On Rossetti’s Law of Cooling. 4.29 
4th. During Paleozoic times the amount of sun-heat required 
to keep up the known surface-temperatures was certainly less 
than I have calculated from No. 3, because of the large quantity 
of carbonic acid then forming a part of the atmosphere. 
5th. During Neozoic times the amount of sun-heat required to 
keep up the known surface-temperatures was probably less than 
I have calculated from No. 3, in consequence of the large quantity 
of aqueous vapour then existing in the atmosphere as compared 
with the present time. 
6th. The so-called Pluvial period and Glacial period were 
probably the result of atmospheric changes caused by a tempo- 
rarily diminished rate of heat-radiation from the sun, causing a 
precipitation of aqueous vapour, followed by an increased radia- 
tion of non-luminous heat into space from the surface of the 
earth. 
