fomething of this kind in each of thefe iflands, 
Barbadoes and Tobago excepted, which are quite out of the 
range of the refl. 

There is no doubt but eruptions or different changes in fome 
of them, although at a great diftance, may be communicated 
to and affe61: the others in various manners. It is obferved by 
the inhabitants round thefe burning mountains, that fhocks of 
earthquakes are frequent near them, and more fenfibly felt 
than in other parts of the ifland, and the fhocks always go in 
the dire^Vion of them. 

I cannot omit mentioning this great affiftance I received in 
the above excurfion from Dr. Young, Mr. Maloune, and Mr. 


Volcanic Mountain in St. Vincent's. ^i' 

Fraser ; for, without the aid of their negroes, I could not 
have poflibly gone through with it. 

References to the figure, tab. IL 

A K The fummit that overlooks the crater, from which, the. 

drawing is taken. 
AAAA. The circumference of the crater. 
BBBB. The circumference of the bottom. 

C. The burning mountain. 

D. The fmall one on its fummit. 
EE. The two lakes of water. 

F. The fe£tion of the rock on the weflfide of the crater* 

G. The large ravin. 
HHHH. Ravins of great depth; 

I, Efflorefcence on the north end of the rock, which at a. 
diftance looks like alum or nitre. The different ridges on the fummit of the moun- 
tain, as they join the crater. 

7. Woods deftroyed by the hurricane. 

8.8. The clouds going to the fouthward of the weft ridgc^. 
after pafiing north on the weft fide of the crater. 

9.9.9. Where I defcended into the bottom of the crater. 

L and 10. The fummit and bafe of the ridge on which J> 
afcended the mountain. 

[ 3^ 3 

IV. A Supplement to the Third Pari of the Paper en the Sum- 

matlon of hifinite Series, in the PJiilofophical Tranfadions 

for the Year 1782. By the Rev. S. Vince, M ^. ; 

communicated by Nevil MalkeJvne, D. D. F. R. S. and 

Aftronomer Royal, 

Read November 25, 1784. 

^"^HE reafoning in the third part of my paper on the Sum- 
^ mation of infinite Series having been midinderftood, I 
have thought it proper to offer to the Royal Society the follow- 
ing explanation. When I propofed, for example, to fum the 
feries I - * + 5 -^ hcz, fine fine^ I wanted to find fome quantity 
which, by its expanfion, would produce that feries, and that 
quantity I called its fum ; not (as I conceived mufl have been 
evident to every one) in the common acceptation of that word, 
that the more terms we take, the more nearly we fhould 
approach to that quantity, and at laft arrive nearer to it than 
by any affignable difference, for there manifeflly can be no fuch 
quantity ; but as being a quantity from which the feries mufl 
have been deduced by expanfion, which quantity I found to be 
— i + H. L. 2. If therefore in the folution of any problem, 
the conclufion, whofe value 1 want, is exprefled by the above 
feries, and which arofe from the necefhty of expanding fome 
quantity in the preceding part of the operation, furely no one 
can deny but that I may fubflitute for it - | + H. L. 2. For 
whatever quantity it was, which by its expanfion produced at 


I'M,:, Tmm V,,/ L X\Y. TaU 1/^,31. 

Mr. Vince's Supplement^ &c. 3^ 

firfl a ferles, the fame redu«5lIon which, from that feiies, pro- 
duced the feries i-*-+|— &c. mull: alfo have produced 
— I + H. L. 2. from the quantity which was expanded. This 
value of the feries I obtained in the following manner. I fup- 
pofed the feries I — 4 + ? "" ^^' ^^ ^^ divided into two parts ; 
the firft part to contain all the terms till wc come to thofc 
where the numerators and denominators become both infinitely 
great, in which cafe every term afterwards may be fuppofed to 
be equal to unity : the fecond part, therefore, would neceflarily 
be (fuppofing the firll: part to terminate at an even number of 
terms) i - i + i - i ■{■Scz.fnefme, The firft part, hy coUed- 

inp; two terms into one, becomes ^- &c. 

^ 2.34-56.7 

which feries, as it is continued till the terms become infinitely 
fmall, is equal to - i + H. L. 2. The fecond part i - i + i — 
&c.has not, taken abftra6tedly of its origin, any determinate value 
(as will be afterwards obferved), butconfidered as part of the ori- 
ginal feries it has, for that feries muft have been deduced from the 

expanfion of the binomial i +x\ , or — — ; and hence, when 

J?= I, I - I + I -&c. can in this cafe have come only from 

, which, therefore, mull: be fubftituted for it ; confe- 

quently the two parts together give — f -}- H. L. 2. 

Having thus explained the nature of the feries which I pro- 
pofed to fum, and the principle upon which the corre6lioit 
depends, I muft beg leave to acknowledge my obligations to 
my very worthy and ingenious friend George ATwooD,Efq. 
F.R.S. who firft obferved that the feries i — i + i — i + &:c. has 
no determinate value in the abftradb, as it may be produced by 

— 1 — ; — r-; — whatever be the number of units ia the denomi- 

J + I + I +&C. 

Vol. LXXV. F nator; 

34 ^'''' Vince's Supplement on the 

jiator * ; and it may alfo be added, that the fame feries arlfes- 

from —— --- ,"^ . ' , provided the number of units be g-reater in 

I -f- I -|- I -J- I -j-OtC. '■ o 

the denominator than in the numerator. The ccrre6lion will 
therefore be different in different circumftances, and will depend 
on the nature of the quantity which was at firft expanded. In 
the third part of my paper, I appHed the correction to thofe cafes 
where the original feries arofe from the expaniion of a binomial, 
where the corre6lion is in general as I tliere gave it ; but as I 
did not apply my method to any other feries, 1 confeis that it 
did not appear to me, that the correction would then be dif- 
ferent, which it neceffarily would had [ extended my reafon- 
ing to other cafes. 1 fliall therefore add one example to (hew 
the method of corredlion in other inftances, where the value 
of the correction will be found to be different, according as we 
beoin to collect at the firlf or fecond term-. Let the leiies be 
.* _ 1 4. 5 _ 6 _[_ 8^ _ ^c. fine fine^ which camie originally from 

___J ^ ; DOW if we bepin to colled at the firfl: term, the feries 

becomes ~— H — ^ — V &c. and for the fame reafon as before, the- 
1.2 4-5 

correaion, to be added, is ]. ; but — — + — - -1- &c. ~ \- of a 
» 1.24.5 

circular arc (A) of 30" to the radius — - ; hence the fum re- 
quired =±A+ 4-. ■ If we begin to colled at the fecond term the 

feries becomes 2 -" -^ &c. ; and the corredion to be 

2.4 5.7 

fubtracled is 4 ; for the fecond part of the original feries is now 
_ I 4- I _ I ^_ I _&c. which was produced by - , -; but 

* I have been fince informed by Mr, Wales, F. R. S, that a pupil of his, Mr, 
OND, made the fame obfervation, 

Summation of Injinhe Series, 


2 ?_ . ^- — &c. = I -f * A ; therefore the fum required — 

2.45-7 ' 

-V + ± A as before. In the fame manner we may apply the cor^ 
je6tion in all other cafes. Although, therefore, the feries 
I - I + I — I 4- &c. or — i + i-i + i- &c. have no determi- 
nate value in the abftrad, yet the ^ven feries will fix its value 
by pointing out the quantity from which the feries muft have 
been originally produced. 

F 2 

[ 36 J 

V. Defcription of a Plant yielding Afa foetlda. In a Letter 
jrom John Hope, M, D. F. R, S. to Sir Jofeph Banks, 
Bart, P. R. S. 

Read December 9, 1784. 

S I R, Edinburgh, Auguft 18, Ij84» 

I BEG you will do me the honour of prefenting the inclofed 
account of the Afa foetida, and the botanical defcription of 
the plant, with the drawings, to the Royal Society. 

1 have the honour of being, with much refpcd and efteem, &c^ 


A S A F OE T I D A. 

PLAKTAumbellifera, tripedalis, ere6la, ramofa, glauca^ 
flore luteo.- 
Radix perennis.. 

Folia radicalia fex, procumbentia, trilobo-ovata, multoties 
pinnatim divifa ; foliolis incifis, fubacutis, fub- 
decurrentibus ; petlolo communi fuperne piano, linea 
elevata longitudinaliter per mediunx decuprente. 

a Cauh's, 

Dr. Hope's Defcrtpiion, kc. y^ 

Caulis bipedalls, eredtus, teretiufculus, annuus, leviter ftria- 
tus, glaber, nudus praeter unam circa medium fo- 
liorum imperfedorum conjugationem ; petlolo mem- 
bran aceo, concavo. 
Rami nudi, patuli ; quorum tres inferi, alterni, fuflinentur 
fuiguli folii imperfedi petiolo membranaceo con- 
Quatuor intermedii vertlcillati funt. Supremi ex aplce 

caulis o6lo, quorum interni ere6ll. 
Omnes hi rami fummitate fuftlnent umbellam com- 
pofitam feffilem terminalem, et prasterea 3 — 6 ramulos 
externe politos, umbellas compofitas ferentes. 
Hoc modo, rami inferiores luflinent 5, raro 6 ramulos ; 
intermedii 3 vel 4; fuperiores i et 2. 
Cal. TJmbella tmiverfalis radiis 20 — 30 conflat. 

• — partialis flofculis fubfeffilibus 10 — 20. 

Vmhella compojita feffilis convexo-plana. 

. ■ pedunculata hsemifpherica. 

Involucrum univerfale nullum.. 

— partiale nullum. 

Perianthium proprium vix notablle. 
CoR. univerfalis uniformls. 

Flofculi umbellae feffilis fertiles. 

. pedunculatae plerumque abortiunt. 

propria petalis q^ulnque aequalibus, planis, ovatis : primo 
patulis, dein reflexis, apice afcendente. 
St AM. Ftlamenia 5, fubulata, corolla longiora, incurvata. An^ 

thera fubrotundae. 
PiST. Germen turbinatum, inferum* 
Sty It duo, reflexi. 
Stigmata apice incraflata* 


sS Dr, Hope's De/cnf>f!on of a 

Per. nullum : fruclus oblongus, piano- comprefTus, utrlnque 3 

lineis elevatis notatus eft. 
Sem. duo, oblonga, magna, utrinque plana, 3 lineis elevatis 

Planta odorem alliaceum diffundit. Folia, rami, pedun- 

culi, radix, truncus, fe£li fuccum fundunt ladeum, 

fapore et odore Ala,* foetid^. 

THOUGH Afa foetida has been ufed in medicine for many- 
ages, having been introduced by the Arabian phy(icians near a 
thoufand years ago ; yet there was no fatisfaftory account of 
the plant which yielded it, tillKiEMPFER publifhed his Amoeni- 
tates Exoticae about feventy years ago. 

KiEMPFER, towards the end of the lafl century, travelled 
over a great part of Afia, and was in Perfia, and upon the fpot 
where the Afa foetida is collected. He gives a full account of 
the manner of collecting it. He defcribes the plant ; and alfd 
gives a figure of it, differing in many refpe£ts from thofe which 
I now prefent to the Society *. 

Six years ago, I received from Dr. Guthrie, of St. Peterfburg, 
F. R. S. two roots of the Afa foetida, with the following card 
from Dr. Pallas, addreffed to Dr. Guthrie : 

" Dr. Pallas's compliments to Dr. Guthrie ; he fends 
" him two roots of the Ferula Afa foetida, a plant which he 

* Probably K^mpfer's Afa foetida Plant is a different fpecies from that 
defcribcd hyDr. Hope in this paper. K^mpfer was himfelf upon the mountains 
where the drug is collefted, and his fidelity in defcribing, as well as delineating, has 
not hitherto been impeached. Sanguis Draconis, and fome other gums, are 
indifferently the produce of various fpecies of plants ; and why may not Afa 
foetida be fimiU.rly circumllanced ? Jos. Banks. 

" thinks 

l-hUrj Trnnj . K,l LXXV T«bJII.;>.jit. 

rcetiaa be limiU.rly circumflanced ? Jos. Banks. 

P Lint yielding h(A fdticla. ^^ 

*' thinks never was cultivated in any European garcien, and 
'* which nobody has been fo fortunate as to raile from feed but 
*' Iiimfeif, thouph the feeds fent to the Academy from the 
** mountains of Ghilan in Perfia had been diftributed among 
•* feveral curious perfons." 

Both thefe roots were planted in the open ground, in the 
Botanic Garden at Edinburgh ; one died ; the other after fome 
time did well, and laft lummer flowered and produced feed. I 
had an accurate drawing of the plant made by Mr. Fife, wliich 
I now have the pleafure of laying before the Society. It ex- 
prefl'es very well the general habit of the plant, which was of 
a pale fea- green colour, and grew to the height of three 
feet. The ftem is deciduous, but the root is perennial. 
Every part of the plant, when wounded, poured out a rich 
milky juice, refembling in fmell and tafte Afa foetida ; and fit 
times a fmell refembling garlick, fuch as a faint impregnation 
of Afa foetida yields, was perceivable at the diftance of feveral 

In Perlia, at the proper feafon, the root is cut over once and 
again ; from the inciiions there flows a thick juice like cream, 
wliich, thickened, is the Afa foetida. 

I have only further to obferve, that as the plant grows in 
the open air, without prote(£l:ion, and even in an unfivourable 
leafon produced a good deal of feed, and as the juice feems to 
be of the fame nature with the officinal Afa foetida, there is 
fome reafon to hope, that it may become an article of cultiva- 
tion in this country of no inconfiderable importance. 

Edinburgh, Jan. 1783. 


[ 40 1 

VI. Catalogue of Double Stars, 
By William Herfchel, Efq, F, R, S. 

Read December 9, 1784. 


THE great ufe of Double Stars having been already pointed 
out in a former paper, on the Parallax of the Fixed Stars, 
and in a latter one, on the Motion of the Solar Syftem, I have 
now drawn up a fecond coUedion of 434 more, which I have 
found out fmce the firfl was delivered. 

The happy opportunity of giving all my time to the purfuit 
of aftronomy, which it has pleafed the Royal Patron of this 
Society to furniih me with, has put it in my power to make 
the prefent colledion much more perfedl than the former; 
almofl every double ftar in it having the diftance and pofition 
of its two flats meafured by proper micrometers ; and the 
obfervations have been much oftener repeated. 

The method of claffing them is in every refped the fame as 
that which has been ufed in the firfl: collection ; for which rea- 
fon I refer to the introductory remarks that have been given 
with that coUedion * for an explanation of feveral particulars 
necefTary to be previoufly known. The numbers of the flars 
are here alfo continued, fo that the firfl clafs ending there at 

♦ See PhilofophicalTranfaaions, vol. LXXII. p. 112. 


Air, Herschel's Catalogue of Double Stars, 41 

24 begins here at 25, and the fame is done with the other 

Moil: of the double ftars in my firfl: collection are among the 
number of thofe ftars which have their places determined in 
Mr. Flamsteed's extenfive catalogue ; but of this colledicn 
many are not contained in that author's work, I have therefore 
adopted a method of pointing them out, which it will be prooer 
to defcribe. 

The finder of my reflector is limited, by a proper diaphragm, 
to a natural field of two degrees of a great circle in diameter. 
The interle<51:ion of the crofs wires, in the center of it, points^ 
out one degree ; and by the eye this degree, or the diilance. 
from the center to the circumference, may be divided into I, 
I, I, -1^ ^iid f. Thus we are furnifhed with a meafure which,. 
though coarfe, is however fufficiently accurate for the purpofe,- 
here intended ; and which, if more than two degrees are 
wanted, may be repeated at pleafure. 

In fuch meafures as thefe I have given the diftance of a dou-. 
ble ftar, whofe place I wanted to point out, from the neareft 
flar in Flamsteed's Catalogue. And fince, befides the 
diftance, it is alfo required to have its pofition with regard to 
the ftarthus referred to, I have ufed the neighbouring ilars for 
the purpofe of pointing it out. 

The ufefulnefs of this method is fo extenfive, that I fhall be 
a little more particular in defcribing its application. When a 
ftar is thus pointed out, as for inftance the 32d in the firll: clafs, 
where it is faid, '* About | degree f. preceding the 44th Lyncis, 
*' in a line parallel to Q Urfas majoris and the 39th Lyncis ;" we 
are to apply one eye to the finder, and placing the 44th Lyncij 
into. the center of the field, we are to look at;^.Urfae majoris 
and the 39th Lyncis in the heavens with the other eye by the 

Vol. LXXV. G Uz 

4i Mr. Hersctjei/s Catalcguc 

lide of the hndt-r. The naked eye then wiH immediately direct 
us, by means of the two ftars juft mentioned, towards the 
place where, in the finder, the armed eye will perceive the 
double flar in queftion about | degree from the 44th Lyncis. I 
need hardly obferve, that we muft recollect the inverlion of the 
finder, as thofe who are in the habit of uling telefcopes with 
high powers, always furniihed with inverting finders, will of 
courfe look for the fmall flar in the upper part of the field, as 
in fig. I. 

At the 45th flar, in the firfl clafs, the defcription fays, 
" About 1 1 degree f. preceding ^, towards 1 Aurigae.'* This 
double flar will accordingly be found by placing ^ Aurigse firft 
into the center of the finder; then, drawing the telefcope 
towards /, which the naked eye points out, the ftar we look for 
will begin to appear in the circumference as foon as ^ is about 
I degree removed from the center, as in fig. 2. 

It will fometimes happen, that other flars are very near 
thofe which are thus pointed out, that might be miftakeii for 
them. In fuch cafes an additional precaution has been ufed by 
mentioning fome circumftance either of magnitude orfituation, 
to diilinguifh the intended flar from the reft. After all, if any 
obferver fhould be ftlU at a lofs to find thefe ftars without having 
their right afcenfion and declination, he may furnifh himfelf 
with them by means of Flamsteed's Atlas Cceleftis ; for my 
defcription will be fafficiently exadl for him to make a point in 
the maps to denote the ftar's place; then, by means of the gra- 
duated margin, he will have its J^ and declination to the time 
of the Atlas, which he may reduce to any other period by the 
ufual computations. 

Before I quit this fubje£l I muft remark, that it will be found 
on trial, that this method of pointing out a double ftar is not 


of Double Stars, 43 

only equal, but Indeed fuperlor, to having its liglit afcenfion 
and declination given : for, fince it is to be viewed with very 
high powers, not fuch as fixed inftruments are generally fur- 
niflied with, the given right afceniion and declination would be 
of no fervice. We might, indeed, find the ilar by a fixed or 
equatorial inftrument ; and, taking notice of its fituation with 
regard to other neighbouring ftars, find, and view it after- 
wards, by a more powerful telefcope ; but this will nearly 
amount to the very fame way which here is purfued, with more 
deliberate accuracy than we are apt to ufe, while we are em- 
ployed in feeking out an obje£l to look at. 

It will be required, that the obferver (hould be furnifhed 
with Flamsteed's Atlas Coeleftis, which muft have the jflars 
marked from the author's catalogue, by a number eafily added 
to every ftar with pen and ink, as I have done to mine. The 
catalogue fhould alfo be numbered by an additional column, 
after that which contains the magnitudes. I hope in fome 
future editions of the Atlas to fee this method adopted in print, 
as the advantage of it is very confiderable, both in referring to 
the catalogue for the place of a ftar laid down in the Atlas, and 
in finding a flar in the latter whofe place is given in the 

I would recommend a precaution to thofe who wifh to exa- 
mine the clofeft of my double ftars. It relates to the adjufl 
ment of the focus. Suppofing the telefcope and the obferver 
long enough out in the open air to have acquired a fettled tem- 
perature, and the night fufficiently clear for the purpofe ; let 
the focus of the inflrument be re-adjufted with the utmoft 
delicacy upon a ftar known to be fingle, of nearly the 
fame altitude, magnitude, and colour, as the ftar which is ^o 
be examined, or upon one flar above and another below the 

G 2 fame. 

44 ^^^' Hep SCH el's Catalogue 

lame. Let die phasnomcna of the adjufting ftar be welf 
attended to; as, whether it be perfedliy round and well de- 
fined, or affeded with little appendages that frequently keep 
playing about the image of the ftar, undergoing fmall alte«'a- 
tions while it paiTes through the field, at other times remain- 
ing fixed to it during the whole pafTage, Such deceptions may 
be detefted by turning or unfcrewing the obje6t-gLifs or fpecu- 
ium a little in its cell, when thofe appendages will be obferved 
to revolve the fame w^ay. Being thus acquainted with the 
jmperfeilions as well as perfedlions of the inftrument, and 
going immediately from the adjufting ftar, which for that 
reafon alio fhould be as. near as may be,, to- the double flar which, 
is to be examined, we may hope to be fuccefsful. The aftrc- 
nomical Mr. Aubert, who did me the honour to follow this 
method with y Leonis, which he did not find to be double 
when the telefcope was adjufted by y itfelf, foon perceived the 
fmall ftar after he had adjufted it upon Regulus. The inilru^ 
ment, being one of Mr. Doi.lond's bcil 3I feet achroma- 
tics, fliewed Mr^ Aubert the two flars of y Leonis in very 
clofe conjundion, or rather one partly hid behind the other- 
On comparing thefe appearances with my obfervations of that 
double ftar, w-e muft not be furprifed to find that I place them, 
at a vifible diftance from each other : for the Newtonian ref' 
fledors, on the plan of ray 7-feet one,, as I have found, will 
give a much fmaller image of the ftars than the 3^ feet achro- 
matic refradors ; wherefore the two ftars, which in refradorsr 
as it were run into each other, will in the refledor remaia 
feparate. For this reafon alfo, thofe who only ufe fuch re- 
fradors muft not be difappointed if they cannot perceive the. 
26th, 30, 31, 36, 41, 44, 46, 47, 60, 75j 82, 86, and 87th 
ftars of my firft clafs to be double, 


oj DvuhU Stars. 45 

• AW the obierviitions in the following catalogue on the rela- 
tive magnitude, colour, and pofition of the flars, are to be 
underftood as having been made with a power of 460, unlefs 
thcv are marked otherwife. This will account fo.r t!ie dif- 
fereiice which obfervers may find in. the relative magnitude ; for 
fhould they ufe only a power of about 200, many of the 
fmali ftars that are lliid to be very unequal and extremely une- 
qual, muft appear to them perhaps a degree lower in the fcale, 
and become extremely and exccliively unequal : and this will 
happen, though the quantity of light fhould be the very fame 
which the refledtor has that ferved me to fettle thefe particulars. 
I need not fay, that on other accounts, fuch as a real difference 
in the light of the telefcope, the pre fence of the moon, twi- 
lights, aurorse boreales, or other eaufes, many of the fmall 
flars may be found to be of a different comparative luflre from 
what is afligned to them In the catalogue. The fmall ftar near 
Rigel, for Inftance, appears of a beautiful pale red colour, full,, 
round, and well defined, with my 20-feet reflector j the lo-feet 
inflrument fhews it alfo very well in fine evenings ;. the ^-feet 
requires more attention, nor is the Imall flar defined, but of a 
duiky pale red colour. A good 3I feet achromatic, of a large 
aperture, when Rigel is on the meridian,, may, perhaps, alfo 
f-iew the fmall flar, although 1 have not been able to fee it 
with a very good inftrument of that fort, which fhews the 
fmall flar that accompanies the pole-flar ; but the evening was 
not very favourable. 

The meafures of the diflances were all taken with a parallel 
filk- worm's- thread micrometer, and a power of 227 only.. 
They are not, as in the former catalogue, with the diameters 
included^ hut fi"om the center of one f}:ar to the center of the 


^5 Mr. Hersciiel's Catalogue 

oth^r. I iiare adopted thefe meafures on finding that I could 
procure threads fine enough to lubtend only an angle of about 
i^' 1^1'' -i and that by this means there was no longer any 
great difficulty of judging when the flars were centrally co- 
vered by the threads. However, I do net know whether thele 
meafures, with ftars at a confiderable diftance, may not be 
liable to an additional error of perhaps one fecond, owing to 
the remaining uncertainty in judging of their cxad: central 
pofition while the meafure is taking. 

The pofitions have all been meafured (unlefs marked other- 
wife) with a power of 460, adapted to an excellent microme- 
ter, executed by Mefl'. Nairne and Blunt, according to 
the model given in the PhilofophicalTranfa6tions, vol. LXXI. 
pnge 500-. fig. IV. ; but with a great and neceflary improve- 
ment of 'making the wheel d^ d^ of that figure perform its 
whole revolution ; bv which means the two filk-worms- 
threads may be adjufted to a greater degree of exadlnefs ; for if 
they are not placed fo as perfectly to bife6l the circle, the two 
threads will not coincide exactly after having performed one 
femi-revolution, which they muft be made to do with the 
utmoft rigour. I found the abfolute neceflity of this precau- 
tion when' I came critically to examine the pofitions of the 
Georgium Sidus, as they are given in table III. Phil. Tranf. vol, 
LXXI. p. 497. The meafures were afFeiSled with a fmall and 
pretty regular error, which I was at a lofs to account for ; and 
the diftance of this ft:ar being then totally unknown, I looked 
for the caufe of the deviation at firft in a diurnal parallax of 
that heavenly body ; but foon found it owing to the incon- 
venience before-mentioned, of not being able experimentally 
to adjuft the moveable thread to that critical nicety which I 


of Double Stars. i^j 

have now introd'accdand ufed in all the angles of thetollo^ving 


Datchet nearWindfor, Nov. l, 1784. W. HERSCHEL, 


I. 25. A Ononis. Fl. 32. Sob humero in confequentia. 
Jan. 20. Double. Confiderably unequal. L. fine w. ; S. w, 

1782. inclining to pale rofe colour. The diftance or black 
divifion between the two flars with 278 is about \ diar 
meter of L. % with 460, near | diameter of L. Pofi- 
tion with 278, 52* 10' f. preceding. 
26. fti Leonis. Fl. 2. Anteriorem pedem dextrum praecedens. 

Feb. 8. A very minute double ftar. Confiderably unequal. 

1782. Both r. With 227 there is not the leaft fufpicion of 
its being double; with 460 it appears oblong, and, 
when perfedly diftin(5l, we fee | of the apparent dia- 
meter of a fmall ftar as it were emerged from behind a 
larger ftar ; with 932 they are more clear of each other,, 
but not feparated ; the focus of every power adjufled 
upon the o^^ and 6th Leonis.. November 6th, 1782, I 

* The divifion s on the moveable circular index (j) of this micrometer fhould 
be read off by means of a line drawn on a fmall plate fattened to the fide /, and 
projeftiag with a proper curvature againft the plane of the divifions towards r, fd 
as to be nearly in conta<5t; a coincidence of lines being by far the beft method of 
afcertaining the fituation of the index. A nonius of four fub -divifions may alfo 
be ufed, whereby the 60 divifions, already divided into halves upon the index- 
plate, will be had in eighths, each of which, on the conflrudion of my prefcnt 
one, will be equal to three minutes of a degree of the circle. 

7 firft 

4^ Mr, Hf'RsciiEL's Catalogue 

J. firfl fufpcifled a feparation ; and November 13th, fairly 

faw a divifion between them. April 4, 1783, with an 
improved refledor of 20 feet 3 inches focal length and 
12 inches aperture, I faw them evidently divided. Por- 
tion 20"* 54' f. following*. 

2^. Fl. 90 Leonis. Infra edu£i:ionem caudas. 

Fe^j. 9. Treble. The two nearefl: — very unequal. L. w. ; 

1782. S, rw. With 2y8, i^ diameter of L; with 4*^0, \\ 

diameter of L. Pofition with 278, 61° 9' f. preceding. 

The two farthefl: — very unequal. S. dufky r. Dif- 

tance from L. 53'^ 43^'^ Pofition '^^'^ 12' f. preceding. 

28. y Leonis. Fl 41. In coUo lucida. 

Feb. II. A beautiful double ftar. Pretty unequal. L. w. ; 

1782. S. w. inclining a little to pale red. With 227 and 278 

diftinLlly feparated ; with 460, 4 diameter of S. j with 

625, I diameter; with 932, full I diameter, or when 

* i fufpe<5t thefe ftars to recede from each other. It is, however, very 
poffible, that the opening which I obferved between them, at the latter end 
of the year 1782 and beginning of 1 783, may be owing to very favoura- 
ble weather, or to my being better acquainted with the obje£l. Could we 
increafe our power and diflin£lnefs at plcafure, we might undoubtedly fcparatc 
any .two ftars that are not abfolutely in a direft line palTing through the eye of the 
obferver, and the centers of both the ftars. This will appear when we confider 
that perhaps 59 thirds out of one fecond, which the diameter of the ftar may 
fubtend, are fpurious ; fo that a double ftar feemingly in contact, or even partly 
hiding each other in appearance, may ftillbe far enough alunder to admit of a fair 
and confiderable feparation by applying an adequate magnifying power. It would 
have been curious, if a confiderable difference in the colours could have led us to 
difcover which of the two ftars is before the other ! But the far greateft part of 
their apparent diameters being, as we have obferved, fpurious, it is probable, that 
a different coloured light of two ftars would join together, where the rays of one 
extend into thole of the other ; and io, producing a third colour by the mixture 
of it, ftill leave the queftion undecided. 


Xif T>otibli Stan, 49 

I. bed I dinmcter of S. ; with 1504, I criamcter, well- 

defined, and the difference of colours iViU vifible; with 
2i;6, not quite a diameter of S, pretty well defined, 
4A,ut exceedingly tremulous; with 2589, lefs than i 
diameter; with 3168, ftill pretty diilmd, and about 
I diameter of S ; with 4294, more than a diamtter of 
S, but attended with the utmoft difficulty of n}anaging 
the motions ; with 5489, the interval fiill fomewhat 
larger, and if the obje£l could be kept in the center of the 
field, the eye might adapt itfelf to the focus, and 
get the better of the violent aberration ; but J-he edges 
of the glafs being of a different focus, the eye is con- 
ftantly difappointed in its endeavours to define the ob- 
je6t ; with 6652, I had but a fingle glimpfe of the ftar 
^uite disfigured; however, I afcribe it chiefly to tho 
foulnefs of the glafs, which, on account of its fmall- 
nefs, is extremely difficult to be cleaned; withaio-feet 
refle£lor, 9 inches aperture, power 626, above \ dia- 
meter of S. very diffind ; with a 20-feet reflector, 
power 350, too bright an obje6t to be quite diftincly 
though I fee it very well. Pofition 5° 24'' n. following, 
A third fliar preceding. Dift. i^5i^^23'^^, pretty accurate 
for fo great a diffance. Pofition 31° o' n. preceding. A 
fourth ftar precednig the third, and fomewhat fmaller. 

29. Parvulajuxta Fl. 44^"" Leonis, 

Peb. 17. Double. About 4' following the 44LhLeonis, which 
1782. being double in the finder, this is the lead: of the two. 
Extremely unequal. L. w. S. d. With 227, 14 dia- 
meter of L. ; with 460, 2 diameters of L. Pofition 
26° -2^1' n, following. 
Vol. LXXV. H 30. Secunda 

50 Mr, Herschel's Catalogue 

I. 30. Secunda ad t Cancrl. Fl. ^y, 

March <;. Double. Pretty unequal. Both pr. With 227, 
1782. about I diameter; with 278, I diameter; with 460, 

about I diameter or lefs. Poiition 68'' 12' n. preceding. 

A beautiful minute objetfl:. 

31. Inter Fl. 41^"" et 39"" Lyncis. 

March 5. Double. Near i| degree n. preceding the4ifl:Lyn- 
1782. cis ; towards ?i Urfae majoris. A little unequal. Both 
w. With 460, I or at moft -*- diameter, Pofition 51° 
21' f. preceding. 

32. Fl. 44* Lyncis auftralior et praecedens. 

April 3. Double. About | degree f. preceding the 44th Lyn- 
1782. cis; in a line parallel to 9 Urfse majoris and the 39th 
Lyncis. Very unequal. L. r. ; S. bluifh r. With 
227, I diameter of L. or i| when beft ; with 460, i| 
diameter, or when beft, near 2 diameters of L. The 
diameters are fo fmall that the length of the time, and 
attention of looking, makes a confiderable difference in 
the eftimation of the diftance. Poiition 8° 27' f. pre- 

33. £ Librae. Fl. 51. Primam chelam Scorpii attingens. 

May 12. Treble. Without great attention, and a confiderable 
1782. power, it may be miftaken for a double ftar ; but the 
largeft of them confifts of two. Very little unequal. 
Both w. With 460, I or at moft -i diameter afunder ; 
with 932, full I diameter of L. or near | diameter of 
S. Pofition, with 278, 82° 2' n. following. For 
meafures of the third ftar fee the 20th of the fecond 

34. Fl. 55. Caftiopeiae. < Ptolemaei. In pedis extremitate. 


of Double Stars. 51 

I. Treble. The two neareft very unequal. L. w. ; S. 

June ir, colour of pale red blotting paper. With 278, | diame- 

1782. terofS. Pofition with 227, 20" 30^ n. preceding. For 

mealures of the third ftar fee the fourth in the third 


35. Fl. 38.. Serpentarii. Dextrum infra pedem. 

June I r, Double. Very unequal. L. w. ; S. d. With 460, 
1782. 1 1 diameter of L. As the fituation is too low for 460, 
I tried 227, but it only fhewed the flar wedge-formed. 
Pofition 60° 48^ n. preceding. 

36, ^Herculis. Fl. 40. In dextro latere. 

July 18, A fine double flar. Very unequal. L. w. ; S. afli- 
1782. colour. With 460, lefs than § diameter of S. ; with 
932, I full diameter of S. *. Pofition with 811, 
20^42' n. following. 
^7. (p (Fl. 1 1^.") Herculis borealior et fequens. 
July 22, Double. About j degree n. following <p ; in a line 
1782. parallel to the 35th and 42d Herculis; the mofl: fouth 
of two very fmall telefcopic ftars. Confiderably une- 
qual. Both reddifh. V/ith 227, they can but juft be 
feen as two ftars ; with 460, near i diameter ; with 
932, not lefs than i| diameter of L. Pofition 59*^48' 
f. following. 

* The interval between very unequal ftars, eftinaated in diameters, generally 
gains more by an increafe of magnifying power than the apparent diftancc of thofe 
which are nearer of a fize. Inftances of the former may be found in the firft 
clafs, the ift, 7, 29, 35, 37, 39, 53, 59, 63, 64, 72dilars; of the latter, the 
i6th, 28, 33, 45, 46, 73, Siftftars. However, this only feems to take place 
when there is a difficulty of feeing the objeft well with a low power, which being 
removed by magnifying more, the diftance is, ns it were, laid open to the view. 

H 2 38. Fl. 

52^ Mr, Herschel's Cafaloguf 

I. 38. Fl. 18'"^ Perfei pra^cedens ad boream. In capite; 
Aug. 20, Double. About | degree n. preceding the i8th; m 
i;82. a biie parallel to o- and r Perfe'ij of two ftars- that 
next to the 1 8th. A little vmequal. Both pr. With 
278, a moil: minute and beautiful objecl ; with 460, 
I diameter of either. Pofitioii with 278, ^.^ 42' rib. 

39. jG (Fl. ii*"") Caffiopeiic prgecedens ad auftrum. 

Aug. 25, Double. About I degree f. preceding /G ; in a line 
1782. parallel to 17 and a CaliiopeiLC ; the following and largeft 
of two very confiderable flars. Very unequal. L. 
pr. ; S-. r. With 278, | diameter of S; ; with 460, 
f , or when beft,. | diameter of S. Polition 50° 42' it. 

40. Fl. 25"" Caiilopeiae pr^ecedens ad boream. 

Aug. 28, Double. About f' degree n, preceding the 2£;tlir 
J 782. towards a Caliiopeias ;- the firfl: telefcopic flar in that 
diredion. Very unequal. Both r. W^ith 460, | dia- 
meter of S. ; difficult to be feen. Pofition 50° ^o' f,. 

41. Fl. ^i^Draconls boreaiior. 

Aug. 29, A very minute double ftar. About | degree n. of the- 
1782. 3ifti ii^ ^ lii^s parallel to y and ^ Draconis; the moft 
louth and preceding of two. Confiderably unequal. 
Both pr. or r. With 227, they appear only as a 
lengthened or diflorted flar ; with 460, I diameter of 
S. ; or in very fine nights f diameter of S. ; with a. 
new fpeculum and <;oo, near f diameter when beft;- 
with 9^2, f diameter. Pofition 84° 21'' n. preceding. 
Requires qyqyj flivourable circumftaace to be €tQi\ 

3 42- 

of Double Stars,- 5J 

I, 42. ^Serpentls. Fl. 13. In primo flexu colli. 
Sept. ", A beautiful double ftar. Coniiderably nneq\3al. L» 
1782. vv. ; S. greyidr. With 227, \ diameter of S. ; with 

278, not quite | diameter of S. ; with 460, near i 

diameter of S. ; with 932, near i diameter of S. ; 

with 1504, above i diameter of S, Polition 42° 48' 1^ 


43. Ad Fl. 48*'^^ Draconis. 

Sept. --, A very minute double {lar. The moH north of 
1782. three, forming an arch ; or that which is towards a 
Draconis. Confiderably unequal. Both pale pink. In 
fine nights, with 460, it has the fliape of a wedge;; 
with 932, a fine black divifion juft vifible ; in a very- 
clear dark night a divifion may be ittw with 500, and 
with 9:52, it will be about 4. diameter. Polition witl> 
500, 88° 24^ n. preceding. 

44. Fl, 4. Aquarii. Supra veftimentum manus finiflrae. 

Sept. 3, A minute double flar. Very unequal. Both pr. 
1782. With 460, almofl: in contadl, or at moft 4. diameter 
of S. Pofition 81° 30' n. preceding. A third flar of 
the fixth clafs in view, n. preceding. 

45. ^ Aurigae(FL. 11*"') pr^ecedens ad auftrum. 

Sept. 5, Double. About 1 1 degree f. preceding ^^ towards- 
1782. i Auriga y a pretty confiderable fliar in a minute tele- 
fcopic conftellation. A little unequal. Both pr. or r, 
W^ith 227, I- diameter of S. ; with 278, near 1 dia- 
meter of S. ; with 460, about f diameter, or near § 
Jiameter of S. Pofition 47° ^^. f. preceding, 

46. V (Fl. 13''") Aquarii fequens ad boream. 

Sept. 7. Treble. About 1 1 degree n. following v, m a line 
1782. pcirallel to /3 and oe, Aquarii; the middle of three that 


5?J. Mi\ HEnscEEL^ Cafa/ogug 

I. are in .the fame diredion. The two neareft very une- 

qual. L. rw. ; S. pr. With 460, about i diameter 
of L. or more. Pofition 62° 27' n. preceding. The two 
fartheft very unequal. S. pr. Diftance with 227, 
1^ 22'^ 42^^^ Pofition 35° 51' n. following. 

47. Fl. 29'"^ Capricorni prascedens ad bor-eam. 

Sept. 27, A minute double ftar. About | degree n. preceding 
1^82. the 29th, in a line parallel to y and a Capricorni. A 
little unequal. Appears diflorted with 227 and 278; 
nor will 460 (hew it feparated ; with 657, two ftars 
vifible ; 932 confirms it. Difficult to be feen diftindly 
on account of its low fituation. Pofition 84° 48' n. 
preceding. 20-feet refle(5lor, 200. Both w. 

48. Fl. 6*'" Cephei praecedens. In dextro brachio. 

Sept. 27, Avery minute and beautiful double ftar. Near | de- 

^1782. . gi'GS preceding the 6th towards 1; . Cephei ; a pretty 

fconfiderableteiefcopic ftar. A little unequal. Both pr* 

Almofl in contact with 460; with 625, better divided; 

with 657 ftill better. Pofition 14° 9'' f. preceding. 

49. X Cephei (Fl. 22^"") fequens ad boream. 

Sept. 27, Double. About i| degree n. following X, in aline 
1782. fiom ^through X Cephei continued. Extremely une- 
qual. Both dw. Cannot be feen with 278, except 
with long attention; with 460, if diameter of L. 
Pofition 85° 48' n. following; perhaps a little inac- 

c;o. X Aquarii (Fl. y^"""") prfficedens. 

Sept. 30, Double. About 2f degrees preceding, and a little 

1782. fouth of X Aquarii; a confiderable ftar. Very unequal. 

■L. w. ; S. dw. With 278, lefs than i diameter of 

L; with 460, 1 1 diameter of L. Pofition with 227, 


of Double Slavs. ^ r 

I. 41' 12' n. preceding. The meafnre inaccurate on 

account of the low power, and probably 3° or 4° too . 

51. Quas fequitur i (Fl. 32*"") Cephei. 

Sept. 30, Double. About 2I degrees n. following <, towards 
1782. y Cephei; a confiderable jftar. A little unequal. Both 
pn A pretty object with 227; with 460, i| diameter 
nearly. Pofition 3° 36' f. preceding. 

52. Parvula Fl. 25"'Orionis adjecla. 

oa. 2, Double. A few minutes n. following the 25th 
1782. Orionis, in a line parallel to h Eridani and e Orionis. 
Very unequal. L. afh w. ; S. dw. With 460, i dia- 
meter of L. Pofition 52° 48' n. preceding. . 

53. Parvula Fl. 30""^ Orionis adjeda. 

oa. 2, Double. About 10^ preceding the 30th, in a line 
1782. parallel to X and y Orionis. Very unequal. L. w. ; .: 

S. d. ; with 460., i diameter of L. Pofition 43° 24' n. , 


54. T (Fl. 20**") Orionis praecedens. In malleolo liniftri cruris, 
oa. 4, Double. Near | degree preceding r, in a line from 
1782. ^ through T Orionis continued. Very unequal. L. r. ; 

S. dr. With 227, about 1 diameter of L. ; with 460, 
about 2 diameters of L. Pofition 35° 42' n. preceding; 
a little inaccurate. 
^^, Fl. 8"" Tauri praecedens ad boream. . 
oa. g. Double. ' About i j degree n. preceding the 8th 
1782. Tauri, or near 2 degrees f. following the 65th Arietis, 
in a line parallel to the Pleiades and e Tauri; a fmall 
telefcopic flar not eafily found. A little unequal. 
L. r»; S. d. _ With 227, lefs than 1 diameter of S. ; ; 

with . 

5-6 Mr. Herschel's Catalogue 

L with 460, near two diameters. Pofition 82* 48' {. 

56. Fl. 54^"" Ceti fequens ad an drum, 

06l. 12, Double. About | degree f. following the 54th, 
1782.. towards <5" Ceti. Nearly equal. Both r. With 227, 
about I diameter;, with 460, about il diameter. Po- 
fition 87° 39' n. following. 
^'j. Fl. 70^"" et 67'"^ Orionis pra^iens. 

061.12, Multiple. In a fpot which appears nebulous in the 
1-782. finder, and is about 50' fi-om the 67th, and 45^ from 
the 70th Orionis. More than 1 2 ftars in view with 
460 ; among them is a double ftar. The largeft of the 
bafe of an ifofceles triangle, e. preceded by four ftars in 
a line. Conliderably unequal. With 460, i full dia- 
meter of L. Pofition 19° 48' f. following.. 
38. ^ Lyrae (Fl. 12*"') fequens. Inter edu(9:ionem cornuum, 
Oft. 24, Double. About f degree following the 12th, in a 
J782. line continued from the 11 through the 12th Lyra:; 
the lafi- of a finall telefcopic triangle. Extremely une- 
qual. L. r. ; S. d. Not eafily feen with 227 ; with 
460, near 2 diameters of L. Pofition i^° o' n. pre- 
^(). Ab I (Fl. 18') Lyras /3verfus. 

oa. 24, Double. The moft fouth of two very fmall tele- 
11782. fcopic ftars, which are the fecond pair fituated in a line 
from I towards jG Lyrae. A little unequal. Both d. ; 
the fainteft object that can be imagined. With 460, 
about I diameter. Pofition y c^^ o' f. preceding; the 
meafure is liable to fome error from the obfcurity. 
60. E telefcopicis 7/ et X Lytic auftralioribus ct fcquentibus. 


of Double Stan, 57 


oa. 24, Double. About | degree X following x, la a Hue 

1782. parallel to a and 'y Lyrae; a very fmall tclefcopic ftar. 
Extremely unequal. Both dr. With 227, i full dia- 
meter of L ; with 4.60, near 2 diameters of L. Poii- 
tion 16^ 48' n. preceding. 

6r. Pra^iens Fl. i^'^' Equulel. 

oei. 26, A minute double flar. About | degree n. preceding 
1782. the ifl: Equulei, in a line parallel to « Equuiei and 
y AquilcC ; a, large fl:ar. Very unequal. Both pr. 
With 460, I diameter of S. Pofuion 18^ 24' n. pre- 
ceding. A pretty obje6l, but requires fine weather. 

62. Sequitur Fl. 2^"' Equuiei.. 

oa. 29, Double. About | degree f. following the 2d Equuiei, 
1782. in a line parallel to I Delphini and (5* Equuiei. Conii- 
derably unequal. Both r. With 460, il or !| dia- 
meter of S. Pofition 35° 9' f. preceding. 

6'^, y Equuiei (Fl. 5^) auftrallor. 

oa. 29, Double. Full I degree f. of 7, in a line fi-om the 
L782. 5th through the 6th Equuiei continued. Equal. Both 
dr. With 227, about I diameter fcarce vifible ; with 
460, about I diameter. Pofition 5^ ^j' f. preceding. 

64. TT x\rietis. Fl. 42. In poplite. 

oa. 29, Treble. Exceffively unequal. L. w ; S. both mere 
1782. points. With 227, neither of the fmall ftars can be 
itQw, except with confiderable and, long continued atten- 
tion, when .they alfo appear;- the. neareft with this 
power is | or 1. diameter of L. ; with 460, 1 1 or 1 1 
diameter of L. The third is about 25^'' or 16'^ dlftant 
from L, by exa£t eflimation. Pofition of both, being 
all three in a line 19° 19^ f. following; as exacl as the 
obfcurity will permit. 
V0L. LXXV. I 6s^ 

^8 Mr. Herschel's Catalogue 

I. 65. Ill Nubecula /3 Sagitt;^ adjecla et fequenti. 

Nov. 4, Double. I degree n. following /3 Sagittie, towards 
1782. 2 9tli Vulpeculs ; the largefl and moiL fouth of a clufter 
of fmall ftars that appear cloudy in the finder. Very 
unequal. L. rw. ; S. pr. With 22^, full i diameter 
of L. ; with 460, about 1 1 or 2 diameters of L. Po- 
fition 14° o' n. preceding. A third flar in view, of the 
5th or 6th clafs. 

66. /3 (Fl. 23^) Draconis auftralior et prsecedens. 

Nov. 4, Double. About 1 1 degree f. preceding /3, in a line 
1782. from V continued through ^ Draconis. Pretty une- 
qual. Both pr. With 460, 1 1 or 1 1 diameter of L. 
Poiition a° 24' f. preceding, 

6y. Nebulam Aurigas pedem dextrum fequentem, priccedens. 

Nov. 4, Double. About 55' from the 37th Nebula of M, 

1782. Messier ; the largeft and mod preceding of two flars. 
Very unequal. Both pr. With 460, near 2 diameters 
of L. Poiition 23° 57^ n. following. 

68. Parvula Fl. io'^ Orionis quam proxime adjecla. 

Nov. 5, Double. The fmall ftar not many minutes from the 
1782. loth Orionis. A little unequal. Both whitifh. With 

460, near i diameter. Poiition 84° 54' f. following; 

a little inaccurate on account of the difficulty of feeing 

the ftars well. 

69. In Lyncis pedlore. 

Nov. 13, Double. About 3 degrees f. preceding the 19th 

1782. Lyncis, in a line drawn from the 19th Lyncis to t Au- 

rigas ; the 24th and 19th Lyncis alfo point to it nearly : 

in a very clear evening it may juft be feen with the 

naked eye. A little unequal. Both rw. With 227, 

I dia- 

of Double Suj?s. :^g 

I. I diameter ; with 460, i ^ or near 1 1 diameter. Poii- 

tioii 77^ o' f. following. 
70. f (Fl. 1235) Tauri borealior et prxcedens. 

Nov. 13, A very pretty double ftar. Near i degree n. pre- 
1782. ceding f Tauri towards Capella ; the corner of a rhom- 
boid made up of (^, this, and two more, and oppofite 
to ^. Confiderably unequal. ' L. pr. ; S. a little deeper 
r. With 227, almofi i diameter of L. ; with 460, 
1 1 diameter of L. Pofition 36" 24^ f. preceding. 

7*. Fl. 44'"" Urfas majoris priccedens ad auftrum. 

Nov. 1 9, Double. Nearly in the interfection of a line from 
1782. iG Urfi£ majoris to the 39th Lyncis, crofled by one from 
4^ to u UrfcE majoris ; the lafh line fhould bend a little 
towards t1> Urf^ majoris. A little unequal. Both 
whitilh. With 460, near 2 diameters of S. Pofition 
2^ 6^ n. following. 

72. Fl. 6^, Urfse majoris. 

Nov. 20, Double. Excefiively unequal. L. pr. ; S. a point. 
1782. Not vifible with 227, nor hardly to be fufpe£l:ed unlefs 
it has been firft feen with a higher power ; with 460, 
1 1 diameter of L. or, when long viewed, full z dia- 
meters of L. Polition 53° 45' n. following. A third 
ftar in view. Equal to L. Colour rw. Diftance 
i' o'^ 4'^'. Pofition 22" 21' f. following. 

y^, jQ (Fl. 6") Arletis borealior et prsecedens. 

Nov. 22, Double. About 1 1 degree n. preceding /S Arietis, 
1782. towards /3 Andromedse ; a confiderable ftar. Very une- 
qual. L. r. ; S. deeper r. With 227, about | dia- 
meter of L. ; with 460, full i| or almofi: if diameter 
of L. when beft. Pofition yy^ 24' f. following. 

I 2 74. 

6o Mr. HercCKEl's Catalogue- 

I. 74. Fl. 39^ i\rietis borealior et prascedens. 

Dec. 22, Double. About | degree n. preceding 39 Arletis, 

1782. towards <)/ Triaiiguli ; a pretty large telefcopic ftar, A 
little unequal. Both pr. Witli 227, near i diameter 
of L. ; with 460, about i§ diameter of L. Politloa 
20° 36^ n. preceding. 

75. Fl. 26''"" Orionis prxcedens ad auftrum. 

]an. 9, Double. About I degree f. preceding the 26th, ia 
1^83. ^ liiie parallel to (5" and /3 Orionis; the tartheft of two ;, 

or I degree f. preceding the 30th in the fame direction. 

Nearly equal. Both w, or r\v. With 460, perhaps a 

diameter. Pofition 89° 36' n. preceding; but not very 


76. In pe£lore Lyncis. 

Tall. 23, Double. Not eafy to be found. A line from the 19th* 
178^. Lyncis to u Geminorum eroded by one from Q Urfic 
majoris to e Auriga^, points out a ifar but juil; viliblejn 
a fiiie evening; it. is -perhaps about three degrees^from 
the 19th Lyncis; when that flar is found, w^e have the 
double ftar about i degree 11. following the fame, in a 
line parallel to r Geminorum and the 19th Lyncis. 
Confiderably unequal. Both afh w. , With 460, I 
diameter of. S. Pofition o' o' preceding. A third 
laroe ftar ill' view. .Diftance 1/ i'[ 46'^'.- Pofitioa 
3^ 42' f. preceding, 

7*^. K (Fl. 7^) Crateris borealior. 

Tan. 31, Double. Near 2| degrees north of a Crateris; a 

1783. fmall telefcopic fiar, about I degree following the 
mod north of two large ones. Pretty unequaL Both 
whltifn. With 227, iefs than half diameter of S. ; 


of Double Stars. 6 1 

I. with 460, near i diameter; with 625, a little more 

than I diameter. Poiition 82^ 2\' n. following. 

78. Fl. I i^ Librae borealior. 

Jan. 31, Double. Near 2| degrees north of the i ith Librae, 

1783. in a line parallel to |W Virginis and the 109th of the 

fame conftellation. Equal. Both inclining to r. With 

460, full I diameter. Poiition 58^ 24' n. preceding, 

or f. following. 

79. Fl. 46 Herculis. In dextro latere* 

Feb. 5, Double. Extremely or almoft exceflively unequal. 

17S3. L. w. ; S. d. With 227, it is hardly vifible ; with • 
460, near i diameter of L. Pofitlon 66^ 36' f. fol- 

80. Fl. 81 Virginis. 

Feb. 7, Double. Equal. Both pr. With 227, near 1 dla- 
1783. meter; with 460, f diameter. Pofition 41*^ 12^ n. fol- 
lowing or f. preceding. 

81. TT Serpentis (Fl. 44^"") prascedens ad auflrum. 

]Mar. 7, Double. About i\ degree f. preceding tt, towards 
1783. k; the mofl: north of two. A little unequal. Both 

r. With 460, If diameter of L. Pofition 49° 48^ f. 

preceding. A third large ftar in view ; paler than the 

other two. Diftance from the two taken as one ftar 

56'' 28'''. Pofition, with L. of the two, 31° 48' f. 

S-2. Fl. 49 Serpentis. 

Mar. 7, Double. The moft north and • following of two 
1783. ftars. A little unequal. Both pr. With 227, I or I 

diameter, and a very minute and beautiful object ; 

with 460, ■ I diameter. Pofition 21° ^^' n. preceding. 
3 S3' 

'62 AI . ^"terschel's Catalogue 

1.83. A Ophiuchi. Fl. 10. In ancone fiQlilri brachii. ^ 

M^v. 9, A very beautiful and ciofe double ftar. L. w. ; S. 
1783. blue; both fine colour? Conliderably or almoil: very 
unequal. With 460, | or J- dinmeter of S. ; with 
932, full } diameter of S. Ponlion 14° 30^ n. fol- 

84. Fl. ^o^ Aung2e auftralior. 

Mar. 18, Double. Near i degree f. of the 50th Auriga^, in 

1783. a line parallel to /3 and 0. Very unequal. L. r. ; 

S. dr. With 227, about I diameter of L. ; with 

460, almoftj i^ diameter of L. Pofition 14° o' n. 


85. Fl. 36^"" Lyncis fequens ad auftrum. 

Mar. 24, Double. Near f degree f. following the 36th Lyn- 
1783. cis, in a line parallel to the 31 ft Lyncis and n Urfte 
majoris ; of two the neareft to the 31ft Lyncis. Con- 
fiderably unequal. Both w. With 227, i diameter of 
L. ; or when long kept in view, 1 1 diameter of L. ; 
TOth 460, and after long looking, 2 diameters of L ; 
otherwife not near fo much. Pofition 88° 57' n. fol- 

86. Fl. 105^ Herculis borealior. 

Mar. 27, Double. One full degree n. of the 105th Herculls, 

1783. in a line from the 72d Serpentarii continued through the 
105th Herculis ; a fmall telefcopic flar. Confiderably 
unequal. Both dr. With 460, a little more than i 
diameter of L. Pofition 'j^° z/\! n. preceding. 
tj. q Ophiuchi. Fl. y^. 

April 27, A very minute double ftar. Confiderably unequal. L. r. 

1783. S. r. With 227, not to be fufpe<5led unlefs known to 

be double, but may be feeii wedge-formed, and with 

6 long 

of Double Slurs, 6q 

L long attention I have alfo perceived a mofl minute divi- 

fion ; with 460, about | or } diameter of S. Pofition 
2° 48^ f. preceding. 

88. T Ophiuchi. Fl. 69. In dextra manu fequens. 

April 28, The clofefl of all my double ftars ; can only be fuf- 
17S3. pe6led with 460; but 932 confirms it to be a double 
ftar. Pretty unequal. Both pr. or wr. It is wedge- 
formed with 460; with 932, one-half of the fmall 
ftar, if not three- quarters feem to be behind the large 
ftar. Pofition of the wedge 61° 36' n, preceding. 
V Ophiuchi, jufl: by, is perfectly free from this wedge- 
formed appearance. 

89. Illas ad Fl. 56*"" Andromcdae praecedens ad boream. 

July 28, Double. About f degree preceding, and a little north 

1783. of the two ftars that are about the place of the 56th An- 
dromeda, in a line towards j«; a conliderable ftar; and of 
two in a line parallel to (3 and y Trianguli that which 
is nearefl to the 56th Andromedse. Pretty unequal. 
L. drw. ; S. dpr. With 227, near i diameter of L. ; 
with 460, about i| diameter of L. Pofition 75° 30' 
f. following. 

90. jQ Aquarii (Fl. 22^"") praecedens ad auflrum. 

July 31, Double. About 4 1 degrees from jG towards ^ Aquarii. 

1783. A little unequal. Both dw. or pr. With 460, li 

diameter or near 2. Pofition 77° 36^ £ following. 

91. y Aquilae (Fl. 50^''') praecedens ad boream. 

Aug. 7, Double. About f degree n. preceding 7, in a line 

1783. parallel to y and ^ Aquilas; of two that nearefl to y. 

Very unequal. L. dpr. ; S. d. With 227, hardly 

vifible, and like a ftar not in focus; with 460^ appears 


64' '^^' Herschel's Catalogue 

I. nebulous on one fide, but is a double flar; with 932,. 

about i\ diameter of L. Pofition 8° 18' n. preceding. 

92. 17 Aquilae. Fl. 52. Duarum in finiftro humero fequens. 
Aug. 27, A minute pretty double flar. A little unequal. 

1783. Both pr. With 460, f diameter of L. or near % dia-, 
meter of S. Pofition 34.° 24^ f. following. 

93. Fl. 62^"™ Aquilas prcecedens adboream. 

Sept. 12, A minute double fiar. About | degree n. preceding 
1-83. the 62d, in a line parallel to ^ and J'Aquilce; a pretty 
confiderable ftar. Very unequal. Both inclining to pr. 
With 278, almoft in conta6t ; with 460, near | dia- 
meter of S. ; when in the meridian, and the air fine, 
near i diameter of L. Pofition 19° 9' n. preceding. 

94. ^ Cygni. Fl. i 8. In ancone alas dextrae. 

Sept. 20, Double. Very unequal. L. fine w. ; S. afh colour 
2783. inclining to r. With 27S, about \ diameter of L. ; 
with 460, I diameter of L. ; with 932, full i| dia- 
meter of L. in hazy weather, which has taken off the 
rays of L. and and thereby increafed the interval. 
Pofition 18° -21^ n. following; perhaps a little inac- 
curate. . 

95. Fl. 2)3'''^ Cyg^^i fequens ad au drum. 

Sept. 22, Double. Full 1 1- degree f. following the 33d, 
1783. towards J Cygni ; a pretty confiderable ftar. Very une- 
qual. L. w. ; S. inclining to r. With 460, at firfl 
about f diameter of L. ; but, after looking a confidera- 
ble tinae, and in a fine air, near \\ diameter. Pofition 
72° 15' n. preceding. 

96. ?j (Fl. zi''") Cygni fequens ad aufirum, 

Sept. 23, Treble. Full i| degree n. following ij, in a line 
i!783, parallel to Q and A Cygni, The two neareft confiderably 


of Double Stars, 6$ 

I. unequal. Both pr. With 460, i diameter of S. or | 
diameter of L. Pofitioii 89° 18' f. following. The 
two farthefl: confiderably unequal ; the colour r. Did. 
Pofition 56° 3' n. preceding. 

^y. Fl. 51*" Cygni fequens. 

Sept. 24, A minute double ftar. About 2I degrees following 
1783. the 5 1 ft, in a line parallel to ^ and a Cygni ; the largeft 
and moft fouth of an obtufe-angled triangle ; a very 
confiderable ftar. Pretty unequal. Both rw. ; but S. 
a little darker r. With 278, | diameter of S. and 
beautiful ; with 460, | diameter of S. Pofitioii 46" 
24' n. following. v 


II. 39. Procyonem juxta. 
Feb. 2, Double. About 2 degrees f. following Procyon, in 
1782. a line froni \ Geminorum continued through Procyon. 
Exceflively unequal, L. pr. ; S. not vifible with 278 ; 
with 460, more than 3 diameters of L. Pofition, by 
the affiflance of a wall * and micrometer 54^ 28' fl 


* When the fmall ftar is fo faint as not to bear the leafl illumination of the 
wires, its pofition may flill be mcafurcd by theafilfranceof fome wall or other obje6l; 
for an eye which has been fome time in the dark, can fee a wall in a flar-hght 
evening fufficiently well to note the projection of the Hars upw it, in the manner 

VOL. LXXV K which 

66 Mr. Her scH el's Catalogui 

11. 40. * Secunda ad (?; Cancri. Fl. 23. 

