298 



NA TURE 



[January 24, 1901 



On chucks and mandrils our author has much to say, 

 and useful advice is given on how to centre work for the 

 lathe, the book concluding with a chapter on screw- 

 cutting of a rudimentary nature, sufficient, however, to 

 give the amateur a good start in this somewhat difficult 

 subject. 



Taken as a whole, the little book will be of much use 

 to the young apprentice and amateur. It flavours more 

 of the workshop than of the technical school, which is 

 very much in its favour. 



Principles of Plant Culture. By Prof. E. S. Goff. 



Second Edition. Pp. 287. (Wisconsin : Madison. 



Published by the Author, 1899.) 

 Many of our county councils have now instituted 

 training colleges for teachers, and laboratories for the 

 instruction of pupils in the elements of agriculture and 

 horticulture. In such establishments Mr. GofiPs little 

 treatise, which is now in a second edition, will be most 

 useful. The phenomena of the life of plants are clearly 

 explained, and tlie details of internal structure sufficiently 

 set forth. The application of these facts to the practical 

 details of cultivation is shown, and stress laid upon the 

 conditions that are propitious, as well as on those that are 

 adverse, to plants. Numerous illustrations are given and, 

 as an appendix, is provided a syllabus of laboratory work 

 containing directions whereby the pupil may be assisted 

 in realising for himself the teachings of the text. 



It is a book suitable not only for those who have the 

 advantage of access to a laboratory, but also for those 

 who have to acquire a knowledge of plant-life without the 

 assistance of a teacher 



Photography in Colours. (Photography Bookshelf, No. 5.) 

 By R. Child Bayley. Pp. 74. (London : Iliffe, Sons 

 and Sturmey, Ltd., 1900.) 

 There are probably many people who wish to obtain a 

 general survey of the different attempts that have been 

 made to solve the fascinating problem of " photography 

 in colours" without necessarily entering deeply, or at 

 all, into the practice of any one or more methods. 

 Every one who practises photography should, however, 

 have an intelligent idea of the various processes in use, 

 even if such knowledge amounts to a mere outline of 

 the principles involved. Until now there has been no 

 book devoted to such a summary, so the one before us 

 is very welcome for filling such a gap in our literature. 



The author has naturally avoided all technicalities, 

 and confined himself strictly to the explanation of the 

 fundamental principles on which each method is based. 

 The book, it may be mentioned, originated from the 

 editorial articles written by the author for Photography., 

 which have been revised and published in this handy 

 form. 



The Romance of the Earth. By A. W. Bickerton. Pp. 



181. (London: Swan Sonnenschein& Co., Ltd., 1900.) 



Price 2s. 6d. 

 This is an attempt to trace, in a popular manner, the 

 history of the earth from the time it had a separate 

 existence to the present, together with that of its fauna 

 and flora. As giving an idea of the subjects touched 

 upon it may be mentioned that among the titles of the 

 various chapters are "The Beginning of the Earth," 

 "Earth-Sculpturing," " Ice- Ages," "Evolution," "Em- 

 bryology " and " Organic Ascent." In order to make the 

 story a connected one, the author admits that where 

 facts have not been available he has permitted himself 

 "to speculate, to make deductions from the accepted 

 laws of nature." To this there could be no objection 

 had some clear indication been given whereby the reader 

 might distinguish the generally accepted ideas from the 

 personal views of the author. Still, the book is well 

 written and appropriately illustrated, and provides an 

 interesting first course of reading on some of the greater 

 problems of science. 



NO. 1630, VOL. 63] 



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 Nature. 

 No notice is taken of anonymous communications,^ 



Directions of Spirals in Horns, 

 The direction of the spiral in the horns of Bovidse is, I think, 

 a less simple matter than might be inferred from Mr. G. 

 Wherry's interesting note in Nature for January 10, p. 252 ; at 

 all events so far as sheep and goats are concerned. 



The only wild goat with truly spiral horns is the markhor, 

 Caprafakoiteri, in all varieties of which the spiral is, as Mr. 

 Wherry states, " crossed " (right horn twisting to left, left horn 

 to right), but in the great majority of tame goats the reverse is 

 the case, the horns being " homonymous." This was pointed 

 out to me many years ago by the late Edward Blyth, and I 

 have been able to confirm his observations repeatedly in coun- 

 tries where tame goats abound, both in India and in North-East 

 Africa. The rule is not without exceptions, a few tame goats 

 having horns coiled like the wild markhor. I have already 

 called attention to these facts in the " Fauna of British India, 

 Mammalia," p. 508. The " homonymous " spiral in tame goats 

 is the more interesting because it is probable that most of them 

 are derived from the wild Capra aegagrus, which has horns 

 curving backwards, not spiral. 



As regards sheep, the horns in all the Ovis ammon group, in- 

 cluding O.poli, are "homonymous," as Mr. Wherry says. But 

 the bharal, Ovis nahura, has its horns arranged on the reversed 

 or " crossed " system. It is true that the bharal is in some othei 

 respects intermediate between sheep and goats. 



W. T. Blanford. 



The "Usefulness" of Science. 



In your interesting article on "The New Century" in the 

 January 3 number of Nature, I notice that you endorse M. 

 Levy's account of the usefulness of " useless " studies and even 

 proceed to suggest that " all our progress has come from the 

 study of what was useless at the time it was studied." Now 

 while fully agreeing with your main argument, it seems to me 

 that this goes too far. Certainly M. Levy's illustrations do not 

 prove it. For it so happens that the early astronomical 

 observations, to which he appeals, so far from being useless in 

 the eyes of those who made them, were believed to be of the 

 utmost practical importance. In fact, it may be doubted 

 whether the study of astronomy has ever again been prosecuted 

 in so directly utilitarian a spirit as in its infancy. For, quite 

 apart from the practical need of determining the succession of 

 the seasons, which M. Levy seems to have strangely overlooked, it 

 was generally believed that the observation of the heavenly bodies 

 was "useful" as a method of forecasting terrestrial events. 

 Astronomy was the offspring of astrology, and assiduously 

 practised because no distinction had yet been made between 

 those heavenly bodies which made great practical differences to 

 human affairs, like the sun and the moon, and those whose 

 influence was inappreciable. Furthermore, it must be re- 

 membered that these same bodies were regarded as literally 

 deities of the highest order, so that their observation was a 

 religious rather than a scientific act. This veneration of the 

 heavenly bodies, moreover, persists throughout Greek science, 

 and even Aristotle regards them as composed of a purer and 

 diviner material than anything " sublunary." So that, when he 

 advocates the "useless" Oecopia of astronomy and mathematics 

 as the highest exercise of human faculty, he does not mean 

 " seek knowledge for its own sake," but rather ''raise yourself 

 to the contemplation of what is nobler and diviner than any- 

 thing earthly." For the eternal and immutable truths of 

 mathematics also were regarded as being of more than human 

 validity. Hence it seems a mistake to call these primitive 

 researches useless because we do not happen to believe in the 

 use they were supposed to have. 



And this suggests a further scruple. Does not the doctrine that 

 the " useful " discoveries arise out of the study of the " useless " 

 come perilously near to a psychological paradox ? For how can 

 any one rationally pursue the study of what he at the time con- 

 ceives to be useless ? It must at least be useful to him, i.e. satisfy 

 his desires in some way or other. In the last resort, what can the 

 useful be but that which satisfies some human desire, subserves 



