C. Lloyd Morgan — Geological Time. 155 



too great and equally unwise excess, before te settles down into the 

 steady earnestness of sober manhood, so did geologists, when they 

 had freed themselves from the restraint imposed upon them by a 

 belief in the truth of the Mosaic account of Creation, make too 

 great drafts on the bank of Geological Time. " In the economy of 

 the world," said Hutton, " I can find no traces of a beginning, no 

 prospect of an end." Geological Time was considered illimitable, 

 and a false analogy was set up between the boundless infinity of 

 space and the vast immensity of past time. Geologists began to 

 speak of millions of years as mere moments in the antiquity of the 

 earth's history. Thousands of millions, billions, and " vast oeons " 

 of past time were spoken of with impunity. This error, for we 

 shall shortly see that it was an error, arose partly no doubt from our 

 utter inability to conceive periods of time which greatly exceed in 

 length the three or four thousand years with which the history of 

 nations has to deal. Directly we cease to have a clear mental image 

 of the length of time spoken of, and can no longer refer it to any 

 standard, we get into the region of mere empty words which mean 

 nothing. "A million of years" — it is easily said, but really conveys 

 very little to the mind. Mr. Croll, feeling the truth of this, helps 

 us to conceive this immense period of time. " There is one way," 

 he says, '•' of conveying to the mind some idea of what a million of 

 years really is. Take a narrow strip of paper, an inch broad, or more, 

 and eighty-three feet four inches in length, and stretch it along the 

 wall of a large hall, or round the walls of an apartment somewhat 

 over twenty feet square. Eecall to memory the days of your boy- 

 hood, so as to get an adequate conception of what a period of a 

 hundred years is. Then mark off from one of the ends of the strip 

 one-tenth of an inch. The one-tenth of a inch will then represent 

 one hundred years, and the entire length of the strip a million of 

 years. It is well worth making the experiment," Mr. Croll adds, 

 "just in order to feel the striking impression that it produces on the 

 mind." 



Having grasped in some degree the vast period of time conveyed 

 by that little phrase "a million of years," the geologist is in a better 

 position to hear patiently the arguments brought forward by pliysi- 

 cists for the definite limitation of that time, which the School of 

 Uniformity had taught him to consider as indefinite in length. Of 

 those who have made this subject their special study. Sir William 

 Thomson takes the Iftad, and he has considered the matter from 

 more than one point of view. 



I will here extract a short description of his'results from Professor 

 P. Guthrie Tait's " Eecent Advances in Physical Science," in which 

 there is a brief resume which "contains nearly all that is accurately 

 and definitely acquired to science upon the subject." In the first 

 place, then. Sir William Thomson takes into careful consideration 

 the facts connected with the internal temperature of the earth. It 

 is a matter of every-day experience that there is a gradual increase 

 of temperature as we descend into the earth's crust. But " when- 

 ever a body is hotter at one part than at another, the tendency of 



