Notices respecting New Boohs. 187 



to notice in these columns recently. We now have another work, 

 dealing with a different aspect of the subject, from the pen of 

 Dr. Moll wo Perkin, whose activity as a worker in the field of 

 electro-chemistry is well known to all interested in the subject. 



The book is divided into three Parts. Part I. is headed 

 " General," and may be said to form a short treatise on the more 

 purely electrical aspect of the subject. Part II. deals with electro- 

 chemical analysis, and Part III. with preparations by electrolytic 

 means. 



We prefer to deal with the last two parts first. The prepa- 

 ration of these must have involved a considerable amount of trouble, 

 for, as the author states in the preface, he decided not to include 

 any experimental work which he had uot tested personally. The 

 directions given are very explicit, and the author's wide personal 

 experience enables him to supply many useful hints. The biblio- 

 graphical references at the ends of the various sections form a 

 useful guide to the student who wishes to consult the original 

 papers on the subjects dealt with. On the whole, we have nothing 

 but praise for this part of the work, although the author is at times 

 extremely lax in his scientific terminology. We would remind 

 him, for instance, that CD. (current-density) is not measured in 

 amperes, but in amperes per unit of area. The unit of area adopted 

 by the author is the square decimetre ; so that when he speaks of a 

 CD. of 0*2 ampere, he really means 0*2 ampere per sq. decimetre. 

 We are quite well aware of the fact that the author drops the 

 "per sq. decimetre" for the sake of brevity. But there is no 

 excuse for scientific inaccuracy in a scientific work. If the author 

 desired to secure brevity, why did he not simply say *' a CD. 

 of 0*2," without mention of the particular unit, it having been 

 stated once for all that the unit is the ampere per sq. decimetre. 



We wish we could be excused the task of reviewing Part I. of 

 this book. It fairly bristles with inaccuracies which can only be 

 described as truly appalling. On p. 9, one of the columns con- 

 taining electro-chemical equivalents is headed "per coulomb iti mg. 

 per sec." (the italics are ours). On p. 24, the author refers to 

 branched circuits, and considers the case of two conductors, 

 A and B, joined in parallel ; " suppose " — we read — " the resist- 

 ance of A to be 1 ohm, and that of B to be 10 ohms, then only -^ 

 of the current will pass along B, the remaining ^passing through A." 

 On p. 27 we read " electrical energy is the product of the current 

 and potential," aud immediately afterwards, "the unit of electrical 

 energy ... is the volt-coulomb." On p. 57, we glean the valuable 

 piece of information that " by connecting the cells up in parallel, 

 the internal resistance cf the system is lowered, being very little 

 more (!) than that of only one cell." The author is hopelessly at 

 sea regarding the use of the terms " potential " and " E.M.F." — 

 to him they are merely a case of " tweedledum and " tweedledee." 



We feel that the best advice which we can give to the author is 

 that in a future edition of the book he should either omit entirely 

 Part I., which is an unpardonable blot on the work, or else have it 

 revised by a friend competent to deal with the subject 



