Chemistry and Physics. 495 
Measurement of low sa: nat — M. Wrosrewsx1 has 
Gimpaled the indications of a h en thermometer and a ther- 
mal eciaticy The hydrogen haaaei indicates, below —193° 
iy ae 
the laws of Mariotte and Gay-Lussac demand. This sapere 
td with the depth of temperature. Thus the hydro 
thermometer gives for the temperature of solidification of oxide of 
carbon and azote —207° C, and —214° C, The thermal apnokee 
gave —199° ©. and —203°C, The regularity of the thermo- 
electric curve shows that the thermal junction gives more reliable 
aulicehaes than the air net EEN at very “low temperatures, 
When oxygen, azote, and oxide of carbon are evaporated in a 
Seana the temperature falls. ool a few degrees below —200° 
he author also maintains that the lea of saa ths, of atmos- 
pheric air is not that of a simple gas; but acts like a mixture of 
which the components have atone’ laws of ea — Comp= 
tes gy ones. Ave! 13, 1885, p. 9 = he 
New property of Telicn sa ge NER SIEMENS has exam- 
imed the new selenium cells made b Mr. Fritts, of New York, 
and states that they possess great sensitiveness to rays of light of 
certain refrangibili ay. These cells consist of a thin homogeneous 
layer of selenium spread on a aris late. This layer is heated 
to convert it from amorphous to crystalline selenium, and is then 
se ie with fine gold leaf. One of the plates examined by Sie- 
was not sensitive to light; when, however, a galvanometer 
an intercalated between the gold leaf and the base plate, the 
existence of an electrical current was detected. ‘The difference of 
potential was apparently proportional to the light, and it remained 
during the illumination. The infra-red rays did not produce this 
difference of potential. This eects force increased from 
9.30 A.M, to 11.35 A. M.; remained constant for some time, and 
en decreased to 3 P. M. eA der Akad. der asia 
u Berlin, Feb: 12, 1885. 
5. On the depth in the sea to which light Peaticnes Jia, i. 
Lox and Ep. Sarasin, who have studied the absorption of light 
by the water of 5 a Geneva, have extended their researches to 
the water of the Mediterranean. The photographic plates, which 
were lowered to different depths, were protected from the action 
of salt water by a bituminous varnish, which was removed by 
elo 