Fe:^. 2, Double. A little unequal. Both nv. With 227,, 
J782. near 2 diameters ; with 460, 2-2- diameters of L. Po- 
fition 56° 42'' n. following. 

41. * Prima ad v Cancri. Fl. 24. 

Teh. 2, Double. Confiderably unequal. Both pr. With- 
1782. 227, 1 1 diameter of L. ; with 460, 4 diameters of L. 
Pofition 32^ 9' n. following, 

42. E telefcopicis k Virginis precedentibusf. 

Feb. 6, Double. i\bout 1 1 degree f. preceding k Virginis, 
1782. ill ^ line parallel to f and ^; the moft fouth of three 
forming an arch. Extremely unequal. L, w. ; S^ 
hardly vifible with 227 (but with a ten-feet refle£lor 
S. b.) ; with 460, above 2 diameters of L. Pofitioa 
52° 24^ f. following. 

43. Fl. 43''" Leonis praecedens ad auftrum. In dextro genu. 
Feb. 17, Double. Near f degree f. preceding the 43d, in a 
1782. hne parallel to c<, and the 14th Leonis. Very unequal. 

L. w. ; S. d. With 227, near 2| diameters of L,. 
W'hen heft. Pofition 85° 2' n. following. 

44. Virginis. Fl. 84. Verfus finem alse dextra^. 

Feb. 17, Double. Extremely unequal. L. w. incUning to r. ; 
1782. S. d. Requires attention to be feen with 227; with. 

460, 2i diameters of L. Pofition, with 278, 29° 5' 

f. preceding. 

which has been defcribed with the lamp-micrometer, Phil. Tranf. vol. LXXII. p. 
269 and 170. Then, introducing fome light, and adapting the fixed wire to 
the obferved diredion of the liars on the wall, the moveable wire may be fet to 
the parallel of the large ftar, which will give the angle of pofition pretty 

f See note to IV. 5r» 


of Trouble Stars. 6j 

II. 45. Fl. 54 Vlrginls. 

April 3, Double. A little unequal. Both w. With 227, 
1782. il or near i| diameter, Pofition 57" o' n. follosvlng, 

46. Fl. 42^"^ Comae Berenices fequens ad auftrum. 

April 15, Double. About i| degree from the 42d Comer 
1782. towards v Bootis ; the mofl fouth of a telefcopic equi- 
lateral triangle. Exceflively unequal. L. pr. ; S. d. 
With 278, 2 J diameters of L. ; not fo well to be feeii 
\vith higher powers. Pofition 6^ 42^ f. following. A 
third flar preceding, above i \ 

47. Fl. 2 ComiE Berenices. 

April 18, Double. Confiderably unequal. L. rw. ; S. pr. 
1782. With 278, 2 diameters of L ; with 460, above 3 dia- 
meters of L. Pofition 27° 42' f. preceding. 

48. Prope Fl. 16*'" Auriga^. 

Aug. 28, A minute double ftar. Lefs than | degree f pre- 
1782. ceding the i6th, in a line parallel to the 10 and 8 
Aurigas ; the preceding ftar of a fmall triangle of which 
the 1 6th is the largeft and following. A little unequal. 
Both pr. With 227, i| or, when heft, i| diameter 
of L. Pofition 15° 48^ n. following. 

49. (Fl. iio*)Pifcium borealior. In lino boreo. 

Sept. 3, Double. About I degree n. of, and a little pre- 
1782. ceding iioth, towards vj Pifcium. A little unequal. 
Both wr. With 460, about 3 diameters of L. Pofi- 
tion 59° 6' n. preceding. A third ftar in view, about 
1 1 min. 

50. Fl. 38. Pifcium. In auftrino lino. 

Sept. 4, Double. Pretty unequal. Both pr. With 227, 
1782. full 2 diameters of L. ; with 460, about 4 diameters- 
of L. Pofition 25"^ 3^ f. preceding, 

K 2 51. 

68 Mr\ H£R9Cbel's Catalogue 

II. 51. p Caprlcorni. Fi . 11. Triuin in roflro fequens. 
Sept. 5, Double. Very unequal* Both rw. With 460, l| 
1782. diameter of L. Pofition 84° o' f. following. A thicd 
ilar in view. 

52. (Fl. 40'"') Perfei pr^xedens ad boream. 

Sept. 7, Double. Almoft | degree preceding the 40th, in a 
1782. line parallel to ^ and the 38th Perfei. Equal. Both w. 
With 227, nearly 2 diameters. Pofition 8'' 24' n. pre- 

53. Fl. 12*'" Camelopardali praecedens. 

Sept. 7, Double. Lefs than \ degree preceding the i ith and 
1782. I2th, in a line from the ift Lyncis continued through 
the 1 2th Camelopardali. Extremely unequal. Both 
dr. With 227, it appears like a ftar with a tail; but 
932 fhews it plainly to be only a double ftar ; with 
227, not much above i diameter of L. ; with 932, 
H ; about 3 1 diameter of L. Pofition 18° ^'^^ f. following ; 

a little inaccurate. 
fj4. Qua3 praecedit & (Fl 74*'", oculum boreum) Tauri. 
Sept. 7, Doubk. Near i degree f. preceding e, in a line 
1782. parallel to a and y Tauri; a fmall flar. Extremely 
unequal. L. rw. ; S. d. With 460, above 3 diameters. 
of L. Pofition 68° 42^ f. preceding. 

55. Fl. 4^ Ceti auftralior et fequens. 

Sept. 9, Double. About i degree f. following the 4th and 
1782. 5th in a line parallel to oj and r Ceti ; in the fhorter leg 

of a redangular triangle. Very unequal. L. r. ; S. 

d. With 278, rather more than 2 diameters. PofW 

tion 21° 42' n. preceding. 

56. /3 (Fl. 6*"") Arietis priEcedens ad boream. 

7 Double 

of Double Sl< 69 

II. Double. Almofl: i degree n. preceding fo Arletis, 

Sept. 10, towards f Andromcdac ; a fmall ftar. A litrle unequal. 

17S2. Both reddifh. With 227, full 2 diameters ot L. Puli- 

tion 23'' 1 2' n. preceding. A ."bird flar r/ or 7,' preceding, 

in the lame diredion with the two flars of the double ftar. 

57. Ad Fl. 72"" Aquarii. 

Sept. 27, Treble. About 2| degrees following ;c, in a line parallel 

1782. to ot and 71 Aquarii. The nearefl: a little unequal. Both 

r. With 460, 2\ diameters of L. Pofition 25° 51^ f. 

preceding. The two fartheft a little unequal. Of the 

5th clafs. About 50° or 55° f. following. 

58. Fl. 56^Ceti auflralior et fequens. 

Sept. 27, Double. About | degree f. following the 56th, In a 
1782. hne parallel to ^ and t Ceti. Confiderably unequal. 
Both dw. W^ith 278, i{ diameter of L. Pofition 
25° 12' n. preceding; too low for accuracy. 

50. (Fl. 46*"') Aquarii fequens adaullrum. 

Sept. 3c, Double. About 2 degrees f. following^, in a line pa- 

1782. rallel to /9 and I Aquarii ; there is a very confiderable il:ar 

between this and ^, not much out of the line. Pretty 

unequal. Both dr. With 227, 2j or 2$ diameter of 

L. Pofition 61° 12' n. preceding. 

60. £ (Fl. 5*"") Canis majoris fequens ad boream. 

Sept. 30, Double. About \ degree n. following the 2d ad |, 

1782. in a line from the 4th continued through the 5th 

Canis majoris nearly. Very unequal. L. rw. ; f. d. 

With 227, 1 1 diameter. Pofition 67° 36' n. preceding. 

61. TO- (Fl. 47^"") Orionis fequens ad auftrum. 

oa. 2, Treble. About ij| degree f. following tat In a line 

1782. parallel to (p and « Orionis ; the fmalleft and moft fouth 

of three forming an arch. The two nearefl extremely 


T5 Mr, Hersciiel^s Catalome 

jI. Dneqiuil. L. dw. ; S. a mere point. With 227, 1 1 or 

1 1 diameter of L. Pofition 4° 54' n, following ; too 
obfcure for accuracy. The two fartheil: extremely inie- 
qual. S. a mere point. Of the fourth clafs. Pofi- 
tion about 50 "■ f. following. 

62. Fl. 3^ Pegaii adje£la. 

oa. 4, Double. In a line with, and north of, the two flars 
1782. that are about the place of the third Pegafi. A little 
unequal. Both dufky r. With 227, about 3 dia- 
meters of S. Pofition 88*^ 24' n. preceding; perhaps a 
little inaccurate. 

63. Fl. 3*"' et 4^™ Navis prsecedens. 

oa. 12, Multiple. Near 2 degrees preceding the 2d and 4th 
J782. Navis; the middle one of three. One of the multiple 
is double. Nearly equal. Both w. or afh colour. 
With 227, about ^\ diameter, and not lefs than 20 
ftars more in view ; with 460, about 3 diameters. Po- 
fition 30° 12^ n. preceding, 

64. g (Fl. 81*"") Geminorum ad auflrum fequltur. 

oa. 13, Double. About \ degree f. following^, in a line from 

1782. f continued through^ Geminorum nearly; the neareft 

and largeft of two. Very unequal. L. r. ; S. bluifh 

r. With 227, above 3 diameters of L, Pofition 

4° 9'' n. preceding. 

65. Pollucemfequens ad boream. 

Oci:. 13, Double. Full | degree n. following /3, in a line from 
1^82. ^ continued through /3 Geminorum; the ftar next to 
the middle one of three, nearly in a line. Exceflively 
unequal. L. rw. ; S. d. With 227, above 2I or near 
3 diameters of L. and 5 other ftars in view ; with 460, 
above 3 diameters of L. Pofition 89° \z' n, following. 
^ 1 66, 

of Double St^rs* rt 

II. (i(^, Juxta y Delphini. 

Ocl. 19, Double. Full | degree f. preceding y, towards ^ 

3782. Delphini. Confiderably unequal. L. pr. ; S. r. With 

227, il diameter of L. Pofition 78'' 4.2^ n. preceding.. 

67. /G (Fl. 10'™) Lyras praecedens ad boream. 

Oft. 19, Double. The 4th telefcopic flar about if degree n. 

1782. preceding /S, in a line parallel to y and cc Lyras, Ex- 
tremely unequal. L. r. ; S. dr. With 227, i\ or 
almofl 1 1 diameter of L. With 460, above z- diame- 
ters of L. Pofition 68° 6' f. following. 

68. Proxime ^ Lyrae. 

oa. 24, Treble. About 2| minutes f. following ^ Lyras. 
1782. The two neareft, a httle unequal. Both dr. With 
460, 3 full diameters. Pofition 8° 24' n. following. 
The fartheft as large as L. of the two neareft at leaflu 
Colour dr. Pofition with L. 25° 57' f. preceding.. 
Diftance of ^ Lyrae, which is in view, from the two 
neareft 2I ly" ^o''\ Pofition 6^"" 12', ^ being n. pre- 
ceding, or the double ftar f. following. 
^9. Fl. 4^"" Cygni fequens ad boream. 

oa. 24, Double. Near | degree n. following the 4th Cygni, 

1782. ifi a line from y Lyrse continued through the 4th 

Cygni. A little unequal. Both w. With 227, about 

2 diameters of L. or 2| when beft. Pofition 29° 12' 

n. following. 

70. rm 8 telefcopicarum % (Fl. 15.) SaglttiE fequentium, , 

Nov. 6, Double. About 1 1 degree f. following % Sagitt^, in 
J 7 82. a line parallel to y Sagittse and y Delphini. Extremely 
unequal, Both r, ; S. deepei: r. With 227, i| dia- 

72 Mr, Herschel's Catalogue 

\[, meter of L. ; with 460, above 2 diameters of L. Po- 
fition nz' 57' n. following. 

7 I . Fl. 58' Aurigae auftralior. 

Nov, 6, Multiple. About | degree f. of the 58th Aurigae, in 
1782. a line parallel to /3 and Q. A clufter of ftars containing 
a double ftar of the fecond, and one of the third clafs. 
That of the fecond very unequal. Both r. With 
460, about 2 1 diameter of L. Pofition 44° 36' n. 
following ; that of the third equal. Both r. With 
227, above 20 ftars in view. Diftance ly" 41'^'. The 
two double ftars are in the following iide of a fmair 
telefcopic trapezium. 

72. Fl. 13^ Lyncis auftralior. 

Nov. 13, A pretty double ftar. About i| degree f. of the 13th 
1782. Lyncis, towards Q Geminorum ; a conliderable ftar. 
Nearly equal. Both pr. With 227, full 2 1 diameters; 
with 460, almoft 4 diameters. Pofition 11° o' f. pre- 

73. Fl. 21* Urfae majoris. 

Nov. 17, Double. Very unequal. Both rw. With 227, zl 
17S2. diameter of L. ; with 460, above 3. Pofition 36° 45' 
n, preceding. 

74. V (Fl, 4*)Crateris borealior. 

Nov. 20, Treble. Near i degree n. preceding v Crateris, 
1782. towards a, Leonis. The two neareft equal. Both dw. 
With 227, 2i or 3 diameters. Pofition 71° ^'^' n. fol- 
lowing. The fartheft larger than either of the two 
other ftars. Of the fixth clafs. Pofition about 68 or 
69° f. preceding the double flar. 

cf Doubk Stars, jrj 

II. 75. Fl. 1 18 Tauri. 

Dec. 7, Double. A little unequal. L. vv. ; S. w. Incrming; 
1782. tor. With 278, 2.1 diameter of L. ; with the fame 
power by the micrometer j^" 41'^^; more exai^lly with 
625, 5'' 2' ^ Polition 77" 15'. I could jull; fee it 
with ail 18-inch achromatic, made by Mr. Nairne; it 
was as clofe as poffible, and a pretty objeft. 

76. T (Fl. 6'^^) Arietis auftralior etpr^cedens. 

Dec. 23. Double. About i degree f. preceding r Arietis, 

1782. towards ^ Ceti ; the mofl: fouth of two fmall teiefcopic 

ftars. Nearly equal. Both w. With 227, above 3 

diameters; by the mici-ometer ^" ^"^"'^ Pofition 15'' 

24' f. preceding. 

77. *Fl. 17 Hydrse. 

Dec. 28, Double. The largeft of two. A little unequal. 

1782. Both w. With 227, 2 1 diameter of L, ; with 460, i| 
diameter. Pofition 90° o' north. 

78. ;^ (Fl. 63""') Leonis fequens ad auftrum. 

Jan. I, Double. About f degree f. following ;:^/, towards r 

1783. Leonis; the fmalleft of two. Very or extremely un- 
equal. L. r. ; S. d. With 227, 3 full diameters of 
Lr. Poiition 75° 21' f. following. 

7p, Fl. 39 Bootis. 

Jan. 8, A pretty double jftar. A little unequal. Both pr. 
1783. With 227, near i| diameter of L. ; wnth 460, near 2 

diameters of L. Pofition 38° 21' 11. following. 
80. d (Fl. 40*) Eridani adjeda. 

Jan. 31, Double. About if min. f. following d Eridani. 
1783. Very unequal. Both dr. With 227, hardly vifible ; 
with 460, very obfcure. Pofition 56° 42' n. preceding. 
Vol. LXXV. L * Diftance 

74 ^^' Herschel's Catalogue 

II. Diftance of L. from ^Eridani, with 227, i' 2i^'47^''» 

Pofition of L. 17° 53^ f. foliowlng c/'Eridaiii. 
81. Fl. 49^"" Eridani fequens. 

Jan. 31, Double. Near i degree following the 49th Eridani^ 
J 783. towards I Orionls. Very unequal. Both dw. With 
227, full I diameter of L. ; with 278, 1 1 or i| dia- 
meter of L. ; with 460, 2.1 or.3 diameters of L. Po- 
lition 51° 36' n. preceding, 
82: Fl. 31^"" Bootis fequens ad auftrum. 

Feb. 3, Double. Near i degree f, following the 31 ft, in a 
1783. line from v continued through the 3 1 ft Bootis ; the moft 
fouthoftwo. A little unequal. L. w. ; S. dw. With. 
227, about 1 1 diameter of L. ; with 460, about 3 dia- 
meters of L. Pofition 1 ° o^ f. following. A third flat 
,! , , . in view, 20° or 30° n. preceding. 

83. Fl. 22^ Andromedse boreaiior. 

Feb. 26, Double. Within | degree north of the 2 2d, in a 
1783. line parallel to the 19th and i6th Andromedae; the fol- 
lowing and fmallefl: of two. Confiderably unequal. L.w.; 
S. d. With 227, lior if diameter, of L. ; with 460, 
more than 2 diameters of L. Pofition 5° 48^11. following. 

84. Fl. 65 Pifcium. , 

Feb. 27, Double. Nearly equal. Both pr. With 227, near 
1783. i I diameter of L. ;, with 460, full 2 diameters. Pofi- 
tion 30° q7^n. preceding. 

85. b (Fl.. 36'') Serpentis boreaiior et fequens. 

Mar. 4, Double. About I i degree n. following ^, nearly in 
1783. a line from the 3 2d continued through the 36th Ser- 
pentis. Extremely unequal. L. w. ; S. dw. With 
227, I full diameter of L. ; S. hardly to be feen ; with 
460, full 2 diameters of L. Pofition 46° 9' n. preceding, 


tf Double Stars, 75 

IT. 86. Fl. 49"™ Serpentis praecedcns ad auftrum. 

Many-,- Double. About 1 1 degree f. preceding the 49tli, in 

3.78'^. a line with the 49th atid another between this and the 

49th Serpentis, each nearly at |- degree diflance. Very 

unequal. L. dw. ; S, d. With 227, 2 diameters, or 

2| when beft. ' Poiition ^^"^ 9^ f. following. 

87. F-L. 29^et30^ Monocerotis anftralior. 

Mar. 8, Multiple. It makes nearly an equilateral triangl^i 
j_8o. with the 29th and 30th Monocerotis towards the fouth. 
Among many, the fourth from the fouth end- of an 
irregular long row is double. A little unequal. Both 
pr. With 22p, 1 diameter of L. and 16 more in 
view. Pofition86'' 12' f. following. 

88. 0} (Fl. 5t'"^) Serpentis prscedens ad auftrum. 

MaT. 8, Double. About i degree' f. preceding the 5ifl:, 
'1783. towards the 13th Serpentis,- Very or extremely une- 
qual. Both r. With 1227, zl diameter of L. when 
beft; with 46b, .near '3. diameters of L. Pofition 
44° 45' n. preceding. 

89. Ad Genam Monocerotis. 

Mar. 26, Double. About i degree n. preceding the 1 2th Mo- 

-1783. • nocerotis, in a line parallel to « and x Orionis ; the 
fmallefl and moil liorth of two. Coniiderably une- 
qual. L. r. ; S. bluifh' r. With 227, near 4 diame- 
ters of L. when befl. Pofition 50° 51^ n. following. 

00. Fl. ioo^"* Herculis prsecedens ad boream. 

Mar. 27, Double. About i| degree n. preceding the looth, 

1783. towards jtt. Herculis ; a very fmall telefcopic ftar; the 

moft towards ^a, and fmalleft of three forming an arch. 

Coniiderably unequal. Both dw. With 227, about 

2 .diameters of L. Pofition 75*^ 9^ f. foliovving* 

L 3 91. 


76 Mr. Hkrschel's Catalogue \ 

II. 91. % (Fl. 15^) Sagittic auftralior. 

Apr. 5, Treble. About twice as far ibutii of % Sagitta% as % 
J 783. and the ftar near it are from each other; a fmall ftar. 
The two nearefh very unequal. L. pr. ; S. r. With 
227, \i diameter of J^. Pofition 74.'^ 54' f. preceding. 
The third with L. extremely unequal. S. d. With 
227, about 3 diameters of L. or more. Pofition about 
40° or 50^ n. preceding. With more light this would 
be a fine objed:. 
92. In Camelopardali clune. 

Apr. 30, Double. About four times the diftance of the loth 
1783. and 1 2th Camelopardali, north of the loth, and almofh 
in the fam.e diredlion with the loth and 12th, is a ftar 
of between the 5th and 6th magnitude not marked hi 
Flamsteed ; naming that ftar A, we have the fol- 
lowing direction. About | degree preceding A Came- 
lopardali, in a line from the 2d L-yncis continued 
through A ; the fecond from A. Very unequal. L. 
w. ; S. dv With 227, if or 2 diameters of L. Po- 
fition 22° 42' f. following. Very inaccurate. 
^^, B (Fl. 13^) Aquilae auftralior. 

May 25, Double. Near | degree fouth of> and a little fol- 
1783. lowing f, towards A Aquilae, a very fmall ftar. Verj- 
unequal. L. dw. ; S. dr. With 460, above 2 dia- 
meters of L. Pofition 16" o'' n. preceding. 
^4. I (Fl. 17*"") Andromeda^ pra'cedens ad boream. 
Aug. 19, Double, About if degree n. preceding i Andromedas 
1783. in a line parallel to a and jG Caffiopeias ; in the fide of a 
trapezium of four fmall flars. Pretty unequal. Both 
r. With 460, 2i diameters of L. Pofition 54° 24' 
n. preceding. 


of Double Stars, 77 

II. 95. fi (Fl. k,^^^ Aquilse auftralior. 

Sept. 12, Double. About \ degree loutli of ^, in a line from 

178^. o-. continued througb y\ Aquilas ; a fmall ftar. A little 

unequal. Both dulky afli-coloured. With 460, near 

3 diameters of L. ; with 278, near 2 diameters of L. 

Pofition 29° 2! '^' preceding. 

96. ^ (Fl. 65^) x'\quilas borealior et fequens. 

Sept. i2» Double. About i| degree n. following^ Aqu/iki.^ 
1783. towards 6 Delphini ; more accurate towards 29 Vulpe- 
culae ; a very conflderable ftar. Nearly equal. Botli ■ 
rw. With 278, about \\ diameter of L. ; with 460^ , 
full 2 diameters. Pofition 56° I2^f. preceding. 

97. f (Fl. 64^"") Cygni praecedens. 

Sept. 15, Treble. About i degree preceding f, towards the 
•*7?3* 41ft Cygni; a large ftar. The two neareft extremely 

unequal. L. w. ; S. pr. With 460, 2f diameter^ Qf / 

Xv, Pofition 45° 15' n. preceding. The third with L. 

extremely unequal. Of the 5th or 6th clafsr; about : 

50° f. preceding. 

98. Fl. 49 Cygni. 

Sept. 15, Double. Very unequal. L. r. ; S. bluJfh r. With 
1783. 278, If diameter of L. ; with 460, ^\ diameters of r 
L. Pofition 31^48^ n. following. 

99. /S (Fl. 6*'") Cygni fequens adboi'eam* 

Sept. 15, Double. Near | degree n. following /?, towards | 
1783. Cygni. Very unequal. Both dw. With 278, i| 

diameter of L. ; with 460, about z diameters of Lo . 

Pofition 87° 48' n. following. 

100. Fl. 51^ Cygni boreallor et fequens. 

Sept. 24, Double. Near two degrees n. following the 51ft ^ 
1783. Cygni, in a line parallel to Cygni and a Cephei ; a 

yS Mr. Herschel's Catalogue 

II. pretty confiderable ftar. Very unequal. L. w. ; S. 

inclining to' blue. With 278, extremely unequal, 
and I i'diarrieters' of L; when bed ; requires attention to 
be feen wellwith this power ; with 460, full 2 diame- 
ters of L. or 2|' when beft,- otherwife much lefs. Poli- 
tion 15° 5i''n. following. ' - 

10 1. Fl. 57^"* :: Canielopardali prsecedens ad boream. 

Sept. 26, Double. About 2 degrees n. preceding' the 57 :: , 
•1783. towards the 42d Cameloipardali ; a ' eoiifiderable.,ftfir 
near three fmaller, forming an arch. About 'i degree 
from the double ftar V. 135. Conliderably unequal. 
Both pr. V/ith 278, if diameter of L. ; with 460, 
2| diameters of L. Pofition 67° 15' ni, preceding. 

102. e (Fl. 29^) Orionis auftralio^r et pr^ecedens. 

Sept. 27, Double. About | degree f. precediug ^, in aline 

J783.. parallel' to ^ and jG Orionis ; the krgeft o^ feveral. Very 

* ''* .unequal. L. pr. ; S. inclining to garnet. ' With 278, 

inear 2 diameters of L. With 460, 2 1 diameters of 

L. Pofition 52° 24^ f. following. 

.1; •; :1rh-;'- 


III. 47. e Pollucis; Fl. 38 Geminorum. In cake. . 
Dec. 27, Double^ Extremely- unequal. L. rw* ; S. r. Dif- 
1781. tance, with 460, 7;^i48''^ Pofition .89° 54^ f. follow- 
ing. Two more in view, the nearefl of them perhaps 

40'^ ; thev form a redan gle nearly. 
. ; • ' , 48. 

' of Double Stjrs. ■ .yt^ 

ni. 43. ;• (Fii. 61''"') Gemlnorum piaDcedcns ad boream.' 
Dec. 27,, Double. About i degree n. preceding r, in a line 
J ''Si. parallel to a and the 60th Geminorum ; near two de- 
grees from ^. A little unequal. Both pr. Dirtance 
^// i^'^\ Pofition 43"^ 54^ n. following. 

49. ^ (Fl. 4'") Hydri£ priccedens ad boream. 

Jan. 20, Double. About 1 1 degree n. preceding ^, in a line 
1782. from 71 continued through ^ PIydri£. Pretty unequal. 

L. r. ; S. garnet. Diftance 12'' 30^^^ Pofition 62*^ 

48' n. following. 

50. 5 Virginis. Fl. 51. De quatuor ultima et fequens. 

Feb. 6, Treble. The two nearefl extremely unequal. L. w. ; 
1782. S. d. Diftance 7^^ 8^^^ ; but inaccurate on account of 

the obfcurity of S. Pofition 69° iS' n. preceding. 

For meafures of the two fartheft fee VI. 43. 

51. Fl. 88 Leonis. In dextro clune. 

Feb. g, Double. Extremely unequal. L. rw. ; S. r. Dif- 
1782. tance 14^^38^^^; a little inaccurate. Pofition. 47° 33' 
n. preceding. 

52. Fl. lo^'" Orionis fequens. 

Feb. 17, Double. Above i deg. n. following the loth, towards 
1782. w Orionis. Confiderably unequal. Both pr. Diflance^ 

with 278, 13'^ 40'^^ Pofition 37° 3^ n. follov/ing. 
53' y Virginis borealior et fequens. 

Feb. 17, Double. Near. 2 1 degrees n. following <)/, in aline 

1782. parallel to s and a. Virginis ; a conliderable f!:ar; a line 

from y to this pafles between two of nearly the fame 

magnitude with this ftar. A little unequal. Both d, 

Diflance 12'^ 58'^^ Pofition 79° o' n. preceding. 

2 54* 

^&- Mr. Herschel*s Catalogue 

III. 54. SecunJa ado- Urfs majoris. Fl. 13, la fronte. 
June 2, Double. Extremely unequal. L, w. ; S. r. Dif- 
1782. tance j" 56''^''. Poiition i3°o'n. preceding. 
^^. V (Fl. 18^"™) Coronie borealls fequens ad boream. 
June 14, Double. Coniiderably unequal. L. dr, ; S. d. 
1782. Diftance with 227, about 3 or 4 diameters of L. being 
too obfcure for the micrometer. Pofition ^tj' 4^' ^• 
preceding. Diftance of the largeft of the two from u 
Corons i' iW %"\ Poiition of the fame with u, 64"* 
24' n. following. 
:^6. S (Fl. 72^) Serpentarii borealior. 
June 16, Double. About 2f degrees n. of the yad Serpen- 
1782. tarii ; a confiderable fiar. A little unequal. Both r. 
Diftance 7^' 3y'''. Pofition 9° 42^ f. preceding, A third 
ftar about 1' preceding, 
■^'j. In Anferis corpore. 
Aug. II, A pretty double flar. About | degree n. of a clufter 
1782. of ilars formed by the 4th, 5th, 7th, 9th Anferis; in 
a line parallel tathe 6|:li Vulpeculasand /2 Cygnl ; that 
of two which is farthefl: from the clufler. A little 
unequal. Both r. Diflance Y' i'^'. Pofition 58° 36' 
f. followino", 
■58. 6 Perfei. Fl. 1.3. In finiflro humero. 
Aug. 20, Double. Extremely unequal. L. w. inclining to r. ; 
1782. S. d. Diftance with 932, 13'' 3^"'* Pofition 2 o'' o' 
n. preceding, A third ilar, very unequal, within i' ; 
towards the foutii. 
'^(), Ad Fl. i9''"Perfei. In capite. 

• Aug. 20, Doable. It is perhaps the 19th Perfei removed, or 
.1782. more likely a fear not marked in Flamsteed's Cata- 
logue ; the 1 9th being either vanilhed, or mifplaccd by 


of Double Stars* S^ 

III. Flamsteed. Pretty unequal. L. b\v. ; S. bi% Dif-"' 
taiice 12^' 2^'^ Pofitlon o" o^ following. 

60. Secunda ad / Perfei. Fl. 20. Illas in larva praecedlt.''^ '^''^ 
Aug. 20, Double. Extremely unequal. L. rw. ; S. d. DiC- 
1782. tance 14'' 1"'. Pofition 30° 30' f. following. 

61. Sub finem caudae Draconls. 

Aug. 29, Double. Of two confiderable flars, about half-way 

1782. between a, and i Draconis, that which is towards /. 

The two ftars are parallel to ^ and e Urfae majoris. 

Very unequal. L. pr. ; S. db. Diilartce 12^^30^'^^ 

perhaps a little inaccurate. Pofition 87^ 42' n. preceding. 

62. Fl. 35 Pifcium. In lino auftrino. 

Sept. 4, Double. Confiderably unequal. L. rw. ; S. pr. 
1782. Diflance 12'^ 3^^''- Pofition 58° 54^ f. following. 

63. Prope Fl. 65*™ Saglttarii. Ad extremum paludamentiim, 
Sept. 5, Double. Near | degree f. following the 65th Sagit- 
1782. tarii towards ^ Capricorni. Very unequal. Too low 

for colours; perhaps dw. Diflance 14'^ 20'''. Poli- 
tion 73° 48' n. following. 

64. Fl. 26 Aurigce. In dextri cruris irivolucro. 

Sept. 5, Double. Very unequal. L. rw. ; S. r, Diflance 
1782. 13 ' ^s"'' Pofition 2° 36^ n. preceding. 

65. e (Fl. 58'") Perfei aufrralior. In dextri pedis talo. 

Sept. 7, Double. About 10' fouth of the 58th Perfei, in a 

1782. line parallel to f and i Aurigas; a fmall telefcopic flan 

Very unequal. L. r. ; S. d. Diflance with 625, n'^ 

22''''. Poiition 48° 54' n. following. Very inaccurate t 


66. e Tauri. Fl. 30. In dextri humeri fcapula. 

Sept, 7, Double. Extremely unequal. L. w. ; S. r. Dif^ 
1782. tance 11'^ \6"' \ inaccurate on account of obfcurity. 
Pofition 17° 15' n. following. 
Vol. LXXV. M 67. 

III. 67-. ^ Leporis, Fl. 3. Borea praecedentis laterisqiiaclriiateri 

xid aures. 
Sept. 7, Double, Exceffively uneqijal. L. w. ; S. d. With 
ij82, 327, there was not a poffibillty of meafuriiig the dif- 
tance, though the glafs was carefully cleaned ; on try- 
ing 625, I found the ftar fo ftrong that It bore a very 
tolerable good light*. Diftance with this power iz^^ 
zo'" . Pofition 8v° 2.1' n. preceding. 
68. y] (Fl. 17*) Arietjs auftralior et praecedens. 
Sept. 10, Double. Full I degree fouth preceding 1;, in a line 
J 782. parallel to a and y Arietis. Very unequal. L. pr. ;, 
S. d. Diftance 8'' ^"\ Politlon SS"" 4^' 1^- following. 
^^. Prope Fl. 64"" Aquarii. In dextro femore. 
Sept. 27, Double. Full i| degree n. following the 64th :: , 
J 782. in a line parallel to \ and (p Aquarii ; the largeft of two 
that follow a very obfcure triangle in the hnder. Ex- 
tremely unequal. !>. rw. ; S. db. DIflance 12^' 4.6'''. 
Pofition 20° 3'' f. following. 
70. « Cephei. Fl. i. In dextro crure. 

Sept. 27, A beautiful double flar. Extremely unequal. Lw 
1782. fine w. ; S. r. DIflance 5'' 47''^. Pofition 32° 30^ f.. 

*' With regard to fniall ftars, that become vifible by an increafe of magnifyino' 
power, w€ may furmife, that it is partly owing to the greater darknefs of the 
field of view, arifing from the increafed power, and partly to the real efFeft of- 
the power,; for, though the real diameter of a ftar, notwithilanding it be magnified 
a thoufand times, fliould itill remain fmaller than the minrmum vifibile, yet fince a 
Ibr of thefeventh magnitude maybe feen by the naked eye, we may conclude, that 
the light of a ftar fubtends incomparr^bly a larger angle than its luminous body ; 
and this may be in fuch a, proportion, with very fmall flars, that the power of 
the telefcope fliall be juft fuiFicient to magnify the real diameter fo as to bring it 
with ill the limits of this proportionj wheteby the Har will become vifible. 


of Dotible Stars, 8f ? 


111. 71. Tiaram Cephel prjEcedens. 

Sept. 27, Treble. About 1 1 degree preceding the game ij^ar *\, 
1-82. ill ^ li"s parallel to i and ^Cephei. The two nearefi: 

very unequal. ly. w. ; S. db. Diftance 11 ' -»;:■ 

^' or/'/ 

Politlon 35° 24' f. following. The two farthefl conf).- 
derably unequal. S. db. Dulance iS'^ 37^^^- Pofi- 
tion y^° ^Y II. preceding. The place of \\\t garnet 
jiar^ reduced to the time of Flamsteed's Catalogue, is 
about 7R 21 h. 45'. P.D. 32°!. 

72. Tiaram Cephei pr^ecedens. 

Sept. 27, Double. Within | degree of the foregoing treble 
1782. ftar. Confiderably unequal. L. rw. ; S. pr. Dlflance 
13^^ 7^^^. Pofition 32° o^ n. following. 

73. Fl. 25^ Ceti auftralior et fequens. 

Oft. 2, Double. About | degree f. following the 25th, in a 
1782. line parallel to ^ and r Cetl. Pretty unequal. Diftance 

with 278, \^' 50^"^ Politlon 89^12' f. preceding; 

perhaps a little inaccurate. 

74. Fl. 18^ Pegafi auftralior. Ad oculum finlftrum. 

Oft. 4, Double. About | degree f. preceding the 18, in a 
1782. line parallel to f\ and e Pegafi ; the moft north and largeft 
of two. A little unequal. Both rvv. Diftance 14" 
^()'" full meafure. Pofition 31^ 2>o ^i* following. 
75» Ad Genam Monocerotis. 

Oft. 4, Double. About 1 degree n. of, and a little preceding 
1782. the fix telefcopics in the place of the 12th, in aline 

parallel to the 1 2th Monocerotis and ^ Gemlnorum. 
76* rm quatuor tclefcopicarum,^ Ononis fequentium, penultima. 
Oft. 4, Double. About | degree n. following J", in a line 
1782. parallel to t and i Ononis. Extremely unequal. 

* Phil. Tranf.vol.LXXIII. p. 257. 

M 2 L. 

84 -^^' Herschel's Catalogue 

III, L. r. ; S, d. Diftance with 278, 9^' 12^'\ Polition 
13° 6' n. preceding. 

77. Fl. 65""" Arietis feqiiens adauftrum. 

oa. 9, Double. About I degree f. following the 65th Arie- 
1782. tis, in a line parallel to the Pleiades and e Taurl ; the 

preceding of two. Very unequal L. r. ; S. bluifh. 

Diflance 8'^ 32''^ Pofition yf 18' f. following. 

78. Fl. 13^"" Tauri prascedens ad auftrum. 

06V. 9, Double. About i| degree f. preceding the 13th 
1782. Tauri, in a line parallel to £ Tauri and I Ceti. Nearly 

equal. Both pr. Diflance 7^' 10'''. Pofition 87° 57' 

n. preceding. 

79. e (Fl. 83^) Ceti borealior. 

oa. 13, Double. About f degree n. of e Ceti ; the neareH: of 
1782. three forming an arch. Extremely unequal. L. rw. ; 
S. darkiih red. Diftance with 278, 10'' 48^'^ Pofi- 
tion 45° 1 2^ f. preceding. 

80. <r (Fl. 76'"*) Ceti prsecedens. In finiftro crura. 

oa. 13, Double. Full i| degree preceding 0-, towards t Ceti. 
1782. Extremely unequal. L. rw. ; S. br. Diftance 11^^ 
16^^^. Pofition 22° 24^ n. preceding. 

81. Parvula a ^Lyrae g verfus. 

oa. 19, Double. Above I degree from ^ towards g Lyras. 
1782. Extremely unequal. L. r. ; S. dr. Diflance 9^' 27^^' 
full meafure. Pofition 66° 18^ n. following* 

82. Fl. 41 Aurigae. 

Nov. 6, A pretty double flar. Confiderably unequal. L. w. ; 
1782. S. grey inclining to r. Diflance 8^^ 32^^^. Pofition • 
80° o' n. preceding, 


cj Doubk Stars, 8 r 

III. 83. Fl. 19 Lyncis. 

Nov. 13, Double. A little unequal. L. rw. j S. b\v. Dlf- 
1782. tance 14'' 1 1^^^ Polition 46° 54^ f. preceding. 

84. Fl. 40 Lyncis. In Urfae majoris pede. 

Nov. 13, Double. Very or extremely unequal. L. wr. ; S. r. 
1782. Diftance Y' ii'^^« Pofition 48'' 12' n. preceding. 

85. Fl. 2 Canum Venaticorum. 

Nov. 13, Double. Very unequal. L. r. ; S. bluifh. Dif- 
1782. tance 12^^ 12^^^ Pofition 1 1 ° o^ f. preceding. 

86. Fl. 57 Urfe majoris. 

Nov. 20, Double. The largeft of two ftars. Exceflively un- 
1782. equal. L. w. ; S. a red point without fenfible magni- 
tude. With 227, S. is but jufl vifible, Pofition 75^ 
36^ n. following. 

87. Fl. 59* Urfae majoris borealior. 

Nov. 20, A pretty treble ftar. Near i| degree n. of the 59th, 
1J82. hi a line parallel to ^ and /3 Urfae majoris nearly. The 
two neareft confiderably unequal. L. pr. -, S. r. Dif° 
tance 1 2^^ 30'^^ Pofition o"" o^ preceding. The two 
fartheft very unequal. S. dr. Didance 32^^ 21^'^j 
Pofition 4° o^ n. following. 

88. Fl. ii^ Taurl borealior et fequens. 

Nov. 25, Double. About i degree n. following the nth 
1782. Tauri, towards / Aurigas. Very unequal. L. w. ; S. 
. . pr. Diftance with 278, 13^^ 37^^^ Pofition 89^ 51^ 
n. following. 

89. Ad 63^*" Herculis. In linea per ^ et £ du<£la. 

Nov. 26, Double. About 4 degrees from ^ towards s Herculis, 
1782. iiear the 63d. Very unequal. L. r. ; S. r. Diftance 
J ^// ^^///^ Polition 47° 48^ n. following. 

^6 Mr, Herschel's Catalogue 

III. 90. Fl. 103^ Tauri borealior. 

Nov. 29, Double. About three degrees diredly n. of the 103 
1782. Tauri ; the largeft of three, formhig aa obtufe angle. 
Confiderably unequal. L. r\v. ; S. pr, Diflance wklt 
278, 13'' 6'"''. Pofitlon 64° o^ n. foUowmg. 
^i. Fl. 62^ Arietis borealior et fequens, 
Dec. 23, Double. Near i degree n. followhig the 62d Ari- 
1782. etds, towards g Perfei. Nearly equal. Both dvv. Dif- 
tance ii'^ 17^^^; not very accurate. Pofitioii 12° 24' 
n. preceding or f. followuig. 
^2. f (Fl. ^j"]^"^^ Cancri prascedens ad boream. 
Dec. 28, Double. About i degree n. preceduig | Cancri, in a 
17 82. line parallel to e Leonis and the 41 ft Lyncls; a confi- 
derable ftar. A little unequal. Both rw. Diftance 
8^^ 50^^^ Pofition 6^° 12^ f. preceding. 
9 J. Fl. 1 17 Tauri. 

Dec. 31, Double. Almoft equal. Both fvv. Diftance 12'' 
1782. 12'^^ Pofition 53° 27'' f. following. 
^4^ V (Fl. 7»"^) I^eporis praecedens ad boream. 
Dec. 31, Double. About 1 1 degree n, preceding V Leporis, in 
1782. a line parallel to X and e Orionis; the fecond in that 
line. Equal. Both rw. Diftance 11'' 44^^^ Pofi- 
tion 4° o' f. following or n. preceding. 
-95. V (Fl. 48*"") Eridani praecedens ad auftrum. 
Jan. 2, Double. Near J- degree f> preceding v, in a line from 
.1783. the 51ft continued through the 48th Eridani. Extremely 
unequal. L. rw. ; S. d. and hardly to be feen with 
227. Diftance with 278, 15'^ 21'''; very inaccurate 
©n account of obfcurity. Pofition 9° 1 8^ f» preceding. 

s 96. 

of Double Stars ^ %^j 

in. 96. Fl. lyCraterls. 

Jan. 10, Double. Nearly equal. Both r\v. Dllliance ^'^ 
1783. 46^^^ Pofitlon 64'' zY ^' preceding. 

97. Fl. 54 Hydrx. 

Jan. 10, Double. Very unequal. L. w. ; S. bluidi r. Dif- 
1783. tance i\" \Y'^\ too low for great accuracy.. Pofitioti- 
^8° 1 5^ f. following. 

98. Ad Genam Monocerotis. 

Jan. 13, Double. About f degree f. preceding the mod. f of 
178,3. a clufter of fix teleicopics in the place of the i 2th, in a 
line parallel to the 15th and 12th Monocerotis. Ex- 
eeflively unequal, Pofitlon 6 l° 57' f. preceding.. 

99. Fl. ^'^^ Eridani. 

Jan. 31, Doubk. A very little unequal. L. pr. ; S, rw.. 
1783. Diftance 9'^ ()"\ Pofition 44^" 9^ n. preceding. 
lOQ. Fl. ^i^^"^ Eridani praccedens ad auflrum. 
Jan. 31, Double. About z\ degrees: f. preceding the 55th-. 
1783. Eridani, in a line parallel to Rigel and y Eridani. Ccn- 

fiderably unequal. L. pr. ; S. db. Diftance i \'^ S^"^' 

Pofitioa 16" 24^ f. preceding. 

1 01. ^ Centauri. Fl. 3. 

Jan. 31, Double. Conliderably unequal. L. d\v. ; S. dpr, 
1783. Diftance i \" SS'"'- Pofition 22° o^ f. following. 

102. h (Fl. 29^"") Herculis praecedens ad auflrum. 

Feb. 3, Double. About 1 1 degree f. preceding h Herculis 
1-783. towards e Serpentis ; a fmall flar. Very unequal. Both 
r, Diftance 14^^ z^^\ Pofition 67° i2^n. following. 

103. B (Fl,. 37') Serpentis borealior et fequens. 

March 4, Double. Near two degrees f following £,. in a line 
^^83. parallel to the 13th Serpentis and 10th Serpentarii, 
Very unequal. L. pr. ; S, r. ; but a city Jog,, if I may 


S ? Mr , H £ R »c H E L* s Calalog ue 

III. To call It, probably tinges them too deeply, Diflance 
with 278, 12'' 3V"; with 625, iz" 23"^ Pofitioa 
50° m' Vi. preceding. 

104. Fl. 83^"" Herculis prasccdens. 

JNiar. 26, Double. About I degree preceding the 83 ; the fe- 
1783. cond ftar towards the 79th Herculis. Very unequal. 
L. r. ; S. darker n Dlftance 14''^ 2o''\ Pofition 83^ 
48^ n. preceding. 

105. y (Fl. 12^) Sagittje borealior et prascedens. 

April 7, Double. About 2^ preceding the double ftar V. 106. 
1783. Pretty unequal. L. r. ; S. d. Diftance 14^^29^^^; 

very inaccurate, on account of obfcurity. Pofition 

50° 24^ f. preceding. 

106. Fl. 5 Serpentis. 

May 21, Double. Excefiively unequal. L. rw. ; S. db. Too 
1783* oblbure for mealures. Of the third clafs, far. Pofi- 
fition about 30'' or 40^ n. following. 

107. Congerie Stellularum Sagittarii borealior. 

June 6, Double. Above i \ degree n. of the 20th clufter of 

•1783. ftars of the Connoijfance des l^emps, in a line parallel 

to y S'agittarii and the clufler : the moft fouth of many, 

Confiderably unequal. Diftance with 278, 15'^ lo^^^ 

As accurate as the prifmatic power of the atmofphere, 

which lengthens the flars, will permit. Pofition 54^ 

48'' f^ preceding*. 


* What 1 call the prifmatic power of the atmofphere, of which little notice 
has been taken by allronomers, is that part of its refradive quality whereby it 
ilifperfes the rays of light, and gives a lengthened and coloured imqge of a lucid 
point. It is very vifible in low flaps; Fomalhand, for inftance, affords a beau- 
tiful prifmatic fpedrum. That this power ought not to be overlooked in delicate 
4 and 

ef I)sM$k Starts " '■ 

III. loS. Fn. r9»'» Aqufepra^cedens ad boream* 
July 7, Double. Above | n. preceding the iptli^ in a \m^ 
1783. parallel to jG and f Aquili£. Very unequal. L. r. ;, 
^ S. dr. Diftance 12^' 58^"^ Pofition 58^ 27'' f. fol« 

109. Fl. 19*"* Aqurlas priEcedens ad Boream» 
July 7, Double. About ij degree 11. preceding the 19th, iur' 
1783. aline parallel toe and ^i\quiliE. Pretty unequal. Both 
rw. Diftance 10^^ I3^^^» • Portion 22'^ 6^ n. preceding. 
no. Fl. 77' Cygni borcalior et pr^ecedens. 
Sept. 17, Quadruple. Full | degree n. preceding the 17th, iu 
1783. a line parallel too- and ^j^ Cygni ; a fmall ftar. The 
two neareft extremely unequal. JL. r. ; S. d, Dhlance 
with 625, 13'' 54^''. Poiition 67" 36^ f. following. 
The two largeft a very little unequal. Both r. Dli- 
tance with 278, 25^' S^''- t'oiitioii 40-^ 35'' i^- ^^l' 

and low obfervations, is evident from forae meafurcs I have taken to afceitain its 
quantity. Thus I founcl. May 4, 1783, that the perpendicular diameter of e, 
Flamsteed's aoth Sagittarii, roeafured 16" 9' ', while the horizontal was 8"35'" ; 
which gives 7" 34""' for the prlfmatic effeft : the meafures were taken with 460,. 
near the meridian, and the air remarkably clear. And thouglj this power, which 
depends on the obliquity of the incident ray, diminiflies very faft in greater alti- 
tudes, yet I have found its efFcds perceivable as high, not only as a or 7 Corvi in 
the meridian, but up to Spica Virginia, and even to Regulus. Experiments on 
thefe two latter ftars I made November 20, 1782 ; when Regulus, at the altitude 
of 49", fliewed the purple rather fuller at the bottom of the field of view than 
wheii it was at the upper edge ; which fliews that the prifmatic powers of the edges 
of the eye lens were affifted in one fituation by the power of the atmofphere, bu.t 
counterafted by it in the other. I turned the eye ions in all fituations, to convince 
myfelf that it was not in fault. This experiment explains alio, why a liar is not 
always beft in the center of the Held of view ; a fact 1 have often noticed before I 
knew the caufe. 

V0L. LXXV. N lo^Ying. 

po Mr, Herschel's Caialogui 

III. lowing. The fartheft very unequal. S. d. Pofitlon 
almoft in a line with the two largest. 

1 1 r. e (Fl. 46^) Orionis borealior et fequens. 

Sept. 20, Treble. About ij degree n. following s, towards 
i'783. a Orionis. The two neareft of the third clafs. 

1 1 2. (Fl. 18*"^) Cygni fequens ad auftrum. 

Sept. 22, Double. About i degree f. following S, towards the 
1783. 47th Cygni; a pretty confiderable flar. Equal, or per- 
haps the fouthern ftar the fmalleft. Both pr. Dif- 
tance with 278, 10'' 8"'". Pofition 71° o\ f. fol- 

113. Fl. 27*"' Cygni priEcedens ad auftrum. 

Sept. 23, Quadruple and Sextuple. About | degree f. pre- 
1783. ceding the treble ftar I. 96. ; the middle of three, the 
moft north whereof is the 27th Cygni. In the qua- 
druple or n. preceding fet, the two neareft very une- 
qual. Diftance with 278, ii^' i6^^ Pofition 26° o' 
n. preceding; the two largeft almoft equal. Both r. 
Diftance with 278, 29'^ 27'''. Pofition 5y° iz' n. fol- 
lowing. In the fextuple or f. following fet, the two 
largeft pretty unequal. Both r. Diftance with 278, 
19'^ zo"\ Pofition 27° 36' f. preceding. All the 
other ftars are as fmall as the fmalleft of the quadruple 
fet, and fome of them much fmaller. 
514, Fl. 16"" Monocerotis praecedens ad boream. 

Jan. 23, D-ouble. About J| degree n. preceding the i6th. 

y o u R T 1? 

of Douhk Sliitf, ft 


IV. 45. Ill pectoris crate Ononis. 

Dec. 27, Double. About f degree following i[/, towards 71 
1781. Orionis. Extremely unequal. L. pr. ; S. dr. Dif- 
tance with 278, 20'^ 3'^ Pofition 62° 24.' f. fol- 

46. Fl. 21 :: Geminorum *. 

Dec. 27, Double. A little uaequal. Both pr. Diftancc 

1 78 1, about 25'^ Pofition 

47. Fl. 3 Leonis. 

Feb. 2, Double. Exceflively unequal. L. r. ; S. d. ; not 

1782. vifible with 227. Diftance eftimated with 460, about 
24^^. Pofition a little n. following. A third ftar in 
view. Diftance perhaps 2'. Pofition about 1 5® f. fol- 

48. H (Fl. i*"") Geminorum praecedens ad boream. 

Feb. 6, Quintuple. In the form of a crofs. About f degree 
1782. IL preceding H Geminorum, in a line parallel to the 
65th Orionis and f Tauri ; the middle of three. The 
two nearefl or preceding of the five extremely unequal. 
Diftancc 20'' 57^^^' Pofition 7° 27' f. preceding. The 
laft of the three, in the fhort bar of the crofs, has an 
excefiiively obfcure flar near it of the third clafs. Five 
more in viev%', differently difperfed about the quintuple. 

* The 21 ft and aOth Geminorum are not in the heavens as they are marked in 
Flamsteed's Atlas, fo that it becomes doubtful whether the N'*^!. is right. 

N 2 49- 

Feb. 6, Double. I full: d^egreen. following J Virgmis,, in a 
1782. line' parallel to ^/ and /3' Leonrs. A little unequaL/ L. 
pr. ; S. dr. Diftance 2^' 28'^ Pofition 56'' 30'f. 
"50".' Fl. 17 Virginis. In peflore. ■; 

*Feb. 6, Double. Confiderably unequal. L. w. ; S. bluifli. 
1782. ■ Biftance 20''' l/^^^ Pofition 58^ 21^ n. preceding. 

51. k Virginis :; Fl. 44 :: -}-. In ala auftrina. 

Feb. 6, Double. A flar fouth of three forming an arch, and 
1782. of the fame magnitude with the middle one of the arch. 
Extremely unequal. L. w. ; S. db. Diftance. 22'''' 
17^^^; inaccurate. Pofition 32^ 3^^ i^« following. 

52. * ; Cancri. Fl. 48. In boreali forfice. 

Feb. 8, Double. Confiderably imequal. L. rw. ; S. d. gar- 
1782. net. Diflance 29^^ 54^^^ Pofition 2,9'' 54^ "• preceding;, 

a little inaccurate. 
CJ3. TrGeminorum. Fl. 80. Supra capita. 
Feb. 9, Double. Exceffively unequal. L. garnet ; S. cL 
1782. Diftance with 460, 21^^ 30^^^ Pofition 
Other very fmall flars in view. 

54. ^ (Fl. 4^"") Hydras fequens. 

Feb. II, Double. About I degree following ^, towards ^ 
1782. Hydras. Pretty unequal. Both pr. S. deeper. Dif- 
tance 25^'' 43^"^^ Pofition 59° 24' n. following. 

55. Fl. 41"" Lyncis fequens. In caudasfine. 

Mar. 5, Double. About 3I minutes n. following the 41 ft" 
1782. Lyncis. Extremely unequal. L. r. ; S. dr. Diftance 

15^^ 52^^'; a little inaccurate. Pofition 50° 48^ n, 
preceding; inaccurate. 

t Perhaps the 45th 3 require? fixed inftraments to determine. 

IV. 56. Fl. I S Librae. 

April 3^ Double. The following of two. Extremely uiie- 
1782. q^^''^l« L. r. ; S. b. Diilauce i f 59"^^ Pofitioa 
44° 45^ 11. following. 

57. Fl. 42'™ Ccmie Berenices fequens ad auflriim. 

April 15, Double. About 3 degrees f. following the 42dComis- 
■ 1782. Berenices towards v Bootis ; the vertex of an ilofceles^ 
triangle. Extremely unequal. Diftance with 625^, 
16'^ 42^^''. Pofition 46° 31^ f. preceding. 

58. Fl. 36*"' Comae Berenices priEcedens ad boream. 

April 18, A pretty double ftar. About 2! degrees n. preceding 

i''82. the 36th, in a line parallel to the 42d and 15th Coma^ 

Berenices ; the following of two unequal ilars. A little 

unequal. Both rw. Diftance 15'' 52^"^ Pofition 

67° ^y^ f. preceding. 

5p. Prope a Lyrs. 

May 12, Double. About 2 or 3 minutes f. preceding a Lyraj. 
1782. Very unequal. Bothd. Diftance with 278, 22^^ 20^^^ 
Polition 2^° 57^ n. preceding. Pofition of the largeft 
with regard to a, Lyra^ 59° 12^ f. preceding, 
'60. Fl. 4="" Urfae majoris fequens ad boream. 
June 6, Double. Near i degree n following the 4th, in ar 
1782. Ihie parallel to and h Urfae majoris; a pretty larg^ 
ftar. Extremely unequal. L. r. ; S. d. Diftance 
near 30'''' ; but too obfcure for meafures. 
t)i. ^(Fl. 7^) Coron^eauftralior et praecedens. 
July 18, Double. Near | degree f. preceding f, towards ^ 
1782. Coronae bor. Nearly equal. Both pr. Diftance 
16'^ 46'^^. Pofition 4° 57' n» following,. 


94 ^^> Herschel's Catalogue 

IV. 62. T (Fl. 22^) Hercnlis anftralior et fequens. 
Aug. II, Double. About 2| degrees f. following r Herculls, 
1^82. ill a line parallel to f and y Draconis ; a confiderable 

ftar. Very or extremely unequal. L. w, ; S. br. 

Diftance 16'^ S^'^^- Pofition 72° I5^f. preceding. 

63. Fl. 42 Herculls. Dextrum fupra genu. 

Aug, IT, Double. V^ery unequal. L. r. ; S. rw. Diflancc 
1782. 21^^ 31^'^ Pofition 3^" 42^ f. following. 

64. Prope q (Fl. 12^'") Perfei. 

Aug. 20, Double. Within a few minutes of q Perfei. Pretty 
1782. unequal. Both pr. ; but S. a little darker. Diftance 
^l'^ 59^^^ Pofition ^'j'^ 57^ f. preceding. 
6^. Prope Fl. :^^"' Cafliopeias- 

Aug. 25, Double. Within 1,0 minutes of the 3d Caffiopeis. 
1782. Very unequal. L. pr. ; S. r. Diftance 20^^46^^'; 
very inaccurate. Pofition 41° 12^ f. following. 

66. (Fl. "^"^^"^^ Caffiopeias piraecedens. 

Aug. 28, Double. About 1 1 degree f. of, and a little pre- 
1782. ceding^, in a line from 5 continued through Q Caffio- 
peias. Extremely unequal. L. r. ; S. db. Diftance 
24'^ 2^^'; very inaccurate. Pofition 13° 12. n. fol- 
lowing ; inaccurate. 

67. t Fl. 40 et 41 Draconis. 

Aug. 29, Double. A little unequal. L. rw. ; S, pr. Dif* 

1782. tance 20^ 39^''^ mean meafure; very accurate. Pofition 

^f I5^f. preceding*. There is a third, mach fmallcr 

flar. Diftance 3' 16'' ^i''\ Pofition about 30° f. 

following . 

♦ The proper motion of one of thefe ftars at lead fince the time of FlaaT- 

STEED is evident, as he gives us their difference in J9^ 2', and in PD 3' 5''. Pofi- 
tion f. preceding. Hence we have the hypotcnufe or diftance above 3' 40", 
inftead of 20" 39'" ; and the angle 86° 17' inilead of 35° 15'. 

4 68. 

of Double Stars. ^^ 

IV. 68. Fl. 77 Plfcium. In lini flexii. 

Sept. 3, Double. A little unequal. L. wr. ; S. pr. Dif- 
1782. tance 29^' 36^^^ Pofition 4"^ 48^ n. following. In both 
meafures the weather too windy for accuracy. 

69. Fl. 23"" Andromedas prascedens. 

Sept. 4, Double. Full 1 1 degree preceding the 23d, in aline 

1782. parallel to v and t Andromedas. Of two double ftars 

in the finder the largeft of the preceding fet. Very 

unequal. L. r. ; S. d. Diftance with 278, 21^^ 58^^^ 

Poiition 70° 36' n. preceding. 

70. Fl. 51 Pifcium. In aullrino lino. 

Sept. 4, Double. Very unequal. L. rw. ; S. d. Diftance 
1782. with 278, 22^^ 29^^^ Pofition 0° 36^ n. following. 

71. * Capricorni. Fl. 12. Trium in roflro auflrina. 

Sept. 5, Double. Pretty unequal. Both rw. Diflance 23,^' 
1782. 30^'^^. Pofition 30^45^ f. preceding. 

72. Fl. ^§^ Perfei borealior. 

Sept. 7, Double. About | degree n. of the 55th Perfei; of 
1782. three in a line the moft north. Pretty unequal. L^ 

rw. ; S. pr. Dillance with 278, 16^^51/^'. Pofition* 

27"" 24' n. following. 

73. In Conftellatione Camelopardali. 

Sept. 7, Double. Between Fl. 2 and 8 Cam. ; the fmallefl: 
1782. of two that are within | degree of each other. Confix 

derably unequal. Diftance 19/^ 32.^^^ Pofition 85° a- 

f. preceding. 

74. ^ (Fl. 68^'") Tauri fequens ad boream. 

Sept. 7, Double* Near | degree n.. following^, towards^;. 
1782. Tauri. Very unequal. L. pr. ; S. r. Diftance 1.6^'' 
31'^^ Pofition 25° 45' n, following. 


«>i5" Jfr. Herschei/s Gi^^%?^f 

IV. 75. ^ (Fl. 66""^) Tauri fequeus. 

..iiept. 7» Double. About 1 1 degree n. following r, in a lioe 
17-82. parallel to jw Tauri and the 9th Orionis. Very une- 
qual. L. r. ; S. dr. Diftance 22'^ 25^^^' Po^^tioii 
6 1° 36M'. following. 
*76. Fl. 13^"" Ceti praecedens ad auftrum. 
Sept. 9, Double. About i degree f. preceding the i3tlT^ 
X782. towards the 8th Cetl. Confiderably unequal. L. rw. ; 
S. br. Diftance with 278, 18'^ 55''''. Pofition 40° 24'' 
n. following. 

