Figure of the Earth. 35 



course to any foreign authority or assistance whatever. Dr. 

 Thomson, in his review of the last vohune of the Philosophical 

 Transactiojis, hsi6 taken the trouble to observe, that Laplace had 

 before pursued a similar investigation, although the slightest in- 

 spection of the dates of the respective papers might have con- 

 vinced him, that Laplace had done no more than justice, in ac- 

 knowledging the true source of the theory in question. The 

 geographical elements of the problem have been supplied by the 

 experiments and observations of Maskelyne and Cavendish, 

 compared with those of General Mudge, Colonel Lambton, and 

 Captain Kater ; the computations have been conducted by the 

 assistance of Mr. Ivory's most masterly investigations of the at- 

 tractions of spheroids, combined with the theory advanced in the 

 Philosophical Transactions, together with an auxiliary approxi- 

 mation, for supplying the want of convergence of the series. 



It is unnecessary to enter into any inquiry respecting the pre- 

 cession and nutation, as connected with the earth's density, since 

 these effects are known to depend on the ellipticity of the 

 spheroid and of its strata alone, without any regard to the 

 manner in which the density is distributed among them. 



London, 2d Jan. 1820. S. B. L. 



Art. III. Geological Description of the Hills which pursue 

 the Course of the Wi/e, from Ross to Chepstow, with Re- 

 marks upon the Characteristics of the Hei'efordshire Forma- 

 tions, and an Outline of the Stratifications of the Forest of 

 Dean, and the opposite Shores of the Severn. JBy John 

 FoSBEOOKE, Esq. 



[Communicated by the Author.] 



The want of industry and accuracy in acquiring statistical 

 descriptions of the geology of particular districts, has been 

 much the subject of animadversion, among the authors of sys- 

 tems of this science. In matters of general literature, whatever 

 is local can only be interesting to a few, but we should divest 

 ourselves of such particular considerations in relation to subjects 

 of this kind, and reflect that the conformity of the most unin- 



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