May 21, 1896] 



NATURE 



adulteration had already done. He says : ' Those who 

 mix maize in the chocolate do very ill, because these 

 grains do bcyet a very melancholy humour, and those 

 which mix it in this confection, do it only for their 

 profit.' " 



The book is illustrated by numerous full-page and 

 smaller illustrations, and is well printed on thick, glazed 

 paper. 



THE CHEMISTRY OF ENGINEERING. 

 Chemistiy for Engineers and Manufacttircrs. A Prac- 

 tical Text-hook. By Bertram Blount, F.l.C, F.C.S., 

 and .A.. G. Bloxam, F. I.C., F.CS. \'olume I. Chemistry 

 of Engineering, Building, and Metallurgy. Pp. x + 244. 

 35 illustrations. (London : Charles Griffin and Co., 

 Limited, 1896.) 



THIS book gives a general view of chemical tech- 

 nology, and is intended for the use of engineers, 

 managers of works, and students. It is meant to be read, 

 and not to be treated as a book of reference, and therein 

 differs from the larger works which have already covered 

 the same ground. The authors ha\e confined themselves 

 to explaining the general chemical principles underlying 

 each process, working details and exact descriptions of 

 plant being omitted. Thus the manager of works en- 

 gaged on a particular process can probably, by perusing 

 this book, find out as much as he desires about any other 

 typical process, although it is perhaps unlikely that he 

 will learn from it much regarding his own business. It 

 is to be regretted that in pursuance of their plan of 

 avoiding all semblance of a book of reference, the authors 

 have in no case indicated where further information can 

 be obtained to supplement their own accounts. The 

 volume is divided into two parts, the first part dealing with 

 the chemistry of engineering and building, and the second 

 with metallurgy. These two parts are very unequal in 

 merit, the first being what it claims to be, a practical 

 treatise, which will doubtless be much appreciated by 

 manufacturers. In this part the accounts given of fuels, 

 and particularly that of gaseous fuel, are useful summaries, 

 and the chapters on steam-raising and on lubricants 

 contain a considerable amount of practical information. 

 These sections will be of value in enabling an owner of 

 machinery or user of power to detect causes of waste, 

 and to realise when saving may be eftected by calling in 

 expert assistance. 



The part devoted to metallurgy is much less satis- 

 factory. It is evident that, as the attempt has been made 

 to compress an account of the whole art into 104 pages, 

 only the barest outlines of the various processes could 

 be given. Among the unfortunate results of this are that 

 the Patio process for extracting silver from its ores, and 

 the cyanide process for extracting gold, arc each dismissed 

 in half a page, though in these cases the chemical actions 

 are complicated and the mechanical arrangements of 

 secondary importance. Such paragraphs serve no useful 

 purpose. There are more mistakes in this part than 

 should have been allowed to creep in, this constituting 

 another point of difference between the two parts. For 

 example, in describing the wet process of copper extrac- 

 tion, the reason for preventing the temperature from 

 rising much above 38' C. is incorrectly stated, the true 

 NO. 1386, VOL. 54] 



reason being that the production of ferric salts is favoure 

 by higher temperatures ; moreover, a little-used method 

 of keeping down the percentage of ferric salts in the 

 solution is given, while no allusion is made to the ordinary 

 one, viz. the passage of the liquid through a layer of 

 cupriferous pyrites, rich in copper. Again, on p. 214, sul- 

 phurous acid is given as one of the agents used to 

 precipitate gold from the solutions obtained in the 

 chlorination process, the fact being that it is only employed 

 to prepare solutions for the passage of sulphuretted 

 hydrogen, which is not mentioned. It may be a hard 

 saying, but there is little doubt that the whole book 

 would have been improved if the part on metallurgy had 

 been left out. Space could then have been found to 

 expand here and there the first part, which, excellent as 

 it is, might thus have been made still more useful. 



OUR BOOK SHELF. 



Elementary Practical Physics. By William Watson, 



B.Sc. (London : Longmans, Green, and Co., 1896.) 

 Elementary Practical Chemistry. By G. S. Newth, 



F.l.C. (London : Longmans, Green, and Co., 1896.) 

 We have long deplored the unfortunate division between 

 theoretical and practical chemistry in many schools and 

 classes, and have been convinced that, alike for educa- 

 tional and utilitarian purposes, physics was a neglected 

 instrument ; therefore, very heartily do we welcome the 

 new movement of which these books are a manifestation. 



Each volume is described on its title - page as a 

 " laboratory manual for use in organised science schools." 

 Each is written to the new syllabus of the South Kensing- 

 ton Science and Art Department, and each gives excel- 

 lent directions for setting up (and often for constructing) 

 apparatus, and for taking observations to demonstrate 

 the chief phenomena, and to verify the fundamental laws, 

 of chemistry and physics respectix'ely. In the physics we 

 are glad to see that nearly all the experiments are of a 

 quantitative character ; in the chemistry this is far less 

 often the case, partly owing, doubtless, to the nature of the 

 subject. In both works the experiments are judiciously 

 chosen, carefully described, and well illustrated, and m 

 many cases strikingly original. 



One criticism of principle may be made. Mr. Newth 

 says : " In a text-book it is almost inevitable that in 

 giving such directions as will lead a student on to the 

 discovery of a fact, the fact itself shall be stated." He 

 may be right in this ; but if so, it appears to afford 

 an argument against the use of such text-books in the 

 laboratory at all, for, speaking generally, the most 

 valuable exercise of all for the student is the study of his 

 recorded observations, and the endeavour to deduce 

 therefrom the property or law they demonstrate. Is not 

 the getting up of a proposition of Euclid a smaller intel- 

 lectual feat than the solution of a "rider"? 



Especially does this principle of research appear to be 

 applicable to the laws of elementary physics ; but I\Ir. 

 Watson apparently endorses Mr. Newth's view. 



With this reservation, we cordially recommend both 

 these volumes to the notice of teachers of elementary 

 science. From the point of view taken, the work has 

 been well done in both cases, and the books reflect credit 

 alike on authors and publishers. C. H. D. 



A Text-Bpok of the Science and Art of Bread-Makine^. 

 By William Jago, F.l.C, F.CS. Pp.618. (London: 

 Simpkin, Marshall, Hamilton, Kent, and Co., 1895.) 

 The practical application of science to the arts and 

 trades has been one of the most notable features of the 

 present century, with the almost universal result of 



