144 Notices respecting New Books. 



"When ordinary phosphorus (that is to say, colourless and trans- 

 parent phosphorus) is kept in water and is not exposed to a bright 

 light, it becomes covered with a white opake crust, seldom very 

 thick, which is known as white phosphorus. 



According to Baudrimont, who has subjected this to exami- 

 nation*, this is neither a hydrate, nor an.allotropic condition of 

 normal phosphorus, nor does it arise from a devitrification. It 

 is only ordinary phosphorus irregularly corroded on the surface 

 and roughened, so to say, by the combustible action of air dis- 

 solved in water — a slow combustion which diffused light accele- 

 rates, and which ceases as soon as the liquid contains no more 

 oxygen dissolved. 



XIX. Notices respecting New Books. 



A Treatise on Attractions, Laplace's Functions, and the Figure of 

 the Earth. By John H. Pratt, 31. A., Archdeacon of Calcutta. 

 Third Edition. Cambridge and London : Macmillan and Co. 

 1865. 



AS this is the third edition of a well-known work, we need not do 

 more than mention generally the nature of its contents, and 

 then advert more particularly to one or two points in which it differs 

 from foregoing editions. The first part, which is preliminary to the rest 

 of the volume, contains in the first place the usual investigation of 

 the attraction exerted by spheres, spheroids, and ellipsoids on internal 

 and external points ; next, an investigation of the properties of 

 Laplace's functions, and their application to determining the attrac- 

 tion exerted by bodies nearly spherical on external and internal 

 points ; and lastly, an elaborate and interesting discussion of the 

 attractions exerted by tablelands, mountains, &c. This last portion 

 of the first part is illustrated by a series of examples of cases actu- 

 ally occurring in geodetic operations, particularly those of the Indian 

 survey. It may be remarked that the attempt to take account of the 

 effects of local attractions is the distinguishing feature of the book. 



The second, and by far the larger part of the book is devoted to 

 the question of the figure of the earth. This is discussed from two 

 points of view, — first, theoretically, on the hypothesis of the earth's 

 being, or having once been, a fluid mass; secondly, practically, as 

 determinable by geodetic operations. Each of these discussions is 

 very elaborate ; and in the course of them there are passed in review 

 a number of detached observations and investigations scattered 

 through various scientific journals. Those who are interested in 

 learning what has been done on this subject since the publication of 

 Mr. Airy's celebrated Treatise, will obtain the requisite information 

 from the present work, which is brief, clear, full, and worthy of 

 Archdeacon Pratt's high reputation as a mathematician. 



* Comptcs Rendus, November 13, 180'5, 



