November 25, 1915] 



NATURE 



339 



I 



of a tabloid-press. The g-eneral character of the 

 • ourse is now too well known to call for detailed 

 •lescription. 



In the opinion of the writer, the time is ripe for \ 

 a revision of the optical experiments described in 

 hooks of this type. The Continental form of the ! 

 Tulfrich refractometer suffers from a seriously- : 

 defective form of water-jacketing^, and might with 1 

 .idvantage be replaced (in the text-book as well } 

 IS in the laboratory) by the newer English in- | 

 -^trument, which has been improved greatly in this j 

 respect. Similar statements may be made in refer- i 

 t nee to polarimetric apparatus, in which the ! 

 English makers now enjoy a marked superiority, I 

 which might well find acknowledgment in books | 

 such as those now under review. The time is also 

 ripe for recognising the great technical import- 

 ance of the newer sources of monochromatic light, 

 and the advantages they possess over those 

 formerly in use. The introduction of lithium into 

 the sodium flame and of a globule of mercury into 

 a warmed hydrogen vacuum-tube provide, for use 

 with a refractometer, a series of four lines which 

 is much superior to the traditional series CDFG, 

 which has come down to us from the period when 

 lunlight was still the chief illuminant for optical 

 experiments; the fact that the instrument will 

 leed to be calibrated for these four wave-lengths 

 {e.g., with a crystal of quartz) is a real advantage 

 from the point of view of the training of the 

 student. For polarimetric work the enclosed 

 mercury arc, which has now almost displaced the 

 sodium flame, both in technical and in scientific 

 laboratories, is ripe for description in the text- 

 books ; and it ought to be followed very soon by 

 a description of Dr. Sand's enclosed cadmium 

 arc, the brilliant invention of an P^nglish worker, 

 which promises to revolutionise all those branches 

 of optics which depend on the utilisation of power- 

 ful sources of monochromatic light. It is curious 

 that both authors should be content with jacketed 

 polarimeter tubes in which only about three- 

 quarters of the liquid is under the direct control 

 of the circulating water. 



(3) Mr. Berry's "Volumetric Analysis" repre- 

 sents a distinct advance upon most of the smaller 

 books on the subject, though its advantages are 

 largely neutralised by the very high price which 

 is charged for a volume of less than 140 pages. 

 The method of treatment is more scholarly than 

 is usual in a small text-book, and the inclusion 

 of a chapter on the "Theory of Indicators," based 

 on Mr. Tizard's well-known report, affords wel- 

 come recognition of the scientific aspects of the 

 subject. If issued at half the present price the 

 book could be commended heartily for general use 

 in the many laboratories in which volumetric 

 analysis is now taught. 



NO. 2404, VOL. 96] 



(4) Mr. .Mdridge's book is little more than a 

 skeleton, on which a useful course of elementary 

 chemistry may be built up; but it gives the im- 

 pression that the author is alive to the various 

 educational features that may be embodied in such 

 a course, and the suggestions which he makes 

 should be of real value to other teachers who have 

 not had so long an experience in work of this 

 kind. Specially welcome is the stress which he 

 lays on the full description written by the pupil of 

 his experiments and observations, a description 

 to be written in pencil at the laboratory bench, 

 but written neatly, arranged log^ically, and ex- 

 pressed in the best English which the boy can 

 command. Such an exercise is certainly better 

 than the barren attempt to induce a boy to express 

 in a formal essay pious opinions on a subject of 

 which he has no special knowledge, and in which 

 his interest is often non-existent. 



(5) Dr. Martin's book on " Dyestuffs and Coal- 

 tar Products," issued as the first of a series of 

 manuals of chemical technology, is reprinted with 

 additions from vol. i. of his well-known book on 

 "Industrial and Manufacturing Chemistry," and 

 does not, therefore, call for a detailed review. The 

 sections reproduced deal with the coal-tar indus- 

 try, synthetic colouring- matters, natural dye- 

 stuffs, dyeing and colour-printing, inks, sac- 

 charine and other sweetening chemicals, modern 

 synthetic drugs, and photographic chemicals. The 

 reproduction of these articles is very opportune 

 at the present time, and will be generally wel- 

 comed. T. M. L. 



OUR BOOKSHELF. 



The Principles of Agriculture through the School 

 , and the Home Garden. By C. A. Stebbins. 



Pp. xxvi + 380. (New York: The Macmillan 



Co.; London: Macmillan and Co., Ltd., 1913-) 



Price 45. 6J. net. 

 " Daisies growing- a girl " is the title of the 

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 Such is " school-gardening- " as actually carried 

 out in the Western States to-day. 



We wish that every school teacher in this 

 country could read this volume. Every page is 



