314 Notices respecting New Books. 



pose, all will agree ; but we do not quite see why Mr. Watson 

 should call this statement a definition. If any distinction is to be 

 made between definitions and axioms or postulates, surely the above 

 statement is a sort of compound axiom or postulate consisting of at 

 least two propositions: viz. (1) that the sum of the chords when 

 their number is indefinitely increased will have a determinate finite 

 limit ; (2) that this limit will be the length of the curve defined as 

 above. 



Although there are some other points on which we are not inclined 

 to adopt Mr. Watson's views, we willingly allow that his views are 

 in all cases well worth consideration, and that his book is an excel- 

 lent treatise on the elements of geometry. When a second edition 

 is called for, we would suggest that some of the diagrams should be 

 drawn again. In a book of this kind obvious inaccuracy in the dia- 

 grams ought to be avoided, for the learner's sake ; and this has not 

 always been done. E. g. p. 132, AF is obviously not a square; 

 p. 138, ABODE is obviously less than PGr; p. 219, the pentagon 

 is regular only by courtesy ; and so on in several other cases. 



Select Methods in Chemical Analysis {chiefly Inorganic). By Wil- 

 liam Crookes, F.R.S. Sfc. Illustrated with 22 woodcuts. Lon- 

 don : Longmans. 8vo, pp. xvi and 468. 



It has been the intention of the author to provide the student with 

 a laboratory companion containing information not usually found in 

 ordinary works on analysis. The methods here placed at the stu- 

 dent's disposal have all appeared during the last twelve years in the 

 f Chemical News,' of which Mr. Crookes is the well-known editor ; 

 but in this work they are systematically arranged, and the compiler 

 assures us that he has tested most and improved some of them 



(P- iu > 



The "contents" are divided into chapters; and in each chapter a 



group of the simple bodies is discussed, modes of separation from 

 all the preceding bodies being then given. Attention is very pro- 

 perly paid to the rarer elements, whose presence is unjustly 

 ignored in most treatises of this kind. But the work of systemati- 

 zation spoken of in the preface does not proceed very far; it is 

 limited, as in rfiost other manuals, to natural-history grouping. 

 Even here the results are occasionally open to question. Does 

 magnesium, for example, as closely resemble barium, strontium, or 

 calcium as they resemble each other ? Yet all four metals are classed 

 together in Chapter II. An entire chapter intervenes between gm- 

 cinum and aluminium. Iron is divorced from manganese, silver 

 from lead. It would probably be better to reject the natural-history 

 method altogether, and follow the order* of the atomic weights ; at 

 any rate, we should then be proceeding on an intelligible principle, 

 open to little dispute, and conducive to fresh comparison. 



The " preparations " incidental to analytical work are noticed 

 here and there. Thus very good methods are given for making pure 

 sulphuric acid, pure lead, zinc, &c. ; on the other hand, the way of 

 making phosphorous acid (p. 337) leads to no useful result. Most 



