338 Scientific Intelligence. 



D 1 = 589, 625, Mtiller, Kempf. 



607 ' I Bell 

 603, J - Deu " 



602, Peirce. 



589, 590, Kurlbaum. 



— Annalen cler Physik unci Chemie, No. 2,1888, pp. 381-412. 



J. T. 



II. Geology and Natukal Histoey. 



9 1, On the distribution of strain in the Earth's crust resulting 

 from secular cooling^ with special reference to the growth of con- 

 tinents and the formation of mountain chains / by Charles 

 D avisos. With a Note by G-. H. Daewik — Starting from the 

 results reached by Sir W. Thomson and independently by Prof. 

 Darwin in regard to the rigidity of the earth, and from the con- 

 clusions of the former as to the secular cooling of the earth, Mr. 

 D avisos has gone forward and discussed the distribution of strain 

 in a solid globe resulting from secular cooling with reference to 

 the effect of this distribution on the great features of the earth's 

 surface. His conclusions, as will be seen, throw much light upon 

 what he terms "the beautiful contraction-theory of mountain evo- 

 lution " to which the work of Thomson and Darwin leads up. 



The author starts by supposing that the earth is bounded by a 

 smooth, spherical surface and is made up of a great number of 

 very thin concentric shells, each so thin that the loss of heat may 

 be considered throughout as uniform. The first conclusions 

 reached are : 



1. " That the rate at which any shell parts with its heat 

 increases to a certain depth below the earth's surface, where it is 

 a maximum, after which it decreases toward the center, and the 

 depth of the surface of greatest rate of cooling is continually 

 increasing, and varies as the square root of the time that has 

 elapsed since the consolidation of the globe." Also, 



2. " Folding by lateral pressure takes place only to a certain 

 depth below the earth's surface ; at this depth it vanishes, and, 

 passing through it downwards, folding gives place to stretching 

 by lateral tension." 



Accepting now, for the sake of simplicity, 174,240,000 years as 

 the time that has elapsed since the consolidation of the earth, a 

 period which lies well between the limits set by Sir W. Thomson 

 and for which the depth at which the rate of cooling becomes 

 practically insensible is 400 miles, the following conclusions are 

 reached : 



3. " (l) Folding by lateral pressure changes to stretching by 

 lateral tension at a depth of about five miles. (2) Stretching by 

 lateral tension, inappreciable below a depth of about 400 miles, 

 increases from that depth toward the surface ; it is greatest at a 

 depth of 72 miles, that is, just below the surface of greatest rate 

 of cooling; after this, it decreases, and vanishes at a depth of 



