128 PROCEEDINGS OF SECTION B. 
oxide of copper, heated in a specially-constructed furnace, 
absorbing and weighing the resulting water and carbon . 
dioxide. 
He employed a train of 28 pieces, and tested all his 
methods on artificial mixtures, factors being found nec 
for the hydrogen and marsh-gas. 
He finds approximately two parts of free hydrogen per 
10,000 by volume, at sea, in the mountains, and in the air 
of Paris. This is equal to 3 of the normal amount of carbon 
dioxide in fresh air. The marsh-gas is insignificant in . 
amount at sea, about 2-10ths of a volume (2°19 per 100,000) 
per 10,000 in the mountains, and about 1-2 per 10,000 in 
the air of Paris. 
The carbon monoxide he finds to be nearly. insignificant i in 
the normal Paris air, but of Benzene vapour and analogous 
eompounds he registers -17 parts per 10,000. 
It has long been known that these substances exist in the 
air. Marsh-gas, often accompanied by hydrogen, comes from 
- decomposing vegetable matters; some fermentations yield a 
large proportron of hydrogen; fire-damp, petroleum gases 
and volcanoes are all well-known sources of hydrogen. 
M. Gautier suggests additional sources of hydrogen, and 
gives an interesting and suggestive analysis of the gases ob- 
tained from a granite, 
C.c. per Kilogramme of Granite. 
(CO,) Carbon dioxide, 272-6. 
(H,S) Hydrogen sulphide, 1-2. 
(C,H,) Acetylene, 12-3. 
(CH, j Marsh-gas, trace. 
(N) Nitrogen rich in argon, 230°5. 
Hydrogen, 53. 
Liveing and Dewar, in their investigation “on the spec- 
trum of the more volatile gases of atmospheric air which are 
not condensed at the temperature of liquid hydrogen,” de 
monstrated the presence of free hydrogen in the air over the 
Royal Institution. I cannot, of course, follow the authors 
throughout their beautiful research on an occasion such as 
this, and shall content myself with a very brief reference. 
After having removed the known gases from the fraction- 
ally-distilled liquid air, they made a laborious attempt to 
identify the spectral lines which the residue exhibited on 
sparking. One direction of their inquiry will be gathered 
from their own words—“ As our mixture of gases probably 
include some of all such gases as pervade interplanetary 
ce 
