40 On Local Attraction. [No. 1, 



crust, which was originally formed hy a loss of heat radiated from the 

 surface into space, would reduce the heat of the fluid into which it sank, 

 and after a time a thicker crust would be formed than before, and the 

 difficulty of its being broken through would become greater every time a 

 new one was formed. Perhaps the tremendous dislocation of stratified 

 rocks in huge masses with which a traveller in the mountains, especially 

 in the interior of the Himalaya region, is familiar, may have been brought 

 about in this way. The catastrophes, too, which geology seems to teach 

 have at certain epochs destroyed whole species of living creatures, may 

 have been thus caused, at the same time breaking up the strata in which 

 these species had for ages before been deposited as the strata were formed. 

 These phenomena must now long have ceased to occur, at any rate on a 

 very extensive scale, as Mr. Hopkins's investigations on Precession appear 

 to prove that the crust is very thick, at least 800 or l,O0U miles ; and this 

 result has been recently confirmed by Professor W. Thomson in a paper on 

 the ' Kigidity of the Earth.' " 



These results meet with some confirmation from an examination of 

 the direction of the deflection of the plumb-line at several coast- 

 stations where it is drawn towards the sea. The amounts of deflection 

 are, however, so small that nrach cannot he built upon this. This, 

 at any rate, may be said, that they present no obstacle to the theory 

 so remarkably suggested by the facts brought to light in India, viz. 

 that mountain-regions and oceans on a large scale have been produced 

 by the contraction of the materials, as the surface of the earth has 

 passed from a fluid state to a condition of solidity — the amount of 

 contraction beneath the mountain-region having been less than that 

 beneath the ordinary surface, and still less than that beneath the 

 ocean-bed, by which process the hollows have been produced into 

 which the ocean has flowed. These coast-stations do in fact in several 

 instances tend directly to favour the theory, as they seem to indicate, 

 by excess of attraction towards the sea, that the contraction of the 

 crust beneath the ocean has gone on increasing in some instances still 

 further since the crust became too thick to be influenced by the 

 principles of floatation, and that an additional flow of water into the 

 increasing hollow has increased the amount of attraction upon stations 

 on its shores. 



I am, your's faithfully, 

 Calcutta, August 2, 1864. Joiin H. Pratt. 



