BY F. D. POWER, F.G.S. 33 



If the glasses through which I have viewed the works of 

 nature will not allow me to agree with the interpretation that 

 other observers have thought fit to make, I cannot be accused 

 of having drawn on my imagination to obtrude a pet theory 

 upon your notice, for I have endeavoured to give a correct 

 description of matters as they at present are found, and to 

 point out how, by using such forces of nature as are to be 

 seen at work at the present day, such results could be brought 

 about, not forgetting that time is an unlimited factor of 

 nature's that enables her to produce results slowly, yet surely, 

 in the world's laboratory, which man, during his short space of 

 life, can never hope to attain by the same means. 



DISCUSSION. 



Mr. R. M. Johnston, F.L.S., in reply to Mr. Power, said : — 

 Of the many hypotheses advanced at different times to account 

 primarily for the oscillations of the earth's surface it is frankly 

 acknowledged by those who espouse one or other of them that 

 all are open to objections of some kind. 



There are three hypotheses, however, ably supported by 

 celebrated physicists, which severally seem to find greatest 

 favour among geologists, some espousing the one and some 

 the rival hypotheses. These three hypotheses are mutually 

 exclusive, and may be briefly described as — 



1. The contraction or cooling globe theory. 



2. The gradation or surface displacement theory. 



3. Mobility of a hypothetic fluid theory. 



Undoubtedly the first of these has obtained the greater 

 acceptance among geologists, owing mainly to the able 

 advocacy of Robert Mallet ; and although it is admitted that 

 there are serious objections to its acceptance (notably those 

 urged by MellardEead in his " Origin of Mountain Eanges "), 

 it is even now variously modified, the most widely accepted 

 among geologists as furnishing an explanation of the origin 

 of the upheavals and subsidences of the earth's crust. Such 

 is the opinion of Dr. Geikie in his last great work. 



The rival theories, though ably supported, have even 

 greater objections urged against them, and even one of the 

 most formidable opponents of the contraction theory in 

 Australasia, Professor Hutton, cannot urge that it is disproved 

 by the demonstration of the truth of any other hypothesis. 

 In his able address before the A.A.A.S. he states that 

 " During the last fifty years investigation has rather been 

 destructive than constructive, but progress has been made. 

 Formidable obstacles have been removed . . . No doubt the 

 outlook is still foggy, but the horizon is clearing, and we may 



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