48 PROCEEDINGS OF THE CANADIAN INSTITUTE. 
A decrease in the diameter of the sun of less than 20 miles would 
‘keep up the supply for over 5000 years. The most refined instru- 
ments would not be sufficiently precise to detect so small a variation. 
If on the same hypothesis, the sun’s radius were to become one- 
half what it now is, or the density of the sun eight times its present 
value, which would make its density about the same as that of lead, 
instead of— . 
3p A 
5  (4383200,? (5280)? 
for a contraction of 1 foot, we should have 
3p ( 1 1 
5 4 (433200) (5280) — (433200) = 
z.e., about 433200 x 5280 times as much heat would be generated. 
This would be sufficient to sustain the present rate of radiation 
for 22,000,000 years. Similarly if the mass of the sun were equally 
diffused throughout a sphere having a radius of 276,000,000 miles, 
which is the distance of Neptune from the sun, and were to contract 
till it became uniformly as dense as lead, heat enough would be pro- 
duced to meet the present demand for 44,000,000 years. Further, 
if the solar mass had the same specific heat as water, and were 
raised to a temperature of 28,000°, it would contain a store of heat 
2,000,000 times as great as the present yearly expenditure. 
These figures, curious and instructive in themselves, derive con- 
siderable importance from their bearing on the problems of geological 
time, when taken in connection with the vast zeons considered neces- 
sary by most geologists for the formation of the different strata 
of rocks, and with the still vaster ages claimed by biologists for the 
evolution of the existing and extinct forms of animal life. 
The paleontological evidence for the high development and wide 
dispersal of organisms, at least in later paleozoic times, is complete ; 
and to the existence of a flora and a fauna, such as that indicated 
even in the Cambrian formations, a mild climate is absolutely 
essential. Now though climate is profoundly affected by the pres- 
ence of mountains and large bodies of water, and even more by 
winds and ocean currents, and by the quantities of the variable 
elements in the atmosphere, yet to maintain a mild climate the heat- 
giving power of the sun must have been materially as great as at 
present. 
