I50 



NATURE 



[June 15, 1905 



breaking down of the insulation. The production of 

 ozone — the forerunner of the above effect — is a matter 

 of the utmost importance to electrical engineers, 

 especially in damp climates. 



That portion of the book dealing with varnishes 

 is most valuable. The pros and cons, of the use of 

 linseed oil, which undoubtedly has a very extended 

 use at the present time, and other acid bodies are 

 well set forth, as are those of the use of insulators of 

 paraffin origin. The uses to which oils can be put as 

 insulators, their various characteristics, their purity 

 and methods for purifying and drying are carefully 

 dealt with. Presspahn-mica is advocated instead of 

 micanite for high tension working. 



An important part of the w'ork is that which deals 

 with insulation of armatures, field-coils, and trans- 

 formers. It is well shown upon what the so-called 

 " space-factor," that is the ratio of area of copper to 

 gross area of slot, depends. Very valuable sugges- 

 tions are made with regard to pressure tests. Long 

 time high pressure tests are likely to injure apparatus, 

 and are not recommended — a few seconds' application 

 is suflicient. The appliances in use for taping and 

 handling insulation material, and a most interesting 

 description of the tools employed, together with a 

 useful bibliography, close what is really a valuable 

 book. The printing is good, and the illustrations are 

 excellent. Ernest Wilson. 



Insect Life. A Sliort Account of the Classification 



and Habits of Insects. By Fred. V. Theobald, 



M.A. With numerous illustrations (53 in the text). 



Second edition, revised. Pp. xi + 235. (London : 



Methuen and Co., 1905.) Price 25. 6d. 



The first edition of this work was published in 1896, 



and the public interest in entomology is evidenced by 



the increasing number of books on the subject which 



reach a second edition within a comparatively short 



time of publication. A cheap popular illustrated book 



on insects seems at present to be assured of a sale 



at least sufficient to cover expenses, which was not the 



case a few years ago. 



The second edition is exactly similar to the first as 

 regards its size, illustrations, and general contents ; 

 but here and there we notice occasional additions. 

 There is much useful information in the book, but we 

 regret that the second edition has not been more 

 carefully revised, for, apart from occasional misprints, 

 several erroneous or obsolete statements contained in 

 the first edition have been repeated in the second. 

 Thus on p. 3 (note) we read, " The total number 

 [of^ insects] described, however, is under 250,000." 

 This is probably based on Kirby's estimate' in his 

 "Text-book of Entomology" (1885) of 222,000; but 

 the later estimate given in the second edition (1892) 

 was 270,000, which would require to be augmented 

 by many thousands to be correct for 1905. On p. 87, 

 " The so-called Apples of Sodom found near the Red 

 Sea," should, of course, be the Dead Sea. While it is 

 true, as stated on p. 105, that Danaus chrvsippiis is 

 the only European species of the genus, the much 

 larger insect occasionally found in England is the 

 common North .American"!), erippus (or D. arcliippus), 

 introduced, but which mav not improbably become 

 n.-ituralised in Europe, and has established itself 

 within the last half-century in many of the 

 Pacific Islands, as well as in Australia and New 

 Zealand. Lastly (p. 166), it is possible that the bite 

 of the species of tsetse fly which destroys cattle in 

 South Africa may be " comparativelv harmless to 

 man"; yet, as Mr. Theobald must certainly know, 

 the terrible sleeping sickness of Western and Central 

 .■\frica is now ascribed to the bites of different species 

 of tsetse flies infesting those regions. 



\A'e hope that when" this little book reaches a third 

 NO. 1859, VOL 72] 



edition Mr. Theobald may have an opportunity of 

 enlarging it, for entomology, like other sciences, 

 advances so rapidly that it is not possible to bring it 

 up to date, unless the author gives himself a free 

 hand in this direction. 



The Radial Area-Scale. Patented by R. W. K. 



Edwards. (Richmond, Surrey: Morgan and Kidd.) 



Price 3i. 6d. 

 This ingenious instrument is designed for use in find- 

 ing the approximate areas of irregular plane figures 

 such as indicator diagrams. It consists of a sheet of 

 transparent celluloid marked with eleven scales on 

 lines radiating from a point at equal angular intervals 

 of about 3°, and so divided that a scale reading is pro- 

 portional to the area of a sector from the centre up to 

 that point. When used, the sheet is laid over the figure 

 to be measured, and is adjusted until the figure is just 

 contained within the bounding radials, with its outline 

 cutting the nine inner scales each in two points. The 

 outer and inner readings at these points are now taken 

 and the two sets added; the difference between the 

 two sums gives the required area. The entire opera- 

 tion occupies about three minutes. Applied by the 

 writer to a 3" circle and a 6" semicircle, the results 

 were correct in both cases to within J per cent. As 

 the outside radials include an angle of about 30°, the 

 instrument is quite quickly adjusted over large or 

 small figures of any shape, and the scales are clear 

 and easy to read. To ensure a good approximation, 

 Simpson's rule has been cleverly applied in figuring the 

 scales. The instrument seems likely to be of consider- 

 able service, and should be widely known. 



.4 Preparatory Course in Geomelry. By W. P. Work- 

 man and A. G. Cracknell. Pp. viii + 56. (London : 

 W. B. Clive, 1905.) Price gd. 

 The little book by Messrs. Workman and Cracknell 

 is preparatory to a forthcoming work on " Geometry, 

 Theoretical and Practical," on which the authors are 

 now busily engaged. It consists essentially of a set 

 of exercises on the accurate scale drawing of lines, 

 angles, triangles, and polygons, and requires the 

 reading off of quantitative results as regards lengths 

 and angles. Areas, ratios, and the general proper- 

 ties of circles are not reached in this volume. It 

 trains the youth in the proper use of the drawing-pencil, 

 straight-edge, scale, protractor, set-square, and com- 

 pass, and gives him a concrete knowledge of, and prac- 

 tical Insight into, geometrical truths as a preliminary to 

 more formal work. Teachers using the book would 

 do well when valuing class work to act on a sugges- 

 tion contained therein, and give varying credit accord- 

 ing to the degree of accuracy disclosed by the results. 

 The book gives good promise of another very interest- 

 ing class book of elementary geometry. 



The Evolution, of the World and of Man. By George 

 E. Bo.xall. Pp. xi+191. (London: T. Fisher 

 LInwin, 1905.) Price 5s. 

 .\ SINGLE example to show how Mr. Boxall proposes to 

 supplemerit the deficiencies in the story of evolution as 

 told by science will enable possible readers to estimate 

 the value of his book. On p. 30, after stating that 

 geology tells us the order in which various strata 

 were laid down, he continues : — " but no attempt has 

 as yet been made to estimate the temperature, for 

 instance, when the granite was first deposited, and 

 yet this should not be a difficult problem to solve. 

 Thus, of the true metals, aluminium is the only one 

 which appears in the granite, ..." and the account 

 continues with the same disregard of scientific fact. 

 Mr. Boxall expresses his own view of the value of 

 the book by not troubling to provide an index to it. 



