288 Transactions.— Geology. 
5. The theory also entirely fails to account for strata being elevated with- 
out disturbance, unless we Suppose such an amount of horizontal slipping of 
one bed over another as is manifestly impossible. 
6. If, however, as appears to me certain, the rocks must crush and rise 
tolerably uniformly, it is evident that the theory is quite inadequate to account 
for mountains ; for, the contraction being universal, and the sea occupying the 
outer surface of the earth, the sea would rise more than the land, and the result 
would be that after the contraction the sea would stand higher above the land 
than it did before. In other words, the land would be said to have been 
depressed instead of having been elevated. If, therefore, we consider the earth 
when the crust was first formed, and it was surrounded by a universal ocean, 
we see that no land could rise above the water from contraction, but that, on 
the contrary, the ocean would gradually deepen. It was these considerations 
that led me to suppose that the first deposits were of organic origin, and that 
it was these deposits that first raised land above the water. 
7. Mr. Fisher assumes, without giving any reasons, that since the date of 
the present surface features of the earth, a shell, 500 miles in thickness, has 
contracted as much as rock would do in passing from a fused to a devitrified 
state. But is this a reasonable assumption? I think not. It is certainly 
quite as reasonable to suppose, with Sir W. Thomson, that it is 100 millions 
of years since the crust of the earth cooled ; and if we suppose that the oldest 
Laurentian rocks date from this period (which is the most favourable 
supposition that can be made for Mr. Fisher), then the Cambrian period will 
probably date about 50 millions of years ago ; and, taking the thickness of 
formations as our guide, it is as reasonable a supposition as can be made that 
of the other 50 millions of years 39 were occupied by the rest of the paleozoic 
era, 9 by the mesozoie era, and 2 by the cainozoie era. So that, if we suppose 
the present features of the earth to have originated in the triassic period, it 
follows that 11 millions of years is the oldest date than can be assigned to any 
of them. This, by Fourrier's calculations of the rate of cooling of the earth— 
allowing for the slight increase of radiation in former times—is only sufficient 
to allow it to decrease 4° F. in temperature ; and if we suppose that the whole 
of this heat was abstracted from the shell 500 miles in thickness underlying 
the crust, its temperature would be reduced by only 12° F., which is not 
nearly enough to give the amount of contraction supposed by Mr. Fisher. 
8. We can look at this question in another way. If the surface of the 
earth has contracted, as Mr. Fisher supposes, one mile in a hundred since the 
present surface features originated, and the circumference is now 24,856 
miles, it must at the time supposed have been 25,104 miles in circumference, 
and the radius, which is now 3,956 miles, must then have been 3,995 miles, 
80 that it must have shrunk 39 miles, "This in 11 millions of years would be 
