Correspondence—Mr. T. Mellard Reade. al 
to say, that some of the very best workers have been, and are, the 
very men whose conclusions I venture to question or dispute. At all 
events, I have thought it a more profitable theme to dwell on the 
immense extent of our remaining ignorance, rather than on the little 
area over which our knowledge has been securely established—on the 
difficult, and, as it seems, the almost insoluble problems which lie 
before us, and are pressing close around us, especially those which are 
involved in the very last and the very latest changes which have taken 
place on the surface of our globe.—The ‘‘ Scotsman,” Noy. 2nd, 1883. 
C@i Ea S12] @ aN ew enn S mene 
MR. MELLARD READE’S REPLY TO MR. WALLACE ON THE 
AGE OF THE EARTH. 
Str,—In replying to Mr. Wallace’s letter in the October Number 
of the Grotocican Magazrinn, I shall only refer to those points that 
J think really touch the question in dispute between us. Fortunately 
the issue is considerably narrowed by certain admissions which I will 
proceed to notice.! But before doing so I may perhaps be permitted 
to say that the letter is full of misconceptions and extraneous matter 
that have no bearing on and are no elements in the calculation. 
Mr. Waliace states that his 3 million of square miles 177,200 feet 
thick represents the matter which actually exists on the globe in the 
form of stratified deposits, which he estimates took 28 millions of 
years in accumulating, using as his measure the present rate of 
denudation. Also that this deposit equals a stratified crust of from 
9,000 to 10,000 feet thick, if spread over the whole of the existing 
land. So far, this is satisfactory and explicit. There is, however, 
this fundamental omission in his calculation and reasoning. He does 
not allow for the material having been worked up again and again to 
form this actually existing deposit. By the average number of times 
these particles of rock have been re-used, by so much—even if we 
assume the other elements to be correct—is Mr. Wallace’s calculation 
in error. Hvery geologist knows that nearly all stratified rocks are 
more or less made up of the ruins of pre-existing stratified rocks, and 
the question to be answered is, how often have the particles been so 
re-used ? If, as I estimate, the materials have on an average been 
re-used twelve times, then Mr. Wallace’s result would have to be 
multiplied by 12, or instead of 28 millions as he estimates, the Harth 
would be 356 millions of years old. 
My mode of arriving at a rough approximation of the number of 
times the materials of the sedimentary rocks have been re-used, 
though “incomprehensible ” to Mr. Wallace, is really a very simple 
process, and until Mr. Wallace or some one else points out a better 
way, I suppose I may be permitted to use it. It is this. Stratified 
deposits if only derived from stratified deposits would make the age 
of the earth infinite. This would hardly suit Mr. Wallace. From 
1 In making these ‘‘corrections” it is evident that the origin of Mr. Wallace’s 
difficulties is that he does not realize fully the conditions of the problem he set himself 
to solve. 
