Notices respecting New Books. 319 



planetary radius vector, which corresponds to planetary velo- 

 city at the mean perihelion centre of gravity of Sun and Ju- 

 piter; for Jupiter's mean excentricity being *04316* 7 the 

 mean perihelion centre of gravity is at 



•95684 x 1117-87 -i- 1047-879 = 10208. 



The time of planetary revolution is 



1 year -^(214-86-r- 1-0208)* •= 10333-8 seconds; 



the velocity is therefore 2irrx 1*0208 -j- 10333*8 per second. 

 The velocity of light is 214-86 r-r 497-83, which is 695-4 times 

 the theoretical equatorial velocity of the nucleus, or the equa- 

 torial velocity of a nuclear atmosphere extending to 695*4 r. 

 This differs by less than ^ of 1 per cent, from the mean plane- 

 tary radius vector. 



Philadelphia, November 1875. 



XXXVIII. Notices respecting New Books. 



Physical Geography , or the Terraqueous Globe and its Phenomena. 

 Illustrated with 125 wood engravings, frontispiece, and 12 maps. 

 By William Desbobough Coolet. London : Dulau and Co., 

 1876 (8vo,pp. 429). 



" f^ EOGBAPHY, as the word imports, is a delineation or de- 

 " scription of the earth. In its widest sense this comprehends 

 not only the delineation of the form of its continents and seas, its 

 rivers and mountains, but their physical condition, climates and 

 products, and their appropriation by communities of men"f. Ac- 

 cordingly it admits of division into three fairly distinct branches, 

 viz. Mathematical, Descriptive, and Physical Geography. The 

 first might be classed as a branch of Astronomy ; the second, if its 

 relations to History are put on one side, is little more than a 

 description in words of the facts that are presented to the eye in a 

 good set of maps. The third, Physical Geography, can scarcely be 

 considered as a separate science • it is rather a delineation of facts 

 based upon a knowledge of all natural sciences • it passes in review 

 whatever is known respecting the form, internal heat, electro-mag- 

 netic tension of our planet, the volcanic reaction of its interior on 

 its solid crust, the phenomena of its aerial and watery oceans, the 

 distribution of the various forms of organic life over its surface, 

 and, so far as they can be made out, the causes whose action in the 

 past have determined the present condition of the surface, and the 

 distribution of organic forms upon it. It is plain that a subject 

 embracing so many topics, many of them with scarcely any mutual 

 connexion that can be traced, admits easily of division in several 



* Stockwell, op. cit. p. 38. 



t Outlines of Astronomy, c. iv., by Sir J. Herschel. 



