﻿TF. J. SoUas — On Evolution in Geology. 7 



The Laurentian strata were clearly never exposed to a temperature 

 like this, but it is quite conceivable that their wide-spread and 

 extreme state of metamorphosis may be connected with the early 

 date of their origin. 



Elevation and Depression of Strata. — The movements of the earth's 

 crust are generally allowed to be due to the loss of heat from within 

 it, whether by the wrinkling or the crushing of the crust on a con- 

 tracting nucleus, or by any other means. But at the beginning of 

 geologic time the temperature was much more elevated above that 

 of its surrounding medium than at present, and consequently cooling 

 or the loss of heat must have gone on more rapidly than at present, 

 and from this follows a more rapid progress of those movements of 

 upheaval and subsidence depending on this cooling. Thus elevation 

 and depression of strata must have occurred with greater rapidity in 

 the earlier than in the later stages of our planet's history. 



Summary. — We have now shown that the decreasing energy of 

 the sun and of the earth must have led to diminishing rapidity 

 in the action of three of the main factors of geologic change, viz. on 

 the denudation, reproduction, and the elevation and depression of 

 strata. 



In spite of all fluctuation resulting from more than usually rapid 

 conversions of potential into kinetic energy, the loss of energy 

 continually proceeds, and as continually is accompanied by a 

 decrease in the rate of geologic change, just as certainly as the 

 greater periodical activity in the solar radiation once every 11 -2 

 years gives rise to exactly opposite results. 



If then denudation and deposition take place with accelerated 

 velocity as we recede from the present time, how great is the 

 mistake of attempting to check the results as to the age of the world 

 obtained by the physicist with those deduced by the geologist, as 

 though the methods of both were independent of each other, while 

 all the time the latter proceeds upon the assumption that the rate of 

 geologic change has on the whole been always constant, and the 

 former disproves this in a corrollary to his chief argument. To 

 adapt an analogy of Prof. Stuart's, one is told that a certain boy 

 grows iVth inch in a year, and that he is four feet high; the 

 geologist then argues ten years to grow 1 inch, 480 years for four 

 feet, therefore the boy is 480 years old. On a person who knows 

 more about the boy in question coming forward to inform us that 

 when he was younger he grew much faster, and that after all his 

 age is only ten years, the geologist replies. It may be so, let me 

 see, -roth of an inch in a year, on the doctrine of uniformity, 1 inch 

 in 10 years; no, you are clearly mistaken, 10 years is far too short 

 a time, the organic processes of growth could not possibly have 

 occurred in this time. I grant you my own calculation is not 

 rigorously exact ; let us say then our boy is but 400 years of 

 age. - 



Is this an unjust parallel? 



