THE 



GEOLOGICAL MAGAZINE. 



No. LIV.— DECEMBER, 1868. 



ozRia-in^sT^Xj ^^I^TIC3L:ES. 



I. — Some Observations on the Supposed Internal Fluidity of 



THE Earth. 



By G. PouLETT ScROPE, Esq., M P., F.R.S., etc., etc. 



ALLOW me to make a few remarks on the two interesting 

 papers contained in your last number, — one by M. De- 

 launay, on the Supposed Internal Fluidity of the Earth, the other by 

 Mr. Shaler, on the Formation of Mountain Chains. I wish, in the 

 first place, to protest against the assumption contained in the first 

 paper (pp. 507 and 509) that the internal fluidity of the globe is 

 " generally accepted by geologists," on the evidence of its high in- 

 ternal temperature. No doubt the arguments employed in that paper 

 go to shew that, whether fluid or rigid within, the precession and 

 nutation of its axis would remain equally unaffected. So far, there- 

 fore, the well-known astronomical argument of Mr. Hopkins and 

 Sir W. Thomson, as to its entire or nearly entire solidity, must be 

 considered to be invalidated. But as Mr. Shaler justly remarks in 

 the second paper, p. 512, ''the proved increase of temperature from 

 the surface towards the centre, and the extreme elevation of heat 

 which must exist at considerable depths (as shewn in volcanic and 

 other igneous phenomena) cannot be regarded as evidence of general 

 fluidity, until it has been shown that the internal pressure has not a 

 greater influence in preventing liquefaction than internal heat in pro- 

 ducing that condition." 



Theorizing on the probable conditions of the solidification of the 

 earth, on the supposition of its having cooled from an originally 

 gaseous or fluid state, Mr. Shaler follows and sustains the view 

 suggested by Mr. Hopkins (very properly referred to in a note), 

 namely, that the process probably began at the centre, but that as it 

 advanced towards the surface there must have been a time when the 

 remaining liquid matter, being of inconsiderable thickness, the sur- 

 face also would begin to solidify by radiation of its heat into space, 

 from which time the farther solidification of the interior would pro- 

 ceed in two directions, outward from the central nucleus, and inward 

 from the outer crust. Ultimately the whole might be entirely solidi- 

 fied, or some portions of liquid matter might remain in a thin belt, 

 or rather in pockets or vesicles, here and there, at varying, but still 



VOL. V. — NO. LIV. 35 



