March 2,1 882] 
_same part of its surface whatever angle it is placed at, ani thus | 
the power of an electric light can be accurately given for every 
angle along which the ray travels from the lamp. Observations 
are taken through red and green glasses to get a better measure 
of the power of the light. Prof. Ayrton has found that ordinary 
_air absorbs the green rays of the electric light very strongly, and 
hence, in order to get a proper test of an electric lamp, the 
photometer should not be far from the light. The new disper- 
sion photometer shown is the only one admitting of this precau- 
tion. Mr. Shoolbred stated that he had found from experiment 
that the carbons of the Swan and Maxim incande cent lamps 
bore a much higher current without breaking when fed from a 
Faure accumulator than from a dynamo;electric machine. Prof. 
‘Ayrton corroborated this statement, and said that he had ob- 
tained a lizht of $00 candles from a Maxim lamp fed -by an 
accumulator.-—Prof. Sylvanus Thompson then read a paper on 
the electric resistance of carbon under pressure. It was generally 
stated that the resistance of carbon diminished under pressure, 
but he had found from recent experiments that the diminution 
observed was really due to the contact between the electrodes 
and the carbon, Under pressure there are more points of 
contact between the metal and carbon than without pres- 
sure. The result has an important bearing on the action of 
the carbon relay, rheostat, and microphone transmitter.—Prof. 
Ayrton pointed out that as carbon apparently diminished in 
resistance under a rise of temperature, this would seem to indi- 
cate it as a compound substance, since only simple substances 
seemed to increase in resistance with rise of temperature. Prof. 
Guthrie recalled that Dr. Moser had suggested that the alteration 
of the resistance of selenium under light was an effect of contact.— 
A paper by Mr. G, Gore was read, on the influence of the form of 
conductors on electric conductive resistance. His experiments 
were designed to show whether there wasa difference of resistance 
‘in certain liquid conductors under the positive and negativecurrent. 
None was discovered.—Dr. Hopkinson, F.R.S., read a paper 
on the refractive index and specific inductive capacity of trans- 
parent insulating media. He inferred from tried experiments 
and the electromagnetic theory that glass had a high refractive 
index for rays of very long wave-length. Dr. J. H. Gladstone 
“suggested that the point should be tested by experiment, and 
that the method of photographing the red rays might be em- 
ployed.—Mr. J. Mactarlane Gray explained that an objection to 
one result of his former communication to the Society, on the 
specific heat of steam, was really a confirmation of it, as 
Regnault’s value was erroneous. 
Chemical Society, February 16.—Prof. Roscoe, president, 
in the chair.—During the evening it was announced that the 
Council proposed Dr. Gilbert as the president for the coming 
year, Dr. Schunck and Mr. Griess as vice-presidents, and Drs, 
Atkinson and Japp, Capt. Abney, and Mr. O’Sullivan, as 
Members of Council, instead of Dr. Tidy and Messrs. Carteighe, 
Roberts, and Warington.—The following papers were read :— 
On benzylphenol and its: derivatives, Part 2, by E. Rennie. 
The author has obtained and studied the following derivatives :— 
benzylphenol-sulphonic acid, mononitrobenzylphenol, amido- 
benzylphenol, dinitrobenzylphenol, nitrobromobenzylphenol. The 
same nitrobromo derivative is obtained whether nitric acid acts 
‘on the potassium bromosu!phonate or bromine acts on the 
potassium nitrosulphonate. The formulz of these substances 
must therefore be symmetrical. Benzylphenol is therefore a 
para derivative. The author quotes other evidence in support of 
this view.—On the Buxton thermal water, by J. C. Thresh. The 
author has made a most complete analysis of this water, and 
gives full details as to the methods employed.—On retrograde 
phosphates, by F. J. Lloyd. It has been long known that in 
some superphosphates the percentage of soluble phosphate 
originally present gradually decreases. The phosphate which 
has become insoluble is termed retrograde phosphate. The 
author has compared the different solutions recommended by 
Fresenius, Petermann, &c., for extracting these phosphates ; he 
concludes that a cold ammoniacal solution of ammonium citrate 
containing 30 per cent. of citric acid is the most suitable solvent. 
