362 



NATURE 



[August 19, 1897 



" We ourselves did try a form of usury law, but with 

 the natural result. It was evaded wholesale by necessitous 

 debtors, and the simple device was adopted of tacking on 

 the prohibited interest to the original loan. ... A 

 native ruler of the old type would probably begin by 

 putting half a score of usurers to death by slow torture ; 

 but this is not our way, nor would it in this case do much 

 good except to check money-lending for a season. We 

 are on the horns of a dilemma. We believe in the 

 sanctity of contract, but we loathe Shylock, and writhe at 

 seeing the peasant come shorn out of his clutches." 



As an interesting and clear account of these and in- 

 numerable other questions affecting the welfare of the 

 people, Mr. Crooke's book is greatly to be commended. 

 The stay-at-home Englishman is, and always has been, 

 inclined to lay down some system of theoretical perfec- 

 tion for the government of our great Eastern dependency. 

 He will learn here that there are too many causes of 

 friction— the opposing interests and prejudices of different 

 religions, different races, and different castes — to admit 

 of any perfectly smooth working of the great machine of 

 Government. For the sake of peace and practical ex- 

 pediency it is necessary to yield a little here and a little 

 there, and to moderate the rate of progress to suit the 

 conditions of the case. 



A really weak poirlt in an otherwise altogether admir- 

 able work is that portion of Chapter ii. which deals with 

 the history of the province from the earhest times down 

 to the Muhammadan conquest. Mr. Crooke has not con- 

 sulted the latest authorities on this subject ; and in not 

 doing so, he has made a mistake which is all the more 

 serious because, as it happens, the study of inscriptions 

 and coins has, within the last few years only, brought to 

 light a very considerable amount of historical informa- 

 tion. Very few of the dates for the earliest period given 

 by Mr. Crooke are accepted by scholars nowadays. The 

 initial year of the Gupta era is, for instance, no longer 

 regarded by any one as lying between the years i6o and 

 170 A.D. For this statement Mr. Crooke quotes Mr. 

 Vincent Smith : " the most recent authority on the gold 

 coinage of the Guptas." Mr. Vincent Smith is still 

 entitled to this designation ; but, between the date of the 

 work to which Mr. Crooke refers and the date of publi- 

 cation of Mr. Crooke's book, he has contributed a number 

 of articles to learned periodicals, in which he has accepted 

 the years 319-20 A.D. as the starting-point of the Gupta 

 era Again, a great deal more is known now about the 

 different Scythic invasions of Northern India and their 

 dates than would be inferred from Mr. Crooke's account. 

 In a word, this portion of the book — unimportant though 

 it may be from the author's point of view — is altogether 

 unsatisfactory, and should be entirely rewritten in a 

 new edition. 



It remains only to notice that the work is admirably 

 printed, bound, and illustrated. 



CHEMICAL EQUILIBRIUM. 

 The Phase Rule. By Wilder D. Bancroft. Pp. viii -F 255. 

 {The Journal of Physical Cheinistry, Ithaca, New York, 

 1897.) 

 T N the preface to this book the author says : — 

 *- " My idea is that all qualitative experimental data 

 (referring to chemical equilibrium) should be presented 

 as particular applications of the Phase Rule and the 



NO. 1 45 I, VOL. 56] 



Theorem of Le Chatelier, while the guiding principles 

 for the classification of quantitative phenomena should 

 be the Mass Law and the Theorem of van 't Hoff. In 

 this book I have tried to present the subject of qualita- 

 tive equilibrium from the point of view of the Phase Rule 

 and of the Theorem of Le Chatelier, without the use of 

 mathematics." 



Notwithstanding the thoroughness with which this 

 programme has, on the whole, been carried out, the 

 writer cannot help feeling that the result is not com- 

 pletely satisfactory, and that this is largely due to the 

 narrow treatment rendered necessary by the limitations 

 which the author has imposed on himself. The phase 

 rule itself merely gives the connection between the 

 number of components of a system, the number of 

 phases, and the number of external factors of equili- 

 brium (pressure and temperature usually) on the one 

 hand, and the number of independently variable factors 

 of equilibrium on the other. It gives no further inform- 

 ation about the system whatever. The theorem of Le 

 Chatelier permits us to predict the direction in which 

 the equilibrium will be displaced by a change in one of 

 the factors of equilibrium. A study of chemical equili- 

 brium from this limited point of view, almost of necessity 

 resolves itself into an enumeration of the different possible 

 cases (as, for example, a system containing one com- 

 ponent and one phase, which may be liquid, solid, or 

 gaseous ; a system containing one component and two 

 phases, and so on, considering in turn systems containing 

 two, three, or more components), together with a descrip- 

 tion of the special cases which have been investigated, in 

 so far as they illustrate the two guiding principles above 

 mentioned. This is, on the whole, the plan adopted by 

 the author, and his discussion of many possible cases of 

 which no actual example has been investigated., will 

 be of much service in indicating profitable lines for 

 research. 



The equilibria between solids and solutions, and 

 between two solutions are very fully treated ; whilst the 

 dissociation of calcium carbonate and of ammonium 

 chloride are the only ones of their kind mentioned, 

 equilibria in homogeneous gaseous or liquid systems are 

 omitted, and the metallic alloys receive somewhat scanty 

 attention. Some of these omissions are doubtless due to 

 the fact that the study of the cases in question is not 

 materially assisted by the application of the phase rule. 



The distinction which is made between solvent and dis- 

 solved substance (for which latter the author adopts the 

 not very euphonious term " solute ") appears to the writer 

 to be purely conventional, and not, as Prof. Bancroft 

 seems to think, a real difference. On pp. 36 and yj we 

 read : — 



" In cases of limited miscibility there is no difficulty in 

 telling which component is solvent and which solute ; 

 but when the two substances are consolute (miscible in 

 all proportions), there is at present no sure way of de- 

 ciding at what concentration the change takes place." 



The introduction of a conception which is incapable of 

 more accurate definition than the foregoing, can and does 

 only obscure the subject. The distinction of solubihty 

 from fusion curves and the consequent differentiation of 

 eutectic alloys from cryohydrates, seems to the writer 

 to be unnecessary and undesirable. On p. 127 there is 



