316 A. Vaughan — Critique on Results of a Shrinking Globe 



For here we arrive at a point to whicli, as I have shown above, the 

 method of analysis cannot rigidly apply, not only on account of 

 the physical discontinuity of surface rocks, but also on account of 

 the irregular distribution of the large land and ocean areas which 

 renders a shell at the depth of two or three miles a purely theoretical 

 conception. 



In fine I adhere to the conception^ so fully explained in the 

 beginning of my paper, that, owing to the existence of separation 

 planes, this imaginary shell of compression settles down upon the 

 interior rocks ; so that in reality we are dealing with a vast series 

 of shells, contracting upon and consequently squeezing each other, 

 surrounded by a thin layer of surface rocks, which settles down upon 

 thera by closer application. 



Before criticizing the theory put forward by Mr. Reade, I should 

 like to point out the questionable strength of his disproof of the 

 older theory. 



Assuming that contraction has only affected a shell about 150 

 miles in thickness, he supposed this shell to have lost an average 

 of 1000° F. since Cambrian times, and proceeds to calculate its 

 radial contraction. 



To quote his own words :^- 



" The linear contraction of 150 miles of rock cooled 1000°, using 

 this coeificient, would be 4,125 feet, but, as the contraction of the 

 shell 150 miles deep is volurainal, the contraction in thickness of 

 the shell would be three times this, or 12,375 feet or=2'344 miles." 



I fail to see how the contraction in thickness, i.e. the contraction 

 of a certain line of material, can by any possibility be voluminal. 

 Bat, accepting this result for the sake of argument, Mr. Eeade 

 finds that the girth of the interior shrinking sphere would be 15 

 miles less than that of the thin imaginary outer shell of compression ; 

 so that this represents, so to speak, the amount of looseness which 

 has been used up in mountain-making since Cambrian times. 



Here Mr. Reade leaves this part of his argument, but if we apply 

 the above result we shall find that the elevation which could thus 

 be produced is a very large one indeed. For suppose, to take a 

 case far from the maximum possible, that the extra length of 15 miles 

 in each great circle is used up in forming a cone tangential to the 

 interior sphere. We should thus be able to form a mountain covering 

 nearly a million square miles and rising to a height of 60 miles 

 above the surface of the sphere. But, as Mr. Reade says, his 

 assumptions are generous in the extreme, and I feel sure that, as 

 referred to above, he has gratuitously multiplied them by three. 



In the very simple calculation presented early in this paper, I 

 took a coefficient not diifering much from the one adopted by Mr. 

 Eeade, and made allowance for a loss of 10° C, which I believe 

 would more than cover any one period of mountain-making. By 

 this line of reasoning we seem to obtain a better means of com- 

 parison with actually known facts than if we estimate the total 

 available volume which the old theory would allow for mountain- 

 making since Cambrian times, and then attempt to compare it 



