I02 



NATURE 



[Dec. I, 1S87 



work is divided into two sections, elementary and ad- 

 vanced, of which the former is about one-fourth of the 

 bulk of the latter. The reader must not go away with the 

 idea that the volume contains no original views, for, as Mr, 

 Abercromby says in his preface, " the results of many of 

 the author's original and unpublished researches are in- 

 cluded in its pages, such, for instance, as the explanation 

 of many popular prognostics ; the elucidation of the 

 general principles of reading the import of cloud-forms ; 

 the classification of those cases in which the, motion of 

 the barometer fails to foretell correctly the coming weather ; 

 and the character of that kind of rainfall which is not 

 indicated in any way by isobaric maps." 



Mr. Abercromby's pages convey small consolation to 

 adventurous weather prophets, such as Mr. Wiggins or 

 the framers of the New York Herald announcements. 

 At p. 433 we read : " From eight to twelve hours seems 

 to be the furthest time for which forecasts can be issued 

 in advance, and even then many local details cannot be 

 given." Again, at p. 426 he says : " On the whole, we 

 see that the crude notion of forecasting European storms 

 from the United States contains some elements of truth, 

 but that still, from the nature of cyclone motion, the idea 

 can never be used in practical forecasting." His state- 

 ments as to the impossibility of practically predicting 

 weather by observations of sun-spots are also made with 

 great care. 



The most interesting chapters, at least to the ordinary 

 reader, are those which relate to weather prediction, for 

 isolated observers. As regards the formation of clouds 

 and their indications, Mr. Abercromby sets forth the 

 results of much research, but in our opinion he speaks 

 somewhat too decidedly on points which are still sub 

 jiidice. 



We welcome tlie book most cordially, and anticipate a 

 considerable demand for it. We may say, however, 

 that in several places we have noticed slips in the word- 

 ing, and that the orthography of some of the foreign 

 names is not quite " according to Cocker." In some 

 cases the author's phraseology is not quite clear, and 

 paragraphs have to be read repeatedly before their precise 

 meaning is taken in. 



OUR BOOK SHELF. 



Class-book of Algebra Exa7nples for Middle and High 

 Schools. Part II., for High Schools. By John Cook, 

 M.A., Principal, Central College, Bangalore. (Madras : 

 printed at the Lawrence Asylum Press, Mount Road. 

 1887.) 

 This book contains, in addition to the examples which 

 form the main part of the volume, an " Introductory 

 Summary of Rules and Formulae," extending to about 

 one-third of the whole contents. Although Mr. Cook in 

 his preface lays special stress on this summary, we are by 

 no means sure that its introduction into the volume is an 

 improvement. It is insufficient to allow the student to 

 dispense with the use of a text-book ; and a student, who 

 desired to refresh his memory about some particular 

 method or formula, would do better to read it up in his 

 text-book, than to refer to a set of stereotyped rules. Such 

 a summary has the positive disadvantage that it inclines 

 the student to conceive of algebra as consisting entirely of 

 a set of rules, proceeding he knows not whence and lead- 

 ing he knows not whither — a conception which it is one of 

 the chief duties of a teacher of algebra steadily to combat. 



In parts of this introduction, moreover, there is a looseness 

 of method which is apt to prove very misleading to the 

 student. To refer to only one or two cases in point, we 

 would mention in the first place a confusion between an 

 integral or a rational number and an integral or a rational 

 function. This confusion is shown in the case of division 

 (p. 10) and in the case of root-extraction (pp. 46 and 51). 

 Again, Mr. Cook defines (p. 43) the G.C.M. of two or 

 more fractions, a conception which is perfectly useless in 

 algebra, and only tends to confuse the mind of the learner 

 as to the real meaning of the algebraical G.C.M. 



As to the main part of the volume, we are able to com- 

 pliment Mr. Cook on having brought together a number 

 of examples which are likely to prove useful, especially to 

 teachers. The examples show very considerable variety, 

 those on identities being particularly noteworthy. At the 

 end of each exercise stands a "model solution" which 

 will no doubt prove useful to the student ; but what does 

 Mr. Cook mean by saying in one such solution (p. 143) that 

 any three numbers that satisfy the relation a"- -\- b"- — c^ may 

 be expressed in the form yt, 4.n, i,n ? We trust that, 

 should the book reach a second edition, as it doubtless 

 will, Mr. Cook will either dispense with the introduction 

 altogether, which we should be inclined to consider the 

 better plan, or at least remove from it the faults in method 

 to which we have made objection. The good quahties 

 possessed by the main part of the book — the examples 

 themselves — would then render the volume one of un- 

 doubted value alike to students and teachers of elementary 

 algebra. R. E, A. 



77/1? Student's Hand-book to the Microscope : a Practical 

 Guide to its Sclectiofi and Management. By A Quekett 

 Club Man. (London : Roper and Urowley, 1887.) 



Although hand-books and practical guides to the use of 

 the microscope are by no means scarce, this little volume 

 will be welcome to many. It more completely, and in a 

 much smaller compass, meets the precise wants of the 

 beginner who intends to acquire a practical knowledge of 

 the use of the microscope, than the majority of kindred 

 treatises. But it aims only at elementary instruction in 

 the use of the instrument and its accessories. The author 

 does not burden the eager and ambitious amateur who 

 has just become possessed of, or is just about to obtain, a 

 microscope, with the complexities of collecting, preserving, 

 dissecting, preparing, and mounting. There can be no 

 doubt that to obtain a fair initial mastery of a good 

 instrument, with powers up to a quarter-inch objective, 

 and to become facile in the use of all the apparatus which 

 these may involve, for illuminating, polaj-izing, &c., and, in 

 short, in putting to its best and highest use such a micro- 

 scope, is by far the better course. To become hastily 

 acquainted with the microscope and its adjuncts, and then 

 to be diverted by elaborate processes for preparing and 

 mounting, is not the surest way to increase the number 

 of skilled and competent masters of the modern micro- 

 scope. The Quekett Club Man is evidently practical, and 

 sees this. He confines himself to a concise and useful 

 statement, aided by illustrations, of what the microscope 

 is and how its various accessories may be employed. 



The author does not claim to take the student into any 

 of the intricacies of high-power work, nor, save in an 

 incidental way, to call attention to the newest microscopy. 

 This is consistent ; but we regret that the new and only 

 accurate terminology is not employed. "Numerical 

 aperture," briefly explained, would have been wiser than 

 " angle of aperture," with no comment of any moment 

 as to its relatively unscientific nature. Nor are we quite 

 convinced that, although the author did not hold it to be 

 within his scope to discuss, or even indicate the existence 

 of, "apochromatic lenses," he was as helpful to the 

 uninitiated as he might have been, by not indicating the 

 existence of "compensating eye-pieces"; for both in 

 English and German microscopes, with any good objec- 



