Nn =e RON EMT eee dn Fe hh thee Vm ae tke Poet Bm a i Ry a RRs Fie in i RO Re = Fy tire Ha alee Aa ths Glee ee cig O01 OW snk ts alate nit Werks Faso: Feehan Bp Ponitnti >) victim te eth cipal aie Ah eta WV Ain it oh Wana teh Nigh = Fon hn Hatter BM chim be tse“ an = font ve MeSntyli-%e Aceren we eet, ae SNe We rth Feng pivestiasaouen sa ae Gn a ety ha enti hip Ge we a DR Re Tit VN 0b NA de bn Te ln AY: Mes Ae © Bre obs th R- Valea find) tl ce | iiegibodianam aero ee Rie te The» ant ~ rai < - . . , . - ~ c - M of . ae ; : Sih i the Wi are eg AP eh = her a taht Hi te thm H to ip he lc b> em eg bh ~ Rag Hn fe eee Rat a e Rhatert h aw ad eh Nh Deh THE ton Be in Gein in fay pH A LAE Hen te Dig rll ar Molc a par ee-Ver = Sie ote the = mullite Dae © ib este Ube ye Re td tym mcbe os Sim Oot Pgs — te ta ih wh: tae: etal 5 Wm at few On Raat As ripe oa Hint et FSD n he he Belin ha -Gell goo testi he Ds oe TB AES am im A gt 5 Ee Te Ee i= Chased SiG ini NM eee hie | ovo iim hela bay agaden oi = Nhe We Ye Ra Rndie Mite ty Be ce C—O Cd he Vote ae BAe -
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It is interesting to note that the length of the period of variability,
reckoning from maximum to maximum, began after March 27 to
increase from three days to four days.
The two following maxima, after that of April 8, occurred on the
13th and 18th, so that the period became still more lengthened, namely,
to about jive days. Further observations up to May 5 seem to
indicate that the five-day period is shortening.
Another interesting observed fact was that the light of the Nova
at the minimum on the 25th was more intense than at the preceding
minimum on the 21st, the estimated difference of magnitude at these
times being about 4-tenths of a magnitude. Unfortunately the
increasing twilight and the unfavourable position of the Nova make
it very difficult now to determine the magnitudes correctly.
The two plates accompanying this paper illustrate epee the
various fluctuations of the light of the Nova from February 22, when
it had not quite attained its maximum brilliancy, to May 5.
The curve is drawn to satisfy as far as possible all the observations
made at Kensington. The dotted portions represent the possible light-
curve for those times when no estimates for magnitude could be
secured.
In the plates the abscisse represent the time element and the
ordinates that of magnitude.
401
Further Observations on Nova Perset.
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402 Sir Norman Lockyer.
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Prefers
Colour.
In the first part of the period covered by the later observations, the
colour of the Nova has been generally described as yellowish-red, red
with a yellow tinge, and yellow with a reddish tinge. Since April 25
the colour has been perhaps more red than formerly, and sometimes
noted as very red.
It is interesting to remark that the colour varies periodically with
the change in magnitude. At maximum it is of a distinct yellowish-
red hue, but at or near minimum the yellowish tinge disappears and
the Nova appears very red.
Further Observations on Nova Perset. 403
The Visual Spectrum.
In the continued observations the C and F lines of hydrogen have
always been recorded as “ conspicuous,” other prominent lines being
near A447, 465, and 501 (the last named being sometimes as
bright as F or even brighter), and a line in the yellow which recent,
measures show to be Ds.
The strong lines in the green at 4X 4924, 5019, 5169, and 5317,
which occurred in the earlier photographs, and which were ascribed to
iron, are either absent from the later photographs or appear only as
very weak lines.
It has been noted that the lines 447, 501, and Ds appear to vary
with the magnitude of the star, becoming relatively more prominent
towards a minimum.
The continuous spectrum has been described throughout as “ weak”
or ‘very weak.”
On the evening of April 25, Messrs. Fowler and Butler made
comparisons of the Nova spectrum with the spectra of hydrogen,
helium, and that furnished by an air spark between poles of iron and
zinc. For this purpose a Hilger two-prism star spectroscope was
used with the 10-inch refractor. The hydrogen line F and the helium
line Dz were found to be sensibly coincident with Nova lines. @,The
middle of the strong green line, previously mentioned as 501,
practically coincided with the nitrogen line 5005-7, and therefore
there is little doubt that it is identical with the chief nebular line.
X5007°6. This line was also compared with the asterium line at.
X5015°7, but was found to be decidedly non-coincident with it,
though of sufficient breadth to nearly reach it.
Photographie Spectrum.
In so far as the number and positions of the lines are concerned,
the few photographs available for discussion were obtained in the.
early part of the period dealt with in the present paper (March 26 to
May 7), and show a spectrum very similar to that of March 25, which
was described in detail in the last paper. The chief lines shown in
the photographs are Hf, Hy, Hé, He, and HE, together with 4471
and 4650.
Characteristics of HP.
In continuation of the series of light curves of Hf reproduced in
the last paper, I give those plotted by Mr. Baxandall from the later
photographs.
It will be seen that the line Hf still shows two maxima of intensity.
As recorded in the previous paper, the less refrangible component gave.
404 Total Eclupse of the Sun, May 28, 1900.
MAR. 267"
APR, 137
99 TH
LIGHT CURVE of H,
(30-inch reflector).
indications of becoming brighter than the more refrangible member.
These further photographs indicate that by April 4 the less refrangible
had become twice as intense.
“Total Eclipse of the Sun, May 28, 1900.—Account of the
Observations made by the Solar Physics Observatory Eclipse
Expedition and the Officers and Men of H.MLS. ‘ Theseus’ at
Santa Pola, Spain.” By Sir Norman Lockyer, K.C.B., F.B.S.,
Received May 21,—Read June 20, 1901.
(Abstract.)
The Report gives details as to the erection of coronagraphs,
prismatic cameras, and other instruments, and of the results obtained
by their use during the eclipse, which was observed under very favour-
able circumstances. Some of the more obvious results have already
been stated in a Preliminary Report,* and the following remarks may
now be added. :
A comparison of the photographs taken with the coronagraph of
16 feet focus with those taken about two hours earlier in America
indicates that while some of the prominences changed greatly in
appearance in the interval, no changes were detected in the details of
the corona.
The spectrum of the chromosphere, as photographed with the
prismatic cameras, so greatly resembles that of 1898 that it has. not
been considered necessary to make a complete reduction of wave-
* “Roy. Soc. Proc.,’ vol. 67, p. 341.
On the Prothalli of Ophioglossum pendulum (L.), de. 405
lengths. The prominences visible during totality had comparatively
simple spectra, the greatest number of lines recorded being 36.
The heights above the photosphere to which many of the vapours
can be traced in the photographs are tabulated and compared with
the results obtained in 1898; the two sets of figures are sufficiently
accordant, except in the case of the shorter arcs, the value 475 miles
derived for the lowest measurable vapours in 1898 being represented
in 1900 by two strata, one reaching to 700 miles and the other to 270
miles above the photosphere.
