668 Transactions. — Geology. 



thickness of all the " Azoic, PaliBOzoic, and Neozoic rocks 

 amounts to 177,200ft., and, allowing 861'6 years as the time 

 required for the denudation of 1ft. of surface in the several 

 river-basins, at least a hundred and fifty-two million years 

 must have passed of geological tmie down to the close of the 

 Miocene-Tertiary epoch." 



I have purposely prefaced my subject on " Denudation as 

 a Factor of Geological Time " with the views which are held, 

 or have been held, by the leaders of geological thought, as it 

 enables us to see what vast steps have been taken backward, 

 as it were, into the past since the days when men thought 

 that the earth's history dated back some four or five thousand 

 years before the Christian era. But, great as is the factor of 

 denudation in estimating the history of change on the earth's 

 surface, the traces of past life as unfolded in the stratified 

 rocks raise questions for consideration which, as far as our 

 present knowledge goes, can only be settled by assuming long 

 intervals of time, as by no other means— unless special centres 

 of creation are recognised — can it be supposed that animals 

 and plants representing a past highly-differentiated fauna and 

 flora could have dwelt on the earth and have become adapted 

 to conditions such as do not now and could not now exist. 

 And here I would emphasize a fact too often overlooked by 

 naturalists and geologists — viz., that, whilst change has gone 

 on ever since time was, at no two moments are the conditions 

 of existence the same. This is why life is ever-changing and 

 various. We cannot have two plants or two animals alike, 

 for, try how we may, we cannot place them as to origin and 

 treatment under absolutely the same conditions. This is 

 nature's mode of dealing with matter. To change is to live, 

 and could we learn the art of changing our physical nature — 

 that is, of constantly adapting ourselves to environment — the 

 " elixir of life " would be ours, and man's niastery over nature 

 would be complete. But, fortunately for us, nature will still 

 be our master, for no modification, no change, will ever differ- 

 entiate the flesh into spirit or the spirit into flesh ; for, as 

 Marcus Aurelius puts it, — 



What springs from earth dissolves to earth again. 

 And heaven-born tliiugs fly to tht ir native seat. 



When this earth of ours first became solidified, as it must 

 have become in the process of cooling, many years passed by 

 before its temperature was sufficiently cool to enable the 

 watery vapour of the atmosphere to be condensed. Water 

 does not and cannot remain as water, except under special 

 conditions, above a temperature of 100'^ C. or 212° Fahr. It 

 is possible that the vapour enveloped the whole earth to the 

 point of saturation at a temperature much above what is now 

 experienced. My reason for thinking so is that the dimen- 