77. Fl. 37^ Ceti borealior. In dorfo. 

Sept. 22, Double. About J degree n. preceding the 37th, 

1782. towards the 36th Ceti. Very unequal. L. r. ; S. dr. 

Diftance 19'^ 6^^\ Polition 63° 24^11. preceding. 

78. ;j (Fl. 3'"') Cephei praecedens. 

Sept. 27» Double. About 1 1 degree preceding ;?, in a line 
i^Sz. from 6 continued through tj Cephei. Very unequal. 
L. r. ; S. d. Diftance ig'' 32^^''. Pofition 40° 36' n, 

79. I/, Cephei. Fl. 13. Ad coronam. 

Sept. 27, Double. A little unequal. L. \V. ; S. rw. Dif* 
1782. tance 21^^ 3^'^ Pofition 7 7^" 48^ f. preceding. 
So. (3 (Fl. 2^) Canls majoris borealior. 

Sept. 30, Double. About 1 1 degree n. of /3 Canis majoris 
1782. towards the nth Monocerotis ; the moft n. of two. 
Confiderably unequal. Diftance 17^^ 59'^''* difficult 
to take, and perhaps a little inaccurate. Fofition 2° 24'' 
n. following. 
Si. 1/ Canis majoris. Fl. 6. In dextro genu. 
Sept. 30, Double. Confiderably unequal. L. f w. ; S. pr. Difl. 
1782, 1 8'" 1 9'''. Poiition very near diredly preceding. 

I §2. 

cj Double S/ars, ^ §"/ 

IV. 82. Prope Fl» i6»"'Cephei. In cingiilo. 
Sept. 30, Double. ■ Above I degree following the i6thCephei, 
1782. ill ^ li'ie parallel to /3 and « Caffiopeiae. Confiderably 
unequal. L. orange. S. r. Diftaiice' 28^' ^'^\ Poli- 
tion 79° 18^ n. preceding. 
8 J. Fl. 26 Ceti. Supra dorfum. 
oa. 2, Double. Very unequal. L. rw. S. db. Diftance 
1782. 17^^ 2'^^ mean mealure. Poiition i^'^ ^6' i. preceding. 

84. ;« Orionis. FL.23 In crate pe£loris 

06V. 2, Double. Confiderably iwiequal. L. w. ; S. pr* 
1782. Diftancc with 278, 26^' g'^\ Pofition 59.^ 33 ^' fol- 

85. Fl. ultima Lacertae. 

06t. 4, Treble. The two nearefl: extremely unequal. L. 

' 1782. • fw. ; S. d. Diflance 20^' 27'^^ Pofition 79^" 53^ n. 

preceding. The next very unequal ; S. r . Diftancc 

54^^57^'^; inaccurate. Pofition 44° 24' n. following, 

A fourth and fifth ftar in view. 

86. Fl. 8 Lacertae. In media cauda. 

oa. 4, Quadruple. The two largeft and neareft a little une- 
1782. qual. Both rw. Diftance 17^^ i^'^\ Pofition 84° 

30^ f. preceding. The two next very unequal, of the 

fourth clafs. The two remaining confiderably unequal, 

of the fifth clafs. They form an arch. 
Byv}e (Fl. 29'"') Orionis prascedens. In finiftro calcaneo. 
oa. 4, Double. About i degree preceding e, in a line pa* 
1782. rallel to a- Orionis and b Eridani nearly. Confiderably 

unequal. Both pr. Diftance 29^'' i8''^ Pofition 8 2^* 
r, ni 18' n. following. 

Vol, LXXV. O 88. 

9? Mr. Herschel's Catalogue 

IV. 88. Fi.. 7 Tauri. In dorfo. 

c&. 9, Double, Very unequal. L. pr. ; S. dr. Diftancc 
1782. 19'^ S'^^^^* Pofition 23° 15^ n. following. 

89. E telefcopicis caudam Arletis fequentlbus. 

oa 9, Double. The vertex of an ifofceles triangle follow- 
1782. ing T Arletis; a very fmall ftar. Very unequal, li,' 

r.^ S. d. Diftance with 278, 20'^ 3'''^ Pofitiou 

62° o' f. following. 

90. Ad Fl. 18*"* Urfae minoris. Prope edu6lionem caudae. 

oa. 12, Double. The largefl: of fix or feven ftars, and moil; 
1782. fouth of a triangle formed by three of them. A little 

unequal. L. pr. ; S. deeper pr. Diftance 2^(>^^ z\"\ 

Pofition 3° 1 2' n. following. 

91. Fl. 2 Navis. 

oa. 12, A pretty double ftar. A little unequal. L. w. ; S. 
1782. w. inclining to r. Diftance i']" 23'^'. Pofition 69** 
12' n. preceding. 

92. /3 inter et ^ Delphini. 

oa. i-]. Treble. Between /3 and X,-> hut nearer to /9 Delphin\. 
1782. All three nearly equal. AH ,wr. Diftance of the tWQ 

neareft with 278, zi" 2)2>" ' Pp^iUou 18"* 27' n, pre^, 


93. E (Fl. 4*™) Lyrae fequens. . \, ; 

oa. 19, Double. About 3 degrees following! «, in a line pa« 
1782. rallel to ex. and 5 Lyrae ; the largeft of two. Extremely 

unequal. L. w. ; S. r. Diftance 19'^ 50''^ PofitioaL > 

24° o^ f. preceding. 

94. E borealibus telefcopicis jQL.yraE prascedentibus. 

oa. 19, Double. Full 2 degrees n. preceding /S Lyras, in a 
3782- line parallel to the 18th and e ; the fixth telefcopic ftar. 


tf Double Stars, 99 

IV; Confiderably unequal. L. rw.; S. pr, Diftancc 22" 
$'^'^\ Pofitlon 5° 24' n. following. 

95. Fl. 25"" Monocerotis priccedens. 

oa. 19, Quadruple. About 2I degrees preceding, and a little 
1782. n. of the 25th Monocerotis. Two large ftars always to 
be feen, and two more only vlfible in dark nights. The 
nearefl: which is that to the fmallefl: of the two large 
ones, extremely unequal. Diftance 20'' ^l' ' ' Pofi- 
tioii following. 

96. Fl. 25*" Monocerotis fequens. In latere. 

oa. 19, Double. About i| n. following the 25th, in a line 
1782. parallel to the 2ifl: Monocerotis and Procyon. A little 

unequal. Both dr. Diflancc. 18'^ ^9^^^* Pofitiou 

24*^0' f. preceding. 

97. Fl. 29 Monocerotis. In femore. 

Odi. 19, Double. Extremely unequal. L. wr. ; S. d. Dif^ 
1782. tance 29^^ 54^'^ Pofition 15'' 12'' f. following. Six 
more in view, 

98. oi (Fl. 58^"") Orionis ad aufbrum praeiens. 

Oft. 29, Double. About | degree preceding a, towards ^ 
1782. Ononis. Equal. Both r. Diflance 17^' 59^^^; a little 

99. Duarum telefcopicarum ^ Sagittas ad auftrum fequentium 

Nov. 6, Treble. Of a trapezium, confining of this treble 
1782. ftar, J", ^, and the 9th Sagitt^, it is the corner oppofite 
to ^; the neareft to f of two. The two neareft very 
unequal. L. pr. ; S. db. Diftance 21'^ 22'^^; Inac- 
curate. Pofition 0° o' following. The two largefl a 
little unequal ; of the fifth clafs. Pofitloa 10^ 36' f. 

O 2 100*. 

Joo Mr, Her scH el's Catalogue 

IV. ICO. % Sagittae. Fl. 13. Infra mediam arundinem. 

Nov. 6, Treble. The largeO; of three. The two iiearert: 

1782. equal. Both r. Dii1:ance23''' 2'"^ Pofition 10° 12^ f. 

precedhig. The third is a large fliar. Diftance above 

I minute. Pofitioii about 10° or 15° n. preceding the 

other two. 

10 1. <p (Fl. 24*) Auriga borealior et pra?cedens. 

Nov. 6, Double. Near % degree n. preceding (p, in a line 
1782. parallel to the 2 1 ft and 8th Auriga^. Pretty unequaL 

L. rw. S. bluifh. Diftance 25'^ 2.<^"\ Poiitioix 

76° o' n. preceding. 

102. Fl. _^c^ Auriga. 

Nov. 6, Double. The apex of an ifofceles triangle. Very 
1782. or extremely unequal. L. rw. ; S. Diftance 

23'^ 30^^^ Position 50° 3' f. preceding;. 

103. Fl. 77^'" Draconis fequituri 

Nov. 13, Double. Near \ degree following the 77th Dra- 
1782. conis, in a line parallel to x, Cephei and the 76th Dra- 
conis nearly ; of a re£langular triangle the leg neareft: 
the 77 th. Very unequaL L. r. ; S. bluiih r. Dif- 
tance 22^' o^^'^ Poiition 45° 48^ n.. following. 

104. Inter y et 55*'" Andromedas. 

Nov. 13, Double. A little more than i degree n. following 
J78». the 55th Andromedae, in a line parallel to /3 Trianguli 
and Algol. Confiderably unequal. L. r. ; S. d. Dif- 
tance with 278, \%" ^f'\ Pofition 22° 33' n. fol- 

105. ^Corvi. Fl, 7. Duarum in ala fequente prscedens. 
Nov. 13, Double. Extremely unequal. L. w. ; S. r. Dif- 

1782. taace 23'^ ^o^'\ Pofition 54° o^ f, preceding, , 


of Double Sfcirs, ' lo*)^ 

IV. io6. a. (Fl» 50"^) Urfae majoris fequens adborcam. 

Nov. 17, Double. About 1 1 degree, n.. following a^ in a liner 

1782. parallel to /3 Urfys et ;c Draconis ; the lafl: oi three in a 

row. Extremely unequah Both r. Dlflance 18''' 

55^^^; verj inaccurate. Pofition 44"* 33^ f. fallowing. 

A third Imall flar in view. 

107. Fl. 79^ Pegafi auflrahor et priecedens. 

Nov. 20, Double. About | degree f. preceding the 79tht, 
1782. towards r Pegafi; at the center of a trefoil. Very 

unequal. L. r. ; S. d. , Diftauce with 278, 26'^l2'/. 

Polition 50° 21' n. following. 

108. Fl. 69* Urfae majoris auilralior. r 

Nov. 20, Double. Near 2 degrees f. of the 69th, .tov/ards 
1782. the 63d^Urfa2 majoris. A very little unequal. Both r. 

Diftance 19''' 15'^^ ; very inaccurate. Pofition 10° 12'^ 

n. following. . 

109. Fl. 62Tauri.. 

Nov. 25, Double. Coniiderably unequal. L. w..; S. r. Dif- 
1782. tauce 28''' ^'^'. Pofition 21° 12' n. preceding. 

no. j6 (Fl. 112^) Tauri berealior et fequens.: 

Pec. 24, Double. About i| degree n. following /G Tauri>, 

1782. towards 6 Aurigas ; the fecond in that diredlion. Very 

•unequal. L. r. ; S. d. Diftance. id^^ i^^\ Pofition 

rri ;v. 7-4° 54' "• pi-eeeding. 

111. Fju. 54 Cancfi. 

Dec. aS, Double. A little unequal. Both rw. S. a little 

1782. darker. Distance 17'^ 14'^% Pofition 29° a' £ fol 
lowing. , r ; 

112. -y (Fl. 15^"')' Crateris fequens ad borearru 

Jan. i^ Double. About I degree n.. following y Craterls, in 

1783. a line parallel to I Corvi and Spica. Equah Both pr^ 


lOi Mr, HersChel*s Catalogue 

IV. Dlftance 26'^ 15'"'; too low for accuracy. Pofitloti 
58° 42^ n. preceding or f. following. 

113. Fl. 61^ Cygni borealior et praecedens. 
Jan. 6, Double. About 1 1 degree n. preceding the 6 1 ft, in 

-1783; a line parallel to u and a Cygni. Very or extremely 
unequal. L. r.; S. db. Diftance with 278, i 7'' 30''^ 
Pofition 28° 24' n. preceding. A third ftar in view. 

,114. t (Fl. 12') Virginia auftralior. 

vjam 8, Double, About ij degree f. of f Virginis. Very 
1783. unequal. L. pr. ; S. d, Diftance 23'^ 21^^''. Pofitioii 
15° 54^ n. preceding. 

1 15. (p (Fl. 1 1*"") HercuUs praecedens ad auftrum. 
Jan. !o, Double. About 2| degrees f. of, and a little pre- 
J783. ceding ^, in a line parallel to ij and ^ Herculis; the 
largeft of three or four. Extremely unequal. L. r. ; 
S. b. Diftance 20''' 54'^^ Polition 43° 48^ n. fol- 

116*. Fl, 83*" Pegafi fequens ad boream. 

Jan. 13, Double. Equal. Both w. Diftance 28'' 59^^^* 

i;83. Pofition 68° 21^ Mr. C. Mayer, in 1777, fettled its 
place j^o^^ 52^ ^^^^ in time, and 20* 17' ^^'^ in de- 
clination N. 

117. Fl, 42^ Eridani auftralior. 

Jan. 31, Double, About i| degree f. of the 42d Eridani, in 
1783. a line parallel to Rigel and jt* Leporis; the moft foutl'i 
and following of three. Very unequal. L. r. ; S. r* 
Diftance 19^^ 32^^^* Pofition 31° 48' f. preceding. 

118, < (Fl. 48"^) Cancri fequen?, 

Feb. 5, Double. Full | degree following the 48th, in a line 

1783. parallel to § Cancri and e Leonis; a very fmall ftar, 

next to two more which are nearer to t, A little une- 

7 qual. 

of D'ouhle Stan, 102 

IV. qual. Diflance 24^'' (i''\ Pofition about 23° n. fol- 


1 19. i (Fl. bS""*) Virginis prsecedens ad auftrum. 

Feb. 7, Double. About 1 degree f. preceding the 68th, in a 
1783. line parallel to the 99th and » Virginis. Extremely 

unequal. Diflance z\'' 49 "^^ Pofition 36° 54' n. 


120. Fl. 82*"" Pifcium fequens ad boream. 

Feb. 37, Double. About | degree n. following the 82d Plf- 
1783. cium, in a line parallel to a and /Q Trianguli ; the 

largeft of two. Confiderably unequal. L, rw. \ S pr. 

Diftaiice i*^" \()'^\ Pofition 21° o^ f. preceding. A 

third flar in view. 

121. c- Scorpii Fl. 20. pr^ecedens trium lucidarumin corpore. 
M?r. I, Double. Very unequal. L. whitifh ; S. r. DIf- 

178^. tance 21^^40^'''. Pofition o*' o^ (or perhaps 1°) n. pre- 
ceding. ' 

122. Fl, 32* Ophiuchi borealioret praecedehs. 

Mar. 7, Double. Near i degree n. of, and a little preceding 
1783. the 32d Ophiuchi, in a line parallel to a, and -n Herculis. 

Very unequal. DiJftance 21:''' 3''^^, Pofition 25° 3 f. 


123. Fl. 19 Ophiuchi. 

Mar. 9, Double. The mtjfl fouth of two. Very unequal- 
3783. L. pr.; S. d. Diftaiice 20^^ ^f^\ Pofition 3° 9'' f, 

124. ^ (Fl. 4?"") Ophiuchi prsecedens ad auflrum. • ' -c^^ 
Mar. 24, Double. About I degree preceding and a little f. of ip, 

J 783. in a line parallel to ij^' Ophiuchi and &> Scorpii; in the 
bafe of a triangle, the neareft to x]/. A little unequal. 

% Both 

*3^4 ^^« Herschel's Catalogue 

!¥,,_ Both inclining to r. . Diftance 15'^ 14.''', Pofitioii^ 
62^ 54^ n. following. 

125. Fl. 29 Camelopardaii. 

April 2, Double. Very unequal. •. L. pr. ; -S. d. Diftance' 
1783. 22'' 2 6^''-;,' very inaccurate. Pofitioiv 47^ 36'. f. fot* 
,fi j^ lowing; a little iji accurate. 

126. A (Pl. 22*) Cephei borealior et praecedens. 

April 20, Double. Lefs than- 1 "degree n. preceding A, in a " 
1^.83. line almoft parallel to I and f Cephei; a confiderable - 
gff^j ^fiAi". . A little unequal. Bothdw. Diftance 18''' 50'^^ 
PofitIon45'^ 39' n. preceding. 
3 27 t« A (Fl. 16*™) Aqullse fequens ad boream. 
May 21, Double. About 2§ degrees n, following the farthefl: 
5783. of two which are about if degree from x, in a line- ' 
parallel to X and ^ Aquilae. Very unequal. L. rw. ;'* 
S. dr. Diftance 1 7^^ 14^^^; more exad with 932, 15^'' 
S'^'^\ Pofition 69° 54^* n. preceding. Mr. Pigott, 
who favoured me with it, gives its place J^ iZ^~i 
^2.^i =t. Declination i" o^ S. - 
I2S. y (Fl. 57*""), Andromedae praecedens ad auflrum. 
juiy.28, Double. About i| degree f. preceding y almoil: 
3783. towards (3 Andromedas; moreexa£l towards o-Pifcium; 
one not in a row of ftars which are near that place. 
._;Confiderably unequal. L. pr. ; S. dr. Diftance 15'' 
": ■ 42^'^ Pofition 24° 12' n. following. 
129. Fl. 59 Andromedae. 

July 28, Double. A little unequal. ' L. rw. ; S. pr. Difr ^ 
17^. tance 15''. l/-.^; Pofition ^^^^ 9^ n. following. A third 
Of: J &H ii^ view ^b^ut, 58° or iSp° f, preceding* 
.L:f;p3irj '"'-f A .\{; cj '• ■; " ■ ^'' . 
dvM I IJO. 

cf Double Stars, 105 

IV. 130. VI (Fl. 99*) Pifcium borealior et fequens. 
Aug. 2, Double. About i| degree 11. of, and a little fol- 
1783. lowing y\ Pifcium, in a line parallel to /3 Arietis and /3 
Trianguli ; the lafl: of four in a crooked row. Very- 
unequal. L. r. ; S. darker r. Diftance with 278, 
\<^" \^'"» Pofition 62° 15' n. following. 

13 1. Fl. 100 Pifcium. 

Aug. 2, Double. Pretty unequal. L. pr. ; S. r. Diftancc 
1783. 15^^ S"^'" * Pofition 5° o' n. following. 

132. Fl. 46*"" Aquilae fequens ad boream. 

Aug. 6, Double. About \ degree n. following 46 Aquilae, in 
1783. a line parallel to ot. and y Sagittas. Very unequal. 

L. r. ; S. db. Diftance zz" 44'^'. Pofitioii 41° 24^ 

n. preceding. 


V. 52. Secunda a v Geminorum jt* verfus. 
Dec. 27, Double. The fecond ftar from v towards y. Gemino- 
,781. rum. Pretty unequal. L. r. ; S. b. Diftance OiS' ' 

53. p Geminorum. Fl. (i'}^. In Inguine fequentls H'. 

Dec. 27, Double. The brighteft of two. Extremely une- 
1781. qual. L. pr. ;S. d. Diftance 44''' 1 5'^^. 

54. 5 Hydrae. Fl. 22. Duarvim in edu6lione cervlcis fequens. 
Jan. 20, Double. Exceffively unequal. L. w. ; S. a point. 
,782. Diftance near i minute, too obfcure for meafures, and 

Vol. LXXV. P not 

io6 Mr. He-r^chel\ Catalogue 

V. not vifible till after having looked a good while at §), 

PofitioQ about y^° f. following. 
^^. Ad Fi. 1 2^™ Geminorum. In pede Jl' praecedentis liniflro. 
Jan. 30, Treble. A fmall ftar near the place of the 12th 
1782. Geminorum. The two neareft a little unequal. Dif- 
tance lefs than i\ 

56. Fl. 15 Geminorum. Dextrum prioris Jl^ pedem attingens* 
Jan. 30, Double. Conliderably or very unequal. L. r. ; S. d, 
1782. Diftance 32^^ 39^^^* Pofition near 60'' f. preceding. 

57. Fl. 9^ Orionis borealior et fequens. In exuviarum 

Feb. 4, Treble. More than i degree n. following the pth 
1782. Orionis, towards the 1 13th Tauri ; the largeft of two. 
The two neareft confiderably unequal. L. rw. ; S- rw* 
Diftance with 278, 36^' 26'^^ Pofition ^f 36'. The 
farthefl very unequal. S. r. Diftance Vth Clafs. Pq- 
iition following. 

58. Fl. y Leonis. Supra pedem borealem anterlorem. 

Feb. 4, Double. Very unequal. L. rw. ; S. r. Diftance 
1782. 42^^ 25'^^ Pofition 8° 36' n. following. 
^g, ^ Cancri. Fl. 31. In quadrilatero circa Nubem. 
Feb. 6, Double. Extremely unequal. L. r. ; S. d. Dif^ 
1782. tance 44^^ 5^'^^* Pofition n. following* 

60. (Fl. 95^"") Leonis praecedens ; ad caudam. 

, Feb. 9, Double. Near | degree f. preceding the 95th, in z 
,782. line parallel to jS and ^ Leonis. Very unequal. L. rw. ;. 
S. d. Diflance 37'' 15'"'^ Pofition 70° 48' n. fol- 

61. Fl. 81 Leonis. In clune. 

Feb. 9, Double. Extremely -unequal, L. rw. ; S. r. Dif- 
1782, tance 57^^ 23'''^ Pofition 

2 » 62, 

of Double Stars, lo^ 

V. 62. Fl. ^"^ Leonis. E poflerlores pedes prxcedentibus. 
Feb. II, 1782. Double. Very unequal. Diftance 33'^ 16 '^^ 
6^, Fl. 25 Leonis. In inhmo pe^lore. 

feb. 17, Double. The largefl of two. Extremely unequal. 
1782. L. pr, ; S. d. Dlftance 52'^ 46^^^ Pofition 
64. Fl. 43^' Leonis auftralior. Ad liniftrum anteriorem cu- 

Feb. 17, Double. Near r degree f. of the 43d, in a linepa- 
1782. rallel to ^ and a Leonis. Extremely unequal. L. w. 
inclining to r. ; S. db. Diflance 59^^ 40^^^. Pofition 
6^. Secunda ad tt Canis majoris. Fl. 17. Li pe6lore. 
JMar. 3, Treble. The two nearefl very unequal. L. rw. ; 
1782. S. r. Diftance 44^^ 52^^^ Pofition 64^ 12^ f. following. 
The two tarthell: very or extremely unequal. S. r. 
Diflance Vth Clafs. Pofition about 85° f. preceding. 
The three liars form a redangle, the hypotenufe of 
which contains the largeft and fmalleft. 

66. f (Fl. 63^) Geminorum borealior. 

Mar. 3, Double. About | degree n. of, and a little prc- 
1782. ceding />, in a line parallel to u and a, Geminorum. 

Very unequal. L. pr. ; S. d. Diftance 34'' 39^"' 

Poiition 1° or 2° n. preceding. 

67. Pollucem prope. In capite fequentls If'. 

Mar. 3, Double. Near i degree n. following /3, in a line 
J7S2. from (J continued through /3 Geminorum nearly; the 

farthefi: and fmallefl of three. Confiderably unequal. 

L. r. ; S, dr. Diftance 47^^ sY'^^ 

68. Fl. 75*"^^ Leonis prsecedens ad boream. 

Mar. 5, Treble. One of two n. preceding the 75th, m a 
?782. line parallel to the 84th and 59th Leonis, The two 

P 2 neareft 

loS Mr. Herschel's Catalogue 

V. iieareft very unequal. Diftance 54'^ ^f\ The far- 

thefl extremely unequal. 

69. Fl. n LeoQis minoris. In extreme anteriore pede. 

Mar. 12, Double. The largefl of two. Extremely unequal. 
1782. L. pr. ; S. r. Diftance 58^' i^'". 

70. Fl. 2^'" Bootis prj::£cedensad boream. 

Apiil5, Double Near 3 degrees n. preceding the 2d Bootis* 

1782. towards the 43d Comx^ Ber. ; the preceding of three in 

a line parallel to » and t] Bootis. A little unequal. 

L. r. ; S. darker r. Diilance 56'' S^ "' Pohtion 7° o' 

f. preceding. 

71. Prope y (Fl. 24^'") Gemlnorum. 

April 15, Double. Three or four minutes n. preceding 7 Ge- 
1782. minorum. Of the Vth Clafs. More in view. 

72. -f* wHerculis. Fl. 36 6137. In finiftro Serpentarii brachio. 
May 18, Double. A little unequal. L. bluifh w. S. reddifh 
1782. w. Diftance 59^^ ^^"\ Politioii 36° ^Y f. pre- 
ceding *. 

73. T Urfae majorls. Fl. 14. Duarum in collo praecedens. 
June II, Double. Extremely unequal. L. w. ; S. d. Dif- 
1782. tance 54'' 46^'^ Pofition about 45° n. following. 

74. S (Fl. 72'') Serpentarii borealior. 

June 16, Double. More than i degree n. following the 56th 
1782. double ftar of the Illd Clafs ; nearly in a line parallel to 

the62dand 72d Serpentarii, Very unequal. L. rw. ; 

S. r. Di{l:ance40^' 54^^^ Pofition 39° 15^; inaccurate. 

* One of thefe ftars, at leafl, feems to have changed its place fince the time 
of Flamsteed, who makes their difference in R.A, 45", and in P.D, 1' 35"» 
Pofition f. preceding; hence we have the hypotenufe or diftance above i'45"» 
inftead of 59" 59'", and pofition 69° 46' inftead of 36° 57'. 

7 75- 

of Double Si{irs. i go 

V. y^. E telefcGplcis e Coronas borealis fequentlbus. 

July 18, Double. About i degree f. following ?, in a line 
1782. parallel to ^ and t Coronae ; the preceding of three 
forming an arch. Extremely unequal. L. r. ; S. 
darker r. Diftance 41'' 12'''. Polition 16" o'f. fol- 

76. jG i\qLiarii. Fl. 22. In finiftro humero. 

July 20, Double. Exceffively unequal. !L. w. ; S. d. Dif- 
1782. tance about 53'' it"^ i very inaccurate. Pofition 

55° 48; 

77. ^/(Fl. 43^) Sagittarii borealior et fequens. 

Aug. 4, Double. A few minutes n. following the 43d, in a 
1782. line parallel to and tt Sagittarii ; the nearefl of two. 
Extremely unequal. L. w. ; S. d. Diftance with 278, 
36'' ^"'. Pofition 78° 45' f. following. 

78. f Sagittarii. Fl. 38. Trium fuper coftis fub axilla. 

Aug. 4, Double. Extremely unequal. L, r. ; S. d. Dif- 
1782. tance VthClafs. Pofition 28° 6' n. preceding. A 

third ftar. Diftance about four times as f^r as the 

former. Pofition alfo n. preceding. 

79. Fl. 9 :: Caffiopeias. 

Aug. 25, Double. Of two in a line parallel to /G and y, that 
1782. towards y Caffiopeiae. Very unequal. L. w. ; S. pr. 
Diftance 52'^ 39"^' Pofition 50° 36' n. preceding. 

80. T Aquarii. Fl. 69. Duarum in dextra tibia borealior. 
Aug. 28, Double. Very unequal. L. rw. ; S. d. Diilancc 

1782. 36'^ ^f> Pofition 19" 54' f. following. 

81. Fl. 35 :: Caffiopeiae. In finiftro crure. 

Aug. 28, Double. Confiderably unequal. L. rw. ; S. br. 
jj32. Diftance 42'^ ^S'"* Pofition 85° 12' n, following. 


1 ro Mr. Her sen el's Catalogue 

V. 82. V (Fl. 25^"^) Caffiopeiifi prcecedens. ' In finiftra manii, 
Au?-. 2S, Double. Near | decree u. precedino; f, in a line Da-« 

ij82. raliel to a. and /3 CaPiiopeia?. Nearly equal. Both pr, 
Dilrance 43'' 26'''. Poiitlon 7° 48' n. following. 
8j. ip Cadiopeiae. Fl. 36. Sub pede finiflro. 
Aug. 28, Double. Very unequal. L. pr. ; S. r. Dlftance 

1782. 2)?>' '^S' ' ' Politioii 10° 12' f. following. 

84. Fl. 47 :: Caffiopeiai. Ex obfourioribus infra pedes. 

Aug. 29, Double. The largeft of three forming a rectangular 
1782. triangle on, or near, the place of the 47th CaffiopeicE. A 

little unequal. L. rw. ; S. pr. Diftance 50''' S^'"* 

Poiition 3° 33'' n. preceding. 

85. ^ (Fl, 27^) borealior et pra^cedens. In dextro brachio. 
Aug. 29, Double. About | degree n. preceding a Andromedae 

1782. ^ verfus. Very unequal. L. rw. ; S. r. Diflance 30'' 
^Y^' * Pofition 79° 24' n. following. 

86. Fl. 1 2 Urfjc minoris. 

Sept 4, Treble. Extremely unequal. All three r. The 
1782. neareft is the fmalleft. Poiition fome degrees f. follow- 
ing. The fartheft alfo fouth, but more following. 

87. (T Capricorni. Fl. 7. Sub oculo dextro. 

Sept. 5, Double. Very, or almoft extremely unequal. L. r. ; 
■1782. S. d. bluifn. Diflance 50^^ ^i"\ Poiition 85° 12' f* 

88. ^ (Fl. 1 5^) Aurigae borealior. In finlflra manu. 

Sept. 5, Double. About 3' or 4^ n. following the 15th Au- 
.5782. rigae. Very unequal. Diitance 34'^ 15^^^, mean mea- 
fure. Pofition 54"^ 6' f. preceding. 


of Double Stars. . i t i 

V. 89. 5 AurigiE. Fl. 37. In dextrocarpo. 
Sept. 5, Double. Exceflively unequal. L. fine w. ; S rcd- 
1782. dllh. Diftance with 460, ^^^^ iZ'^\ narrow mcafure. 
Pofitlon i6°o''n. preceding. A third ilar in view, 
po. V Aurigs". Fl. 32. In dextri brachii ancone. 
Sept. 5, Double. Exceffively unequal. L. orange w. ; S. r. 
1782. Diftance 53^^ 43'^^ Polition 61'' 48^ f. preceding. S. 
not vitible till after fome ip.inutes attention. 

91. /3 (Fl. 34*) Aurigas adje^la. In dextro humero. 

Sept. 5, Double. Near \ degree f. following /G, in a line 
1782. from the 27th continued through /3 Auriga; a confi- 

derable ftar. Very or extremely unequal. L. pr. ; S. 

d. Diftance 30^^ 3^^^ Pofition ^45° 6' n. preceding. 

92. Fl. 3* Arietis borealior. 

Sept. 10, Double. Full i degree f. following the 3d Arietis,. 

J782. in a line parallel to a Arietis and (JCeti ; the moft fouth 
of two. Equal. Both reddifh. Diftance 51^' i6^^\ 
Pofition 52° 45'' n. preceding or f. following. 

93. Fl. 103'™ Herculis fequens ad auftrum. 

Sept. ig, Double. About i| degree f. following the io3jd 

1782. Herculis, in a line parallel to the ift and loth LyriE ; 

the neareft of two. Equal, perhaps the following the 

fmalleft. Both r. Diftance 47'^ 46'''. Pofition 45^ 

42' f. following. 

94. Duarum Fl. 31^"" Cephei fequentium auflrina.. 

Sept. 30, Double. About | degree n. of the 31ft Cephei, 
1782. towards ctf Polaris. Pretty unequal. Botlipr. Diftance 
41^' ^o"\ Pofition 45° 15^ f. following. 

95. Fl. 51 Aquarii. In dextro cubito. 

oa. 2, Double. Exceffively unequal. L. rw- ; S. d. Dif- 
1782. tance Yth Clafs. Pofition n. preceding. Two. 


1 1 2 Mr. Herschel's Cafa/ogue 

V. - other flars in view ; the neareft of them extremely 
unequal. Pofitioii about 80 or 90° f. preceding. The 
farthefl: very unequal. Poiition about 30° f. following, 

96. u (Fl. 59'™) Aquarii fequens ad auftrum. 

oa. 2, Double. About | degree f. following u, in a line 
1782. parallel to 5 and c iVquarii. Extremely unequal. Dif- 
tance Vth Clafs near. Pofition 15 or 20° f. pre- 

97. Fl. 10 LacertSB. 

oa. 4, Double. Very unequal. L. w. ; S. r. Diftancc 
1782. with 278, 52'' 3^^^^» Poiition 38° 45^ n. following. 

98. Fl. 3 Pegafi. 

oa. 4, Double. Pretty unequal. L. wr, ; S. dr. Diftance 
1782. 34^^ 43^^ • Pofition 82° 48^ n. preceding. Befides II, 
62. another flar in view, Pofition following. 

99. Fl. 33 Pegafi. 

oa. 4, Double. Confiderably unequal. L. pr. ; S. r. Dif- 
1782. tance with 278, 45'^ 3^^^. Pofition 89° 12^ n. fol- 

100. Fl. 59 Orionis. 

oa. 4, Double. The following of two. Extremely \ine- 
1782. qual. L. w. ; S. a point requiring fome attention to 

be feen. Diftance ^y''' i$^'\ Pofition about 6f f. 

loi. V (Fl. 36="") Orionis praEcedens. 

oa. 4, Double. About | degree preceding t;, nearly in a 
1782, line parallel to jc and jS Orionis ; the fecond from v. 

Extremely unequal. L. w. ; S. r. Diftance 44^'' 

15''^ Pofition about 15° f, following. 


cj' Douhk' Stars. ' Jj 3 

V. 102. Pl. 61 Ccti. 

oa. 12, Double. Extremely unequal. L. rw. ; S. dr. Dlf- 
1782. tancc with 278, 2>l" S'^" ' Poiition 76' 21 i pro- 
ceding. A tliird il:ar at fome diilance. A iictle une- 
qual. Pofition n. following. 
103-. AI3 ; (Fl. 18^) Lynt* /3 vcrfus. 

Oct. 24, Double. Full \ degree f. preceding /, nearly towards 
1782. iG Lyra\ Extremely unequal. L. \v. ; S. r. Diilance 
with 278, 45'^ 32'^'^* Poiition 29° 12^ n. followhig, 

104. £ (Fl. 4*) Sagitti-e auftrallor et pra^cedens. 

Nov. 6, Double. Full \ degree f. preceding £, In a line pa- 
1^82. rallel to y Sagittae and y Aquil« ; the nejireft of two. 

Extremely unequal. L. pr. ; S. d. Diilance Vth Clafs. 

Pofition 16° 18' f. following. 

105. y (Fl. 14*) Sagitta; auftralior et fequens. 

Nov. 6, Double. About } degree f. following y Sagitti^e, in a 
1782. line parallel to Sagitta and Delphinus. Confiderably 

unequal. L. pr. ; S. r. Diilance 38^^ j6^^'. Pofition 

74"^ 15^ f. following. 

106. 7(Fl. 12') Saglttas boreallor et praecedens. 

Nov. 6, Double. About i\ degree n. preceding y Sagitta?, 
1782. towards the 6th Vulpecul* ; a coniiderable flar. 

Equal. Both rw. Diilance 38'' 54'''. Pofition 60' 

42^ n. preceding or f. following. 

107. Fl. 56 Aurigae. 

Nov. 6, Double. Confiderably unequal. L. w^ ; S. pr. 
3782. Diilance 52'' Si'"- Pofition 72° 36' n. following. 

108. y. (Fl. 13^) Canis majoris borealior. 

Nov. 6, Double. About % degree n. of v. Canis majoris. A 
1782. little unequal. L. dw. ; S. d. Dilhuice 42" S?)"* 
Pofition 23" 18' n. following. 
Vol. LXXV. Q 10;. 

114. Mr. HrnsciSEL^s C^talogfdg 

V. 109. Inter /3 Cancii et ^Hydrae. 

Nov. 6, Double. A large flar not in Fr.AMSTEF.D, between 
2782. 13 C.mcrl and Hydric. Exceiiively unequal. Drftancc- 
35" 24 ^'^ Poiition 3 >° o' n. preceding. 

I JO. Fl. Ill Tami. 

Ndv. 13, Double, ^'e^y unequal. L. rw. ; S. r. Diflance 
1782. 46'^ 42 '". Pofition 3' 48' n. preceding. 

111. Fl. 42"' Urlk mnjorls aufh-alior et i'equens. 

Nov. 20, Double. Full 1 degree 1. following tlie 42d, in a 
1782. line parallel to the 29th and 48tb Urlie majoris ; the 
middle of three forming an arch. Conliderablv une- 
qual. L. wr, ; S. r. Diftance ^o'^ ^o'\ Pofitioa 
5 1° 2j^ n. following. 

1 1 2. * Ex obicurioribus ^ and' v Gemrnorum fequentibus* 

Dec. T, Double. Forms almoft an ifofceks triangle with ^ 
1*^82. ^nd V Gemlnorum. Nearly equal. The preceding pr. 
the follow jn 2: wr. Diftance Vth Clafs far. 

113. * Fl. 9*"" itnter et i i''" Orionis, 

Dec. 7, 7Veble. About if degree f. preceding the nth 
1-82. Orionis, tovyards ; Tauri. The two largell; confidera- 
bly -unequal. L. w. ; S. pr. Diftance 37^^ 51^'^ Po- 
rtion '2j'^ 54^ n. preceding. The third farther off and' 
fmaller. S. r. Pofition n^ following. 

1 14. Fl. 103 Tauri. 

Dec. 7, Double. Excefiively unequal:. L. rw. ; S. d. Dif- 
^^82. tance with 278 and 625, 30'^ x"\ mean meafure. Po- 
iition 72'' 24'. 

1 15. Tauri. Fl. i 14. 

Dec. 7, Double. Excefiively unequal. Tv. w. ; S. a point. 

r;82. Diilance 5.''' 34'^'. Pofition 77' 54' f. preceding. 

2 Two 

«/ Double Stars, 1 1 5 

V* Two otiicr fniall liars following, nn<I" a third to the 

316. Fl. 41 Arietis. 

Dec. 2" Treble. The two nearefl exceflively unequal. T.. w.; 
1782. S. a point. Ulflance with 278, 39'' 2o''\ l\)iitioa 
So"" 48' f. preceding. For the diftance of tlie tarthefc, 
lee VI. 5. ■*. 

117. f (Fl. S^'""') Arietispraecedens ad borcam. 

Dec. 2-,% Double. About i| n. preceding f, towards the 41ft 
i;S2. Arietis; the following of four forming an nrcb.. ^^ery 
unequal. Both dr. Diflancc 34'' 4H"'. Pohtiou 47^ 
33^ n. preceding. 

118. 6 (Fl. 46^) Orionis boreallor et prsceden?. 

Dec. 28, Double. The mod 11. of three preceding e Orionis, 
3782. towards ijl Tauri. More north is another let of three; 
care mufl: be taken not to miftake one of tliem for this,. 
\ Extremely unequal. L. rw. ; S. d. Diftance Vrh 
Clafs. Pofition 1 3"^ 6^ f. preceding. Two more fol- 
lowing, exceffively unequal; one about i\ the 
about 1 1 minute. 

119. 6 (Fl. 46') Orionis auftralior et praecedens. 

Dec. 28, Double. Full | degree f. preceding g, in a line pa- 

1782. rallel to e Orionis, and b Eridani ; the fmallefl and mofl; 

f. of two. Very unequal. L. w^. ; S. r. Diftance 30^'' 

12^^^; a little inaccurate. Pofition 2 1"" 33 f preceding, 

A third ftar 2 or ^° f. following. 

* The ftar VI. 5. in the plsce referred to is called Flamsteeb's 35th 
Arietis. With fo many ftars and meafures it was hard'y poirible to avoid ieveral 
errors, I have therefore now added to the errata already given at the end of vol. 
LXXII. and LXXIII. of the Phil, Tranf. fome others, that have fince been detetfted 
by a careful review of the double ftars, and believe that no more will be found. 

0^2 120. 

1 1 6 Mr . I i E R sc H E L*' s Calaljg us 

V. 120. Fr.. 15 Hydiae. 
l>ec. 28, Double. Extremely uiicqual. L. vv. ; S. r. Dii- 

1782. t;ince 43'' i^'\ Polition about 70° n. preceding.. 
12!. ^ Coma; Berenices. Fl. 12. 

Jan. I, Double. Confiderably unequal. L. rw. ; S. pr. 

1783. Diibnce S^" 5S'"* Pofitlon about y;*-' f. following. 
122. Fl. 44^ Bootls nuilralior et priiecedens. 

'r-Au 8, Double. Near 5 degree i, prect-ding the 44tli, 
17H3. towards the 3Bth Bootls. Very unequal. L, bw. ; S. 

pr. Distance -^^'^ 2\''\ PolitioH 67^ 6' f. preceding. 
J 23. * In Andromt'ds pe6lore. 

JaiT. 8, Double. Equal. Both rw. or pr. Diflance 45'^ i'^'', 
i-8^. Porition j»2^ 24' f. preceding. Its place, as determined 

in 1777 by C. Mayer, is J9>. o'' 34' 33^' in time, and 

29- 45"' 3'^ decHi>ation north. 
124. g (Fl. 2"") Centauri fequens ad au{!rum- 
"fan. 31, Double. About 1 1 degree f. following ^ Centauri, 
.1783. in a line parallel to y Serpentis and ^ Centauri ; the 

moft f. of two. Confiderably unequal, Diftance 54''^ 

1 '^' ; too low for accuracy. 
12 y Fl. 46""" Bootls fequens ad boream. 

Feb. 3, Double. Near 2 degrees n. following the 46th, in a 
1 78-. line parallel to J" Bootis a^id Q> Coron;£ ; the third fbar 

about that dire«i^ion. Confiderably unequal. L. r. ; 

S. darker r» Diftance ^^^ 53^ Pofition ^7° Z^^ ^» 

126. r (Fl. 5'"') Herculis pra?cedens ad auflrum. 
Feb. 3, Double. Near | degree f. preceding r Herculis, In 
i-jS-^. a line parallel to y and c* Serpentis; a fmall Aar. A 

little unequal. Both pr. Diftance '^f' 51^^^ rather 

lull mcaltire. Pofition 52° 6^ f. preceding. 


of Dovble Stars, i ly 

V. 127. (Fl. 41*"') HltcuHs prsecedens ad boream. 
Feb, 5, Double. About | degree n. preceding the 41 ft Her- 
J7S3. culis, in a Hue parallel to z Serpentarii and /3 Herculis. 

Pretty unequal. Both r. Diftnace 48''4o''''. Pofirion 

19" 45' n. preceding. 

128, < (Fr.. 68*'") Virginis iequens. 

t^eb. 7, Double. About 1 1 degree following i Virginis, 
1783. in a line parallel to Spica and /Q Libric. A little uac« 
qual. L. pr. ; S. r. Di{laace4i'' 58''', 

129. / (Fl. 25'"') Virginis Icqucns ad lx)ream. 

Feb. 7, Double. About i\ degree n. lollowingy, in a line 
1783. parallel to y and e Virginis; a large flar. Very une- 
qual. L. r. ; S. dark r. Diftancc 46^' 42'^^ Pofitloii 
6 or y"' f. following, A double liar of the Vth Clafs 
In view, preceding. 
I 20. Fl. -2,^ ComiE Berenices. 

Feb. 26, Double. Very unequal. L. r. ; S. d. DiRance 
1783. 31''' 17^''. Pofition 36° 51^ f. following. 

13 1 . Fl. 24**" Librae fequcns ad boream. 

Mar. I, Double. About ri degree n. following the 24th 
1783. Librae, in aline parallel to tt and /3 Scorpii. Confidera' 
bly unequal. L. rw. ; S. r. Diftance 47'^ 46^^^ 

132. Fl. 29*'" inter et 30'"' Librae. 

Mar. I, Double. Of two between the 29th and 30th Librae 
1J83. that neareft to the 30th. Very unequal, L» w. ; S. d. 
Diftance 39'' 59^^^ 3 ^^^7 inaccurate. 

133. Fl. 60 Herculis. 

Mar. 7, Double. Extremely \inequaL L. w. ; S. d. Dif- 
1783. tauce 48'^ 40'". Poiitiou ^f\ o' n. preceding. 

1 1 S Mr, F-Ie R s c H E I / s Catalogue 

V. 134. ^ (Vl. 4"'") Ophiuchi priecedens ad auflrum. 
Mar. 24, Double. Abo'Jt i degree preceding and a little C of 
1783. -^t in a line parallel to ^ Ophiuchi and w Scorpii ; the 

fartheft of two In the bafe of a triangle. Equal. Dif- 

tance 45'^ 47'''- 

135. Ad Fl. 49*" Camelopardali. 

April 4, Double. The fmalleft and mofl f. of two that arc 

1783. about 20^ afundcr. A little unequal. Both r. Dif- 

tance with 278, 38''^ 1 8^"^ Pofition 85° o' f. preceding. 

136. 5 (Fl. 65^) Aquilae borealior. 

Sept. 12, Double. About f degree n. of ^, in a line parallel 
1783. to ?j and /3 Aquilae; a confiderable flar. Confiderably 
unequal. L. pr. ; S. r. ; Diflance with 278, 47'^ 5^^^. 
Pofition 65° 48 ' f. preceding. 

137. X (Fl. 17^) Cygni borealior. 

Sept, 22, Double. About 1} degree n. of %, towards J* Cygni ; 
1783. a confiderable flar. Confiderably unequal. L. garnet ; 
S. r. Diflance with 278, 35'' i''\ Pofition ^f 3' n. 


VI. G'], 7} Orionls. Fl. 28. In extremo enfis manubrio, 
Dec. 27, Double. Exceffively unequal, L. w. ; S. d. Dif- t 
1781. tauce i' 50'' 57''^- Pofition 35° 12'n. following. 


of 'Double Stars. j i p 

VI. 6S. J] (Fl. 28^) Orionis aiiftralior. 

Dec. 27, Double. About \ degree f. of, and a little follow- 
1781. ing ij, ill a line nearly parallel to I and t^ Ononis. Very 
unequal. L. r. ; S. d. Dlftance z' o" i\*", PoiiUoii 
7° 54'' «. preceding. 

69. Fl. :4Arietis. Supra caput. 

Dec. 27, Double. Very unequal. L. pr. ; S. dr. Diftance 
1781. i' -9^^ 28^". Polition li'ia' n. preceding. 

70. (3 Geminorum. Fl. 70. Supra caput prioris !£'. 

Dec. 2.7, Treble. Or two fniall flars in view ; the nearefl: a 

1781. little more than i minute ; the other not much farther. 

71. T Hydrie. Fl. 31. Trium inflexucolh auftraliffima. 

Jan. 20, Double. Pretty unequal. L. w. inclining to rofe 

1782. colour. S. pr. Diilance \' v" 40'''. Pofition 88" 36' 
n. preceding. 

72. Ad Fl. 68'™ Orionis. In fufle. 

Jan. 30, Double. The moil: n. of two that are i degree 
1782. ai under. Very unequal. L. \\\ ; S. dr. Diftance 
with 278, 1/ iz" $0'" , Pofition. 41° o' f preceding. 
73.. e Geniinorum.. Fl. 27. In boreali genu praecedentis U^', 
Feb. 2, 1782. Double. L. w. Diilance 1^ 50^^ 30^^^ 

74. Fl. 51 Geminorum. 

Feb. 2,, Has two very obfcure flars in view.. L. r. ; S. r. S. r, 
1782. The nea-reft about It, the next % minutes. Pofition. 
of both about 40 or 50"" n. following. 

75. (w Cancri, Fl. 4. Ad primum borealem forficem. 

Feb. 2, Has a very obfcure ftar in view. L. pr. Diflance 
1782. about I 5 minute. Pofition about 30*^ n. preceding. A 
thij'd about z\ Pofition more north. 


120 Mr. Herschhi,'^ Caiahgue 

VI. 76, ^ Leonls. Fl. 14.. 

Feb. 2, Double. Extremely unequal. L. r\v. ; S. r. Dif« 
1782. tance i' 3'' 29'''. Potition 49° 36' n. following. 
'^7. T VIrginis. Fl. 93. 
Feb. 4, Double. Very unequal. L. w. ; S. dr. Diflance 

1782. I'8^^2 2^^^ 

78. f (Fl. 16'"") Cancri fequitur. 

Feb. 8, Double. About i degree following ^Cancri, towards 
1782. ij Leonis. Extremely unequal. Dirtance i^ 3^''47^^^. 

79. (p Leonis. Fl. 74, 

Feb. 9, Double. V^ery unequal. L. w. ; S. pr. Diftance 
1782. i' 38'' ^S^'^* Pofition about 10 or 12° n. preceding. 

80. Fl. ()^ Leonis. 

Feb. 9, Double. Very unequal. L. w. ; S. db. Diftance 
1782. i^ 10'' 13'' . 

81 . Fl. 27 Virginis. In ala dextra. 

Feb. 9, Double. Extremely unequal. L. w. Diftance 
1782. i^ 28^U8^^ 

82. Fl. 31 Monocerotis. In media eauda. 

Feb. 9, Double. Very unequal. L. rw. ; S. db. DiftanQe 
1782. 1^ 10^^ ^3'^'- Pofition 40° o' n. preceding. 

83. Prope Fl. i^'" Orion is. 

Feb. 9^ Double. A few minutes f. following the ifl, towards 
j-82. the belt of Orion. Coniiderably unequal. L. pr. ; S. 
r. Diflance i' 20'^ 58'"^ Poikion 88^ 15' n. fol- 

84. Fl. 14 Canis minoris, 

Feb. 9, Treble. The nearefl extremely unequal. I^. nv. ; 
i;82. S. d. Diflance i' s" -^'''- Pofition 26^ 24' n. fol- 

VL lowing. The third forms an angle, a little larger than 

a redlangle, with the other two. Pofitlon f. following. 

^^. Fl. 27 Hydras. 

Feb. 9. Double. Very unequal. L. rw. ; S. pr. Dlftance 
1782. Vlth Clafs far. Polition about 60® f. preceding. 

86. Prima ad 0- Cancri. Fl. 51. 

March 5, Double. Extremely unequal. L. w. ; S. d. Pofi* 
1782. tion n. following. 

87. Tertia ad 0- Cancri. Fl. 64. . 

March 5, Double. Very unequal. L. rw. ; S. dr. Diftance 
1782. i' 25^^ as"'* Pofition 25° 12^ n. preceding. 

88. /3 Aurigae. Fl. 34. In dextro humero. 

March 5, Double. Extremely or exceffively unequal. L. fine 
1782. bluifliw. ; S. d. Diflance z' 49'' (i"\ Pofitlon 54* 
I z' n. following. A third farther off. Very unequaL 
About 40 or 50° n. following. 

89. Fl. 6* Bootis adje6ta. 

Mar. 12, Double. Juft following tlie 6th Bootis. A little 
1782. unequal. L. r. ; S. deeper r. Diftance i' 19^^ y)'"^ 
Pofition 58° 6^ f. preceding. 

90. Fl. 61 Virginis. 

Apr. 3, Double. Very unequal. L. w. ; S. d. Dlilan«e 
1782. i' 13"' I5^^'« Pofition about ']^'' n. preceding. 

91. Prope y (Fl. 24^"") Geminorum. 

Apr. 15, Double. Three or four minutes n. of y Geminorum. 
1782. Confiderably unequal. Both fmall; too obfcure for 
meafures with 7 -feet; my 20-feet fhews a third flar 
'between them with 12 inches aperture, 

Vgl.LXXV* R 92^ 

122 Mr. Herschel's Catalogue 

VI. 92. <^ (Fl. i^) Capricorni borealior. 

June 14, Double. About J degree n. of J Capricorni. Very 
1782. unequal. Both r. Diftance i' 2.'^ \6^'\ Pofition 
2° 3^ f. preceding. 

93. Coronae borealls. Fl. 15. Ad fummum. 

July J 8, Double. Very unequal. L. w. ; S. d, Diftance 
1782. i' 27^^44''^'; a little inaccurate. Pofition 54° 27' f. 

94. A Corona borealis. Fl. 12. 

July 18, Double. Extremely unequal. L. w. ; S. r. Dif- 
1782. tance 1^35'^ i^'^\ Pofition 33^ 12^ n. following. 
pj. 72 Bootis. Fl. 8. Trium in (iniftro crure borea. 
-Aug. 3, Double. Extremely unequal. L. w. inclining to 
1732. orange; S. r. Diftance about if minute. Pofition 
about 25 or 30*^ f. following. ^ 

96. f Perfei. Fl. 44. In pede finiflro. 

Aug. 25, Treble. The nearefl extremely unequal. L. w. ; 

1782. S. r. Diftance 1' ii^'' 2b''\ Pofition 66° 36' f. pre- 
ceding. The fartheft very unequal. S. r. about if 
minute. 70 or 75° f. preceding. 

97. Secunda ad t i^quarii. Fl. 71. In dextro eruie.. 
Aug. 28, Double. Very unequal. L. r. ; S. d. Diftance 

1782. 2' 3^^ 36^^% mean meafure* Pofition 18^ 30'' n. pre- 

98. Fl. 46''" Tauri fequens ad auftrum. 
Sept. 7, Double. About i| degree f. following the 46th,. 
iy82. nearly in a line parallel to the 38th Tauri and the 42d 

Eridani. A little unequal. L. pr. ; S. r. Diftance 
Pofition 43° 48^ n. preceding. A double 

r 2 

// ^ /// 

ftar of the Vth Clafs in view, following within ^\ 


of Double Stays. 1 2 j 

VI. Equal. Both fmali and r. Almofl ftmilarly fituatcd 

with the above, but politioii more n. preceding* 
^g, m Perfei. Fl. 57. In dextri pedis talo, 
Sept. 7, Double. Pretty unequal. [>. r. ; S. rw. Diftancc 
1782. i^ 3^" ^Y^^* Pofition 71° 51^ f. preceding. 
100. / (Fl. 32^'")Cephei fequens. 

Sept. 30, Double. About i| degree n. followiiig i, nearly 
1782. towards y Cephei. A little unequal. Both pr. Dif- 

tance i' i^^ 54^^''* Pofition 8° 9' a. preceding. 
loi. I Tauri. Fl. 68. 

oa. 31, Has two ftars in view. The neareft exceffively une- 

1782. qual. L. w. ; S. d. Diftance with 278, i' 2,'^ i8''^ 

Polition 35° 24' f. preceding. The fartheft extremely 

unequal. S. r. About i { minute. Pofition about 50'^ 

n. preceding. 

102. Fl. 5 Lyncis. 

Nov. 13, Double. The largeft of a fmall triangle. Very 
,782. unequal. L. r. ; S. garnet. Diftance 1^ 28'' 20''^ 
Pofition 2° o' n. preceding. 

103. ePegafi. Fl. 8. 

Nov. 20, Double. Very unequal. L. pr. ; S. dr. Diftance 
1782. i' 30'^ S^'^' Position 52° 45^ n. preceding. 

104. ^Bootis. Fl. 30. In dextro calcaneo. 

Nov. 29, Has a very obfcure ftar in view. Extremely unequal. 
1782. L. w. inclining to r. ; S. d. Diftance about 1 1 miiiute. 
Pofition almoft diredly preceding. 

105. Fl. 105 Tauri. 

Dec. 7, Double. Very unequal. L. pr. ; S. r. Diftance 
1782, 1' 41'^ Z()''\ Pofition 18° o' f. preceding, 

R 2 J 06. 

fi'4 ^^^- Herschel's Catalogue 

\'L loC. b Eridani. Fl. 62. 

Dec. 7, Double. Connderably unequal. L. w. ; S. pr^ 
1782. Diftaiice i^ o^' 26'^'. Poiitlon 1 5" 9^ n. following. 
107. Fl. 31^ Monocerotis aufrralior et prircedens. 
Dec. 21, Double. About i| degree f. of, and a little pre-- 
1782. ceding the 3 1 il Monocerotis, in a line parallel to ^ Hy- 
dr;£ and the 311I Monocerotis ; the moft fouth of two.- 
Confiderably unequal. L. r. ; S. deeper r. Di^auce 
about 1 1 minute. Poiition 50 or 60° £ following. 
P08. 5 (Fl. 22^)Hydri£ borealior et praecedens. 
Dec. 20, Double. About | degree n. of, and a little pre*- 
2782. ceding 5, nearly in a line parallel to « and ^ Hydras.- 
Very unequal. L, r. ; S. blackifli r. Vlth Clafs far. 
Polition I or 2° n. preceding. A third flar preceding. 

109. Fl. 22 an 26 Cancriincertum. 

Dec. 29, Double. One of the two being loft *, it does not 
■1782. appear which is the remaining ftarr Very unequal. 
L. r. ; S. dr, 

1 10. Telefcopica ad Ceti. 

Jan. 2, Double. Looking for Ceti, which was invifible to 
1783. the naked eye, I miftook this for it. Pretty unequal. 
L. rw. of about the eighth magnitude ; S, r. Diftance 
1^20'^ S^''\ PofitIon33°42^ 
Ti I. a Hydrse. Fl. 30. Duarum contigtiafrum lucldior. 
Jan. 8, Has two ftars within about 2 minutes ; the neareft" 
1783. exceffively unequal; the farthefl extremely unequal. 

Both f. foUawing. 
112. Fl. 13 Bootis. 

Jnn. 8, Double. Extremely unequal. L. t. ; S. dr. Dif- 
J783. tance i' 17^^58^'^ Pofition 7^24^ n. preceding. 

» See Phil. Tranf. vol. LXXIII, p. 252,-^ 


of DQuble Stars,- ^-i^ 

VI. 113. Fl. 4 Virginis. 

Jan. 8. Double. Extremely uneqml. L. wr. ; S. dr.. Dif-- 
1783. tance z' z^" 44''^; too obfeure for accuracy. 

1 14. Fl. d^"'^ Orionis priccedens ad auftrum. 

Jan. 9, Double. About i degree f. preceding, trhe 69th, 
1783. nearly towards A Orionis. Confiderably unequal. L. 

pr. ; S. d. Diftance i' o^o" 38'''. Polition 22"^ W f. 


115. Fl. 2 1 '■" Crateris fequens ad auftrum. 

Jan. 10, Double. About z\ degree f. following the 21 fl, in 
1783. aline parallel to the 12th Crateris and 4th Corvi. Very 
unequal. L. w. ; S. r. Pofition 12° 12' n. following. 
i 16. Fl. 43 Herculis. 

Jan. Id, Double. Very unequal. L. inclining to garnet ;'■ 
3783. S. r. Dlftance \' i^" 37'''. Polition 38*^ 48' f, pre- 

1 1 7. Fl. 12^ Librae borealior et priscedens^ 

Jan. 10, Double. x'\bout i^ degree n. preceding the 12th 
178-^. Libras, towards Spica. Very unequal. L. rw. ;_ S. r. 
Pofition about 40° f. preceding, 

118. Fl. 30 Monocerotis. 

(Feb. I", Double. Very or extremely unequal. Diftance 

II o. e (Fl. 18') Plfcis auftnni auftralior et praecedens. 

July 28, Double. About i| degree f. of, and a little pre- 

578". ceding £ Pifcis auflrini, in a line fromJ* Aquarii continued 

* On account of the change In the magnitudes of the ifl: and 2d Hydr^e, this 
fmall ftar may be of ufe to afcertain whether the 30th Monocerotis, which is 
fituated between them, has any confiderable proper motion. See Phil. Tranf. voL 
LXXllI. p. 255. 


1 2 6 Mr. H E R ^. c 1 1 R t/s Calakgue of Double Stars , 

through e Pifcis. Pretty unequal. Iv. dpr. S. dr. 
Dlftance i' 26'' 58''". Pofitlou 6f 46^ f. following. 

120. Fl. 43"" Saglttarii fequeiis ad auftrum. 

Aug. 16, Double. Near i degree f. following the 43d, in a 
1783. line parallel to | and Sagittarii ; a confiderable flar. 

Very unequal. Both dr. Diftance with 278, l'' 14'' 

^''\ Pofition 2"^° o^ n. preceding. 

