88 Proceedings of the Asiatic Society. [May, 



A letter from C. P. Caspersz, Esq., Commissioner of the Suncler- 

 buns with an enclosure from Babn Sib Clmnder Mullick, announcing 

 the discovery of inscribed stones in the Sunderbun Lot 211, was read. 



The following letter from Archdeacon Pratt to the President, was 

 read. 



The President explained that his object in bringing forward this 

 letter was to give the Society the benefit of the writer's own resume of 

 the whole series of his papers, some of which had been published by the 

 Royal Society. The 5th and last of the series would appear, he hoped, 

 in the Society's Journal in the course of the present month. 



Calcutta, March 9th, 1865. 



" My dear Mr. Grote, — After our conversation last night, it strikes 

 me that it will not be amiss if I put in writing in a few words what is 

 the object of my last (and fifth) paper, laid before the Royal Society, 

 on Local Attraction for your information as President of the Asiatic 

 Society. 



There are two main problems to be solved by Great Trigonometrical 

 Surveys, (1) the very accurate mapping of the countries to which they 

 appertain, (2) the determination of the average form of the earth with 

 great nicety. The instruments used in the Survey operations are 

 adjusted by the plumb-line, and therefore any derangement in the 

 plumb-line by Local Attraction, (that is, by irregular attraction at the 

 place where the plumb-line is), affects the Survey operations and the 

 results deduced from them. 



In my first paper, I showed that the Himalaya mountains have a 

 great effect on the plumb-line in the plains of India. In my second, 

 that the Ocean, south of India, by deficiency of matter, has also a 

 great effect on the position of the plumb-line. In my third paper I 

 showed that slight variations of density in the materials of the crust of 

 the earth, such as no doubt exist, have also a considerable effect on 

 the plumb-line — but the exact amount cannot be found, because we 

 cannot survey the materials of the crust, as we can measure the height 

 and form of the mountains or the depth and boundaries of the ocean. 

 The result of these three papers was, that there were causes of consider- 

 able' derangement in existence, but their aggregate effect could not be 

 found, because that part which arises from variation of density in the 

 crust, cannot be found. 



