248 



NA TURE 



[January 14, 1892 



«.nd processes are treated with a clearness, conciseness> 

 and completeness that make the book a delight to read* 

 and although, as he says, " my aim has not been to in- 

 troduce novelties," yet he has succeeded, in so far as we 

 are able to predict, in placing before students a book not 

 •only of practical utility, but also of great educational value. 

 Stocks and shares, and such like transactions, have all 

 been treated more in accordance with the methods of 

 the present day than is usual in such treatises. There 

 has also been inserted a chapter on foreign exchanges 

 for the benefit of those preparing for examinations in 

 commercial arithmetic. The examples are of a varied 

 and useful nature, and are numerous and well chosen : 

 each new principle or process is accompanied with 

 one or two sets of them, while interpolated through- 

 out are many to be worked out by those who wish to 

 revise their back work as they proceed in the subject. 

 Miscellaneous exercises to the number of 500, together 

 with sets of examination papers, form also a useful 

 addendum. W. 



Journeys in Persia and Kurdistan. By Mrs. Bishop 

 (Isabella L Bird). Two Vols. With Portrait, Map, 

 and Illustrations. (London: John Murray, 1 891.) 

 This work consists of letters written in the course of the 

 second half of journeys in the East which extended over 

 a period of two years. The author had intended, in the 

 event of their being published, to correct them by refer- 

 ence to notes made with much care. Of these notes she 

 was robbed, and she refers to the loss as her "apology to 

 the reader for errors which, without this misfortune, 

 would not have occurred." Perhaps, however, the book 

 is all the better for being presented essentially in the 

 form in which it was originally written. The record of 

 the writer's impressions has thus a directness, simplicity, 

 and freshness of which it might to some extent have 

 been deprived by elaborate revision. Mrs. Bishop does 

 not profess to have written a book on Persia and Eastern 

 Asia Minor. She has merely set down what she herself 

 saw during her travels in those countries. But she has 

 done this so well that ordinary readers are not likely to 

 resent the slightness of her references to the administra- 

 tion of government, the religious and legal systems, the 

 tenure of land, and the mode of taxation. The illustra- 

 tions are very good, and add considerably to the interest 

 of the narrative. 



A First Book of Electricity and Magnetism. By W- 



Perren Maycock, M.Inst.E.E. (London: Whittaker 



and Co., 1891.) 

 The scope of this work is limited to the syllabus of the 

 elementary stage of the Science and Art Department. 

 It is intended as an easy introduction to many of the 

 text-books now in use, which, although termed ele- 

 mentary, are of rather too advanced a nature for some 

 students to commence with ; the author considering that 

 they might be led to "take a greater interest in their 

 work " by the help of such a book as he has put before us. 



Throughout the three parts, which deal severally with 

 magnetism, electro-kinetics, and electro-statics, the ex- 

 planations are of a plain and simple nature, while the 

 illustrations bring out clearly the various points which 

 they are intended to exhibit. The information is based 

 on the latest ideas ; and interpolated in the text are many 

 questions, the answers to which the student should write 

 out before proceeding beyond them. 



The book will be found really very useful for beginners, 

 and will be to them a good introduction to higher works. 



A Cyclopcedia of Nature Teachings. With an Introduc- 

 tion, by Hugh Macmillan, LL.D., F.R. S.E. (London : 

 Elliot Stock, 1892.) 

 The compiler of this volume has brought together a large 

 number of extracts from various authors, setting forth 



NO. I I 59, VOL. 45] 



what profess to be "facts, observations, suggestions, 

 illustrations, examples, and illustrative hints taken from 

 all departments of inanimate nature." Here is the in- 

 formation offered to us about "the sun-controlled 

 stars " : — 



" When stars, first created, start forth upon their vast 

 circuits, not knowing their way, if they were conscious 

 and sentient, they might feel hopeless of maintaining 

 their revolutions and orbits, and might despair in the 

 face of coming ages. But, without hands or arms, the 

 sun holds them. Without cords or bands, the solar king 

 drives them unharnessed on their mighty rounds without 

 a single misstep, and will bring them in the end to their 

 bound, without a single wanderer." 



This sorry stuff is a fair specimen of a good many of 

 the " Nature Teachings " presented in the " Cyclopaedia." 

 A more suitable title for the compilation would have been 

 " Scientific Gush." The compiler does not always even 

 give accurate titles to his extracts. A passage from one 

 of Mr. Ruskin's writings has the strange heading, " The 

 Star Mercury." 



LETTERS TO THE EDITOR. 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of ^atvthis,. 

 No notice is taken of anonymous communications.'] 



On the Attitudes of the Zebra, during Sleep, and their 

 Influence on the Protective Value of its Stripes. 



Nowadays, when the colours of animals and their uses for 

 the purposes of recognition and protection are forcing them- 

 selves upon the attention of all naturalists, it is not wonderful 

 that an animal so conspicuously marked as the zebra should 

 have commanded a large share of notice. 



Much as it has been considered, however, I do. not think we 

 have yet learned all the lessons that it has to teach us. 



That its bold and vivid stripes should be of immense service 

 for recognition may be accepted as beyond dispute. 



The statement of Mr. Francis Galton, that on a clear moon- 

 lit night these vivid stripes melt into invisibihty, and to an eye 

 not absolutely focussed to the animal itself, but to objects in its 

 immediate vicinity, it is quite unseen, even when so near that its 

 breathing can be heard distinctly, proves most indubitably their 

 immense protective value. As he says, "If the black stripes 

 were more numerous, it would be seen as a black mass ; if 

 white, then as a white one ; but their protection is such as 

 exactly to match the pale tint which arid ground possesses in 

 the moonlight." 



Primd facie, this is hardly what one would have expected, but 

 when pointed out by a competent and trustworthy observer, even 

 a slight knowledge of the laws of light proves it to be true. 



Let anyone notice at what a short dista:ice a lady in a 

 galataa dress with broad stripes becomes invisible in the moon- 

 light, and he will be at once convinced of the truth of Gallon's 

 remark. 



Prof. Henry Drummond further says : — " When we look at the 

 coat of a zebra, with its thunder-and-lightning pattern of black 

 and white stripes, we should think such a conspicuous object 

 designed to court, rather than elude, attention. But the effect 

 in nature is just the opposite. The black and white somehow 

 take away the sense of a solid body altogether, and the two 

 colours seem to blend into the most inconspicuous grey, and at 

 close quarters' the effect is as of bars of light seen through the 

 branches of shrubs. I have found myself in a forest gazing at 

 what I supposed to be a solitary zebra, its presence betrayed 

 by some motion due to my approach, and suddenly realized that 

 I was surrounded by an entire herd, which was all invisible until 

 they moved." By this I understand Prof. Drummond to refer 

 to his observations in the day-time, as Mr. Galton speaks only of 

 the moonlight. 



One can readily see how the shadows of the branches in a 

 tropical forest falling upon the zebras would so intermingle with 

 the stripes of the animals as to add enormously to the difficulty 

 of recognition by human eyes, and also, in the dim light of the 