—Contributions to the knowlecge of the composition of alloys 
and metal work, for the most part ancient, by W. Flight. This 
paper contains analyses of some copper nickel coins of Bactria ; 
some coins of ancient India, about 500 B.c., containing silver, 
copper, lead, &c. ; a figure of Buddha, containing 4 per cent. of 
silver chloride ; ‘‘ Bidrai” ware and ‘‘Koft Gari” work from 
India; some iron and bronze implements from the Great 
Pyramid; copper spear-heads from Cyprus ; a Hebrew shekel, 
NATURE 
427 
various old Roman bronzes, &c.—On the dissociation of chlorine, 
by A. P. Smith and W. B, Lowe. The authors consider that 
their experiments prove that 1 gramme of chlorine at 6° C, 
becomes 0°744 grim. of chlorine at 1030° C, 
Meteorological Society, February 15.—Mr. J. K. Laughton, 
M.A., F.R.A.S., president, in the chair,—The following gentle- 
men were balloted for and duly elected Fellows of the Society :— 
W. Aronsberg, J.P., W. G. Birchby, J. Rand Capron, F.R.A.S., 
P. Crowley, F.Z.S., W. W. Culcheth, M.Inst.C.E., D. Cun- 
ningham, M.Inst.C.E., F.S.S., S. Cushing, W. N. Greenwood, 
E. Kitto, J. Mansergh, M.Inst.C.E., G. Oliver, M.D., H. S. H. 
Shaw, Assoc.M.Inst.C.E., G. W. Stevenson, M.Inst.C.E., 
F.G.S., and W. H. Tyndall.—The papers read were :—Notes 
of experiments on the distribution of pressure upon flat surfaces 
perpendicularly exposed to the wind, by C. E. Burton, B.A,, 
F.R.A.S., and R. H. Curtis, F.M.S. In the present state of 
aero-dynamics it seems to be impossible to make ana priori 
investigation of the distribution of pressure on a surface exposed 
to the impact of the fluid in motion without introducing such 
limitations as render the solutions arrived at widely divergent 
from the results obtained by the experiments hitherto made. 
The authors therefore proposed to themselves to attack the 
problem from the experimental side only, by a method which, 
as far as they know, has not been applied in the case of air, viz. 
the application of Pitot’s tube, suitably modified in form to the 
simultaneous measurement of the pressures at the centre and at 
any en-centrically situated point of a pressure plate of known 
dimensions. The results of the preliminary experiments are 
given in the present paper.—The principle of New Zealand 
weather forecasts, by Commander R. A, Edwin, R.N., F.M.S. 
—The high atmospheric pressure of the middle of January, 
1882, by H. Sowerby Wallis, F.M.S.—The electrical thermo- 
meter lent by Messrs, Siemens’ Bros. for observing the tempera- 
ture of the air at the summit of Boston Church Tower was also 
exhibited. 
EDINBURGH 
Royal Society, February 6.—Prof. Balfour, vice-president, 
in the chair.—Mr. John Aitken, in a paper on the Colour of the 
Mediterranean, and other waters, described a series of experi- 
ments which he had made last year as ‘to the cause of the 
brilliant blue colour so characteristic of the Mediterranean and 
the Lake of Geneva. Two distinct theories had been advanced. 
The one explained the colour as due to reflection from small sus- 
pended particles whichdid not reflect the lowerrays of thespectrum; 
the other as the result of the absorbent action of the water itself 
upon the white light before and after reflection from these particles, 
The former was shown to be inconsistent with the facts esta- 
blished by experiment, which could be fully explained upon the 
latter theory. The greater the number of white reflecting 
particles the greener the water appears to be, a fact which 
sufficiently explains the gradual deepening of the green to blue as 
one recedes from the shore. The waters of the Lake of Como 
owe their darkness to the absence of reflecting particles, as Mr. 
Aitken very ingeniously proved by scattering finely divided chalk 
in the centre of the lake, thereby producing a most brilliant 
blue. The brilliancy depends greatly on the colour of the 
suspended particles; and observations in other parts of the 
earth’s surface go far to show that great brilliancy is usually 
found where white sand lines the shore. Thus the dullness of 
tint in our waters is to be referred to the dull colour of the 
small suspended particles. The author had also extended his 
observations to spring water, which was found to vary greatly 
in colour from dingy yellow to emerald blue. The paper 
was illustrated by experiments bearing out the views expressed, 
and led to a considerable discussion amongst the Fellows. 
—The Rey. Prof. Duns, D.D., read a paper on the surface 
geology of Middle Lochaber, giving a description of the 
peat, sand, gravel heaps, angular dééris and boulders, which 
occur between the rivers Spean and Nevis, and along the 
west slopes of the Nevis Mountains. The paper was chiefly 
devoted to the boulders, their mineral character, size, position, 
angle to horizon, and striation being particularly noted. It was 
shown that the peat had been formed after the deposit of the 
sands and gravels, that the boulders occur om not iz the heaps, 
that the position of boulders in the plain may have as much sig- 
nificance as those on mountain slopes, that all the characteristic 
glacial markings abound in this district, and that the bulk of the 
phenomena may ultimately be explained by the recognition of 
two movements—one outwards from Ben Nevis as a centre, and 
another (and preceding) inwards from the west, north-west, 