121. Fl. 1 2 Lacertje. 

Aug. 18, Double. Very unequal. L. w. ; S. r. Diftance 
1783. with 278, 1^0" io^^\ Pofition 73° o' n. following. 

Add the following errata of the Catalogue of Double Stars in 
vol. LXXII. to thofe already noticed at the end of the 
LXXIId and LXXIIId volumes. 




Read J 







19" 14'" 

19" 26'" 



35" 48'" 

36" 9- 



V Capricorni. Fl. 10, 

f Capricorni. Fl. ii. 



33° 4a' 




Fl. 5. 

Fl. 4. 

r/,//,^./;„„.,: I ■„/. L xxir Taij. V. p.iif,. 



[ '27 ] 

VII. Obfervatio?2S of a fiew variable Star, In a Letter from 
Edward Pigott, Efq. to Sir H. C. Euglefield, Bart.F. R, S, 
and j^, S. 

Read December 23, 1784. 

D E A R s I R, 

FOR fome years pad 1 have been employed in verifying 
all the flars fufpeOed to be variable, in order that here- 
after we may know with certainty what to depend upon. This 
undertaking, which is nearly completed, has already proved 
of ufe in detecting many miftakes, and producing fome difco- 
veries ; among which, the following is one of the mofl: im- 
portant. September 10, 1784, I flril: perceived a change in 
the brightnefs of the ftar vj Antinoi, and by a feries of obfer- 
vations made ever fince, I find it lubjed: to a variation very 
limilar to that of Algol, though not exadlly the fame in any 
one particular. 

7] Antinoi, when brightefl:, is of the third or fourth magni-^ 
tude, being between S and (3 Aquilas ; and at its leaft bright- 
nefs of the fourth or fifth magnitude, it then being betweea 
that of I Antinoi and ^ Aquilae ; therefore, its greatefl varia- 
tion in brightnefs may be called about one magnitude ; and the 
changes it undergoes, though probably not nicely afcertained 
from fo few.obfervations, are nearly thefe :, 

4 At 

12^ Mr.'9iGorr\Obfervatlons 

At Its greated brightnefs 44 =t hours. 

In decreafins: - - 62 dr hours. 

At its leafl brightnefs 30 ± hours. 

In increaiing - - S^ — ^^o^^s. 

All thefe changes, which hitherto feem to be regular and con- 
flant, are performed in 7 days 4 hours 38 — minutes; this Ifhali 
il:ile its period, and hereafter will fhew how it is determined 
with fuch exa6lnefs. 

The ftars to which ^ Antinoi was Compared are in order 
thus : ^ Aquil^e third magnitude, /3 Aquilas and 5 Serpentis 
fourth magnitudes, i Antinoi fourth or f fth magnitude, and ^, 
Aquilas a bright fifth. I find, by feveral years obfervation, 
that /3 Aqullas retains the fame brightnefs. ; Antinoi, which 
has been examined with particular attention by Mr. Good- 
rick e and myfelf, is fufpe(£ted by us both to be fubject to ar 
fmall variation, but not fufficiently appar^ent, fo as to afted: 
materially thefe comparilons, and poffibly it may be only the 
effedt of fome optical iliuiion ; for I have frequently remarked, 
that both in the twilight and moon- light, or when the air is in 
the leafl hazy, there is a greater difference between the bright- 
nefs of many of the ilars, than in a dark night and clear fky. 
In the following journal of obfervations of 17 Antinoi, the 
Greek letters /3, ^, jt*, belong to Aquila, and ;, v, to Antinous ; 
fecondly, the magnitudes marked in column the third are by 
eflimation, and can be of no further ufe than merely to give, 
at firft fight, an idea of the ftar's brightnefs ; and laftly, the 
lines diftinguifhed by inverted commas, are extra«5ts from Mr, 
Goodricke's journal, whofe friendly afliflance I have often ex* 
perienced, and was the more welcome on this occafion, becaufe 
repeated attention and great exadnefs were requifite, 

K Dates. 

bf a new Variable Star, 




July 17 


Sept. 10 


> :;j: i. 



28 1 
^29 J 


oa. I 


















I9 J 








3 -4 




















Journal of the comparative brightnefa of 1 Atitinoi. 


Vgl. LXXV, 

r Lefs than J Aquilx and brighter than 6 Scipentis (Ji 
I Aquila; and S Serpentis are cqxial) weather hazy. 
P.ather brighter than ^ Aquilse and fi Serpentis. 
If any difterence, lefs than (3 Aquilre. 

N. B. Thefe times are from recoUefiion, and cannot 
err more than i| hour. 
Lefs than /3 Aquilce and Serpentis. 
iVluch lefs than /?, equal to 1. 
*' A little brighter than 1, air clear," 

Lefs than ^, brighter than /3, and much brighter than p 

'* Brighter than t and $." 

Rather brighter than /3, and much brighter than s, 

'* Lefs than & and»." 

Much lefs than /3, and equal to u 

<' Lefs than ^ and.." 

f Brighter than |3 and »; at 1 1 h. it fcemed to have 
I increafed. 

J Lefs than ^, rather brighter than^ji thought it rather 
1 lefs at ii|h.; moon near. 

Brighter than /3 ; moon-light. 

If any difference, rather brighter than /?. 
" Rather brighter than ^." 

Lefs than i3, brighter than»; air clear, moon-light. 

Equal to 1, much lefs than /3, 
" Lefs than u" 

Between the brightncfs of ^ and J* 
" Brighter than ^ and »." 

Rather brighter than jg, 

" Much the fame as yefterday." 

Brighter than » ; think it not lefs than /3 ; this obfer- 
vation doubtful, occafioned by intervening clouds. 
" Believe it lefs than »; weather bad." 
*' Certainly lefs than /3; weather bad,' £>< 

" Lefs than » ; rather a doubtful obfeivation." 
Rather lefs than (3, and brighter than ». 1 

Equal to ^. 

" Rather brighter than /3.'* 
Lefs than |S, brighter than % 

S . Dates. 





06t. 16 





^ 24 




Nov. 3 









/ 7 





I H \ 
I7 J 



















Mr. Pigott's Obfervations 

Journal continued. 








r 3 

















5 " Lels than B and *." 

5 Undoubtedly lefs than 1. 

Lefs than », brighter than /^ . 

"Lefs than.." 

Evidently brighter than /3. 

" Much brighter than/S.'* 

" Brighter than ^." 

Lefs than |3. 

" Not fo bright as ^, brighter than »." 

Equal to », much lefs than j3 ; moon-light, air clear. 

f " Lefs than. • 5 rather, though very little, brighter 

1 thanju." 

Much lefs than ^, equal to », brighter than /*. 
Sometimes feemed rather lefs, but generally equal toj3; 
Equal, if not rather brighter than Q, 

/ " At 6| rather lefs, at 8| nearly equal, and at 9I 

L " rather brighter than ^.'*. 

r Remarkably bright, nearer 5 than /3; moon-light, 

1 • air clear. 

" Nearer to /S than to J." 

Seemed equal to ^ ; air not very clear, 

" Rather brighter than &" 

Evidently lefs than &. 

Much lefs than /3, 

" Lefs than /I and *."" 

Brighter than |S, much lefs than ^. 

Rather brighter than ^, certainly equal, - ■* 

" Rather brighter than^ and «." 

Lefs than/3, equal to •, 

" Lefs than /3, and rather lefs than h" 

I Evidently lefs than ^, and rather brighter than «j at- 

I 8' it feemed increafed, and about 
Between its leafi: and full brightnefs. 
" Lefs than |3, and fomething lefs than£.'* 

Brighter than ;S. 

if any difference, rather brighter than ^ ; clouds cov- 
J ered the moon: at 8h.if any difference rather; lefs- 
( than ^; moon-light, and air not fo clear as at 6. 

" Rather brighter than (3,. brighter than i." 

Rather lefs than (3, brighter than ,. 

Lefs than |3, rather brighter than 13 moon-light. 

" Brighter than /3." 

[f \ny diflerence, lefs than /3, 

Ili \ 

of a new Variable Sta}\-^\ i^^ r 

■In order to obtain a point of comparifon, for fettling the 
periodical changes of tj Antinoi, which I fuppofe to be con- 
ftant, it is natural to fix upon that phafis, which can be deter- 
mined with the greatefl precifion ; and this feems to be at the 
time when it is between its leaft and greateft brightnefs, as 
clmoji the whole increafe of brightnefs is completed in lefs than 
24 hours, though the perfect completion is performed only in 
n^d ±L hours ; thus having fettled this neceffary point, and found 
roughly the length of a lingle period, the computations, in 
order to obtain greater exadlnefs, areas follows. 

S s Ti 



Mr. PiGOTT^s Ohfervaiions 

Time when », Antlnoi was 
between ifs leaft and greateft 

Intervals between 
the obfervations. 

Number of pe- 
riods in ditto. 


gth of a 
e period. 


J 784, Sept. 12. at 20 1 
Oa. II. at 11 J 

Days. Hours. 

28 15 

4 each of 



. Hours. 


Sept. 12. at 20 1 
0(5t. 18. at 20 J, 


5 I^° 


41 -^ 

Sept. 1 2. at 20 1 
OQi. 26. at 00 J 


43' 4 

6 D* 


41 - 

Sept. 12. at 20 1 
Nov. 16. at 8 J 

64 12 

9 D^ 



Sept. 19. at 20 -\ 
Odl. 18. at 20 J 


4 D^ 



Sept. 19. at 20 1 
0£l. 26. at 00 J 

3^ 4 

5 D^ 



Sept. 19. at 20 1 
Nov. 1 6. at 8 J 

S7 12 

8 D^ 



Od. II . at II •) 
Nov. 16. at 8 J 

3S 2r 

5 D° 



oa. 18. at 20 1 
Nov. 1 6. at 8 J 

28 12 
ingle period, ( 

4 D" 

XI a mean, 




I .ength of a f 


4 30 

Perhaps other aflronomers may not exadly agree with me, 

in fixing the times as fet down in column the firft ; for my 

part, I determined them without paying any regard to the 

refults, by taking a medium between the times when n Antinoi 

4 had 

oj a new Variable Sfat\ i -^ j 

had rather pnflecl its lead brightnefs, being nearly equal to i An- 
tlnoi, and when it was a little, but undoubtedly, brighter 
than jQ Aquilas. I'hough it does not appear, as I have already 
faid, that any of the other phafes can be fettled with equal 
preclfion, different comparifons neverthelefs may prove fatif- 
fa61:ory towards corroborating t^e above ; I have therefore alfo 
deduced its period from the beft and moft diftant obfervations^ 
made when at its leafl brightnefs; they are thus: 7 days 
o hours and 7 days 5 hours. Thefe refults I reject, and retain 
the mean given by the flrfl: fet, with which we may proceed on 
to gain a much greater exaulnefs ; let one period be lubtra^ted 
from the obfervation of July 27th, 1783, and it will appear^ 
that 17 Antinoi had varied in brightnefs during the following 
four daySy though at that time it did not ftrike me. 

July 17th, decidedly brighter than /3 Aquilae. 

— 1 8th, not obferved. 

1783, "J — 19th, rather brighter than ,G Aquilas. 

— 20th (anfwering to the 2 7tii) equal or rather 
lefs than jG A qui lie. 

As it is therefore evident, that on July 19th and 27th, 1783, 
7] Antinoi was decreafing in brightnefs, I fhall compare thole 
days obfervations to correfponding ones made in 1784, 


i784,Sept. 30. at 61 

Oa. 7. at i6j . . 

0£t k: at A I Similar obfervatrons to that of 1783. 

Oa. 22. at lif J^^^^ ^^th, at 10 h. ±, 7; Antinoi being 
Nov. 12. at 2I "^^^^^ brighter than /3 Aqujlae.. 

Nov. I p. at 00 


1^4 ^^^'' Pigott's Obfervatrons 


1^84, Sept. 30. at 18 "j 

061. 15. at 14 i Similar Obfervations to .that of 178^^ 
0£l. 22. at 19 /- July 27th, at 10 h, rt, ^ Antinoi being 

Nov. 12. at 


equal to or 

rather lefs than /3 Aquilae. 

Nov. 19. at 14. 


Ill eftimating the 

; above times, I 

paid much attention to the 

obfervations of the preceding and 

following days ; however, a 

few hours more or lefs do not make a material difference, Tho 

I'efults of thefe comparifonsare 
































43 -V 







On a mean 7 


38 - length of a lingle period. 

As this approaches the mofl to the preceding refult, It may be 
aiTumed as neareft the truth, provided the changes be uni- 
formly periodical. 

Hitherto the opinion of aftronomers concerning the changes 
of Algol's light feem to be very unfettled ; at leaft none are 
univerfally adopted, though various are the hypothefes to 
account for it ; fuch, as fuppofing the ftar of fome other than 

a fpherical 

of a new Variable Star, i or 

a fpherical form, or a large body revolving round It, or with 
feveral dark fpots or fmall bright ones on its furface, alio giv- 
ing an inclination to its axis, &;c. ; though moil: of thefe con- 
jectures with regard to Algol be attended with difficulties, fome 
of them combined do, I think, account for the variation of 
yi Antinoi. 

Thofe perfons who are accuftomedto examine the flars atten- 
tively will not befurprifed to find, that Mr. Goodricke and I 
do not always perfe(5lly agree in our obfervations ; thefe fmall 
differences in the magnitudes of the flars are very difficult to be 
afcertained with the naked eye, which has often made me la- 
ment, .we had not fome contrivance for determining their relative 
brightnefs, and even I attempted feveral methods, but did nor 
purfue them with fufficient attention and diligence to obtain 
any fatlsfa£l:ory refults ; neverthelefs I fhall juft mention them., 
as perhaps fomebody elfe may overcome thofe difficulties, 
which to me appeared fo very confiderable. 

1. In 177S I had fmall pieces of fine glafi ftained with dif- 
ferent (hades, which being applied to the eye end of a telefcope, 
I could eafily find what degree of fhade was requifite to efface 
flars of different brightnefs \ and thus I obferved fome of the 
ftars and planets. 

2. Diaphragms were attempted ; but, befides other diffi- 
culties, they did not efface flars of the firfl magnitude. 

3. A method which pleafed me much, and perhaps may not 
prove unfuccefsful, is, by putting the flars out of the focus of 
a telefcope till they become invifible ; this is performed by 
drawing the eye-tube of a refra6lor either in or out; the point 
of focal diflance being previoufly determined, the brighter the 
ftar the greater length of tube mud be (lid either in or out to 
efface it ; thus I was in hopes of determining their magni- 

z tudes^ 

136 A/>. PiGOTT*s Ohjervations^ &:c. 

tudes, and for that purpofe had in 1776 divifions engraved on 
the eye- tube of a refraftor ; but found tliat its high magnify- 
ing powers prevented ftars of the firfl and fccond magnitude 
becoming invifible. 

Laflly, I am inchned to think the following method pradi«» 
cable, vi%. to refle£l in a telefcope, by means of an illumina- 
tor, different degrees of light in a known proportion, fo that 
ftars of all magnitudes may be obliterated. 

The changeable ftate of the weather will perhaps be thought 
a confiderable obftacle to thefe contrivances, and to throw doubt' 
•on the obfervations ; but this may be fufficiently obviated by 
attending to fmall telefcopic ftars, which according to the 
clearnefs of the atmofphere are more or lefs diftinftly feen. 

I beg the favour of you, dear Sir, to prefent thefe obferva- 
tions to the Royal Society ; and believe me, with the greatefl 
regard, &c. 

York, Dec. 5, 1784. EDWARD PIGOTT. 

[ '37 3 

VI I r. Ajlronomical Obfervations, In iwO Letters from M. 
Francis de Zach, Profeffbr of Mathematics, and Member of 
the Royal Academies of Sciences at Marfeilles, Dijon, and 
Lyons, to Mr. Tiberius Cavallo, F. R, S. 

Read December 23, 1784. . 

SIR, Lyons, ApfH 4, lySj.' 

1SEND you the account of the obfervations on the eclipfc 
of the moon, which I have made together with the rev. 
Father le Fevre, Aftronomer at Lyons, in the Obfervatory 
called au grand College i to which I fliall add the obfervations of 
the vernal equinox ; fome obfervations on Jupiter's fatellites, 
made at Marfeilles by M. Saint JacoLJEs de Sylvabelle ; 
and, laftly, a new fblution of a problem that occurs in com- 
puting the orbits of comets. If you think that thefe obferva- 
tions do in any way deferve the notice of the Royal Society, I 
fhall be v^ery glad you would communicate them. In order to 
afcertain the going of the pendulum clock, I took feveral cor- 
refponding altitudes of the fun, which you will find in the fol- 
lowing table. On the day of the ecliple the Iky was very 
ferene, nothing could be finer, and it continued fo during the 
obfervation. I determined to ufe an achromatic telefcope of 
3! feet length, that fhews obje<Sls in their natural pofition, be- 
caufe the dikited and uncertain te<"mination of the true fhadow 
of the earth appears more perfectly defined by fmall than by 
Vol. LXXV. T ' large 

j^S M DE Zach's JJlronomicni Ohfervatpons* 

large telefcopes, which magnify too much, and give too great a 
tranfit between the penumbra and the true dark fhadow. On 
that account feme celebrated aftronomers advife to ufe for the 
eclipfes of the moon no greater telefcopes than of four or five 
feet length. It was remarked at Paris, that in an eclipfe of 
the moon, obferved through a tclefcope of DoLLOND,the focus 
of its object lens being 30 inches, and likewife through a tcle- 
fcope of five feet length ; the eclipfe appeared to begin 4^ 7^' 
fooner, and to end 4^ Y' l^ter, through the fmall than 
through the long tclelcope ; the like has been remarked by 
feveral others, and it has been alfo obferved bv mvfelf. As to 
my obfervations I am tolerably fatisfied with them, as they do not 
differ materially from thofe of Feather le Fevre, though it is 
known that in eclipfes of the moon no greater exa£l:nefs than 
that of a minute can be obtained. The moon's fpots were 
carefully obferved ; for it is known, that the mean of the ob- 
fervations of the moon's fpots is fufficient to afcertaln the 
longitude of a place to 4'^ or ^" nearly. M. de la Lande 
comparing the oblervations of the moon*s fpots in an eclipfe, 
made the 22d of November, 1760, in Vienna, by the Impe- 
rial Aftronomer Abbe Hell, with thofe made at the fame 
time in Paris by M. Messier, finds the difference of meri- 
dians td be 56^ ^o^"* which agrees very exactly with thatt afccr- 
tained by other means. 


M, DE ZACH'b JJinoriomual Ohfcrvatms^ 






. ^ 












V «— * 





















« i-i 






• ' ' 


















x: o 










»-< ^. 


^ CO 



•H xn 


OJ • 

" in 



tH ^ 


■^ c 

-g C- 

^ O 





O •- 






_a rt 


w > 

^ CO 



t-" d 





l»4 1-4 



:3 ^ 

r/:; nj 

1 • 




cr„ iy> 


X3 C 

^ ►-< 



"^i- « 


o o 










►H OJ 


■ ■ >-.-• 



M 1-4 


." J 


c -r: 

3 — 

„ r>. 

Vi rt 



^ r^ 



«™ iy» 






^ « 

IS § 

^ H4 



CO oo 

o -Z 





-a ^ 






M N 


t— « 


^m 1—4 

^ O 


a 'z 




^ »J^ 



CO lO 



^ CJ 


^ « 


"^ S 

^ .2 




•O CO 


o « 






S ^ 




•-4 Ct 





<^ IM 

. o 

U5 • 
•% 4-1 


c ■- 


,^ "5 

° C< 


:; « 



CO «J^ 


■* • 






» u^ 



CO 00 


o ■;:; 






^ CO 




>-< CJ 



.s'" • 


r" ^ 

5 J:; 


C/D rs 



r-"'^'— s 



. — ■ — . 


upper limb 
aftern fide 

b at 


g 0, 

m's upper lim 
the fame altit 
weftern fide ■ 

he fum 
ter on 

anas ma 
of the 


fn . «J 

+-» ^ 

^ 'o 

he fun'; 
at the 

Sun's ce 


by the 





U } 



Z H 

T a 



M DE Zach*s Aj]ronomicc\l Obfervations, 

iQih March, 1783. 

tal •\ 

The futj's upper limb at the horizontal 
wire of th^ firft telcfcope on the eaftern 
fide - - . J 

Sun's upper limb at the fame altitude on 
the weftern fide of the meridian 

Dividing the fum by 2 

iiun's center x)n the meridian as marked by\ 
the pendulum c'ock - - J 

Equition of the day 

Clock (lower than equated folar time 


o / 

3» 30 

Jfl oblerva- 

9 I 56 

H 31 47 

23 o^ 43 

11 46 51I 

12 7 57 

o 21 



lid obfer- 

h. , ,,. 
9 13 9 

14 20 33; 

23 33 4^ 
II 46 51 

^2 7 57 

o 21 

Clock flower than equated folar time 1 9th March 21 6 
■ -■ i8th March 19 32 

■.■■■■»M«| , ■ H I III II. Ill I I I 

Retarding of the clock upon 23 h. 58' 8" - I 34 

I obferved too the mid-day at the great gnomon of the ob- 
servatory, and found at the fame time the meridian line erro- 
neous by I ^'\ as you will find in the following tables. 

When the center of the fun's 
image was on the meridian the 
time pointed by the clock was 

Equations of thofe days 



11 50 50 

12 8 33 

Retarding onequjitcd folar time 17 a"^ 

Retarding the 17th 

Retarding of the clock during thofe 24. hours 




/ // 

1 1 48 56 

12 8 15 

19 19 

17 43 





/ /' 

ii 47 3 
12 7 57 

20 54 
19 19 

I 35» 

I fixed therefore the retarding of the clock i' ^^^\ 


M. DE Zach's j^Jlronom'ical Ohfervaiions. 


True mid-day concluded by the fun's correfpon- 1 
dent altitudes as the clock marked J 

Equation of the mid-day 

Retarding of the clock at the rate of i' 35" 1 
per 24 hours - - - J 

True mid-day the pendulum clock fhould | 

have marked - - - J 

Mid-day concluded at the gnomon of the 1 

obfervatory . - - - J 

Difference, the error of the meridian line 
or gnomon - - . 


II 48 42 
- 18 

+ 13 

II 48 37 
II 48 56 




II 46 51 
- 18 
+ II 

II 46 44 

II 47 3 


From thence I concluded. 


Mid-day at true folar time ii 5.9.60 
Mid-day the clock flxould 1 ^ 

have marked on the 1 8th J ^ ^' 

Retarding upon true folar 


T-l 23 

Mid-dayatequatedfolar time 12 8 15 
Mrd-day the clock fhould \ o 

have marked on the i8thj ^ 3/ 

Retarding upon equated! 
folar time *• J 

19 38 




M, DE Zach^s Aftrommlcal Ohferi^citions, 

Obfervations of the' moon's ecllpfe the 1 8th March, 1783. 


My obl'eivations with ati achromatic teielcojie of 33- 
feet length. 

by the. clock. 

True or ap- 
parent time. 

The bcgianing of the eclipfe very doubtful, 
, Shadow touches Grimaldi 
Grimaldi all in the fliadow 
Shatiow touches Mare Humoruno 

7 4^ 45 
7 42 54 

7 49 32 

8 21 

8 2 29 
8 6 18 
8 12 ig 

8 13 43 
8 lb 7 

8 21 31 

8 25 54 

8 32 21 

8 33 29 
8 35 36 
8 36 5^ 
8 38 57 

10 19 57 
10 23 33 
10 24 9 
10 29 34 

10 35 37 
10 43 6 

10 57 32 

11 15 44 
II 20 10 



























53 39 

54 48 
I 27 

12 16 
14 24 
18 13 

24 15 

25 39 
2^ 3 
33 27 
37 50 

44 18 

45 26 

47 33 ■ 

48 53 
50 55 

32 2 

35 38 

36 14 
41 39 
47 43 

55 12 

9 39 

27 51 
32 18 


Copernicus all in the fliadow 
Tycho touches the fliadow 

Mare Serenitatis touches the fliadow » 

111 1 ti f nf* ffTi<im\r . ■■ 

Proclus touches the fliadow 
Mare Crifium touches the fliadow 

oM Tn f nf* tlnniOU'' . » 

Total immerlion - - *• 

Beginning of the emerlioa 
Grimaldi emerging 

Mare Humorum emerging 

Total emerfion of INIare Humorum 

Copernicus all out of the fliadow 

Mare Serenitatis all emerged 

Mare Crifium all emerged 

End of the eclipfe • 

Total duration . . - 


M, DE Zach's Ajlronomkal Objervatlons. 


Father le Fevre's obfervations with a refle(n:or k,c^ niches 
focal length, magnltynig 300 times. 

I ]M M E R s I o N s. 
Grimaldi touches the fliadow 
Kepler touches the ftiadow' 
all in the fliadow 

Copernicus touches the fliadow 
all in the fliadow 

Mare Serenitatis touches the lliadow 
all in the fliadow 

Mare Crifiam touches the fliadow 
. — . all in the fliadow 

Total immerlion 

Beginning of theeraerfion 
Grimaldi emerged 
Kepler all out of the fliadow 
Copernicus all out 
Mare Serenitatis all out 
Crifium all out 

End of the eclipfe 
Total duration 

Time by the 






/ // 

7 41 43 

7 53 37 ■ 

7 52 2 

8 3 57 

7 53 24 

8 5 19 

8 22 

8 12 17 

8 2 26 

8 14 21 

8 16 7 

8 28 3 

8 26 2 

8 Z1 58 

8 r. 28 

8 45 25 

8 36 56 

8 48 53 

8 38 54 

8 50 52 

10 19 42 

10 31 47 

10 23. 24 

10 35 29 

10 35 43 • 

10 47 49 

10 43 4 

JO 55, 10 

10 57 19 

11 926 

II ^s. 50 

II 27 57 

II 20 22 

11 32 30 

3 39 20 

The oblervatlon of the vernal equinox was made at the 
gnomon. The height of this gnomon, taken- from the center 
of the hole by which the beams of the fun come in, is 1878 
lines of a French inch ; the diftance from the bottom of the 
gnomon to the equinoctial point is 1928 ; the diftance from the 
upper limb of the, fun's image to the equinodlial point was 
found 16,7 ; the diftance from the under limb 23,4 ; the dia- 
meter of the hole = 6 ; therefore the diftance from the bottom 
to the upper limbi 928 - 16,7 + 3 - 1914,3, to the under limb 
1928 + 23,4-3=1948,4; which gives the time the equi* 
uox happened the 20th of March, 5 h. 56' 52'' P.M. 

4 Obfervations 

144" M r>E Zach's Ajlronomkal Ohfervathm, 

Obfervatlons of Jupiter's fatellites at Marfellles. 




^ / *-"- 



h. . n 

April 3 

ImmerCon of the Ift fatellite at 


2 22 56 


May 19 

Imm. Ill: fat. - - 


2 48 12 


June 7 

Imm. IVth fat. was not total, but its 

light diminiflied fcnfibly withoutj 

ever difappearing ; the fky was ferine, 

and Jupiter had fix 

belts very 



Eraerfion of the 111 fatellite 


I 29 46 


]'^''y 5 

Em. lit fat. 


II 43 59 



Em. Ild fat. . ^ ^ 

9 17 28 



Em. Illd fat. - "^ >• 

9 27 13 



Em. Ild fat. 


i» 51 59 



Em. lit fat. 


10 111 



Imm. Illd fat. 


10 40 '^T^ 


Aug. 6 

Em. lit fat. 


8 21 20 



Em. Ill lar» 


10 18 49 



Em. Ild far. 


8 55 3v 


Sept. I 

Em. Illd fat. 


9 40 44 


14 Em. Ill fat-. 

- ! : , i' . 1 "1 ' r 


8 6 48 


IT is known, that the indh-ect method to calculate the orbits 
of comets in a conic fedion, by means of three obfervatlons 
given, is rendered more eafy and expeditious if there is a pofli- 
bility of drawing a graphical figure that reprefents nearly the 
orbit under confideration, by means of which the calculation 
is directed, and the required elements of the comet's path may 
be rigoroufly determined. To draw the orbit of a comet that 
moves in a parabola or ellipfis, the problem is reduced to find 
the potition of the axis and the perihelial diftance ; this por- 
tion of the axis will be determined as foon as the angle Is 
known, that the axis forms with another Hne, whofe pofition 
is given ; this line may be an ordinate to a given point ot the 
curve, or a tangent, or a radius vector, &c» The latter is to 

7 '^^ 

M. DE TjACus AJlronomkal ObfeiVc7tions. 145 

Le employed in preference, b^caufe the periheliiU dlftance being 
a conftant quantity, the angle of pofition then becomes the true 
anomaly of the comet ; but as the data of this problem are 
■only geocentric longitudes and latitudes of the comet, de- 
duced from the immediate oblervations of right afceniion and 
declination, the heliocentric longitudes and latitudes mufl 
firfl: be calculated ; but as thofe data are not fufficient, what is 
not given mud be arbitrarily fuppofed, viz. the (hortened ^\(' 
t2inQts(diJiantias cur tat as). This fuppofitionis changed and altered 
until the calculation will agree with the three obfervations, 
then the difference between two longitudes is the angle com- 
prehended between the two (hortened diftances in the planeof the 
ecliptic ; the whole reduced to the plane of the comet's orbit by 
means of the heliocentric latitude, gives the difference between 
'the anomalies comprehended by two radius vectors, the problem 
then is reduced : two radius vedors being given, with the angle 
comprehended, to find the two true anomalies, the perihelial 
distance, and the time the comet puts in running its anomalies. 
Let therefore t s =^yf reprcfent the ecliptic at an infinite dlf- 
tance ; QPR the apparent elliptical or parabolical path of a co- 
rnet; S the fun's center; P the comet's perihelion; T the place of 
the earth when the comet was firll obferved in C ; I the earth's 
place when the comet was obferved in K ; ST =r ^, S\ — ^, the 
diflances from the earth to the fun at the firfl and fecond obfer- 
vation known by aflronomical tables ; let Cm and K^ be two 
perpendiculars to the plane of the ecliptic, it will be Sm^Uy 
S« s= u the two fhortened di{lances> 

The obferved geocentric long-itude of the comet in T:^5=:arc T "v^G j 
the obferved geocentric longitude of the comet in I=ra~arc V ViJ'H; 
the geocentric longitude of the fun by tables in T~^r=arc TVy=^A; 
'the geocentric longitude of the fun by tables in Ir:^ — arc T ViJ'riBii 

Vol. LXXV. U Now 

14^ ^'^- EE Zach*s Ajlronrymlcal Ohfervattom, 

Now for the hrft obfervatlon the angle of elongation \%h -- a\ 
for the aDG:le ATG = arc AG = t 'f^-^K — t ^/5 G ^ lono-. o — lon^^v 
eornet — b — a\ 

the anqle of the animal parallax S;;2Ti=""' ' ~"' =<:' : 

the angle cf commutation wST= jg^. - ^+ (3 — <3) =y; 

from whence the heliocentric longitude of the comet =^ 

The iiime at the fecond obfervatlon in I. 
Angle of elongation =. /3 — oi ; 

Air I n ^'"'- v*^— *) '^ 
Anjrle or annual pa^-allax g — ; 

Angle of commutation ^ = i3o^~" e +(/5 - a) ; 
heliocentric longitude of the comet in I = /3 — 1 8o° + (p = ^ 7 
putting now the heliocentrie latitude feen from S = /^ ;- 
the geocentric latitude feen from T — /;.; 

17 1- • 1 • T '11 1 fin. /". tane. / , 

the heiiQcentric latitucie will be •-, - •' , ■ \ :=: tans:. ^ ; 

7 r • 1 Tr • "11 1 fin ® . tan<r. ^ i i* 

the lame with li« it wiii b€ — . ' ^ ■ ^ ■" - =-• tanp". y. heliocentna 

iin. (i3 — Ji) ° 

latitude in K. 

Having thus determined th-e heliocentric latitudes of two 
obfervations, the radius ve6lors will eahly be found in the fup- 
polition made for the fhortened drllances, for they are in the 
lame ratio to the radius veftors as the coiine of the heliocen- 
tric latitudes are to the radius = i ; therefore the radius ve6toF 

m of the firfl:. obfervatlon willbe=:~.- and the radius ve6lor of 

col,. ,4 

the fecond obfervatlon u — ——- . 

' col. y. 

Taking: now the difference between the found heliocentric 
longitudes, we get the heliocentric motion of the comet upon 
the ecliptic between two fliortened diflances, which is to be 
redu-ced upon the comet's orbit, this heliocentric motion Is 
tjiercfore 7 -.§■ =^ /^. Now to reduce this motion we have, firfl-, . 


li'L l>E Zacu's Aft ronomicjl Qi)ft;rv£tt ions, 14.7 

lliius totus = I is to coliiie .-7; :: as cotangent k is to the tan- 
gent of an angle which 1 put = ;7, and 90° - i -p /Z will 
give an angle which I put = q, Luflly, the analogy 
cof. « : cof. q :: fin. k ; w^ili giv^c the cofme of an angle if/, 
wliich is the requircu motion upon the orbit, or the angle 
compreheaded between the two radius vectors w and ^, l.t't 
therefore ECPMND be the apparent parabolic path of a comet ; 
S the lull's center; ]\'I and N two places of the comet, the angle 
MSN equal to its motion in longitude, or thie comprehended 
■angle if/ ; P the perihelion ; it is required to find the two ano* 
malies PAI, PN, that is, PSM and PSN, the perihelial dif- 
tance SP, and the time the comet employed to come from its 
perihelion P to M and N. 

:SM = 7n 


MSN - ^ 
NSB := .V 


Parameter =p 

In the right-angled triangleSMRand SNVwe have 
MR = OS";;/fin. (4.=t:.v) N V =: QS=:^ fm. .r; 
therefore OP— Ip — m (fin. 4^ — -^0 ^^^^ PQ^ 
\p^lJi.{\Vi.x\ but by the natureofthe parabola 
w^ehaveSMz:.AP^POaiidSN:=AP + PQ;thatis 
V2':=,\p — m (tin. ipzt.v) 1^,= ipz:izf4, fin. .v , 

m + m (fin. 4^=tzx^ ~ip f^ — H' ^^^^' ^~i P 
/;/ ( I + fim ij;±.v) rr {p ^.t (l rp fm. x') =lp 

Slid I -f fin. (iLdr.v")— -^ I =i= fill. X := ~\hY 

putting Into a fum i + fin. (4/ — a*) + i t±rfin. .v t=: — +3^ ; reduc- 
tion made 2^fin. x ^(\i\. (iP'^t^v) = ^-^-7-^) p ; but by trigono- 
metrical formulae we have (in. (ij;— .v)=:lui. 4^ cof. ATrtrfin. x 
^of. ip. Subftituting this exprefTion in its place we obtain, 

2 ^ fin. x-\- fin.ip cof..Vrt:fm . x cof.vl' = ( ^~ — ^ j />. By the fame 
formulas we have cof.- x—i^ fm.^ a; and cof. x — s/\ -lin. 

U 2 




M, DE Zach*s /IJirGnonncal O!)fervatlons. 



























r. S 








*— I 






H D 












:=: bD 






^ ^ ^ 















C d 
O « 



iJ<f. DE Zach^s JJlronomical Obfervatiojis, 

14 f 



«— ■ 

























■" -5 ^ 



i> ' — - 

O S- 



















»— « 








o ^ 




r • 

<— 1 

























^ .2 

■^ ^ 
*- t 

bI3 <45 


3 II 












XTO M DE Zacii's AJlrcnomlcal Ohferja'/iQtu-, 

The angle .v defines tlierefore the pofitlon of the axis and 
the two anomalies required, the perihelial diftance being 
_^ -= 2^:±: 2^7, lin. .v, it will be known alto by the angle .v. 

In order to find the thne the comet emplovs in runnino' its 
anoinalies, let the perihelial dlftatice jnd: now invefl:igated^/> be 
equal to the radius of the earth's orbit, the parabolic area 
i\vept by the radius vector will be by the nature of the para- 
bola ! PQ X OM 4- 1 SO X QAI :=. :^- ^ ^ ^^^ + ^so x OM ^ ^^^^ 

. 44 

44, r. 22 

tlie periphery of the earth's orbit is j \ 2Z \: 2p '. ~p\ 

therefore the whole area -p.lp—~— p^. It is known that the 

velocity of a heavenly body moved in a circular path, is to 
the velocity in a parabolic path in the ratio v/2 : i. If the pa- 
rabolic area -of the comet is divided by s/z it comes out 
^ A equal to an area that the earth -deicribes 111 

the very fame time; put therefore A equal to the time of a 
fidereal year, we (hall recover the analogy ; the whol-e area of 
the earth's orbit is to the time in which it is defcribed as the 
parabohc area is to the time con fumed in fweeping it ; therefore 

-If , A :, j4j^-^ 3SOIMO . 7A(4l-O + 3S0)MO. ^^^ Qj^j^ 
7 6v^2 ^ 'jip^'^z 

SM . fin. anom. PSM and OS =: SM . cof. anom. PSM ; let 
the anomaly he — S, we have OM=:/7/ fni. ^, and OS z=:}?i cof 5; 
therefore PO ~ p — m cof. ^. SublVitutlng we obtain 

i — ^-^ — — = which IS - — -^ =i — ■ , 

'thereby the time is found in parts of a fidereal year. 

I am, &c, 


^M, DE Zacii*s Afirtnomlcal Ohfervji'ioni, T'5'i. 

SIR, Lyons, >:f,y 4, i)3j. 

Lately 1 recelveJ from the Obfervatory at Marlllllcs.the 
oblervatlon of the tranfit of Mercury, which happened the izrii 
Nov. 1:82. The fkv not beuijr verv favourable, only the two in- 
tcrnalcontafls were obferved ; the firfl: internal conta£l was oh- 
iervcd by M. St. Jacques df, Sylvabelle, at 3 h. 18^ 30'^^ 
apparent time ; the lafl internal contact by M. St. Jacques, at 
4h. 33^ 16'"; by M. Bernard, his Adjunclns, at 4 h. 29' i^'\ 
The neareH- diftances of Mercury's limb to that of the fun in. 
the northern part of its diik were at 


3 dZ 14' 

51 ^ 

3 42 SI 

. 34 > 

4 22 I J 

^9 . 

parts of the micrometer. 

The apparent diameter of the fun was 2174 parts of this mi- 
crometer : I fuppofe the before-mentioned 2174 parts— 32-^ 
26^^,9. I conclude farther, by the obfervations, the middle of 
the tranfit at 3 h. 54^ ''/\'^S-> ^^^J^r^^s I fix, by interpolation, 
the diftances of the limbs at 3h. 54^ 7^^,2:5 = 35^'', 6 ; I have 
therefore femi-diameter of the fun =: 16' 13^,4-35^^,6 =: 
15^ 37'''?8 + femi-dlameter of Mercury = 6^^ := 15^ 43'^8 ^rtO'the 
leaft diflance of centers of the fun and Mercury. By M. de. 
la Lande's tables it is 15'' 42'',. only a ditFerence of \'\%. 

M. Wallgt at Paris has obferved this tranfit at the Royah 

Firfl: external con ta:f): 2 56 28 

Firfl internal conta(ft 3 '^ 3. 

Second - - 4 ^7 18 

Second external - 4, 22 53. 
5.^ lonl/- 

152 M. deZach's AJlronomkal Objerv^Uions, 

I only add an important remark upon the diameter of Mer- 
cury, which the aftronomers fuppofed in this tranfit=: 1 1^\ 

Let ABC reprefent the fun's di(k ; in P an external in Q^an 
internal conta(fl; ANC the apparent path of Mercury over the 

Thefemi-diameterof the funir 972''^, this of Mercury in our 
fuppofitionrr6^% MN = 942'^ the leaft diftances of the centers. 
In the right-angled triangle MNP it is MP :=: 972'' -f 6'' = 978'', 
MQ = 972''^-6''r=966''; therefore NP will be foundr:26o'' 
and NQr: 2 1 o^'' : now NP— NQ=PQ^r: 50", which converted 
into time gives 8' 14^^ for the time the diameter of Mercury em- 
ployed to run over the limb of the fun ; but by the obfervations 
of M. Wallot I find this time conflantly in both contacts 
5' 35^^ > therefore 8' 14'' : 12'' :: 5^ 35'^ : 8^^137, which 
{hould be the diameter of Mercury ; and indeed M. Wallot, 
by an immediate meafure, taken with an excellent wire-micro- 
meter, finds this apparent diameter not greater than 9'^, which 
fufficiently fhews that this diameter fuppofed 7'' ia the meaa 
4iltance is alfo too great, 

I am, &c. 

P/i,l,:<.T>ri ru.lW.l.XXI : Tab.V I .// 


[ ^53 ] 

IX. Obfcrvatlons of a new Variable Star. -By John Goodrick6, 
Efq.\ communicated by aS/V H. C.-Eiigldkld, Barf. F. R, S^ 
and A. S. 

Read Jannary 27, 1785 


**^.l ^HE account that has been lately given of the regular 
variation of Alfrol's liRht, and the notice aflronomers 

'&^" " " t) 

DEAR SIR, York, Jan. 10, 178^. 


have been pleafed to take of it, are well known. It is natural 
tiierefore to fappofe, that the relation of other fimilar pheno- 
mena may alfo meet with the fame flivourable reception. Of 
tnis kind is the following, -^hich I begthe faveur of }^ou to 
^prefent to the Royal Society. 

On the I oth of September, 1784., whilfl: my attention was 
diredled towards that partof the lieavens where /3 Lyne was 
lltuated, I was furprifed to find this ftar much lefs bright than 
iifual, whereupon I fufpedted that it might be a variable flar : 
my fufpicions were afterwards confirmed by a feries of obfer- 
vations, which have been regularly continued fuice that time, 
and which will pvefently follow in their proper place. At firll: 
Lthought the light of this flat fubje(5l to a periodical variation 
•of nearly yFv days and nine hmirs^ though the degree of 'its di- 
minution did not then appear to be conftant ; but now, lipon a 
-more clofe examination of the obfervations themfcives, I am 

V^L.. LXXV. X inclined 

1^4 ^^' Goodricke's Obfervations 

inclined to think, that the extent of its variation is twelve days, 
and nineteen hours, during which time it undergoes the fol- 
lowing changes. 

1. It is of the third magnitude for about two days. 

2. It diminilhes in about one day and a quarter. 

3. It is between the fifth and fourth magnitude for lefs than 
a day. 

4. It increafes in about two days. 

5. It is of the third magnitude for about three days. 

6. It diminishes in about one day. 

7. It is fomcthing larger than a ftar of the fourth magnitude- 
for little lefs than a day. 

8. It increafes in about one day and three quarters to the firft 
point, and fo completes a whole period. 

Thefe eight points of the variation are perhaps inaccurately 
afcertained ; and indeed it cannot be expelled to be otherwife in 
eflimations of this nature, where it is very poffible to err even 
feveral hours. 

The relative brlghtnefs of jG Lyra;, at its obfcuratioii in the 
third and feventh points, is nearly as follows. When in that of 
the third point, it is lefs than ^and x, and nearly equal to 
^ Lyras ; and when in that of the feventh point, it is rather 
lefs than J and 5 Herculis, and much brighter than ^, jc, and 
2 Lyras. At its greatefl: brightnefs in the firfl: and fifth points^ 
it is fometimes brighter than y Lyrae, but lefs than /3 Cygni,. 
and fometimes only nearly equal to it 5 but in thofe points it 
fcems to alter in its brightnefs feveral times in the fame night,, 
and that generally in a pretty confiderable degree. However,, 
this may perhaps be only owing to fome fallacy of obfervation ; 
for I have often perceived, that the relative brightnefs of ftars 
is affeded not only by the different flates of the air, but alfo by 


t>f a new Vatiable Star,.^ 155 

their change of poiitloii occafioned by the earth's diurnal 
motion, and that particularly in ftars of a great altitude. 

The magnitudes of the ftars, to which /3 Lyrce was com- 
pared during the progrefs of its variation, are as follows. 
/3 Cygni and y Lyrae of the third magnitude ; | and 5 Kerculis 
of between the fourth and third magnitude ; Herculis is 
fomething lefs than a ftaf of the fourth magnitude; ^, k, audi 
^ Lyr;£ are ftars of between the fourth and fifth magnitude, if - 
hot nearer the fifth. The relative brightnefs of thefe flats 
follows the order in which they are fet down. 

Ohfervat'ions of ihe brlghtnefi and magnitude of 13 Lyrae. 

1784, Sept. 10. At 1 1 h. =*=, much lefs than y Lyras; 
nearly equal to, if not rather brighter than f, x, and S Lyras, 
and not fo bright as |, ^, and c? Herculis ; between the fourth 
and fifth magnitude, 

Sept. II. At 8| h. nearly the fame as it was lafl night, if 
not brighter; indifferent obfervation. 

Sept. ,12. At 8| h. and ph. between the third and fourth 
magnitude ; lefs than y Lyras, brighter than 5, |, and Her- 
culis, and much brighter than f, jc, and S Lyrae. Mr. E. 
Pi GOT T agrees with me nearly. 

Sept. 13, 15, 18, 19, and 20. It was at or near its greateft 

Sept. 23. At yi h. it was nearly eqjual to ^, x, and Lyrae, 
and much lefs than ^, 9, and HercuHs. 

At io| h. the air being extremely clear, Icompared it more 
attentively to the neighbouring ftars, and found it as follows : 
rather a little brighter than $, a little lefs than f, and rather 

X 2 lefs 

3.-56"' A//'. -Goodricke's Obfcr'uattons 

kfs thaii >i LyrEc. Mv. B. Pigot-t thought it had rather in- 
cceafed from 8| to 1 1 h. ' ; 

•Sept. 24, At i3-ll>. certainly- brighter than it was lafc nighty 
but intervening clouds precluded all further obfervation. 

Sept. 28. At i.ah. not quite fo- bright a-s 7 Lyrye, but rather, 
brighter than Q a?id | Herculis. Mr. E. Pigott thought it* 
nearly equal to '}/,l.jr{f. . . . 

Sept. 29. At-ji h. not lobright a-s-^ Lyrs*.- 
At 8f h-. to TO'I h. nearly equal to | and Q IlercuHs; but ifi 
any thing it feenned rather lefs- than f, and rather. hi-igliier.thaii. 
^: about the fourth n^aG[nitude. 

At 1 1 5 h. to -izi b. the fame, if notlefs ; I could not compare 
it welt to J and'^, becaufe they were low ; moon-light, bu-t the 
air was clear. 

Sept. 30. At7h. rather lefs than ^, if hot equal Jro it; a 
iittle- lefs than 1^ and; brighter than Herculis r about the- 
fourth magnitude. ' *' '^ " 

At II h. and 125 h. it feenied to be on- its ihcreafc, beinir 
for the-moft'part larger th'an J and '5 Herculis-. 

061. 1 and 2. About its greatefl: brightnefs, but lefs than* 
^''fcyVi'.'" Mi". E.' PlGOTT thoug-ht it brighter on the 2d 
than on the if!:, being on the 2d' nearly equal^ to ^Eyras. '" '"'" 
Oct. 4. At lorh. I thought it rather lefs',. but'-the weather- 
was hazy. i'ot)i^i 
Oct. 5. At 6| h. not fo bright -as J' and '^ Herculis ; a little - 
brighter than ^, and brighter than ^ and k Lyrie ; air clear. 

At 9! h. nearly- equal '.0 ^, and a little brighti^r than §and ?& 
Lyra;. • 

At I2i h. a little lefs than ^, nearly equal ta >«, and rather a 
little brighter than I .yra' ; between the fourth tind fifth mag- 
nitude ; air very clear» 

5: ^ oa 

of a neis) Variable Star. '.i-:;rj 

Odl. 6. At hi h. and 7I h. Ids than f and y., and a little lefs 
diaii ^ Lyriie;- between tlje filth and fourth magnitude. 

Oct. 7. At 6| b. between the tourtli' and tlurd magnitude.; 
a little brighter than ^, and nenrly Herculis ;. much 
brighter tlian f, ;c,, and ^ Lyra: ; 1 obierved'k tiii \zk ii- when 
it was certainly increaled. 

At '/iho. Mr=,E. PiGOTT thought it. brighter than J and 5 

Odi. 8. At S b. nearly equal' to- 7 Lyr^e ; on account of' tlie 
intervenin-g clouds,, I could not- perceive- which, was largeft ; 
third magnitude. .-. 

.061.. 9.- At. 7 h, rather lofsthan y Lyn^; 

■ Ocl. 10.. At ^h. .i-iih. aiid 12 h. nearly equal to 7, if 
-not rather lefs. , 

Oct. II.. AtSh. I oh. and i'2 hv rather lefs than y;. sat 
I 2 h. if any difference, lefs than it was lafl: night. . -i 

0.(£l. 15.. At 8. h.=i^ nearly equal, to, though rather lefs 
than, 9/ Lyne. 

, 06t 1 6 . hx. 6 1 . h . . and 9 1 .h . , little lefs .than .7, if- not ecjaal 
•to it . . 

At 1 1 h. rather larger than <j^, but^ th-e weather- was> fogjxv-, 
Mr. E. Pi GO T T agrees Avkh me in- both obfervation s. 
- 0(51:. 17,. At 6i hJand 7 h* fomewhat lefs than y Lyrir-. • 
t' Qdi, 18. At 6| h. between the fourth anxl fifth magnitude; 
brighter than k and ^, and rather brighter than ^Lyra^; good 
obfervation. - 

At 9|.h. I i thought it was decreafed, being, equal to f anoi 
rather brighter than ?<: Lyrae. Mr. E. Pigott alfo thought it 
was decreaiing. 

Od. 19. At 6| h. it was rather lefs than ^ and ?tj and 
brighter than I Lyrasi 

■ '#/ At? 

15^ ^'^f* Cjoodr ick e's Obfervaiions 

At 8| h. nearly the fame, if not Increafed, 

Ode. 20. At 6 1 h. rather brighter than J and 5 Herculls,, 
and between the fourth and third magnitude. ' 

At 8| h. and 1 1 h. I thought it \vas increafed, but it was 
lefs than y Lyrae ; between the third and fourth magnitude. 

0£t. 22. At 6 h. 8 h. and 9 h, nearly equal to y Lyrae. 

Od. 23. At 6 h. 8 h. and 1 1 h. rather lefs than y, though 
nearly equal to it. 

Odi. 24. At 62 h. and 1 1 h. lefs than y Lyrae, and brighter 
than J and Q Herculis; at 8 h. Mr. E. Pigott thought it 
rather lefs than y Lyrac. 

05:. 25. At 6 h. 8 h. and 1 1 h. nearly, though perhaps not 
quite equal to ^ Herculis ; lefs than J Herculis, and brighter ' 
than ^ and I Lyrac; about the fourth magnitude. At 6| h» 
Mr. E. Pigott thought it rather brighter than Q and 

061. 26. At 6 h. and 1 1 h. brighter than Q and Herculis, 
but lefs than y Lyrae. 

Odi, 27. At 6 h. and 8| h. brighter than it was kft night, 
but ftill lefs than y Lyrae ; much brighter than J and 6 Her* 
culis ; the moon was at its full. 

061. 28. At 8 h. it rather lefs than y Lyrae. 

0£l. 29. At 91 h. nearly equal to, though rather brighter 
than y Lyrae ; I faw them but for a (hort time on account of 
clouds coming on. 

0(5t. 31. At 8 h. between the fifth and fourth magnitude; 
lefs than f and h, and brighter than ^ Lyrae. Mr. E. Pigott 
thought it equal to ^ Lyrae at 8| h. 

Nov. I. At 6ih. between the fourth and fifth magnitude; 
tather brighter than f, and brighter than )c and ^ Lyrse. 

Nov. 3, At 5i h. little lefs than y Lyr«, 


of n new Variable Star. 1551 

Nov. 6. At 8 h. rather lefs than y Lyrae, and brighter 
than 5 Herculis. Mr. E. Pigott thought it nearly equal to y 

Nov. 7. At 7 h. and io| h. much lefs than y Lyrae; 
nearly equal to, if not rather brighter than, Q Ilerculis, and 
rather lets than J Herculis; between the fourth and third mag- 

Nov. 10. At io| h. nearly equal to y Lyi'ae. Mr. E. 
Pigott thought it not quite fo bright as 7 at 1 1 h. 

Nov» II. At 5I h» and 7 h. a little brighter than y Lyric ; 
afterwards I rather thought them equal, though Q> appeared 
for the moft part fomething brighter. At 1 1 h. and 12 h. they 
appeared nearly equal. At 7 h. Mr. E. Pigott thought it was 
lefs than y, if there was any difference. 

Nov. 12. At 6| h. 81 h. and 10 h» much lefs than 7/ Lync, 
but brighter than £ and Q Herculis ; between the fourth and 
third magnitude. 

Nov. 13. At 6| h. and loh. equal to, if not rather lefs 
than f, lefs than ;c> and brighter than ^ Lyrae ; between the 
fifth and fourth magnitude. At 5I h. Mr. E.. Pigott thought 
it rather brighter than ^ Lyrae. 

Nov. 16. At 7I h. little lefs than y. At loh. certainly a 
little brighter than it. 

Nov. 17. At 6 h. rafiher brighter than y. At 8^ Ii. 9I h. 
and loi h. brighter than y^ and lefs than j3 Cygni. 

Nov. 18. At 9 h. 10 h. and i^h. juft the fame. 

Nov. 19. At 6 1 h. and 8 h, lefs than y Lyrx, and brighter 
than 6 and | Herculis ; between, the third and fourth magnitude-. 
At 10 h. fomething brighter than 5 Herculis. 

Nov. 20. At 7 h. 8h. and loi h. rather lefs than |, ancf 
rather brighter than Q Herculis ; between the fourth and third 

^ magnitude^ 

t€o Mr, Gooduicke's Obfervatwns 

inap^aitude. At i8| h. I thought it-was mcreafed ; obferved in 

t-wi light. 

Nov. 21. At 7"h. fomething brighter thriii ^ and J Herculis, 

Nov. 25. At 7 h. lefs than y Lyra?, and brighter than 5 
Ilerciills ; between the fourth and third magnitude. At 9I h. 
I thought it v/as decreafed, being now of the fourth mag- 

Nov. 26. At 9:h. =h much lefs than 7/, and of between the 
fourth and fifth mngnitude ; but the weather was too hazj, 
and the moon-light too ftrong, to obfcrve well. 

Nov. 29. At 72 h. and 8 h. rather brighter than y Lyrae. 
Mr. Edw. Pigott thought it nearly equal to y at 8 h. 

Nov. 30. At 8| h. and io| h. brighter than y Lyra?, and 
lefs than /3 Cygni ; air clear. 

Dex:. 4. At 5I h. 6| h. and io|- h. lefs than 7 Lyra^, and 
brighter than 6 Herculis ; between the third and fourth mag- 
nitude. Mr. E. PiGOTT thought it nearly equal to y at 6| h. 

Dec. 9. At 8 h. much lefs than y Lyrae, and brighter 
than^Lyrie; about between the fourth and fifth magnitude. 
At 182 h. it was increafed, and nearly eqUal to Herculis ; but ' 
lefs than Q and J ; not quite of the fourth magnitude. 

Dec. 1 1. At 6 h. and 8 h. lefs than y Lyrae, and brighter 
ilian Q and | Herculis. At 8|- h. ^\ h. and i^l h. nearly 
equal to, though rather lefs than y. 

Dtc. 12. At 5 h, and 6 h. ^learly equal to 7, thougli rather- 

Dec. 13. At 51 h. and 9I h. fomething brighter than y, 

Dec. 14. At 7 h. and 8| h. rather brighter than y. 

Dec. 17. At 5! h. lefs than y Lyra% and brighter than 
S and t, Herculis. At 7I h. nearly equal to y^ though rather 


of a new Varlalk Star, 1 6 r 

Dec. 19. At 9 h. I believe It was brighter than 7, but the 
weather was not very favourable. 

At 19 h. little lefs than y. 

Dec. 20. At 55 h. lefs than y Ivvra,', and brighter tliau 
5 and I Herculls. At 6.| h. nearly equal, though rather lels 
than y Lyrct. 

Dec. 21. At 8 h. much lefs than 7, and confiderably 
brighter than ^Lyrae ; not quite of the fourth magnitude. 

At 18 h. a little brighter than ^ and jc, and brighter than J 
Lyra^; between the fourth and fifth magnitude. 

Dec. 28. At 6h. lefs than 7 and brighter than 5 Herculls ; 
between the third and fourth magnitude. At 8 h. nearly equal 
to Q Herculls ; between the fourth and third magnitude. 

1785, Jan. 5. At 5|h. about equal to ^Herculls; fourth 

Jan. 6. At 5I h. bettveen y Lyrae and 5 Herculls, but rather 
nearer y. At 8| h. It feemed a little brighter than y. 

From the above ferles of obfervations I have deduced all the 
conclufions relative to the eight points of the variation, as they 
are flated in the beginnmg of this paper. However, as at firil It 
•may not clearly appear, that the ftar has a more confiderable 
diminution in the third point than In the feventh. It will not 
be improper to add a few words relating to that clrcumilancc : 
for proof of it, therefore, I refer to an attentive coniparlfon cA 
the obfervations of Sept. 10. Sept. 23. Oct. 5- and 6. Ode, 
18 and 19. &c. correfponding to the third poliit of the varia- 
tion with thofe of Sept. 29 and 30. Odi. 25, Nov. 7 and 
19, &c. correfponding to the feventh point of the varLa- 
tlon. It may be objefted, that in fome of the obfervations of 
the feventh point, the ftar might have become flMl.more di- 
minlfhed in the Intermediate hours ; but this is not probable^ 

Vol. LXXV. Y btcauie 

i'62 Mr. GooDRicKE*s Obfervat'ions 

becaufe in that point the flar has been obferved of about the 

fourth magnitude at intervals much fhorter than in the third 

point, fo that, if it had continued to diminifli, its diminution 

would have proceeded at a more rapid rate, which ftill fhews 

that there is at leaft a difference between thefe two points. 

With regard to the period of the variation, it is evident 

from a collation of the preceding obfervations in a coarfe way, 

that it is nearly twelve days and three quarters. To determine it 

with greater accuracy is a fubje6t of confiderable difficulty, in 

the prefent cafe ; for unlefs we can obtain very exa6l points of 

comparifon, the period would come out erroneous, efpecially 

if deduced from intervals confifting. of only a very few periods, 

as is the cafe here. However, as I have been able to obtain a 

few obfervations of the middle of its obfcuration in the third 

point accurate enough for our purpofe, I have formed the fol« 

lowing calculation. 

Times of the middle of its obfcuration 
in the third point. 

1784, oa. 6 
— 18 
oa. 18 





only a fingle period of 









two periods, 

each of 



— 3^ 

oa. 6 

- 31 

Hence the period on a mean is 1 2 1 9 :±: 
In afcertaining the above times, I attended particularly to 
the neareft obfervations both preceding and following. In the 
manner above ftated the period may alfo be deduced from the 
middle of its obfcuration in the feventh point ; but as thefe 
obfervations are not fo exaa as the above, I Ihall only, as a 


of a new Variable Star, 16-' 

further confirmation, compare two of the mofl: di^ant of 
them, v'i%. Sept. 29. 22 h. and Nov. 20. 6 h. which interval I 
find contains fix periods, each of 12 d. 20 h. ~. 

I have it in my intention to pUrfue the fubje£l further, and 
when I have got a fullicient number of obfervations, it will 
be eafy to determine the period with greater exadnefs, and 
alfo at the fame time to afcertain the other particulars of the 
variation with more precifion. in the mean while I wifli that 
this account may be confidered as being yet imperfect ; but I 
was induced to fend it in its prefent ftate, in hopes that other 
aftronomers may contribute by their obfervations to the eluci- 
dation of this phicnomenon. 

As /3 Lyrae is a quadruple ftar, N° 3. of Mr. Herschel's 
Vth Clafs of Double Stars *, I was defirous to fee if any of 
the fmall flars near it would be afFe(51:ed by its different changes ; 
but they feemed not to fuffcr any alteration, either when it 
was at its greatefl or at its leafl brightncfs. I attended to this 
the more particularly becaufe the lofs of the flar's light was 
very confiderable, and thephaenomenon feemed to be occafioned 
by a rotation on the ftar's axis, under a fuppofition that there 
are feveral large dark fpots upon its body, and that its axis is 
inclined to the earth's orbit. 

