February 6, 1902] 



NATURE 



315 



certain amount of motion we can get a certain amount of 

 heat." In the first place this form of statement is likely 

 to give the impression that heat is something entirely 

 different from motion, and in the second place it implies 

 that heat and motion are quantitatively convertible, which 

 is not strictly true. Further on the statement is made that 

 in order to bring about chemical change " high heat must 

 be used to aid the reaction." 



A great number of similar expressions are to be found 

 scattered throughout the book, and it seems a very 

 short-sighted policy to sacrifice accuracy and the use of 

 scientific modes of expression, even in attempting to 

 make matters more intelligible to beginners, as it is far 

 more difficult to get rid of early false impressions than to 

 acquire correct ones in the first place. This sort of treat- 

 ment is especially to be noticed in the author's account 

 of the ionic theory. On p. 90, ions are first introduced 

 very briefly to the notice of the student, and throughout 

 the succeeding pages many reactions are represented as 

 due to action between the ions ; and equations are printed 

 in which the ions are represented as atoms. This must 

 be exceedingly confusing to the student who has been 

 told in another place that atoms, generally speaking, 

 cannot exist in the free state ; and it is not until p. 417 

 that this difficulty is overcome for the student by the true 

 e.xplanalion of the nature of an ion. Another serious mis- 

 statement occurs in the account of the phenomena of 

 osmotic pressure, where, after quoting the extension of 

 Avogadro's law to solutions, the following passage 

 appears : " Notwithstanding the simplicity of this law, no 

 practical method for determining molecular weight based 

 upon it has yet been devised." 



The more descriptive part of the book is also not free 

 from inaccuracies. For example, in one portion of the 

 table on p. 15 the atomic weights are referred to H = i, 

 in another part of the same table to = i6. The term 

 combining weight is itself used in two different senses in 

 different parts of the book ; in the earlier portion it is 

 used as synonymous with atomic weight, and in the 

 later portion as a simple submultiple of the latter. 

 Another discrepancy is that which ascribes to krypton 

 on p. 19 the atomic weight 81 -8 and on p. 262 5867. 

 It is disappointing to find the author of so excellent a 

 work as the admirable little book on organic chemistry 

 failing to come up to the standard of accuracy which 

 is now demanded of teachers. 



HYDRAULICS. 

 A Treatise on Hydraulics. By Henry T. Bovey 



M.Inst.C.E. Second edition, rewritten. Pp. xviii -t- 583. 



(New York : John Wiley and Sons ; London : Chapman 



and Hall, Ltd., 1901.) 

 ' I "HE author of this treatise, in his position of professor 

 -I- of civil engineering and applied mechanics at 

 McGill University, Montreal, has exceptional oppor- 

 tunities for conducting experimental investigations on the 

 flow of water, owing to the remarkably complete equip- 

 ment of the hydraulic laboratory under his charge, which 

 the University owes, in addition to many other endow- 

 ments, to the munificent liberality of Sir William C. 

 McDonald, a well-known merchant residing in Montreal. 

 NO. 1684, VOL. 65] 



It is very satisfactory to note that Prof Bovey has made 

 full use of his opportunities in advancing the study of 

 hydraulics, as indicated, in the first instance, by the pub- 

 lication of the first edition of this book in 1895 ; whilst 

 this second edition, with its rearrangement, its large 

 quantity of new matter, and its additional tables of ex- 

 perimental results, marks the progress which has been 

 made in the interval towards raising the .subject of 

 hydraulics, so long based on empirical formula, into the 

 position of an exact science. 



The subject is divided into eight chapters, to each of 

 which, m addition to examples worked out in the text, 

 is appended a number of problems for the student, re- 

 lating to the questions dealt with in the chapter, together 

 with their answers. The book begins with a chapter on 

 general principles and the flow through orifices and over 

 weirs, followed by one on fluid-friction and pipe-flow, and 

 another on the flow of water in open channels ; and 

 these three chapters, each extending over more than a 

 hundred pages, complete the portion relating to the flow 

 of water, and occupy more than half the book. They 

 furnish a fairly exhaustive treatment of the subject ; 

 but though, owing to the large print, the widely-spaced 

 formuhe, the numerous diagrams, and the tables, the 

 actual contents of these chapters are not so great as might 

 be inferred from the number of pages they occupy, the 

 chapters are inconveniently long, and might with 

 advantage have been subdivided. This is undoubtedly 

 the portion of the book to which civil engineers engaged 

 in water-works, irrigation, and river improvement will 

 mainly refer for an elucidation of the difficulties involved 

 in the correct determination of the flow of water through 

 orifices, over weirs, along pipes, and in open channels. 

 A chapter is devoted to the important subject of 

 hydraulic machinery, including rams, presses, accumu- 

 lators, and water-pressure engines. Three chapters 

 relate to water-motors, dealing successively with iinpact, 

 reaction, and the principles of impact and tangential 

 turbines, vertical water-wheels, and turbines ; and the 

 final chapter deals with centrifugal pumps. The book 

 is illustrated by three hundred and thirty figures in the 

 text, mainly diagrams for elucidating the various theories 

 and principles dealt with, together with a few drawings 

 of machines referred to ; whilst a very convenient paged 

 list of the various headings of subjects throughout the 

 book is given in the table of contents at the commence- 

 ment, and a concise but useful index concludes the 

 volume. 



The mathematical treatment adopted right through, 

 with thie four hundred and forty-six examples given for 

 working out, render the book more especially suitable for 

 students in hydraulics who have had a previous mathe- 

 matical training, the book having, indeed, been originally 

 the outcome of a series of lectures to such students ; 

 and it will be doubtless of interest to hydraulicians, par- 

 ticularly in view of the advance it manifests in hydraulic 

 science. A less elaborate and less educational method 

 would probably have more favourably commended the 

 book to the notice of practical engineers interested in 

 hydraulic problems ; and, in its present shape, the book 

 seems likely, irrespective of its value to hydraulic 

 students, to be mainly advantageous to those engineers 



