THE GEOLOGIST. 
JANUARY 1864. 
ON THE EARTH'S CLIMATE IN ANCIENT TIMES. 
By tue Editor. 
For some time past we have been drawing attention to some of the 
dicta of Geolog}^ wliich appear to liave a less solid foundation than 
they should have to authorize the positive manner in which tliey have 
been enunciated. Similar doubts on some points would appear not 
to be absent from other minds. Mr. Page has just issued a little 
work reviewing the state of the popular doctrines of our science, and 
Mr. Sterry Hunt has appropriated to the explanation of the higher 
Palaeozoic climate Dr. Tyndall's memorable researches on the rela- 
tions of gases and vapours to radiant heat. Heat, from whatever 
source it may proceed, passes tlirough hydrogen, oxygen, and nitrogen 
gases and dri/ air, with nearly the same facility as through a vacuum, 
and these gases are thus to radiant heat what rock-salt is amongst 
solids. Glass and some otlier substances whicli are readily per- 
meable to light and to solar heat, offer, as is well known, great ob- 
stacles to the passage of radiant heat from non-luminous bodies, and 
many vapours and gases have a similar effect in intercepting the heat 
from such sources. Thus, for a vacuum ^he absorption of heat from a 
body at 212° Fahr. is represented by 0, that by dry air as 1, while the 
absorption by an atmosphere of carbonic acid gas is 90 ; by one of 
marsh-gas, 403 ; by olefiant gas, 970; and by ammonia, 1195. de- 
fiant gas at 1 inch tension produces an absorption of 90°, and car- 
bonic acid gas in the same state, an absorption of 5 6. The small 
quantities of ozone present in electrolytic oxygen were found to raise 
VOL. VII. B 