I muft not omit mentioning here that Mr. Herschel, 
amongfl thofe ftars v/hich he fuppofes to have undergone an 
alteration, reckons (3 or y Lyrae ; becaufe he obferved that y was 
much larger than (3, whila Flam^teed marks both of the 
fame magnitude -f*. It may alfo be added, as fliewing that (3 
Lyrae varied in former times, that Hevelius, in his Catalogue, 
differs from Flamsteed, and marks y of the third magnitude. 

* Phil. Tranf. for 1782, p. 147. 
t Phil. Tranf. for 17B3, p. 256. 

Y 2 and 

1 64 Mr, Goodricke's Ohfervattons of a new Variable Star, 

and /S of between the fourth and third. I have, however^ 
fome doubts whether the variation of this ftar does not entirely 
ceafe or become lefs vihble in certain years. Thefe doubts ari(e 
from fome obfervations of Cassini in Phil. Tranf. N"" y^^ 
p. 2198. where I find that in obferving the new il:ar, which, 
then appeared near the beak of the Swan, he compared it very 
fr,equently for upwards of a month to /S and y Lyr^, yet 
without perceiving, or even fufpe6i:ing, that /G was variable^ 
though it was eafy for him to have perceived it, if th^ varia* 
tion had then been even lefs than it is now.- 

I am, &c, 


[ i65 T 

X. On the Motion of Bodies affecled by FrlBion. By the Rev. 
Samuel Vince, yf. M. of Cambridge; CGmmtmicated by 
Anthony Shepherd, D. D. F, R. S. Plumia?2 Profejfor of 
Ajlronotny and experimental Philofophy at Cambridge. 

. Read November 25, 1784, 

THE fubje6l of the paper which I have now the honour 
of prefentlng to the Royal Society, feems to be of a 
very confiderable importance both to the practical mechanic 
an4 to the fpeculatlve philofopher ; to the former, as a know- 
ledge of the laws and quantity of the fri6llon of bodies in motion 
upon each other will enable him at firft to render his machines 
miore perfect, and fave him in a great meafure the trouble of 
corre£ling them by trials ; and to the latter, as thofe laws 
will furnifli him with principles for his theory, which when 
eflablifhed by experiments will render his conclufions appli- 
cable to the real motion of bodies upon each other. But, how- 
ever important a part of mechanics this fubje^l may conflitute, 
and however, from its obvious ufes, it might have been ex- 
pe6led to have claimed a very confiderable attention both from 
the mechanic and philofopher, yet it has, of all the other parts 
of this branch of natural philofophy, been the mod neglected. 
The law by which the motions of bodies are retarded by fric- 
tion has never, that I know of, been truly eftabiilhed^ 
MusscHENBROEK fays, that in fmall velocities the fridion varies 
very nearly as the velocity, but that in great velocities the fri£lion 
.increafes ; he has alfo attempted to prove, that by Increafing 
Z the 

1 66 Mr, ViiircE on the Motion of 

the weight of a body the fridlon does not always Increafc exacftly 
in the fame ratio; and that the fame body, if by changiiig its 
pofition you change the magnitude of the furface on which it 
moves, will have its quantity of friction alfo changed. Hel- 
SHAM and Ferguson, from the fame kind of experiments, 
have endeavoured to prove, that the fri6lion does not vary by 
changing the quantity of furface on which the body moves ; 
and the latter of thefe aflerts, that the fridion increafes very 
nearly as the velocity; and that by increafing the weight, 
the friction is increafed in the fame ratio. Thefe different con- 
clufions induced me to repeat their experiments, in order to fee 
how far they were conclulive in refpe(5l to the principles de- 
dticed from them : when it appeared, that there was another 
caufe operating befides friction, which they had not attended 
to, and which rendered all their dedu£l:ions totally inconcluiive. 
Of thofe who have written on the theory, no one has efta- 
blifhed it altogether on true principles : Euler (whofe theory 
is extremely elegant, and which, as he has fo fully confidered 
the fubje6t, would have precluded the neceffity of offering any 
thing further, had its principles been founded on experiments) 
fnppofes the fri6iion to vary in proportion to the velocity of the 
body, and its preflure upon the plane, neither of which are 
true: and others, who have imagined that friftion is a uni- 
formly retarding force (and which conje61:ure will be confirmed 
by our experiments), have ftill retained the other fuppofition, 
and therefore rendered their folutions not at all applicable to 
the cafes for which they were intended. I therefore endea- 
voured by a fet of experiments to determine, 

I ft, Whether fri^ion be a uniformiy retarding force, 

2dly, The quantity of fiidlion. 

Bodies affeSed by FriBion, . 167 

^dly, IVheiher the fridVion varies in proportiofi to the prejfure 
ar weight, 

4thlv, Whether the JriBion be the fame on whichever of its fur- 
faces a body moves. 

The experiments, in which I was affifled by my ingenious 
friend the Rev. Mr. Jones, Fellow of Trinity College, were made 
with the utmoll: care and attention, and the feveral refults 
agreed fo very exa6ily with each other, that I do not fcrnple to 
pronounce them to be conclufive. 

2. A plane was adjufted parallel to the horizon, at the extre- 
mity of which was placed a pulley, which could be elevated or 
deprefled in order to render the firing which connecled the 
body and the moving force parallel to the plane. A fcale accu- 
rately divided was placed by the fide of the pulley perpendi- 
cular to the horizon, by the fide of which the moving force 
defcended ; upon the fcale was placed a moveable flage, which 
could be adjufled to the fjpace through which the moving force 
defcended in any given time, which time was meafured by a 
well regulated pendulum clock vibrating feconds. Every thing 
being thus prepared, the following experiments were made to 
afcertain the law of fridlon. But let me firfl obferve, that if 
fri6lion be a uniform force, the difference between it and the 
given force of the moving power mufl be alfo uniform, and 
therefore the -moving body muft defcend with a uniformly ac- 
Cfclexated velocity, and confequently the fpaces delcribed from 
the beginning of the motion mufl be as the fquares of the 
times, jufl as when there was no friction, only they will be 
diminifhed on account of the fri£lion. 

3. Exp. I . A body was placed upon the horizontal plane, 
and a moving force applied, which from repeated trials was found 
to defcend 52! inckes in 4'^ for by the beat of the clock and 

7 the- 

1 68 . ^' Mr. ViNCE on tie MoUon of 

the found of tlie moving force when it arrived at theflage.. the 
fpace could be verj accurately adjufted to the time ; tlie ftage 
v/as then removed to that point to which the moving iorce 
v/ould defcend in 3'^, upon Aippohtion that the ipaces defcribed 
hy tlie moving power were as the fquares of the times ; and the 
fpace was found to agree very accurately Vvith the time ; the 
ftage was then removed to that point to which the moving 
force ought to defcend in 2'', upon the fame fuppofition, and 
the defcent was found to agree exactly with the time ; iaftly, 
the ftage was adjufled to that point to which the moving force 
ought to defcend in \'\ upon the fame fuppofition, and the 
fpace was obferved to agree with the time. Now, in order to 
find whether a difference in the time of defcent could be ob- 
ferved, by removing the ftage a little above and below the pofi- 
tions which correfponded to the above times, the experiment 
was tried, and the defcent was always found too foon in the 
former, and too late in tlie latter cafe ; by which I was affured 
that the fpaces Hrft mentioned correfponded exactly to the 
times. And, for the greater certainty, each delcent was repeated 
eight or ten times.; and every caution ufed in this experiment 
was alfo made ufe of in all the folio wins;. 

Exp. 2, A fecond body was laid upon the horizontal plane, 
and a moving force applied which defcended 41 1 inches in 3'''' ; 
the ftage was then adjufted to the fpace correfponding to z'\ 
upon fuppofition that the fpaces defcended through were as the 
fquares of the times, and it was found to agree accurately with 
the time ; the ftage was then adjufted to the fpace correfpond- 
ing to i^\ upon the fame fuppofition, and it was found to agree 
with the time. 

Exp. 3. A third body was laid upon the horizontal plane, and 
amoving force applied, which defcended 59^ inches in 4'^; the 


bodies qff'ecied by Friolf on* ' ' l6^ 

flage Was then adjufted to the fpacp conelponding to 3'', upoti 
iuppofitioii that the fpaces defcended through were as the 
fquares of the times, and it was found to agree with the time ; 
<the ftage was then adjufled to the fpace correfponding to 2'% 
upon the fame fuppofition, and it was found to agree with the 
time ; the ftage was then adjufted to the fpace correfponding 
to i'\ and was found to agree with the time. 

Exp. 4. A fourth body was then taken and laid upon the 
horizontal plane, and a moving force applied, which defcended 
'^^ inches in 4^'; the ftage was then adjufted to the fpace 
through which it ought to defcend in 3'', upon fuppofition 
that the fpaces defcended through were as the fquares of the 
times, and it was found to agree with the time ; the ftage was 
then adjufted to the fpace correfponding to 2^\ upon the fame 
fuppofition, and was found to agree with the time ; laftly, the 
ilage was adjufted to the fpace correfponding to i'\ and it was 
found to agree exactly with the time. 

Befides thefe experiments, a great number of others were 
ttiade with hard bodies, or thofe whofe parts fo firmly cohered 
as not to be moved inter fe by the fri£lion ; and in each experi- 
ment bodies of very different degrees of friclion were chofen, 
and the refults all agreed with thofe related above ; we may 
therefore conclude, that thefriSlion of hard bodies in motion is a 
uniformly r etar ding for ce^ 

But to determine whether the fame was true for bodies when 
covered with cloth, woollen, &c. experiments were made in 
■order to afcertain it ; when it was found in all cafes, that the 
retarding force Increafed with the velocity j but, upon covering 
bodies with paper, the confequences were found to agree with 
thofe related abovft 

Vol. LXXV, Z 4. Having 

I "o M'\ V J NCE on the Mouon of 

4, Mavliig proved that the retarding force of all hard bodies 
ariiing trom trittion is luiiform, tlie quantity of fridion, con- 
fidered as equivalent to a weight without inertia drawing the 
body on the horizontal plane backwards, or a<fling contrary to 
the moving force, may be immediately deduced from the fore- 
going experiments. For let M = the moving force expreffed by 
its weight; Fi=the fricflion ; W=rthe weight of the body 
upon the iiorizontal plane; S = the fpace through which the 
moving force defcended in the time t expreHed in fecotids ; 
r=i6-j-a feet; then the whole acceitrative force (the force of 

gravity being unity) will be ^^ 7" y hence, by the laws of uni* 
formly accelerated motions, ■ , - x rr — S, confequently 

F — M — - ^ "^ . z^ . To exemplify this, let us take the cafe of the 

laft experiment, where Mz=7, Wr: 25I, 5=4/^ feet, i^^^'i 

hence F= 7 -^^4^7^ = 6.417 ; confequently the fridion was 

to the weight of the rubbing body as 6.4167 to 25.75. ^'^^ 
the great accuracy of determining the friction by this method is 
manifefl: from hence, that if an error of t inch had been made 
in the defcent (and experiments carefully made may always de- 
termine the fpace to a much greater exadnefs) it would not 
have affeded the conclufion -^;-o-dth part of the whole. 

5. We come in the next place to determine, whether fric- 
tion, cceteris paribus, varies in proportion to the weight or 
preflure. Now if the whole quantity of the fridion of a body, 
meafured by a weight without Inertia equivalent to the fridion 
drawing the body backwards, increafes in proportion to its 
weight, it is manifefl:, that the retardation of the velocity of 
the body arifing from the fridion will not be altered; for the 
7 retardation 

Boiiies iijfl'tteci by Fricficn, I '^« i 

, . . Qiiantity of fiii^ion i -.-it. 

retardation vanes as -^ — ~ — 7: ; hence, it a body be r>ut 

Quantity ot matter ' / r *• 

ill motion npon the horizontal plane by any moving force, if 
both the weight of the body and the moving force be increafed 
in the fame ratio, the acceleration ariling from that moving 
force will remain the fame, becaufe the accelerative force varies 
as the moving force divided by the whole quantity of matter, 
and both are increafed in the fame ratio ; and if the quantity 
of fri£^ion increafes alio as the weight, then the retardation 
arifing from the fri6lion will, from what has been faid, remain 
the fame, and therefore the whole acceleration of the body will 
not be altered ; confequently the body ought, upon this fuppo- 
iitlon, fliill to defcrlbe the famefpace in the fame time. Hence, 
by obferving the fpaces defcribed in the fame time, when both 
the body and the moving force are increafed in the fame ratio, 
we may determine whether the fri6lion increafes in proportion 
to the weight. The following experiments were therefore 
made in order to afcertain this matter. 

Exp. I. A body weighing 10 oz. by a moving force of 4 oz. 
defcribed in 2^^ a fpace of 5 1 inches ; by loading the body with 
10 oz. and the moving force with 4 oz. it defcribed ^6 inches 
in 2"; and by loading the body again with 10 oz. and the 
moving force with 4 oz. it defcribed 61 inches in 2^\ 

Exp. 2. A body, whofe weight was 16 oz. by a moving 
force of 5 oz. defcribed a fpace of 49 inches in 3'^; and by 
loading the body with 64 oz. and the moving force with 20 oz. 
the fpace defcribed in the fame time was 64 inches. 

Exp. 3. A body weighing 6 oz. by a moving force of 2| oz., 
defcribed 28 inches in 2'^ \ and by loading the body with 24 
oz. and the moving force with 10 oz. the fpace defcribed in the 
fame time was 54 inches. 

Z 2 Exp. 

1^2 Mr. \ ijsCE, on the Motion ef' 

ExF. 4, A body weighing 8 oz. by a moving force of 4 oZo 
defcribed 33I inches in 2'^; and by loading the body with 8 
oz. and the moving force with 4 oz. the fpace defcribed in the 
fame time was 47 inches. 

Exp. 5. A body whofe weight was 9 oz. by a moving force of-" 
4I oz. defcribed 48 inches in 2^^; and by loading the body with. 
9 oz. and the moving force with 4i oz. the fpace defcribed in 
the fame time was 60 inches. 

Exp. 6. A body weighing 10 oz. by amoving force of 3 oz. 
defcribed 20 inches in 2/'', by loading the body with 10 oz.. 
and the moving force with 3 oz. the fpace defcribed in the fame- 
time was 31 inches ; and by loading the body again with 30- 
Qz. and the moving force with 9, oz. the fpace defcribed was. 
34 inches in z^/. 

From thefe experiments, and many others which it Is not 
neceflary here to relate, it appears, that the fpace defcribed is 
always increafed by increafing the weight of the body and the 
acceleratlve force in the fame ratio; and as the accelerationr 
ariiing from the moving force continued the fame, it is manifeft, 
that the retardation arifing from the fridion muft have beenr 
diminifhed, for the whole acceleratlve force muft have been in- 
creafed on account of the increafe of the fpace defcribed in the 
fame time ; and hence (as the retardation from friction varies as 

Quantity of friftion \ ,-, .. r r 'ct' • r • r r u' 

~ — T^ — ^ the quantity of fnciton increales m a lejs ratio 

Quantity ot matter J i ^ ^ -^ -^ -^ 

than the quantity of matter or weight of the body. 

6. We come now to the laft thing which it was propofed ta 
determine, that is, whether the fri£lion varies by varying the fur- 
face on which the body moves. Let us call two of the furfaces 
A and ^, the former being the greater, and the latter the lels. 
Now the weight on every given part of a is as much greater 
2 than 

B^dth affccfcd by Fn'^lion, 1 73 

than the weight on an equal part of A, as A is greater than a ; 
if therefore the fridtion was in proportion to the weiglit, CiVte^ris 
paribus^ it is inanifefl, that the fridion on a would be equal to 
the friction on A, the whole fri£lion being, upon fuch a fuppo- 
fition, as the weight on any given part of each furface multi- 
plied into the number of fuch parts or into the whole area, 
which produdls, from the proportion above, are equal. But 
from the laft experiments it has beeji proved, that the fridlion 
on any given furface increafes in a lefs ratio than the weight ; 
confequently the fridion on any given part of ^ has a lefs ratio 
to the fridion on an equal part of A than A has to a^ and 
hence the friftion on<^ is lefs than the friflion on A, that is, 
the fmalleft furface has always the leaft fridion. But as this 
conciufion is contrary to the generally received opinion, I have- 
thought it proper to confirm the fame by a fet of experiments. 
But before I proceed to relate them, I will beg leave tC'recom-^ 
mend to thofe, who may afterwards be induced to repeat them, 
the following cautioijis, which are extremely neceflary to be 
attended to. Great care muft be taken that the two furfaces- 
have exactly the fame degree of roughnefs ; in order ta be 
certain of which, fuch bodies mufl be chofcn as have no knots 
in them, and whofe. grain is fo very regylar that when the 
two furfaces are planed with, a fine rough plane, their rough- 
nefs may be the fame, which will not be the cafe if the body 
be knotty, or the grain irregular, or if it happens not to run 
in the fame direction on both furfaces. When you cannot de- 
pend on the furfaces having the fame degree of roughnefs, the 
beft way will be to pafte Ibme fine rough paper on each fur- 
face, which perhaps will give, a more, equal degree of rough- 
nefs than can be obtained by any other method. Now as the- 
proof which I have already given depends only on the motion'. 


!^4- ^'^''' ViNCE on the Motion of 

of t'he body upon the fame furface^ it is not liable to any inac- 
curacy of tbe kind which the preceding cautions have been 
given to avoid, nor indeed to any other, and therefore it niufl 
be perfectly conclufive. In the following experiments the 
cautions mentioned above were carefully attended to. 

Exp. I. A body was taken whofe flat furface was to its edge 
as 22 : 9, and with the fame moving force the body defcribed 
on its flat (ide 33! inches in 2^^, and on its edge 47 inches in 
the fame time. 

Exp. 2. A fecond body was taken whofe flat furfaCe was to 
Its edge as 32 : 3, and with the fame moving force it defcribed 
on its flat fide 32 inches in 2'\ and on its edge it defcribed 37 1 
inches in the fame time. 

Exp. 3. 1 took another body and covered one of its furfaces, 
whofe length was 9 inches, with a fine rough paper, and by 
applying a moving force, it defcribed 25 inches in 2^^ ; I then 
took off fome paper from the middle, leaving only 4- of an incli 
at the two ends, and with the fame moving force it defcribed 
40 inches in the fame time. 

Exp. 4. Another body was taken which had one of its fur- 
faces, whofe length was 9 inches, covered with a fine rough 
paper, and by applying a moving force it defcribed 42 inches 
in 2^^ ; fome of the paper was then taken off from the mid- 
dle, leaving only i^- inches at the two ends, and with thef^me 
moving force it defcribed 54 inches in 2''; 1 then took off 
more paper, leaving only I of an inch at the two ends, and 
the body then defcribed, by the fame moving force, 60 inches 
in the fame time. 

In the two laft experiments the paper which was taken off 
the furface was laid on the body, that its weight might not be 


B',d:es affi'cUd by FriClLn, 17^ 

Kxp. 5. A body was taken whole fiat rurface was to its rdge 
as 30 : 17 ; ihcfiat llde was laid upon the horizontal phme, a 
moving force was applied, and the flage was fixed in order to 
frop the moving iorce, in confcquence of which the body 
would then go on with the velocity acquired until the fridion 
had deilroyed all its motion; when it appeared from a mean of 
12 trials that the body moved, after its acceleration cealed, 
5^ inches before it flopped. The edge was then applied, and the 
moving force defcended through the fame fpace, and it was 
found, from a mean of the fame number of trials, that the 
fpace defcribed was 7^ inches before the body lofl all its motion, 
after it ceafed to be accelerated. 

Exp. 6. Another body was then taken whofe fiat furface was 
to its edge as 60 : 19, and, by proceeding as before, on the flat 
lurface it defcribed, at a mean of 1 2 trials, 54. inches, and on 
the edge 6a 1. inches, before it flopped, after the acceleration 

Exp. 7. Another body was taken whofe flat furface was to 
its edge as 26 : 3, and the fpaces defcribed on thefe two fur- 
faces, after the acceleration ended, were, at a mean of 10 
trials, 4I- and 7-%. inches refpedively. 

From all thefe different experiments it appears, that the 
fmallefl furface had always the leaf! fri£lion, which agrees, 
with the confequence deduced from the conlideration that the 
friclion does not increafe in fo great a ratio as the weight ; we 
may therefore conclude, that the friSlion of a body does not con- 
tinue the fame when it bus different furf aces applied to the plane on 
which it moves ^ but that the fmalleji furface will have the leaft' 

7. Having thus eflablifhed, from the mof^ declfive experi- 
ments, all that I propofed relative to fridion, I think it proper,. 


-176 "Mr. VlNCE 071 the Motion of 

before I conclude, to give the refult of my examination into 
the nature of the experiments which have been made by 
others ; wliich were repeated, in order to fee how far they 
were conclufive in refpe(fl to the principles which have been 
deduced from them. The experiments which have been made 
by all the authors that I have feen, have been thus inftitutedr 
To find what moving force would ^^ put a body at reft in 
♦motion : and they concluded from thence, that the accelerative 
force was then equal to the fridion ; but it is manifeft, that 
- any force which will put a body in motion muft be greater 
than the force which oppofesits motion, otherwife it could not 
overcome it ; and hence, if there were no other objeflion than 
this, it is evident, that the fri6lion could not be very accurately 
obtained ; but there is ancHrher obje£tion which totally deftroys 
the experiment fo far as it tends to fhow the quantity of fric- 
tion, which is the ftrong cohefion of the body to the plane 
when it lies at reft ; and this is confirmed by the following 
experiments, ift, A body of 'I2i oz. was laid upon an hori- 
zontal plane, and then loaded with a weight of 8 lb. and fuch 
a moving force was applied as would, when the body was juft 
put in motion, continue that motion without any acceleration, 
in which cafe the frldion muft be juft equal to the accelerative 
force. The body was then ftopped, when it appeared, that the fame 
moving force which had kept the body in motion before, would 
not put it in motion, and it was found neceflary to take off 
4I oz. from the body before the fame moving force wou^ put 
it in motion ; it appears, therefore, that this body, when laid 
upon the plane at reft, acquired a very ftrong cohefion to it. 
idly, A body whofe weight was 1 6 oz. was laid at reft upon the 
horizontal plane, and it was found that a moving force of 6 oz. 
^'ould juft put it in motion ; but that a moving force of 4 oz. 


Bodies ajfeSii'd hy FrtSilon, 177 

would i when It was jufl: put in motion, continue that motion 
without any acceleration, and therefore the accelerative force 
muft t/jen have been equal to the friction, and not when tli& 
moving force of 6 oz. was applied. 

From thefe experiments therefore it appears, how very 
conliderable the cohefion was in proportion to the fri£lion when 
the body was in motion ; it being, in the latter cafe^ almoir. 
I, and in the former it was found to be very nearly equal to 
the whole fridlon. All the conclufions therefore deduced from 
the experiments, which have been inflituted to determine the 
fridion from the force ncceflary to put a body in motion (and I 
have never feen any defcribed but upon fuch a principle) have 
manifeftly been totally falfe ; as fuch experiments only {hew 
the refiftance which arifes from the cohefion and friction con- 

8. I (hall conclude this part of the fubjcfl with a remark 
upon Art. 5. It appears from all the experiments which I have 
made, that the proportion of the increafe of the fri£lion to the 
increafe of the weight was different in all the different bodies 
which were made ufe of; no general rule therefore can be efta- 
blilhed to determine this for all bodies, and the experiments 
which I have hitherto made have not been fufficient to deter- 
mine it for the/ame body. At fome future opportunity, when 
I have more leifure, I Intend to repeat the experiments in order 
to eftabliih, in fome particular cafes, the law by which the 
quantity of friction increafcs by increafmg the weight. Leaving 
this fubje<St therefore for the prefent, I (hall proceed to eftablllK 
a theory upon the principles which we have already deduced 
from our experiments. 


i '-S Mr, ViNCE on the Motion of 


Let c^ f, g, (tig. i.) reprefent either a cylinder^ or that circular 
Jecfion of a body on which it rolls down the inclined plane CA im 
coufeqiience of its fridfion^ to find the time of defcetit and tht 
number of revolutions. 

As it has been proved in Art. 5. that the fri£lion of a body^ 
does not iiicreafe in proportion to its weight or prefllire, we 
cannot therefore, by knowing the friction on any other plane,, 
determine the friction on CA ; the friction therefore on CA can 
only be determined by experiments made upon that plane, that 
is, by letting the body defcend from red:, and obferving the 
fpace dclcribed in the firft fecond of time ; call that fpace a^. 
and then, as by Art» 3. friction is a uniformly retarding force, 
the body muft be uniformly accelerated, and confecjuently the; 


whole time of defcent in feconds will be = \/— . Now to deter-- 

mine the number of revolutions^ let j be the center of ofcillatioii^^ 
to the point of fufpenfion a * j then, becaufe no force acting at a 
can affe£t the motion of the point j, that point, notwithftanding; 
the action of the fri£tion at a, will always have a motion pa- 
rallel to CA uniformly accelerated by a force equal to that 
with which the body would be accelerated if it had no friction ;. 
hence, if 2;;^/ = 3.2-3- feet, the velocity acquired by the point s 

iii'tKe'firil: fecond will be = "^^^. - ; now the excefs of the ve- 

* a and s are not fixed points in the body, but the former always repreffenti 
that point of the body in contaft with the plane, and the latter the correfponding 
■ center of ofciIlation» 

2 loeity 

bodies aj^ediei hy TriBlon. i ^j ^j 

Joclty df the point s above that of r (r being the center) is ma- 
n.ifeftly the velocity with which s is carried about r; hence the 

velocity of s about the center ——-t\ tazn — - — y— _ ^ ^.^ , 

•^ UA CA ' 

r ^\ ^ 2WXCI3-2^XCA 2?«Xr^xCB— 2«X''^XCA 

confequentiv rs \ ra w — r : — ^ — iJiJ: 

^ J CA ;.fXCA 

p the velocity with which a point of the circumference is car- 
ried about the center, and which therefore express the force 
which accelerates the rotation ; now as za exprefles the accele- 
rative force of the body down tiie plane, and the fpaces de- 
fcribed in the fame time are in proportion to thofe forces, we 

have 2 a : CA :: ■ ttt— '• — - 

the fpace which any point df the circumference defcribes about 
the center in the whole time of the body's defcent down CA ; 
which being divided by the circumference p x ra (where 

^ = 6.282 Sec.) will p-ive^- ^ for the whole number 

of revolutions required. 

Cor. I. If a X CA = ;« x BC, the number of revolutions — o, 
and therefore the body will then only Aide ; confequentlj/ the 
friction vanifhes. 

Cor. 2. Let a^r's^ (fig. 2.) be the next polltion of ars, and 
draw / r^^ parallel to sa, then will j'/ reprefent the retardation 
of the center r arifing from friction, and a^ b will reprefent the 
acceleration of a point of. the circumference about its center; 
hence the retardation of the center : accetef^tion of the cir- 
cumference about the center :: s't : a' b :: (by fim. a's) 
ir' : hr' :: rs \ ra. 

Cor. 3. If ^^ coincides with /?, the body does not y7/^<? but 
only roll; now in this cafe s s' : rr' \\ a s\ ar\ but as ^ s' and 
r r' reprefent the ratio of the velocities of the points s and r, 

A a '2 they 

1 8o Mr. ViNCE on the Motion of 

thev will be to each other as '-^^ : 2? or as m x CB: a x CA; 

hence, when the body ro//s Without Jli ding ^ a s : a r y, m x 
CB : ^ X CA. 

Cor, 4. The tune of dcfcent down CA is=^ sJ' — » but by 

the lad Cor. when the body rolls without Jli J/ nq;. ^/ = ' — r- • 

hence the tune of defcent in that cafe —AC 4/ ^^^7^, ; now 

\ OT X r^ X BC 

the tune of defcent, if there were no friclion, would be = 

-7 , hence the time of defcent, wlien the body rol/s with- 

^w X BC ^ 

out ^fliding : time of free defcent :: K^sa : \/r a. 

Cor, 5. By the laft Cor. it appears, that when the body juft rolls 
without Jli ding, or when the fridion is juft equal to the accelera- 

tiv€ force, the time of defcent =AC\J .,,, ; now it is ma- 

' \m xra X BCl 

nifeft, that the time of defcent will continue the fame, if the 
friction be increafed, for the body will ftill freely roll, as no 
increafe of the fridion ading at a can affect the motion of the 
point J. 

If the body be projetfled from C with a velocity, and at the 
fame time have a rotatory motion, the time of defcent and 
the number of revolutions may he determined from the com- 
mon principles of uniformly accelerated motions, as we have 
already inveftigated the accelerative force of the body down 
the plane and of its rotation about its axis ; it feems therefore, 
xjnneceilary to lengthen out this paper with the iuvefligations* 

p s a- 

BoJics aJfeShd by Friciion. i § I 


Let the My be pro'iecied on an horizontal plane LM (fig. j.) 
with a given velocity to determine the through which the 
jbody ivill move bejore it JtopSy or bcjore its motion becomes latijorni. 

Case I. i. Siippofe the body to have no rotatory motion 
when it begins to move; and let ^ = the velocity of projedioU' 
per lecond measured hi feet, and let the retarding force of the 
fri£lion of the body, meal u red by the velocity of the body 
which it can deftroy in one fecond of time, be determined by 
experiment and called F, and let ,v be the fpace through which 
the body would move by the time its motion was all deilroyed 
when projeded with the velocity a, and retarded by a force F ; 
then, from the principles of uniformly retarded motion, a=i 


— , and if /^rtime of defcribing that fpace, we have / — 
- , and hence the fpace defcribed in the firft fecond of time 

= . Now it is manifeil, that when the rotatory motion 

of the body about its axis is equal to its progreflive motion, the 
point a will be carried backwards by x\\q farmer motion as much 
as it is carried forwards by the latter y confequently the point of 
eonta(ft of the body with the plane will then have no motion 
in the direction of the plane, and hence the fricflion will at 
that inftant ceafe, and the body will continue to roll on uni- 
formly without Jliding with the velocity which it has at that 
point. Put therefore s^the fpace defcribed from the com- 
mencement of the motion till it becomes uniform, then the 
body being uniformly retarded, the fpaces from the end of 
7 the: 


"1^2 Mr, ViNCE on the Motion of 

the motion vary as the fqnares of the velocities, hence 

2 2 

-^'. a (^.\ I : 2F) :: -T. ~ z : <2* - 2Fs = fquare of the progref- 

five velocity when the motion hecomes uniform ; therefore the 

velocity deflroyed by friction ~a — \/ a^ — 2F2 ; hence, as the 
velocity generated or deflroyed in the fame time is in 
proportion to the force, we have by Cor. 2, Prop. i. 

}• s : r a •.-.a — s/a" ~ 2bz \ - X a — s/a'' — z¥z the velocitv of 

r i "' 

tiie circumference efg generated about the center, conlequently 

s/a^ — 2Fz~ — X a — s/ii^ — 2b'z, and hence z— ^ 

r s as X 2F 

the Ipace which the body defcribes before the motion becomes 

2. If w^e fubftitutethis value of z into the expreffion for the 

velocity, we (liall have a x - for the velocity of the body when 

its motion becomes uniform ; hence therefore it appears-, that 
the velocity of the body, when the fr](5lion ceafes, will be the 
fame whatever be the quantity of the fri6lion. If the body be 
the circumference of a circle, it will always lofe half the ve- 
locity before its motion becomes uniform. 

Case II. i. Let the body, befides having a progreffive 
velocity in the direction LM (fig. 3.) have alio a rotatory mo- 
tion about its center in the diredlion gfe, and let v reprefent 
the initial velocity of any point of the circumference about the 
center, and fuppofe it firft to be lefs than a ; then fri«5lion being 
a uniformly retarding force, no alteration of the velocity of 
the point of contad of the body upon the plane can affecl the 
^quantity of fridion ; hence the progreffive velocity of the body 
Hvill be the fame as before, and confequently the rotatqry velo-^ 


Bodies ajfe6ied hy Fridlion, i8'i>' 

city generated by fridion will alio be the fame, to which if wc 
add the velocity about the center at the beginning of the mo- 
tion, we fhall have the whole rotatory motion ; hence there- 

ra ~~' - — __- 

fore, v + — X a — \/ a — 2F2; = ^a^ — 2F2, confequently 

«* X as^— V Xrs + ^x ri 

2F X <3i 

comes uniform. 

the fpace defcribed before the motion be- 

2. If this value of z be fubftituted into the expreffion for the 
velocity, we fhall have ~ for the velocity when the 

fri£tlon ceafes. 

3. \i v-z=:a, then 2s no, and hence the body will continue to 
move uniformly with the firft velocity. 

4. If V be greater than a^ then the rotatory motion of the 
point a on the plane being greater than its progreflive motion 
and in a contrary direction, the abfolute motion of the point 
a upon the plane will be in the direction ML, and confequently 
fridtion will now ad in the diredion LM in which the body 
moves, and therefore will accelerate \.\\& progrejjive and retard 
the rotatory motion ; hence it appears, that the progrejjive mo-- 
ilon of a body may b accelerated by fribtion. Now to deter- 
mine the fpace defcribed before the motion becomes uniform, we 
may obferve, that as the progrellive motion of the body is now 
accelerated, the velocity after it has defcribed any fpace % will 
be —s/a 4- 2F2;, hence the velocity acquired = s/a + z¥% - ^^ . 

and confequently the rotatory velocity deflroyed — x 

■ ' ' y (I — . . - ■ 

^fl^-fzFz — ^, hence v y^ s/a' -\-^^%- a — ^a' ■^■q.Yz.^ 


therefore % tz — = ^ the Ipace required, 

,5; if 

i8+ ^^^' ViNCE on the Motion of 

5. If a — 0, or the body be placed upon the plane wichoiit 

any progreffive velocity, then z — ~~~ . 

Case III. i. the given rotatory motion be in tlie direc- 
tion ^^y'; then as the friclion muft in this cafe alv/ays acl in 
the direction ML, it miift continually tend to deftroy both the 
progreflive and rotatory motion. Now as the velocity de- 
flroyed in the fame time is in proportion to the retarding force, 
and the force which retards the rotatory is to the force which 
retards the /(rijo-r^/i;^ velocity by Cor. 2. Prop. i. as r^:rj, 
therefore if 1; be to ^ as ra is to r s^ then the retarding forces 
being in proportion to the velocities, both motions will be de- 
flroyed together, and confequently the body, after defcribing 
a certain fpace, will refl ; which fpace, being that defcribed 
by the body uniformly retarded by the force F, will, from 

what was proved in Cafe I. be equal to -r. . 

2. If V bears a greater proportion to a than ra does to r s^ 
It is manifeft, that the rotatory motion will not be all deftroyed 
when the progreflive is ; confequently the body, after it ha$ 

defcribed the fpace -r,, will return back in the diredlion ML; 

for the progreffive motion being then deftroyed, and the rota- 
tory motion ftili continuing in the dire<£tion g efy will caufc 
the body to return with an accelerative velocity until the fric- 
tion ceafes by the body's beginning to roll, after which it will 
move on uniformly. Now to determine the fpace defcribed 

before this happens, we have r s : r a \\ a \ ^-^ — - the rotatory 

Telocity deftroyed when the progreffive is all loft ; hencfi 

^ - '[fiif = Vi!2zzl^llf — the rotatory velocity at that time, whiclaL 


Bod:es aff'ecJed fy Frisian, 185 

being fubflltuted for v in the lail: article of Cafe II. gives 

i,^,s--ax^ta ^^^ ^j^^ fpace defcribed before the motion become? 

ahxai" ^ 


3. If V has a iefs proportion to a than r a has to r j, it is 
manifefl, that the rotatory motion will be deftroyed before tiie 
frogrp[jive\ in which cafe a rotatory motion will be generated 
in a contrary direction until the two motions become equal, 
when the fridion will inftantly ceafe, and the body will then 

move on uniformly. Now r a \ r s \\ v '. - — - the progreflive 

velocity deftroyed when the rotatory velocity ceafes, hence 

a = ■ = progreiiive velocity when it begins its 

rotatory motion in a contrary direction ; fubflitute therefore 
this quantity for a m the expreffion for z in Cafe L and we have 

n^ -]- 2f'i X • a X a X ra — V X r s 

iii~ X ar 

i — r; — for the fpace defcribed after the rota- 

tory motion ceafes before the motion of the body becomes 
uniform. Now to determine the fpace defcribed before the 
rotatory motion was all deftroyed, we have (as the fpace from 
the end of a uniformly retarded motion Varies as the fquare of 

a axra — vxrs aXra — vX rs 

the velocity) a : —p : : -^ : — r^gr— -. — the fpace that 

could have been defcribed from the time that the rotatory 
velocity was deftroyed, until the progrellive motion would 

Have been deflroyed had the fri6lon continued to acfl ; hence 

._ ^4 

« ax ra — v xrs lav X raX rs — v^ xri^ ■, r i r • i i i 

re- HFU — 2 — — v z = the Ipace deicribed when 

21' '^r X ra 2.\ x ra ^ 

the rotatory motion was all deftroyed, hence 


rj*+ 2' J X ra X a X a- — : x 2av Xra Xrs — %?" x ri 

z^ ^^^L- + i:^ ■■ -^'whoie fpace da- 

ai xar X2\: 2.b x ra ^ 

fcribed by the body before its motion becomes uniform. 

Vol. LXXV. " B b d ->.- 

3?6 Mt\ ViNCE on the Motion of 


'The CENTER of FRICTION IS that point in the bafe of a hoiy 

mi which it revolves, into which if the whole furface of the bafe^ 
mid the majs of the body were collected^ and made to revolve about 
i'he center of the bafe of the given body, the angular velocity de- 
ft/oyed by its fridiion would be equal to the angular velocity df/Iroyed-: 
in the given body by itsfriBionin the fame time. 


To find the center of frldlion. 

Let FGIi (fig. 4.) be the bafe of a body revolving about its 
center C, and fuppofe about a, b, r, &c. to be indefinitely 
fmall parts of the bafe, and let A, B, C, &c. be the correfpond- 
ing parts of the folid, or the prifmatie parts having a^ b, c, &c. 
for their bafes ; and P the center of fri6lion. Now it is ma- 
nifeft, that the decrement of the angular velocity muft vary 
as the whole diminution of the momentum of rotation caufcd 
by the fri<£lion dirc^ly, and as the whole momentum of rota- 
tion or efFe(£l of the inertia of all the particles of the folid in- 
verfly ; X.\\Q former being employed in diminifhing the angular 
velocity, and the latter in oppofing that diminution by the en- 
deavour of the particles to perfevere in their motion. Hence,- 
if the effe6l of the friction varies as the effedl of the inertia,, 
the decrements of the angular velocity in a given time will be 
equal. Now as the quantity of fri6tion (as has been proved 
from experiments) does not depend on the velocity, the efFedt 
of the fridion of the elementary parts of the bafe a, b, c, &c. 
2 will 

iBodies affedled hy FriSlloHk 187 

^Vlll be as ^ X rtC, h x 1>C, c x cC, &c. alfo the efFc6t of the Inertia 
of the correfponding parts of the body will be as A x aC\ 
B X ^C% C X cC', &c. Now when the whole furface of the 
bafe and mafs of the body are concentrated in P, the effecl: of 
the fri(5lion will be as ^ + ^ 4- ^ + &c. x CP, and of the inertia as 
A + B + C + &c. X CP'" ; confequently a x aC -{■ b x 5C -^r c x cC 
+ &c. : T+T+TT &c. X CP :: Ax^C'" +B x bC+CxcC^- 
+ &C. : A + B 4- C + &c. x CP' ; and hence 

CP = --^ ■- - - - — — - — ^ ^^— ■— (itS=:tneluni 

a XaC -\-b X l^C + c X cC i- &:c. X A + ii i- C -\-&.c. 

of the produces of each particle into the fquare of its diftance 
from the axis of motion, T:=::the fiim of the products of each 

part of the bafe into its diftance from the center, s = the area 

s J ' 
of the bafe, / = the folid content of the body) 7^7—^. 


Given the velocity with which a body begins to revolve ahotit the- 
•center of its bafe, to determine the number of revolutions which the 
body will make before all its motion be dejlroyed^ 

-- [U hi 

■'Let the fridion, expreffed by the velbcityl.whieh' it Is kbie to' 
deftroy in th6' body if it were proiefted in a right line hoi-i'zbn^ 
tally in one fecolid,- be detefmirieid 'by' experiment, dnd cail^^F;' 
and fappofe th'e initikl velocity *of' the- center of -fri^V-ion- P t about* 
^ to be a[ "Then 'conceiving the whole fu-rfice of the bafe- ati^i 
m^fsT)f "the body to 'be- coUsfHed^ntS the'^l5?iit P,^ aft-d §^s -hks-^ 

B b 7. 

1 88 Mr,yn;cTS. on the Motion of 

hence if we put z— PC, /) = the circumference of a circle 
whole radius is unity, then will pz = circumference defcribed 

by the point P ; confequently — ^=: the number of revolutions 


Cor. It the folid be a cyllnJer and r be the radius of its bafe, 

then 2, = — , and therefore the number of revolutions 

4 ' "" X.W...WVX V.X .V..V.XV..XV...O-^^^p. 


91? ^*f«£/ //6<? nature of the curve defcribed by any point of a body 
qfcdUd by friBion, when it defends down any inclined plane. 

Let efg (fig. 5.) be the body, the points ^, r, j, as in Prop. L 
and conceive j /, r ;/, to be two indefinitely fmall fpaces defcribed 
by the points s and r in the fame time, and which therefore 
will reprelent the velocities of thofe points ; but from Prop. I. 
the ratio of thefe velocities is cxprefled by m x CB : a x CA, 
hence s t : r n i: m x CB : a x CA. With the center r let a 
circle 1; w be defcribed touching the plane LM which is parallel 
to AC at the point b, and let the radius of this circle be fuch. 
that, conceiving it to defcend upon the plane LM along with 
the body defcending on CA, the point b may be at reft, or the 
circle may roll without Aiding. To determine which radius^ 
produce r s to ;v, parallel to which draw n dy, and produce n t 
to % ; now it is manifeft, that in order to anfwer the conditions 
;4bove-mentioned, the velocity of the point x mufl be to the 
velocity of the point r as 2; :.i,. that is, %x : y x :: 2 : 1^ 
hence zyz:zyx = nr. Now zy : dt {\: ny : nd) n rx i r si 

therefore ^/=:— x%y=:— x «r, hence ^j (=:td+ds = fd-^nrzz 
4 ^^ 

ridlrt. Trruu^ I',,!. /.A:\TT,i:.,\'I[/.. /iS. 

BoMes rfff5fcd by FridfJon. iSp 

-i X «r + /;Or='^^i^X«/', confequently "^"^ — ^; i :: is '. nr :: 

(from what is proved above) /«xCB:^7xCA; therefore 
a X CA X r s + a x CA x r.v = f;2 x CB x r x^ hence r v =» 

.. ^^ " ^^{ the radius of the circle which roUina; down 
mxCH— ^xCa ^ 

the inclined plane LM, and carrying the hody with it, will 
give the true ratio of its progreliive to its rotatory motion, 
and confequently that point of the circle which coincides with 
any given point of the body will, as the circle revolves upon 
the line LM, defcribe the fame curve as the correfponding 
point of the body ; but as the nature of the curve defcribed by 
any point of a circle revolving upon a flraight line is already 
very well known, it feems unnecelTary to give the invefligation. 
By a method of reafoning, not very different, may the nature 
of the curve, which is defcribed by any point of a body moving 
"Upon an horizontal plane, and affected by fridtion, be determined. 

[ '9° ] 

XI. Ohjervatlo?2s and Experiments on the Light of Bodies In a 
State of Combujlion, By the Rev. Mr. Morgan ; comviiinicated 
by the Rev. Richard Price, LL.D. F.R.S. 

Read January 27, 1785. - - 

THE difcuflion which I now wifh to lay before the Royal 
Society is nothing more than a feries of facfls, and of 
conclafions which feem to flow from thofe fadls, and from an 
attention to the following data. 

I. That light is a body, and like all other bodies fubjedl to 
the laws of attraction. 

II. That light is an heterogeneous body, and that the fame 
attractive power operates with different degrees of force on its 
different parts. 

III. That the light which efcapes from combuftibles when 
decompofed by heat, or by any other means, was, previous to 
its efcape, a component part of thofe fubflances. 

It is an obvious conclufion from thefe data, that when 
the attra«£live force, by which the feveral rays of light 
are attached to a body, is weakened, fome of thofe rays will 


Mr. Morgan's Obfervdtions and Experhnents, &c. lot 
efcape fooner than others. Thofe which are united with theleafl 
degree of power will efcape firll, and thofe which adhere to it 
mod ftrongly will (if I may be allowed the expre(hon) be the 
lall: to quit their bafis. We may here have recourfe to a flimiliar 
fa6l, which is analogous to this, and will illuflrate it. 
If a mixture, confifting of equal parts of water, of fpirits 
of wine, and of other more fixed bodies, be placed over 
a fire ; the firft influence of that heat, to which all the in- 
gredients ar€ alike expofed, will carry off the fpirits of 
wine only. The next will carry off the fpirits of wine 
blended with particles of water. A flill greater degree of 
heat will blend with the vapour which efcapes a part of 
the more fixed bodies, till at length what evaporates will be a 
mixture of all the ingredients which were at firft expofed to 
the fire. In like manner, when the furface of a combuflible is 
in aflate of decompofition, thofe parts which are the leafl fixed, 
or which are united to it with the leafl force, will be feparated 
firfl. Amongft thefe the indigo rays of light will make the 
earliefl: appearance. By increafing the heat we fhall mix the 
violet with the indigo. By increafing it flill more we fhall add 
the blue and the green to the mixture, till at length we reach 
that intenfity of heat which will caufe all the rays to efcape 
at the fame inflant, and make the flame of a combuflible 
perfedlly white. It is not my pre fen t defign to fhew why 
the mofl refrangible rays are the firfl which efcape from a 
burning body, but to enumerate the feveral fads which feem to 
fhew, that fuch a general law takes place in combuftion ; and 
that the various colours of bodies in this flate are uniformly 
regulated by that decreafe of attradive force now defcribed. 


i(^z My. Morgan's Ohfa'vallons and Expdr'unents on 

By examining the flame of a common candle we may ob- 
fervc, that its iowefl extremities, or the part in which the black 
colour of the wick terminates, dilcharges the lead heat; and 
that, as the vertex of the flame is approached, a fucceffive order 
ot parts is paflld through, in whicii the loweft is continually 
adding to the heat of what is juft above it, till w^e come to 
the top of the flame, near which all the heat is collecled into a 
focus. i\t the loweil extremity, however, where the heat is 
inconfiderable, a blue colour may be always obferved ; and 
from this appearance, amongfi others, it may, I think, be 
fafely concluded, that the blue rays are fome of thofe which 
efcape from combuflibles in an early period of their decompo- 
fition ; and that if the decompofition could be examined in a 
period flill more early, the colour of their flame would be 
violet. By an a priori deduction of this kind, I was led to 
watch the appearances of a candle more attentively ; whence I 
found that to the external boundary of a common candle 
is annexed a filament of light, which, if proper care be 
taken to prevent the efcape of too much fmoke, will appear 
moft beautifully coloured with the violet and indigo rays. To 
the preceding inftance of a common candle many fa£ls may 
be added, which fpeak a fimilar language. If fulphur or 
asther is burned, or any of thofe combuflibles whofe 
vapour is kindled in a fmall degree of heat, a blue flame 
will appear, which, if examined by the prifm, will be found 
to confrft of the violet, the indigo, the blue, and fometimes a 
fmall quantity of the green rays. The beft mode, however, 
of (hewing the efcape of fome rays by that degree of heat 
which will not feparate others till increafed, is the following. 
Give a piece of brown paper a fpherical form, by prefling it 


■the Ll^ht of Bodies in a State of Comhufic-tu 1 93 

npon any hard globular fubftance, Gradually bring the paper, 
thus formed, to that diftance from the candle at which it will be- 
gin to take fire. In this cafe a beautiful blue flame may be feen, 
hanging as it were by the paper till a hole is made in it, when 
the flame, owing to the increafed a6lion of the air upon all. 
parts of it, becomes white, though the edges ftill continue of 
a blue or violet colour. As a confirmation of what I have 
concluded from the preceding fa£ls, it may be obferved, that 
the very flame which, when expofed to a certain degree of 
heat, emitted the mofl refrangible rays only, will, if expofed 
to a greater degree of heat, emit fuch as are lefs refrangible* 
The flames of fulphur, fpirits of wine, &c. when fuddenly 
expofed to the heat of a reverberatory, change their blue ap- 
pearance for that .which is perfe6lly white. But to gain a 
more flriking diverfity of this faft, I adopted Mr. Melvill*s 
mode of examining bodies whilfl: on fire. I darkened my 
room, and placed between my eye and the combuftible a (lieet 
of pafteboard, in the center of which I made a fmall perfora- 
tion. As the light of the burning body efcaped through this 
perforation, I examined it with a prifm, and obferved the fol- 
lowing appearances. When the fpirits of wine were fet on 
fire, all the rays appeared in the perforation ; but the violet, 
the blue, and the green, in the greatefl abundance. When 
the combuflion of the fpirits was checked by throwing fome 
fal ammoniac into the mixture, the red rays difappeared ; but 
when, by the long continuance of the flame, the 'fal ammoniac 
was rendered fo hot as to increafe, rather than diralnifh thci 
combuflion, the red rays again appeared at the perforation. If 
the fcreen was managed fo that the different parts of the 
fiame might be examined feparately, I always obferved that 
Vol. LXXV. C c - the 

3 94 ^^^' Morgah's Ohfe^vaitons and Expenmenis on 
the colours varied according to the degree of heat. At 
the bafe of the flame, or where the heat was leaft, the in- 
digo, the violet, and a very fmall tinge of the bkie and 
green appeared. As I approached the vertex of the flame, 
the rays which efcaped became mors and more numerous 
till. I reached the top, when all the rays appeared in the 
prilra. It fhould be attended to, that when the red rays firft 
made their appearance, their quantity was fmall, and gradually 
increafed as the eye in its examination approached that part 
where the heat was greatefl:. Mr. Melvill, w^hen he made 
fome of the preceding experiments, obferved, that the yellow 
rays frequently efcaped in the greateft abundance ; but this fin> 
gularity proceeded from fome circumftanccs which efcaped his 
attention. In confequence of mixing acids or falts with the 
burning fpirits, a very denfe fume of unignited particles arifes^ 
and before the rays of the burning body arrive at the perfora- 
tion where the prifra catches them, they muft pafs through a 
medium which will abforb a great part of the indigo and the 
violet. On the other hand, owing to the imperfection of tjie 
decompofition, very few of the red rays are feparated from their 
bafis, and confequently the yellow and the orange rays are 
thofe alone which pafs through the unburn t fmoke of the 

1 would now proceed with obferving, that, befides the in- 
creafe or decreafe of heat, there are other modes of retarding 
or accelerating the combuftion of bodies, by which alfo may 
be examined fome of the preceding illuftrations. 

I. A candle burns moft rapidly and brilliantly in dephlo- 
g^ifticated air. 

z» The 

the Light of Bodies in a State of Combujlion, j 9 ; 

2. The blue colour of a fulphurcous flame in pure air is 
•changed into a dazzling white. 

3. The flame of inflammable air, when mixed with ni- 
trous air, is green. It is white flrongly tinged wjth the indigo 
and violet when mixed with common air ; but when mixed 
with dephlogifticated air, or furrounded by it, the brilliancy 
of its flame is moft Angularly beautiful. 

If the preceding fa^ls prove that light, as an heterogeneous 
body, is gradually decompofed during combuftion ; if they 
prove, likewife, that the indigo rays efcape with the leaf!: hear, 
and the red with the greateft ; I think we may rationally ac- 
count for feveral Angularities in the colours of different flames. 
If a piece of paper, impregnated with a folution of copper in 
the nitrous acid, be fet on fire, the bottom and fides of the 
flame are always tinged with green. Now this flame is evi- 
dently in that weak flate of decompofition, in which the mofl 
refrangible rays efcape in the greatefl abundance ; but of thefe 
rays the green efcape moil plentifully through the unignited 
vapour and that portion of the atmofphere which feparates the 
eye from the flame. The peculiarity which I have now endea- 
voured to account for may be obferved in the greatefl perfection 
in brafs founderies. The heat in this inflance, though very 
ftrong, is fcarcely adequate to the decompofition of the metallic 
vapour which efcapes from the melted brafs. A very Angular 
flame therefore appears to the eye ; for while its edges are green, 
its body is fuch as to give the objeds around a very pallid or 
ghaflily appearance, which is the confequence of its wanting 
that portion of red rays which is neceflary to make a perfed 

C c a The 

i(j6 Mr. Morgan's Ohfervatlom and Experiments ort 

The moH fingular phenomenon attending a burning body 
iS, perhaps, the red appearance it aflumes in its lafl: ftage of 
coiribiiiLlon. The preceding fatls and obiervations may, I 
think, help us to explain it. 

1. After a body has continued to burn for fome time, its 
external lurface is to be regarded as having loft a great portion 
if not the whole of thofe rays which the firfl application of 
heat was able to feparat'e. Bat thefe rays w^ere the indigo, the 
violet, the blue, and perhaps the green. Nothing, therefore, will 
remain to be fepa rated, buttbe yellow, the orange, and the red, 
C^onfequently, the combuftion of the body, in its lafl: ftate of de- 
compolition, can afllime no other than a reddifli appearance. But 

2. Let us con-fide r the external fur face of the combuflible 
as annexed, to an inner furfaee, which may be partly, but not fo 
perfectly decompoled as itfelf : for the violence of the heat will 
be found to lelien in its effeds the nearer it approaches to the 
center of the fubftance which is expofed to it. Hence we are 
to confider the parts which are juft covered by the external fur- 
face as having loft lefs of their component light than the exter- 
nal furfaee itfelf. Or the former may retain the green rays 
when the latter has loft both indigo, violet, blue, and green. 

3. Thofe parts which are nearer the center of the body 
than either of the preceding muft, as they are further from 
the greateft violence of the heat, have loft proportionably 
fewer of tlieir rays. Or w^hile the more external parts may 
have loft all but the red, thefe may have loft only the indigo 
snd viokt. 

4» The moil central parts may be unafFeded by the heat ; 
and whenever the fire does reach thefe parts, they will imme- 
diately difcharge their indigo rays, and be decompofed in the 


the Light cj bodies in a State of Combufiion, 197 

gradual manner which I have already defcribed. A piece of 
rotten wood, whilil: burning, will exemplity and confirm the 
preceding illuftration. When influenced by the external air 
only, if examined through a prifm, no rays will be found to 
efcape but the orange and the red. By blowing upon the 
burning wood with a pair of bellows, the com bullion, 
being; increafed, will affect thofe internal parts of the body 
which were not adled upon before. Thefe parts, therefore, 
will begin to lofe their light, and a prifm will {hew the 
green, the blue, the violet, and indlgOy all appearing in fuc- 
ceffion* Appearances hmilar to the preceding may be ob- 
ferved in a common kitchen fire. When it is fainted:, its 
colour is moll: red, the other rays having been emitted, and 
the combuftion at a fland ; but by blowing upon it in this 
ftate, its brightnefs will be increafed, and more and more of 
the rays which are yielded by the internal parts of the body 
will come to the eye, till at length, by continuing to blow, the 
combufiion will be made fo complete as to yield all the rays, 
or to make it appear perfectly white. 

Many are the varieties difcoverable in the flanies and In the 
appearances of fixed burning bodies to which the preceding 
obfervations may be applied ; but, to avoid unnecefl'ary amplifi- 
cation I will take notice only of what appears to me an imper- 
fedion in Sir Isaac Newton's definition of flams. He con- 
je6i:ures, that it may be a vapour heated red-hot. I think I 
fliould rather fliy, that flame Is an inflance of combufiion 
whofe colour will be determined by the degree of decon.ipofi- 
tloii which takes place. If it be very imperfe^l, the molf 
refrangible rays only will appear. If it be very perfe<5l, all 
the rays will appear, and its flame will be brilliant in 


193 Mr. Mob. can's Ohfervations and Experiments on 
proportion to this perfe£tion. There are flames, however, 
which confift of burning particles, whole rays have partly 
efcaped before they afcended in the form of vapour. Such 
would be the flame of a red-hot coal, if expofed to fuch a heat 
as would gradually difperfe it into vapour. When the fire is 
very low under the furnace of an iron foundery, at the upper 
orifice of the chimney a red flame of this kind may be feen, 
which is different from the flame that appears immediately after 
frefh coals have been thrown upon the fire ; for, in confe- 
quence of adding fuch a fupply to the burning fuel, a vafi: 
column of fmoke afcends, and forms a medium fo thick as to 
abforb mofl of the rays excepting the red, 

"Experiments on eleSiric light. 

If we would wifh to procure any degree of certainty in any 
hypothefis which we may form concerning ele£lrical light, 
perhaps the following general dedu£lions may be of fome fer* 
vice to us. 

1. There is no fluid or folid body in its pafTagc through 
W'hich the eledlric fluid may not be made luminous. In water, 
fpirits, oil, animal fluids of all kinds, the difcharge of a Ley- 
den phial of almofl any fize will appear very fplendid, pro- 
vided we take care to place them in the circuit, fo that the 
fluid may not pafs through too great a quantity of them. My 
general method is to place the fluid, on which I mean to make 
the experiment, in a tube three-quarters of an inch in diameter, 
and four inches long. I flop up the orifices of the tube with 
two corks, through which I pufh two pointed wires, fo that the 
points may approach within one-eighth of an inch to each 
2 other. 

the Light of Bodies in a State of Comhiflion, 199 

other. The fluid in palling through the interval which fepa- 
rates the wires is always luminous, if a force be ufed fufii- 
ciently flrong. 1 fhould obferve, that the glafs tube, if not 
very thick, always breaks when this experiment fucceeds. To 
make the paflage of the fluid luminous in the acids, they muft 
be placed in capillary tubes, and two wires introduced, as in 
the preceding experiment, whofe points (hall be very near each. 
other. It is a well known fa6t, that the difcharge of a fmall 
Leyden phial in pafling over a flrip of gold, lilver, or Dutch 
^letal leaf, will appear very luminous. By conveying the con- 
tents of ajar, mcafurlng two gallons, over a ftrip of gold leaf 
one-eighth of an inch in diameter, and a yard long, I have 
frequently given the whole a dazzling brightnefs. I cannot 
fay, that a much greater length might not have been made 
very fplendid, nor can I determine to what length the 
force of a battery might be made luminous in this manner. 
We may give this experiment a curious diverfity, by laying 
the gold or filver leaf on a piece of glafs, and then placing the 
glafs in water ; for the whole gold leaf will appear molf bril- 
liantly luminous in the water by expofing it, thus circum- 
flanced, to the explofion of a battery. 

2, The difficulty of making any quantity of the eledlrical 
fluid luminous in any body increafes as the condudling power 
of that body increafes. 

EXP. I. In order to make the contents of a jar luminous 
in boiling water, a much higher charge is neceffary than would, 
be fufficlent to make it luminous in coLd water, which is uni- 
verfally allowed to be the worft conduftor. 

EXP. II. I have various reafons for believing the acids to 
be very good conductors. If therefore into a tube, filled with 
"Water, and circumftanced as I have already defcribed, a few 


200 Mr, Morgan's Obfervaiions cmd Experiments on 

drops of either of the mineral acids are poured, it will be 
almoft impoffible to make the fluid luminous in its paflage 
through the tube. 

EXP. III. If a jflring*, whofe diameter is one-eighth of an 
inch and whofe length is fix or eight inches, is moiftened with 
water, the contents of a jar will pafs through it luminoufly, 
but no fuch appearance can be produced by any charge of the 
fame jar, provided the fame firing be moiftened with one of 
the mineral acids. To the preceding inftance we may add 
the various inftances of metals which will conduct the eledtri-' 
cal fluid without any appearance of light, in circumftances 
the fame with thofe in which the fame force would have ap- 
peared luminous in pafling through other bodies whofe con- 
ducting power is lefs. But I proceed to obferve, 

III. That the eafe with which the eledrical fluid is rendered 
luminous in any particular body is increaled by increafing 
tiie rarity of the body. The appearance of a fpark, or of 
the difcharge of a Leyden phial, in rarefied air is well known. 
But we need not reft the truth of the preceding obfervation on 
the feveral varieties of this fa6t ; fimilar phenomena attend the 
rarefaction of aether, of fplrits of wine, and of water. 

