December i, 1892J 



NATURE 



Q9 



hints in the concluding chapter should be found very 

 serviceable. 



Mr. Brothers has produced a very serviceable and use- 

 ful addition to our photographic literature ; as a hand- 

 book for students it perhaps is somewhat too bulky, 

 but nevertheless it will be very much used by them. 

 Every photographer who wishes to know something 

 about the art with which he is working, and who does 

 not wish to limit himself to the mere cut-and-dried 

 manipulations.shouldatany rate makehimself acquainted 

 with the volume. W. J. L. 



MA TRICULA TION CHEMISTR V. 



Matriculation Chemistry. By Temple Orme. (London : 

 Lawrence and BuUen, 1892.) 



T^HIS is still another elementary manual dealing with 

 J- the non-metals and their compounds. According 

 to the author it can be studied most advantageously if 

 the rudiments of chemistry have first been acquired. 

 The book is built on pretty much the same plan as many 

 already in existence ; here and there, however, the read- 

 ing is enlivened by ideas which, if not altogether com- 

 mendable, have some pretensions to novelty. 



The author is evidently of opinion that much of the or- 

 dinary chemical knowledge can be presented in ^other 

 ways. Mass and weight first receive attention. In this 

 book there are no atomic weights ; atomic masses reign 

 supreme. In using a balance we are told that we do not 

 find weights, but " only masses." Indeed to bring this 

 idea home the following curious question is set : — " When 

 you * weigh ' a thing in an ordinary balance, do you find 

 its weight .? " 



After a passing allusion to constitutional formulae, in 

 which they are likened to pyrotechnic frames, the next 

 important alteration with which the author concerns 

 himself refers to the nomenclature of oxides. Such a 

 name as sulphur dioxide or carbon dioxi 1e is discarded, 

 for it is "founded upon a formula which is liable at any 

 time to be altered so as to suit our knowledge of atoms 

 and molecules." Anhydride is described as, " etymologi- 

 cally at least, a still more atrocious term " ; hence we find 

 that throughout the book SO2, CO2, &c., are spoken of 

 as acids. P2O5 is said to be a tribasic acid, N„( 5 a mono- 

 basic acid. CS2 is called sulphocarbonic acid, P.,S3 thio- 

 phosphoric acid, NjO hyponitrous acid, and so forth, in 

 spite of the fact that such compounds as that formed from 

 " hydric oxide and phosphoric acid {sic) are often called 

 ncids by modern chemists." 



The definition of a salt is thus summarily disposed 

 of:—" You are often asked what a salt is; the only 

 possible answer is that it is a compound." 



Such methods of tampering with terms which have a 

 generally-accepted meaning should, it seems to us, meet 

 with no encouragement. They can only end in muddling 

 the reader who wishes to pursue his subject by the aid of 

 any of our standard works. But matter which is liable 

 to do more immediate harm is frequently to be noted. 

 For instance, it is stated that there is no such thing as 

 the Law of Multiple proportions — it is only a corollary of 

 NO I 205, VOL. 47] 



the atomic theory. If, according to its usual interpreta- 

 tion, a law is a generalized statement of fact, it is rather 

 hard to see how its existence is affected by its relations 

 to any theory. 



To most chemists the brilliant work of Moissan has 

 sufficed to settle the question of the isolation of fluorine ; 

 the author is, however, still sceptical on this point. P.^03 

 is given as the formula of phosphorous acid {sic) ; 

 recent research has shown P40e to be correct. The 

 valency of potassium is said to have been fixed by a 

 " minute study of '\is gaseous compounds," water is stated 

 to be elastic with regard to shape, and from Avrogadro's 

 hypothesis molecules of different gases are stated to be 

 equal in size. 



Even when the author is apparently trying to be pre- 

 cise he is apt to mislead. The following definition is an 

 example : — " A chloride means a compound of chlorine 

 with some other substance which, though it is not itself 

 metallic in its general characteristics, possesses that im- 

 portant property of a metal, the capability of uniting 

 energetically with chlorine." Is it to be understood from 

 all this that a chlorine compound which is not produced 

 by energetic union — say an endothermic compound like 

 C2CI4 — is not a chloride .'' 



These extracts may serve to show that the book re- 

 quires to be carefully overhauled before it can be placed 

 with confidence in the hands of a beginner. 



OUR BOOK SHELF. 



Vegetable Wasps and Plant Worms ; a Popular History 

 of Entomogenous tungi, or Fungi parasitic upon 

 Insects. By M. C. Cooke, M.A., LL.D., A.L.S. [364 pp. 

 4 pi. and figs, in text ] (London : S.P.C.K., 1892.) 

 It is somewhat surprismg that a book on a subject of 

 such importance alike to the entomologist and fungolo- 

 gist has not been forthcoming long ago. It is true that 

 a Memoir on the subjecc was undertaken thirty-five 

 years ago by Mr. G. R. Gray, but, being privately printed, 

 was limited in circulation. To this work Dr. Cooke 

 admits his indebtedness for a large amount of information 

 bearing on the entomological aspect of the subject, and 

 it is to be regretted that he was not aware of the existence 

 of a much extended manuscript revision of the same work, 

 at present in the Botanical Department, Natural History 

 Museum. 



Dr. Cooke's book is professedly a popular work on the 

 subject, and consequently does not deal with the economic 

 side, relating to such matters as the "muscardine" or 

 silkworm disease, further than to indicate the nature and 

 affinities of the fungus causing the disease. 



The fungi parasitic upon insects are arranged under 

 four primary groups : the Cordyceps group, the Laboul- 

 beniacece ; the Entomophthorce ., and lastly a heterogen- 

 eous collection of moulds, which, with few exceptions, 

 are not truK parasitic and destructive. The structure 

 and general characteristics of these groups, with glimpses 

 of their life-history, are dealt with in an introductory 

 chapter Entf)mologists, whose main interest will be to 

 ascertain the name of any fungus parasitic on an insect, 

 will find this a comparatively easy matter, as the general 

 arrangement is an entomological one, commencing with 

 the Hymenoptera ; and under each is given an account of 

 all the fungi that are known to be parasitic upon species 

 included in the order. Numerous wood< uts in the text 

 and four plates assist very materially in thedeterminati n 

 of species. From the mycological standpoint the arrange- 

 ment indicated above is purely artificial, and introduced 



