594 
NATURE 
Mr. J. T. Barber of Spondon, Derby, informs us that on April 6, 
the night of the above observation at the Collegio Romano, he 
considered that the total impression given by the comet’s light 
was. about equal to that of a star of the seventh magnitude. If 
we take the theoretical intensity of light (represented by the 
reciprocal of the product of the squarcs of the distances of the 
comet from the earth and sun) as wsz¢y, we find the intensity on 
the following dates :— 
May 12\... 7°1 | May 20 ... 1178 || May 28... ... 9 2 = i242 
Hah nO) 24 ... 16°0 | June 10 (perihelion) 1590°0 
THE SOLAR EcLipsE oF MAy 16.—The Nautical Almanac 
gives the following particulars of this phenomenon, which is 
seen as a small partial eclipse in these islands :— 
Angle from 
Magnitude N. point 
Begins. Greatest phase. Ends. (sun's dia- of first 
meter=z). contact. 
Direct. 
h. m. hm. h. m. - 
Greenwich 18 10°5 ... 18 46°0 ... 19 2370 ... o°186 158 
Cambridge 18 13°2 ... 18 47°7 ... 19 23°7 ... O175 159 
@xford es. 1S 07-2 <..-18 41 °2)-.. 19) 16°7 ... 02078 160 
Liverpool 18 6°2... 18 36°7...19 8-4 ... 07139 163 
Edinburgh 18 13:2... 18 4o"2... 19 81... O°IO5 ... 167 
DMpline ee hha 5 TG e2°Q)... DS e515... ON TOn ee TOO 
If we apply the Littrou-Woolhouse method of distributing 
the times approximately over this country we have the following 
equations :— 
G.M.T. of h. m. 
Beginning ... . 18 6°12+[0°4696] L —[9°2403] M. 
Greatest phase ... 18 43°58 +[0°2142] L+[8-5528] M. 
Ending pia ts: 19 22°58+[9°4197] L+[9°4134] M. 
The magnitude is given by 0°205 — [8°115] L+[7°250] M. 
Here the latitude of the place for which the Greenwich times 
are required is put =50°+L (and expressed in degrees and 
decimals), and M is the tongitude from Greenwich, taken posi- | 
tively towards the east, and expressed in minutes and decimals 
of time. 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE 
OxrorD.—Prof, Odling will conclude this term his course on 
the Atomic Theory; Mr. Fisher will lecture on Inorganic 
Chemistry ; and Mr. F. J. Brown will form a class for practical 
instruction in organic chemistry. 
Prof. Lawson will lecture at the Botanic Gardens on the 
General Morphology of Plants, and will continue his course on 
the Elements of Systematic Botany. 
Mr, Yule will give a course of demonstrations at the Magdalen 
College Laboratory, on the Physiology of the Nervous System. 
A Postmastership in Physical Science is offered by Merton 
College in June. The examination will be held in common 
with Magdalen and Jesus Colleges. The Postmastership is of 
the annual value of 80/., and is tenable for five years from 
election, proyided that the holder does not accept or retain 
any appointment 
full course of University studies. After two years’ residence 
the College may raise, by a sum not exceeding 20/. per 
annum, the Postmastership of such Postmasters as shall be 
recommended by the Tutors for their character, industry, and 
ability. 
Candidates for the Postmastership, if members of the Uni- 
versity, must not have exceeded six terms of University standing, 
but there is no limit of age. 
Mr. J. Perry, M.E., has been elected to the Chair of 
Mechanical Engineering at the City and Guilds Technical 
College, Finsbury, at the open election this week. 
SOCIETIES AND ACADEMIES 
LONDON 
Royal Society, March 30.—‘‘On the Movement of Gas 
in ‘ Vacuum Discharges.’”” By William Spottiswoode, F.R.S., 
and J. Fletcher Moulton, F.R.S. 
In the preparation of tubes for our experiments, it was often 
noticed, that after the exhaustion had been carried to a certain 
degree, the passage of a strong current had the effect of in- 
creasing the pressure. This appeared to be due to an expulsion 
incompatible with the pursuance of the | 
| 
of gas from the terminals themselves by the passage of the dis- 
charge. And accordingly the use of such currents from time to 
time during the process of exhaustion was adopted for making 
the vacuum more perfect and more permanent than otherwise 
would have been the case. On the other hand, it was also 
noticed, that after the tube had been taken off the pump and 
sealed in the usual way, the passage of a strong current had in 
some instances the effect of decreasing the pressure. We thus 
met with two effects, apparently due to the same cause, but 
diametrically opposite in character. 
