BY THE PRESIDENT. 59 



The marks of former ice action in older formations would of course 

 be more or less obliterated by age and geological changes. It 

 seems to me that the solution of the cause of the fact of our earth 

 having passed through a succession of climates alternately hot and 

 cold must be sought for in the science of Astronomy. Many 

 astronomers do not think that the precession of the equinoxes is 

 enough to account for it. Mr. Croll, in his work ' Climate and 

 Time,' says tlyit he thinks it is. I think it highly probable, 

 judging by analogy, that our sun has a climate — that he has not 

 uniformly the same temperature. Our sun travels round his sun 

 in a stellar year of about twenty-five millions of years. As our 

 earth has changes of temperature in its year, so may the sun have 

 changes of temperature in his year. If our sun's sun is powerful 

 enough to compel the solar system to I'evolve around him, he may 

 be powerful enough to influence our sun, and with him the whole 

 solar system, in other ways. I consider it possible that our sun 

 may have spring, summer, autumn, and winter in a period of 

 about twenty-five millions of years, or at least, that he does not 

 always have the same climate. 1 do not mean to infer that our 

 sun derives light and heat from his sun, as light and heat, for the 

 light from Alcyone is very little, and the heat imperceptible ; but 

 he evidently influences our sun by the force of gravitation, or else 

 it would not revolve round him. And if he can supply the force 

 of gravitation, he can supply other forms of force, which may be 

 utilised by oiu' sun and converted into light and heat. If this 

 theory is true, we might be able to solve that very interesting 

 question, the age of the earth. To use a common phrase, "every 

 schoolboy knows" that if you make a transverse section of an 

 exogenous tree, as an oak, you will find the wood arranged in a 

 series of rings or layers. Now each ring of wood represents a 

 year of growth ; so we have only to count the number of rings 

 and we have the age of the tree. In a precisely similar manner, 

 in order to ascertain the age of the earth, we must make a per- 

 pendicular section of the earth, and count the number of ice ages. 

 Each ice age may represent a solar winter, that is, a year of 

 twenty-five millions of years. Suppose we find evidence of 100 

 glacial periods, we should estimate the age of the earth at about 

 2,500 millions of years. Of course the calculation is only sugges- 

 tive or approximate, for the data of my calculation may be incorrect. 

 Astronomers may find that the sun's year is more, or that it is 

 less than twenty-five millions of years ; or geologists may find 

 evidence of more or of less than 100 glacial periods; or the sun 

 may have two or more cold periods in his year, or he may have 