The bright-line spectrum of the corona was decidedly less bright
than in 1898, and a much smaller number of rings is seen in the
photographs. ‘The three brightest rings are at wave-lengths 5303-7,
4231°3, and 3987-0, and it may be noted that these were also the
brightest in the eclipses of 1893, 1896, and 1898. The conclusion
that the different rigs do not originate in the same gas, arrived at
from a discussion of the photographs of 1898, has been confirmed.
A drawing is given to illustrate the fact that while the details of the
green coronal ring are seen in the inner corona, they have no apparent
relation to the positions of the great streamers or prominences. For
an investigation of this nature the photographs taken with the pris-
matic camera of 20 feet focal length are specially valuable.
“Preliminary Statement on the Prothalli of Ophioglossum pen-
dulwm (1.), Helminthostachys zeylanica (Hook), and Psilotwm,
sp.” By Wiui1am H. Lane, M.B., D.Se., Lecturer in Botany,
Queen Margaret College, University of Glasgow. Communi-
cated by Professor F. O. Bower, Sc.D., F.R.S. Received
May 20,—Read May 23, 1901.
During a recent visit to Ceylon and the Malay Peninsula* the
author found prothalli of Ophioglossum pendulum and Helminthostachys
zeylanica, as well as a single specimen, which there is reason to regard
as the prothallus of Psilotum. As the examination of the material will
occupy a considerable time, it has seemed advisable to give a brief
description of the mode of occurrence and external morphology of the
prothallus in these three plants, without entering into details of struc-
ture or discussing the phylogenetic bearing of the facts.
The chief gaps in our present knowledge of the gametophytes of the
more isolated living Pterzdophyta concern the Ophioglossacee and Lyco-
podiacee, to which groups the prothalli described below belong. The
* The expenses of the visit to the Malay Peninsula were defrayed by a grant
from the Royal Society.
406 Mr. W. H. Lang. On the Prothalli of
prothallus of Ophioglossum pedunculosum* was described by Mettenius in
1856. It was subterranean, consisting of a small tuber, from which an
erect cylindrical body proceeded. On the latter, which in some
instances was observed to reach the surface and turn green, the sexual
organs were borne. The first divisions in the germinating spore of
O. pendulumt are described and figured by Campbell. The prothalli
of two species of Botrychiuwm are known, both of which are subterranean.
That of B. virginianum t is thick’and flattened, and in its structure and
in the localisation of the sexual organs on the upper surface clearly
dorsiventral. The prothalli of 6. Lunaria,§ however, have sexual
organs on all sides. In the Lycopodiacee the prothallus is well known
in the heterosporous forms and in Lycopodium. 'The sexual generation
is entirely unknown in the Ps¢lotacew and in Phylloglossum. If the
author is correct in attributing the prothallus to be described below to
Psilotum, the only two isolated genera of existing Vascular Cryptogams
in which the gametophyte is entirely unknown are Tmesipteris and
Phylloglossum.
Hie. 1. Fie. 2. Fie. 3.
Fig. 1. Ophioglossum pendulum, old prothallus from above. (x 7.)
Fig. 2. Helminthostachys zeylanica, prothallus, bearing antheridia, from the
eside. (x 7.)
Fig. 3. Psilotum, sp., prothallus from the side and slightly from above. (x 7.)
Ophioglossum pendulum.
The sporophyte of this plant was, for the most part, found growing
on the humus collected by such epiphytic ferns as Polypodwm querer-
folium and Asplenium nidus. A large mass of the former, with the
Ophioglossum growing upon it, was collected in the Barrawa Forest
* ¢Filices Horti Bot. Lipsiensis,’ Leipzig, 1856, p. 119.
+ ©Mosses and Ferns,’ London, 1895, p. 224.
+ Jeffrey, ‘Trans. Canadian Institute,’ 1896-7, p. 269.
§ Hofmeister, ‘Higher Cryptogamia,’ London, 1862, p. 307.
Ophioglossum pendulum (Z.), dc. 407
Reserve,* near to Hanwella, in Ceylon. On the humus contained in
this being carefully examined prothalli of various ages were found.
They were distributed throughout the humus, the majority being found
near the bottom of this, éiten embedded among the ramenta which
clothe the rhizome.
The very young prothalli are button-shaped, the slightly conical
lower part expanding above. The basal region is brownish, the surface
of the upper portion a uniform dull white. The latter tint is due to
the close covering of paraphyses, which, at this age, extends unin-
terruptedly from just above the base over the whole surface of the
prothallus. The youngest prothalli are thus clearly radially sym-
metrical. In slightly older prothalli, seen from above, the circular
outline is lost, owing to the more active growth of two or three points
on the margin. This continues, and there thus arise a corresponding
number of cylindrical branches, the prothallus becoming irregularly
star-shaped. At first the branches spread out in a horizontal plane,
though with a slight upward tendency. But when the branches them-
selves subdivide all suggestion of this secondary dorsiventrality is lost,
and the larger prothalli consist of branches radiating in all directions
into the humus (fig. 1).
From a short distance behind the smooth, bluntly conical apex the
surface of the branch is covered with short, wide, unicellular paraphyses
analogous to those known in prothalli of Lycopodiwm Phlegmaria. These
are only absent above the sexual organs.
The prothalli are moneecious, antheridia and archegonia being found
close together on the same branch. The surface projects very slightly
above the large sunken antheridium; the neck of the archegonium,
which, as seen from above, is sounosel of four rows of cells, hardly
projects from the prothallus. The sexual organs thus resemble those
of O. pedunculosum, as described by Mettenius.
-Rhizoids have not been seen on any of the numerous prothalli ex-
amined. An endophytic fungus occupies a middle zone of tissue in all
the branches, the superficial layers and a central core of cells being
‘Tree from it.
Helminthostachys zeylanica.
The prothalli of this plant were also found in the Barrawa Forest
‘Reserve, a low-lying jungle subject to frequent floods. Young plants
still attached to the prothallus were fairly abundant in certain spots,
and, by searching in the rotting leaf mould around, prothalli of various
ages were obtained. The prothalli were found at a depth of about
2 inches.
* Iam indebted to my friend Mr. F. Lewis, who guided me to this locality, for
the assistance he afforded me in my search for the prothallus of Ophioglossum and
Helminthostachys.
VOL. LXVIII. 2F
408 Mr. W. H. Lang. On the Prothalli of
The youngest prothallus obtained was a short cylindrical body a little
over one-sixteenth of an inch in length. The lower end was darker in
tint and bore a number of short rhizoids, while above this, where the
antheridia were situated, the surface was of a lighter colour. The
apex itself was bluntly conical and almost white. In slightly larger
prothalli the contrast between these two regions was more strongly
marked. The lower, vegetative region increases in size and becomes
lobed, while the antheridia are confined to the cylindrical upper
portion, which continues to increase in length. This latter region
appears to be longer and the lobed basal part relatively less developed
in prothalli which bear the antheridia (fig. 2). Seven of the young
prothalli found were male; the other two bore archegonia only.
