March 17, 1898] 



NATURE 



463 



before his death, that he obtained his C.B. and knight- 

 hood. His memory has been perpetuated in that branch 

 of the profession which he so adorned by the estabUsh- 

 ment, at Netley, of the Martin Memorial Gold Medal, 

 which is presented to the surgeon on probation who 

 takes the highest place in military medicme at the final 

 competition. The biography is exceedingly pleasant 

 reading, and the author has done well to incorporate in 

 it letters from many interesting persons to Sir Ranald, 

 and also some extracts from official documents, in the 

 compilation of which he was concerned. F. W. T. 



The Chemistry of the Garden : a Pritner for Amateurs 

 and Young Gardeners. By Herbert H. Cousins, M.A. 

 Pp. XV -I- 141. (London : Macmillan and Co., Ltd., 

 189S.) 



This little book is very clearly and pleasantly written. 

 It contains much valuable practical information respect- 

 ing garden soils, the use of artificial manures in horticul- 

 ture, the preparation and application of effective fungi- 

 cides and insecticides, and various other matters. The 

 book is designed for the use of persons who have not 

 received a scientific education, and we should think it 

 will exactly meet their wants ; there is, however, much 

 m it that will well repay the perusal of a higher class of 

 readers. There are a few minor points which seem open 

 to criticism. " Pod-plants " is not a good distinctive 

 name for the papilionacece, as the cruciferce are also 

 podded. The popular use of the word "germ," as de- 

 scriptive of certain races of living beings, should surely 

 be discouraged as fundamentally incorrect. Nor is there 

 any advantage gained by speaking of" muriate of potash," 

 though the term still lingers in commerce. If a person 

 who knows nothing is to be taught, it is surely needless 

 to burden him with archaisms which he must unlearn 

 if his education proceeds any further. Agricultural 

 chemists will, we think, demur to the same valuation 

 being applied to the nitrogen of ammonia and to the 

 nitrogen of insoluble organic manures. R. W. 



77;,? Naturalisfs Directory., 1898. Pp. 125. (London : 

 Upcott Gill, 1898.) 



The sub-title explains that this book is " for the use of 

 students of natural history, and collectors of zoological, 

 botanical, or geological specimens, giving the names and 

 addresses of British and foreign naturalists, natural 

 history agents, societies and field clubs, museums, 

 magazines, &c." The volume is more remarkable for 

 what It omits than for what it includes, and disappoint- 

 ment will be saved by not referring to it for the addresses 

 of well-known naturalists. 



Ttte Teacher's Manual of Object-Lessons in Domestic 

 Economy. By Vincent T. Murche. Vol. i. (Standards 

 I. and II.) Pp. 250. (London : Macmillan and Co., 

 1898.) 



This manual is, the preface informs us, "designed 

 primarily to meet the requirements of the Education 

 Department in the Class Subject of Domestic Economy, 

 as laid down in the Code for 1897." It will be service- 

 able to the teacher in indicating what to show, do, and 

 describe during object-lessons on materials used for 

 food, and it contains a large amount of clearly explained 

 and well-arranged facts about common things. 



Storm and Sunshine in the Dales. By P. H. Lockwood ; 

 with a preface by H. G. Hart. Pp. 94. (London : 

 Elliot Stock, 1898.) 



A BOOK containing many personal observations on out- 

 door nature, expressed simply and sympathetically. The 

 author is a fervent admirer of the natural beauties of 

 Yorkshire dales, and his descriptions may lead others to 

 share his enthusiasm, notwithstanding the fact that the 

 scenes he depicts are mostly "glimpses of the obvious." 



NO. 1 48 I, VOL. 57] 



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 fc^r this or any other part of NATURE. 

 No notice is taken of anonymous coinmunicattons.'\ 



A Dust Shower. 



Paragraphs have recently appeared in several of the daily 

 papers to the effect that a dust storm had been encountered off 

 the west coast of Africa by the mail steamer Roslyn Castle, and 

 that the dust had fallen on the deck for 900 miles. I was 

 fortunate enough to secure a sample of this dust, which actually 

 fell on the deck, with the following note affixed : — 



" Ship covered with fine red dust off west coast of Africa. 

 Lat. 22-5 N. Long. 1725 W. February 15, 1898." 



" Dust fog encountered with for 900 miles. February 18, 

 1898." 



This dust is extremely fine, and consists chiefly of minute 

 grains of quartz and flakes of brown mica, some of the former 

 being well rounded. 



I cannot find any trace of glass or other thing to suggest a 

 volcanic origin to the dust ; but it is undoubtedly a very fine 

 sand, in all probability derived from the Sahara, although no 

 mention is made of the direction of the wind when the dust fell. 



Although cases of volcanic dust being transported for long 

 distances are fairly frequent, those of sand appear to be less so. 



Sir A. Geikie ("Text-Book of Geology," p. 337) mentions 

 two cases of the transportation of sand from the Sahara ; in 

 the first instance it fell in the Canaries, in the second it was 

 traced as far as Boulogne-sur-Mer. In the present case the 

 distance of transport is probably greater than the one, and less 

 than the other. C. St. A. Coles. 



The Solution of Quadratic Equations. 



Ix your issue of Februarj- 24 a review appears of " Chambers's 

 Algebra for Schools." Your re%'iewer concludes with a lament of 

 the probable uselessness of protesting against the method of 

 solving quadratics by "completing the square." 



Vour reviewer might do something towards removing this 

 "national fetish" if he would explain what method is taught 

 elsewhere, to replace this out-of-date procedure. Before this 

 vigorous onslaught, I feel ashamed to confess that I can recall no 

 general elementary method, that does not depend on the com- 

 pletion of the square. 



In my desire to free myself from a possibly antiquated " cult," 

 I am, however, willing to undergo this humiliation, in the hopes 

 that I and others may be brought more on a level with the 

 times. E. CuTHBERT Atkinson. 



Rugby, March 6. 



In answer to Mr. Atkinson's letter, I will explain, as briefly as 

 I can, what appears to me to be the proper way of discussing 

 quadratic equations. 



As soon as the pupil can easily factorise such an expression as 

 ;r- - 5jr + 6 into the product {x - 2) (_x - 3), it is not ver)' 

 difficult to make him see that 2 and 3 are the only values of x 

 which make x"^ - 5*^ -h 6 equal to zero ; or, in other words, 

 that the equation .r-* - 5^- -f 6 = o can be solved when the 

 expression on the left hand has been factorised. 



It is exceedingly important that the factorising of polynomials 

 and the solution of equations should be treated as cognate, or 

 rather equivalent problems. A quadratic equation should always 

 be reduced to the form ax"^ -^r bx -^ c — o : then the expression 

 on the left-hand may be factorised by inspection, or else multiplied 

 by such a quantity that the result can be conveniently expressed 

 as the difference of two squares ; 4a (that is, four times the co- 

 efficient of x'^) will always do, sometimes a smaller number. 

 This should be illustrated by numerical examples : for instance, 

 if the equation is 2x^ + 3^: - 7 = o, multiply by 8 : then 

 l6.r" + 24r — 56 = o, that is {^^x -(- 3)-' - 65 = o, and 

 jf = i( - 3 ± \^65). When a boy is able to appreciate general 

 formulae, he may be led to see that 



4^ {ax- -f- ^j: -t- c) = {zax -J- bf - {ir - Sflc) = 



(2aar-f bf - (V^ -Aficf 



and hence to use the " solution by formula " when he cannot 

 find the roots by inspection. 



