Previous Index Next
Page 177
(previous) (Page 000177) (next)
 
RADIATION. 177

faces, the needle points to zero. Let any gas be now per-
mitted to enter the exhausted tube; if the molecules pos-
sess any power of intercepting the calorific waves, the
equilibrium previously existing will be destroyed, the com-
pensating source will triumph, and a deflection of the mag-
netic needle will be the immediate consequence. From the
deflections thus produced by difi'erent gases, we can readily
deduce the relative amounts of wave-motion which their
molecules intercept.

In this way the substances mentioned in the following
table were examined, a small portion only of each being
admitted into the glass tube. The quantity admitted was
just sufficient to depress a column of mercury associated
with the tube one inch; in other words, the gases were
examined at a pressure of one-thirtieth of an atmosphere.
The numbers in the table express the relative amounts of
wave-motion absorbed by the respective gases, the quantity
intercepted by atmospheric air being taken as unity:

Radiation through Gases.
Relative

Name Of gas' absorption.
Air“, ............................ . ....... 1
Oxygen .................................. 1
Nitrogen ................................. 1
Hydrogen ................... -. ............ 1
Carbonic oxide .............. . ............ ’7 50
Carbonic acid ............................ 972
Hydrochloric acid ......................... 1,005
Nitric oxide .............................. 1,590
Nitrous oxide ............................. 1,860
Sulphide of hydrogen ...................... 2,100
Ammonia ................................. 5,460
Olefiant gas .............................. 6,030
Sulphurous acid ........................... 6,480

Every gas in this table is perfectly transparent to light,
that is to say, all waves within the limits ,of the visible

Previous Index Next