These female prothalli were stouter and more lobed than the male
ones, and the diameter of the short apical region, on the surface of
which the archegonia were situated, was almost the same as that of
the vegetative region. There thus appears to be a partial sexual
differentiation in the prothalli of Helminthostachys, but both antheridia
and archegonia may occur on the same prothallus, as some of the latter
attached to young plants have shown. The antheridia are large and
often closely crowded together. They hardly project from the
surface, the wall being only slightly convex. The archegonial neck,
which is formed of four rows of cells, projects distinctly from the
prothallus.
The distinction made above between a vegetative and a reproductive
region in this prothallus is supported by the distribution of the
endophytic fungus. This is entirely absent from the reproductive
region, but in the basal part occupies a wide zone between the two
or three superficial layers of cells and the central tissue, which are free
from the fungus.
The young plants attain a considerable size while still attached to
the prothallus. Plants with three leaves and as many roots have
been seen, the prothallus of which showed no sign of decay. The
first leaf is ternate and has a leaf-stalk of variable length. The
lamina is green and reaches the light. A single root corresponds to
each of the early leaves.
Examination of the prothalli connected with young plants indicates
the position they occupied in the soil. Most commonly the long axis
of the prothallus was vertical ; sometimes, however, it was oblique,
and occasionally horizontal.
Psilotum, sp.
The prothallus of this plant was looked for without success in
Ceylon, both in the mountain region and on the roots at the base of
Cocos palms near the coast. In the localities visited on the west coast
of the Malay Peninsula Psilotum was not abundant. On Maxvwell’s
=
Ophioglossum pendulum (Z.), ke. 409
Hill, in Perak, I found it scantily on stems of tree-ferns, the rhizome
growing among the roots of the fern, which cover the stem. No
young plants were found ; but a single prothallus, embedded among the
roots of the fern in close proximity to a plant of Psilotwm, was
obtained. This prothallus, as will be evident from fig. 3 and the
description below, could only belong to Psilotwm, or be that of some
species of Lycopodium, the gametophyte of which has not been de-
seribed. From the position in which it was found, the former suppo-
sition is the more probable one, but such evidence of association is of
course not conclusive, and the specimen can only be described as the
prothallus of Psilotum with the reservation expressed above.
The prothallus when fresh measured about one-quarter of an inch in
length by about three-sixteenths of an inch at the widest part, which,
as fig. 3 shows, is above. The lower portion is cylindrical and rounded
below. To one side near the lower end is a well-marked conical pro-
jection directed obliquely downwards, which clearly corresponds to
the primary tubercle of the prothallus of Lycopodium cernuum. The
surface of the lower three-fourths of the prothallus was brown and
bore rhizoids. The latter were absent from the upper part, which
widens out suddenly, the increase in width being due to the projection 4 a
of the thick, coarsely lobed margin of the summit of the prothallus.
The central region of the summit is smooth and somewhat depressed.
The upper portion of the prothallus had a faint green tint when fresh,
but no chlorophyll grains could be detected.
In the tissue of the overhanging margin the numerous sunken
antheridia occur, closely crowded together. Archegonia have not been
observed on external examination.
Tn its form this prothallus evidently presents resemblances to pro-
thalli of Lycopodium. In the lower part it resembles the prothalli of
the Lycopodium cernuum type, while the appearance of the upper
portion suggests a comparison with prothalli of Z. clavatum or L. anno-
tnum. ‘There seems no reason to doubt that the meristem will be
found at the junction of the upper and lower regions.
Probably this prothallus was completely embedded among the roots
of the fern. As some of the roots-had been removed before the
prothallus was noticed, this point was not definitely settled ; but the
general appearance of the upper portion, and the absence of assimi-
lating lobes, makes it probable that the upper surface was not exposed
to the light.
That the facts stated above bear on the relationship of the plants to
which these prothalli belong will be obvious from the brief description
given. ‘The discussion of this will, however, be best deferred until the
full account, which is in course of preparation, is completed.
MO, soe V tit. 2G
410 Mrs. H. Ayrton.
“The Mechanism of the Electric Arc.” By (Mrs.) HerrHa
AyRTON. - Communicated by Professor PrRRy, F.R.S.
Received June 5,—Read June 20, 1901. |
(Abstract.)
The object of the paper is to show that, by applying the ordinary
laws of resistance, of heating and cooling, and of burning to the are,
considered as a gap in a circuit furnishing its own conductor by the
volatilisation of its own material, all its principal phenomena can be
accounted for, without the aid of a large back E.M.F., or of a “ negative
resistance,” or of any other unusual attribute.
The Apparent Large Back E.M.F.
It is shown how volatilisation may begin, even without the self-
induction to which the starting of an arc, when a circuit is broken, is
usually attributed ; and it is pointed out that, when the carbons are
once separated, all the material in the gap cannot retain its high
temperature. ‘The air must cool some of it into carbon mist or fog, just
as the steam issuing from a kettle is cooled into water mist at a short
distance from its mouth. The dissimilar action of the poles common
to so many electric phenomena displays itself in the arc at this point.
Instead of both poles volatilising the positive pole alone does. It is
considered, therefore, that the arc consists of (1) a thin layer of
carbon vapour issuing from the end of the positive carbon, (2) a bulb
of carbon mist joining this to the negative carbon, and (3) a sheath of
burning gases, formed by the burning of the mist, and the hot ends of
the carbons, and surrounding both. The vapour appears to be indicated
in images of the arc by a sort of gap between the arc and the positive
carbon, the mist by a purple bulb, and the gases by a green flame.
The flame is found to be practically insulating, so that nearly the
whole of the current flows through the vapour and mist alone. It is
suggested that the vapour has a high specific resistance compared with
that of the mist, and that it is to the great resistance of this vapour-
film that the high temperature of the crater is: due, and not to any
large back K.M.F. of which it is the seat.
Volatilisation can only take place at the surface of contact between
the vapour film and the positive carbon. When that surface is smaller
than the cross-section of the end of the carbon, it must dig down into
the solid carbon and make a pit. The sides of the pit, however, must
be hot enough to burn away where the air reaches them, hence there
is a race between the volatilisation of the centre of the carbon and the
burning of its sides that determines the shape of the carbon. When
the are is short, the air cannot get so easily to the sides of the
The Mechanism of the Electric Are. 411
pit, hence it remains concave. When the arc is long, the burning of
the sides gains over the volatilisation of the centre, and the surface of
volatilisation becomes flat, or even slightly convex.
The peculiar shaping of the negative carbon is shown to be due to
its tip being protected from the air by the mist, and its sides being
burnt away under the double action of radiation from the vapour
‘film and conduction from the mist, to a greater or less distance,
according to the length of the are and the cross-section of the vapour
film.
It is shown that if the crater be defined as being that part of the
positive carbon that is far brighter than the rest, then the crater must
be larger, with the same current, the longer the arc, although the area
of the volatilising surface is constant for a constant current.
