174. 
From a mean of two sets of experiments we may conclude that 
this arrangement does not much influence the results. 
The disc was next treated in the following manner :— 
It was covered with a chamois leather blind tied into holes 
drilled in the disc, and having two pieces of different shape cut 
out. The experiments gave (for an atmosphere of 3% dry 
hydrogen) tapping in A 54, tapping in B 56, while for an 
uncovered disc they gave 53 as the heat-result, All these 
experiments apparently combine to prove that the result is not 
due to vibration. 
Our next experiments were made with the view of testing 
whether or not the two effects, the residual and the gas-effect, 
were resident in the same particles of the disc ; and for this purpose 
the experiments made immediately after rotation were compared 
with those made one minute afterwards, 
The experiments available for this purpose are so numerous 
that they can bear splitting into two portions, in each of which 
the same result is seen. 
Thus we have for an atmosphere of 39; dry hydrogen, and as 
the mean of 30 individual comparisons. , 
Effect at first : Effect one minute after :: 1°30 : I; 
also, as the mean of 22 individual comparisons, we obtain the 
proportion of 1°19 : 1,while as the mean of the whole we obtain 
1°25: 1. 
Treating in a similar manner the observations made with an 
atmosphere of # hyd. + <°; air, we obtain 
As the mean of 25 comparisons 
As the mean of 21 comparisons ............... 
while as the mean of the whole we obtain 1744 : I. 
We therefore conclude that the residual effect is less diminished 
during the interval of one minute than the gas-effect. 
We next made experiments with two aluminium discs ‘05 and 
025 of an inch in thickness respectively. These discs were covered 
on both sides with a coating of lampblack applied by negative 
photographic varnish. 
From these experiments it was concluded that there are two 
effects which are differently distributed over the particles of the 
disc. 
It also appeared that the effect for.*, hyd. which may be 
supposed to represent the residual effect, and that for 5 hyd. 
+4!; air, which may be supposed to represent the gas-effect, are 
both diminished in very nearly the same proportion, namely 
100: 77, by a transference of the pile to a position nearer the 
cenite of the disc. And it was furthermore conclu.ed from the 
experiments that in an aluminium disc covered with varnish, as 
well as in a disc of ebonite, we may imagine the residual effect 
to be more deeply seated than the gas-effect. 
We venture on the following as what appears to us to be the 
most probable explanation of the whole body of experiments, 
including those with radiation. 
(1) There is a temporary heat or cold effect which may 
be supposed to arise in particles very slightly attached to the 
disc ; this is radiated off chiefly during rotation, and does not 
probably greatly affect the disc afterwards. 
(2) There is a surface gas-effect, which in an aluminium and 
even in an ebonite disc 1s conducted into the interior as it arises, 
so that it does not greatly radiate during rotation of the disc. 
In a paper disc, however, which is formed of a badly conducting 
material loosely put together, part of the effect does escape as 
radiation during rotation. 
(3) There is a residual effect, which is more deeply seated 
than the gas-effect. And inasmuch as radiation takes place from 
a perceptible depth, this effect is much more influential than the 
gas-eflect in increasing radiation alter rotation, In the case of a 
paper disc, this deeply seated effect will be less diminished by 
radiation during rotation than the gas-effect, and therefore after 
rotation in such a disc we might expect the gas-effect to be 
pecuiiarly small. 
In the course of these experiments we have endeavoured to 
prove that this residual effect is not caused by vibration. The 
radiation-experiments with aluminium discs of three different 
thicknesses went, on the other hand, to show that it was of the 
nature of a surface-effect. This is confirmed by the results de- 
rived from tapping ; for, in the first place, the experiments with 
aluminium discs show that the two effects (the residual and the 
gas-effect) are probably distributed in the same proportion, going 
from the centre to the circumference of the disc. Again, taking 
the two discs of thickness ‘o5 and ‘025 of an inch, we obtain 
the following results :— 
NATURE 
PEI iy > oye a ee ee SOS RS ae 
Vy mt ia th VRAD) Cee 
2 - pee Aw 
a 
* 
| 
| Fune 26, 1873 
Effect for »*, hyd. Effect for yi; hyd. +3; air. 
Thin disc ... 48 (22 observations). 228 (10 observations), 
Thick disc... 29 (20 observations). 103 (10 observations), 
Now, allowing for errors of experiment, we see that the resi- 
dual, as well as the gas-effect, is reduced to about one-half for 
the thick disc. 
