AUGUST 27, 1902] 
NALCO RE 
401 
assumption that the molecular attraction varies inversely as the 
square of the distance from the molecule and does not vary 
with the temperature. This assumption is found to be in agree- 
ment with the experimental data as tested by the equation. It 
is further shown in the paper that the molecular attraction differs 
from the attraction of gravity in being determined primarily by 
the chemical constitution of the molecule and not by its mass. 
In the July number of the American Chemical Journal, 
Messrs. Morse and Frazer give an account of their experiments 
on the preparation of cells for the measurement of high osmotic 
pressures. Osmotic-pressure determinations are well known to 
be attended with considerable difficulties, and the number of 
experimenters who have succeeded in carrying out the measure- 
ment of even low osmotic pressures is comparatively small. 
Specially constructed porous cells made of fine materials, very 
uniformly mixed and hard burned, were employed, and the 
semipermeable membranes were produced in these by electro- 
lysis. The electrical resistance of the membranes so obtained 
varied very considerably, the lowest resistance being about 3000 
ohms and the highest more than 200,000 ohms. From the 
observations made by the authors it appears that high-resistance 
membranes are those which are requisite for successful osmotic- 
pressure measurements, but no certain method of obtaining 
such membranes has been discovered. Experiments were 
carried out with half-normal and normal cane-sugar solutions. 
For the former the osmotic pressure was found to be about 13°5 
atmospheres, and for the latter a lower limit of 31°4 atmo- 
spheres was determined. It is extremely interesting to note 
that this osmotic pressure of more than thirty atmospheres was 
developed within two hours of commencing the experiment, 
and that the membrane within the cell had a resistance of more 
than 200,000 ohms. 
ALTHOUGH the electrochemical equivalent of silver has been 
the subject of several very careful investigations, the results 
obtained by different experimenters indicate that the quantity 
of silver deposited by a given quantity of electricity is depen- 
dent to a certain small extent on the form of voltameter and on 
the conditions under which thisis employed. Messrs. Richards 
and Heimrod (Zectschrift fiir physikalische Chemze, vol. xli. 
Pp- 302) have investigated minutely the cause of these differences, 
and find that the most important disturbing factor in the 
ordinary silver voltameter is the formation of a complex silver 
ion at the anode which diffuses towards the kathode, and by 
its decomposition increases the quantity of silver deposited at 
the kathode. An improved form of silver voltameter is de- 
scribed in which the anode and kathode are separated by a 
porous cell which prevents the diffusion of the anode solution 
to the kathode, and the accuracy of the results obtained by the 
use of this instrument is demonstrated by several series of 
experiments. As a result of this investigation it appears that 
the electrochemical equivalent of silver as determined by Lord 
Rayleigh’s voltameter is at least ‘05 per cent. too high, and 
that the quantity of electricity associated with one gram 
equivalent must now be taken as 95,580 coulombs. 
The additions to the Z ological Society’s Gardens during the 
past week include a Geoffroy’s Cat (Fe/és geoffroii) from Paraguay, 
presented by Dr. Jose Carlos Rodriguez; a Somali Ostrich 
(Struthto molydophanes) from East Africa, presented by Mr. A. 
Marsden ; two Lion Marmosets (Midas rosalia) presented by 
Miss E. M. Unwin ; a Sykes’s Monkey ( Cercopithecus albigularis) 
from East Africa, a Macaque Monkey (Macacus cynomolgus), a 
Roofed Terrapin (Kachuga tectum), a WHamilton’s Terrapin 
(Damonia hamiltonz), four Bungoma River Turtle (Zmyda 
granosa) from India, a Moustache Tamarin (A/édas mystax) 
from the Upper Amazons, four Long-necked Chelodines 
(Chelodina longicollis), two Vulpine Paalangers ( Zichosurus 
vuloecula) from Australia, nine Tigrin? Frogs (Rava figrina) 
NO. 1712. vou. 65] 
from the East Indies, a Californian Toad (Bufo boreas), four 
Pennsylvanian Mud Terrapins (Czvosternon pennsylvanicum) from 
North America, two Blackish Sternotheres (Sternothoerus 
nigricams) from Madagascar, a Lesueur’s Water-Lizard 
(Physignathus lesueurz) from Queensland, two Black-pointed 
Teguexins (Zzpinambis nigropunctatus) from South America, 
deposited ; a Hoolock Gibbon (Hy/obates hoolock) from Assam, 
purchased ; a Crested Porcupine (Ayst7zx cristata) born in the 
Gardens. 