By considering how the cross-section of the vapour film must vary
with the current and the length of the arc, it is found that its
resistance 7, must be given by the formula
hk ml
i aa ie Chas
where h, k, and m are constants, / is the length of the arc, and A the
current. This is the same form as was found by measuring the P.D.
between the positive carbon and the arc by means of an exploring
carbon, and dividing the results by the corresponding currents. Hence
the existence of a thin film of high-resisting vapour in contact with the
crater would not only cause a large fall of potential between the
positive carbon and the arc, exactly as if the crater were the seat of a
large back E.M.F., but it would cause that P.D. to vary with the
current and the length of the arc exactly as it has been found to vary
by actual measurement.
The Apparent “ Negative Resistance.”
As nearly all the current flows through the vapour and mist, the
surrounding flame being practically an insulator, the resistance of a
solid carbon are, apart from that of the vapour, must depend entirely
on the cross-section of the mist. To see how this varies with the
current, images of an arc of 2 mm. were drawn, with the purple
part—the mist—very carefully defined, for currents of 4, 6, 8, 10, 12,
and 14 amperes. The mean cross-section of the mist was found to
increase more rapidly than the current, consequently its resistance
diminishes more rapidly than the current increases. As the formula
for the resistance of the vapour film shows that it too diminishes faster
than the current increases, it follows that the whole resistance of the
are does the same, and that consequently the P.D. must diminish as the
current increases. Hence if 6V and 6A be corresponding increments of
2G 2
al
)
412 Mrs. H. Ayrton.
P.D. and current 6V/6A must be negative, although the resistance of the
are 18 positive.
It is found, from the above measurements of the cross-sections of
the mist, that the connection between mm, the resistance of the mist,
and the current, is of the form,
)
i ae
AN ae
If m varies directly with the length of the arc, then
Ly ceils en
m= (f+) ie
Adding this equation to (1), we get
p+q st+tl
ftm=r Ban nies
for the whole resistance of the arc, which is exactly the form that
was found by dividing direct measurements of the P.D. between the
carbons by the corresponding currents. Hence there is no reason why
this ratio should not represent the ¢rue resistance of the are.
Under what carcumstances V/A measures the True Resistance of the Are.
When the current is changed it takes some time for the vapour
film to alter its area to its fullest extent, and still more time for the
carbon ends to change their shapes, All the time these changes are
going on the resistance of the arc, and, consequently, the P.D,
between the carbons, must be altering also. Both these, therefore,
depend not only on the current and the length of the arc, but also, till
everything has become steady again, z¢., till the are is “ normal”
again, on how lately a change has been made in either. At the first
instant after a change of current, before the volatilising area has had
time to alter at all, 6V and SA must have the same sign, just as they
would if the arc were a wire, but as the volatilising surface alters, the
sign of 6V changes. If, therefore, a small alternating current is applied
to the direct current of an arc, it will depend on the frequency of that
current whether 6V/sA is positive or negative. When the frequency
is so high that the volatilising surface never changes at all, dV/dA
will measure the true resistance of the arc, unless it has a back E.M.F.
which varies with the alternating current.
The measurements of the true resistance of the arc made in this
way by various experimenters have given very various results, because
probably the frequency of the alternating currents employed has been
too low not to alter the resistance of the arc. A curve is drawn
showing how the value of 6V/3A with the same direct current and
The Mechanism of the Electrie Are. ARGS
length of arc varies with the frequency of the alternating current, and
it is pointed out that even if the arc has as large a back E.M.F. as is
usually supposed, the true resistance cannot be measured with an
alternating current of lower frequency than 7000 complete alternations
per second.
The exact conditions under which the true resistance of the arc can
be measured in this way are examined, and the precautions that it is
necessary to take to ensure the fulfilment of these conditions are
enumerated.
*
The Changes introduced into the Resistance of the Are by the Use of Cored
Carbons.
A core in either or both carbons has a great effect on both the P.D.
between the carbons and the change of P.D. that accompanies a given
change current. It lowers the first, and makes the second more
positive, 7.¢., gives it a smaller negative or larger positive value, as
the case may be. It is pointed out that this might be due to the
influence of cores either on the cross-section of the arc, or on its
specific resistance, or on both.
To see the effect on the cross-section, enlarged images were drawn
of 2 mm. arcs with currents increasing by 2 amperes from 2 to 14
amperes, between four pairs of carbons, + solid — solid, + solid
— cored, + cored — solid, + cored — cored. Two sets of images
were drawn with each pair of carbons—the one immediately after a
change of current, to get the “non-normal” change, and the other
after the arc had become normal again. ‘The mean cross-section of
the mist was calculated in each case, and its cross-section where it
touched the crater was taken to be a rough measure of the cross-
section of the vapour film.
It was found that the mean cross-section of the mist with a given
current was largest when both carbons were solid, less when the
negative carbon alone was cored, less still when the positive alone was
cored, and least when both were cored. Coring either the positive
carbon alone, or both carbons, had the same effect on the cross-section
of the vapour film as on that of the mist, but coring the negative
alone only diminished this cross-section immediately after a change of
current, but not when the arc had become normal again. Hence it
was deduced that if the cores altered the cross-sections of the arc only
they would increase its resistance, and, consequently, the P.D. between
the carbons. As they lower this, however, they must do it by lowering
the specific resistance of the are more than they increase its cross-
section. The vapour and mist of the core must therefore have lower
specific resistances than the vapour and mist of the solid carbon.
When it is the positive carbon that is cored, all the vapour and mist
414 The Mechanisin of the Electric Are.
come from the cored carbon. When the negative, they come from the
uncored carbon, and it is only because the metallic salts in the core
have a lower temperature of volatilisation than carbon that the mist is
able to volatilise these and so lower its own specific resistance.
The effect of a core in either carbon, or in both, must depend on
the current, because the larger the current the more solid carbon will
the volatilising surface cover, and the less therefore will the specific
resistances of the mist and vapour be lowered. The way in which the
core acts in each case is traced, and the alterations in the specific
resistances and cross-sections due to the core are shown to bring about
changes in the P.D. exactly similar to those found by actual measure-
ments of the P.D. between the carbons. It is shown, for instance, how
these changes entirely account for the fact established by Professor
Ayrton* that, with a constant length of arc, while the P.D. diminishes
continuously as the current increases, when both carbons are solid, it
sometimes remains constant over a wide range of current, or even
increases again, after having diminished, when the positive carbon is
cored.
The alterations in the value of 6V/d5A introduced by the cores are
next discussed, and it is shown that the changes in the resistance of
the arcs that must follow the observed changes in its cross-section,
coupled with the alterations that must ensue from the lowering of its
specific resistance, would modify 6V/SA just in the way that Messrs.
Frith and Rodgerst found that it was modified by direct measure-
ment. Thus all the principal phenomena of the arc, with cored and
with solid carbons alike, may be attributable to such variations in the
specific resistances of the materials in the gap as it has been shown
must exist, together with the variations in the cross-sections of the are
that have been observed to take place. Hence it is superfluous to
imagine either a large back E.M.F. or a ‘negative resistance.”
* Klectrical Congress at Chicago, 1893.
