Capt. F, W. Hutton — On the Formation of Mountains. 27 



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 fifty millions of years ago,^ and it is as reasonable a sup- 

 position as can be made that, of the other fifty millions of years, 

 thirty-nine were occupied by the rest of the Palasozoic era, nine by 

 the Mesozoic era, and two by the Cainozoic era. ^ So that if we suppose 

 the present surface-features to have originated in the Triassic period, 

 it follows that 11 millions of years is the oldest date that can be 

 assigned to any of them. This, according to Fourrier's estimate of 

 the rate of cooling of the earth, is only sufficient time to allow it to 

 decrease 3f° P., 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, as Mr. Fisher 

 supposes, the surface of the earth has contracted one mile in a 

 hundred since the present surface-features originated, and the cir- 

 cumference is now 24,856 miles, it must at the time supposed have 

 been 25,104 miles in circumference ; and the radius, which is now 

 3956 miles, must then have been 3995 miles ; so that it must have 

 shrunk 39 miles. This in 11 millions of years would be 11-9 yards 

 in 2000 years, or since the time during which we have astronomical 

 observations. 



9. If, however, we allow, for the sake of argument, all Mr. Fisher 

 asks, namely, that a mountain half a mile high might be formed on 

 every 100 miles since the present surface-features originated, we 

 then find that, taking the date of the surface as before, Mr. Fisher's 

 mountain has taken eleven millions of years to rise 2640 feet ; or it 

 has risen only one foot in 4166 years, which is less than the rapidity 

 of denudation. Mr. Fisher, therefore, is in this dilemma: either 

 the contraction of the earth has been so rapid that it ought to have 

 been noticed by astronomers ; or the elevation of land has been so 

 slow that it could not rise above the ocean. 



10. Another important objection to the Contraction theory is that 

 mountains have always been formed in those places where deposits 

 have been heaviest, while by that theory those areas should never 

 rise at all. Mr. Fisher says that " the local pressure caused by a 

 fresh deposit . . . will originate a line of elevation along its shore 

 line or boundary," and also " the thickness of the rigid crust being 

 increased by the new deposit, it would offer an impediment to the 



1 Mr. A. "Wallace, on quite independent grounds, puts it at twenty- four millions 

 for the Cambrian, and fourteen millions for the Triassic period. (Nature, i. p. 454, 

 3rd March, 1870.) 



^ These proportions are taken from the thickness of the various formations in the 

 Northern Hemisphere. In New Zealand the geology is not yet suiiiciently advanced 

 to enable us to ascertain the thickness of the formations ; but I am of opinion that 

 the proportions between them will be found to be not very different from those that 

 obtain in England. 



3 According to Sir W. Thomson's theory, eleven million of years ago the interior 

 temperature increased at the rate of V F. in 47 feet, so that the radiation was very 

 little more than it is now. 



