62 



NATURE 



[March 28, 191; 



istry examinations knows how completely an 

 otherwise intelligent student can confound free 

 and combined nitrogen, free and combined potass- 

 ium, etc. We should like to have seen this dis- 

 tinction more strongly emphasised even at the risk 

 of repetition. Thus on p. 39 the passages occur : 

 "Phosphorus has an important part to play in the 

 formation of the seeds of plants and in hastening 

 their maturity. . , . Phosphorus appears luminous 

 in the dark. . . . Potassium is rather abundant in 

 Nature." 



For the rest, however, the book will be found 

 helpful. The numerous illustrations are largely 

 taken from bulletins of the various experimental 

 stations, and as the numbers are given they serve 

 not only to emphasise the various points, but also 

 as a guide to the voluminous and growing litera- 

 ture of the subject. 



{3) Dr. Whiting's little book is a useful sum- 

 mary of laboratory methods for students wishing to 

 become acquainted with the commoner soil micro- 

 organisms. Methods are given for isolating and 

 studying the common bacteria, algse and protozoa, 

 from soils, and references are given to original 

 papvers where the literature is more fully dis- 

 cussed. We note that Martin and Lewin's method 

 for collecting active protozoa from soil is found to 

 give good results with careful manipulation in the 

 author's laboratory, just as it does in this country ; 

 for purposes of enumeration, however, the blood- 

 corpuscle counting apparatus is used by Dr. 

 Whiting instead of the dilution method in favour 

 here. Exercises are also given on soil algae, which 

 have not yet received the attention they appear to 

 deserve. For a long time the student has been 

 able to obtain help in soil bacteriology, but he has 

 found more difficulty in getting assistance with 

 other organisms, and this little book can be re- 

 commended to him. 



(4) In the past, farm machinery has been used 

 to cheapen agricultural production rather than to 

 intensify it, and so it has found greater develop- 

 ment in new countries where labour is scarce than 

 in older countries where higher yields per acre 

 are aimed at. But in the nature of the case much 

 of the machinery that has been purchased has not 

 been properly used. It is not only the untrained 

 amateurs who know so little about machinery ; the 

 trained agricultural student also is not uncom- 

 monly helpless before a trivial breakdown. On 

 farms it is essential that someone should know 

 sufficient about machinery to be able to look after 

 it properly, to see that it is used to the fullest 

 advantage, and to attend to the minor troubles, 

 A^hich, if left alone, might develop and cause 

 serious difficulty at a critical time. This 

 being so, it is gratifying to find that attention is 

 being given by teachers and writers to farm 

 machinery, and that some of the past neglect is 

 being remedied. 



Mr. Wirt's book will probably prove more use- 

 ful to his own classes than to other teachers. It 

 consists largely of questions that the intelligent 

 student might be asked, and would, indeed, be 

 NO. 2526, VOL. lOl] 



likely to ask himself, but it does not provide the 

 material for answers. It supplies, however, a 

 bibliography which will serve as a guide to other 

 books where more information is given. 



If later editions are called for we should suggest 

 the inclusion of more working diagrams illustra- 

 tive of the main principles of the machine, the 

 right and wrong adjustments, and especially the 

 ways in which the machine may go wrong. 



(5) Mr. Reed's little book on late cabbage is 

 intended for practical men, and it is written in 

 the terse American colloquial style that always 

 appeals to practical men everywhere. The details 

 of cultivation, manuring, insect pests, etc., are 

 sufficiently clear to afford the necessary guidance. 

 The author states with engaging frankness that 

 he grows not only cabbage, but also seed, and he 

 quite rightly emphasises the need for obtaining 

 good seed ; he does not unduly push his wares, 

 however, and his book loses nothing in conse- 

 quence. It is interesting in connection with our 

 present conditions to note that in the author's 

 experience cabbage does well on newly ploughed- 

 up grassland, forming good hearts and needing 

 no nitrogenous fertiliser. On older arable land 

 more fertiliser is required, but not an excessive 

 amount., 



The author keeps rigidly to his title and does 

 not touch on other members of the cabbage 

 tribe, not even the nearly related early cabbage. 

 He shows also that the native-raised seed is fully 

 as good as the imported seed ; on his own land he 

 declares that in the past seven years he has not 

 had less than 20 tons of cabbage per acre, whilst 

 on at least one occasion he has had 30 tons. It is 

 a good idea, which might be further extended, to 

 persuade practical men to write little books on 

 crops which they thoroughly understand. 



E. J. Russell. 



ESSENCES AND VARNISHES. 



(i) Manual for the Essence Industry. By Erich 

 Walter. Pp. iii + 427. (New York: John 

 Wiley and Sons, Inc. ; London : Chapman and 

 Hall, Ltd., 1916.) Price i8s. 6d. net.* 



(2) The Industrial and Artistic Technology of 

 Paint and Varnish. By Alvah H. Sabin. 

 Pp. X + 473. (New York : John Wiley and 

 Sons, Inc.; London: Chapman and Hall, Ltd.,. 

 1917.) Price 165. 6d. net. 



(i) ' I "HE phrase "essence industry" in the title 

 -»■ of this volume covers more than an 

 English reader might at first sight associate with 

 it. In point of fact, the book is a treatise upon 

 the manufacture of most of the things, or in- 

 gredients of things, which are intentionally 

 flavoured, coloured, or perfumed, as a means of 

 preparing them for human use. These include 

 non-alcoholic beverages, such as lemonade and 

 other " mineral " waters ; alcoholic preparations 

 like liqueurs, cordials, and bitters ; flavourings and 

 spices used in baking, cooking, and confectionery- 