+ “The Resistance of the Electric Arc,” ‘ Phil. Mag.,’ 1896, vol. 42, p. 407.
report of Magnetical Observations at Kalimouth Observatory. 415
Report of Magnetical Observations at Falmouth QRB at for
the Year 1900. Latitude 50° 9’0” N., Longitude 5° 4’ 30 0Ne
height, 167 feet above mean elev.
The Declination and the Horizontal Force are deduced from hourly
readings of the photographic curves, and so are corrected for the
diurnal variation.
The results in the following tables, Nos. J, I, III, IV, are deduced
from the magnetograph curves, which have been standardised by
observations of deflection and vibration. These were made with the
Collimator Magnet, marked 664, and the Declinometer Magnet, marked
66C, in the Unifilar Magnetometer No. 66, by Elliott Brothers, of
London. The temperature correction (which is probably very small)
has not been applied.
In Table V, H is the mean of the absolute values observed during
the month (generally three in number), uncorrected for diurnal varia-
tions and for any disturbance. V is the product of H and of the
tangent of the Observed Dip (uncorrected likewise for diurnal
variation).
In Table VI the Inclination is the mean of the absolute observations,
_ the mean time of whichis 3 p.m. The Inclination was observed with
the Inclinometer No. 86, by Dover, of Charlton, Kent, and needles |
and 2, which are 34 ee in length.
The Declination and the Horizontal Force values given in Tables I to
IV are prepared in accordance with the suggestions made in the Fifth
Report of the Committee of the British Association on comparing and
reducing magnetic observations, and the time given is Greenwich Mean
Time, which is 20 minutes 18 seconds earlier than local time.
The following is a list of the days during the year 1900 which were
selected by the Astronomer Royal as suitable for the determination ot
the magnetic diurnal variations, and which have been employed in the
preparation of the magnetic tables :—
JAMUAL Yea 346 65) SSO, oll, Hebruary 3-3). O, ile
Miarch> oy) oo. ik Dilek 2S: April.. Beech Oy py
May ee 5 LO, RA aS. Mca nee MOM ITE GY ONO). 5).
July oe et Uae ed lish, pe 010). August Oy Gis Oe Wish SU)
sigjomemuleeie | 5 ti, Yale 25) Ele, October De le Mie Oe rile
November 5, 6, 11, 16, 30. December 3. 67 lay 23) 248
EDWARD KITTO,
Magnetic Observer.
SAP R Ob
NH ooOn
ON ANN A
GH in 18 D
DONO
ee
on Five selected quiet Days in
Table I.—Hourly Means of Declination at the Falmouth ©
Winter.
fepori of Magnetical Observations at
CM D> 10 SH CO
ODO © HX
ONNA ASN
Hm 9 Is bs
Oanoedeo
OO NN ANN NN
DN ADOND
ORDL100
CONN ANA NA
moro OS
HODmMOL
OO) OO ON NI NY NY
INP DW MH
HOOK-IlOKk
MOANA N A
19 DW O OH
me OG iky ©
MANNA N
t
28-5 | 28-1
PPR
28 “8 nae "28-8
416
(18° + West.)
284) 28 °6 |
Means
Summer.
~
~
~
~
~
~
~
i ig
1D 11 10 (©
AAA AAA
26-0
riwiy oO
CO 1D 10 19 20 1
NAN AA SN
SE Peee
Iv 10 101010
NANNASN
D> TH SHO Dro
Im CO CE 10 ©€ P~
NANNNA A
1D 1919 Is DS
© I bOI
| 26°2 | 25°6
Note.—When the sign is + the magnet points
I~ FN OD 1
DD OI~ DO
AANA A
Table I1.—Diurnal Inequality of the Falmouth
Annual mean.
Summer mean.
Winter mean
~
SO se ret SS
RONDO
NANNAN
*~ Mean of four days—2nd, 7th, 13th, 31st.
OM Hip w 19
DDD DO ®O 0
NANNANANN
4
SO ihs Sr et 18.2
D M DO DW WD
NANNAN
/
—0°4 |—0°2 |
|
|
!
—0°6
i
|
|
Falmouth Observatory for the Year 1900. AIT
‘Observatory, determined from the Magnetograph Curves
each Month during 1900.
Noon | 1 | 2 | 3 | gaa ks ay ie | s | 9 | 10 Ia. | Mid.
| | Bi ior oneal Sao |
Winter.
/ / / } I) / | / | / | / / if / / | /
33-2 | 34:0 | 33-3 | 32-6 | 82-1 32°3 31-7 31-1 | 30°8 ae 30°8 | 30°8 | 30°8
a2-5 | 33°6 | 33-8 | 32-6 | 31°5 | 31-0 | 30°7 | 30-5 | 30°5 | 30-1 | 30-3 | 30-4 | 30-7
#20 | 38-7 | 33°8 | 32-7 | 31-0 | 29-7 | 29-4 | 29-7 | 29°7 | 29-7 | 29-6 | 296 | 29-3
31-5 | 32:8 | 32-4 | 31-1 | 29-4 | 29-0 | 28-6 | 28-4 | 28°3 | 27-8 | 27-8 | 27-7 | 28-0
Pero 28-3 | 27-5 | 26-4 | 26-0 | 25-9 | 25-6 | 25-4 | 25-2 | 25-1 | 25:1 | 25:1 | 25-4
28-6 | 28-9 | 28-6 | 27-9 | 27-5 | 27°1 | 26°7 | 26°3 | 26°3 | 26°2 | 26-2 | 26-1 | 265
al -0 ies 81-6 30-6 | 29°6 | 29-2 | 28-8 | 28-6 | 28°5 28-3 | 28-3 | 28°83 | 28-5
Summer.
, , i / | / / | / / , | , | / , /
32°5 | 84-1 343 33-0 | 31°5 | 30°3 | 29-7 | 29°6 | 29°5 | 29-4 | 29-5 | 29-1 | 29-0
32-1 | 33-8 | 33°6 | 32-1 | 30-6 | 29-6 | 29-0 | 28°8 | 28-8 | 28-9 | 29-2 | 29-2 | 29:2
33°2 | 34-2 | 34°5 | 33-8 | 32-6 | 30°9 | 29°8 | 28°9 | 28-6 | 28°5 | 28-3 | 28-4 | 28°5
31°7 | 34:0 | 34-1 | 32-6 | 31-2 | 30-1 | 29-2 | 29-1 | 29-2 | 29-0 | 28-6 | 28-6 | 28-3
33°6 | 34°8 | 34-0 | 32-7 | 30°7 | 29-4 | 28-9 | 29-0 | 28-9 | 29-0 | 29°0 | 28-9 | 29°0
34-0 | 34°6 | 33-2 | 81-1 | 29-4 | 28°83 | 28-3 | 28°8 | 28-7 | 28-7 | 28-7 | 28-7 | 28-5
Ea |b Ce anal heh | } | }
82-9 | 34-3 | 34-0 32: 6 81-0 29-8 29-2 [29-0 | 29-0 | 28-9 | 28-9 | 28°8 | 28°8
Declination as deduced from Table I.
