CHAP. X 



THE EARTH'S AGE 



223 



miles is deposited. As these two areas are as 1 to 19, it 

 follows that deposition, as measured by maximum thickness, 

 goes on at least nineteen times as fast as denudation — 

 probably very much faster. But the mean rate of denuda- 

 tion over the whole earth is about one foot in three thousand 

 years ; therefore the rate of maximum deposition will be at 

 least 19 feet in the same time ; and as the total maximum 

 thickness of all the stratified rocks of the globe is, according 

 to Professor Haughton, 177,200 feet, the time required to 

 produce this thickness of rock, at the present rate of 

 denudation and deposition, is only 28,000,000 years.^ 



The Bate of Geological Change Prohably Greater in very 

 Remote Times. — The opinion that denudation and deposition 

 went on more rapidly in earlier times owing to the frequent 

 occurrence of vast convulsions and cataclysms was strenu- 

 ously 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 "con- 

 vulsionists," 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,^ 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 atmosphere, and, perhaps, a 

 greater difference between equatorial and polar tempera- 

 tures ; hence more violent winds, heavier rains and snows, 



^ 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 wJiole sea-hottom instead of over a narrow belt near the 

 coasts, a supposition entirely opposed to all the known facts, and which 

 had been shown by Dr. Croll, five years previously, to be altogether erro- 

 neous. _ (See Nature, Yol. XVIII., p. 268, where Professor Haughton's 

 paper is given as read before the Royal Society. ) 



2 See Geological Magazine for 1877, p. 1, 



