102 



NATURE 



[April ii, 191 8 



plants grow, he will be unable to prune intelli- 

 gently and to secure the desired results." It is a 

 matter for regret, therefore, that the chapter on 

 plant physiology, with which the book opens, 

 should be inferior' to the later chapters, which deal 

 in a clear and useful manner with the practical 

 asp'ects of pruning. Readers with little or no 

 knowledge of plant physiology would, however, 

 be apt to find the treatment of the subject in this 

 chapter somewhat involved and confusing. 



In the succeeding part of the book the photo- 

 graphs of the branches of fruit trees are extremely 

 good, and are accompanied by very clear and 

 simple explanations of the methods of branching. 

 These should prove useful to fruit-growers and 

 to teachers of both horticulture and Nature-study. 

 The pruning of nursery stock, of young and of 

 mature trees, of bush fruits, and of ornamental 

 shrubs is fully dealt with. A chapter oh the " re- 

 juvenation of neglected trees " may be mentioned, 

 as it is a subject which should be of Interest to 

 some owners of small private orchards who are 

 anxious to obtain the best possible yields from 

 their trees. The author considers that in the case 

 of apple, pear, and sweet cherry trees specimens 

 fifty to seventy-five years old may be profitably 

 "rejuvenated," but that in the case of plums and 

 sour cherries It will be better to destroy the trees 

 and to re-plant. 



" Practical tree surgery " is another aspect of 

 the subject which the author has fortunately In- 

 cluded in the book, for frequently trees which are 

 specially valuable on account of their position or 

 association could be saved for long periods from 

 decay by a little skilled care and attention. Some 

 hints which might be useful to the authorities 

 responsible for the care of street trees are given, 

 and a model contract which should put "commer- 

 cial tree-surgery on a basis that will tend to 

 eliminate fakers " is outlined (p. 401). 



The book contains numerous references to the 

 experimental work on pruning which has been 

 carried out in this country and in America, and 

 summaries of such experimental trials and of their 

 results are given. These accounts are both fuller 

 and clearer than Is usual In abstracts of this kind. 

 As work of this nature has In the majority of 

 cases been published only in the bulletins of the 

 American experiment stations or in horticultural 

 periodicals, it is frequently difficult to trace, and 

 its Inclusion in the book is a feature of great 

 value. 



In conclusion, it may be added that the book 

 has a good index and more than three hundred 

 excellent Illustrations. 



OUR BOOKSHELF. 



Comment Economiser le Chauffage Domestique et 



Culinaire. Par R. Legendre et A. Thevenln. 



Pp. 123. (Paris: Masson et Cie, 1918.) Price 



1.25 francs. 



The question of economy In the use of fuel for 



general domestic heating and cooking is of no 



NO. 2528, VOL. lOl] 



small importance in relation to the general 

 economy of fuel rendered imperative in France by 

 the conditions arising from the war. This small 

 book, issued at a low price under the auspices 

 of the Minlstfere de I'Armement et des Fabrica- 

 tions de Guerre, Is primarily intended to indicate 

 practical methods of attaining economy in the 

 domestic use of fuel, without pretence at scientific 

 treatment of the subject, although there is an 

 excellent section on the principles of combustion 

 and the heat values of fuel. 



In the earlier sections the various ordinary fuels 

 are described and also the supplementary fuels, 

 such as peat, lignite, sawdust, tan, etc., 

 briquettes, and simple methods of briquetting 

 small coal. The advantage of using substitutes 

 to the utmost extent to relieve the demand on the 

 better fuels essential for industrial purposes is 

 emphasised. 



The second section deals with domestic heating 

 appliances, and, besides describing various forms 

 of fireplaces, stoves, etc., deals with the principles 

 of heating by radiation, conduction, and convec- 

 tion. There is a useful section on smoky chimneys. 

 The final section Is concerned with cooking, stress 

 being laid on the advantages of the Norwegian 

 oven. Each section concludes with a summary 

 of possible economies and brief directions as. 

 to their realisation. An abbreviated Issue of a 

 similar character would well be worth considera- 

 tion in this country. 



The Pasteurisation of Milk from the Practical 

 Viewpoint. By C. H. Kilbourne. Pp. Iv + 248. 

 (New York : John Wiley and Sons, Inc. ; Lon- 

 don : Chapman and Hall, Ltd., 1916.) Price 

 6s. net. 



The pasteurisation of milk consists in heating the 

 milk to a temperature between 140° and 160° F., 

 the milk being maintained at 140° for not less 

 than twenty minutes or at 160° for not less than 

 one minute. By this treatment disease germs 

 which may have gained access to the milk are 

 destroyed, as well as a large proportion of the 

 bacteria commonly present in milk, whereby its 

 keeping qualities are lengthened. In the United 

 States pasteurisation has been very largely em- 

 ployed, and this little book gives a capital survey 

 of the Installation, operation, and control of pas- 

 teurising plants. The author speaks from first- 

 hand knowledge, having been chief of the Divi- 

 sion of Pasteurising Plants, New York City De- 

 partment of Health. The various types of pasteur- 

 isers are suflficiently described, and this section is 

 illustrated with a number of diagrams of various 

 plants. The cleaning and cooling of milk, the 

 cleaning of containers, and home pasteurisation 

 are also dealt with, the eflficiency of various appa- 

 ratus Is discussed, and the changes induced in 

 milk by pasteurisation are described. 



The book can be recommended as a thoroughly 

 trustworthy guide on the subject of pasteurisa- 

 tion, useful alike to the student of hygiene and to 

 the practical dairyman. . ' R. T. H. 