Summer mean.
| | | | |
, | ; , | 2 / / y f / , / ,
ee |e +3°4/4+1°8 +06 0:0 |—0-2 |—0-2 |—0°3 |—0°3 |-—0-4 |-0°4
‘ | |
Winter mean.
| 7 / J | / | / | 7 s ¢ | / / / /
ge ers +2°6 #16 406 ee eal —0°4 |—0°5 |—0°7 |-0-7 Oe ae
Annual mean.
|
, , , , | ,
+29 +40 ey eae te
to the west of its mean position.
{
|
/ y ,
+0 °4 |-Or1 ae
|
| J | / , | / ,
|
|
-0-4 | 0°5 O18) ea —0°5
418 Report of Magnetical Observations at
Table I1I.—Hourly Means of the Horizontal Force at Falmouth
0-18000 + (C.G:S. units). on Five selected quiet Days in
i | \ {
Hours |Mid.| 1 | 2 | Beil oan Site | Fete io: |. 9 |) aeneaee |
| |
W inter.
} |
| | | | | |
1900. | | | | | | |
Jan. ..) 671) 670 671 671 | 673 | 674) 676| 677) 675| 669| 663 | 660
Heb. ..| 672 | 672 6721 673 | 673| 674| 673| 674| 673| 669| 663 | 662 |
March .| 679 | 680, 679, 679| 679! 679| 678| 678| 675| G666| 662| 657
‘Oct. ..| 696 | 696 694 | 695| 697] 698; 699| 698] 695| 685| 676| 672
Nov. ..| 706 | 706 706/ 706| 707| 708| 708| 707| 703) 696} 692| 694
Dec. ..| 701 701; 702| 703} 703} 704| 704) 704] 704| 708} 701 | 699
—SS— S| ls ———— | =
Means| 688 | 688 | 687 | 688| 689 690 690 690, 688| 681| 676| 674
| | | | }
Summer.
| | | |
April..! 687 | 686! 686 687 686; 686| 685 | 686| 683) 678 668) 665
687 | 685 | 683, 683 682] 680! 676 | 672 | 668| 666) 666 |
June ..| 700 | 699 | 697, 697) 698} 698] 695} 692] 687 | 681 | 675 | 673
July ..| 702 | 701; 699 698] 698| 697 | 695 |
Aug. ..| 701 | 700} 698 698} 697! 697] 693 | 688] 681} 673 | 674) 680
Sept...! 707 | 705 | 704( 703 | 704|° 702 | 701 | 697 | 691 | 68a | 968%) Gem
(op)
we)
Ww
D>
7)
SI
| 697 | 696 695) 694 694 698 691 688 683 | 677 | 673 673
| | |
* Mean of four days—2nd, 7th, 13th, 31st.
Table [V.—Diurnal Inequality of the Falmouth
See | 1 | 2 | so. | 4. | ss Gol a Se 19 | ul
| | | |
Summer mean.
!
|
; i } ! | | | | | an ee | i, j c
+ °00005 + *00004 + -00003/+ -00002 + -09002 + 00001 — -00001'— -00004 | — “00009 — "00015|— 00019 ip “00019
1 | | i | i. | |
Winter mean.
| | Fie | |
iat “00002 + °09002 ia "00001 + -00002 + -00003 + -00004 + -00004 + -00004 + -00002)— -00005 — *00010 — 00012
! | | i | |
Annual mean.
| {
ees -00003
REA EES Ec
ie "00002 + -00002'+ *00003 + 00003 + :00002! TOS *00004' — -00010 hes °00015 — -00016
| \ | | | {
Note.—When the sign is + the reading
Falmouth Observatory for the Year 1900. ANG
Observatory, determined from the Magnetograph Curves
each Month during 1900.
| '
Boom) 1) 2 Sb bd nes 8 | 6 | 7 | 8 | 9 | 10 | 11 aee
! |
Winter.
| | oa
| | |
662, 667, 671; 671 | 671 670 671 al 674 | 675 | 673 | 673) 673
662 664) 667; 668| 669| 672) 673 673 | 674 | 674 | 674) 675 | 674
662 | 669/| 675 | 679| 681 | 681) 681 = 685 | 684] 684 {| 684) 685
{
———————————
{ |
Summer.
670 678 | 687; 692) 693; 691 | 693 {| 694] 695 | 694] 693 | 692 | 693
670 Gideon) onde) 1677) G80 | (E85) G2: G94 | 693.) 691 | GOL |} 691 691
678 684 | 691 | 700 | 699] 700! 704; 705 |. 704| 703 | 700; 699] 699
Sse ress,| “689 | “G90 |} 698 | .°698 | 698") FOL | 702°| 704 708 |) 703: | ax7On
Got) 697 | 698 | 700; 700 | 699 | 699 | 704 |} 704-| 704) 703 | 703 | 7038
688 GISr i, (OL | 702") 704") 702) 704") 708 | 707-1 - 707% 705 |. 708?) 7706
680 686 | 690 | 694-|" 696 | 696 | 698-7OL | 7OL | 701+ 699'|. 699)) G39
Horizontal Force as deduced from Table III.
| Noon Mar igi e. (Hak 'g ies. eb a0 | ee
|
}
|
|
Summer mean.
| | | | | | | | ee. 2!
— 09012 — 0006 — °00002 + -00002 + 00004 + 00004 + eee | + 00000) + *00009| + *00009 + "00007, + °00007 + "00007
| | | | |
|
! | |
Winter mean.
+ -00004
nea :
- 00010) — 000 - *00002 + °00002)| + °00003| + °00004| + °00065|+ °00004;+ °00004/+ *00004
na “00001
Annual mean.
+ °00003)+ *00005) 3F 0007 ae 0007 + “00007 + 00006
| {
<5 0005 + °00906
-
— °00011 — -00006
|
i
— *00002
as on) + *00008
is above the mean.
‘i
%
420 Report of Magnetical Observations at Falmouth Observatory.
Table V.—Magnetic Intensity. Absolute Observations.
Falmouth Observatory, 1900.
C.G.S. measure. |
| H or V or
Pantie Horizontal force. | Vertical force.
| January es cee ee 0 -18665 0 °43503
February . mite ay 0 -18660 0 °43474
| Narciicg eae ee: 0 -18661 043476
Apel. 018676 0 *43508
| May . 0:18677 0 °4.3500
June. 0°18682 0 °43463
July.. 0 -18686 043458
| Aug sean 0°18681 0 °43460
September . ‘ 0 -18696 0 °4:3495
October, «eee 0:°18683 0 -43489
November .. O °18696 0 °434.99
December... 0 ‘18696 0 °434.95
| Wie anisiivis cin crite: O 18680 0° 43485
Table VI.—Magnetic Inclination. Absolute Observations.
Falmouth Observatory, 1900.
