248 Rev. 0. Fisher — On the Formation of Mountains. 



altered ash, along its line blocks were falling into it at various 

 angles, and on either side the rock was shattered, and its parts more 

 or less displaced. On seeing this instance, the thought was at once 

 suggested that the blocky nature of the ground was due to rock 

 Assuring and rock weathering, and further examination seemed to 

 lend support to this view. 



If I remember aright, Darwin, in his " Voyage of a Naturalist," 

 describes some singularly stony and blocky ground on hills in the 

 Falkland Islands, to which the Scafell tract would seem, somewhat 

 similar, but the cause of which was not very evident. Is it possible 

 that the explanation just applied to Scafell might apply to this 

 case also ? * 



Keswick., April ith, 1873. 



P.S. — The above article was already in type when Dr. Eicketts' 

 communication on "Fissures, Faults, etc.," appeared in the May 

 Number of this Magazine. I do not see, however, that he throws 

 any light on the formation of fissures, since in Dr. Eicketts' opinion 

 earthquake shocks are produced by the action of faulting, and 

 " previous to a fault being formed, a fissure must have taken place " 

 (p. 204). What is the precise cause of the first formed fissure, Dr. 

 Eicketts does not state ; but it is clear he does not connect it with 

 earthquake shocks. Space will not permit me to do more at present 

 than add this postscript. — J. C. W. 



Keswick, Ma7/ 20th. 



III. — On the Formation of Mountains, with a Ceitique on 

 Captain Hutton's Lectuee. 



By Rev. ,0. Fisher, F.G.S. 



THE subject of Captain Hutton's lecture,^ on the Formation of 

 Mountains, delivered at Wellington, New Zealand, is one which 

 has engaged a good deal of my attention, and was discussed by me 

 in a paper read before the Cambridge Philosophical Society, and 

 printed in their Transactions.^ In that paper I attributed the ele- 

 vating force, which has raised mountain ranges, to the contraction of 

 the heated interior of the earth, and subsequent wrinkling of the 

 crust so as to accommodate itself to the diminished nucleus. This was 

 an old hypothesis, but I believe the amount of horizontal pressure 

 produced in that manner had not been estimated before. Mr. 

 Mallet, the eminent seismologist, read a paper on the same subject 

 before the Eoyal Society in May, 1872, in ignorance of what I had 

 written, and came to the same conclusion as myself as to the amount 

 of the horizontal pressure. And the late well-known mathematician, 

 Archdeacon Pratt, in a note to the last edition of his ' Figure of the 

 Earth,' ^ indorsed my result, which I give in his words: " The Eev. 

 0. Fisher shows, that the horizontal force of compression, thrown 

 into a stratum at the earth's surface, by the shrinking of the parts 



1 Geol. Mag., Vol. X., p. 166. 



2 Vol. xi., part iii. See also Geol. Mag., Vol. V., p. 493. 



3 Figure of the Earth, fourth edition, p. 203, note. 



