424 Scientific Proceedings, Royal Dublin Society. 
This gives, by integration, 
Ae a goalie a 
a 2s Se = ay 
From this equation, we find, substituting the proper values (as 
above given for 8, a, 6') the following relative lengths of time— 
1°, Present time to Miocene time . A : 41°7 
2°. Miocene time to Jurassic time . 5 a 21°1 
3°. Jurassic time to time of albumen coagulation 37:2 
1000 
These numbers are written down to the scale, on which 100 
represents the whole duration of organic life, from the present 
time to the time of coagulation of albumen at 80° N. Lat. 
From the foregoing results the following conclusion may be 
deduced— 
That the tume elapsed from Miocene tumes to the present time, is 
41°7 per cent. of the whole time of the existence of life on the 
globe. 
(B.) Earth-Heat regarded as the sole cause of changes in Geologi- 
cal climates. 
It is easy to show that Earth-heat has been always, probably 
not a very important factor in Geological climates. We may 
demonstrate this statement as follows—It has been just shown, 
that if atmospheric conditions were the same as at present, the 
quantities of heat, at 80° N. lat., required to keep up the neces- 
sary radiation, at various Geological times, would be— 
Present time “ ; 41:90 melted feet of ice. 
Miocene time . : 61:26 5 3 
Jurassic time ; . 75:36 es ms 
Albumen coagulation time . 112-56 
and I have already calculated the amounts of increase of sun- 
heat, sufficient to account for the several climates. 
If the sun-heat had been the same as at present, we have to 
provide heat from some other source (say earth-heat) to account 
