342 



NATURE 



\Mar. 5, 1874 



regard and esteem of all true friends of Science ; he be- 

 longs to the same metal that has already formed a wedge 

 which will force open the secrets of inner Africa. 



OUR BOOK SHELF 



Adulterations of Food, with short Processes for their 



Detection. By Rowland J. Atcherly, Ph.D., F.C.S. 



(London : W. Isbister & Co., 56, Ludgate Hill, 1874.) 

 The attempt to notice the adulterations of food in 100 

 pages of large type is a somewhat rash one, and it is not 

 therefore surprising that the author of the treatise is 

 frequently compelled to dismiss his subject in a very 

 cursory manner. 



For two of the classes of readers whom he addresses, 

 the dealer and consumer, the work will no doubt be of 

 use, and it is also likely to be useful to the chemist, as 

 affording him a brief conspectus of the most likely adul- 

 terants in any particular article. Of what use, however, 

 the last 12 pages of letterpress describing the making 

 and use of volumetric solution are to the "trained chemist," 

 to whom the author addresses them, we are at a loss to 

 conceive. 



The information given in the part upon adulterations is 

 generally sound, though the statement on p. 34 that 

 prussic acid is found when nitro-benzol has been used as 

 a flavouring is absurd ; so far is this from being the case, 

 that it would be an indication of the use of a genuine but 

 insufficiently purified oil of bitter almonds. The process 

 for detecting alum in bread on p. 15 is also very unsatis- 

 factory, and certainly not adapted for the use of either 

 dealer or consumer. The book concludes with 21 neatly 

 executed cuts of various starches, chicory, cocoa, tea- 

 leaves and adulterating leaves found in tea, &c., as seen 

 under the microscope. In conclusion, we would advise 

 the author in a future edition to considerably expand the 

 part on adulteration and to entirely omit the part in- 

 tended for the " trained chemist," leaving that person to 

 obtain his information on volumetric solutions from the 

 proper sources. R. J. F. 



An Easy Introductioti to Chemistry. Edited by the Rev. 

 Arthur Rigg, M.A., late Principal of the College, 

 Chester. (Rivingtons : London, Oxford, and Cam- 

 bridge, 1873.) 

 The present work, founded, as the editor states, on 

 a " First Book of Chemistry," by Dr. Worthington 

 Hooker, published in America, is intended for the use of 

 children. Mr. Rigg calls attention to the inquiries of 

 "young persons " as generally suggested by their obser- 

 vations of things touched and handled, and states that 

 his aim has been "To supply information in a form which 

 it is hoped may be intelligible and interesting to all par- 

 ties concerned in thus learning to read the ever open 

 book of nature." 



The intention is a worthy one, and we have no doubt that 

 the work will serve its purpose in instructing some of its 

 readers, though we doubt if it will prove very intelligible 

 for " persons " so young as those to whom the style of its 

 commencement would seem to prescribe its use. We do not 

 say this with any desire to find fault, for it would indeed 

 be difficult to place the information in a simpler form 

 than has been done, but because of the great difficulty of 

 convincing young minds of the alterability of matter. 

 Either talking or reading alone is quite incompetent to 

 do this. Without experimental illustration they are 

 utterly meaningless except to well-advanced intellects, 

 and even there cannot do much, as anyone can tell 

 who has had the honour of meeting the chemist whose 

 knowledge extends not beyond books. In fact, chemistry 

 is not to be taught without the laboratory and its experi- 

 ments, and Mr. Rigg has shown his sense of their im- 

 portanca by the insertion of 46 beautifully-executed 



woodcuts of experiments and a frontispiece of a labora- 

 tory with its apparatus and fittings. 



Excepting in a school, however, the "young persons "of 

 the preface are not likely to meet with the actual experi- 

 ments of which illustrations are supplied, and those that 

 are of sufficient age to go to such a school might surely 

 have a rather more advanced book placed in their hands. 

 The question, however, which a reviewer ought to ask 

 himself is, Is the book such a one as would fairly carry out 

 the author's intention ? and to this we must, in this case, 

 answer " Yes." Granting the possibility of teaching che- 

 mistry to young children, Mr. Rigg's book would certainly 

 serve its purpose well. With regard to his facts, Mr. Rigg 

 is, as a rule, sound ; but we must demur to his statement 

 on p. 134, that " If (silica) is to these (grasses and grain) 

 and other plants very much what bones are to animals ; " 

 and again, on p. 167, "Every stalk of grain or grass is 

 chiefly wood. In both cases fine particles of flint are 

 scattered in the wood to make it firm enough to stand 

 even in a gale of wind." The experiments of Sachs and 

 others have long since disproved this theory. Such 

 blemishes as these are, however, of but little moment 

 when the main principles of the science are the object of 

 teaching, and on these Mr. Rigg is perfectly orthodox. 

 We must, in conclusion, compliment the pubhshers on 

 the very elegant get-up of the book. 



Die Rohstojfe des Pflanzenreiches : Versnch einer tech- 

 iiischeu Rohstofflehre des Pflanzenreiches. Von Dr. Julius 

 Wiesner. (Leipzig : Engelmann, 1873. London : 

 Williams and Norgate.) 



This is one of those elaborate German works which seem 

 as if they were intended completely to exhaust the sub- 

 ject of which they treat. Every substance of economical 

 or technical importance which is obtained from the vege- 

 table kingdom is treated of in detail from the point of 

 view of its practical utihty rather than its physiological 

 history ; its chemical, mechanical, and microscopical pro- 

 perties, the mode of its preparation or manufacture, and 

 its utility in the arts or commerce, are described. The 

 book is, in fact, a repertorium of technical botany. 



LETTERS TO THE EDITOR 



[ The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. No notice is taken of anonytnoui 

 coinmu)dcations.\ 



On a Proposed Statistical Scale 



At a lecture last Friday evening, at the Royal Institution, I 

 spoke on a subject which happens to lie at the meeting-point of 

 many special sciences, and therefore, as I am desirous of having 

 it well discussed, and from many points of view, it seems to me 

 best to state it afresh in your columns for that purpose. It refers to 

 the definition of the esiim&teA degree of deiYlopmciil of any quality 

 whatever, without reference to external standards of measurement. 

 The scale 1 propose depends on two processes; the one is securely 

 based on the law of statistical constancy, tlie other is doubtlully 

 based on the law of frequency of error. ( i ) At present we are accus- 

 tomed todealwithaveragesand the like, which can only be obtained 

 by measuring e;'c?y individual by a detached standard scale, and 

 going through an arithmetical process afterwards. Now I want 

 to deal with cases for which no external standard exists, and I 

 propose to proceed in quite another way, on the principle (hat 

 interco/nparison suffices to define. We have only to range our 

 group in a long series, beginning witli the biggest and ending 

 with the smallest ; and then we know by the law of statistical 

 constancy tliat the individual who occupies the half-w.iy point, or 

 any other fractional position of the entire length, will be of the 

 same size as the individual who occupies a similar position in 

 any other statistical group of similar objects. We state his 

 size witli statistical precision by saying that his place is so and so 

 In a series. \\'e appeal to a standard which lies dormant in every 

 group, and which a statistician can evoke, for temporary pur- 

 posei of comparison, whenever ha will. (2) What places in the 



