52 



NATURE 



[May 1 6, 1895 



manned the shaft to be a box full of liquid, which, if 

 rotated, would leave the latter behind somewhat, and the 

 apices would cause two stresses — tanjjcntial and centri- 

 petal — to act on the particles, the former only being of 

 momenta! value." 



Now what is the student, whether at the Xew Cross 

 Institute or elsewhere, to make of this without further 

 explanation r To introduce St. V'enant and say no more 

 than this, is surely giving either too much or not enough. 

 The same criticism might be repeated at many other | 

 places. Under the heading of " Pillars and Struts," we 

 are told that Euler is pronounced Oiler (this, at least, is 

 nothing if not practical), and his formula for the stability of 

 long columns is quoted without explanation. Gordon's 

 formula and constants are also quoted, and the subject is 

 dismissed with the dictum : 



" Claxton Fidler says a pillar-strength cannot be an 

 absolute quantity, but may be anywhere between Euler 

 and (Gordon's results." 



The theory of heat engines is treated in an equally 

 scrappy and inconclusive fashion. The student will not 

 find it easy to reconcile what he is told on p. 609 as to the 

 efficiency of the engine not depending on the working i 

 substance, with the statement, on p. 613, that "in prac- | 

 tice it is difficult to find a sufficiently perfect substance" 

 — which is given as a reason why the efficiency of a real 

 engine is less than the efficiency in Camot's cycle. He j 

 will find himself also at a loss to understand the state- j 

 mcnt that " in adiabatic expansion external work is done 

 at the expense of internal heat, and is therefore negative"; 

 or to see why the dr>'ness fraction of steam is necessarily 

 "a whole number" (p. 594). Again, to take a matter of 

 first-rate importance in regard to the action of steam in 

 the cylinder, initial condensation is spoken of as if it 

 affected the efficiency merely by the trifling alteration it 

 produces in the form of the expansion cur\e, and we do 

 not find a hint as to the real reason for its highly pre- 

 judicial effect. 



It would be unfair to conclude that all the theoretical 

 portions of the book are equally unsatisfactory. But 

 at the best, their brevity, and the narrow limits of mathe- 

 matical knowledge which the author assumes on the part 

 of his readers, make this part of the work more like an 1 

 engineering pocket-book than a treatise, the purpose of 

 which ought to lie to educate the student to reason about 

 the application of mechanical principles to engineering. 

 If the book, in this aspect, is representative of the teach- 

 ing which the new Polytechnics arc giving, it suggests 

 the inquiry whether what Lord Armstrong once called 

 " the vague cry for technical education " has met with 

 the liest possible response. We have no sympathy with 

 those who would exclude either engineer apprentices or 

 any other workmen from the highest education they are 

 capable of. But the question may fairly be asked whether 

 a good deal of what is apparently taught, and taught 

 for the express purpose of enabling pupils to pass a 

 specified examination, is in any just sense education at 

 alL TTjc mental discipline which would be obtained by 

 making a real study of problems such as are touched 

 on in this Ixiok, would be of the highest value as an 

 cduratton to the engineer. Hut there is no royal road 

 to the comprehension of elasticity and thermodynamics. 

 NO. 1333. VOL. 52] 



If the young apprentices and working lads, who, much 

 to their credit, flock to the new J'olytechnics, will take the 

 trouble to truly master any of these things, they will 

 gain an intellectual possession which will make thcni 

 better men, if not directly better workmen. We would 

 be the last to set a bound to their aspiration, or to dis- 

 courage the study of Euler and St. \'cnant. But as a 

 preparation for any such task, they must first, let us say, 

 leam what is the meaning of a differential coefficient. 

 To offer them scraps of conclusions which have to be 

 taken on trust, and " reasons " whi,ch can carry conviction 

 to no one except perhaps a jaded examiner, is giving stones 

 to children who presumably cry for bread. If this re- 

 presents the " theoretical " side of technical education as 

 the new technical schools understand it, or as examiners 

 accept it, we are still some way from a satisfactory 

 solution of the much-\exed problem. For a great deal 

 of this docs not usefully instruct, and does not effectually 

 educate : it is, as we have said, either too much or not 

 enough. 



THE LAKE OF GENEVA. 

 Le IJman Monographic Limmologiquc. By K. .V. Korcl. 

 Tome second. (Lausanne : F. Rouge, 1895.) 



THE first volume of Prof Forcl's work on the Lake of 

 Cleneva appeared in 1892, and was reviewed in these 

 pages (vol. xlvii. p. 5). It dealt chiefly with the physical 

 histor>' of the lake-basin, while the present one, con- 

 taining parts 6-10 of the whole work, begins with 

 " Hydraulics," or the currents, waves, si-ic/us, and other 

 deviations of the surface from the normal form of a fluid 

 at rest. It passes on to thermal questions, such as 

 the temperature at different depths, freezing of the surface, 

 &c. ; next to optical questions, such as the colour, oc- 

 casional iridescence and other peculiarities of the water, 

 and the phenomenon of the /•<//<; MorgiDia ; then to 

 acoustics (briefly) ; and lastly, to the chemistry of the 

 water. 



As it is impossible, in the limits of a comparatively short 

 notice, to deal with the numerous subjects included in the 

 present volume, we shall restrict ourselves to those which, 

 perhaps, may be more widely interesting than the rest. 

 The first one concerns those curious oscillations of the 

 level of the lake, which locally are called scii/ifs. This 

 phenomenon, as detined by Prof Forel, consists in an 

 alternate rise and fall of the surface of the water ; the 

 movement being roughly comparalile with that of a 

 balanced plank, when set swinging by a slight disturb- 

 ance. These oscillations are more or less rapid ; their 

 amplitude varying much. Commonly it is only a very few 

 inches ; but it may amount, though rarely, to about six 

 feet— the disturbance sometimes lasting for twenty or 

 twenty-five minutes. The whole question is discussed by 

 Prof Korel in its various aspects, and a history given of 

 the different explanations which have been advanced. He 

 attributes it neither to the effect of storms, nor to that nf 

 wind, nor to that of varying atmospheric pressure, but to 

 a disturbance of the whole mass of water by earth-tremors, 

 and compares it to the effect which may 1)e produced on 

 a fluid contained in a flat dish by Lipping the bottom. 

 In this hypothesis, however, he fninkh- admits the 

 existence of a difficulty ; namely, that earthquakes and 



