W. J. So/las — On Evolution in Geology. 
7 
The Laurentian strata were cl early never exposed to a temperature 
like this, but it is quite conceivable that their wide-spread and 
extreme state of metamorpliosis 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 witliin 
it, whether by the w rinkling 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 muck more elevated above that 
of its surround ing medium tkan 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 
upkeaval 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 sliown 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, reproduciion, 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 exactlv 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 
thougk 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 bis chief argument. To 
adapt an analogy of Prof. Stuart’s, one is told that a certain boy 
grows i^-th 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. ün 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, iVth 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? 