Month. | Mean. Month. | Mean. |
| sanuary 102. A weet. (866) 46.80 July 10. al ae 43.7
2A et kee (SOOs AGE 20... ays 5 seat) GO
| She... Snags: (166, 4677 30... | 66 43°9
| 66 46°7 66 44-0
j aes yy ae SSS
February 10,........--.| 66 45°9 |) August. 12...00. so epee mo Gmmnecemes
| Dalen anes ane | 66 46°6 26 | 66 44°3
| 2B slop sole lt | 66 46-0 31 66 45-0
| 66 46:2 66 44-4
March 10): 2... 4.4...) 60) 4666 |i (Septemberl a jane) shee (66 44°4
| PAT I. ttete ols 3 | OO RI AO gO 5 Cs MPP) (010) 6 2b Ss
aan Smee 66 45°5 66 44-4 |
po October 8.........2- 4.8) 08 au
April Oi ane ekeuee 66 47°0 20... 0... 0. Se ees
PHO es en iauta ts here 66 45°8 225. oes s ne calas| OOMenORES
i 28 lin. bi sie cidsan ee 66 45°5 BO... es cea ne ROO EnOE
ae Nias aa
| 66 46:1 | 66 45:1
May LO} isle dan tds 05) OC ae 2m MEN overmber 10,52. eee 66 45-7 |
Bra hate CU kGO eons 21... Sus be
SOMME che lle er OO gaan 29. wienieie's eia'edn sl OOM
66 45 °8 66 44°5
June Nise eae auds amu MO OUNr eA ES December le nuw emir | 66 43-5
| DOnc os or cnete | OO) Aac6 19,2 0. eas se oss | Oona
f DOr hs oes 66 44°9 Se ihe | 66 43-7 |
|
| (66 44-4 | 66 44 °4
THE NATIONAL PHYSICAL LABORATORY.
Report on the Observatory Department for the Year
ending December 31, 1900.
The work at the Kew Observatory in the Old Deer Park at Richmond,
now forming the Observatory Department of the National Physical
Laboratory, has been continued during the year 1900 as in the past.
This work may be considered under the following heads :—
I. Magnetic observations.
IT. Meteorological observations.
III. Seismological observations.
IV. Experiments and Researches in connexion with any of the
departments.
VY. Verification of instruments.
VI. Rating of Watches and Chronometers.
VII. Miscellaneous.
I. MAGNETIC OBSERVATIONS.
The Magnetographs have been in constant operation throughout
the year, and the usual determinations of the Scale Values were made
in January.
The ordinates of the various photographic curves representing
Declination, Horizontal Force, and Vertical Force were then found
to be as follows :—
Declinometer : 1 cm. = 0° 8°7.
Bifilar, January, 1900, for 1 em. 6H = 0:00051 C.G.S. unit.
Balance, January, 1900, for 1 cm. 6V = 0:00049 C.G.S. unit.
The distance between the dots of light upon the vertical force
cylinder having become too small for satisfactory registration, the dots
_ were separated on June 20 by slightly altering the position of the
zero mirror.
The curves have been quite free from any large fluctuations ; indeed,
no unusual disturbance has been registered for some time past. The
principal variations that were recorded during the year took place on
the following days :—
> January 19th-20th ; March 8th—9th and 13th ; May 5th.
The hourly means and diurnal inequalities of the magnetic elements
for 1900, for the quiet days selected by the Astronomer Royal, will be
found in Appendix I.
422 ! The National Physical Laboratory.
A correction has been applied for the diurnal variation of tempera-
ture, use being made of the records from a Richard thermograph as well
~ as of the eye observations of a thermometer placed under the Vertical
Force shade.
The mean values at the noons preceding and suceeedime the selected
quiet days are also given, but these of course are not employed in
calculating the daily means or inequalities.
The following are the mean results for the entire year :—
Mean Westerly Declination............ 16° 52"°7
Mean Horizontal Force ......... Bhat ay 0°18428 C.G.S. unit.
Mean inclination? pee toe ee, ee 67° 1158
Mean: Vertical! Moréen.e ass ee 0°43831 C.G.S. unit.
Observations of absolute declination, horizontal intensity, and ineli-
nation have been made weekly as a rule.
A table of recent values of the magnetic elements at the Observa-
tories whose publications are received at Kew will be found in
Appendix IA to the present Report.
A course of magnetic instruction was given to Captain Denholm
Fraser, R.E., charged with a magnetic survey of India, and facilities
were afforded him for making experiments with a view to improving
the instrumental outfit for the survey.
A new magnetic hut was erected early in the year by Mr. Eldridge.
It is larger and better lighted than the old hut, and has proved very
useful.
II. METEOROLOGICAL OBSERVATIONS.
The several self-recording instruments for the continuous registra-
tion of Atmospheric Pressure, Temperature of Air and Wet-bulb,
Wind (direction, pressure and velocity), Bright Sunshine, and Rain
have been maintained in regular operation throughout the year, and the
standard eye observations for the control of the automatic records
have been duly registered.
The tabulations of the meteorological traces have been regularly
made, and these, as well as copies of the eye observations, with notes
of weather, cloud, and sunshine, have been eae as usual, to the
Meteorological Office.
With the sanction of the Meteorological Council, data have been
supplied to the Council of the Royal Meteorological Society, the
Institute of Mining Engineers, and the editor of ‘Symons’ Monthly
Meteorological Magazine.’ On the initiative of the Meteorological
Office, some special cloud observations have been made in connection
with the International scheme of balloon ascents.
Electrograph.—This instrument worked generally in a satisfactory
manner during the year.
The small glass beaker mentioned in last year’s Report is still
Report on the Observatory Department. 423
employed, and by removing the sulphuric acid at regular periods—
generally fourteen or fifteen days—the troubles previously experienced
with the “setting” of the needle and with the shift of zero has been
largely overcome.
No systematic use has been made of the thirty-six Clark cells men-
tioned in the 1898 Report, but they have been employed to check the
scale values of the two portable electrometers.
Scale-value determinations of the electrograph were made on April 2,
July 14, and October 25, and the potential of the battery has been
tested weekly. Forty cells only have been employed during the year,
giving about 30 volts.
With a view to promoting uniformity in procedure, the Superin-
tendent, at the suggestion of the Meteorological Office, had an inter-
view with Mr. C. T. R. Wilson, F.R.S., and Mr. W. Nash, of Greenwich
Observatory, who were shown the electrograph arrangements and the
means adopted for standardising the curves. The stoppage this
entailed in the working of the instrument was utilised in giving it a
thorough cleaning. A new bifilar suspension was also fitted to the
needle, and the wire leading from the can to the electrometer was
bedded in paraffin wax in hopes of improving the insulation.
Inspections.—In compliance with the request of the Meteorological
Council, the following Observatories and Anemograph Stations have
been visited and inspected :—North Shields, Glasgow, Aberdeen,
Alnwick Castle, Deerness (Orkney), Falmouth, and Fort William, by
Mr. Baker; and Radcliffe Observatory (Oxtord), Stonyhurst, Fleet-
wood, Armagh, Dublin, Valencia, and Yarmouth, by Mr. Constable.
