yune 1 8, 1 8 74 J 



NATURE 



colour, but soon a remarkable black, or nearly black, band 

 begins to form at the top of the lilm, and gradually to ex- 

 tend itself downwards. The lower boundary of this black 

 band is sharply defined. There is not a continuous gra- 

 dation of colour according to the arrangement in Newton's 

 table, but the black appears in immediate contact with 

 the white or even the yellow of the first order, and M. 

 Fusinieri has even observed it in contact with bands of 

 the third order. 



Nothing can show more distinctly that there is some 

 remarkable change in the physical properties of the film, 

 when it is of a thickness somewhat greater than that of the 

 black portion. And in fact the black part of the film is 

 in many other respects ditferent from the rest. It is easy, 

 as Leidenfrost tells us, to pass a solid point through the 

 thicker part of the film, and to withdraw it, without 

 bursting the film, but if anything touches the black part, 

 the film is shattered at once. The black portion does not 

 appear to possess the mobility which is so apparent in 

 the coloured parts. It behaves more like a brittle solid, 

 such as a Prince Rupert's drop, than a fluid. Its edges 

 are often very irregular, and when the curvature of the 

 film is made to vary, the black portions sometimes seem 

 to resist the change, so that their surface has no longer 

 the same continuous curvature as the rest of the bubble. 

 We have thus numerous indications of the great assistance 

 which molecular science is likely to derive from the study 

 of liquid films of extreme tenuity. 



We have no time or inclination to discuss M. Plateau's 

 work in a critical spirit. The directions for making the 

 experiments are very precise, and if sometimes they 

 appear tedious on account of repetitions, we must re- 

 member that it is by words, and words alone, that the 

 author can learn the details of the experiment which 

 he is performing by means of the hands of his friends, 

 and that the repetition of phrases must in his case 

 take the place of the ordinary routine of a careful 

 experimenter. The description of the results of mathe- 

 matical investigation, which is a most difficult but at 

 the same tiine most useful species of literary composition, 

 is a notable feature of this book, and could hardly be better 

 done. The mathematical researches of Lindelof, Lamarle, 

 Scherk, Riemann, &c., on surfaces of minimum area, 

 deserve to be known to others besides professed mathe- 

 maticians, and M. Plateau deserves our thanks for giving 

 us an intelligible account of them, and still more for 

 showing us how to make them visible with his improved 

 soap-suds. 



In the speculative part of the book, where the author 

 treats of the causes of the phenomena, there is of course 

 more r:om for improvement, as there always must be 

 when a physicist is pushing his way into the unknown 

 regions of molecular science. In such matters everything 

 human, at least in our century, must be very imperfect, 

 but for the same reason any real progress, however small, 

 is of the greater value. J. Clerk Maxwell 



HINTON'S PRACTICAL PHYSIOLOGY 



Physiolo^^y for Practical Use. By various writers. Edited 



by James Hinton. 2 vols. (Henry S. King cS: Co.) 



THIS work consists of a series of independent essays 

 by different writers, on points in physiology which 

 are Ukcly to prove interesting and instructive to the 



general public. No attempt is made to give more than 

 the best known facts of the science, together with the 

 most approved theories by which they are, at the present 

 day, connected. The thoroughness of the knowledge of 

 the authors, the largeness of the view they take of the 

 suliject, and the easiness of the style they adopt add 

 greatly to the interest of the book. 



Those who are accustomed to regard the living body as 

 an arrangement of organs which is quite peculiar and 

 whose mechanism is altogether inexplicable upon the 

 ordinary principles of mechanics and chemistry, will, 

 after having carefully studied this work, be convinced 

 how subject it is to the same influences that affect the 

 inanimate world, and that in fact it is nothing more than a 

 very complex machine, with the detailed mechanism of 

 which we are daily becoming more and more acquainted. 

 There are peculiarities however in the living frame which 

 fail to be represented in working out the analogy with the 

 steam engine. " The latter, after being constructed, daily 

 wastes. Every day it becomes worse, for each stroke of 

 its piston, to say nothing of the motion of its other parts, 

 implies a waste of the piston itself, and of the cylinder in 

 which it is inclosed, and in which it works. Now when 

 we get these out of order, the whole machine has to be 

 stopped, that the engineer may repair the deteriorated 

 portions." Such is not the case in the living body, which 

 differs from any machine yet constructed in that it is 

 ■' constantly working, constantly wasting, and constantly 

 repairing its own deficiencies^'' This is a most important 

 dilference between the two engines ; and it is almost 

 certain, that as our knowledge of machine-construction in- 

 creases, but little improvement will ever be made in this 

 direction, on account of the nature of the materials cm- 

 ployed, so that the difference will not be diminished. The 

 cell of a Daniel's battery may be instanced as an example 

 of an engine in which a partial repair of its structure is 

 continually being effected, for by the gradual solution of 

 the crystals of sulphate of copper that are always placed 

 in one of the compartments, the power of the battery, 

 and therefore the constancy of the current it developes, 

 is rendered more perfect. 



There is an excellent chapter on alcohol, in which the 

 principle of its action is most clearly explained. The 

 author prefaces his subject by clearly stating his views on 

 its social relations. For instance, he remarks: — "We 

 are not in the ranks of those who would remove the tax 

 on spirits, a tax whereby the poor as well as the rich are 

 made to contribute to the expenses of Government, by 

 paying a price above its production-cost for an article of 

 lu.xury ; and very far are we from siding with those who 

 misinterpret the liberty of the subject — we mean the right 

 of any man to wrong his neighbour, to sell him fictitious 

 goods — poison, perchance for food." . . . "We are not 

 abstainers ourselves, and we are not about to advocate 

 teetotalism under the banner of physiological instruc- 

 tion." 



There is a paragraph which quite represents the gener- 

 ally accepted doctrine of the relation of mental activity to 

 work done, but to which we think all physiologists ought 

 now-a-days to take exception. It is remarked that 

 "energy, the manifestation of power, or the conversion of 

 force into action, involves no expenditure of hfe or loss of 

 power. Thinking or lifting a weight is but a function of 



