T^ 



THE POSITION OF GEOLOGY. 537 



THE POSITION OF GEOLOGY. 



By Peof. JOSEPH PEESTWICH, F- R. S. 



^HE position of geology in this country at the present time, 

 more especially as relates to the later geological periods, is 

 anomalous and possibly without precedent. On one side its ad- 

 vance is barred by the doctrine of uniformity, and on the other 

 side by the teaching of physicists. The former requires that 

 everything should be regulated by a martinet measure of time 

 and change. It asserts that the vast changes on the earth's sur- 

 face, effected during long geological periods, are to be measured 

 hy the rate at which similar hut minor chajiges are effected in the 

 present day, and that the agencies now modifying the surface have 

 been alike, in every respect, in all past time. It is true that no 

 restriction is placed on the extent of the changes, but such pro- 

 longed time is insisted on for their accomplishment as to destroy 

 the value of the concession. Not that time is in itself a difficulty, 

 but a time rate, assumed on very insufficient grounds, is used as 

 a master key, whether or not it fits, to unravel all difficulties. 

 What if it were suggested that the brick-built Pyramid of Hawara 

 had been laid brick by brick by a single workman ? Given time, 

 this would not be beyond the bounds of possibility. But Nature, 

 like the Pharaohs, had greater forces at her command to do the 

 work better and more expeditiously than is admitted by uniformi- 

 tarians. 



, On the other side, physicists would lead us to suppose that 

 those great movements of the earth's crust, with which we are all 

 familiar in the form of high mountain and continental upheavals 

 in the earlier stages of the earth's history, were impossible in 

 those times which more immediately approached our own. They 

 maintain that if the earth is not solid throughout, its outer crust 

 at least must have now attained a thickness estimated to vary 

 from eight hundred to twenty-five hundred miles, and is so rigid 

 that we are forced to believe that for a long preceding period it 

 must have been in a state of comparatively stable equilibrium. 

 This, however, would have rendered the great earth movements, 

 considered by geologists to have continued up to the threshold of 

 our own times, impossible. And to this finding the physicists 

 would have geological speculations conform. At the same time, 

 judging, among other reasons, from the rate of cooling of hot 

 solid bodies, they would assign a much shorter term to the earth's 

 history since it became habitable than is compatible with the views 

 of the uniform itarian school of geologists. The one side counts 

 in round numbers upon some three hundred million years; the 

 other sees no reason to go beyond fifteen to twenty million years 



TOL, XXIT. 41 