III. SEISMOLOGICAL OBSERVATIONS.
Professor Milne’s “ unfelt tremor” pattern of seismograph has been
maintained in regular operation throughout the year; particulars of
the time of occurrence and the amplitude in seconds of arc of the
largest movements are given in Table I, Appendix III.
The “ disturbance ” on January 20 was particularly noticeable.
The movement was the largest that has yet been fully recorded at
the Observatory, the maximum amplitude being 15 mm., or 12°6 seconds
of arc. The next largest disturbance was on October 29, with a maxi-
mum of 12 mm., or 9°5 seconds of arc.
The action of the boom was not altogether satisfactory during
August and September, and on September 27 the old boom was
replaced by a new one of standard pattern. The balance weights are
at 117 mm. and the tie at 127 mm. from the cup end of the boom.
The point of the bearing pivot on the stand was also improved.
A detailed list of the movements recorded from January 1 to
December 31, 1900, was made and sent to Professor Milne, and will
be found in the ‘ Report’ of the British Association for 1901, ‘ Seismo-
logical Investigations Committee’s Report.”
CS SR ee oem oe
r at
424 The National Physical Laboratory.
During October a Milne seismograph, No. 31, intended to be set up
at the University Observatory, Coimbra, was fitted up in the seismo-
graph room, at the same height and in the same N.—S. direction as the
Kew Instrument, and a series of comparisons were carried out till the
end of the year. Several interesting features were noticed, and the
results have been embodied in a paper by the Superintendent.
IV. EXPERIMENTAL WORK.
Fog and Mist.—The observations of a series of distant objects,
referred to in previous ‘ Reports,’ have been continued. A note is taken
of the most distant of the selected objects which is visible at each
observation hour.
Atmospheric Electricity—The comparisons of the potential, at the
point where the jet from the water-dropper breaks up, and at a fixed
station on the Observatory lawn, referred to in last year’s ‘ Report,’
have been continued, and the observations haye been taken since
March on every day when possible, excluding Sundays and wet days.
The ratios of the “ curve” and the “ fixed station ” readings have been
computed for each observation, and these have thrown considerable
light upon the action of the self-recording electrometer, especially with
reference to its insulation. Some direct experiments have also been
made on this point. |
The reservoir holding the supply of water for the water-dropper of
the self-recording electrometer is supported upon six large “ Mascart ”
insulators, and it was thought that perhaps this system of insulating
the tank could be improved upon.
A quantity of fine paraffin wax, with a high melting point, was
procured from Price’s Candle Company, Limited, in rectangular blocks,
and a number of cylinders of sulphur were cast at the Observatory.
Three similar water tanks were supported upon three wax blocks,
three sulphur blocks, and three Mascart insulators respectively. Each
received a similar definite charge, and the rate of loss of charge was
observed. |
The observations—which are to be regarded only as preliminary—
extended through May, June, and July, under various hygrometric
conditions. The sulphur and paraffin when new and clean gave much
the best values, but after the lapse of a few weeks the rate of loss
became very similar for all three species of insulator. The deteriora-
tion was apparently due to accumulation of dust, &c. The provision
of a hood or cover to the sulphur and paraffin blocks would undoubtedly
improve the permanency of their insulating qualities.
Platinum Thermometry.—The paper by the Superintendent, referred
to in last year’s Report, has been published in the Royal Society’s
2
‘Proceedings,’ vol. 67, p. 3.
Report on the Observatory Departinent. 423
V. VERIFICATION OF INSTRUMENTS.
The subjoined is a list of the instruments examined in the year
1900, compared with a corresponding return for 1899 :—
Number tested in the year
ending December 31.
AS
= =
1899, 1900.
2 Ie ee 6 9
PMMEMIOMPE LEG) Sasi os2 foaaiie.s ois cede sie ee ees 23 ]
Js SEEIT TG Spo oh re ne ara etna gare Li. 197
Atrprietal WOVIZONS) ccviceciecs cece weiss Fe 9 27
Maremeterss Marine ..........06--0heees oe 92 139
" SUBIC A IRS ats Mae are a 85 57
ms SUBTLE) Ts iene AS Bae mio CE 15 23
SIMONE ARG ER Sette ss cba os Se ain See LaGak aes 404 963
= DID TEINS Rg Gee OP eee 43 51
WSS E ORS 200. ses eet, cores 6 1
Ppp GOMHe erst: ears ksi 48 Jobst ace eenee. 241 173
TOG] STRUTT SUAS) be 9 17
iPnetoenaphic Lenses... 2.2..6...00..25. 65. 160 136
Breer tie. ek ik Masai Sk Stine. 3 1
SGC OEE UA em eae 561 1,345
LUSTING Sie ee Ne oe 19 t
Rain-measuring Glasses .................. 44 29
Ricaleen, GWE Aas itera. osha es mas ii
SERUM RIES Hiab OL tins Sank CYS alate hits 876 813 :
unshane Recorders... .~. vt u.usavercsk ote 6 3
JZIDEC LOTTE Oa a He na a Os 24. 3 12
Thermometers, Avitreous or Immisch’s 5 —
ms Chimica ea ena ne 16,020 20,476
i Weep sea MAG GRE 19 83
Re oh hangee 2200. 7. 62 40
" EFypsometric © a2 ¥.<:: 39 66
4 ow Iuange se 103 33
- Meteorological ......... 2,892 2,786
o Solarradiationm......... — 2
i RO UAIMCLENRCE REAL he HAL a 104 61
Winihtlars AG ae GUE he) Pet 5 5
Vertical Force Instruments ............ 1 14
Dechnometens ie seek he abe —- 1
a eftetliyy Wat ode ah teh ecto 22,051 27,569
Duplicate copies of corrections have been supplied in 56 cases.
VOL. LXVIII. PA ae
= 9 oa
7 Z
426 The National Physical Laboratory.
The number of instruments rejected in 1899 and 1900 on account of
excessive error, or for other reasons, was as follows :—
1899. 1900.
Thermometers; clinieal 4. hcg sgh 149 nite
ue ordinary meteorological ... 78 79
SE KAM S een sce ee se ee eee 151 122
ihe ESCO WES ioe hie eiu eee ee Rae eee 49 116
AMO Cubs 47 cA ect tee A noe 21 ou
eT OUS a veces Geese es Genet ERR One Merry 14 28
Four Standard Thermometers have been constructed during the
year.
There were at the end of the year in the Observatory, undergoing
verification, 16 Barometers, 285 Thermometers, 15 Sextants, 250 Tele-
scopes, 30 Binoculars, 2 Hydrometers, 4 Rain Measures, 2 Rain Ganges,
and 4 Unifilar Magnetometers.
VI. RATING oF WATCHES AND CHRONOMETERS.
The number of watches sent for trial this year is slightly less than
in 1899, the total entries being 403, as compared with 469 in the pre-
ceding year.
The “especially good” class A certificate was obtained by 98
movements.
This is a marked increase on the number obtained in 1899, and the
general performance has been decidedly better.
The following figures show the percentage number of watches
obtaining the distinction “ especially good,” as compared to the total
number obtaining class A certificates :—
“Year 2.5 s