272 T. Mellard Reade — Sedimentation and Temperature. 



not represent so late a subsidence as our deposits in the lake region, 

 for tbey are not the superficial gravel, but are covered by a few feet 

 of more recent till. 



These few foreign examples, just cited, show that the continental 

 movements, as set forth in this paper, are not peculiar to America, 

 but they were probably not synchronous, although they have taken 

 place in the most recent geological times. 



This paper must of necessity be imperfect, as it is the first attempt 

 to work out the detailed evidence of recent terrestrial subsidence 

 from records in the ancient shore-lines, many of which have only 

 lately been reported. All of the phenomena cited sbow that in 

 modern geological times there have been gigantic movements causing 

 the earth's crust to move to and fro, producing conditions which, 

 have greatly modified the physical features, climatic conditions, and 

 distribution of life. 



VII. — The Effect of Sedimentation on the Temperature of the 



Earth's Crust. 



By T. Mellard Reade, C.E., F.G.S., etc. 



MY letter in the March Number of the Geological Magazine, 

 asking for a description of the " Herschel-Babbage " theory 

 of Mountain formation, appears to have called forth Mr. Davison's 

 " Note on the Expansion Theory of Mountain Evolution,"^ in which 

 he favours us with his definition of the " fundamental principle of 

 the theory of terrestrial evolution which has sometimes been called 

 the 'expansion theory.' " 



Whether this fundamental conception is identical vpith the " Her- 

 schel-Babbage " theory is not stated, but I am obliged to Mr. 

 Davison for putting his views on the subject into a form admitting 

 of examination and discussion. To make my meaning plain, I shall 

 have to repeat Mr. Davison's ovs^n vi'ords. 



"Masses of sediment laid down in an area of subsidence are 

 gradually lowered to regions of the earth's crust that are at a higher 

 temperature than that in which they were deposited. The sediment, 

 being heated, expands, is crumpled and folded internally, and, 

 bulging up at the surface, is reduced by deniidation to the form of 

 a mountain-chain." ^ On which the following observations are 

 made. " It is obvious that the heat which passes into and expands 

 the sediment must be withdrawn from the immediately adjoining 

 parts of the earth's crust, partly laterally, but chiefly from below ; 

 and that the amount of heat gained by the sediment must be equal 

 to that lost by the crust." 



So far from this being " obvious," I consider it a fundamental 

 misconception. If a mass of strata at the surface having the sur- 

 face temperature could be placed in contact with another mass, say 

 ten miles deep, having the temperature due to that depth, the colder 



^ Geological Magazine, May, 1891, p. 210. 



2 Jt is unnecessary for me to criticize this " fundamental " definition further than 

 to disclaim it as an adequate statement of my own theory. For an outline of this 

 I must refer those interested to the forthcoming June number of the Philosophical 

 Maorazine. 



