November ii, 1922] 



NA 1 URE 



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formulas are given, one due to Greenwell and the other 

 to Aldis ; an example is given of the use of the former, 

 which is here worked out, giving a thickness of 1-19 

 inches ; if the reviser had worked out the same example 

 by the second formula here given, he would have ob- 

 tained a thickness of 1-98 inches, yet no hint is given to 

 tell the student that the two formulas do not agree, or to 

 help him in any way to reconcile so grave a discrepancy. 



It is also a pity that so many of the illustrations are 

 mere sketches, and badly executed at that. As an 

 example Fig. 104, which is intended to be the plan of a 

 horizontal winding engine, may be quoted ; an intelli- 

 gent boy of twelve who had seen a winding engine 

 would probably in his drawing indicate that there are 

 such things as valves and valve-rods. 



It has been thought advisable to direct attention to 

 the points in which this little book falls short of the 

 standard to which it might so easily be raised, because, 

 as already stated, it has evidently a very decided sphere 

 of usefulness, and in a work of this kind addressed to 

 the beginner it is pre-eminently necessary that he shall 

 receive no wrong impressions and shall be left with 

 nothing to unlearn when he advances to the higher 

 stages of the subject. 



Essays on French Science. 



Discours et mManges. Par Emile Picard. Pp. v + 292. 

 (Paris : Gauthier-Villars, 1922.) 10 francs. 



THIS volume contains discourses, short essays, and 

 obituary notices of some distinguished Freni h 

 men of science. It may be warmly recommended, more 

 especially on account of the obituary notices, which 

 do not confine themselves — as is too frequently the 

 case — with an account of the work done, but tell us 

 something of early surroundings, education, and 

 temperament, and thus bring out the personality as 

 well as the results achieved. It is not only that the 

 account gains in interest thereby, but the information 

 allows us to judge more adequately of the individual 

 influence exerted on contemporary science. 



Pierre Duhem's work is recognised in this country by 

 every one familiar with thermodynamics, but the 

 personal touches which M. Picard's account supplies 

 give us just what is wanted to appreciate the full value 

 of the man. Poincare is better known to us, perhaps 

 Darboux also, but we shall find here something new 

 about them as well as about others with whose work 

 M. Picard deals. The notice of Lord Kelvin is excellent. 



The author does not always confine himself to those 

 branches of science which he has himself enriched by 

 valuable contributions. As secretary of the Academy 

 of Sciences he has to undertake the duty of explaining 

 the ground for the award of prizes, some of which l ; ke 

 NO. 2767, VOL. I IO] 



that founded by Mr. Osiris, include a wide range of 

 subjects. We thus find short discourses on " French 

 A via i ion in 1909;' and even on " Antityphoid Vaccina- 

 tion." A lecture on the diminution in the birth-rate 

 was no doubt inspired by the atmosphere of the war, 

 and some of the other writings are even a more direct 

 outcome of the anxieties of the time at which they were 

 written. Here it is perhaps allowable to make one 

 criticism. In the essay on " Les Sciences mathe- 

 matiques en France," M. Picard shows so much know- 

 ledge of scientific history in other countries and such 

 fair appreciation of the international aspect of science, 

 that one regrets the inclusion of an article that origin- 

 ally appeared in the Revue des Deux Monies : 

 " L'histoire des sciences et les pretentions de la science 

 allemande." There is no doubt much in it that is true, 

 but it is not written in the dispassionate and eminently 

 fair spirit which pervades the rest of the book and it 

 strikes a discordant note. 



Graphical Methods in Ciystallography. 



Graphical and Tabular Methods in Crystallography as 

 the Foundation of a Neiv System of Practice : With a 

 Multiple Tangent Table and a ^-Figure Table of Natural 

 Cotangents. By T. V. Barker. Pp. xvi + 152. 

 (London : T. Murby and Co., 1922.) 145. net. 



IT has been anticipated for some time that Mr. 

 Barker would publish an account of the graphical 

 and tabular methods in crystallography which he has 

 been teaching at Oxford, and that his book would 

 include a description of the form of two-circle gonio- 

 metry and its special application to crystallochemical 

 analysis, which he recommends as the result of his 

 studies in Russia under the late Prof. Fedorov. The 

 present volume only very partially fulfils these expecta- 

 tions, crystallochemical analysis being reserved for a 

 further publication. So far as it goes, however, the 

 book is a valuable presentation of extant graphical 

 methods, and it concludes with a most useful table 

 of multiple tangents. 



The main purposes of the monograph are " to provide 

 the researcher with a select collection of exact graphical 

 methods, which personal experience has proved to be 

 both accurate and time-saving ; to discuss the relation 

 of these methods to formal processes of computation ; 

 and. finally, to outline a new system of practice." 

 The methods described involve the use of both the 

 stereographic and gnomonic projections, and are a 

 mixture of the well-known ones due to Penfkld. 

 Hutchinson, V. Goldschmidt, and Fedorov. A crystal- 

 lographic protractor is described and recommended, 

 which in itself is a happy combination of the features 

 of the Penfield, Fedorov, and Hutchinson protractors. 



U I 



