May i6, 1907J 



NA TURE 



51 



from the modern student. A few leading text-books 

 we had from which to select ; after reading these we 

 were encouraged at once to study the more simple 

 of original papers and treatises. In this way we 

 were led earlv to view science in the malcing, and 

 ever since we have valued the independent spirit 

 which this mode of training infused into us. Grant- 

 ing the increased facilities for absorption (it is 

 amazing what some of our junior students " know "), 

 it yet remains to be seen whether the present mode 

 of boiling down science into a sort of intellectual 

 pemmican will turn out better scientific men. Mean- 

 while, the flow of text-books continues, each written 

 to meet some want. The above arc some that we 

 have received. 



(i) In this first course in practical physics an 

 attempt is made to provide for pupils in day schools, 

 evening schools, and pupil teachers' classes a course 

 which is not too difficult for voung students, but 

 which contains all that is really essential. The de- 

 scription of the experiments is not surrounded by any 

 theory, the author's opinion being that this should 

 be given by the teacher — at any rate in the first year. 

 The course is a very simple one, consisting of 

 exercises in the measurement of length, area, 

 volume, mass, relative density, pressure of air, and 

 of a few experiments in heat. The instructions given 

 seem to be very clear in the main, and the order of 

 experiment is quite logical. 



(2) The text-book by i\Ir. Mackenzie is intended for 

 artisans in evening schools. These belong to a class 

 of student which has not been sufficiently catered 

 for up to the present, k volume like this is an effort 

 to provide something suitable for preparing them to 

 benefit more fully from the instruction given them 

 in the principles underlying their trades. 



The course laid down is wholly experimental. 



".Although instructions on the carrying out of e.x- 

 perimenls are given in detail, the students are not 

 told as a rule what they are expected to see or what 

 conclusions they should draw." 



No previous experience of laboratory work is 

 expected. The range covered is the same as in 

 No. I. We recommend this volume as a very suitable 

 introduction to the rudiments of the subject. 



i'3) " This book has been written in order to supply 

 a want," viz. a work containing approximately all 

 that is required by the syllabuses in experimental 

 science set for the Oxford and Cambridge junior 

 local and Central Welsh Board junior examinations. 

 It is primarily meant to help the teacher by providing 

 the material required for revision. The subject- 

 matter includes hydrostatics, mechanics, heat, and 

 chemistry. Each experiment is prefaced by a short 

 theoretical account which will add value to the book, 

 and each chapter ends with a set of questions. There 

 is not much room for originality in such a volume — 

 the conditions laid down in producing it tend to pre- 

 clude originality. The descriptions, so far as they 

 go, appear to be clear, and provided a student actually 

 does the described experiments are probably sufficient. 

 We regret to see the phrase " whole pressure " 

 alluded to in a modern text-book ; still more do we 

 NO. 1959. VOL. 76] 



regret to see it defined as thi; total force tending to 

 deform a body. 



(4) Mr. Martin's "Text-book of Mechanics" deals 

 only with statics; the kinematics and kinetics are to 

 follow in a second volume. For such an elementary- 

 book sufficient care is not always e.xercised in con- 

 nection Vtith fundamental illustrations. The necessity 

 of a strong push to displace appreciably a large ball 

 of iron hung up by a string indicates its great 

 weight, and not its great mass. The difficulty of 

 displacing it quickly depends on its mass. It is not 

 usually (rue to say that " two bodies of equal mass 

 moving with equal and opposite velocities will on 

 impact (collision) come to rest." Even two equal 

 lead balls will not behave in this way. Force is 

 defined in the introduction as rate of change of 

 momentum; no attempt is made to connect this 

 definition with the use of the word force in the body 

 of the book. Putting aside, however, this incomplete- 

 ness of logical treatment, the volume may be con- 

 sidered a useful summary of elementary rules regu- 

 lating the equilibrium of bodies. The last third of 

 the book consists of chapters on graphical statics 

 with applications to stresses in members of framed 

 structures. These chapters will be found to be useful 

 in teaching technical students, for whom they are 

 primarily intended. There is no calculus employed, 

 although it will be used extensively in the companion 

 volume, which is nearly ready for the press. 



(j) " Properties of Matter," by Mr. Wagstaff, is a 

 somewhat more ambitious work, since it is intended 

 to include all that is usually required for a pass 

 degree ; it therefore deserves a stricter examination. 

 We must point out that Borda's metre has long been 

 obsolete; the same remark applies to Borda's kilo- 

 gram. The work of the Bureau International seems 

 to be little known to writers of text-books. The 

 author de.serves credit for attempting to introduce 

 vitality into his subject by outlining various attempts 

 to " explain " matter. However, is not Osborne 

 Reynolds's interesting granular theory novi- dis- 

 credited? .Also, is there not some doubt about the 

 possibility of explaining all mass as being electro- 

 magnetic? We think that the selection of problems 

 has been very well made, and the treatment is very 

 clear. A proof is given of most of the theorems 

 stated, and this is usually sufficient for those who- 

 intend to proceed only to a pa.ss degree. Sugges- 

 tions, of course, might be offered in many ways, 

 rhe experiment on a stretching wire is most easily 

 made with a wire of copper. With a thin wire the 

 wjiole course of the extension up to the breaking 

 point can be obtained with small loads, and the 

 amount of permanent extension is much more con- 

 siderable than with steel. We think that some idea 

 of the nature and character of rolling friction should 

 be included. Were this done, an explanation could 

 also be given of the incompleteness of the working 

 out of the problem of the disc rolling down an in- 

 clined plane. The solution given (the usual one, by 

 the way) involves perpetual motion of the disc when 

 once started on a horizontal plane, for its acceleration 

 would be zero. The fact is that if the friction be 

 represented by a single force it cannot be represented 



