39Q 



NA TURE 



[February 26, 1903 



knowledge or the range of practical experience re- 

 quisite for the task he has undertaken. He attempts 

 within the narrow limits of eight chapters running to 

 286 pages— of which one chapter of only sixteen pages 

 is devoted to " maintenance "—to deal with such great 

 subjects as the manufacture of steel and iron ; the 

 quality, strength and tests of these materials; the 

 classification of ships and the assignments of their 

 loadlines ; the various methods of ship construction ; 

 the strength of ships and the stresses to which they 

 are subjected at sea; the types of ships and the con- 

 struction of typical vessels ; the details of construction 

 of ships and their fittings; and the maintenance of 

 ships during their employment at sea. These are all 

 most important subjects,' and greatly need adequate 

 treatment by someone who thoroughly understands 

 them and can make them understood by others. Mr. 

 Watson has certainly failed to do what is required. 



The various points are treated in this work chiefly 

 with reference to cargo steamers built to Lloyd's 

 rules, and there is little in some of the chapters ex- 

 cept what is contained in those rules. The " laying 

 off " of a vessel upon the mould loft floor, and the 

 manner of giving out particulars of the forms of the 

 various parts of the structure to the workmen, is 

 described in two pages, in a general manner that 

 conveys no really useful information. Similarly, the 

 launching arrangements, and the calculations requisite 

 for them, are only glanced at in a very brief and 

 sketchy manner. The subject of bilge keels is dealt 

 with in twenty lines, and the question of how to place 

 these properly in position upon the ship is dismissed 

 with the remark that they " should be placed so as 

 to give the least possible resistance to propulsion." 

 A student would like to have some guide to that 

 position ! In dealing with the subject of vibration 

 of steamships, the author recommends, as a provision 

 against it, the strengthening of parts of the structure 

 in and near the engine-room ; and he makes no re- 

 ference to the most important precaution of all — 

 which has been much studied of late by marine 

 engineers — that of designing the engines so as to 

 obtain as perfect a balance as possible of the recipro- 

 cating parts. 



The chapter upon " Stress and Strength " is very 

 unsatisfactory, owing to an apparent want of scientific 

 grasp of this difficult and intricate subject. We hope 

 that the " shipbuilders, ship superintendents, students 

 and marine engineers " for whom this work is said 

 to be intended will soon be supplied with fuller and 

 more exact information than is here presented to 

 them. 



Elementi di Gcografia Fisica, Fisica Terrestre e Meteor- 

 ologia, ad uso delle Scuole Classiche, Tccniche, Nor- 

 mals cd Agrarie. By 'Prof. Francesco Porro. 

 Pp. viii + 2S0. (Turin, Rome, &c. ; G. B. Paravia 

 & Co., 1902.) 



Prof. Porro dedicates his little book " a mio figlio 

 Giannino," a distinct novelty in school-book prefaces. 

 The book itself devotes more space to the atmosphere, 

 the oceans and glaciers than is usual in elementary 

 works on physical geography. The features of the 

 land are dealt with in much less detail, while the 

 usual introduction on astronomical matters one ex- 

 pects to find in an English school book of the kind, 

 and the usual appendix on biological matters, are 

 omitted altogether. The result is that it is possible, in 

 a limited space, to give a very satisfactory outline 

 of the departments which are selected for treatment. 



NO. 1739, VOL. 67] 



Prof. Porro writes as a lover of nature, with a 

 subdued enthusiasm that should prove contagious. 

 He has a good knowledge of the literature of his 

 subject, makes his references accurate, and knows 

 how to choose really instructive photographs and to 

 construct helpful diagrams as illustrations. 



H. R. M. 



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.} 



Cambridge Mathematics. 



Prof. Greeniiill's notice (p. 338) of the German transla- 

 tion of my " Calculus " is pleasant enough reading. He says 

 I follow the method of Squeers, " Spell winder ! Now go and 

 clean it." He is nearly right, but in truth 1 act on the belief 

 that the average English boy loves to learn by doing things 

 first and thinking about them afterwards, and so my method 

 is rather the reverse of that of Squeers. Again, " the book, 

 as a series of events connected by a slight thread of con- 

 tinuous theory, suggests a mathematical Pickwick." This 

 is acute and severe and good humoured and kindly. I hope 

 that Cambridge men, as they believe in Prof. Greenhill I's 

 great knowledge and good sense, will also see his kindly 

 feeling, and that they will not think me presumptuous in 

 urging them to consider his advice seriously. It will be 

 gathered that I do not myself think that my course of 

 mathematics for engineers is more than a promising effort. 

 I am very much alive to its defects. But I know that the 

 idea on which I have been working is a good one ; I carefully 

 developed tha't idea in opening the discussion at the Glasgow 

 British Association meeting (published by Messrs. Mac- 

 millan). It is an idea as well known as the commonest copy- 

 book maxim, but it is as much ignored at our colleges and 

 schools as the sixth and eighth Commandments were in 

 Blackbeard's ship. Anyone who studies how Prof. Forsyth 

 has transformed my copy-book-maxim-ideas of elementary 

 mathematics teaching so that they have become acceptable 

 to all the schoolmasters of the country, and have in a few 

 months been adopted by many examining bodies, must see 

 that it is useless for anybody outside Cambridge to do more 

 than say more and more strongly and persistently how much 

 Cambridge is ignoring certain obvious truths ; how Cam- 

 bridge is neglecting its duty of leadership of this country in 

 mathematics teaching. 



I have pointed out how the engineer needs mathematics 

 in all his work ; how he needs the ideas of the infinitesimal 

 calculus, and yet how mathematical symbols have been made 

 hateful to him, his very desire for mathematical knowledge 

 having in many cases been taken a devilish advantage of 

 by self-sufficient dull pedants. How the engineer, clear- 

 eyed and eager to use tools which he knows by trial will 

 never fail him, and scornful of all method which he has by 

 trial found to be mere pretence, has got to loathe mathe- 

 matics and theory ; — is it not written in the pages of every 

 engineering journal that is published? And yet we know 

 that all engineering is built upon mathematics, that all great 

 advances in engineering are made by those practical en- 

 gineers who accidentally become able to compute, to use the 

 more celestial weapon. When, as at the Royal College of 

 Science, there is an endeavour made to construct a syllabus 

 suitable for the mathematical instruction, not merely of the 

 average, but also of the highest kind of engineer 'and 

 physicist, the necessity for making sacrifice and obeisance 

 to outside standards well-nigh defeats our efforts. We ask 

 Cambridge to help us towards that freedom' without which 

 there can be no true education. 



Cambridge leads England in mathematics, and she is at 

 present very far, not only from my ideal of leadership, but 

 also from the ideal of Prof. Greenhill, who knows the state 

 of the mathematical world many times better than I do. 

 I ask Cambridge men, our best mathematicians, the men 