Again, an experiment of a similar nature gave the effect for 
zy hyd. in an ebonite disc of 7; insin thickness = 33 against a 
result = 55 for the thin ebonite disc. Unfortunately it was 
omitted to make a comparison with these two discs for the gas- 
effect ; nevertheless these results are all in favour of the residual 
effect being a surface-effect. 
Our conclusion from the evidence before us is, that the resi- 
dual effect is a surface-effect more deeply seated than the gas- 
effect, but distributed outwards from the centre to the circum- 
ference, very much in the same manner as the gas-effect. The 
residual effect likewise appears able to penetrate a chamois 
leather blind without any perceptible diminution. We regard 
these conclusions as preliminary, and shall endeavour in our 
future experiments to procure additional evidence of these pro- 
perties of the residual effect, as well as to obtain new facts 
regarding it. In the meantime, as the subject is one of interest, | 
and has been already too long delayed, we have not hesitated to | 
bring these results before the notice of the Royal Society, } 
Geological Society, June 11.—Prof. Ramsay, F.R.S., vice- 
president, in the chair.—The following communications were 
read :—*‘ On the nature and probable origin of the superficial 
deposits in the valleys and deserts of Central Persia,” by 
W. T. Blanford. The general results may be summed up 
as follows :—Persia has undergone a gradual change from a 
moister to a drier climate simultaneously with the elevation ot 
portions of its surface, resulting first in the conversion of old — 
river-valleys into enclosed basins containing large lakes, pro- 
bably brackish or salt, Then, as the rainfall diminished, the 
lakes gradually dried up, leaving desert plains. The amount of 
subaérial disintegration among the rocks of the high ground he 
considered to be in excess of the force available for its removal, 
the water which now falls only sufficing to wash the loosened _ 
materials from the steeper slopes into the valieys, and hence the 
valleys in the upper parts are gradually being filled up with 
coarse gravel-like detritus, just as their lower portions have been ~ 
already hidden beneath lake-deposits —*‘On Caryophyllia Bre- 
dai (Milne-Edwards and Haime) from the Red Crag of Wood- 
bridge.” by Prof. P. Martin Duncan, F.R.S, The author 1e- 
corded the occurrence in the Red Crag of the Woodbridge dis- 
trict of a variety of Caryophyllia Bredai (Milne-Edwards and 
Haime).—‘ On the Cephalopoda-bed and the Ooolite Sands of 
Dorset and part of Somerset,” by James Buckman, F.L.S. 
From an investigation of the Cephalopoda-bed in quarries at 
Bradford Abbas in Dorsetshire, the author comes to the con- 
clusion that it is quite distinct from the Cephalopoda-bed of 
Gloucestershire, and that it is the representative oi the Rubbly 
Oolite at the top of Leckhampton Hul and Cold Comfort, and 
of the Gryphite and Z?yigonza-beds of the neighbourhood of 
Cheltenham. The Gloucestershire Cephalopoda-bed he regards 
as situated close to the bottom of the Interior Ooolite series ; 
and this is also the position to which he refers the sandy beds 
above mentioned.—‘‘ Cetarthrosaurus Walkeri (Seeley), an 
Ichthyosaurian from the Cambridge Upper Greensand,” by H. 
G. Seeley, F.L.S. In this paper the author described a small 
Ichthyosaurian femur, discovered by Mr. J. F. Walker in the 
Upper Greensand of Cambridge. He noticed the general cha- 
racteristics of the femur in Ichihyosaurians, and pointed out, as 
the chief peculiarities of the boue that he was describing, the 
subovate form of its head, and the presence of large flawened 
lateral trochanters, which, if of equal dimensions on both sides 
of the bone, would have made its greatest transverse measure- 
ment greater than its length. Upon this bone he proposed to 
found new a genus, Cetarthrosaurus. 
Royal Astronomical Society, June 13.—Prof. Cayley, 
F.R.S., president, in the chair.—S. J. Lambert, of Newton 
Observatory, Auckland, was elected.a Fellow of the Society.— 
The Rev. J. Vale Mummery presented a large photographic 
portrait of Mrs. Somerville. He said that the Society had long 
been possessed of a portrait of Miss Caroline Herschel, and he 
was glad now to be the means of finding her so fitting a com- 
panion. Mrs. Somerville and Miss Herschel had been admitied 
as honorary members of the Society on the same evening in ~ 
1834. They had long been separated, first by distance and then 
