NA TURE 



241 



THURSDAY, APRIL 28, 1910. 



DV:V.4.U7r'> 7iV ENGLAND. FRANCE, AND 

 GERMANY. 



(!) Elementary Mechanics of Solids and Fluids. By 

 Dr. A. Clement Jones and C. H. Blomfield. Pp. 

 vi +366H-xvi. (London : Edward Arnold, n.d.) Price 

 45. 6d. 



(2) An Elementary Treatise on the Dynamics of a 

 Particle and of Rigid Bodies. By S. L. Lonev. 

 Pp. viii+374. (Cambridge : L'niversrt}- Press, 

 1909-10.) 



(3) Initiation a la Mdcanique. By Ch. Ed. Guillaume. 

 Pp. xiv + 214. (Paris : Librairie Hachette and Co.. 

 1909.) Price 2 francs. 



(4) Die Mechanik, eine Einfuhrung mit einem meta- 

 physischen Nachip^^ri. By Dr. Ludwig Tesar. Pp. 

 xiv-f 220. (Leipzig and Berlin : B. G. Teubner.) 

 Price 3.20 marks. 



(5) Vorlesungen iiher technische Mechanik. By Prof. 

 Dr. August Foppl. IIL Festigkeitslehre, 4th 

 edition. Pp. xvi + 426. Price 10 marks. VL Die 

 wichtigsten Lehren der hoheren Dynamik. Pp. 

 xii + 490. Price 12 marks. (Leipzig: B. G. Teubner, 

 1909-10.) 



NEARLY five years have elapsed since the in- 

 defatigable Prof. Perr\' opened a discussion on 

 the teaching of mechanics at Johannesburg. Mr. 

 Blomfield is a teacher of considerable experience, and 

 this book may be safely assumed to be the outcome 

 of a study of this and' other similar reports, combined 

 with a practical knowledge of the difficulties of teach- 

 ing boys, and of the requirements which a teacher 

 has to satisfy on the part of examining boards over 

 which, unfortunately, he possesses no power of con- 

 trol. There have been a few, but not many, books on 

 elementary mechanics published since the Johannes- 

 burg discussion, and we naturally examine the pre- 

 sent book with a somewhat hypercritical eye, in the 

 hope of finding some indications as to whether any 

 real improvement has been effected since then. Let 

 us begin with generalities, and then descend to 

 details. 



(i) In the first place, a good deal of discussion has 

 taken place as to how far the use of text-books is 

 desirable in school teaching, the following alter- 

 natives being proposed : — 



(a) No text-book. 



(b) A text-book consisting of examples only. 



(c) A text-book containing a complete exposition 

 of the subject. 



It is the opinion of many of the best teachers that 

 a text-book should contain a brief but sufficiently 

 complete outline of fundamental principles, but that 

 examples should be the main feature. In this 

 respect Messrs. Jones and Blomfield 's book leaves 

 nothing to be desired. It is very largely made up of 

 examples, far more than any boy could work through 

 in a reasonable time, and the teacher who wishes to 

 adapt the course to his own requirements will onlv 

 have to put a tick against those he means to set to 

 his class. 



NO. 21 13, VOL. 83] 



In the second place, it is undoubtedly desirable, 

 as the authors claim, to teach statics and dynamics 

 simultaneously with hydrostatics, and it is important, 

 not only that the three should for convenience be 

 comprised in one book, but also that the simultaneous 

 treatment should not give rise to serious difficulties 

 in regard to logical sequence in any one of the 

 subjects. 



When, however, we examine the result we find 

 that the mixture of the three subjects in each chapter 

 leads to some rather striking anomalies, and the 

 reader naturally asks, What has Atwood's machine 

 got to do with the U-tube and the barometer? Why 

 do Boyle's and Charles's law come in the same 

 chapter with graphical methods? What connection 

 exists between centres of gravity and Archimedes 's 

 principle, or between force diagrams and centres of 

 pressure? Would not centres of gravity and centres 

 of pressure go better in the same chapter? If, how- 

 ever, the authors seriously think that this somewhat 

 heterogeneous mixture is found beneficial for teach- 

 ing purposes on the ground that it keeps a variety of 

 different ideas before the pupils at the same time, no 

 doubt something can be said in its favour, and we 

 should gladly defer to their views. 



Passing to matters of detail, we naturally expect 

 to find, in the examples, questions of a rather more 

 practical character than in the older text-books. But 

 the pupil who works through the questions might 

 almost believe that there were only three acute angles 

 in existence — 30°, 45°, and 60°. Why is it that other 

 angles so seldom figure in them? Ever}^ boy nowadays 

 has his tables of logarithms, and the first thing he 

 should do when he learns the parallelogram law and 

 Lami's theorem is to calculate resultants, using the 

 tables of log sines, &c. What is the use of teaching 

 him statics if he can only apply the methods to three 

 particular angles? But the absence of other angles 

 is the more remarkable when we speculate as to the 

 sources from which the questions have been taken, 

 especially in view of the fact that Government 

 examination papers have been consulted, and that in 

 some of these, 30°, 45°, and 60° have, we believe, 

 been taboo for some years past. Again, in the 

 chapter on projectiles, a good many examples are 

 to be solved by writing down the equations, but we 

 have failed to find any attempt to make the pupil 

 draiv the paths of projectiles by plotting. Is not this 

 calculated to produce the type of student who uses 

 elaborate algebra to prove an almost self-evident 

 result and generally fails? We have had abundant 

 experience of such students' failures in simple projec- 

 tile questions, and begin to wonder whether it would 

 not be better to omit the subject altogether. 



On the other hand, the book contains a good many 

 things which we had believed were at last dead and 

 buried. Wliat is the use of telling a boy that if a 

 particle is going north-east at 10 feet per second for 

 one second "it has travelled a distance OL (5v'2 feet) 

 due E., and a distance LP (5v^2 feet) due N."? If 

 he has any common sense he ought to think that it 

 would be equally sensible to say that two people 

 starting from London and Cardiff at 2 p.m., with 



K 



