SCIENTIFIC WRITINGS. 403 



I have tried to solve this contradiction by showing 

 that considerations having reference to actual facts op- 

 posed the physical foundations of Thomson's calculation. 

 The chief of these is that Bischof s statement, that sili- 

 cates become about 20 heavier in passing from the 

 fluid to the solid state, is incorrect as follows at once 

 from the well-kown fact, that solid silicates always 

 float on the fused ones, when they have nearly assumed 

 the temperature of the latter. Further I called attention 

 to the point, that Lord Kelvin's calculation takes no 

 notice of the time required by the viscous terrestrial 

 mass to assume the form, which is every moment pre- 

 scribed to it by the deforming tendencies of the at- 

 traction of the sun and moon. As in these changes of 

 form we have to do with dislocations of masses, which 

 stretch continuously over the whole body of the earth 

 from molecule to molecule, and therefore require a con- 

 siderable time to take place, no universal tidal wave 

 could be produced, advancing uniformly with the earth's 

 rotation, and altogether such an one could only arise 

 to a very slight degree. A refutation of these objec- 

 tions to the mathematical necessity of a solid core is 

 still wanting, and we are therefore entitled, in dis- 

 cussing the formation of the earth's surface to assume 

 a viscous or gaseous state of the interior. 



o 



As regards the formation of the earth's surface 

 the local elevations, the formation of the stratified 

 diluvium covering almost the whole surface, earth- 

 quakes and volcanoes, have also a special interest for 

 the non- geologist. I have tried to give an explana- 



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(UNIVERSITY) 

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