326 Analysis of Scientific Books. 



the planes a, lying between / and P, replace the obtuse solid angles, 

 while c 1 and c 2, lying between h and P, replace the acutt solid 

 angles. The planes d \ io d 12 replace the terininal edges of the 

 crystal, lying on the acute solid angles, in pairs, one of each pair 

 being in the front, and the other on the back of the crystal. The 

 planes b 1 and b 2 also lie in pairs, but on the obtuse solid angles, 

 each pair being in sight, but only one of each is numbered. The 

 planes i 1, 2, 3 are in pairs, replacing the acute lateral edges, one 

 of each pair only being in sight; while the planes g I, 2, 2> tend 

 to replace the obtuse lateral edges, being also in pairs, visible in 

 the figure on each side of the plane/". 



The getting-up of the present edition is a considerable improve- 

 ment on the second ; the paper is much better, the type clearer, 

 and the general appearance of the book neater and more elegant. 

 The size of the work renders it a very convenient travelling com- 

 panion, and the able manner in which a vast quantity of information 

 is condensed into a small compass, makes it equally serviceable in 

 the cabinet or the carriage. 



II. Traiti Elementaire des Reactifs, leurs Preparations, leurs Em- 

 plois speciaux,et leurs Applications d V Analyse. Par MM. A. 

 Payen, Manufacturier ; et A. Chuvallier. Paris, 1822. 

 8vo. Pp. 224. 



If we except the fourth volume of Thenard's Traite de Chimie, 

 there is no comprehensive system of rules delivered by modern 

 writers for accomplishing these two great objects of chemistry — 

 synthesis to effect analysis, and analysis to effect synthesis. The- 

 nard is, however, excellent, in as far as he could be supposed to 

 discuss so extensive a matter in 225 pages of rather open letter- 

 press. He classifies under the six distinct heads of gases, com- 

 bustible bodies, products of combustion, mineral salts, mineral 

 waters, and vegetable and animal substances, the various subjects 

 of analytical research ; conveying judicious precepts for the elimi- 

 nation of the different constituents of a compound, and for ascer- 

 taining their proportions. In a short concluding chapter he de- 

 scribes the processes by which we may discover to what class of 

 bodies, and consequently to what chapter of his instructions, any 

 unknown substance is to be consigned. Of the estimation in which 

 M. Thenard's system of analysis is held in this country, no better 

 evidence need be adduced than the fact of two independent trans- 

 lations of it into English having been executed by very able hands. 

 It is equally respected in France. 



However valuable it may be, as a summary digest of analytical 

 methods, its limits necessarily preclude many details of great in- 

 terest and importance. We were, therefore, well pleased to observe 

 the announcement of the work, whose title is prefixed to the present 