EXP. IV. Intothe orifice of a tube, 48 inches long, and two- 
thirds of an inch in diameter, I cemented an iron ball, fo as to 
bear the weight which prefled upon it when I filled the tube 
with quickfilver, leaving only an interval at the open end, 
which contained a few drops of water. Having inverted the 
tube, and plunged the open end of it into a bafon of mercury, 
the mercury in the tube flood nearly half an inch lower than it 

* The thicknefs and diameter of the ftring fliould be regulated by the force we 



the hight of Badics ?/? a Siate of Cornkfrju^ z-^t 

did In a barometer at the fltme inftant, owing to the Yapour 
which was formed by the water. But through this rarefied wa- 
ter the ele£lrical fpark palled as luiniiioudy as ii; does through 
air equally rarefied. 

EXP. V. If, inflead of water, a few drops of fpirits of wine ari 
placed on the furface of the mercury, phi^enomena fimilar to 
thofe of the preceding experiment will be difcovered, with 
this difference only, that as the vapour in this cafe is more 
denfe, the ele6lrical fpark in its paffage through it is not q^uite 
fo luminous as it is in the vapour of water. 

EXP. VI. Good aether fubftituted in the room of the fpirits 
of wine will prefs the mercury down fo low as the height of 
1 6 or 17 inches. The eledrical fluid in pafling through this 
vapour (unlefs the force be very great indeed) is fcarcely lumi- 
,nous. But if the preffure on the furface of the mercury in the 
bafon be gradually leflened by the aid of an air-pump, the va- 
pour will become more and more rare, and the eledric fpark in 
pafling through it more and more luminous. 

EXP. vii. I could not difcover that any vapour efcaped from 
the mineral acids when expofed in vacuo, To give them, 
therefore, greater rarity or tenuity, I found different methods 
neceflary. With a fine camel-hair pencil, dipped in the vi- 
triolic, the nitrous, or the marine acid, I drew upon a piece of 
glafs a line about one-eighth of an inch broad. In fome in- 
ftances I extended this line to the length of 27 inches, and 
found that the contents of an elecShric battery, confifliing of la 
pint phials coated, would pafs over the whole length of this 
line with the greatefl brilliancy. If by widening the line, or 
by laying on a drop of the acid, its quantity was increafed 
in any particular part, the charge, in paffing through that part, 
never appeared luminous. Water, fpirits of wine, circum- 
Vol. LXXV. D d flanced 

202 Mr. Morgan's Ohjeivailons and Experiments on 
flauced fimilai'ly to the acids in the preceding experiment, 
were attended with iiiiiilar, hut not equal effects, hecaule, in 
confequence of the inferiority of their condu6ling power, it was 
necefiary to naake the line through which the charge palled 
confiderably fliorter. 

4. The brilliancy or fplendor of the ele^lric fluid in its 
pafiage through any body is always increafed by leilenlng the 
dimeniions of that body. I would explain my meaning by fay- 
ing, that a fpark, or the difcharge of a battery which we might 
fuppofe equal to a fphere one quarter of an inch in diameter, 
would appear much more brilliant if the fame quantity of fluid 
is compreffcd into a fphere one-eighth of an inch in diameter.. 
Thisobfervation is the obvious ccnfequenceof many known facls. 
If the machine be large enough to afford a fpark whofe length 
is nine or ten inches, this fpark may be {tzw fometlmes forming 
itfelf into a brufli, in which flate it occupies more room, but ap- 
pears very faintly luminous. At other times the fame fpark may 
be feen dividing itfelf into a variety of rr.mifications which fhoot 
into the furnmndliig air. In this cafe, likewlfe, the fluid is 
diffufed over a large luiface, and in proportion to the extent of 
that furface, fo is the faintnefs of the appearance. A fpark, 
which in the open air cannot exceed one quarter of an inch in 
diameter, will appear to fill the whole of an exhaufted receiver 
four inches Vv'lde and eight inches long. But in the former 
cafe it is brilliant, and in the latter it grows fainter and fainter 
as the (ize of the receiver increafes. To prove the obfervation, 
which I think m.ay be juftined by the preceding fads, I made 
the following experim.ents. 

EXP. VIII. To an Infulated ball, four inches in diameter, I 

fixed a filver thread, about four yards long. This thread, at 

the end which was remotefl from the ball, was fixed to another 

^ infulated 

the Light of Bodies in a State of Comhujlion, 203 

infulated fubftance. I brought the ball withui the ftrlking 
diftance of my condu^lor, and the fpark in pading from the cou- 
du^lorto the ball appeared v^ery brilliant ; but the whole length 
of the filver thread appeared faintly luminous at the fame in- 
ilant. In other words, when the fpark was confined within 
the dimenfions of a fphere one-eighth of an inch in diameter, 
it was bright, but, when difriifed over the furface of c^ir which 
received it from the thread, its light became fo faint as to be 
{&t\\ only in a dark room. If I leflened the furface of air 
which received the fpark by ihortening the thread, I never 
failed to increafe the brightnefs of the appearance. 

EXP. IX. To prove that the faintnefs of the eledtric light in 
'vacuo depends on the enlarged dimeniions of the fpace through 
which it is difFufed, we have nothing more to do than to in- 
troduce two pointed wires into the vacuum, fo that the fluid 
may pafs from the point of the one to the point of the other, 
when the diftance between them is not more than the one-tenth 
of an inch. In this cafe we ihali find a brilliancy as great as 
in the open air. 

EXP. X. Into a Torricellian vacuum, 36 inches in length, I 
conveyed as much air as would have filled two inches only of the 
exhaufted tube, if it were inverted in water. This quantity of 
air afforded refiftance enough to condenfe the fluid as it pafled 
through the tube into a fpark 38 inches in length. The bril- 
liancy of the fpark in condenfed air, in water, and in all fub- 
flances through which it paiTes with difficulty, depends on 
principles iimilar to thofe which account for the preceding fa(^s. 
I would now proceed to fhew, 

5. That in the appearances of ele£lriclty, as well as in thofe 
of burning bodies, there are cafes in which all the rays of light 
do not efcape ; and that the mofl refrangible rays are thofe 

D d 2 which 

2^4 Mr. MoRGAN^s Obfervat'wtu and Experiments on 

which efcape firft or moft eafily. The ele£lrical brufli Is 
always of a purple or bluiOi hue. If you convey a fpark 
through a Torricellian vacuum, made * withGiit boiling the 
mercury in the tube, the brufh will difplay the indigo ra\^s. 
The fpark, however, may be divided and weakened even in 
the open air, fo as to yield the moil refrangible rays only. 

EXP. XI. To an infulated metallic ball, four inches in dia- 
meter, I fixed a wire a foot and a half long. This wire termi- 
nated in four ramifications, each of which was fixed to a 
metallic ball half an inch in diameter, and placed at an 
equal diftance from a metallic plate, which communicated by 
metallic condu6lors with the ground. A powerful fpark, after 
falling on the large ball at one extremity of the wire, was 
divided in its paffage from the four fmall balls to the metallic 
plate. When I examined this divifion of the fluid in a dark 
room, I difcovered fome little ramifications which yielded the 
indigo rays only : indeed, at the edges of all weak fparks the 
fame purple appearance may be difcovered. We may likewife 
obferve, that the nearer we approach the center of the fpark,. 
the greater is the brilliancy of its colour. But I would now 
wifh to (hew 

6. That the influence of different media on electrical light 
is analogous to their influence on folar light, and will help us 
to account for fome very Angular appearances. 

EXP. XII. Let a pointed wire, having a metallic ball fixed to one 
of its extremities, be forced obliquely into a piece of wood, fo as 
to make a fmall angle with the furface of the wood, and to make 

* If the Torricellian vacuum is made with mercury perfeftly purged of air, it 
becomes a perfect non-condu6lor. This, I believe, will be proved decifively by 
iftme experiments whicli I hope will be foon communicated to the Royal Society. 

Dr. Price. 

I the 

the Light of Bodies in a State of Combufion, 2© 5 

the point He about onc-elghth of an inch below the furfac;-. 
Let another pointed wire, which communicates with the ground^ 
be forced in the fame manner into the lame wood, fo that 
its point likewife may He about one-eighth of an inch below 
the furface, and about two inches dlfiant from the point of 
the firft wire. Let the wood be infulated, and a ftrong Ipark 
which il:rikes on the metaUic ball will force its paliage through 
the interval of wood which lies between the points, and appear 
as red as blood. To prove that this appearance depends on the: 
wood's abforption of all the rays hut the red, I would obferve, 
that the greater the depth of the points is below the furface, the 
lefs mixed are the red rays. I have been able fometimes, by in- 
creafnig or diminifliing the depth of the points, to give the 
fpark the following fucceflion of colours. When they were 
deepeft below the lurface, the red only came to the eye through 
a prifm. When they were raifed a little nearer the furface, 
the red and orange appeared. When nearer ftill, the yellow ; 
and fo on till, by making the fpark pafs through the wood very 
near its furface, all the rays were at length able to reach the 
eye. If the points be only one-eighth of an inch below the 
fiarface of foft deal wood^ the red, the orange, and the yel- 
low rays will appear as the fpark pafles through it. But whea 
the points are at an equal depth in a harder piece of wood (fuch. 
as box) the yellow, and perhaps the orange, will difappear. Aa. 
a farther proof that the phifinomena I am defcribing are owing to 
the interpofition of the wood, as a medium which abforbs fome 
of the rays and fufFers others to efcape, it may be obferved, that 
when the fpark ftrikes very brilliantly on one fide of the piece 
of deal, on the other fide it will appear very red. In like man- 
ner a red appearance may be given to a fpark which ftrikes, 


2o6 Mr. Morgan's ObfervatJons and Experiments on 

brilliantly over the infide of a tube, merely by fpreading fome. 
pitch VQvy thinly over the outfide of the fame tube. 

EXP. XIII. I would now give another fa6l, whofe Angulari- 
ties depend very much on the influence Oi the medium through 
which the eletftrical light is made to pafs. If into a Torricel- 
lian vacuum, of any length, a few drops of aether are conveyed, 
and both ends of the vacuum are (lopped up with metallic con- 
dudlors, fo that a fpark may pafs through it, the fpark in its 
paflage will affume the following appearances. When the eye 
is placed clofe to the tube, the Ipark will appear perfe6lly 
white. If the eye is removed to the diftance of two yards, it 
will appear green ; but at the diftance of fix or feven yards, 
the colour of the fpark will be reddifli. Thefe changes evi- 
dently depend on the quantity of medium through which the 
the light paiies ; and the red light mxore particularly, which 
we fee at the greatefl: diftance from the tube, is accounted for 
on the fame principle as the red light of a didant candle or a 
beclouded fun. 

EXP. XIV. Dr. Priestley long ago obferved the red ap- 
pearance of the fpark when paffing through inflammable air. 
But this appearance is very much diverfified by the quantity of 
medium, through which you look at the fpark. When at a 
very confiderable diftance, the red comes to the eye unmixed j 
but, if the eye is placed clofe to the tube, the fpark appears 
white and brilliant. In confirmation, however, of fome of 
my conclufions, I Vv^ould obferve, that by increafing *the 
quantity of fluid which is conveyed through any portion 
of inflammable air, or by condenfing that air, the fpark may 
be entirely deprived of its red appearance, and made perfedly 
brilliant. I have only to add, that all weak explofions and 


ihe Light of Bodies in a State of Combufiion, 207 

fpnrks, when viewed at a didance, bear a rcddifh hue. Such 
arc tlie explofioiis which have pailed through water, I'piiits of 
wine, or T.ny bad condudor, when confined in a tube whofe 
diameter is not more than an inch. The reafon of tlicfe 
appearances Teems to be, that the weaker the fpark or explofioii 
is, the lefs is the iiglit which efcapes ; and the more vifible 
the effe6t of any medium which has a powder to abforb fomc of 
that light. 

The preceding obfervations concerning ele(5lrical h!ght were 
the refult of my attempts to arrange, under general heads, 
the principal fingularities attending it. They may, perhaps, 
affifl others in determining how far they may have led my mind 
aftray in giving birth to a theory wiiich I would now briefly 
defcribe in a few queries. 

I. If we confider all bodies as compounds, whofe confrituent 
parts are kept together by attracting one another with different 
forces, can we avoid concluding, that the operations of that 
attradive force are regulated, not only by the quality, but the 
quantity likewife of thofe component parts? If an union of a 
certain number of one kind ot particles, with a certain num- 
ber of a fecond and third kind of particles, forms a particular 
body, mufi: not the bond which keeps that body together be 
weakened or ftrengthened by Incrcafmg or diminiiliing any one 
of the different kinds of particles which enter into its confti- 
tution ? 

II. When, to the natural fhare of the eledric fluid al- 
ready exifting in the body, a frefli quantity of the fame 
fluid is added, muft not fome of the component parts of that 
body efcape ; or muf!: not that attractive force which kept all 
toaether be fo far weakened as to let loofe fome conllituent 


20 S Mi'\ MogGAN*s QS/erva^ms and Experiments an 

parts, and amongft thefe the paiticlea of light in parti* 
cilia r ? 

III. Mufl; not this feparation of parts be great ia proportion 
to the quantity of extraneous particles which are added to the 
body ? Or (agreeable to the 4th obfervation) muil: not the 
fpark be more fplendid and brilliant, the more the ele6;rical 
fluid is concentered in any given fpace ? 

IV. In the diminution or alteration of that attradive force ors 
which depends the conftitution of bodies, may there not be a 
gradation which, in the prefent cafe, as well as in that of 
burning bodies, will caufe the efcape of fome rays fooncr than 
others ? 

Ohfervations on pJoofphoj-ic light. 

It is obvious, from Mr. B. Wilson's experiments, that 
there are many curious diverfities in the appearances of phof- 
phori. Some (hells, prepared ngrccably to his diredlons, after 
expbfure to the fun or to the flafh of a battery, emit a purple, 
others a green, and others a reddifh light. If wdth Mr. Wil- 
son we fuppofe, that thefe fliells are in a ftate of flow com- 
buflion, may we not conclude, that fome arejull; beginning to 
burn, and therefore, agreeably to what I haveobferved on com- 
buftlble bodies, emitting the mod: refrangible rays; whilft others 
are in a more advanced flate of combuftion, and therefore 
emitting the leaft refrangiible. If this conclufion be right, 
the fhells which are emitting the purple, or the green, mufl 
ftill retain the yellow, the orange, and the red, which will 
alfo make their appearance as foon as the combuftion is fuffi- 
dently increafed. 


ibe "Ltght of Eodks in u State of Comb ujl ton, ■20.9 

e:XP. XV. Place a fliell vvhllfl emitting its green rays on a 

warm fhovel, and the appearance of the fhell will be foou 

cl^anfred into that of a veilow mixed with red. To Mr. Wil- 

-son's theory, hou^ever, of (low combuftion the following ob- 

j-e6lions may be oppoled. 

i''. If phofphoric (hells owe their light to this caufe, wc 
muft confider the word combuftion when applied to them as 
implying in its iignilication all thofe circumftances which are 
the ufual attendants of a body whilft on fire. Amongfl: other 
iieceirary confequences in fuch a cafe, the increafe of heat muft 
increalc the decompofition of the combuftible ; whereas we 
•difcover an etl^^t the very oppolite to this in the appearance of 
a phofphoric body, which never fails to lofe its light entirely 
in a certain degree of heat, without lohng the power of be- 
^coming phofphoric again when it has been fufficiently cooled. 
Befides, when a phofphoric ihell has been made very hot, and 
while it has continued fo, I have conveyed the moft brilliant 
difcharge of a battery over it without efFe(^. In other words, 
heat, or the very caufe which promotes combuftion in all other 
inftances, in this particular cafe puts an end to it. Mr. Wil- 
son, in his Treatife on Phofphori, has defcribed an experiment 
fimilar to the preceding. But the refulthe mentions is different 
from that here mentioned. However, from a regard to his 
authority, I have fo frequently repeated my trials that I cannot 
juftly fufpe<5l myfelf of any inaccuracy. 2\ When bodies 
are wafled by combuftion, they can never be made to re-affume 
the appearances which they previoufly difplayed. No power 
can give to alhes the phenomena of a burning coal. But 
phofphoric bodies are very different in this refpe<5t ; for a fhell 
may be made to lofe all its light by expofure to heat, and again 
. Vol. LXXV. E e may 

210 Mr. Morgan's Ohfefuat'.ons and Experiments on 

may be made as Inminous as ever by expofure to the fun. But 
2^. It is obfervable, that fome bodies, which are moO: beau- 
tifully phofphoric, or which, according to Mr. Wilson*s 
theory, are in the bed Aate of flow combuftion ; it is obfervable, 
I fay, that the fame bodies are the moftobftinate in refifting the 
fire. The diamond, which to be decompofed requires the 
force of a mofi: powerful furnace, is, according to this 
theory, wailing away, owing to a feparation of parts which 
is promoted by the weakeft influence of the fun's rays. — With- 
out determining whether the p>recedmg obje6lions be valid, let us 
now fee the confequence of admitting the common hypothecs, 
that the detention of tbofe rays which fall upon phofphori is 
owing to fome force which prevents their immediate reflection, 
but is not adequate to their entire abforption. This force, 
whatever it be, cannot well be fuppofed to operate with equal 
power on all the rays. And if this be not the cafe, I think 
we cannot avoid concluding, that phofphoric fhells will afliime 
-r different colours, owing to the earlier and later efcape of the 
different rays of light. This conclufion is juftified by an expe- 
riment which I have already appealed to. When the force is 
f ich as to admit of the efcape of the purple, the blue, and. the 
green, we have only to leffen that force by warming the bodv, 
and the yellow, the orange, and red efcape. It is proved by 
Beccaria's extenfive experience on this fubj.ft, that there is 
fjarcely any body which is not phofphoric, or which may. not 
be made fo by heat. But as the phofphoric force is moft 
powerful when the purple rays only efcape, fo we are to- con- 
clude, that it is weakeft when it is able to retain the red rays only. 
This conclufion is agreeable to fevcral faCls. Chalk, oyfter- 
thells, together w^ith thofe phofphoric bodies whofe goodnefs 
7 has 

the Light of Bodies in a State of Conibufion* 2 1 1 

has been very mucli impaired bv long keeping; when 
finely powdered and placed within the circuit of an elcdrical 
batter}', will exhibit by their fcattered particles a fliowTr 
of light; but tliefe particles will appear reddilh, or their 
phofphoric power will be fufficient only to detain the 
yellow, orange, and red ravs. When fpirits of wine are in a 
iimilar manner brought within the circuit of a battery, a 
fimilar efte6l may he difcovered ; its particles diverge in feveral 
direftions, dilplaying a moft beautiful golden appearance. The 
metallic calces are, of all bodies, thofe which are rendered 
phofphoric with the greateft difficulty. But even thefe may 
be fcattered into a fhower of red luminous particles by the 
electric ftroke. 

JC'orwich, Oct. 7, 1784, 

POSTSCRIPT by the Rev. Dr. Price. 

BY the phofphoric force mentioned in the laft paragraph of 
this paper, Mr. Morgan appears to mean, not the force with 
which a phofphoric body emits, but the force with which it 
abforbs and retains light. This laft force is proportioned 
to the degree of attra6tion between the phofphoric body and 
light ; and therefore muft (as Mr. Morgan obferves) be 
iveakefi when it emits fo freely the light it has imbibed as not 
to retain thofe rays which adhere to it moft ftrongly. Ac- 
cording to Mr. Morgan's theory, thefe rays ^re thofe which 

E e 2 arc 

ii2 Mr> Morgan's Obfervatlons and Experiments, Sec, 
am leafl refrangible. The obfervatlons and experiments hir 
this paper feem to render this theory probable. It is, how- 
ever, an objeaion to it, that the lefs refrangibility of rays- 
feems to imply a lefs force of attradion between them and the. 
fubftances . which refrad them ; but it fnould be confidered-, 
that, polTibly, the force of cohefion,, which unites the rays 
of light to bodies, may be a different power from that, wluch.. 
refra£is thera^. 

[ 213 ] 

Xir. 0;; the ConJlruBlon cf the Heave tn. 
By VVilllam Ilerichcl, Efq. F. R. S. 

Read February 3, i/^i'* 

Tn E fubje£l of the Coiifrriicllon of the Heavens, on 
which I have fo lately ventured to deliver my thoughts 
to this Society, is of fo extenllve and important a nature, that 
we cannot exert too much attention in our endeavours to throw 
all poffible light upon it; I fhall, therefore, now attempt 
to pi.rfue the delineations of wliich a faint outline was begun 
iu my former paper. 

By continuing to. oblerve the heavens with my laft con- 
ftruvfled, and fmce that time much improved inftrument, I aai 
now enabled to bring more confirmation to feveral parts that 
were before but weakly fupported, and alfo to offer a few {k.[\l 
further extended hints, fuch as they prefent themfelves to my 
prefent view. But firft let me mention that, if we would 
hope to make any progrefs in an invefligation of this delicate 
nature, we ought to avoid two oppofite extremes, of which I 
can hardly fay which is the moft dangerous. If we indulge a 
fanciful imagination and build worlds of our own, we muft 
not wonder at our going wide; from the path of truth and 
nature ; but thefe will vanifh like the Cartefian vortices, that 
foon gave way when better theories were offered. On the other 
hand, if we add obfervation to obfervation, without attempt- 
ing to draw not only certain conclufions; but alfo conjedural 


2 14 Mr. Herschel on the 

views from them, we offend again il: the verj end for which 
only obfervations ought to be made. I will endeavour to keep 
a proper medium ; but if I fhould deviate from that, I could 
wilh not to fall into the latter error. 

That the milky way is a mofl: extenfive (Iratum of flars of 
various fizes admits no longer of the lead: doubt ; and that our 
fun is actually one of the heavenly bodies belonging to it is as 
evident. I have now viewed and gaged thl« Ihining zone in 
almoft every direction, and find it compofed of flars whofe 
number, by the account of thefe gages, conftantly increafes 
and decreafes in proportion to its apparent brightnefs to the 
naked eye. But in order to develop the ideas of the univerfe, 
that have been fuggefled by my late obfervations, it will be beft 
to take the fubjecl from a point of view at a confidcrable 
diflance both of fpace and of time. 

Theoretical view. 

Let us then fuppofe numbcrlefs ftars of various fizes, feat- 
tered over an indefinite portion of fpace in fuch a rrianner as to 
be almoft equally diftributed throughout the whole. The laws 
of attra6lion, which no doubt extend to the rcmoteft regions of 
the fixed ftars, will operate in fuch a manner as moft probably to 
produce the following remarkable effedts. 

^'' Formation of nebiilce. 

Form I. In the firft place, ftnce we havcfuppofed the ftars 

to be of various fizes, it will frequently happen that a ftar, 

being confiderably larger than its neighbouring ones, will 

attract them more than they will be attra«fted by others that are 

-■sj.;^:.; immediately 

Ojfrflruclion of the Heavens. 2 1 ^ 

immediately around them ; by which means they will be, in 
time, as it were, condenfed about a center ; or, in other words, 
form themfelves into a cluftcr of ftars of almoft a globular 
figure, more or lefs regularly fo, according to the fize and 
original diftancc of the furrounding ftars. The perturbations 
of thefe mutual attractions mufl undoubtedly be very intricate, 
as -"we may eafily comprehend by confidering what Sir Isaac 
Newton lays in the firft book of his Principia, in the 38th 
and folio vving problems; but in order to apply this great 
author's reafoning of bodies moving in ellipfes to fuch as are 
here, for a while, fuppofed to have no other motion than what 
their mutual gravity has imparted to them, we mufl: fuppofe 
the conjugate axes of thefe elliples indefinitely diminiflied, 
whereby the ellipfes will become ftraight lines. 

Form IL The n^xt cafe, which will alfo happen aimoft as 
frequently as the former, is where a few fl-ars, though not 
fuperior in fize to the reft, may chance to be rather nearer each 
other than the furrounding ones j for here alfo will be formed a 
prevailing attraction in the combined center of gravity of them 
all, which will occafion the neighbouring flars to draw toge- 
ther ; net indeed fo as to form a regular or globular figure, but 
however in fuch a manner as to be condenfed towards tlie 
common center of gravity of the Vv^iole irregular elufler. And 
this conflruClion admits of the utmofl: variety of Ihapes, ac- 
cording; to the number and fiJuation of the ftars which firfi: 
gave rife to the condenfation of the refl. 

Form 111. From the compofition and repeated conjuniTcion 
of both the foreooin": forms, a third may be derived, w^henmanv 
large flars, or combined fmall ones, are fituated in- long ex- 
tended, regular, or crooked rows, hooks, or branches ; for they 
will alfa draw the furrounding ones, fo as to produce figurejy 


21 6 Mr. Herschel on the 

of condenfed ftars coarfely fimilar to the former which gave 
rife to thcfe condenflitioiis. 

•Form IV. We may Hkevvife admit of ftill more extenfive^ 
combinations; when, at the fame time that a chafter of fiars 
is forming in one part of fpace, there may be another coUecl- 
}X\^ in a different, but perhaps not far diftant quarter, which 
may occafion a mutual approach towards their common center 
of gravity, 

V. In the laft place, as a natural confequence of th« 

former cafes, there will be formed great cavities or vacancies 
by the retreat of the ftars towards the various centers which 
attrad: them ; fo that upon the whole there is evidently a field 
of the greateft variety for the mutual and combined attractions 
of the heavenly bodies to exert themfelves in. -I ihall, there- 
tore, without extending myfelf farther upon this fubjed:, pro- 
ceed to a few coiifidcrddons, that will naturally occur to every 
'OWQ who may view this fubject in the light I have here done. 

Ohjedliom cojijiderea. 

'Atfirfl: f3ght then it will feem as if a fyilem, fuch as it has 
been difplayed in the foregoing paragraphs, would evidently 
tend to a general deftrudion, by the fhock of one flar's 
falling upon another. It would here be a fufficient anfwer to 
fay, that if obfervation fliould prove this really to be the 
fyftem of the univerfe, there is no doubt but that the great 
Author of it has amply provided for the prefervation of the 
whole, though it fhould not appear to us in what manner this 
is effetSled. But I (hall moreover point out feveral circum- 
;Ilances that do manifeftly tend to a general prefervation ; as, in 
ithe firft place, the indefinite extent of the iidereal heavens, 

6 which 

Conjiruditon of the Heavens. 217 

which miift produce a balance that will effedually fecure all 
the great parts of the whole from approaching to each other. 
There remains then only to fee how the particular ftars be- 
longing to feparate clufters will be preferved from rufliing on 
to their centers of attraction. And here I muft obferve, that 
thougli I have before, by way of rendering the cafe more fim- 
ple, confidered the ftars as being originally at reft, I intended 
not to exclude projectile forces ; and the admiffion of then* 
will prove fuch a barrier againft the feeming deftruClive power 
of attraction as to fecure from it all the flars belonging to a 
clufter, if not for ever, at leafl for millions of ages Befides, 
we ought perhaps to look upon fuch clufters, and the deftruc- 
tion of now and then a (tar, in fome thoufands of ages, as 
perhaps the very means by which the whole is preferved and 
renewed. Thefe clufters may be the L^^^^r^/or/Vjoftheuniverfe^ 
if I may fo exprefs myfelf, wherein the mofl falutary remedies 
for the decay of the whole are prepared. 

Optical appearances. 

From this theoretical view of the heavens, which has been 
taken, as we obferved, from a point not lefs diftant in time 
than in fpace, we will now retreat to our own retired flation, 
in one of the planets attending a ftar in its great combination 
with numberlefs others ; and in order to inveftigate what will 
be the appearances from this contracted fituation, let us begin 
with the naked eye. The ftars of the firft magnitude being 
in all probability the neareft, will furnilh us with a ftep to 
begin our fcale ; fetting off, therefore, with the diftance of 
Sirius or ArCturus, for inftance, as unity, we will at prefent 
fuppofe, that thofe of the fecond magnitude are at double, and 

Vol. LXXV. F f thofc 

2.8 Mr, Herschel on the 

thofe of the third at treble the diftnnce, and fo forth. It is not 
neceffary critically to examine what quantity of light or mag- 
nitude of a ftar intltles it to be eftimated of fuch or fuch a pro- 
portional diftance, as the common coarfe eftimation will anfwer 
our prefent purpofe as well; taking it then for granted, that a 
flar of the feventh magnitude is about fcven times as far as 
one of the hrft, it follows, that an obferver, who is inclofed 
an a globular cl after of ftars, and not far from the center, will 
never be able, with the naked eye, to fee to the end of it : for,, 
iince, according to the above eftimations, he can only extend his 
view to about feven tunes the diftance of Sirius, it cannot be 
expelled that his eyes fhould r?ach the borders of a clufter 
which has perhaps not lefs than fifty flars in depth every where 
around him. The whole univerfe, therefore, to him will be 
comprifed in a fet of conftellations, richly ornamented with 
fcattered ftars of all fizes. Or if the united brightnefs of a 
neighbouring clufter of ftars fliould, in a remarkable clear 
night, reach his fight, it will put on the appearance of a fmall, 
faint, whitifti, nebulous cloud, not to be perceived without 
the greateft attention. To pafs by other lituations, let him 
be placed in a much extended ftratum, or branching clufter of 
millions of ftars, fuch as may fall under the IIF form of ne- 
bulae conftdered in a foregoing paragraph. Here alfo the hea- 
vens will not only be richly fcattered over with brilliant con- 
ftellations, but a ftiinlng zone or milky way will be perceived 
to furround the whole fphere of the heavens, owing to the 
combined light of thofe ftars which are too fmall, that is, too 
remote to be feen. Our obferver's fight will be fo confined, 
that he will imagine this fingle colleftion of ftars, of which he 
does not even perceive the thoufandth part, to be the whole 
contents of the heavens. Allowing him now the ufe of a 
4 common 

Conjlrudlion of the Heavens > 219 

common telefcope, he begins to fufpeft that all the milkuiefs 
of the bright path which furrounds the fphere may be owing 
to ftars. He perceives a few cluflers of them in various parts 
of the heavens, and finds alfo that there are a kind of nebu- 
lous patches ; but ftill his views are not extended fo far as to 
reach to the end of the ftratum in which he is fituated, fo that 
he looks upon thefe patches as belonging to that fyflem which 
to him feems to comprehend every celeftial objed:. He now 
increafes his power of vifion, and, applying himfelf to a clofe 
obfervation, finds that the milky way is indeed no other than a 
collection of very fmall ftars. He perceives that thofe objects 
which had been called nebulae are evidently nothing but cluflers 
of ftars. He finds their number increafe upon him-, and when 
he refolves one nebula into ftars he difcovers ten new ones 
which he cannot refolve, He then forms the idea of immenfe 
flrata of fixed ftars, of cluftersof ftars and of nebulas {a) ; till, 
going on with fuch interefting obfervation s, he now perceives 
that all thefe appearances muft naturally arife from the con- 
fined fituation in which we are placed. Confined it may juitly 
be called, though in no lefs a fpace than what before appeared 
to be the whole region of the fixed ftars ; but which now has 
affumed the ihape of a crookedly branching nebula ; not, in- 
deed, one of the leafl, but perhaps very far from' being the 
mofl confiderable of thofe numberlefs clufters that enter into 
the conftrudtion of the heavens. 

Refuit of ObfervationSi 

1 (hall now endeavour to fhew, that the theoretical view of 
the fyftem of the univerfe, which has been expofed in the 
{a) See a former paper on the Conftruftion of the Heavens. 

F f 2 fore- 

220 Mr. Herschel on the 

foregoing part of this paper, is perfectly confiftent with h€t% 
and feems to be confirmed and eflabUfhed by a feries of obfer- 
vations. It will appear, that many hundreds of nebulae of the 
firft and fecond forms are actually to be ittw in the heavens, 
and their places will hereafter be pointed out. Many of the 
thtid form will be defcribed, and inftances of the fourth re- 
lated. A few of the cavities mentioned in the fifth will be 
particularifed, though many more have already been obfcrved ; 
fo that, upon the w^holc, I believe, it will be found, that the 
foregoing theoretical view, with all its confequential appear- 
ances, as feen by an eye inclofed in one of the nebulae, is no 
other than a drawing from nature, wherein the features of the 
original have been clofely copied ; and 1 hope the refemblance 
will not be called a bad one, when it fliall be confidcred how" 
very limited mufl: be the pencil of an inhabitant of fo fmall 
and retired a portion of an Indefinite fyftem in attempting the 
picture of fo unbounded an extent. 

But to proceed to particulars : I fhall begin by giving the 
following table of gages that have been taken. In the firft 
column is the right afcenfion, and in the fecond the north 
polar diflance, both reduced to the time of Flamsteed's 
Catalogue. In the third are the contents of the heavens, being 
the refult of the gages. The fourth fhews from how many 
fields of view the gages w^ere deduced, which have been ten or 
more where the number of the ftars was not very confiderable ; 
but, as it would have taken too much time, in high numbers, 
to count fo many fields, the gages are generally fingle. Where 
the ftars happened to be uncommonly crouded, no more than 
half a field was counted, and even fometimes only a quadrant ; 
but then it was always done with the precaution of fixing on 
fome row of ftars that would point out the divifion of the field, 


Conjlrudlion of the Heavens. 221 

fo as to prevent any conlidcrable miftake. When five, ten, or 
more fields are gaged, the polar diftance in the fecond column 
of the table is that of the middle of the fvveep, which was 
generally from 2 to 2t degrees in breadth; and, in gaging, a 
regular diftribution of the fields, from the bottom of the fweep 
to the top, was always ftridly attended to. The fifth column 
contains occafional remarks relating to the gages. 

I. Table of Star-Gages. 


P.D. Stars. 



H. M. S 

D. M. 

I 41 

78 47 



4 55 

65 36 



7 54 

74 13 



Moft of the ftars extremely fmall. 

8 24 

49 7 



9 52 

113 17 



% The gages marked with an afterilk 

12 52 

113 17 



;f are thofe by which fig. 4. tab. 

16 48 

67 44 



Vlll. has been delineated. 

21 52 

113 17 




22 21 

87 10 



28 26 

46 54 



31 38 

46 54 



Z3 33 

65 32 



34 22 

56 38 



35 22 

55 38 



36 39 

76 32 



39 56 

78 43 



40 29 

48 43 



44 21 

87 10 



46 22 

69 51 



46 33 

65 32 



48 42 

58 47 



48 50 

58 13 



P 53 18 

67 41 



A little hazy. 

53 40 

45 37 



54 10 

75.16 13 1 




Mr\ Hesschel on the 

R.A. P.D. 




H. M. S. 
o 55 10 

o 5^ 4 

o 57 52 

59 10 

1 16 

D. M. 

73 16 

iM 17 

74 25 
74 1^ 








I I 10 
I I 18 
I 2 52 
I 3 52 
I 4 15 

74 5 


IJ3 17 
94 52 








Very clear for this altitude. 
Moft of the ftars very finall. 

I 4 33 

I 5 55 
I 7 27 


I 12 48 

65 32 
7S 31 

45 23 
58 37 
60 19 

1 1,0 



I 13 4 
I 15 51 
I iB 21 
I 23 21 
I 27 30 

94 50 
48 40 

48 40 
48 40 
65 42 







I 31 21 

I 32 4 

I 33 10 

I 33 32 

• I 34 52 

87 7 

94 50 

100 8 

92 35 
60 8 









I 43 30 
1 45 24 

I 48 4 

I 54 24 
I 58 55 

65 42 

69 43- 
100 12 

76 28 
61 55 







2 4 28 
2 4 36 
2 7 12 

2 10 4 

87 5 
78 38 

94 56 

83 3 

100 12 








Corjlru5ilon cf the Heavens* 







H. M. S. 

D. M. 

2 II 30 

65 45 



2 16 27 

no 54 




2 19 27 

76 24 



2 22 17 

45 31 



2 23 6 

60 16 



2 23 19 

113 8 




2 24 6 

5« 30 



2 27 40 

1 15 21 



•^ The fituationtoo low for great accu- 

2 30 

94 56 




2 31 23 

76 22 



2 35 14 

87 2 



2 38 

94 56 



: 2 42 7 

61 50 



2 47 32 

74 3 

II, I 


Moll of the ftars exceedingly fmall. 

2 49 22 

92 55 



2 49 30 

no 55 




2 50 

94 56 



2 54 53 

76 22 



2 59 56 

81 10 




3 I 53 

78 37 



3 I 56 

81 10 



3 4 53 

78 37 



3 10 20 

lOO 2 



3 II 6 

59 29 



1 In a part of the heavens which looks 

3 13 6 

59 29 



1 pretty full of liars to the naked 

3 15 6 

59 29 



J eye. 

3 22 57 

83 I 



3 23 21 

92 49 



3 29 41 

46 35 



3 35 

62 I 



About 15 liars generally in the field. 

3 35 12 

100 3 



3 36 I 

113 3 




3 42 49 

46 10 



3 48 16 

99 59 



3 55 II 

74 2 






Mr, Her SO H EL on the 






H. M. S. 

D. M. 

4 I 24 

92 48 



4 6 iB 

82 57 



4 8 31 

114 55 




4 12 41 

69 33 



And many more, extremely fmall, 

4 16 34. 

111 45 



•^ fufpefted. 

4 26 34 

112 45 




4 27 II 

70 41 



4 28 41 

70 I 



4 29 5 

69 24 



4 30 H 

99 50 



4 31 ^9 

67 33 



4 32 29 

6() 2 



4 33 31 

114 55 




4 42 14 

86 27 



4 S3 22 

72 59 



4 57 45 ' 

83 22 



4 58 45 

84 36 



5 I 16 

69 23 



S 3 45 

83 29 



5 10 52 

69 22 



5 II 22 

96 37 



5 17 22 

96 15 



5 18 

80 46 



About 30 ftars in the field, not very 

5 21 7 

92 52 



exadly gaged. 

5 24 12 

66 5 



5 27 3 

68 52 



5 27 48 

no 40 




5 33 4 

76 10 



5 33 12 

66 26 



5 33 17 

iH 59 




5 34 45 

70 33 



5 36 30 

62 I 

20 — 30 

From 20 to 30 ftars in the fields, not 

5 37 4 

74 26 



very exactly gaged. 

5 38 45 

70 8 



5 41 12 

66 43 




ConJlruBion of the Heave?is, 







H. M. S. 

D M. 

5 44 

n6 43 




5 45 3^^ 

83 30 


5 47 34 

112 34 




5 48 30 

62 I 


About 30 liars in the field ; not very 

5 48 44 

92 51 


CKadlly gaged. 

5 49 

80 5 



5 52 14 

Q3 14 


5 5^ 30 

83 30 


S S3 "^ 

80 5 


5 55 4 

92 56 


5 56 40 

70 27 


5 57 

80 5 


5 57 37 

1 10 33 




5 58 51 

88 36 


5 59 30 

83 30 



6 23 

86 38 



6 r 

80 5 




80 5 



67 17 



Very unequally fcattered. 

6 b 14 

96 16 


6 6 30 

83 30 


6 6 30 

80 5 



6 6 38 

91 45 


Like the rell:, or many fuch fields. 

6 6 40 

68 24 



80 5 



6 9 34 

113 35 



6 II 

62 I 



6 II 

80 5 


The lead: number of ftars in the field I 

6 II 34 

H2 5 


% could find in this neighbourhood. 

6 II 37 

90 15 

About 60 or 70 generally. 

6 14. 4 

68 II 


6 14 38 

90 15 


6 17 45 

62 I 


6 18 14 

96 12 


Very unequally fcattered. 

6 19 14 

93 59 72 





il<fr. Herschel on the 







H. M. S. 

D. M. 

6 26 17 

iH 59 



6 27 14 

94 3^ 




6 27 32 

70 23 


6 3-1 48 

115 40 


^ 34- 44 

9^ 25 


6 34 55 

79 5 


Generally about 50 ftars. 

6 56 

94 5^^ 



6 37 ^5 

75 5 


Geaerally about 70 flars. 

6 39 8 

99 7 




116 43 



6 43 25 

79 5 


6 44 28 

IGO 30 



6 49 5 

87 21 



6 49 30 

77 3^ 


Many fields like this. 

6 49 44 

9^ 'iZ. 



6 51 8 

98 33 



6 52 

116 21 


! ^ 52 ^5 

79 5 


A,bou: 60 ft.irs. 

6 52 44 

9- 59 



6 54 9 

111 11 



6 57 8 

J 00 I 



6 57 3S 

9b 50 



6 58 39 

112 48 



7 25 

79 5 


7 4 

92 3 



7 4 38 

98 59 



7 5 9 




7 S. 9 

112 15 



7 12 8 

100 5. 



7 15 3S 

98 12 



7 19 

91 51 



7 20 

78 59 


7 25 9 

III 21 


# One of the richeft fields. 

7 28 9 

112 34 



7f A field like the reft. 

7 3^ 3 

115 28 


i\i..>. i* 

ConfrnSlbn of the Ueavms* 







H. xM. S. 

D. iM. 


7 41 9 

1 13 26 


^- i 

7 53 4 

80 39 




8 I 4 

III 15 



8 3 4 

113 31 


8 b 3« 

ICO 5 



8 7 3^ 

99 3 



b II 8 

99 25 

2 4., 2 



8 12 34 

I J2 ii; 



8 22 4 

J 11 30 



8 31 4 

112 I 


8 32 24 

1 12 7 


8 35 4 

112 17 


8 35 14 

III 19 


8 40 4 




8 45 4 

113 22 


8 46 39 

91 26 




8 48 4 

112 23 



8 57 25 

66 20 




9 5 38 

91 22 




9 10 4 

115 17 



9 20 4 

112 23 



9 20 40 

99 12 

II, I 


9 20 58 

88 7 




9 35 4 

1 12 23 



9 38 4 

115 17 



9 38 8 

90 23 




9 42 16 

86 16 



# ,^ 

9 45 49 

112 21 

13' 2 


Strong twilight. 

10 4 

1^5 17 



10 16 8 

88 8 




10 19 32 

91 14. 



10 25 8 

b8 8 




10 26 

81 41 




II 4 4 

81 38 




II 7 36 

91 14 



G ^ 



Mr. Herschel on the 






H. M. S. 

D. M. 


1 1 1 o 6 

115 23 




II i6 52 

81 38 



II .0 37 

91 17 




II 53 43 

81 3'. 




12 5 6 

78 57 




12 30 40 

79 3 





12 46 51 

81 40 




12 4b 19 

79 4 





12 53 45 

loi 45 





12 57 8 

99 5^ 



Pretty itrong day-light. 


13 I 19 

79 4 





13 17 27 

101 45 




13 22 49 




Some day-light. 

13 27 57 

loi 45 



13 31 lO 

75 55 



^f Generally about 5 or 6 ftars in 

the field. 

13 38 53 

104 27 



13 48 49 

100 I 



Strong twilight. 

13 51 27 

101 45 



13 55 44 

58 II 



■)f Twilight. 

13 57 53 

104 27 



Moft very fmall. 

- 14 9 49 

100 I 




14 13 52 

113 4 



14 14 57 

lOI 45 



14 24 49 

81 53 



14 29 45 

100 5 



14 30 7 

66 3 

■^ All fizes. 

14 30 8 

80 38 



14 33 22 

58 7 



% Chiefly fmall. 

14 33 52 

113 4 



14 39 57 

lOl 45 



All fizes. 

14 40 36 

64 47 



14 44 II 

114 54 



14 49 52 

113 4 



H 51 H 

58 10 



% Twilight. 

H 52 58 

60 41 



9f Strong Aurora^borealis, 

— - 


Conjlruti'ion bf the Heavens, 







H. iM. S. 

D. M 

H 53 7 

65 }5 



Chiefly lar<:^e. 

'4 SS 36 

64 47 



Moil very Imall, 

'4 59 11 

114 54 



15 2 42 

62 48 



15 3 7 

66 15 



^5 4 36 

64 47 




15 8 37 




^5 8 45 

93 5 



Very fmal!. 

15 13 \~ 

62 48 



15 J5 44 

58 17 



7f Twilight, 

15 19 48 

60 40 



9f Strong Aurora boreaiis, fo as 

to aftcd 

15 20 

75 52 



the gages. 

15. 21 

93 5 



15 26 7 

^^ SI 



IS 28 48 

99 51 



15 29 7 

66 15 



All fizes. 

15 29 44 

58 17 



■^ Twilight. 

15 32 

75 51 



15 33 52 

III 32 



15 35 

75 51 



15 42 2 

58 14 



^ Twilight, 

15 42 3 

116 56 



15 42 sz 

^^3 47 



The ffcars too fmall for the gage, 


15 46 30 

93 5 



15 48 37 




' * 

15 48 46 

63 4 



15 49 52 

111 32 



The fitxiation fo low that it 


15 50 20 

114 55 



attention to fee the liars. 

15 57 3 

116 q6 


16 2 

58 14 



■^ Twilight. 

160 c; 

116 56 



16 12 

214 57 



16 3 12 

114 57 



16 4 

75 43 



All fizes. 

16 4 19 

1 13 6 



Perfeaiy clear. See p. 256. 



Mr, PlEnsciiEL on the 






H. M. S. 

D. M. 

1 6 4 46 

63 4 



Moll: iVnall. 

16 4 52 

99 57 



Moon and twilight. 

16 6 28 

113 4 



Pcrfedly clenr. 

16 712 

6(^ 15 



16 8 6 

ii5 1 



16 8 II 

93 9 



16 8 16 

116 48 

1 1,6 


16 9 28 

^^3 4 



Perfeftly clear. See p. 256. 

16 II 28 

113 4 



The iaaie. 

16 13 28 

113 4 



g Serpentarii and 19 Scorpii 

vifible to 

16 1.3 52 

58 24 



# Moil: fniall. [the 

naked eye. 

16 14 42 

t>3 7 



Moll vervfmali. 

16 15 37 

80 40 



All fizes. 

16 17 28 

"3 4 



16 20 51 

81 57 



16 23 

73 43 



16 23 28 

"3 4 



16 24 II 

93 9 



Require attention to be feen. 

16 25 7 

bo 40 



16 27 32 

68 23 




16 29 16 

116 48 



16 30 31 

80 4.0 



16 31 12 

66 15 



Strong twilight. 

16 32 28 

113 4 



Moft extremely fmall. 

16 32 52 

58 24 



■^ Moll fmall. 

16 35 42 

63 7 




16 35 48 

93 15 



All fizes. 

16 38 12 

66 15 



Strong twilight. 

16 38 45 

107 57 



Strong twilight. 

16 40 51 

113 14 



16 45 32 

68 23 




16 51 45 

107 57 



16 52 22 

66 26 



Day-light pretty flrong. 

16 55 42 

63 7 



-jf Strong twilight. 

17 I 34 

58 11 



•9f Strong day light. 

T: "v 



Cofijlriiclion of the Heave /ts. 





Fit Ids 


H. M. S. 

D. M. 

17 3 22 

66 26 



■X- Day-]ig!it too ilrcng for gaging. 

17 6 3(3 

98 38 



Moft; finall, a;id more lulpected. 

17 9 30 

11^ SS 



^'7 9 32 

68 23 



17 11 10 

66 26 



■^ D.-3j/-tight pretty flrong. 

17 13 24 

63 21 



■)(- Strong day-light. 

17 17 3b 

III 47 



Moon and day-lighc. 

17 25 7 

108 s 



17 27 29 

lib 48 



17 28 32 

68 23 




■^ Twilight. 

17 30 29 

116 48 


17 33 29 

1 16 48 



Day-light very ftrong. 

17 34 36 

98 38 



Very ftrong twilight. 

17 39 3+ 




Moft large. 

17 40 41 

114 52 



Day-light very ftrong. 

17 41 29 

116 48 



Day-light very ftrong. 

17 43 45 

105 3 



Flying clouds. 

17 48 

61 18 



Moft large. 

17 50 4 

56 16 




17 50 7 

108 5 



Like the reft in this part of the heaven. 

17 52 7 

108 5 



Many fuch fields juft by. 

17 52 17 

98 43 



. 17 52 30 

62 12 



Moft large. 

17 52 32 

68 19 



■X- Strong day-light. 

17 55 7 

108 5 



17 55 15 

106 6 



Many fuch fields. 

17 55 3« 

112 54 

1 12 


17 57 30 

60 28 



Moft large. 

17 58 37 

103 24 



17 58 41 

118 57 



17 58 49 

122 17 


17 59 I 

108 8 



^7 59 19 

104 24 



18 13 

122 1 1 



18 3 49 

120 42 



JKo A» 

*>^ \f*i 


Mr. Herschel on the 






H. xM. S 
i8 5 17 
18 6 37 

18 7 4 
18 7 4 

18 7 37 

D. M. 
98 47 
go 36 
62 14 
56 16 
10^ 25 








Too fbon for gaging, not having been 
MoC; large. J long enough out 

lin the dark. 

18 10 7 
18 10 52 

! 18 II 49 
18 13 37 
18 13 52 

120 58 
61 8 

104 6 
104 16 

93 " 






Chiefly large. 

18 14 46 
18 15 28 

18 i6 52 
18 18 40 
18 19 37 

56 20 
92 42 
92 42 
92 42 

102 34 







18 20 7 
18 20 46 

18 21 I 
18 21 12 
18 21 31 

103 18 
92 42 

103 55 
90 41 

103 36 




18 22 4 
18 22 4 
18 22 19 
18 22 37 
18 24 3 

62 7 

56 16 
1 04 6 

lOj 45 
115 10 










Large and fmall. 

18 24 4 
18 24 7 
18 24 10 
18 24 43 
18 25 37 

109 35 

102 31 

92 59 

103 39 
102 34 


18 26 17 

18 26 25 
18 26 47 
18 27 I 

'8 27 55 

98 3 

103 57 

97 43 
120 58 

120 44 

\ 1 1 






Conftrudlion of the He an) em. 







Memor. ndums. 

H. M. S 

D. M. 

i8 28 7 
18 28 8 
18 28 25 

102 51 
91 44 

103 9 





Extremely fnnall. 
Moll: Iniall. 
Extremely fmall. 

18 28 37 
18 29 25 

122 25 

103 24 




Extremely fmall. 

18 29 47 
18 29 49 
18 30 34 
18 31 10 
18 31 10 

97 50 
121 39 

57 18 

92 42 

108 53 






I ' 




18 31 13 
18 31 17 
18 31 34 

103 19 

97 53 
62 34 






All fizes. 

Many more fnfpe6led. 
# Large and Imall. 

18 31 49 

18 r, 4 

121 39 

108 43 







18 33 7 
18 34 5 
18 34 47 
18 34 58 

18 36 34 

103 53 

98 34 

71 53 

60 41 

1 10 12 









Large and fmaU. 

18 36 34 
18 36 47 
18 37 34 
18 38 I 
18 39 40 

91 37 

72 28 

93 29 

104 14 

93 52 












18 40 28 
18 40 47 

18 41 22 
18 42 49 
18 43 17 

92 47 

71 48 

91 37 
121 39 

72 8 







Very clear for this altitude. 


18 43 33 

18 44 34 
j8 44 34 
18 47 32 
18 48 4 

1 19 21 

112 43 

60 34 

91 14 

1 10 12 








All fizes. 

VcL. L 





Mf\ Herschel on the 





Memorandums. 1 

H. M. S. 

D. M. 

1 8 50 16 

60 55 



Many of them fmall. 

18 51 4 

57 20 





18 51 32 

10^6 26 


5 . 

Strong twilight. 

18 52 49 

115 30 



18 54 4 

57 18 



iS 54 8 

91 14 



18 54 55 

104 23 



18 55 4 

108 41 



18 55 16 

62 31 



18 59 8 

91 14 




18 59 26 

72 37 



Too looa for gaging. 

19 I 2 

71 40 



19 I 34 

56 47 




19 2 29 

74 53 



^ Twilight. 

19 2 37 

103 16 



19 2 49 

121 39 



19 3 34 

55 56 




19 6 34 

61 8 




And manv fmall befides. 

19 7 34 

56 56 




19 7 52 

57 59 



19 8 38 

92 8 



19 9 37 

109 I 



19 9 40 

5(5 51 




19 12 59 

75 21 




19 13 50 

59 59 



19 »3 52 

59 29 



19 14 2 

72 15 




19 14 4 

61 21 



Too crowded for accuracy. 

19 H 55 

103 36 



Changeable focus^ 

19 15 40 

55 26 



D bright. 

19 16 50 

60 43 



19 16 59 

7S 23 




19 17 44 

108 12 



19 18 2^ 

78 9 





19 18 28 

61 21 






jtion oj 

IDS neavens, 23 j 





1 Memorandums. 


H. M. S. 
19 19 52 
19 19 55 
19 20 51 
19 21 I 
19 21 34 

D. M. 

57 t4 

108 J2 

<>o 55 

78 47 
55 ^7 







1) bright. 

19 22 27 
19 24 36 

19 24 49 
19 24 50 

19 24 53 

62 29 

56 49 

104 24 
60 43 

"3 51 








Ciiangeable focus. 

19 25 4 
19 25 16 
19 25 22 
19 25 -^■] 
19 27 36 

57 9 
64 18 

59 36 
^03 50 

72 34 







I 1 


D bright. 

Changeable focus. 
•^ Toofmall and too crowded to be cer- 

19 27 44 
19 28 I 
19 28 6 
19 28 52 
19 28 52 

61 8 

103 30 

55 49 

59 26 

5^ 47 









[tain of the number. 
Changeable focus. 

]) very bright. 

19 29 46 
19 30 36 
19 30 36 

19 3^ 33 
19 32 9 

65 10 

74 33 

54 53 

92 34 

109 44 










19 32 15 

19 33 4 

19 33 7 

19 33 14 
19 33 20 

62 3S 

55 34 

103 12 

61 8 
5B 59 








" * ' 



Changeable focus. 

19 34 51 

19 35 34 
19 36 6 

19 36 37 
19 36 50 

"5 44 
63 19 

54 57 
102 31 

60 35 











Changeable focus. 



■7 -^n 

Mr. Herschel o?2 the 






H. M. S. 

D. M. 


19 40 33 





19 40 46 

59 ^2 




19 40 48 

74 33 




19 42 33 

73 H 





19 43 30 

57 23 





19 43 56 

64 27 



Molt lar^e. 

19 45 36 

77 5^ 



^ Fault li . 

'^9 45 37 

103 3 



19 46 21 

73 14 





19 46 51 

115 44 



Strong twilight. 

.... . . 1 

19 47 8 

^0 3S 




19 47 18 

109 46 




19 47 22 

57 38 




Very unequally fcattcred,. 

19 49 6 

57 13 



19 49 48 

56 51 




19 SO 5 

92 39 



% Moft fmall. 

19 51 37 

62 37 



' 19 5^ 

57 15 




19 53 I 

60 35 



19 53 28 

63 40 



19 53 40 

54 59 




19 53 49 

121 39 



i 19 54 

55 12 




19 54 12 

78 3 



•^ Faint D . 

19 54 22 

59 58 



19 55 7 

62 41 



19 56 19 

60 44 




19 56 22 

57 17 



^9 57 19 

62 34 



19 57 40 

58 29 



19 59 49 

62 37 



20 21 

79 3 



9f Strong ]) .. 

20 24 

55 12 




20 25 

<^o 33 



Moft of the ftars extremely fmall. 

20 051 

ijc; 44 





Conjlriidllon of the Hea'-oens, 






H. M. S. 

D. INI. 

20 I 39 

79 34 



■^ Strong D . 

20 5 26 

56 34 




20 5 27 

72 56 




20 6 23 

J07 27 



20 6 43 

62 32 



Many fmall. 

20 8 26 

56 27 




20 8 27 

72 56 




20 8 58 

103 37 



20 9 6 

log 40 



20 9 52 

102 48 



20 12 22 

58 14 



20 17 20 

76 12 




Some t\viIio;ht. 

20 1 8 51 

1^5 44 




20 20 58 

61 27 



20 21 36 

71 28 




20 22 56 

56 27 




20 22 58 

103 26 



20 24 51 

115 44 




20 25 58 

103 26 



Changeable focus. 

20 25 59 

07 27 





20 26 I 

92 44 



20 26 46 

109 37 



Not clear. 

20 26 49 

121 39 



A little hazy. 

20 27 33 

96 7 



Moil fmall. 

20 34 51 

115 44 




20 35 53 

61 20 



20 37 1 8 

58 28 



20 37 34 

97 6 




20 38 I 

92 44 




20 39 42 

66 37 



20 40 22 

56 21 




, 20 41 II 

67 54 



20 41 56 

74 33 



20 42 59 

62 14 



1 20 43 I 

70 29 






Mr, Herschel on the 





Memorandums. \ 

H. M. S. 

D. M. 

20 43 30 

54 47 




Moil of the ftars of the fame fize. 

20 44 59 

70 6 



20 47 13 

60 46 



20 49 I 

92 44 




20 49 10 

57 II 





Mofl of a fize. 

20 50 59 

10-^ 26 



20 51 23 

68 30 



20 53 29 

103 26 



20 54 1 

107 47 



20 56 59 

103 26 



Moil: extremely fmall. 

20 57 55 

61 25 




20 59 I 

92 44 




21 I 6 

96 43 



^ Moft fmall. 

21 3 29 

66 39 



21 3 53 

73 9 



21 6 13 

69 23 



A little hazv. 

21 6 55 

103 32 

II, I 


21 7 49 

109 45 



21 7 59 

64 58 



21 9 25 

61 36 



Strong twilight. 

21 10 13 

60 39 



Strong twilight. 

21 II 17 

73 18 



21 II 42 

96 13 




21 12 I 

92 44 



21 IS 3 

109 56 



21 16 43 

59 7 



21 18 54 

57 20 



21 20 18 

96 43 




21 21 

107 49 



21 22 14 

76 33 



21 25 31 

92 44 




21 29 12 

83 II 



21 30 58 

78 57 



21 32 10 

57 H 



1 21 33 I 

92 44 



Strong txvilight. 


ConJiruBion of the Heavens. 





Stars. Fields. 


H. M. S. 

D. M. 

21 34 55 

97 17 




21 36 38 

65 55 



21 38 20 

65 38 



21 39 55 

96 17 




21 41 52 

58 42 



21 43 22 

109 5S 




21 45 4 

59 39 



21 48 22 

59 30 



21 51 52 

58 5& 



21 51 55 

97 17 

II. 5 


21 54 22 

109 55 




21 57 49 

59 37 




21 5§ 4 

75 7 



21 58 19 

59 6 



21 58 43 

58 34 




21 58 49 

58 20 



22 2 25 

60 9 



22 2 52 

109 55 




22 3 56 

71 48 



22 7 22 

109 55 




22 10 28 

75 2 



22 II 32 

97 H 



-}f Twilight. 

22 II 35 

65 48 



22 18 32 

97 H 



if. Twilight. 

22 20 35 

109 58 




22 20 55 

78 54 



Blight ]) . 

22 27 41 

95 4 



22 30 35 

109 58 




22 31 28 

73 59 



22 33 6 

76 52 



22 34 40 

61 56 



22 35 35 

109 58 

7' I 



22 36 49 

71 57 



22 39 41 
22 40 5 

82 5 



65 48 





Mr, Herschel on the 






H. M. S. 

D, M. 

22 43 SS 

60 9 



Faiat J 

22 45 3 

80 47 



2 2 45 30 

58 38 




22 48 49 

71 57 



22 52 9 

78 43 




22 52 41 

95 4 



22 55 40 

7i 54 



22 56 55 

67 53 



22 58 19 

78 42 




23 27 

113 12 



23 30 

58 38 




23 2 59 

65 50 



23 5 35 

109 58 




23 8 52 

95 I 



Mofl extremely fmall. 