OUR ASTRONOMICAL COLUMN. 
A NEw REGISTERING ACTINOMETER.—M. G. de Fontenoy, 
of Paris, communicates to the Bulletin de la Soctété Astrono- 
migue de France, of August, a description of a novel registering 
actinometer which he has made and has found to act con- 
sistently. 
The record is produced by the sunlight acting on a sensitised 
roll of paper fastened to an inner cylinder in the usual way, but 
in order to differentiate the varying intensities of the actinic 
effect, the light is allowed to act on the sensitised surface through 
a series of small windows, pierced in an outside cylinder of thin 
brass, which are equal in area and equidistant, but have different 
degrees of transparency. The whole instrument is rotated so 
that the common axis of the cylinders is always at right angles 
to the path of the sun’s rays, and the inside cylinder is rotated 
by clockwork once in every twenty-four hours. 
The paper is divided into equal spaces, representing hours, by 
a series of lines drawn on its surface perpendicular to the 
direction of its rotation, and a reproduction of one of the charts 
resulting from the exposure and working during one day in June 
plainly shows the traces made by the light which passed 
through the various windows; the longest trace (z.e. the one 
which is shown for the greatest number of hours) is the one 
which was formed by the light which passed through the most 
transparent window, the shortest is the one due to the light 
which passed through the most opaque window. By joining 
the ends of these traces one gets a curve, the integration of 
which gives the total amount of light registered during the 
twenty-four hours if one has previously determined the actinic 
constant for each window by submitting the instrument to the 
action of a standard light. 
SOLAR PHENOMENA DURING 1I901.—The ‘* Commission 
Solaire” of the Société Astronomique de France has published 
the observations of sun spots and faculze during 190I. | 
Numerous observers scattered all over the globe make 
these observations and then submit them to the commission. 
Observations were made on 357 days during the year 1901, and 
it is hoped that, with the assistance of several recently enlisted 
volunteers, a complete record will be obtained for this and 
future years. : 
During 1901 twelve separate groups of spots, including 392 
individual spots, were observed, the sun presenting a spotted 
surface on sixty days out of the 357 days of observation. 
It is recommended by the secretary, M. F. Bouet, that 
members should also record the barometric pressure, the tem- 
perature, and the state of the surrounding atmosphere at the 
same time that they record the numbers of solar spots and 
faculze. 
A Dark Spor On JupiTer.—In a letter to the Observatory 
Mr. Theodore Phillips describes the movements of the dark 
spot which was observed in the neighbourhood of the red spot 
last year. On June 19 this year it was observed than an 
enormous area of dark material, extending for 35°, followed the 
Ff * shoulder” of the red spot, and on’ June 26 a dark spot was 
observed close to the g “shoulder,” or west, of the red-spot 
hollow. 
Mr. Phillips asks, “‘ How did it arrive at its present position ?” 
and then discusses the various solutions to the question, finally 
arriving at the conclusion that the dark material must have been 
diverted to the south by the red spot, and, after passing that 
obstruction, have regained its former latitude. As there is still 
a portion of the dark area to the east of the red spot, it: would 
be advisable for observers to pay special attention thereto, as 
valuable additions to our knowledge of Jovian phenomena may 
thereby be secured. : 
Mr. Phillips also records an apparent acceleration, of late, in 
the velocity of the red spot. 
