216 
ISLAND LIFE. 
[part I. 
present rate of denudation and deposition, is only 28,000,000 
years. 1 
The Rate of Geological Change probably greater in very remote 
times . — The opinion that denudation and deposition went on 
more rapidly in early times owing to the frequent occurrence of 
vast convulsions and cataclysms was strenuously opposed by Sir 
Charles Lyell, who so well showed that causes of the very same 
nature as those now in action were sufficient to account for all 
the phenomena presented by the rocks throughout the whole 
series of geological formations. But while upholding the 
soundness of the views of the “ uniformitarians ” as opposed to the 
“ convulsionists,” we must yet admit that there is ^reason for 
believing in a gradually increasing intensity of all telluric 
action as we go back into past time. This subject has been well 
treated by Mr. W. J. Sollas, 2 who shows that, if, as all physicists 
maintain, the sun gave out perceptibly more heat in past ages 
than now, this alone would cause an increase in almost all the 
forces that have brought about geological phenomena. With 
greater heat there would be a more extensive aqueous atmo- 
sphere, and a greater difference between equatorial and polar 
temperatures ; hence more violent winds, heavier rains and snows, 
and more powerful oceanic currents, all producing more rapid 
denudation. At the same time, the internal heat of the earth 
being greater, it would be cooling more rapidly, and thus the 
forces of contraction — which cause the upheaving of mountains, 
the eruption of volcanoes, and the subsidence of extensive 
areas — would be more powerful and would still further aid the 
process of denudation. Yet again, the earth’s rotation was 
certainly more rapid in very remote times, and this would cause 
more impetuous tides and still further add to the denuding 
1 From the same data Professor Haughton estimates a minimum of 
200 million years for the duration of geological time; but he arrives at 
this conclusion by supposing the products of denudation to be uniformly 
spread over the whole sea-bottom instead of over a narrow belt near the 
coasts, a supposition entirely opposed to all the known facts, and w T hich 
had been shown by Dr. Croll, five years previously, to be altogether erro- 
neous. (See Nature , Vol. XVIII., p. 268, where Professor Haughton’s 
paper is given as read before the Royal Society.) 
3 See Geological Magazine for 1877, p. 1. 
