March 28, 19 18] 



NATURE 



making- ; and essences used for the manufacture 

 of perfumes, dentifrices, and other toilet articles. 



Most of the flavouring- substances employed in 

 our beverages and foodstuffs are derived from 

 plants, in which they usually exist ready-formed. 

 The art of the essence-maker consists in transfer- 

 ring- these flavours from the plant to a medium 

 by which they can be readily conveyed to the 

 potable or edible final product. The transfer may 

 be a simple mechanical one, as when fruit juices 

 are added directly to beverages. On the other 

 hand, the essential principle of the flavouring sub- 

 stance may first have to be separated from the 

 plant, as when the volatile aromatic oils {e.g. 

 peppermint) are distilled oft" in a current of steam. 

 These distilled oils may then be employed directly 

 as flavouring agents, but, as a rule, they are more 

 <:onveniently first dissolved in alcohol. Such 

 solutions form one kind of "essence." Most fruit 

 flavours, however, are too delicate for isolation in 

 this way, and are obtained by distilling the fruit 

 itself with alcohol, yielding another kind of 

 essence. " Every fruit essence is only a diluted 

 transfer of the volatile flavour of the fruits to 

 alcohol." The same remark holds good for the 

 floral odours which go to make perfumery. 



The book under notice treats of the various 

 Avays in which this transference of flavours and 

 odours from source to product is best effected. It 

 opens with a dissertation on the sense of taste ; 

 this would be improved in parts if specific ex- 

 amples were given to illustrate the author's mean- 

 ing. The following- chapters deal clearly and 

 concisely with the principles and practice of the 

 industry. Fundamentally it is a "chemical" in- 

 dustry ; hence a section of the book is rightly de- 

 voted to the laboratory. The theoretical chemistry 

 of the products is not dealt with; but analytical 

 methods and the general chemical control of the 

 manufacturing operations make up a useful 

 chapter, 



A very large number of formulae are supplied, 

 and the systematic arrangement of these is a com- 

 mendable feature. The British reader will need 

 to bear in mind that the values of the alcoholic 

 strengths and of the gallon used are those current 

 in the United States ; with this proviso, he will 

 find the work a very useful one for the industry 

 in question. 



(2) Readers who are acquainted with the first 

 ■edition of Mr. Sabin's work will remember that 

 the author is an enthusiast on all matters pertain- 

 ing to paints and varnishes. His book, conse- 

 ■quently, has the quality of readableness usually 

 found in the work of one who knows his subject 

 and writes as if he loves it, even though that sub- 

 ject may not at first sight appear a particularly 

 attractive one. Naturally, this quality is shown 

 more especially in the historical portions of the 

 book, but it is by no means absent from the more 

 technical chapters. 



For example, Mr. Sabin is discussing the var- 

 nish on Egyptian mummy-cases, and arguing- for 

 the antiquity of recipes substantially like some in 

 tise at the present day. " Here is the varnish, just 

 NO. 2526, VOL. lOl] 



as it was applied twenty-five hundred years ago. 

 It is just as real as the mummy itself, and is just 

 as absolute a proof that varnish was made in those 

 days as the mummy is proof that people lived in 

 those days. Here, I say, is the actual and real 

 varnish. It was made with resin and oil. It was 

 smeared on, possibly with a spatula, but more 

 likely with the fingers, certainly not put on with 

 a brush. Such a varnish as Theophilus describes 

 would look as that looks, and in all probability 

 would last as that has endured." 



It is some twelve years since the first edition 



was published. The most important change in 



j varnish-making during that period has been the 



' introduction of tung oil, a product which has a 



remarkable power of rapid drying. The author 



I believes, however, that the tung-oil varnishes are 



! by no means so durable as the former oleo-resin 



products which they have so largely displaced. He 



notes that the general appearance of furniture and 



railway and other carriages has grown worse 



rather than better (in America) during the last 



ten years. 



The author has some interesting remarks to 

 make about violin varnish. He does not believe 

 that spirit varnishes were ever used by the great 

 violin-makers. Old violins appear always to have 

 been coated with an oil-resin varnish. One valu- 

 able old instrument which he examined had a var- 

 nish which he concluded must have been made 

 with at least 35 gallons of oil to 100 lb. of resin. 

 If he were called upon to make a special varnish 

 for violins, it would be, he says, a simple amber 

 varnish with 35 or 40 gallons of raw linseed oil 

 (to 100 lb. of amber). 



Mr. Sabin writes from the American point of 

 view, and disclaims any special knowledg-e of 

 English practice ; but his general outline of the 

 principles involved in paint and varnish technology, 

 and many of the applications of those principles 

 which he describes, will hold good on both sides 

 of the Atlantic. C. S. 



OVR BOOKSHELF. 



Hand Grenades: A Handbook on Rifle and Hand 



Grenades. Compiled and illustrated by Major 



Graham M. Ainslie. Pp. v-f 59. (New York : 



John Wiley and Sons, Inc. ; London : Chapman 



and Hall, Ltd., 1917.) Price(65. net. 



The introduction states that hand grenades were 



in use until about the end of the seventeenth 



century, when they fell into disuse. It has been 



stated that they were used by the defenders of 



Mafeking. In the Russo-Japanese War they were 



employed, and became important weapons in the 



present war, where " it was proved that under 



many conditions infantry armed only with rifle and 



bayonet found it impossible to press home an 



attack or hold a position ag-ainst troops armed 



with grenades." This little book' is the result of 



experience in the present war. 



Following the "brief summary of the various 

 grenades, with instructions for preparing and 



