3«4 



AA7URE 



[Feb. 26, 1885 



vary inversely as the length ; so that, in similar ships, it 

 would vary inversely as their displacements. In other 

 words, so far as one element of fighting power is con- 

 cerned, and that a very important one, the measure of 

 its amount is not the displacement, as Mr. Barnaby now 

 assumes, but the inverse ratio of the displacement. 



The fighting power of a ship is thus composed of several 

 diverse and independent elements ; and there is nothing 

 approaching to a consensus of professional opinion as to 

 the relative importance of these elements. To assume 

 that they all vary together with the ship's dimensions, or 

 with her weight in tons, is in the highest degree delusive 

 and absurd. The displacement of a ship measures her 

 weight and nothing more. Whether that weight has been 

 effectively and wisely employed in developing a high 

 degree of fighting power, is an entirely independent 

 matter ; and one upon which the whole question of fight- 

 ing efficiency depends. The statement that displacement 

 "always represents power of some kind," merely begs 

 the question. Of course it represents power ; but such 

 power is simply that of displacing water. It may repre- 

 sent that and nothing more, or it may represent in addi- 

 tion the possession of great fighting power, or of other 

 desirable qualities. But the possession of such qualities, 

 and the degree in which they will be developed, must 

 depend entirely upon the skill of the designer — an 

 arbitrary personal factor which is not always limited by 

 the cubic feet of displaced volume that are placed at his 

 disposal. Mr. Barnaby himself pointed out in the paper 

 above referred to, that although the Defence and Vanguard 

 have approximately equal displacements, the latter carried 

 one-half more armour-plating than the former upon three- 

 fourths of the weight of hull ; and was so superior in 

 manoeuvring capability that she would turn completely 

 around in four and a half minutes, whereas the former 

 vessel required seven minutes to complete a circle. This 

 difference in qualities, and superiority in fighting power, 

 of the Vanguard over the Defence is absolutely undis- 

 coverable by merely comparing the displacements. 



All the comparisons we have seen of the fighting powers 

 of modern ships of war and of our own and foreign 

 navies, have been more or less vitiated by the arbitrary 

 standards that have been selected as the basis of such 

 comparisons. The displacement basis is unreliable and 

 misleading, and furnishes no test whatever of fighting 

 power. It would be extremely difficult to devise any 

 simple standard by which the popular mind may be fairly 

 impressed with the relative powers of our own and 

 foreign navies ; while for purposes of exact comparison or 

 of technical discussion no such standard could be re- 

 garded as absolute. Before a simple standard or unit of 

 comparison can be framed, which will be satisfactory or 

 useful, naval officers, artillerists, and constructors require 

 to agree among themselves about the relative importance 

 of the various elements that make up the fighting power 

 of a ship. The defensive values of armour-plating, speed, 

 turning-power, and other protective qualities, and also the 

 offensive values of the gun and torpedo armaments, the 

 ram, speed, &c, require to be separately evaluated and 

 their relative importance determined. If a general agree- 

 ment could be arrived at as to the relative approximate 

 values of each of these independent elements of offensive 

 and defensive power, an empirical formula might be framed 



— such as Mr. Barnaby attempted with insufficient data 

 in 1872 — which would fairly represent the gross fighting 

 efficiency of a ship. Till this is done, no rule can possibly 

 be devised which will indicate anything more than the 

 mere opinions of the person who frames it ; while often, 

 as in the case of Mr. Barnaby's present displacement 

 basis, the application of the rule may be misleading in a 

 degree which its framer could never have foreseen or 

 intended. 



Sir E. J. Reed's letter to the Times, and the whole force 

 of the charges contained in it, rests mainly upon the truth 

 of the two assumptions we have considered. The first is 

 that the unarmoured ends of our present ironclads have 

 practically no protective value. This is a point which, as 

 we have said, may be determined once and for all by 

 scientific experiments. The second assumption is that the 

 comparative efficiency of our own ships and those of foreign 

 powers may be approximately measured by merely com- 

 paring their displacements. This proposition is unsound, 

 and does not admit of any qualifying corrections short 

 of depriving it of all specific meaning. A scientific 

 standard or unit of comparison which may be fairly 

 applied to the approximate determination of the relative 

 fighting powers of war-ships and navies is greatly to be 

 desired ; but before such an one can be framed, the per- 

 sons who have to use our ships of war and to take them 

 into action, and those who are responsible for their 

 efficient construction, must come to some definite under- 

 standing as to what the various elements of fighting power 

 consist of, and what are their relative degrees of import- 

 ance ; and to do so they must call in the aid of Science. 



PROFESSOR WILLIAMSON'S DYNAMICS 

 An Elementary Treatise on Dynamics, containing Ap- 

 plications to Thermodynamics, &*c. By Benjamin 

 Williamson, F.R.S., and Francis A. Tarleton, LL.D.. 

 (London : Longmans, Green, and Co., 1885.) 



PROFESSOR WILLIAMSON is already so well 

 known to the student by his excellent text-books of 

 the Differential, and of the Integral, Calculus, that his 

 appearance in a new field of authorship is sure to excite 

 attention. We accordingly opened the present work with 

 expectations of a very high order. Not, of course, expect- 

 ations that much novelty of matter could be introduced 

 in an elementary work on a subject which has been 

 thoroughly threshed-out, but that possibly fresh interest 

 and easier assimilability might be given to long-known 

 facts and processes by some novel mode of presentation. 



In these expectations we have been disappointed. 

 Either the subject of Dynamics does not admit of treat- 

 ment superior to that which it has already received, or 

 our authors are not destined to be the pioneers to the 

 possible improvements. Our special reasons for this 

 statement we will give with some detail, but we may 

 begin with some general observations. 



From the time in which Jackson, Lloyd, Whewell, and 

 many others, introduced continental methods to the 

 average Honour-man; through the period of Earnshaw, 

 Pratt, Wilson, Tait and Steele, Griffin, Walton, &c, to 

 the Parkinson, Bezant, Routh, &c, of the present day, 

 there has been a plethora of treatises in English on the 

 various parts of elementary Dynamics. Some of these 