23 10 4 

^4 SS 



23 II 40 

61 48 



23 12 40 

71 54 



23 17 50 




23 23 5S 

69 48 



23 25 32 

113 12 

3' I 



23 32 2 

69 Si 



23 33 20 

79 45 



23 43 2 

69 51 




23 44 47 

45 24 



23 46 52 

113 17 




23 46 55 

65 36 




23 59 21 

87 10 



123 59 56 

95 4 



P R O- 

ConJlruBlon of the Heavens* 241 


Thejiars being fuppofed to he nearly equally fcaitercd^ and their 
number, in a field oj view of a known angular diameter ^ being 
given, to determine the length of the vfual ^ay. 

Here, the arrangement of the flars not being fixed upon, we 
muft endeavour to find which way they may be pLiced io as to 
fill a given fpace moft equally. Suppofe a redangular cone 
cut Into fruftula by many equidiftant planes perpendicular to 
the axis ; then, if one fliar be placed at the vertex, and another 
in the axis at the firft interfedion, fix ftars may be fet around it 
fo as to be equally diftant from one another and from the cen- 
tral ftar. Thefe pofitions being carried on in the fame manner, 
we fiiall have every ftar within the cone furrounded by eight 
others, at an equal diflance from that ftar taken as a center. 
Fig. I. (tab. VIII.) contains four fedions of fuch a cone diftin- 
guilhed by alternate (hades, which will be fufficient to explain 
what fort of arrangement I would point out. 

The feries of the number of flars contained in the fe- 
veral fe£lions will be 1.7. 19. 37. 61. 91. &c. which 
continued to n terms, the fum of it, by the differential method, 

will ht na-\-n , "—— d' •\-n . ^— • —— d'\ &c. : where a is 


the firft term d\ d'\ d"\ &c. the ift, 2d, and 3d differences. 
Then, fince tf=i, ^'rz6, d''-6, d'" — o, the fum of the 
feries will be «\ Let S be the given number of ftars; i, the 
diameter of the bafe of the field of view ; and B, the 
diameter of the bafe of the great re(5l:angular cone ; and, by 

trigonometry, we (hall have Brn ^^^^ 1 field ' -^^^j fince the 
Vol. LXXV. I i ' field 

242 ■^'■^^'' Herschel o?2 the 

field of view of a telefcope is a cone, we fliall have its So- 
lidity to that of the great cone of ftars, formed by the above 
conftrudion as the fquare of the diameter of the bafc of the 
field of view, to the fquare of the diameter of the bafe of the- 
great cone, the height of both being the fame ; and the ftars in 
each cone being in the ratio of the lolidlty, as being equally fcat- 

tered (/^), we have«= a^B^S. And the length of the viiual 
ray = « - i, which was to be determined. 

(I) We ought to remark, that the periphery ?5nd bafe of the cone of the field 
of view, in g.^ging, would in all probability feldom fall exactly on fuch ftars as 
would produce a perfed equality of fituation between the liars contained in the 
fmalJ and the great cone; and that, confequently, the folution of this problem, 
where we fuppoie the ftars of one cone to be to thofe of the other in the ratio 
of the folidity on account of their being equally fcattered, wili not be ilricdy 
true. But it fliould be remembered, that in fmall numbers, where the different 
terminations of the fields would moft affeft this folution, the ftars in view have 
always been afcertained from gages that were often repeated, and each of which 
confiftcd of no lefs than tc-n fields fiiccellively taken, [o that the different deviations 
at the periphery and bafe of the cone vv^ould certainly compenfate each other 
fufficiently for the purpofe of this calculation. And that, on the other hand, in 
higli g^iges, which could not have the advantage of being fo often repeated, thefe 
deviations would bear a much fmaller proportion to the great number of ftars in 
a field of view j and therefore, on this account, fuch gages may very juftly be 
admitted in a folution where pradical truth rather than mathematical precifion 
is the end we have in view. It is moreover not to be fuppofed that we imagine 
the ftars to be aftually arranged in this regular manner, and, returning therefore 
to our general hypothefis of their being equally fcattered, any one field of view 
promifcuoufly taken may, in this general fenfe, be fuppofed to contain a due 
proportion of them; fo that the principle on which this folution is founded may 
therefore be faid to be even more rigoroufiy true than we have occafion to infill 
iipon in an argument of this kind. 


ConJlru^iUn of the liecivem, ' 243 

T^he fame other wfe. 

If a different arrangement of the flars flioulc! be felc'6tecL 
fuch as that in fig. 2. where one ftar is at the vertex of a cone^; 
three in the cuxu inference of the fuft feclion, at an equal dif- 
tance from the vertex and from each other •, lix in the circum- 
ference of the next fe£llon, with one in the axis or center; 
and fo on, always placing three ftars in a lower iecllon in fuch a 
manner as to form an equilateral pyramid with one above them: 
then we fhall have every ftar, which is fufRciently within 
the cone, furrounded by twelve others at an equal dlflance from 
the central ftar and from each other. And by the ditFerentlal 
method, the fum of the two feries equally continued, into 
which this cone may be refolved, will be 2/2^+ 1 i «^ + |«; 
where n flands for the number of terms in each feries. To 
find the angle which a line vx^ paffing from the vertex v over 
the flars t;, n^ b^ /, &c, to x, at the outhde of the cone, makes 
with the axis ; we have, by conftrudion, v i in fig. j. 
reprefenting the planes of the firft and fecond fedlions = 
2 X cof.30° = (p, to the radius p j, of the firfl fe£lion =; i . Hence 

it will be ^^' — 1 =vf = ivm ; or vm= 2 n/(P^ - i : and, by 
trigonometry, — ^rr=L=:T. Where T is the tangent of the 

required angle to the radius R (c) ; and putting / =: tangent of 

(c) In finding this angle we have fuppofed the cone to be generated by a 
revolving reftangvilar triangle of which the line vx^ fig. 2. is the hypotenufe ; 
but the ftars in the fecond feries will occafion the cone to be contained under a 
waving furface, wherefore the above fuppofition of the generation of the cone is 
not ftricftly true ; but then thefe waves are fo inconfiderable, that, for the pre- 
fent piirpofe, they may fafely be neglefted in this calculation. 

I i 2 half 

24^ Mr, Herschel ou the 

half the given field of view, it will be —=: B, the bafe of the 


cone. And — —^—d, will bean expreflion for vp, in terms 

of «yj-, which is the mutual diftance of the fcattered flars. 

Then having — — n^ j^ I n^ ■\- 1 ;?, we may find n ; whence 

idn - ^, the vifual ray, will be obtained. 

The refult of this arrangement gives a fhorter ray than that 
of the former ; but fince the difference is not {o confiderable as 
very materially to affe^Sl the conclufions, I (hall, on account of 
the greater convenience, make ufe of the firft. 

We inhabit the -planet of a Jlar belonging to a Compound 'Nebula 

of the third for tn, 

I fhall now proceed to fliew that the flupendous fidereal lyiLem 
we inhabit, this extenlive ftratum and its fecondary branch, 
confifthig of many millions of ftars, is, in all probability, a 
detached Nebula. In order to go upon grounds that feem to me 
to be capable of great certainty, they being no lefs than an 
ii£lual furvey of the boundaries of our iidereal fyflem, which 
I have plainly perceived, as far as I have yet gone round it, 
every where terminated, and in mofl places very narrowly too, 
it will be proper to fhew the length of my founding line, if I 
may fo call it, that it may appear whether it was fufticiently 
long for the purpofe. 

In the moft crowded part of the milky way I have had fields 
of view that contained no lefs than 588 ftars (^), and thefe were 
continued for many minutes, fo that in one quarter of an hour's 
time there pafled no lefs than 1 16000 ftars thiough the field of 

(-V) See the table of Gages, p. 235. 


ConJlni5lion of the Heavens. 24^ 

view of my telefcope (t'). Now, if we compute the length of 
the vKlial ray by putting S^jSS, and the dlnmtter of the 

field of view fifteen minutes, we fhall find ?i — s/B'S = 498 ; fo 
that it appears the length of what I have called my IbundingHne, 
or ;/- I, was probably not lefs than 49^ times the diftance of 
Sirius from the fun. The lame gage calculated by the fecond 

arrangement of ftars gives %/(??'— i = i. 41 421 ; 

Var — 

tangent of 31° 28' SS" yll ''^ "^ =B= 280,69; ~\-^ ^ d - 

,81649; — r=23i63409,7=i/2'4- I «'+ ? « ; where « = 284,8 

nearly; and zdn- 1 —464, the vifual ray. 

It may feem inaccurate that we fhould found an argum.enton 
the ftars being equally fcattered, when in all probability there 
mav not be two of them In the heavens, whole mutual didance 
fhall be equal to that of any other two given ftars ; but it fhould 
be confidered, that when we take all the flars colledlively there 
will be a mean diftance which may be afl'umed as the general 
one; and an argument founded on fuch a fuppofition will have 
in its favour the greateft probability of not being far fliort of 
truth. What will render the fuppofition of an equal diftribu- 
tion of the flars, with regard to the gages, ftill lefs expofed to 
objedions is, that whenever the flars happened either to be 
uncommonly crowded or deficient in number, fo as very fud- 

{e) The breadth of my fweep was 2° 26', to which muil be adtkd 15' for tvvo 

femi-diameters of the field. Then, putting 161 r:^, the number of fields in 

I 5 minutes of time ; ,7854 = ^, the proportion of a circle to i, its ciicumfcribed 

fquare; (frrfine of 74"" 22', the polar diftance of the middle of the fweep reduced 

to the prefent time ; and 588 =:S, the number of ftars in a field of view,, v/ehave 

«(pS , . . 

- — z: 110076 ftars, 

^^4-6 ^^^' Herschel on the 

denly to pafs over from one extreme to the other, the gages 
were redoced to other forms, fuch as tiie border gage, the 
diftaiice-gage, &c. which terms, and the ule of fuch gages, 
I (hall hereafter find an opportunity of explaining. And none 
of thoie kinds of gages have been admitted in this table, which 
contifts only of fuch as have been taken in places v/here the 
liars a|)parently leemed to be, in general, pretty evenly fcat- 
tercd ; and to increafe and decreafe in number by a certain gra- 
dual piogreffion. Nor has any part of the heavens containing 
a clufter of ftars been put in the gages ; and here I mufi: ob- 
lerve, that the difference between a crowded place and a clufter 
may eaiily be perceived by the arrangement as well as the fize 
and mutual diilance of the fears ; for in a clufter they are 
generally not only refembling each other pretty nearly in fize, 
but a certain uniformity of diilance alfo takes place ; they are 
more and more accumulated towards the center, and put on all 
the appearances which we fhould naturally expevfl from a num- 
ber of them colle6led into a group at a certain diiliance from 
VIS. On the other hand, the rich parts of the milky way, as 
well as thofe in the diftant broad part of the ftratum, confifh 
of a mixture of ffars of all poifible fizes, that are feemingly 
placed without any particular apparent order. Perhaps we might 
recolle6l, that a greater condenfation towards the center of our 
fyftem than towards the borders of it fhould be taken into con- 
fideration; but, with a nebula of the third form, containing 
fuch various and extenfive combinations, as I have found to 
take place in ours, this circumftance, which in one of the firfl: 
form would be of coniiderable moment, may, I think, be 
fafely negledted. However, I would not be underftood to lay 
a greater ftrefs on thcfe and the following calculations than the 
principles on which they are founded wdll permit ; and if here- 

Conjiruclion cf the Heavens^ i\ j 

after we fliall find rcafoii, from experience and obfervation, to 
believe that there are parts of our {y{k&m: where the ftars are 
not fcattered in the manner here fuppofed, we ought then to 
make proper exceptions. 

But to return : if Ibme other high gage be fele6led from the 
table, inch as 472 or 34^, the length of the vifual ray will be 
found 461 and 415. And although, in confequence of what 
has been faid, a certain degree of doubt may be left about the 
arrangement and fcattering of the flats, yet when I recolle£l, 
that in thofe parts of the milky way where thefe high gages 
were taken, the flars were neither fo fmall, nor fo crowded, 
as they mufl: have been on a fuppolirion of a much far- 
ther continuance of them, wdien certainly a milky or ne- 
bulous appearance muft have come on, 1 need not fear to have 
over-rated the extent of my vifual ray. And indeed every 
thins: that can be faid to fliorten it will onlv contnicl the limits 
of our nebula, as it has in moft places been of fufficieut length 
to go far beyond the bounds of it. Thus, in the fides of the 
ftratum oppofite to our fituatlon in it, where the gages often 
run below 5, our nebula cannot extend to 100 times the dif- 
tance cf Sirius ; and the fame telefcopc, which could fhew 588 
ftars in a field of view of 15 minutes, muft certainly have pre- 
fented me alfo with the flars in thefe fituations as well as the 
former, had the}^ been there. If we fhould anfwer this by ob- 
ferving that they might be at too great a diftance to be per- 
ceived, it will be allowing that there mufl at leafl be a vacancy 
amounting to the length of a vifual ray not fhort of 400 tlmiCS 
the dlflance of Sirius ; and this is amply fuflicient to make our 
nebula a detached one. It is true, that it would not be con- 
fiftent confidently to affirm that we were on an iOand unlefs 
we had adually found ourfelves every where bounded by the 


248 Mr, Herschel on the 

ocean, and therefore I fhall go no farther than the gages will 
authorlfe ; but confideruig the little depth of the ftratum in 
all thofe places which have been aftually gaged, to which muft 
be added all the intermediate parts that have been viewed and 
tonud to be much like the reft, there is but little room toexpedt 
a connection between our nebula and any of the neighbouring 
ones. I ouglit alio to add, that a telefcope with a much larger 
aperture than my preient one, grafping together a greater quan- 
tity of light, and thereby enabling us to fee farther into fpace, 
will be the lureft means of compleating and eftablifliing the 
arguments that have been ufcd : for if our nebula is not abfo- 
lutely a detached one, I am firmly periuaded, that an inftru- 
rnent may be made large enough to difcover the places where 
the ftars continue onwards. A \txy bright milky nebulofity 
niufl there undoubtedly come on, fuice the ftars in a field of view 
will increafe in the ratio of n\ greater than that of the cube 
of the vifual ray. Thus, if 588 frars in a given field of viev/ 
are to be Icen by a ray of 497 times the diftance of Sirius ; 
when this is lengthened to 1000, which is but little more 
than double the former, the number of flars in the fame field 
of view will be no iels than 4774 : for when the vifual ray r 

is given, the number S of flars will be::=^; where 72 — r+ i ; 

and a telefcope with a three-fold power of extending into fpace, 
or with a ray of, 1500, which, I think, may eafily be con- 
flrufted, will give us 16096 ftars. Now, thefe would not be 
fo clofe but that a good power applied to fuch an inftrument 
might eafily dlftinguifh them ; for they need not, if arranged 
in regular Spares, approach nearer to each other than 6^^,27; 
but what would produce the milky nebulofity which I have 
■mentioned is the numberlefs flars beyond them, which in one 


Confirudtlon of the Heavens* 249 

refpe£t the vifual ray might alfo be faid to reach. To make 
this appear we muft return to the naked eye, which, as wc 
have before eftimated, can only fee the flars of the feventh 
magnitude fo as to diftlnguifh them ; but It is neverthelels very 
evident that the united luftre of millions of flars, iuch as [ 
fuppofe the nebula in Aiidromedato be, will reach our fight in 
the fhape of a very fmall, faint nebuloiity ; fmce the nebula of 
which I fpeak may eafiiy be ittw in a line evening. In the 
■fame manner my prefent telefcope, as I have argued, has not 
only a vifual ray that will reach the flars at 497 times the dif- 
tance of Sirius fo as to diftinguifh them (and probably much 
farther), but alfo a power of iliewing the united luilre of the 
accumulated flars that compofe a milky nebulofity, at a diilance 
far exceeding the former limits ; fo that from thelc conildera- 
tions it appears again highly probable, that my prefent telefcope, 
not fhewing fuch a nebulofity in the milky way, goes already far 
beyond its extent : and conlequently, much more would an 
inftrument, fuch as I have mentioned, remove all doubt on 
the fubje£t, both by fhewing the flars in the continuation of 
the flratum, and by expofing a very flrong milky nebuMty 
beyond them, that could no longer be miflaken for the dark 
ground of the heavens. 

To thefe arguments, which refl on tlie firm bafis of a feries 
of obfervation, we may add the following confiderations drawn 
from analogy. Among the great number of nebuliE which I 
have now already feen, amounting to more than 900, there 
are many which in all probability are equally extenfive with 
that which we inhabit ; and yet they are all feparated from each 
ether by very confiderable intervals. Some indeed there are 
that feem to be double and treble.; and though with moll of 
thefe it may be, that they are at a very great diilance from each 

Vol. LXXV. K k ' other. 

2^o Mr. Herschel on the 

other, yet we allow that fome fuch conjun<£lions really arc to 
bs found ; nor is this what we mean to exclude. But then 
thefe .compound or double nebulae, which are thofe of the third 
and fourth forms, flill make a detached link in the great chain. 
It is alfo to he fuppofed, that there may fti!l be fome thinly 
fcattered folitarv flars between the lar^e interftlces of nebulse, 
which, beuig fituated fo as to be nearly equally 2ttYd.0:ed. by the 
feverai clufters when they were forming, remain unaffociated. 
And though we cannot expect- to fee thele ftars, on account of 
their vaft diftance, yet we may well prefum.e, that their num- 
ber cannot be very contiderable in com-parifon to thofe that are 
already drawn into fyflems ; which conjetlure is alfo abun- 
dantly confirmed in fituatlons where the nebulas are near enough 
to have their flars vifible ; for they are all infulated, and gene- 
rally to be i'een upon a very clear and pure ground, without 
any ftar near them that might be fuppofed to belong to them. 
And though I have often feen them in beds of flars, yet from 
the fize of thefe latter we may be certain, that they were 
much nearer to us than thofe nebulae, and belonged undoubtedly 
to our own fyftem. 

A delineation of our nebula, by an application of the gages 
in the manner which has been propofed to be done In my for- 
mer paper, may now be attempted, and the following table is 
calculated for this purpofe. It gives us the length of the vifual 
ray for any number of ftars in the field of view contained in 
the third column of the foregoing table of gages from _V to 
100000. If tlie number required is not to be found in the iirft 
4 column 

ConJlru6lion of the Heavens, 251 

column of this table, a proportional mean may be taken be- 
tween the two neareft rays in the fecond column, without any 
material error, except in the few laft numbers. The calcula- 
tions of refolvable and milky nebulofity, at the end of the 
table, are founded, the firft, on a fuppofition of the ftars 
being fo crowded as to have only a fquare fecond of fpace 
allowed them; the next afligning them only half a fecond 
fquare. However, we (hould confider that in all probability a 
very different accumulation of flars may take place in different 
nebulae ; by which means fome of them may aflume the milky 
appearance, though not near fo far removed from us ; while 
clufters of ffars alfo may become refolvable nebulas from the 
fame caufe. The diflindnefs of the inflrument is here alfo 
concerned ; and as telefcopes with large apertures are not eafily 
brought to a good figure, nebulous appearances of both forts 
may probably come on much before the diflance annexed to 
them in the table. 

K k 2 TABLE 


Mr, Herschel on the 

TABLE 11. 

Stars in 









Ray. • 

the field 

T-'l «' 


'' T 







551 . 








1 o,2 









57 3 i 











• o,4 








1 0000 










I 00000 



























































































































































































































j 03 
















♦ 25 

















































ConftniLt'iGn of the Heavens. 253 

SeSlJon of our fidereal fyjienu 

By taking out of this table the vlfnal rays which anfwcr to 
the gages, and applying lines proportional to them around a 
point, according to their refpeclive right afcenfions and north 
polar diftances, we may delineate a folid by means of the ends 
of thefe lines, which will give us fo many points in its fur- 
face ; 1 Ihall, however, content myfelf at prefent with a fec- 
tion only. I have taken one which paflcs through the poles of 
our fyftem, and is at re6tangles to the conjunction of the 
branches which I have called its length. The name of poles 
feemed to me not improperly applied to thofe points which are 
90 degrees diftant from a circle pafling along the rnilky way, 
and the north pole is here affumed to be lituated in R,A. 186^ 
and P.D. 58°. The fe6tion reprefented in fig. 4. is one which 
makes an angle of ^^S degrees with our equator, c roiling it in 
124I and 3041 degrees. A celeftial globe, . adj ufted to the lati- 
tude of 55° north, and having a- Ceti near the meridian, will 
have the plane of this fedlion pointed out by the horizon, and 
the gages which have been ufed in this delineation are thofe 
which in table I., are marked by. afleriiks. When the vifual 
rays anfwering to them are taken out of the fecond table, they 
mufl:' be proje6led on the plane of the horizon of the latitude 
which has been pointed out ; and this may be done accurately 
enough for the prefent purpofe by a globe adjufted as above di^ 
reeled; for as gages, exadlly in the plane of the feclion, were 
often wanting, 1 have ufed many at lome fmall dllfance above 
and below the fame, for the fake of obtalninf7 more delineatino; 
points ; and in the figure the flars at the borders which are 
larger than the reft are thofe pointed- out by the gages. 1 hi 
2 , inter- 

2 cd Mr. Herschel on the 

intermediate parts are filled up by fmaller fiars arranged in 
iT:raiglit lines between the gaged ones. The delineating points, 
though pretty nuinerous, are not fo clofe as wc might wifh ; 
it is however to be hoped that in fome future time this 
branch of aftronomy will become more cultivated, fo that we 
may have gages for every quarter of a degree of the heavens at 
lead, and thefe often repeated in the moft favourable circum- 
ftances. And whenever that fhall be the cafe, the delineations 
may then be repeated with all the accuracy that long experience 
may enable us to Introduce ; for, this fubjed being fo new, I 
look upon what is here given partly as only an example to 
illuftrate the fpirit of the method. From this figure how- 
ever, which I hope is not a very inaccurate one, we may fee 
that our nebula, as we obferved before, is of the third form ; 
that is : A very extenjive, branchings compound Congenes of 
many millions of Jiars \ which moft probably owes its origin to 
many remarkably large as well as pretty ciofely fcattered fmali 
liars, that may have drawn together the reft. Now, to have 
fome idea of the wonderful extent of this fyftem, I mufl ob- 
ferve that this fe£Hon of it is drawn upon a fcale where the 
diflance of Sirius is no more than the 8oth part of an inch ; fo 
that probably all the ftars, which in the fineft nights we are 
able to diftinguifh with the naked eye, may be comprehended 
within a fphere, drawn round the large ftar near the middle, 
reprefenting our fituation in the nebula, of lefs than half a 
quarter of an inch radius. 

The Origin of nebulous Strata. 

If it wete poflible to diftingulfh between the parts of an 
indefinitely extended whole, the nebula we inhabit might be 


ConJlruSlion of the Heavens. . 255 

faid to be one that has fewer marks of profound antiquity upon 
it than the reft. To explain this idea perhaps more clearly, we 
fhould recoiled that the condenlation of clufters of ftars has 
been afcribed to a gradual approach ; and whoever refle6ls on 
the numbers of nges that muft have paft before fome of the 
clufters, that will be found in my intended catalogue of them, 
could be fo far condenfed as we find them at prcfent, will not 
wonder if I afcribe a certain air of youth and vigour to many 
very regularly fcattered regions of our fidereal ftratum. There 
are moreover many places in it where there is the greateft 
reafon to believe that the ftars, if we may judge from ap- 
pearances, are now drawing towards various fecondary centers, 
and will in time feparate into different clufters, fo as to occa- 
fion many fub-divifions. Hence we may furmife that when a 
nebulous ftratum confifts chiefly of nebuliE of the firft and fe* 
cond form, it probably owes its origin to what may be called 
the decay of a great compound nebula of the third form ; and 
that the fub-divifions, which happened to It in length of time, 
cccafioned all the fmall nebulae which Iprung from it to lie in a 
certain range, according as they were detached from the pri- 
mary one. In like manner our fyftem, after numbers of ages, 
may very poflibly become divided fo as to give rife to a ftratum 
of two or three hundred nebula ; for it would not be difficult 
to point out fo many beginning or gathering clufters in It (/). 
This view of the prefent fubje^l throws a confiderable light 
upon the appearance of that remarkable coUedlion of many 

(y) Mr. MicHELL has alfo confidered the ftars as gathered together info 
groups (Phil. Tranf. voU LVII. p. 249.) j which idea agrees with the fub-diviCcn 
of our great fyftem here pointed out. He founds an elegant proof of this on 
the computation of probabilities, and mentions the Pleiades, the Pra*fepc Cancri, 
and the nebula (or chifter of ftars) in the hilt of Perfeus's fuord, as inftanccr. 


256 Mr, Herscviel on the 

hundreds of nebulae which are to be feen in what I called 
: the nebulous flratum of Coma Berenices. It appears from the 
extended and branching figure of our nebula, that there is room 
for the decompofed fmail nebula of a large, reduced, former 
great one to approach nearer to us in the fides than in other 
parts. Nay, pofiibly, there might originally be another very- 
large joining branch, which in time became feparated by the 
condenfation of the ftars ; and this may be the reafon of the 
! little remaining breadth of our fyftem in that very place: for 
. the nebulae of the ftratum of the Coma are brightcfh and mofi: 
crowded juft oppofite our fituation, or in the pole of our fyflem. 
As foon as this idea was fuggefted, I tried alfo the oppofite pole, 
where accordingly I have met with a great number of nebula, 
1 though under a much more fcattered form. 


jtin'Opening in the heavens, 

^ Some, parts of our fyftem indeed feem already to have fuf- 

"tained greater ravages of time than others, if this way of ex- 

prefling myfelf may be allowed ; for inftance, in the body of 

the Scorpion is an opening, or hole, which is probably owing to 

this caufe. 1 found it while I was gaging in the parallel from 

112 to 114 degrees of north polar diftance. As I approached 

the milky way, the gages had been gradually running up from 

9,7 to 17,1 ; when, all of a fudden, they fell down to nothing, 

a very few pretty large ftars excepted, which made them Ihew 

0,5, 0,7, 1,1, 1,4, 1,8; after which they again rofe to 4,7, 

13,5, 20,3, and foon after to 41,'T. This opening is at leaft 

4 degrees broad, but its height I have not yet afcertained. It 

.is remarkable, that the 80 Nebuleufe fans eto'iks of the Con^ 

mo'ijance des Tewps, which is one of the richeft and mofl com- 


ConfiruSlwn of the Heavens, 2^j 

prefled cluHers of fmall ftars I remember to have feen, is 
{ituated juft on the weftern border of it, and would ahnoft au- 
thorife a fufpiclon that the liars, of which it is compofed, were 
collected from that place, and had left the vacancy. What adds 
not a little to this furmife is, that the fame pha?nomcnon is 
once more repeated \vith the fourth clufter of ftars of the 
Connoijfance dcs Temps ; which is alfo on the weftern border of 
another vacancy, and has moreover a fmall, miniature clufter, 
or eafily refolvable nebula of about 2| minutes in diameter, 
north following it, at no very great diftance. 

Phenomena at the Poles of our Nebula, 


I ought to obferve, that there is a remarkable purity or clear- 
nefs in the heavens when we look out of our flratum at the 
fides; that is, towards Leo, Virgo, and Coma Berenices, on one 
hand, and towards Cetus on the other ; whereas the ground 
of the heavens becomes troubled as we approach towards the 
length or height of it. It was a good while before I could 
trace the caufe of thefe ph^enomena ; but (ince I have beeii 
acquainted with the fhape of our fyftem, it is plain that thefe 
troubled appearances, when vv^e approach to the fides, are eafily 
to be explained by afcribing them to fome of the diilant, flrag- 
gling ftars, that yield hardly light enough to be difl:inguiOied. 
And 1 have, indeed, often experienced this to be a£lually the 
caufe, by examining thefe troubled fpots for a long w^iile toge- 
ther, when, at laft, I generally perceived the flars which occa- 
fioned them. But when we look towards the poles of our 
fyflem, where the vifual ray does not graze along the fide, the 

Vol. LXXV. L i flragglin 


2c^S Mr. Herschel on iht 

ftraggling ftars of coiirfe will be very few in number ; ancl^ 
therefore the giound of the heavens will aflume that purity 
which 1 have always obferved to take place in thofe regions. 

Enumeration of very compowid Nebula or Milky^Ways, 

As we are ufed to call the appearance of the heavens, whers- 
it is furrounded Vv'ith a bright zone, the Milky-V/ay, it may 
not be amifs to point out fome other very remarkable Nebulas- 
which cannot well be lefs, but are probably much larger thaiv 
our own fyftem ; and, being alfo extended, the inhabitants oF 
the planets tliat attend the ftars which compofe them muft 
likewife perceive the fame phenomena. For which reafon they 
may alfo be called milky-ways by way of difiindlion. 

My opinion of their fize is grounded on the following ob- 
fervations. There are many round nebulae, of the firil: form,. 
of about five or fix minutes in diameter, the flars of which I^ 
can lee very diftindlly ; and on comparing them with the vifual 
yay calculated from fome of my long gages, I fuppofe, by the ap- 
pearanceof the fmall ftars in thofe gages, that the centers of thefe 
round nebulae may be 600 times the diflance of Sirius from us. 

In eftimatins; the diflance of luch cluflers I confulted- 
rather the comparatively apparent fize of the fl-ars than 
their mutual diftance; for the condenfation in thefe cluifers- 
being probably much greater than in our own fyftem, if we 
"were to overlook this circumfi:auce and calculate b}^ their appa- 
rent compreffion, where, in about fix minutes diameter, there 
are perhaps ten or more ftars in the line of meafures, we fhould 
find, that on the fuppofition of an equal fcattering of the flars- 
throughout all nebulae, the diflance of the center of fuch a 
clufter from us could not be lefs than 6000 times the diflance 


Conflrii^llon of the Ihavehs, i^p' 

of Sirius. And, perhaps, in putting it, by the apparent iize 
of the flars, at 600 only, I may have conliderably under-rated 
it ; but my argument, if that ihould be the cafe, will be fo 
much the ftronger. Now to proceed, 

Some of thefe round nebulae have others near them, perfeiflly 
fuiiilar in form, colour, and the diftribut'ioii of flars, but of only 
half the diameter: andthe flars in them fecm to be doubly crowded, 
and only at about half the diilance from each other : they arc 
indeed lb fmall as not to be vifible without the utmoft attention, 
I fuppofe thefe miniature nebulae to be at double the diftance of 
the tirft. An inifance, equally remarkable and inflruclive, is 
a cafe where, in the neighbourhood of two fuch nebulas as 
have been mentioned, I met with a third, fimllar, refolvable, 
but much fmaller and feiinter nebula. The flars of it are no 
longer to be perceived ; but a refemblance of colour with the 
former two, and its diminished fize and light, may well per- 
mit us to place it at full twice the diiliance of the fecond, or 
about four or five times that of the lirfl:. And yet the nebil- 
lofity is not of the milky kind ; nor is it {o much as difficultly 
refolvable, or colourlefs. Now, in a few of the extended ne- 
bulae, the light changes gradually fo as from the refolvable to 
approach to the milky kind ; which appears to me an indica- 
tion that the milky light of nebulae is owing to their much 
greater diflance. A nebula, therefore, whofe light Is perfedlly 
milky, cannot well be fuppofed to be at lefs than fix or eight 
thoufand times the diflanCe of Sirius ; and though the numbers 
here afiumed are not to be taken otherwife than as very coarfe 
eftimates, yet an extended nebula, which in an oblique fitua- 
tiofl, where it is poffibly fore-fhortened by one-half, two-thirds, 
or Hiree- fourths of its length, fubtends a degree or more in 
♦ L 1 i; diameter, 

i6o Mr. Herschel on the 

diameter, cannot be otherwife than of a wonderful magnitude, 
and may well outvie our milky-way in grandeur. 

The firft I (hall mention is a milky Ray of more than a de- 
gree in length. It takes k (Fl. 52.) Cygni into its extent, to 
the north of which it is crookedly bent fo as to be convex 
towards t'le following fide ; and the light of it is pretty intenfe. 
To the fouth of k it is more diffufed, lefs bright, and lofes 
itfelf with iome extenfion in two branches, I believe ; but for 
want of light I could not determine this circumftance. The 
northern half is near two minutes broad, but the fouthern is 
not fufficiently defined to afcertain its breadth. 

The next is an extremely faint milky Ray, above | degree 
long, and 8 or io^ broad; extended from north preceding to 
fouth following. It makes an angle of about 30 or 40 degrees 
with the meridian, and contains three or four places that are 
brighter than the reft. The flars of the Galaxy are fcattered 
over it in the fame manner as over the reft of the heavens. It 
follows £ Cygni 1 1,5 minutes in time, and is 2° 19^ more fouth. 

The third is a branching Nebulofity of about a degree and a 
half in right afcenlion, and about 48^ extent in polar diftance. 
The following part of it is divided into feveral ftreams and 
windings, which, after feparating, meet each other again 
towards the fouth. It precedes f Cygni i6' in time, and is 
1° 16^ more north. I fuppofe this to be joined to the preceding 
one ; but having obferved them in different fweeps, there was 
no opportunity of tracing their conne£llon. 

The fourth is a faint, extended milky Ray of about i^^'In 
length, and 12' in breadth. It is brighteft and broadeft in the 
middle, and the ends lofe themfelves. It has a fmall, round, 
very faint nebula juft north of it; and alfo, in another place, 
a fpot, brighter than the reft, almoft detached enough to form 

a different 

Conjlruciton of the Heavens, 261 

a different nebula, but probably belonging to the great one. 
The Ray precedes a Trlanguli 18', 8 in time, and is 55' more 
north. Another obfervation of the fame, in a finer evening, 
mentions its extending much farther towards the fouth, and' 
that the breadth of it probably is not lefs than half a degree ; . 
but being (liaded away by imperceptible gradations, it is ditii-- 
cult exactly to affign its limits. 

The fifth is a Streak of light about 27'' long,, and in the 
brlghteft part 3 or 4^ broad. The extent is nearly in the meri- 
dian, or a little from fouth preceding to north following. It 
follows jS Ceti 5^,9 in time, and is 2° 43'' more fouth. The 
fituation is {q low, that it would probably appear of a much 
greater extent in a higher altitude. 

The lixth is an extenfive milky Nebulofity divided into two 
parts; the moil north being the ftrongeft. Its extent exceeds 
15'; the fouthern part is followed by a parcel of ftars which 
1 fuppofe to be the 8th of the Cunnoijfance des Temps,, 

The feventh is a wonderful, extenlive Nebulofity of the milky 
kind. There are feveral ftars vifible in it, but they can have 
no connection with that nebulofity, and are, doubtlefs, belong- 
ing to our own fyflem fcattered before it. It is the 17th of 
the Connoijfance des Temps, 

In the lift of thefe muft alfo be reckoned the beautiful Ne- 
bula of Orion. Its extent is much above one degree ; the 
eaftern branch paffes between two very fmall ftars, and runs on 
till it meets a very bright one. Clofe to the four fmall itars, 
which can have no connection with the nebula, is a total black- - 
nefs ; and within the open part, towards the north-eaftj is a 
diftind, fmall, faint nebula, of an extended (hape, at a diftance 
from the border of the great one, to which it runs in a. parallel 
4 ^ direction,, 

'2%i Mr. Herschel on the 

direction, refembling the (hoals that are feen near the coafts of 

fome iflands. 

The nhith is that hi the girdle of Andromeda, which is un- 
doubtedly the nearefl: of all the great nebulse ; its extent is 
above a degree and a half in length, and, in even one of the 
narrowed places, not lefs than i6^ in breadth. The brighteft 
part of it approaches to the refolvable nebuloiity, and beghis 
to fliew a faint red colour ; which, from many obfervations on 
the colour and magnitude of nebuliE, J believe to be an indica- 
tion that its diflance in this Coloured part does not exceed 2000 
times the diflance of Sirius. There is a very confiderable, 
broad, pretty faint, fmali nebula near it ; my Sifter difcovered 
it Augufl: 27, 178 ;, with a Newtonian 2-feet fweeper. It flicws 
the fame faint colour with the great one, and is, no doubt, in 
the neighbourhood of it. It is not the 3 2d of the Connoiffance' 
des Temps ; which is a pretty large round' nebula, much con- 
denfed in the middle, and fouth following the great one ; but 
this is about two-thirds of a degree north preceding it, in a 
line parallel to /3 and v Andromedie. 

To thefe may be added the nebula in Vulpecula : for, though 
its appearance is not large, it is probably a double flratum of 
ftars of a very great extent, one end whereof is turned towards 
us. That it is thus fituated may be furmifed from its contain- 
ing, in diiferent parts, nearly all the three nebulofities ; viz. 
the refolvable, the coloured but irrefolvable, and a tin6lure of 
the milky kind. Now, what great length muft be required to 
produce thefe effects may eafily be conceived when, in all pro- 
bability, our whole fyftem, of about 8co ftars in diameter, if 
it were feen at fuch a diftance that one end of it might aliume- 
the refolvable nebulofity, would not, at the other end, prefent 


ConJiruBlm of the Heavens. 2^7 

lis with the irrefolvable, much lefs with the colourlefs and 
ir.ilky fort of nebuJofities. 

ud Perforated Nebula, or Ring of Stars., 
Among the curiofities of the heavens (hould be placed a 
nebula, that lias a regular, concentric, dark Ipot in tiie middle, 
and is probably a Ring of liars. It is of an oval {hape, the 
iliorter axis being to the longer as about 83 to 100 ; fo that, if 
the ftars form a circle, its inclination to a line drawn from the 
lun to the center of this nebula mufl be about ^6 degrees. The 
light is of the refolvable kind, and in the northern fide three 
very faint ftars may be feen, as alfo^ one or two in the fouthern 
part. The vertices of the longer axis feem lefs bright and not 
fo well defined as the reft. There are feveral fmall ftars verv 
near, but none that feem to belong to it. It is the 57th of 
the CQfinoiJjance des Temps, Fig. 5. is a reprefentation of it.. 

Planetary Nebula. 

I fhall conclude this paper with an account of a few hea- 
venly bodies, that from their lingular appearance leave me almofl; 
in doubt where to clafs them. 

The tirft precedes v Aquarii k^' ^^ in time, and is i^ more 
Horth. Its place,, with regard to a fmall ftar Sept. 7, 1782, 
was, Diftance 8^ j 3^^ S^^^' '•> ^^^ °" account of the low iituation, 
and other unfavourable circumftances, the meafure cannot be 
very exaft. Auguft 25, 1783, Diftance 7' 5'^ ii-^\ veryexa^l^, 
and to my fatisfatlion ; the light being thrown in by an opaque- 
microicoplc-illumination (^). Sept. 20, 1783, Pofition 41° 24' 


{g) It may be of ufe to explain this kin^ of illumination for which the New- 
tonian refleftor is admirably conftrudtetl. On the fide oppofite the eye-piece an 
©pening is to be made in the tube, through which the light may be thrown in, fo 
a* to fall on fome refleding body, or concave perforated mirror, within the eye- 


264 Mr , H r, R scH E L m the 

fouth preceding the fame flar ; very exad, and by the fiime 
kind of illumination. Od., 17, i7^'3, Diftance 6' 55^'' 7'''^ ; 
a iecond mealure 6^ 56^^ 11'''''', ns exact as poflible. Od. 23, 
i 783, l^ofjtion 42^ 57^ ; a fecond meafure 42° 45^ ; fingle lens ; 
power 71 ; opaque microfcopic-illumination. Nov. 14, 1783, 
Diflance 7' 4'' 35"" Nov. 12, 1784, Diflance 7^ 22'^ 35"^^ ; 
Pofition 38'' 39^ Its diameter is about loor 15^''. I haveexa- 
miiicd it with the powers of 71, 227, 278, 460, and 932 ; 
nnd it follows the law^s of magnifying, fo that its body is no 
illuf on of light. It is a little oval, and in the 7-feet reflector 
pretty well defined, but not fharp on the edges. In the 20-feet, 
of 18,7 inch aperture, it is much better defined, and has much 
of a planetary appearance, being all over of an uniform bright- 
nefs, in which it differs from nebulae : its light feems however 
to be of the ftarry nature, which fuffers not nearly fo much as 
the planetary difks are known to do, when much magnified. 

The fecond of thefe bodies precedes the 13th of Flam- 
steed's Andromeda about 1^6 in time, and is 22^ more fouth. 
It has a round, bright, pretty well defined planetary difk of 
about 12^^ diameter, and is a little elliptical. When it is viewed 
with a 7-feet reflector, or other inferior inftruments, it is not 
nearly fo well defined as with the 20-feet. Its lituation with 
regard to a pretty confiderable flar is, Diftance (with a com- 
pound glafs of a low power) f 51^^34^^'. Pofition i2°o' f. 
preceding. Diameter taken with 278, 14^'' 42^^^. 

The third follows B (Fl. 44.) Ophiuchi 4^,1 in time, and 
is 23^ more north. It is round, tolerably well defined, and 
pretty bright ; its diameter is about 30^^ 

piece, that may throw it back upon the wires. By this means none of the direct 
rays can reach the eye, and thofe few which are reflefted again from the wires do 
not interfere fenfibly with the fainteft objeds, which may thus be fecn undif- 
turbed. \ 


CojifruBwn of the Heavens, 26 c 

The fourth follows -/j Sagittal iy\i in time, and is 2' more 

north. It is perfeclly round, pretty bright, and pretty well 

defined ; about | min. in diameter. 

The fifth follows the zift Vulpeculaj 2.\i in time, and is 

1° 46^ more north. It is exa6llv round, of an equal Ijoht 

• J. O 

throughout, but pretty faint, raid about i' in diameter. 

The fixth precedes h {Fi... 39,) Cygni 8^,1 in time, and is 

1° 26'' more louth. It is perfeftly round, and of an equal 

light, but pretty faint ; its diameter is neari", and the edges 

are pretty well defined. 

The planetary appearance of the two firfl is fo remarkable, 
that we can hardly fuppoie them to be nebulae ; their light is 
fo uniform, as well as vivid, the diameters fo fmall and well 
defined, as to make it almofl: improbable they fhould belong to 
that fpecies of bodies. On the other hand, the effe^Sl of dif- 
ferent powers feems to be much againft their light's being of a 
planetary nature, fince it preferves its brightnefs nearly in the 
fame manner as the ftars do in iimilar trials. If we would fup- 
pofe them to befingle fliars with large diameters we fhall find it 
difficult to account for their not being brighter ; unlefs we 
fhould admit that the intrinfic light of fome ftars may be very 
much inferior to that of the generality, which however can 
hardly be imagined to extend to fuch a degree. We might 
fufpe6t them to be comets about their aphelion, if the bright- 
nefs as well as magnitude of the diameters did not oppofe this 
idea ; fo that after all, we can hardly find any hypotheiis fo 
probable as that of their being Nebulic ; but then they mufh 
coniift of ftars that are comprefled and accumulated in the 
higheft degree. If it were not perhaps too hazardous to purfue 
a former lurmife of a renewal in what I figuratively called the 
Laboratories of the univerfe, the f!:ars forming thefe extraordi- 
nary nebulae, by fome decay or wafte of nature, being no longer 
Vol. LXXV. U m fit 

2,66 Mr. Herschel on the Conjlruciion of the Heavens. 

fit for their former purpofes, and having their projedile forces^ 
if any i'uch they had, retarded in each others atmolphere, may 
rufh at Lift together, and either in fuccefiion, or by one general 
tremendous iliock, unite itito a new body. Perhaps the ex- 
traordinary and iudden biaze of a new ftar in Cailiopea's chair, 
in 1572, miglit pofiibly be of fuch a nature. Butleil I Ihould 
be led too flir from the path of obfervation, to which I am 
refolved to Umit mylelf, 1 fliall only point out a confiderable 
ufe that may l>€ made of thele curious bodies. If a little atten- 
tion to them ihould prove that, iiavlng no annual parallax, they 
belong moft probably to the clafs of nebulae, they may then 
be expe^^ed to keep their fituation better than any one of the 
ftars belonging to our lyftem, on account of their being pro- 
bably at a very great diflance. Now to have a fixed point 
fomewhere in the heavens, to which the motions of the reft 
may be referred, is certainly of confiderable confequence ia 
Aflronomy ; and both thefe bodies are bright and fmall enough, 
to anfwer that end (/6). 

Datchet fiear Windfor, W. HERSCHEI.. 

January i, 1785. 

{h) Having found two more of thefe curious objefts, I add the place of them 
here, in hopes that thofe who have fixed inllruments may be induced to take an 
early opportunity of obferviug them carefully. 

Feb. I, 1785. A very bright,, planetary nebula, about half a minute in diame- 
ter, but the edges are not very well defined. It is perffdiy round, or peihaps a 
very little elliptical, and all over of an xuiiform brightnt Is : with higher powers 
it becomes proportionally magnified. It follows y Krrdani 16' 16" in time, and 
5S 49' more north than that liar. 

Feb. 7, 1785. A beautiful, very brilliant globe of light; a little hazy on the 
edges, but the hazinefs goes off very fuddenly, fo as not to exceed the 20th part 
of the diameter, which I fuppofe to be from 30 to 40". It is round, or perhaps 
a very little elliptical, and all over of an uniform brightnefs : I fuppofe the intenfity 
of its light to be equal to that of a ilar of the ninth magnitude. It precedes the 
third b (Fl. 6.) Crateris 28' 36'' in time, and is i" 25' more north tlian that flar. 

n:r/. ' fn:':, TY / AAf till ,> itlO. 


' ^'y /■ 

■■*■*■.■.*.:. .*•:?:t^•;>/v.^^\!%*^..*. *. — 

[ ^6? ] 

XIII. Remarks on Jpec'ific Gravities taken at different Degrees of 
Heat, and an eafy Method of reducing them to a common Stan- 
dard. By Richard Kirwan, Efq, F. R. S. 

Read February 17, 1785. 


THAT a comparative view of the weights of equal volumes 
of water and all other fubftaiiccs is highly uleful on 
many occafions, is too well known to require any proof; but 
that a principal ule refaiting from this compariion, when pro- 
perly made, is unattainable by a perulal of the common tables, 
I fhall here endeavour to ihew, and at the fame time point 
out a remedy for this defeft. 

One capital advantage derivable from a table of fpecific gra- 
vities, is the knowledge of the abfolute weight of any lolid 
meafure of the fubftances therein contained, or that of the folid 
meafure of a given weight of thofe fubftances, a cubic foot of 
water being luppofed to weigh 1000 ounces avoirdupois, and 
confequently a cubic inch of water weighing 253,182 grains. 
But the authors who havedifcovered this equation of weight and 
meafure, and all thofe who have fince treated this fubjec^l, have 
neglected to inform us of the temperature at which this agree- 
ment takes place ; yet that it cannot take place in all tempera- 
tures is evident from the experiments of Dr. Halley and 
others, who have found, that from a few degrees above the 
freezing to the boiling point, water is dilated about ^'-^ of its 
bulk; and, confequently, if 1000 ounces at the freezing point 
be equal to one cubic foot, they mud be equal at the boiling 

M m 2 poin 


268 Mr. Kir WAN's Remarks on fpecific Gravities 

point to oiij cubic foot and 66,46 cubic inches. And if the 
dilatations are proportional to the degrees of heat throughout 
the fcale, there mufl be an augmentation of 3,136 cubic inches 
per cubic foot, produced by every 10 degrees of heat. Both 
thefe points remain, therefore, to be determined ; firft, at what 
temperature a cubic foot of water weighs exactly 1000 ounces 
avoirdupois ; and,2dly, whether the dilatations produced by fuc- 
ceffive degrees of heat are proportional to the degrees that pro- 
duce them. This laft point has indeed been handled by others, 
but with different views ; and their determinations are not eafily 
applicable to the prefent queftion. 

To examine this matter experimentally, I ordered a hollow 
tinned iron cone to be made, of four inches diameter in the 
bafe, one-tenth of an inch diameter in the lummit infide, and 
10 inches perpendicular height, Whofe folid contents fliould be 
42,961 cubic inches, but by a flight diminution of the dia- 
meter, and a protuberance ariiing from the foldering, I found 
it to contain, in the temperature of 62°, but 42,731 cubic 
inches, according to the eftimation of 1000 ounces to the 
cubic foot ; and having filled it by immerfion in boihng water, 
and taken it up at different degrees of heat, and weighed it 
when cold, I found its contents as exprefled in the following 
table ; the firft column of which fliews the degrees of heat at 
which it was taken up ; the fecond, the weight of the water 
contained in it ; the third, the diminution of weight occafioned 
by thofe degrees of heat j the fourth, the fum of the diminu- 
tions of weight in the cubic foot, by the preceding degrees of 
heat ; the fifth fhews the weight of a cubic inch of water in 
each of thofe degrees of heat; and the fixth, the augmentation 
of bulk in the cubic foot by every 20° of heat. The horizontal 
lines, marked thus ^j I have added from the experiments of Mr, 

z • BladHj 

at different Degrees of Heat. 269 

Bladh, ill the Memoirs of the Academy of Stockhohn for the 
year 1776, whofe determinations, as far as they reached, agreed 
very nearly with mine. The water I ufed was common water 
well boiled and filtered. The experiments were for the moft 
part three times repeated, and the difference in each trial 
amounted to a very few grains. 







Contents of 


Sum of 

Weight of 



the cone in 


dim. in a 

a cubic 

in cubic 



cubic foot. 



















J 2 133 
































3,' 20 



— — — 

■^ ta«i >»■ 



_ _ _ 





Total increafe of 



_ — — 

bulk from 62° to 





bic inches. 


Dec re a fe 

Total from 36'^ to 







212 = 67,327 cu- 




bic inches. 

Hence wx fee, that a cubic foot of water weighs 4<?5,3 grains 
more at 42° than at 62', and confequently is equal to 1001,109 
avoirdupois ounces, and in the temperature of 82^ it weighs lefs 
than at 62° by 788,5 grains, and therefore is equal to 998,198 
ounces. At the boihng point it wants 16589 grains, or ^y,()iS 
ounces of the weight it poflefles at 62°, and confequently 
weighs but 962,085 ounces, &e. 


2 70 Mr. Kir WAN's Reworks onfpec'ific Gravities 

' In this calcuiatiou I take no account of the difference arlfing 
from the expanfion of the veffel, It being only 0,067 of an 
hich at the boiling point; for, according to Bouguer, iron is 
dilated 0,00055 of its bulk from the freezing to the boiling 
point; confequentlj 42,961 cubic inches gain only 0,067 ^^ '^^ 
inch, augmenting the diameter and perpendicular height of 
this fruftum of a -cone at the boiling point in that proportion. 

ilcnce alio we fee, that the expanfions of water are not pro^ 
portional to the degrees of heat ; for by 20 degrees of heat from 
62'' to 82" a cubic foot of water is dilated only^,! 2 inches, but by 
the next 20 degrees of heat, that is, from 82° to 102°, it is 
expanded ^^'] inches, &c. 

Mr. Bladh found the volume of wat?er at 32° to be equal 
to that at ^'^^(y ; but that this irregular expanfion ceafed at 36-6, 
and, according to Mr. De Luc (who firft difcovered it) at 43°. 

As the expanfion of liquids by equal degrees of heat is much 
greater than that of foiids, it happens, that the fpecific gravi- 
ties of the fame folid taken at different temperatures will be 
different ; and., what appears more extraordinary, the fame folid 
will appear fpecitically heavier in higher than in lower tempera- 
tures ; for the fame volume of water being lighter in higher 
than ill lower temperatures, the folid will lofe lefs of its weight 
in it in the former than in the latter cafe : this mlilake we 
may remedy by infpe6llng the fifth column of the foregoing 
table and the following analogy.: as the weight of a cubic inch 
of water at the temperature of 62° is to the weight of a cubic 
inch of water at n degrees of temperature, fo is the fpecific 
gravity found at n degrees of temperature to that which will 
be found at 62°. 

Thus, if 1000 grains of iron be weighed in water of the 
•temperature of 62°, and it lofes therein i 3,^33 grains, if the 


at diftrent Degrees of IJeat. 271 

fame piece of iron be weighed in water of the temperature of 
75°, it will lofe but 13,313 grains; for the lofies of weight 
will be as the weights of equal volumes of water at thofe tem- 
peratures, which, as we have feen, are as 253, 1 8 to 252,8 ; there- 
fore, its fpecific gravity in water of the temperature of 62° 
•will be 7,49; and in water of the temperature of 75°. 7,51 1 ; 
but we may corredl this by the above analogy, for 
^ 253,8 . 252,18 :: 7,51 I . 7,49. 

By this means we obtain the advantage of difcovering the 
true weight of a cubic foot of any fubftance whole fpecific gra- 
vity is known, which it is now plain cannot be know^n when 
bodies are hydroftatically weighed at any temperature a few 
degrees above or below 62% without fuch redudion, or fub-^ 
trading the quantities in the fourth column. 

This method is equally applicable, and with equal neceffity, 
to other means of finding fpecific gravities, as areometers, the 
comparifon of the weights of equal meafures of liquids, the 
different lofles of weight of the fame folid, when weighed in 
different liquids, &c. In all which cafes the weight of water 
at 62°, or the lofs of weight of a folid in water at 62% (hould 
be found by the above analogy. 

Dr. Hales and fome others have eftimated the weight of a 
cubic inch of water at 254 grains, which is an evident miftake, 
as it is true in no degree of temperature, and produces an error 
of more than three ounces in the cubic foot. 

t 272 ] 

XIV. UkSirical 'Experiments made In order to a/certain the non- 
conduct ing Power of a perfeB Vacuum^ &c. By Mr. Wil- 
liam Morgan ; communicated by the Rev, Richard Price, 
LL.D. F.R,S. 

Read February 24, IJ^S- 

■^HE iion-condu£ling power of a perfect vacuum is a fade 
in eledlricity which has been much controverted among 
philofophers. The experiments made by Mr. Walsh, F.R.S. in 
the double barometer tube clearly demon ftrated the impermeabi- 
lity of the electric I/ght through a vacuum ; nor was it, 1 think, 
precipitate to conclude from them the impermeabihty of the 
eleOincJIuid itfelf. But this conclufion has not been univerfally 
admitted, and the following experiments were made with the 
view of determining its truth or fallacy. When I firfl attended 
to the fubjedl, I was not aware that any other attempts had 
been made beiides thofe of Mr. Walsh ; and though I have 
fuice found myfelf to have been in part anticipated in one of 
my experiments, it may not perhaps be improper to give feme 
account of them, not only as they are an additional teftimony 
in fupport of this fad', but as they led to the obfervation of 
lome phaenomena which appear to be new and interelling. 

A mercurial gage B (fee tab. IX. iig. i.) about 15 inches 
long, carefully and accurately boiled till every particle of air 
was expelled from the iniide, was coated with tin- foil five 
anches down from its fealed end (A), and being inverted into 


Mr. Morgan's Experiments, &c. 273 

'tnercury through a perforation (D) In the brafs cnp (E) which 
■covered the mouth of the cill:ern (H), the whole was cemented 
together, and the air was exhaufted from the infide of the 
cillern through 2. valve (C) in the brafs cap (E) jufl: mentioned, 
w^hich producing a perfect vacuum in the gage (B) afforded aa 
-Inlh-ument pecuharly well adapted for experiments of this 
kind. Things being thus adjufted (a fmall wire (F) having 
been previoully fixed on the intide of the ciftern to form a com- 
munication between the brals cap (E) and the mercury (G) 
into which the gage was inverted) tlie coated end (A) was ap- 
plied to the conductor of an electrical machine, and notvvith- 
ftan ding every effort, neither the Inialieft ray of light, nor the 
flighteft charge, could ever be procured in this exhaufted gage. 
I need not obferve, that if the vacuum on its infide had been a 
conductor of electricity, the latter at leall: muff have taken 
place , for it is well known (and I have myfelf often made the 
experiment) that if a glafs tube be exhaufted by an air-pump, 
and .coated on the outfide, both light and a charge may very 
readily be procured. If the mercury in the gage be imperfectly 
boiled, the experiment will not fucceed ; but the colour of the 
electric light, wdiich, in air rarefied by an exhaufter, is always 
violet or purple, appears in this cafe of a beautiful green, and, 
what is very curious, the degree of the air's rarefaction may be 
nearly determined by this means ; for I have known inftances, 
during the courfe of thefe experiments, where a fmall particle 
of air having found its way into the tube (B), the eleCtric 
light became vjfible, and as ufual of a green colour ; but the 
cliarge being often repeated, the gage has at length crack^^^f ■•' 
its fealed end, and in confequence the external air, by being 
admitted into the infide, has gradually produced a change in 
the eleCtric light from green to blue, from blue to indigo, and 
Vql.. LXXV. N n io 

2*-4 Mr'. Morgan's Experiments to a/certain the 

fo on to violet and purple, tiii the medium has at lafl become fb 
denfe as no longer to be a condu6tor of electricity. I think 
there can be little doubt from the above experiments of the 
non-conduvfting power of a perfefl vacuum ; and this fa61t: is 
flili more ilirongly confirmed by the phenomena which appear 
upon the admiflion of a very minute particle of air into the 
iniide of the gage. In this cafe the whole becomes imme- 
diately luminous upon the flightefl application of electricity, 
and a charge takes place, which continues to grow more and 
more powerful in proportion as frelh air is admitted, till the 
deniity of the condu6ling medium arrives at its maximum, 
which it always does when the colour of the electric' light is 
indigo or violet. Under thefe circumftances the charge may 
be fo far increafed as frequently to break the glafs. In fome 
tubes, which have not been completely boiled, I have obferved, 
that they will not condudt the eledtric fluid when the mercury is 
fallen very low in them, yet upon letting in air into the ciftern 
(H), fo that the mercury fliall rife in the gage (B), the elec- 
tric fluid, which was before latent in the iniide, fhall now be- 
come viiible, and as the mercury continues to rife, and of con- 
fequence the medium is rendered lefs rare, the light fhall grow 
more and more vifible, and the gage Ihall at laft be charged, 
notwithftanding it has not been near an eleilrical machine for 
two or three days. This feems to prove, that there is a limit 
even in the rarefaction of air, which fets bounds to its con- 
ducting power ; or, in other words, that the particles of air may 
be fo far feparated from each other as no longer to be able to 
tranfmit the eleClric fluid ; that if they are brought within a 
certain diflance of each other,their conducing power begins, and 
continually increafes till their approach alfo arrives at its limit, 
when the particles again become fo near as to relifl the pafTage 
4 of 

noU'COfiJutf'ing Fo'ive*' of a perjcct Vacuum^ 275 

Qii the fluid entirely, without employing violence, which is 
the cafe iii common and condenied air, but more particularly 
in the latter. Thefe experiments, however, belong to another 
fubject, and may poflibly be communicated at fome future 

It is furprifing to obferve, how readily nn exhaufled tube is 
charged with elecfhricity. By placing it at ten or twelve inches 
from the condudlor the light may be feen pervading itsin{ide,and 
as ftrong a charge may iometimes be procured as if it Vv'-ere in 
conta6l with the conductor: nor does it iignify how narrovv^the 
bore of the glafs maybe; for even a thermometer tube, having 
the minutefl perforation poffible, will charge with the utmoil: 
facility; and in this experiment the phasnomena are peculiarly 

Let one end of a thermometer tube be fealed hermetically. 
Let the other end be cemented into a brafs cap with a valve, 
or into a brafs cock, fo that it may be fitted to the plate of an 
air-pump. When it is exhaufted, let the fealed end be applied 
to the conductor of an electrical machine, while the other end 
is either held in the hand or connected to the floor. Upon the 
flighteft excitation the ele6tric fluid will accumulate at the fealed 
end, and be difcharged through the infide in the form of a 
fpark, and this accumulation and difcharge may be inceffantly 
repeated till the tube is broken. By this means I have had a 
fpark 42 inches long, and, had I been provided with a proper tube, 
1 do not doubt but that I might have had a fpark of four times 
that length. If, inftead of the fealed end, a bulb be blown at that 
extremity of the tube, the ele6tric light will fill the whole of 
that bulb, and then pafs through the tube in the form of a 
brilliant fpark, as in the foregoing experiment ; but in this cafe 
1 have feldom been able to repeat the trials above three or four 

N n 2 times 

276 Mr. Morgan's Exferimenis to afiertam th^ 

times before the charge has made a fmall perforation in the; 
bulb. If again a thermometer filled with mercury be inverted, 
into a ciftern, and the air exhaufted in the manner I have de- 
fcribed for making the experiment with the gage, a Torricellian, 
vacuum will be produced; and now the electric light in the. 
bulb, asw^ell as the fpark in the tube, will be of a vivid green; 
but the bulb will not bear a frequent repetition of charges be- 
fore it is perforated in like manner as when it has been ex- 
haufted by an. air-pump. It can hardly be neceflary to obferve, 
that in thefe cafes the ele6lric fluid affumes the appearance of a 
fpark*, from the narrownefs of the paflage through which it 
forces its way. If a tube, jj-O inches long, be fixed into a globe 
8 or 9 inches in diameter, and the whole be exhaulled, the eledlric 
fluid, after pafling in the form of a brilliant fpark throughout: 
the length of the tube, will, when it gets into the inlide of the 
globe, expand itfelf in all diredlions, entirely filling it wuth a 
violet and purple light, and exhibiting a ftriking inftance of the 
vafl elafticity of the eledric fluid., 

I cannot conclude this paper without acknowledging my obli- 
gations to the ingenious Mr. Brook, of Norwich, who, by com- 
municating to me his method of boiling mercury, has been the 
chief caufe of my fuccefs in thefe experiments f. I have lately 

learned I 

* By cementing the firing of a guittar into one end oF a thermometer tube, a 
f]}ark may be obtained as well as if the tube had been fealed hermetically. 

t Mr. Brook's method of making mercurial gages is nearly as follows. Let a 
glafs tube L (fee fig. 2.)^ fealed hermetically atone end^ be bent into a right- 
angle within two or three inches of the other end. At the diilance of about an inch 
or lefs from the angle let a bulb (K), of about \ of an inch in diameter, be blown 
ia the curved end, and let the reroainder of this part of the tube be drawn out (I) 

mn-comhcihig Power of a perfeci Vacuum. z^--] 

learned from him, that he has alfo afcertained the non-conc!u6ting 
power of a perfedl vacuum ;: but what fteps he took for that pur- 
pofe I know not. Of his accuracy, however, I am fo well con- 
vinced, that hadlnever made an experiment myfelfj fiiould,upoii 
his teftimony alone, have been equally afllired of the facO:. To 
mofl: of the preceding experiments Dr. Price, Mr. Lane, and 
fome others of my friends, have been eye-witnelles, and I be- 
lieve that they were as thoroughly fatisfied. as myfelf with the 
refults of them. I muft beg leave to obferve to thofe who wiflT 
to repeat them, that the firft experiment requires fome nicety, 
and no inconliderable degree of labour and patience. I have 
boiled many gages for feveral hours together without fuccefs,. 

fo as to be fufficiently long to take hold of, when the mercury is boiling. The 
bulb (K) is defigned as a receptacle for the mercury, to prevent its boiling over,, 
and the bent figure of the tube is adapted for its inverfion into the ciftern ; for by 
breaking off the tube at (M) within |- or | of an inch of the angle, the open 
end of the gage may be held perpendicular to the horizon-when it is dipped into 
the mercury in the ciftem, wiihuut obliging us to bring our finger, or any other 
fubftance, into conta£l with the mercury in the gage,.which never fails to render the 
inftrument imperfeft. It is necelTary to obferve,, that if the tube be fourteeii 
or fifteen inches long, I have never been able to boil it effedually for the experi- 
ments mentioned in this paper in lefs than three or four hours, although Mr. 
Brook feems to prefcribe a m.uch fliorter time for the purpofe ; nor will it even 
then fucceed, xinlefs the greateft attention be paid that no bubbles of air lurk 
behind, which to my own mortification I have frequently found to have been the 
cafe ; but experience has at length taught me to guard pretty well againft this 
difappointment, particularly by taking care that the tube be completely dry before 
the mercury is put into it ; for if this caution be not obferved, the inftrument can 
never be made perfeft. There is, however, one evil which I have not yet been able to 
remedy ; and that is, the introduftion of air into the gage, owing to the unboiled 
mercury in the ciftern ; for when the gage has been a few times exhaufted, the mer- 
cury which originally filled it becomes mixed with that into which it is inverted, and 
ii^confequence the vacimm is rendered lefs and lefs perfect, till at laft the inftru- 
ment is entirely fpoiled. I have juft conftrudled a gage fo as to be able to boil the, 
mercury in the ciilern,. but have not yet afcertained its fuccefs,. 


