THE 



GEOLOGICAL MAGAZINE. 



No. XLIV.— FEBRUARY, 1868. 



I. — A Notice of the Chemical Geology of Mr. D. Forbes. 

 By T. Sterry Hunt, F.R.S. 



THE Geological Magazine for October last contains a criticism 

 by Mr. David Forbes of certain views put forward by me in a 

 lecture delivered before the Eoyal Institution of Great Britain on 

 the 31st of May, 1867. Of this lecture a short-hand report appears 

 in this Magazine for August,^ besides which a condensed report, 

 revised by myself, is published in the proceedings of the Institution, 

 in the Chemical News for June 21st, and in three French translations 

 in the Bevue des Cours Scientifiques, Les Mondes, and Cosmos. The 

 Chemical News for October 4th contains a criticism of my lecture by 

 Mr. Forbes, to which I have replied in a communication recently 

 addressed to that Journal. 



In the lecture in question, I endeavoured to bring together the 

 results of modem investigations in physics, chemistry, mathematics, 

 and astronomy, and to construct from them a scheme which should 

 explain the development of our globe from a supposed intensely 

 heated vaporous condition down to the present order of things. I 

 could not pretend to discuss, from their various stand-points, all the 

 conclusions arrived at by different investigators, inasmuch as, even 

 had my attainments permitted, the limits of an hour's lecture would 

 have proved far too short. 



In regard to the structure of the earth I alluded to two views, 

 one of which supposes a liquid globe covered with a thin crust of 

 solidified rock, generally estimated at from twenty to thirty miles 

 in thickness ; while the other regards the earth, if not solid to the 

 centre, as having a crust at least several hundred miles in thickness, 

 and of such solidity and rigidity as to be, so far as superficial 

 phenomena are concerned, inert as if in a solid state. To this latter 

 view I incline ; and I cited in support of it the conclusions of Hop- 

 kins from the phenomena of precession and nutation, the inves- 

 tigations of Archdeacon Pratt on the crushing effect of immense 

 mountain masses like the Himalayah, and the deductions of Sir 

 Wm. Thomson from the phenomena of the tides, showing the 

 great rigidity of the earth, as so many concurrent evidences that our 



^ See the lists of Errata in tliis Magazine for September, p. 432, and October, 

 p. 478. 



VOL. V. — NO. XLIV. 4 



