March 2, 1876] 



NATURE 



345 



represented by so many pounds' weight, but cannot pos- 

 sibly be represented by so many pounds' weight overcome 

 through so many feet ? ^ 



2, What is I' Fahr. of heat? 



One might just as correctly ask, " ^Vhat is i oz. troy of 

 time ?" We have heard of degrees of temperature, and of 

 quantities of heat, but we are totally unable to conceive 

 what could correctly be designated by i^ Fahr. of heat, 

 though it is clear that it is here used for " the quantity of 

 heat which can raise the temperature of a pound of water 

 by 1° F." But let us proceed to our final extract : — 



" If you have understood this explanation, you will have 

 some idea of the theory that heat is altered motion ; but 

 to complete the history we require not only to turn work 

 into heat, but also to turn heat into work. This had 

 already been done many years before by a French engi- 

 neer, M. Carnot, though he did not understand its real 

 significance, but it has now been most beautifully proved 

 by a long series of experiments made by M. Him, of 

 Colmar, in Alsace. What M. Him practically did was to 

 find out how much heat can be obtained from a ton of 

 coals, and then to find out how much work was performed 

 in an engine by that amount of heat. This was by no means 

 a simple task, for much heat is lost in various ways in 

 passing through the engine ; and even when he thought 

 he had allowed for all this, it was found that some of the 

 steam had turned back into water on its way, and thus 

 used up some of the heat. At last, however, when all 

 was carefully measured and calculated, he found that for 

 every p0Hnd of ivater heated f F., enough work had been 

 done te raise a weight of i lb. to a height of yy2 feet. 

 This, you wU notice, was exactly the converse of Joule's 

 experiment, and proved that exactly as much motion is 

 produced by means of confined heat as there is heat pro- 

 duced by means of checked motion." 



This is certainly very novel information. W^e have 

 hitherto been accustomed to think that " What M. Him 

 practically did was [not] to find out how much heat can 

 be obtained from a ton of coals," but to find how much of 

 that heat disappeared by having been actually converted 

 into useful work in an engine. 



But enough has been said to show the necessity for the 

 correction of those "grave errors" alluded to in the 

 second extract made above from the Preface. 



As to the chronological table with which the volume 

 concludes, and which is carried on to 1874, we would 

 only remark that it would not have been unduly extended 

 if a little space could have been found for even a bare 

 mention of a i^ti such names as Andrews, Forbes, 

 Graham, Stokes, Thomson, and Clerk-Maxwell in our 

 own islands, and a few more like Helmholtz, Foucault, 

 Pliicker, and Weber abroad. Surely such names should 

 have been caught at the very first cast of a net whose 

 meshes were found small enough to seize Drebbel, 

 Franklin, Celsius, Reaumur, Fahrenheit, and Humboldt ! 



HASSALL OX FOOD 

 Food: its Adulterations and the Methods for their 

 Detection. By Arthur Hill Hassall, M.D. (London : 

 Longmans, 1876.) 



THIS book is practically a new'edition of the author's 

 former work on " Adulterations Detected in Food 

 and Medicine ; " the main difference being, at least so far 



• We caa hardly blame our author for this blunder, great as it is, when 

 wc find substantially the same in a recent work by so learned and careful a 

 writer as Guthrie. In § 129 of his '' Magnetism and Electricity " we are 

 surprised to read that a body falling to the ground " will, just before reach- 

 inj; the ground, have acquired a momextcm, which is equal to the work 

 done in lifting it" The small capitals are ours — and they but faintly express 

 the agony with which we pause such a passage. 



as the plan of the work is concerned, that in the present 

 volume it has been thought judicious to exclude the articles 

 on drugs, which occupied indeed a very subordinate 

 position in the older one. We cannot but commend the 

 discretion thus shown : unsatisfactory as are many of the 

 processes employed by the public analyst, %'iewed as 

 methods of precision, none are more so than those appli- 

 cable to the analysis of pharmaceutical preparations. It 

 is probably to this fact that we must attribute the immunity 

 from the raids of the inspectors which the apothecaries 

 have on the whole enjoyed ; otherwise we must assume 

 that a higher standard 'of commercial integrity prevails 

 with our druggist than with our grocer or milkman, a 

 supposition to which, possibly, the milkman and the 

 grocer would demur. 



Despite the omission referred to, the present volume 

 is nearly double the size of the former one ; the in- 

 crease in bulk may indeed be taken as commensurate 

 with the increase in importance which the subject has 

 of late years assumed. The additional matter com- 

 prises articles on the Function, Quantity and Pre- 

 servation of Food, and on the influence of the utensils 

 employed in its Preparation and Storage : on Unwhole- 

 some and Diseased Meat ; and on Water and its Impurities 

 A considerable quantity of fresh analytical work has been 

 incorporated, and the author has been at the pains to test 

 the greater number of the various methods commonly 

 employed in the detection of adulteration, and in the 

 determination of its amount. In one or two instances, 

 as for example, in the determination of milk-residues, 

 he is scarcely just to his contemporaries. The 

 chemistry on the whole is fairly good ; thanks to the co- 

 operation of Mr. Otto Hehner, whose assistance Dr. 

 Hassall freely acknowledges. But we are inclined, in 

 common, we are sure, with those who have attempted to 

 make absolute alcohol, to doubt that this liquid is best 

 prepared by digesting spirit of 90 p>er cent, with well- 

 dried chloride of calcium (p. 795). It is well known 

 that calcium chloride unites with alcohol to form a 

 compound in which the alcohol plays the part of 

 water of crj'stallisation, and which is only decomposed 

 with difficulty. Much is said respecting the composition 

 of "fusel oil" and "potato spirit," although neither the 

 author nor his collaborateur thinks it necessary to indi- 

 cate anything with respect to the existence of isomerism in 

 the alcohols mentioned. On p. 676 we see Payen and 

 Chevallier's analysis of hops given : on the following page 

 precisely the same analysis is^ repeated as indicating the 

 composition of crude lupulin, which we are further in- 

 formed, amounts in good samples to about one-sixth of 

 the weight of the hops. 



The public generally, and Messrs. Allsopp and Co. in 

 particular, will be alarmed to learn that the water used in 

 the brewery of that eminent firm contains 7 65 grains of 

 sulphate of zinc to the gallon ! In the face of such a state- 

 ment it is hardly sufficiently reassuring to be told that 

 " the water is remarkable for its complete freedom from 

 organic matter" (p. 681}. The memory of the str)chnine 

 " scare " in connection with the national beverage has 

 scarcely died out : we trust that Dr. Hassall will be the 

 first to allay our anxiety as to the existence of white 

 vitriol in our " pale/' and " Burton." 



A considerable section of the book is devoted to the 