• 2 ; 8 Mr. l\\ u II G A N ' s Experiments, Sec, 

'<\nd was for fome time difpofed to believe the contrary of what 
I am now convinced to be the truth. Indeed, if we reafon 
fi priori, I think we cannot luppofe a perfect vacuum to be a 
perfect condudor without fuppofing an abfurdity: for if this 
were the caie, either our atmofphere mufl: have long ago been 
deprived of all its ele6tric fluid by being every where lur- 
3'ounded by a boundlefs conductor, or this fluid mufl: pervade 
every part of infinite fpace, and confequently there can be no 
Ihch thing as a perfe6l vacuum in the univerfe. If, on the 
contrary, the truth of the preceding experiments be admitted, 
it will follow, that the conducting power of our atmofphere in- 
creafes only to a certain height, beyond which this power be- 
gins to diminifli, till at lafl: it entirely vaniflies ; but in what 
part of the upper regions of the air thefe limits are placed, I 
will not prefume to determine. It would not, perhaps, have 
been difficult to have applied the refults of fome of thefe ex- 
periments to the explr.nation of meteors, which are probably 
owing to an accumulation of eledtricity. It is not, however, 
my prefent defign to give loofe to my imagination. I am fen- 
fible, that by indulging it too freely, much harm is done to 
real knowledge ; and therefore, that one fa£t in philofophy well 
afcertained is more to be valued than whole volumes of fpecu- 
lative hypothefes. 

Chatham-Place, Feb. 12, 1785. 


ri„/..,r„„„ ;;./j.x.\TU, 1.V278. 


'.>W. 2. 

[ '-19 ] 

XV. 'Experiments cind Ohfervatlons relating to Air and Water, 
By the Rev. Jofeph Prieillej, LL.D. F.R.S, 

Read February 24, 1785. 

EVER fiiice the difcovery of the diminution of refpirable 
air in thofe procelTes which are generally called phlogijiic^ 
it has been a great object with philofophers to find what be- 
comes of the air which difappears in them. Among others, I 
have made and publifhed a variety of experiments with that 
view; but though by this means fome farther progrefs was 
made in the philofophy of air, and confequently our know- 
ledge of the principles, or conflituent parts, of natural fub- 
jftances was extended, I did not by any means fucceed to my 
fatisfadion with refpe£l to the immediate obje£l of my re- 
fearches. Others, however, v^^ere more fuccefsful, and their 
fuccefs has at length enabled me to refume my experiments 
with more advantage ; by which means I have been led both to 
confirm their conclufions, and, by diverfifying the experi- 
ments, to throw confiderable light upon various other chemical 
procefles. The refult of thefe obfervations I fhall lay before 
the Society, with as much brevity and diftindtnefs as I can. 

Li the experiments of which I fhall now give an account, 
I was principally guided by a view to the opinions which have 
lately been advanced by Mr. Cavendish, Mr. Watt, and 
M.Lavoisier. Mr. Cavendish was of opinion, that when 
<?/r is deeompofed, water only is produced; and Mr. Watt 


2?o Dr. Priestley's Experimetits andOhfervatlons 
concluded from fome experiments, of which I gave an account 
to the Society, and ahb from fome obfervations of his own, 
that water confifts of dephlogifticated and inflammable air, 
in which Mr. Cavendish and M. Lavoisier concur with 
him; but Mr. Lavoisier is well known to maintain, that 
there is no fuch tiling as what has been called phiogi/Io?i, affirm- 
ing inflammable air to be nothing elfe but one of the elements 
of condituent parts of water. In the following experiments I 
alfo had a particular view to a conclufion which 1 had drawn 
from thofe experiments, of which an account is given in my 
laft communications to the Royal Society j vi%, that inflam- 
mable air is pure phlogiilon in the form of air, at lead with 
the element of heat ; and that fixed ah* confifls of dephlogifti- 
cated and inflammable air; both which do6lrines had been firft 
advanced by Mr. Kir wan, before I had made the experiments 
which I then thought clearly proved them. 

^uch were the hypothefes to which I had a view when I 
began the following courfe of experiments, which I hope will 
be an admonition to myfelf, as w^U as to others, to adhere as 
jigoroufly as poffible to aSlual obfervations, and to be extremely 
careful not to overlook any circumftance that may poffibly con- 
tribute to any particular refult. I fhall have occafion to notice 
my own miilakes with refpe£l to co?icluJto?is, though all the 
fiiBs were ftri6lly as I have reprefented them. But whilfl phi- 
lofophers are faithful narrators of what they obferve, no perfoii 
can juflly complain of being milled by them; for to reajon 
from the fads with which they are fupplied is no more the 
province of the perfon who discovers them, than of him to 
whom they are difcovered. 

One of the moll: Ample of all phlogiftlc proceflfes is that in 

which metals are ignited in dephlogiflicated air. I therefore 

3 began 


relating to Air and JVater, 28 1 

began with this, with a view to afcertaiii whether any 'water 
is produced when the air is made to dii-ippear in it. Accord- 
ingly, into a glafs veflel containing 7 ounce meafures of pretty- 
pure dephlogifticated air, I introduced a quantity of iron turn- 
ings (which is iron in Imall tliin pieces, exceedingly conve- 
nient for thefe and many other experiments) b.aving previoun>- 
made them, together with the veflel, the air, and the mercury 
by which it was confined, as dry as I poilibly could. Alfo, to 
prevent the air from imbibing any moidure, I received it imme- 
diately in the veflel in which the experiment was made, from 
the procefs of procuring it from red precipitate; fo that it had 
never been in contact with any water. ■ ~- ', t - 

I then fired the iron, by means of a burning lens, and pre- 
fently reduced the 7 ounce meafures of air to .65 ; but I found no 
more water after this procefs than I imagined it had not been 
poflible for me to exclude, as it bore no proportion to the air 
which had difappeared. Examining the refiduum of the air, I 
found one-fifth of it to be fixed air, and when I tried the purity 
of that which remained bv the teff of nitrous ain it did not 
appear that aay phlogifticated air had been produced in the pro- 
cefs : for though it was more impure than I luppofe the air 
with which I began the experiment muft have been, it was not 
more fo than the phlogifticated air of the 7 ounce meafures, 
which had not been affeiled by the procefs, and which mufl: 
have been contained in the refiduum, would neceflfarily make 
it. In this cafe one meafure of this refiduum and two of ni- 
trous air occupied the fpace of .32.- ' 

In another experiment of this kind, ten ounce meafures of 
dephlogiflicated air were reduced to .8, and by wafhing in lime 
water to .38. In another experiment, in which 7I ounce mea- 
fures of dephlogiflicated air were reduced to half an ounce 
Vol, LXXV". O o meafure, 

282 Dr. pKif.sTr,EY*5 Experiments and Obfervations 

ineafure,. of which one-fifth was fixed air, the refiduum was 
quire as pure as the air with which 1 hegan the experiment, ths 
tell with nitrous air, in the proportions above-mentioned^ 
giving. 4 in both caies. To what circumftance the. difference 
mip'ht be ovvino- 1 cannot tell. 

In thefe experiments the fixed .air miifl:, I prefume, have been 
formed by the union of the phiogifton from the iron and tho 
dephlogifticated air in which it was ignited; but the quantitjj 
of it was very imall-in proportion to the air which had difap- 
peared, aiKl at that time Ihad no fufpicion that the iron-, which, 
had been melted, and gathered into round balls, could hav*5 
imbibed it ; a melting heat having been fufhcient, as I had 
imagined,, to expel every thing that was capable of affuming 
the form of air from any fubRance whatever.- I was therefore 
intirely at a lofs about wl:^at raufthave become of the air. 

Seniible, however, that- fuch a quantity of air mufl have- 
been ivrxSihtdhy fomething to muft^have given a very. 
perceivable addition of weighty and feeing^ nothing elfe that 
could have Imbibed it,: it occurred' to me to weigh the calx into 
which the iron had been reduced; and I prefently found, that 
the dephlogiiliicated air had adually been imbibed. by the melted 
iron, in the fiirDe manner as inflammable air^ in., my former 
experiments, had been. imbibed by the melted calces of metals, 
however impofiible fuch an abfbrpxion- might have appeared to 
xnt a priori. In the firfl infl:ance,„ about twelve ounce mea- 
liires of d^phlogiilicated air had difappeared,. and the iron had 
gained -fix grains in weight, Repeating the experiment very 
frequently, I always found, that other quantities of iro;i, 
treated in the fame ma.iiner, gained limilar additions of weighty, 
which \yas always very, nearly that of the air which had dif- 


'^r elating to Air and Water, 283 

This calx of irdn, I then concluded, was by no means what 
.1 had before taken it to be, 'vlz, o. pure calx ox flag ^ but either 
the calx, or the iron itfelf, fltturated with pure air. This cal=- 
ciform fubftance I found, by various experimejits, to be the- 
fame thing with x\\Qfcales that fly from iron when it h made 
red-hot, or the fubftanee into which it -runs in a very intenfe 
heat, in an open fire. 

Concludinp^ from the preceding experiment, that iron, fuffi- 
ciently heated, was capable of faturating itfelf with pure air, 
extrai^ed from the mafs of the atmofphere, I then proceeded to 
melt it with the heat of a burning lens in the open air ; and I 
prefently found, that perfect iron was eafily fufed in this way, 
and continued in this fufion a certain time, exhibiting the ap- 
pearance of bGiling o\' throwing out air, whereas it was on the 
contrary imbibing air; and when it was lliturated the fufion 
ceafed, and the heat of my lens could not make any farther 
impreflion upon it. When this was the cafe, I always found 
that it had gained weight in the proportion of 7! to 24, which 
is very nearly one-third of its original weight. The fame was 
the etfe^l when J melted j/?^^/ in the fame circumflances, and 
alfo ^v^x-'j kind of iron on which the experim.ent could be tried. 
But I haveiome reafon to think, that w^ith agreater degree of 
heat than I could apply, the iron might have been kept in a 
flate of fufion fomev/hat longer, and by that means have im- 
bibed more air, even more than one-third of its original 

There was a peculiar circumftance attending the melting of 
cafi iron with a burning lens, which made it impoffible to afcer* 
tain the addition that was made to its weight, and at the fame 
time afforded an amazing fpe^lacle ; for the moment that any 
quantity of it Vv^as melted, and gathered into a round ball, it begnn 

O o 2 to 

.284 Dr, Prie&tley's Experiments andObfer'vations 
.to dilperfe in a thoufand diredions, exhibiting the appearance of 
. a mofl beautiful fire-work, fome of the particles flying to the 
diftance of half a yard from the place of fufion ; and the whole 
was attended with a confiderabie hifling noife. Some of the 
largeO: pieces which had been' dlfperfed in this manner 1 v/as 
able to collect, and having fubjedled tliem to the heat of the 
lens, they exhibited the ilime appearance as the larger mafs from 
which they had been fcattered. 

When I melted this call: iron in the bottom of a deep giafs 
receiver, in order to colledl all the particles that were difperfed, 
they firmly adhered to the glafs, melting it fuperficially, 
though without making it crack, fo that it was flill impoffible 
to coUeft and weigh the particles. However, I generally 
found that, notwithilanding the copious difperfion, what re- 
mained after the experiment rather exceeded than fell fliort of 
the original weight of the iron. Sometimes a piece of com- 
mon iron, and efpecially fleel, would make a little hifling in 
the fufion, and a particle or two would fly oif ; but this was 
never confiderabie *. 

Having now procured what I thought to be a new calx of 
iron, or a calx faturated with pure air, 1 endeavoured to revive 
it by making it imbibe inflammable air, in the lame manner 
that I had before m.ade iron, and various other metals, by melt^ 
ing them in a velTel containing inftammable air. In this I fuc- 
ceeded ; but in tlie courfe of the experiment a new and very 
unexpefted appearance occurred. 1 took a piece of iron which 
I had faturated with pure air, and putting it into a glafs vefTel 

^ On being informed of the above-mentioned phfetiomcna, Mr. Watt con- 
cluded, that the b:ifis of the dephlogiilicated air united to the phlogifton of the iron, 


and formed luater, which was attracted by, and remained Tq firmly united to the 
,calx of iron, as to rcfirt the efTcffts of heat to fcpnrate them, 


relating to Air iind IVater, 2B5 

containing inflammable air, confined by water, threw upon it 
the focus of the lens, and prefently perceived the inflammable 
air to difappear, and without thinking of any thing efcaping 
from the calx of iron (which had been fubjeded to a greater 
heat before) I imagined that I fhould have found the addition of 
the weight of air in the iron, and the refult might be an i.'on 
, different from the common fort. But I found, to my furprife, 
that the iron, which had exhibited no new appearance in thi^ 
mode of treatment, had loft weight, inftead of gaining any. 
The piece of iron on which I made this firft experiment weighed. 
Ill grains, and 71 ounce meafures of inflammable air had dif- 
appeared while the iron had loft 2| grains. 

Confidering the quantity of inflammable air that had difap- 
peared, "ch. 7^ ounce meafures, and the dephlogifticated air 
which had been expelled from the iron, ^v's. 2! grains, which 
is equal to about 4.1 ounce meafures, I found that they were 
very nearly in the proper proportion to faturate each other, 
when decompofed by the eletflrical fpark, vh. X^no meafures of 
inflammable air to one of dephlogifticated air. I therefore had 
now no doubt but that the two kinds of air. had united, and 
had formed either jlv^ J air or water ; but which it was I could 
not tell, having had water on the receiver in which the experi- 
ment was made, and havino: neo-lecled to examine the ftate ot 
the air that remained, except in a general way, by which I 
found, that it was ftill, to appearance, as inflammable as ever. . 

With a view to determine whether j^'a.W air, or water^ would 
be the produce of this mode of combining inflammable and 
dephlogifticated air, I repeated the experiment in a veflel in 
which the inflammable air was confined by mercury, and both 
the veflel and the mercury had been previoufly made as dry as 
poflible. I had no fooner begun to heat the iron, or x^t\\evjlag, 


dtS Dr. Priestley's Experiments and ObfervaUons 
ill thcTc circumftances, than I perceived the air to diminifh, and 
at the lame time the iiiiide of the veffel to grow very cloudy, 
with particles of dew, that covered almoft the whole of it. 
Thefe particles by degrees gathered into drops, and ran down the 
IkIcs oi: the veflel in all places, except where it was heated by 
tli'^ fu n- beams ; fo that it then appeared to me very evident, 
that -water ^ with or without fixed air, was the produce of the 
inflammable air, and t!ie pure air let loofe from the iron in this 
ijvGxle -of operation,.; though afterwards I was taught by Mr. 
Watt to correct this hypothefis, and to account for this refult 
i^i a different manner. When I had examined the remaining 
air, it was as inflammable as ever, without containing any 
mixture. of fixed air at all. 

When I colleded the water which wms produced in this ex- 
periment by means of a piece of filtering paper, carefully in- 
troduced to abforb it, I found it to be, as nearly as poflible, of 
the fame weight with that which had been loll: by the iron : 
and alio, in every experiment of this kind, in which 1 attended 
to this circumflance, I found that the quantity of inflammable 
air which had difappeared was about double to that of the de- 
phlogifticated air fet loofe from the iron, fuppohng..that weight 
to have been reduced into air. Thus at one .time! made a piece 
of this flagambibe ,5! ounce meafures of inflammable air, while 
it lofl as much as^the weight of about 3 ounce meafure-s of de- 
phlogifticated air, and the water colledted weighed 2 grains. 
Another time a piece of flag lofl: 1.5 grains, .and the water 
produced was 1.7 grains; but per fed accuracy is not to be ex- 
pected. ,1 fliall only mention one more experiment of this 
kind, in which t\ ounce mealures .of inflammable air were 
reduced to .92 ounce meafiire, and the iron had lofl: 2 grains,, 
xqual in weight to 3.3 ounce meafures of dephlogiilicated air. 


relating to Air and Water, 2 S 7 

In all the above-mentioned experiments, the Inriammable air 
was that which is produced. by the folution of iron in acids. 

As before- I had finiilied this courfe of exper.ments I had- 
iatistied myfelf that inflammable air ahvvays contains a portit)ii 
of water, and alfo, that when it has been fome time confinccV 
by water, it imhibes more, fo as to be increafed in its fpecifiO 
gravity by that means, I repeated the experiment with inflam- 
mable air which had not bee:i coniined by water, but which was-. 
received in a veiiel of> dry mercury from the-, veflelin which it 
was generated;, but I prefentiy perceived that- vrater was pro-- 
duccd in this- cafe alio, and .to appearance as copioufly as in the- 
former experiment. Indeed, the quantity of water produced, 
which fo greatly, exceeded the weiglit of all the inflammable 
air, is fufficient to prove that it muft have had fome othen^ 
fource than any conftituent part of; that air^ o-r the whole of ity 
together with the water contained in- it; without taking into-- 
coniideration the correfponding lofs of weight in the iron. 

I m.ufl: here obferve, that the iron, flag- which 1 had treated in^' 
tills manner, and which had thereby loft the weight which ^ 
it had acquired by melting in dephlogifticated air, became ^^r- • 
fe5l iron as at firft, and was then capable of being melted by 
the burning lens again ; fo that the fame piece, of iron wouldi' 
ferve for thefe experiments as long as the operator ihouldchufe. 
It was evident, therefore, .that if the iron had lofl: its phlo- 
gifton in the preceding fuflon, it had acquired it again from the- 
inflammable air which it had abforbed ; and I do not fee how the • 
experiment can be accounted for in any other way, w^iich ne— 
ceflarily implies the reality of phloglfton as a conftituent prin- 
ciple in bodies. This, at leafl, is the mofl natural way ofA 
a,ccounting for the appearanceSc 

5. Having^; 

28 S Dr, Priestley's Experiments and Obfeyvations 

Having had this fuccefs with the calx, or Icales of iroji, I 
tried the calx of copper, or thofe fcales which fly from it whea 
it is made red-hot ; and I found water produced in the inflam- 
mable air in the fame manner as when I ufed the fcales of iron 
in the fiime circumftances. I alfo had the fame refult when I 
Y (tyw^^^ precipitate per fe in inflammable air; but having at that 
time a very weak winter's fun, I could not make the experi- 
ment with fo much advantage as I could have Vv'iflied. 

Iron, I found, acquired this additional weight by melting 
in an earthen retort, as well as in the open air by the fun- 
beams, if it were poffible for it to attra61; air, or whatever elfe 
it is that is the immediate caufe of its additional w^eight. 
Three ounces of common iron filings, expofed to a ftrong heat 
in an earthen retort, gained 1 1 dwts, or 264 grains, and yet 
was very far from having been completely fufed. Having a 
glafs tube communicating with the retort, in order to collect 
any air that the iron filings might give out, I found that when 
they were very hot, the water afcended within the tube ; which 
fliews that the iron was then in a ftate of abforblng, and not 
of giving out any air. 

Seeing fo much water produced in thefe experiments with 
inflammable air, I was particularly led to reflcft on the relation 
which they bore to each other, and efpecially to Mr. Cav^.n- 
dish's ideas on the fubjeil. He had told me that, notwith- 
ftanding the experiments of which I had given an account to 
the Royal Society, and from which I had concluded that in- 
flammable air v/as pure phlogifton, he was perfuaded that ^uDater 
w^as effential to the produdlion of it, and even entered into it 
as a conftituent principle. At that time I did not perceive the 
force of the arguments which he flated to me, efpecially as, in 
the experiments with charcoal, I totally difperfed any quantity 


relating io ^/V and Water, 289 

of it with a burning lens tn vacuo, and thereby filled my 
receiver with nothing but inflammable air. I had no fufpicioli 
that tbe w^et leather on which my receiver ftood could have 
any influence in the cafe, while the piece of charcoal was fub- 
je6t to the intcnfe heat of the lens, and placed feveral inches 
above the leatlier. I had alfo procured inflammable air from 
charcoal in a glazed earthen retort two whole days fucceffively, 
in which it had given inflammable air without Intermlflion. 
Alfo iron filings in a gun-barrel, and a gun-barrel itfelf, had 
always given inflammable air whenever I tried the experiment. 

Thefe circumflances, however, deceived me, and perhaps 
would have deceived any other perfon ; for I did not know, 
and could not have believed, the powerful attradion that char- 
coal, or iron, appear to have for water when they are intenfely 
hot. They will find, and attra£l it, in the mldfl: of the liotteft 
fire, and through any pores that may be left open in a retort ; 
and iron filings are feldom fo dry as not to have moifture 
enough adhering to them, capable of enabling them to give a 
confiderable quantity of inflammable air. But my attention 
being now fully awake to the fubje6t, I prefently found that 
the circumftances above-mentioned had adually mifled me; I 
mean with refpeil to the conclujion which T drew from the expe- 
riments, and not with refpe^t to the experiments themfelves, 
every one of which, I doubt not, will be found to anfwer, 
whenever they are tried by perfons of fufficient Ikill and pro- 
perly attentive to all the circumflances. 

Being thus apprifed of the influence of unperceived moiflure 
in the production of inflammable air, and willing toafcertain it 
ta my perfeift fatisfaClion, I began with filling a gun-barrel with 
iron filings in their common ftate, without taking any parti- 
cular precaution to dry them, and I found that they gave, air as 

Vol. LXXV. P p they 

2<^or T>^» Priestley's Experiments and Obfervations 
they had been ufed to do, and continued to do fo many hours;; 
1 even got ten ounce meafures of inflammable air from, two 
ounces of iron filings in a coatedglafs retort. At length, how- 
ever, the produclion of inflammable air from the gun-barrel- 
ceafed ; but on putting water into it, the air was- produced' 
again, and a few repetitions of the experiment fully fatisfied 
me that I had been too precipitate in concluding that inflam- 
mable air is pure phlogifksn, 

I then repeated the experiment with the charcoal, making 
the receiver, the ftand on which r placed the charcoal, and the- 
charcoal itfelf, as dry and as hot as poffible, and ufing cement 
inftead of a wet leather to exclude the air. In thefe circum- 
ilances I was not able, with the advantage of a good fun, and- 
an excellent burning lens, to decompofe quite fo much as two 
grains of the piece of charcoal, which gave me ten ounce mea- 
fures of inflammable air; and this, I imagine, was eiFe<£led by 
means of fo much moifture as was depofited from the air in its 
flate of rarefa<Sl:ion, and before it could be drawn from the 
jeceiver. To the produ<5lion of this kind of inflammable air I 
vv^as therefore now convinced, that- water is as necefl'ary as to 
that from iron. 

It was rn this flate of my experiments that I' received an au- 
thentic account of thofe of M. Lavoisier, on tranfmitting water 
through an hot iron tube and alfo throug'h a hot copper tube 
containing charcoal, and thereby procuring large quantities of ' 
inflammable air, M. Lavoisier hlmfelf having been fo obliging 
as to fend me a copy of his Memoir on that fubjedl. 1 had 
heard an account of the experiments fome months before; but 
it was fo imperfeft a one, that I own I paid little attention to 
them. At this time, however, I was prepared to be fuiBciently 
f«nfible of their value. 


relalhig to Air dnd Water. -sjpi 

In my lafl: communications to the Royal Society, it will be 
>reen that I had tranfmitted the vapour of feveral fluid fub- 
jflances through red-hot earthen tubes, and thereby prcvured 
different kinds of air. M. Lavoisier adopted the fame pro- 
cefs, but ufed an iron tube ; and by means of that circumftance 
-made a very valuable difcovery which had efcaped me. I had 
indeed on one occalion made ufe of an iron tube, and tranfm^it- 
ted fleam through it ; but not having at that time any view to 
the produtflion of alr^ I did not colleft it at all, contenting 
■myfelf with obferving that water-, after being made red-hot 
was ftill water, there being no change in its fenfible properties. 
Being now farther infi:ru(9:ed by the experiment of M. La- 
voisier, I was determined to repeat the procefs witii all the 
attention I could give to it ; but I fliould not have done this 
with fo much advantage, if I had not had the affiftance of Mr» 
Watt, who alway-s thought that M. Lavoisier's experi- 
ments by no means favoured the conclufion that he drew from 
them. As to myfelf, I was a long time of opinion that his 
■conclufion was juft, and that the inflammable air was really 
furnifhed by the water being decompofed in the procefs. But 
though I continued to be of this opinion for fome time, the 
frequent repetition of the experiments, with the light which 
Mr. Watt's obfervations threw upon them, fatisfied me at 
length that the inflammable air came principally from the char- 
coal, or the iron. 

I fhall firfl relate the refult of the experiment that was made 
with charcoal, and then thofe with iron and other fubftances, in 
conta£l with which (when they were in a flate of fuiion, or at 
leaft red-hot) I made fleam, or the vapour of other liquid fub- 
ilances, to pafs. I fhall only obferve that, previous to this, I 
began to make the experiments with coated glafs tubes, which 

P p 2 I found 

29 2 -^^^ Pbikstley*s Experiments and Obfervat Ions 
I found to anfwer very well during the procefs, though they 
never failed to break in cooling. At length I procured a tube 
of copper^ on which, as M. Lavoisier difcovered, fteam had 
no efFe6l ; and at laft I made ufe of earthen tubes, with which 
Mr. Wedgewoou, that mod generous promoter of fcience, 
liberally fuppHed me for the purpofe ; and thefe glazed on the 
outfideonly I find far preferable to copper. They are, indeed, 
every thing that I could wifli for in experiments of this khid ; 
the reafon of which u'ill appear in my account of another courfe 
of experiments, which I hope to lay before the Society in due, 

Tlie difpofition of the apparatus, with which thefe experi- 
ments were made, was as follows. The water was made to boil 
in a glafs retort, which communicated with the copper or 
earthen tube which contained the charcoal or iron, &c. and 
which, being placed in an horizontal pofition, was furrounded 
with hot coals. The end of this tuhe oppofite to the retort 
communicated with the pipe of a common worm tub, fuch as 
is generally ufed in diftillations, by means of which all the 
fuperfluous fleam was condenfed, and collected in a proper re- 
ceptacle, while the air which had been produced, and had 
come along with it through the worm tub, was tranfmitted 
into a trough of water, where proper veflels were placed to 
receive it, and afcertain the quantity of it; after which I 
could examine the quality of it at leifure. 

In the experiment with charcoal, I found unexpected diffi- 
culties, and confiderable variations in the refult ; the proportion 
between the charcoal and water expended, and alfo between each 
ofthemand the j/V produced, not being fo nearly the fame 
as I imagined they would have been. Alfo the quantity of 
fixed air that was mixed with the inflammable air varied very 
4 much. 

relating to Air and Water. 293 

much. This laft circumftance, however, fome of my experi- 
ments may ferve to explain. Whenever I had no more water 
than was fufficient for the produdlon of the air, there was 
never any fcnfible quantity of uncombined fixed air mixed with 
the inflammable air from charcoal. This was particularly the 
cafe when I produced the air by means of a burning lens in an 
exhaufled receiver, and alfo in an earthen retort with the appli- 
cation of an intenfe heat. I therefore prefume, that when the 
ileam tranfmitted through the hot tube containing the charcoal 
was very copious, the fixed air in the produce was greater than 
it would otherwife have been. The extremes that I have ob* 
ferved in the proportion of the fixed to the inflammable air have 
been from one-twelfth to one-fifth of the whole. As I gene- 
rally produced this air, the latter was the ufual proportion ; and 
this was exclufive of the fixed air that was intimately combined 
with the inflammable air, and which could not be feparated 
from it except by decompofition w^ith dephlogifticated air ; and 
this combined fixed air I fometimes found to be one-third of the 
whole mafs, though at other times not quite fo much. 

To afcertaln this, 1 mixed one meafure of this inflammable 
air from charcoal (after the uncombined fixed air had been fepa- 
rated from it by lime-water) with one meafure of dephlogifti- 
cated air, and then fired them by the ele£lric fpark. After this 
I always found that the air which remained made lime-water 
very turbid, and the proportion in which it was now dimi- 
nifhed, by wafliing in lime-water, fhewed the quantity of 
fixed air that had been combined with the inflammable. That 
the fixed air is not generated in this procefs, is evident from 
there being no fixed air found after the explofion of dephlogifti- 
cated air and inflammable air from iron. 

Not with' 

294 ^^' PiiiESTLEY^s Experiments and Ohfervations 

Notwith Handing the above-mentioned variations, the lofs of 
weight in the charcoal was always much exceeded by the weight 
of the water expended, which was generally more than double 
of the charcoal ; and this water was intimately com.bined with 
the air ; for when I received a portion of it in mercury, no 
water was ever depofited from it. 

The experiment which, upon the whole, gave me the moft 
fatisfaclion, and the particulars of which I fhall therefore re- 
cite, was the following. Expending 94 grains of perfe(5l 
charcoal (by which I mean charcoal made with a very ftrong 
lieat, fo as to expel all fixed air from it) and 240 grains of 
water, I procured 840 ounce meafures of air, one-fifth of 
which was fixed air, and of the inflammable part nearly one- 
third more appeared to be fixed air by decompofition. 

Receiving this kind of air in a variety of experiments, but 
not in the preceding ones in particular (for then I could not 
have afcertained the quantity of it) confiding of fixed and in- 
flammable air together, I found fome variations in its fpecific 
gravity, owing, I imagine, to the ditterent proportions of 
iixed air contained in it ; but upon the whole, I think, that the 
proportion of 14 grains to 40 ounce meafures is pretty near the 
truth, when the proportion of fixed air is about one-fifth of the 
whole. With refpe£l to the weight of the inflammable air after 
the fixed air was feparated from it, I found no great difi^erence, 
and think it may be eftimated at 8 grains to 30 ounce meafures. 

Upon thefe principles, the whole weight of the 840 ounce 
meafures of air will be - 294 grains 

that of the charcoal will be 94 
that of the water - 240 

334 which, confidering the na- 

7 ture 

relating to Air and Water, 295 

ture of the experimenr, will perhaps be thought to be tolerably 
ikear that of the air. 

If the air be analyzed, the 840 ounce meafures will be 
found to contain - 168 of uncombined fixed air = 151 grains. 

and 672 impure imflanamable =179 

fo that the wdiole 840 will weigh - - 330 

Lailily, if the 672 ounce meafures of impure inflammable 
air be decompofed, it will be found to contain 

164 ounce meafures of fixed air= 147.6 grs,. 
and 508 inflammable - - = 30.7 

fo that the whole 672 will weigh - - ^1^'3 

which is very near to 179, the weight of the whole together. 

It may, however, be lafely concluded from this experiment, 
and indeed from- every other that I made with charcoal, that 
there was no more pure inflammable air produced than the 
charcoal itfelf may be very well fappofed to have iupplied. 

There is, therefore, no reafon for deferting the old eftablilhed* 
hypothefis of /'y^/^^^i?^ on account of thefe experiments, fince 
the fa6l is by no means inconfiflent with it. The pure inflam- 
mable air with the water neceflarily contained in it would 
weigh no more than about 30 grains, while the lofs of weight 
in the charcoal was 94 grains. But to this muft be added the 
phlogifton contained in^ 392 ounce meafureS' of fixed air,, 
which, according to Mr. Ki swan's proportion, will be nearly 
6^ grains, and this and the 30 grains will be 95 grains. 

The bafis to this fixed air, as well as to the inflamxmable, 
miifl: have been furnifhed by t\iQ water y and from this it may 
be concluded, that the w^ater muft have been fo far altered as 
to-be changed into fixed air, which will be thought not to be 
any great paradox, if it be confidered. that, according to the 


296 T^r. Priestley's Experiments and Ohfervat ions 
lateft difcoveries, fixed air and water appear to confiil: of the 
fame ingredients, namely dcphiogifLicatcd and inflammable air. 
However, in this change of the water we cannot be abfokitely 
fure that the fame proportion of the ingredients is contained, and 
therefore it cannot be abfolutely determined whether the inflam- 
mable air which it contains enters wholly into the fixed air, or 
not. Farther experiments, or a careful comparifon of thefe ex- 
periments with thofe made by Mr. Kir wan and others, may 
perhaps throw fome light tipon this fubjecl. Whether the com- 
bined fixed air comes wholly from the charcoal, or whether the 
charcoal only fupplies the phlogifton, and the water its bafis, 
that is, the dephlogifticated air, deferves to be inveftigated. 

Before I conclude my account of the experiments with char- 
coal, I would obferve, that there is another in which I place 
fome dependance, in which, with the lofs of 178 grains of 
charcoal, and 528 grains of water, I procured 1410 ounce 
meafures of air, of which the laft portion (for I did not exa- 
mine the reft) contained one-fixth part of uncombined fixed 
air. This was made in an earthen tube glazed on the outfide. 

The experiments with iron were more fatisfa^lory than thof<2 
with charcoal, being fubjedt to lefs variation ; and it is ftill 
more evident from them, that the inflammable air does not 
come from the water, but only from the iron, as the quantity 
of water expended, added to the weight of the air produced, 
was as nearly as could be expe6led in experiments of this kind, . 
found in the addition of weight gained by the iron. And 
though the inflammable air procured in this procefs is between 
one-third and one-half more than can be procured from iron by 
a folution in acids, the reafon may be, that much phlogifton 
is retained In the folutions, and therefore much more may be 
expelled from iron, when pure water, without any acid, takes 
the place of it. I would further obferve, that the produce of 


relating to Air andJValer, 297 

ail', and alfo the addition of weight gained by the iron, are 
much more eailly afcertained in thefe experiments than the 
quantity of water expended in them, on account of the great 
length of the vefTels ufed in the procefs, and the different quan- 
tities that may perhaps be retained in the worm of the tub, 
though I did not fail to ufe all the precautions that I could think 
of to guard againft any variation on thefe accounts. 

Of the many experiments which I made with iron^ I Ihall 
content myfelf with reciting the following refults. With the 
addition of 267 grains to a quantity of iron, and the lofs of 
336 grains of water, I procured 840 ounce meafures of in- 
flammable air ; and with the addition of 140 grains to another 
quantity of iron, and the confumption of 253 grains of water, 
I got 420 ounce meafures of air*. 

The inflammable air produced in this manner is of the 
llghtefl: kind, and free from that very offmfive fmell which is 
generally occafioned by the rapid folution of metals in oil of 
vitriol, and it is extricated in as little time in this way as it is 
poffible to do it by any mode of folution. On this account it 
occurred to me, that it muft be by much the cheapeft method 
that has yet been ufed of filling balloons with the lightefl: inflam- 
mable air. For this purpofe it will be proper to make ufe of 
caft-iron cylinders of a confiderable length, and about three or 
four inches, or perhaps more, in diameter. Though the iron 
tube itfelf will contribute to the production of air, and there- 
fore may become unfit for the purpofe in time ; yet, for any 

* If the perfeft accuracy of the former of thefe experiments may be depended 
on (and it may always be prefumed, that thofe in which litth water is expended 
are preferable to thofe in which more is confumed) the vjater that neceffarily enters 
into this kind of inflammable air is about equal in weight to i\\q phlogiJlon\.\\^X is 
in it. But I propofe to give more particxilar attention to this fubjedl;. 

Vol. LXXV. Q^q thing 

2^S Dr. Priest LLi''s Experiments and ObJervatJons 

thing that I know to the contrary, the fame tube may ferve 
for a very great number of proceffes, and perhaps the change . 
made in the inlide furface may protect it from any farther adiori' 
of the water, if the tube be of fufficient thicknefs ; but this- 
can only be determined by experiment. 

Some eftimate of what may be expeded from this method of 
procuring inflammable air may be formed from the following 
obfervations. About twelve inches in length of a copper tube, 
three-fourths of an inch in- diameter, filled with iron tuniings^ 
(which are more convenient for this purpofe than iron flings^ as 
they do not lie fo. clofe,. but admit the fteam to pafs through 
their interftices-) when it was heated, and a fufficient quantity of 
fleam pafled through it, yielded thirty ounce meafures of air in 
fifty feconds ; and eighteen inches of another copper tube, an 
inch and a quarter in diameter, filled and treated in the fame 
manner, gave two hundred ounce mealures in one minute and 
twenty-five feconds ;. {q> that this lai^ger tube gave air in pro- 
portion to its folid contents compared with the Imaller ; but to 
what extent this might be depended upon I cannot tell. How- 
ever, as the heat penetrates fo readily to fome dlftance, the rate 
of giving air will always be in a greater proportion than that of 
the limple diameter of the tube. 

The following experiment was maxie with a view to afcertain 
the quantity of inflammable air that may be procured in this 
way from any given quantity of iron. Two ounces of iron^ 
or 960 grains, when diflblved in acids,, will yield about 80a 
ounce meafures of air ; but treated in this manner it yielded 
1054 ounce meafures, and then the iron had gained 329 grains 
in weight, which is little fhort of one-third of the weight of 
the iron. 


rciaiing to u'fir and JVc2ter. 299 

Cv)!vrideimg how little this inflammable ah* weighs, viz, the 
V hole 1054 ounce meafures not more than 63 grains, and the 
difficulty of afcertaining the lofs of water to fo fmall a quan- 
tity as this, it is not poffible to determine, from a procefs of 
this kind, how much water enters into the compofition of the 
inflammable air of metals. It would be more eafy to deter- 
mine this circumllance with refpe«£l to the inflammable air of 
charcoal, efpecially by means of the experiment made with a 
burning lens /// vacuo. In this method two grains of charcoal 
gave at a medium thirteen ounce meafures of inflammable air, 
which, in the proportion of 30 ounce meaiures to 8 grains, 
will weigh 3.3 grains; fo that water in the compofition of this 
kind of inflammable air is in the proportion of r .3 to 2, though 
there will be fome difficulty with refpe(5t to the fixed air inti- 
mately combined with this kind of inflammable air. 

Since iron gains the lame addition of weight by m.elting in 
(JUphlogiJlicated air, and alfo by the addition of water when 
red-hot, and becomes, as I have already obferved, in all re- 
fpe^lsthe fame fubftance, it is evident, that this air or water, as 
exifting in the iron, is the very fame thing ; and this can 
hardly be explained but upon the fuppofition that water confifts 
of two kinds of air ; viz, inflammable and dephlogifticated. 
I fliall endeavour to explain thefe procefles in the following 

When iron is melted in dephlogifticated air, we may fuppofe 
that, though part of its phlogifton efcapes, to enter into the 
compofition of the Imall quantity of fixed air which is then 
procured, yet enough remains to form water with the addition 
of dephlogiificated air which it has imbibed, (o that this calx 
of iron conlifts of the intimate union of the pure earth of irofi 
and of water ; and therefore when the fame calx, thus fatu- 

q 3 rated 

^00 Dr. Priestley's Expenments and Obfcr-vations 

rated with water, is expofed to heat In inflammable air, this 
air enters into it, deftroys the attradion between the water and 
the earth, and revives the iron, while the water is expelled in 
its proper form. 

Confequently, in the procefs with y?f^/«, nothing is neceflary 
to be fuppofed but the entrance of the water, and the expul- 
lion of the phlogifton belonging to the iron, no more phlo- 
gifton remaining in it than what the water brought along with 
it, and which is retained as a conflituent part of the water, 
or of the new compound. 

Having procured water from the fcales of iron (which I mufl 
again obferve is, in all refpe<3:s, the fame fubflance with iron 
melted in dephlogiftlcated air, or faturated with fteam by means 
of heat) and havii^g thereby converted it into perfecl iron again, 
I did not entertain a doubt but that I fyiould be able to produce 
the fame effecl by heating it with charcoal in a retort; and I 
had likewife no doubt but I fhould be able to extraft the addi- 
tional weight which the iron had gained (viz. one-third of the 
whole) in water. In the former of thefe conje6lures I was 
right ; but with refpe6t to the latter, I was totally miftaken. 

Having made the fcales of iron, and alfo the powder of 
charcoal very hot, previous to the experiment, fo that I was 
fatisfied that no air could be extracted from either of them fe- 
parately by any degree of heat, and having mixed them toge- 
ther while they were hot, I put them into an earthen retort, 
glazed within and without, which v/as quite impervious to air. 
This I placed in a furnace, in which I could give it a very 
llrong heat ; and conne6led with it proper veffels to condenfe 
and colle^l the water which I expe£led to receive in the courfe 
of the procefs. But, to my great furprife, not one particle 


relating to Air dnd IVatcr, 30 r 

of moijlure came over, but a prodigious quaniity of alr^ and 
the rapidity of its produftion aflonifhcd me ; fo that 1 had no 
doubt but that the weight of the air would have been equal to 
the lofs of weight both in the fcales and in the^ charcoal ; and 
when I examined the air, which I repeatedly did, I found it to 
contain one-tenth of fixed air, and the inflammable air, which 
remained when the fixed air was feparated from it, was of a 
very remarkable kind, being quite as heavy as common air. 
The reafon of this was fufficiently apparent when it was de- 
compofed by means of dephlogiflicated air; for the greateft 
part of it was fixed air. 

The theory of this procefs I imagine to be, that the phlo- 
gifton from the charcoal reviving the iron, the water with 
which it had been faturated, being now fet loofe, affecled the 
hot charcoal as it would have done if it had been applied to it 
in the {oimoi Jham as in the preceding experiments; and there- 
fore the air produced in thefe two different modes have a near 
refemblance to each other, each containing fixed air, both com- 
bined and uncombined, though in different proportions ; and 
in both the cafes I found thefe proportions fubjecl to variations. 
In one procefs with charcoal and fcales of iron, the firfi: pro- 
duce contained one-fifth of uncombined fixed air, the middle 
part one-tenth, and the lafl none at all. But in all thefe cafes 
the proportion of combined fixed air varied very little. 

Why air and not water fhould be produced in this cafe, as 
well as in the preceding, when the iron is equally revived in 
both, I do not pretend perfe(ftly to underftand. There is, in- 
deed, an obvious difference in the circumftances of the two 
experiments ; as in that with charcoal the phlogifton is found 
in a combined flate ; whereas in that of inflammable air, it is 


^02 Dr. Priestley's ExperimcJits and Obfeivatlons 

looi'e, or only united to water ; aiid perhaps future experi- 
ments may difcover the operation of this circumftance. 

There is fome analogy between the experinr-ent of the calx 
of iron imbibing inflammable air, and the iron itfelf imbibing 
dephioglfticated air. In the former cafe water is produced, and 
in the Litter Jixed air. However, this cafe of iron imbibing 
dephlogiflicated air more nearly refembles the cafe of the blood 
in the lungs imbibing the fame kind of air, and in both the 
cafes as dephlogifticated air is imbibed, fixed air is formed. 
This, therefore, feems to be a confirmation of the conclufion 
wliich I drew from my former experiments on blood, viz. that 
it parts with phlogifton in refpi ration. Only 1 would now 
add, that at the fame time that it parts with phlogifton it takes 
in dephloglfticated air, which makes the cafe perfe6tly fimilar 
to that of the experiment with iron, which likewife parts with 
phlogifton to form fixed air, at the fame time that it imbibes 
dephlogifticated air in contact with which it is fufed. 

I propole to referve for a future communication the conti- 
nuation of thefe experiments, containing an account of the ap- 
plication of the fame procefs to other fubftances ; but it may 
not be amifs juft to mention a few of the general refults, and 
thofe which have the neareft connexion with the experiments 
recited above. 

After having tranfmitted fteam in contact with charcoal and 
iron in a copper tube, I propofed to do the fame with other fub- 
ftances containing phlogifton, and I began with bones, which 
were burnt black, and had been fubjected to an intenfe heat, 
covered with fand, in an earthen retort. From three ounces of 
bone thus prepared, and treated as I had done the charcoal, I 
got 8-|0 ounce meaiures of air, with the lofs of 288 grains of 
water. The bones wxre by this means made perfedly white, 
3 and 

rehithig to Air and Water.. ^o j 

and had loft i lo grains of their weight. As the air ceafed to 
come a confiderable time before all the water had been tranf- 
mitted through the tube containing them, I concluded that the 
air was formed from, the phlogifton contained in the bones, and 
fo much water as was necefl'ary to give it the form of air. 

This air differs confiderably trom any other kind of inRam- 
mablc air, being in feveral refpecl:s a medium between that 
from charcoal and that from iron. It contains about one- fourth 
of its bulk of uncombined fixed air, but not quite one-tenth 
intimately combined with the remainder. The water that 
came over was blue, and pretty ftrongly alkaline, which muft. 
have been occafioned by the volatile alkali not having been in- 
tirely expelled from the bones in the former procefs, and its 
having in part diflblved the copper of the tube in which the 
experiment was made. 

I fubjecled to the fame procefs a variety of fubftances thaf 
are fald not to contain phlogiflon, but I was never able to pro- 
ciwe inflammable air by means of them ; which ftrengthens 
the hypothefis of the principal element in the conftitution of 
this air having been derived from thefubfiance fuppofed to con- 
tain phlogifton, and therefore that phlogifton is a real fub- 
flance, capable of aiTuming. the form of air by means of water 
and heat. 

The experiments above-mentioned relating to Iron were made 
with that kind which is inalleahk ; but 1 had the fame refult 
when I made ufe of fmall nails of caji iron, except that thefe 
were firmly faftened together after the experiment, the furfaces 
of them being cryftallized, and the cryftals mdxing with each 
ether, fo that it was with great difficulty that they could be 
got out of the tube after the experiment, and in general the 
fclid parts of the nails were, broken before they were feparated 


304 Dr. Priestlky's Experiments and Ohfervations 

from each otlicr. Indeed the pieces of malleable iron adhered 
together after the experiment, but by no means fo firmly. 

Cafl: iron anneitled (by being kept red-hot in charcoal) is 
remarkably dillerent from the caft iron which has not under- 
gone that operation, efpeclallj in its being, to an extraordinary 
degree, more foluble in acids. With the turnings of annealed 
call iron I made tlie following experiment. From 960 grains of 
this iron, and with the lofs of 480 grains of water, I got 870 
ounce meaiares of inflammable air, and tranfmitting fleam 
through them a lecond time, I got 150 ounce meafures more. 
The iron had then gained 246 grains in weight, and the pieces 
adhered firmly together ; but being thin they were eafily broken 
and got out of the tube, whereas it had required a long time, 
and a (liarp fteel inftrument, to clear the tube of the caft-iron 

Having got water from the fcales of iron and of copper fatu- 
rated with dephlogift Icated air, by heating them in inflammable 
air, it occurred to me to make the fame experiment with prcdi- 
pitate 'per fe^ and I found, that the moment that the focus of 
the lens fell upon this fubflance the mercury began to revive, 
the inflammable air rapidly difappeared, and water was formed 
on the fides of the veffel in which the experiment was made. For 
want of a better fun, I could not afcertain every circumfiiance 
relating to this procefs ; but what I did feemed to afford a 
fufficient proof that mercury contains phlogifton, and that it is 
not revived by the mere expulfion of dephlogifticated air, as 
M. Lavoisier fuppofes ; efpecially as ?w^.vW ^/r was found in 
what remained of the inflammable air. In one of thefe expe- 
riments 4.5 ounce meafures of inflammable air had difappeared, 
and 1.6 ounce meafure remained ; and this appeared to contain 
fome dephlogiflicated air' mixed with the inflammable. 

4 Willing 

relating to Air and Water* 305 

Willing to try the efFeft of heating iron, and other fub- 
flances, in all the different kinds of air, without any particular 
expe£lation, I found that iron melted more readily in vitriolic 
CiCid air than in dephlogifticated air, the air was diminiflied as> 
rapidly, and the infide of the veffel was covered with a black 
footy matter, which, when expofed to heat, readily fublimed in 
the form of a white vapour, and left the glafs quite clean. 
The iron, after the experiment, was quite brittle, and 
mufl, I prefume, be the fame thing with iron that is fid- 
phurared; but I did not particularly examine it. Of feven 
ounce meafures of vitriolic acid air, in one of thefe experi- 
ments, not more than three-tenths of an ounce meafure re- 
mained ; of this two-thirds was fixed air, and the refiduum 
of this was inflammable. I had put three of fuch refiduums 
together, in order to make the experiment with the greater 

Having tranfmitted ^^<3W, or the vapour of water, througlr 
a copper tube, I was willing to try the effects oi fpirit of wine 
through the fame tube when red-hot, having before procured 
inflammable air by fending the fime vapour through a red-hot" 
tobacco-pipe^ In this cafe, the vapour of the fpirit of wine- 
had no fooner entered the hot copper tube, than I was perfedly 
sftoniflied at the rapid produ6llon of air. It refembled the 
blowing of a pair of bellows. But I had not ufed four ounces-" 
of the fpirit of wine before I very unexpectedly found, that 
the tube was perforated in feveral places; and'prefently after- 
wards it was fo far deftroyed, that in attempting to remove itr 
from the fire it aftually fell in pieces. The inlide was full of a 
black footy matter refembling lamp-black. 

Upon this. I had recourfe to earthen tubes ^ and found, that by 
melting coppfe'r and other metals in them, and tranfmitting the 

Vol, LXXV* R x vapour 


3-06 Dr. Priest ley's Experiments and Ohfct^callons 

vapour of f^urit of wine in contact with them, differeiiffub- 
fiances were formed according to the metals employed. Thfe 
new lubllances hereby formed may he fa id to be the feveral 
metals lb per- latu rated with phlogifton, and may perhaps not 
be improperly called the charcoal of met ah. 

That this appellation is not very improper, may appear froiii 
thefelubftances yielding inflammable air very copioufiy when 
thev are made red-hot, and the fleam of water is tranfmitted 
in contact w^ith them, jiift as when the charcoal of w^ood is 
treated in the fame manner. The detail of thefe experiments 
1 referve for another communication, as alfo thofe of the con- 
verfion of (pirit of wme, tether, and o//, into different kinds of 
inflammable air, by tranfmitting them, in vapour, through 
hot earthen tubes. In the mean time, I Ihall think myfelf 
happy if the communication of the preceding experiments (hall 
give any fatisfadion to the Members of the Society. 

P O S T S C R I P T. 

BEFORE I clofe' this paper, I wifli to make a few general 
infer ences froiti the principal of the experiments above-men- 
tioned, efpecially relating to the proportional quantity of phlo- 
gifton contained in /><?« and wafer. 

When any quantify of iron is melted in idephlogifticated air, 
it imbibes the greatefl part of it, and gains an addition of 
weight very nearly eqilal to that of the air imbibed. Thus the 
abforption. of twelve ounce meafures of dephlogifticated air 

2 gave 

relating to Air and Water, ^oy 

gave an addition of fix grains to the piece of iron which had 
been melted in it. But there was always a quantity of fixed 
air produced in this procefs ; and on the fuppofition that this 
air confifts of the union of dephlogifticated and inflammable 
air, it proves that the dephlogifticated air which enters the 
iron expels more phlogifton than is neceflary to conftitute an 
cqnal weight of water, fo ih^t water does not contain fo much 
phlogiflon as iron ; but the difference is not very confiderable. 

Admitting Mr. Kirwan's conclufion, viz. that loo cubic 
inches of fixed air contain 8, 35 7 grains of phlogifton, the. 1 3 ounce 
meafure of fixed air, which (in an experiment recited in thefe 
papers) was found in the refiduum of feven ounce meafures of 
dephlogifticated air abforbed by iron, would not have contanied 
more than .oi grain of phlogifton, or about .16 ounce mea- 
fure of inflammable air. Then, as the abforption of 12 
ounce meafures of d^phlogifticated air occafioned an addition of 
6 grains to the weight of the iron which had abforbed it, the 
abforption of feven ounce meafures mufl have occafioned the 
addition of 3.5 grains to the iron which had imbibed it. But 
the fame addition of weight to iron given hjj^eam (which car- 
ries its own inflammable air along wdth it) would have expelled 
near 12 ounca meafures of inflammable air: confequently, 
about ten ounce meafures of inflammable air (or the phlogiuon 
requifite to form it) muft, in the former experiment, have been 
retained in the iron> in order to compofe the water which was 
now made by the union of the dephlogifticated air imbibed by 
the iron and the phlogifton contained in it : and therefore the 
proportion between the quantity of phlogifton in won to that 
which is contained in an equal weight of w^ater, may be about 
12 to 10, or more accurately to 10.4. 

Had no fixed air at all been found in the refiduum above- 
nientlGned, it might have been concluded, that water had cori- 

R r 2. tained 

308 Dr. Priestley's Experiments and Obfervatkns 
tained the very fame proportion of phlogiflon with iron. Since 
when iron that has been faturated with dephlogifticated air is 
heated in inflammable air (in which procefs an equal weight of 
water is produced, and the lofs of weight in the iron is equal to 
that of fuch a quantity of dephlogifticated air as would have 
been one- h^] if of the bulk of the inflammable air which difap- 
pears in that procefs) it might have been concluded, that one- 
fifth of any quantity in water had been inflammable air. 

For, neglecting the difference between the weight of dephlo- 
gifticat-ed and common air, which is not confiderable, and efci- 
mating the latter -^-s^-^-th part of water, and inflammable air at 
one-tenth of the weight of common air, an ounce meafure of 
dephlogiilicated air will weigh ,6 grain, and two ounce mea* 
fures of inflammable air will weigh .12 grain, which num- 
bers are to each other as 5 to i *. 

Though, in confequence of the fmall quantity of fixed air 
Avhich is found in the procefs of melting iron in dephlogifli- 
•cated air, this conclufion is not accurate, it is pretty nearly 
fo ; and it is remarkable that, upon tliis fuppofition, about as 
;nuch inflamxmable air is expelled from iron when water is com- 

* It appears from the prolccHtion of thefe experiments, that the water which 
is found on Jieating tfee leaks of iron m inflammable air, is not formed by the 
dephlogifticated air expelled from rhera uniting with the inilammable air in the 
veiTel, but was the water previonfl.y contained in the fcales^ which is made to quic 
its place by the introdutlion of the phlogiflon from the inflammable air; yet that 
water carries out with it not much lefs phlogifton than was taken in by the iron, 
3nd a little more mml be allowed for that water which was neCefTary to make 
inflammable air, and which could not enter the iron when it was revived ; fo thar^ 
on the whole, the phlogifton in the water that is found after the procefs muft be 
very inearly the fame quantity that is imbibed by the iron, and the water is nearly 
the fame that would have been produced, on the fuppofition of its being made 
from dephlogifticated air exp'jiled from the fcales uniting with the inflammable 
air in the vcflel. 

relating to Air and Water* ' 509 

binecl with It, as the water itfelf brings along with it, as an 
eiTential ingredient in its compofition. For in one experiment 
296 grains added to the weight of a quantity of iron by fteam, 
made it to yield about 1000 ounce meafures of inflammable air. 
This would weigh 60 grains, and one- fifth of the 296 grains 
of water will be 59.2 grains. Again, 267 grains added to iron 
by fteam made it to yield 840 ounce meafures of inflammable 
air, which would weigh 50.4 grains, and one-fifth of the 267 
would be 53.4 grains. 

When the experiments on the melting of iron in dephlo- 
gifticated air Ihall be repeated on a larger fcale, which it will 
not be difficult to do by the help of a larger burning lens than 
I am at prefent pofleffed of, it will be eafy to reduce thefe cal- 
culations to a greater certainty. All that I can do at prefent Is 
to approximate to fuch general conclufionsas I have mentioned ; 
■but they are of fo much confequence in philolbphy, that It 
will certainly be well worth while to afcertain them with as 
much accuracy as poflible. Nice calculations would be ill be- 
^owed on the imperfedh data which I am as yet able to furnifh. 
Attention muft alfo be given to the quantity of water contained 
in inflammable air from iron ; which not being yet afcertalned 
is not confidered in thefe inferences. I wifli only to hint in 
this Poftfcript, that fome important conclufions feems to be 
•nearly within our reach. 

XNfi OF ^ARt 1. OF VX)U LXtV* 


ycs^^e. Line, 

289. I'J- dele ihe whoh Ihe except ~-^ X p. Whence, 


32. 2b. for 2 •OOOOOOOOOI, ^read 2 — '0000000001, 
34. 8. /ar to tangent, read to cotangent. 


78. 2. for unequal, read unequal ; 

•94. 25. /^r 20' 39'" read 20" 39'" 

12Q. lO. Jor Fl. 74, r^«^ Fl. 74. 

170. »0. /?r 16-r^ read 16^1 

200. 15. yiiy in. read 3. 

270. 14. for 36°6 r^a^ 36°,6