-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 — 



i?M 2 



5 (433200, 2 (5280) 2 

 for a contraction of 1 foot, we should have 

 3 



M 



fr 



5 V 1 (433200) (5280) (433200)5280/ 



i.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 seons 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 palseontological evidence for the high development and wide 

 dispersal of organisms, at least in later palaeozoic 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. 



