228 Scientific Intelligence. 
was opened, and marked then the desired pressure. This pressure 
was now determined by connecting a mercury manometer with 
the oil. 
compression of the gas was effected by a column of mer- 
cary rising ge grote in a large tube, which formed the prolongation 
of t eck of the flask in which the gas was ——— ores 
ries of oo the seaabost deviation from the mean was 
only a tenth of a millimeter. 
y studying the oe motion of the manometer after the 
compression it was found t a slight correction could be applied 
for the lowering of the rape 2 of the gas during compression. 
C 
Without the correction, for atmospheric air hl, and ap- 
’ 
plying the correction 1397. 
alent of heat the number 434, which differs only by a single unit 
from that rouile Sound by M. Violle with Foucault’s pate atus. 
An experiment with carbonic acid gave the results — = 1'299; 
an accident happening to the apparatus interrupting the study of 
this gas. There is reason to believe that this result is a little too 
great; moreover the gas was not entirely free from air.— Comp 
Rendus, Ixxvil, 1325. E. ©. P. 
elative intensity of the constituent rays of various sources 
of light.—M. Trannin describes a form of photometer for com 
paring the intensity of the various simple colors of which every 
light is composed. It consists 
(1.) Of two small vightangled prisms, placed one — the 
other and turned in opposite directions, so as to receiv e the ray® 
The an then enters a collimater by which it is rende 4 
el, next a polarizer whose principal section is vertical, a 
then a nee of sett about a centimeter Sesser. cut ese with | to t : 
ouble image rism 
(. ) The tin ntl as telescope of a spectroscope finally 
receive the luminous rays. 
