66 Rev. 0. Fisher — Reply to Capt. Hutton. 



they were heated, and even then the difference would be too sraall 

 to detect." This reads as if I grounded an argument upon ex- 

 periments upon the specific gravities of the rocks ! In considering 

 the conditions of equilibrium of the expanded rocks, it is perfectly 

 true that I have assumed their specific gravity to be altered in the 

 inverse ratio of the volumes, which I suppose no one will deny to 

 be correct in principle. 



I will not follow Captain Hutton into his ''reasons for rejecting 

 the contraction theory" at present; but if, as I hope to do, I pursue 

 the subject further, I will bear them in mind, and I think I shall 

 be able to meet many of them. I trust in the meanwhile that he 

 Avill not be too absolute in his rejection; for it is certain that the 

 earth is a cooling sphere, and consequently must be a contracting 

 one. And if it be a contracting one, the superficial rocks must have 

 been deranged by compression. And when we look at sections, 

 whether in the field, or in diagrams to true scale, we cannot but be 

 astonished at the amount of this compression, which must somehow 

 or another be accounted for; and the "deposition" theory may claim 

 attention as one partial mode of doing this. Nor need yve be very 

 much alarmed by such considerations as are advanced under Captain 

 Hutton's eighth head. For a rate of shrinking in the earth's radius 

 of 2\ feet in a century, which is about 17 yards in 2000 years, would 

 diminish the length of the day during six thousand years by only 

 3-5ths of a second of time.^ 



I should much like to see a diagram showing a range of moun- 

 tains formed on Captain Hutton's theory. I dare not attempt to ofier 

 one mj'self, for it would either be too unlike any ordinary mountain 

 section, or else I should lay myself open to the rejoinder that I have 

 entirely misunderstood the question. I say this because I think 

 that continuous domes, such as Captain Hutton relies upon for the 

 elevations given in his table, are quite exceptional phenomena, if 

 indeed they are to be met with. But my chief objection to his 

 particular theory is, that I cannot see how, on mechanical grounds, 

 the compression which would accrue from the expansion which 

 he supposes would raise a dome at all. 



Finally, I cannot refrain from saying that I believe, in the past 

 history of the earth, there are probably causes to be taken into 

 account, which have not as yet been di'eamt of. And there are facts 

 to be accounted for, which as yet are wholly beyond the reach of our 

 theories. Though every step of reliable knowledge is an advance in 

 the right direction, yet it is highly probable that the goal will never 

 be fully reached by man's finite powers. 



[Errata in Eev. 0. Fisher's paper on the Formation of Mountains, 

 Vol. X. No. 6, p. 258, line 14 from top, for Z (1 + e) x 1, read I x 1. 

 Page 260, note 3 should stand — See a paper on Coral Eeefs by J. C. 

 Ward, in the "Popular Science Eeview" for April, 1873, p. 170.] 



1 Pratt's Figure of the Earth, 4th edition, p. 204. 



