i86 SCIENCE PROGRESS 



Levy, H., On the Criterion for Stable Flow of a Fluid in a Uniform Channel, 



Proc. Roy. Soc. Edin., xH, 192 1, 136-47. 

 RiABoucHiNSKi, D., Sur quelques cas de mouvements planes de fiuides 



autour de solides avec tourbillons, Coniptes Rendus, 174, 1922, 1224-7. 

 Ahlborn, F., Turbulenz und Geschwindigkeitsverteilung in Flusslaufen, 



Phys. Zeit., xxiii, 1922, 57-65. 

 Greenhill, G., The Tide in the Bristol Channel, Proc. Camh. Phil. Soc, 



xxi, 1922, 91, one of whose objects it is to show the advantage 



of using Fourier's functions, of which F« (z) is defined by the equation 



zy" -{- [\ + n) y' + y = o. 



The teacher of apphed mathematics will be interested in 

 a brief paper by A. Dakin, whose aim is well expressed by 

 its title : " That Pure and Applied Mathematics Ought to be 

 Taught and Developed pari passu in Boys' Secondary Schools," 

 Math. Gaz.j xi, 1922, 51-4. The author mentions an interest- 

 ing fact, that in public examinations of the School Certificate 

 and Matriculation standard, out of eight candidates taking 

 pure mathematics only one takes applied mathematics or 

 mechanics. Teachers of applied mathematics at universities 

 know how unpopular their subject is among most students, 

 and where students can take pure mathematics alone, the 

 number doing applied mathematics is almost negligible — and 

 this is in spite of the fact that many of the principles of 

 mechanics are taught in courses of physics, so that applied 

 mathematics ought to be almost a " soft option." This 

 reluctance towards the study of mechanics is probably due to 

 the fact that so little is done on the subject at secondary 

 schools, and if Dakin's paper will help to swell the number of 

 candidates taking mechanics or applied mathematics at the 

 School Certificate examinations, it will be an excellent thing 

 for university mathematics departments. 



It is of course true that many students find it difficult to 

 take courses in applied mathematics because of the need for 

 independent thought in doing examples in mechanics. Take, 

 for instance, the question of units in dynamics. The student 

 is often in a state of bewilderment, induced by the unpleasant 

 conviction that there is a symbol g which has a habit of 

 getting into the wrong place — and this has been known to 

 happen to some who are past the student stage in the subject. 

 The controversy between the adherents of engineer's and 

 of scientific units, about which considerable heat is often 

 developed {Nature, 109, 1922, 12, 44, 74-5, 139), can have 

 little bearing on this difficulty. Whether we use ^ as a multi- 

 plier and take the weight of a body of mass m lb. to be mg 

 poundals, or we use ^ as a divisor and take the mass of a body 

 of weight w lb. to be wjg slugs, the difficulty in the student's 

 mind is bound to persist. The experience of the writer of 

 these notes is probably that of many teachers of the subject : 



