NA TURE 



[July 



192: 



most desirable. The hydrocarbons themselves are un- 

 suitable for this purpose, but the fatty acids with their 

 crystalline derivatives afford much more desirable 

 material for research. 



While in no way depreciating the enormous amount 

 of information contained in the book, which virtually 

 makes it an exhaustive dictionary, it is permissible to 

 suggest that from the point of view of the user, a much 

 more careful selection and limitation of the material 

 would be an advantage. E. F. A. 



Our Bookshelf. 



Die chemische Analyse. Herausgegeben von Dr. 

 B. M. Margosches. VIII.-IX. Band : Methoden 

 zur Untersuchung von Milch und Molkereipro- 

 dukten. Von Dr. Kurt Teichert. Pp. 374. (Stutt- 

 gart : F. Enke, 1909.) 11.40 marks (England: 

 45.60 marks). 



On account of the interest now being shown in the 

 quality of our milk supply, attention may be usefully 

 directed to this book, ft deals exclusively with milk 

 and dairy products and forms the eighth and ninth 

 volume of the general treatise on chemical analysis. 

 The greater part of the space is devoted to the standard 

 methods of analysis, but there is in addition a large 

 amount of information which ought to be of help to 

 the analyst and medical officer of health. 



A preliminary section deals with the composition 

 and properties of milk and the factors which are 

 responsible for any change in the normal composition. 

 Following this comes the portion which is concerned 

 with the detailed analytical methods for the deter- 

 mination of fat, milk sugar, protein, etc. The chapter 

 on cleanliness of milk and its freedom from bacterial 

 contamination puts the facts in a clear and convin- 

 cing manner, and is very valuable in view of the recogni- 

 tion of the dangers of uncleanliness both from the 

 standpoint of public health and the manufacture of 

 such products as butter and cheese. In this con- 

 nexion the employment of the reductase and catalase 

 tests has not become so general as was at one time 

 expected, although the direct determination of dirt 

 is now a regular practice in all analytical and public 

 health laboratories, and leads to the punishment of 

 those who dispose of filthy and insanitary milk. 



Purely bacteriological methods of examination are 

 shown to be difficult, particularly when applied to 

 the detection of pathogenic organisms. The fermenta- 

 tion test, whnh is easily and rapidly carried out, is now 

 being used to a greater extent both in connexion with 

 the public milk supply and the cheese factory. 



The chapter on the adulteration of milk, and the 

 interpretation of the results of analysis obtained in 

 this connexion, is valuable, as is also the one on the 

 testing of cream, skim milk, whey, condensed milk, etc. 



As 111 the case of milk, so with butter and cheese 

 there are given details of analytical methods and 

 hints on the interpretation of results. The detection 

 of adulteration by the addition of foreign fats is dealt 

 with, and other sections are concerned with the analysis 

 of materials used in the preparation of cheese. 



NO. 2751, VOL. I 10] 



The volume is one for reference and the details 

 appear to be scientifically sound. 



Aeroplane Performance Calculations. By Harris Booth. 



(The Directly-Useful Technical Series.) Pp. xv + 



207. (London : Chapman and Hall, Ltd., 1921.) 



21s. net. 

 The development of aviation appears to be entering 

 on a new phase in which " safety in the air " is singled 

 out as of primary present importance. This follows 

 an era of military devotion to the cult of "perform- 

 ance," and the object of the book under review appears 

 to be the statement of the detailed steps which have 

 hitherto been taken to secure the greatest speed and 

 maximum rate of climb of an aeroplane. 



It is probable that the actual arithmetical processes 

 described will rapidly fall out of use, but that the 

 principles invoked will have a greater degree of 

 permanence. The interest of the book is not so much 

 in the relative merits of the four methods of prediction 

 of aeroplane performance described in chapter n. as 

 in the statement of the problem as it appears to a 

 designer. Much of the book shows the individuality of 

 the author, but the general outlook is typically that of 

 the community of aeroplane designers. 



It is perhaps desirable at this point to indicate the 

 established position as to aeroplane design and its 

 relation to performance. The data used by all are 

 common — derived mainly from sources external to the 

 aviation industry — and have been used with almost 

 equal success by a number of designers. In the result 

 it is found possible to predict the consequences of the 

 best efforts from preliminary sketch designs. To 

 realise completely the maximum performance, it is 

 necessary for a designer to consider the details of his 

 craft carefully, and Mr. Harris Booth's book shows how 

 that may be done. Further, it illustrates an essential 

 element of progress, for it assesses in numerical form the 

 importance of separate items in the complete whole. 

 In illustration of this point, it will be found that 14 lbs. 

 is estimated to be the resistance of a flying-boat hull if 

 the open cockpits and hydroplaning steps are excluded. 

 A further estimate shows that the steps account for 

 52 lbs. at the same speed and each cockpit for a further 

 17 His. Here is a striking example of the fact that the 

 very small resistance of a smooth streamline body may- 

 be mi reased five- or six-fold by departures required for 

 various reasons. 



It is just because of its indications of the need for 

 care in design that the present volume may fairly be 

 accorded a place on the shelves of an aeronautical or 

 design office library. So far as can be judged its 

 importance is limited to such function, since the writer 

 is following common practice in supposing that " per- 

 formance " does not include " safety." 



Building Contracts: The Principles and Practia oj 



linn Administration. By Edwin J. Evans. (The 



Directly-Useful Technical Scries.) Pp. xviii + 304. 



(London : Chapman and Hall, Ltd., 1022.) 10s. 6d. 



net. 



The building trade resembles a good many others in 



that, while liberally supplied with works on the technical 



side, there is very little literature dealing with the 



business side. The present volume is intended to fill 



this gap. The subject matter is divided into four 



