jWchanique CShsie, 379 



that the several varieties of prehnite diff r in their chemical 

 composition much less than has been generally supposed. 



Another candidate for the same degree, Mr. P. N. Seven, 

 has examined a specimen of Olivine from mount Somme, 

 near Naples. The composition of this substance, as deter- 

 mined by Klaproth, would seem hardly to admit of its being 

 associated with chrysoHte. 



The following are the* results of two analyses made by 

 Mr. Seven. 



100.24 100.61 



These results, so widely different from those of Klaproth's 

 analysis, clearly justify the association of Olivine in the same 

 species with chrysolite. C. H. 



\^. Mtchanique Celeste. — The fifth and last volume of this 

 great work of M. de Laplace has made its appearance, in 

 which the question of the form of the earth is discussed in 

 variousnewpointsofview: viz. 1st. The dynamic effect of the 

 presence and distribution of the waters on the surface of the 

 globe. 2dly. Thecompression to which the interior beds are sub- 

 jected. Sdly.Thechange of size which may result from the pro- 

 gressive coolingof theearth. The author has arrived atthefol- 

 lowing results : That thegreatmassof theearth is by no means 

 homogeneous; that the beds situate at the greatest depth are 

 the most dense ; that those beds are disposed regularly round 

 the centre of gravity of the globe, and that their form differs 

 little from that of a curve surface, generated by the revolution 

 of an ellipsis; that the density of water is nearly five times 

 less tlian the mean density of the earth ; that the presence 

 and distribution of the waters on the surface of the earth do 

 not occasion any considerable alterations in the law of the di- 

 minution of the degrees, and in that of weight ; that the theory 

 of any consi'lerable displacing of the poles at the surface of 

 the earth is inadmissible, and that every geological system 

 founded on such an hypothesis, will not at all accord with 

 the existing knowledge of the causes which determine the 

 form of the earth ; that the temperature of the globe has not 

 sensibly diminished" since the days of Hipparchus, (above 



