Reviews — T. Mellard Reade — On Mountain Ranges. 231 



thick deposits on the theory of a solid globe. They cannot make 

 a cavity for themselves, because the increase of pressure due to their 

 vpeight would increase the rigidity of the sea-bed. The cavity must 

 therefore somehow be already hollowed out, and it must conveniently 

 border a continent, to be within reach of the sediment. This is a point 

 which needs to be explained. But suppose that done ; and conceive 

 the sediment to be in process of accumulation. A second difficulty pre- 

 sents itself. Mr. Reade appears to consider that the hollow would be 

 first filled up, and that the heat would subsequently be conducted 

 from below into the sediments, and that they would swell up into a 

 mountain region. But as a fact the heat would enter them concur- 

 rently with their deposition, so that the swelling up would begin at 

 once. When the top of the deposit had reached the sea-level, 

 deposition must cease ; and it would be only the balance of heat 

 remaining to be made up after that time, which could be effective 

 towards raising the deposits above the sea-level. If deposition was 

 a rapid process, the larger part of the heat might remain still due, 

 and therefore available to raise the tract above the sea-level. But 

 it is a very slow pi-ocess — so slow that Mr. Reade thinks forty-two 

 millions of years not too long for the deposition of the matter from 

 the Carboniferous upwards in Western North America. Surely in 

 that time the sediments would be almost quite warmed up before 

 the}'' got above the sea-level. 



A valuable part of Mr. Reade's work consists of the experiments 

 he has made upon the rates of expansion of different kinds of rock. 

 His results agree closely with those obtained by Mr. Adie long ago ; 

 giving, as he puts it, 2-77 feet per mile per 100° Fah. He has not 

 referred to Mallet's experiments upon molten slag, of which I have 

 given an account in my " Physics of the Earth's Crust." ^ It is 

 satisfactoi'y to learn that, even at the laigh temperatures examined 

 by Mallet, the coefficient of expansion keeps fairly near that deter- 

 mined by Adie, and now by Mr. Reade, for lower temperatures. 

 Applying his result to masses of the size contemplated, the linear 

 expansion of 1000 miles raised 1000° Pah. (which he takes as the 

 mean increase of temperature for the new deposits and of the old 

 crust under them) would be about 5^ miles. At p. 158 he assumes 

 a lenticular mass, measuring 1000 x 500 miles, and 20 miles deep in 

 its thickest part, raised to a mean of 1000° F. above its previous 

 temperature. Lying in a rigid dish of crust, the entii'e cubical 

 expansion would be effective to elevate the surface. The lower 

 strata, being heated more than the upper, expand more, and become 

 crumpled, because their periphery is confined by the rigid crust. 

 They then burst up the superincumbent less-expanded beds, which 

 gape at the anticlinals. Into these the lower heated rocks are 

 intruded, and form plutonic cores. The interstitial differential move- 

 ments give rise to foliation, and similar phenomena ; and in places 

 the hot solid rock beneath, finding weak places, and " struggling " to 

 escape, intrudes itself into dykes, and becoming more and more liquid 

 as it reaches regions of less and less pressure, at last appears at the 



^ p. 68, note. 