Matters remained in this rather confused state, until we ob- 
served, with more care than befcre, a tube of which the exhaus- 
tion was near the phosphorescent state, and of which both 
terminals were metallic cones, and consequently presented large 
surfaces for any action which might take place upon them. 
In what may be considered to have been its normal condition, 
this tube showed three or four large white strize with a dark 
space of considerable size round the negative terminal. On 
passing the discharge through the tube for some minutes, the 
dark space increased, the striae became fewer and feebler in 
illumination, the green phosphorescence began to show itself, 
| and the discharge showed the usual signs of reduced pressure. 
On suddenly reversing the current, the striz became again more 
numerous and more brightly illuminated, precisely as they would 
be by an increase of pressure, while the other features of the 
discharge in a great measure resumed their original character. 
The most probable explanation of these phenomena appears 
to be this, that the effect of the discharge is actually to alter the 
pressure inthe tube, not by any modification in the chemical 
composition of the gas, but simply by driving occluded gas out of 
one terminal, and by drawing i: in, or occluding it, at the other. On 
reversing the discharge, the operation is reversed, and the occluded 
contents of one terminal are thrown along the tube to be oceluded 
atthe other, This view of the mechanism whereby the observed 
| phenomena are produced is supported by the absence of these 
appearances when the terminals are comparatively small and the 
pressure is such that the occluded contents of the metallic mass 
forming one terminal would form only a small fraction of 
the total mass of gas in the tube; for in that case the pressure, 
and consequently the appearance of the discharge, would be 
affected only in an inappreciable degree by the injection of the 
contents of the terminal. It should also be added that, when 
the terminals are of unequal size, the effects are unequal, as 
might have been expected. 
The phenomena in question appears to have so important a 
bearing on the mechanism of the discharge itself that it becomes 
a question of great interest to determine whether the missing gas 
is tobe found in either of the terminals; and, if so, whether 
the ejection takes place at the positive, and the occlusion at the 
negative terminal, or vice versd@. For this purpose, I have 
devised a tube with three terminals, but have not yet had time 
to complete its construction or to make the experiment. 
Zoological Society, April 4.—Prof. W. H. Flower, LL.D., 
F.R.S., president, in the chair.—Mr. Sclater exhibited and made 
remarks on an example of a rare Flycatcher (Cyanomytas cat- 
destis) from the Philippines, which had been sent to England for 
determination by Dr. Moesch of Zurich.—Mr. Sclater also ex- 
hibited and made remarks on two specimens of the Subcylindrical 
Hornbill (Buceros subcylindricus), which had been formerly living 
in the Society’s Gardens.—Dr. A. Giinther read the description 
of a new species of freshwater Turtle from Siam, a specimen of 
which had been recently acquired by the British Museum. The 
author proposed to name it Gevemyda impressa, from the peculiar 
shape of the principal upper plates, which are not merely 
flattened, but distinctly concave.-—Mr. W. A. Forbes read a 
paper on the structure of the convoluted trachea of two species 
of Manucode (Aanucodia atra and Phonygama gouldi), and 
added remarks on similar conformations in the trachee of other 
birds.—Mr. J. E. Harting read a paper on the eggs of three 
species of wading-birds which had been obtained by the Rev. 
W. Deans Cowan in the neighbourhood of Fianarantosa in the 
Betsileo country, Madagascar. The species to which these eggs 
belonged were Glareola ocularis, Aigialitis geoffroyt, and Gal- 
linago macrodactyla. Much interest attached to these eggs, as 
not having been previously described.—A communication was 
read from Mr. E, P. Ramsay, C.M.Z.S., containing the descrip- 
tion of a supposed new species of 7zpAras, an example of which 
had been obtained by the late Mr. S. White while collecting at 
the Aru Islands. The author proposed to name it 7ephras 
whitet, after its discoverer. 
| | Apri 20, 1882 
