j84 



NATURE 



[August i6, 1894 



of teaching sii'ijecls is sometimes too prominent, to the neglect 

 of matters less obviously useful. It is, of course, one thing to 

 know a subject from the examination point of view, and quite 

 another to be able to think about it, and still another to be able 

 to write about it. In particular, I have often regretted to find 

 how little attention has been given lo a matter which perhaps 

 may be called literary rather than scientific, but which is all-im- 

 poriant in criticism, I mean to the power of expression. It is not 

 easy to overrate the importance to the engineer, as to other folk, 

 of the power of saying clearly what hemeans, and of saying just 

 what he means. I do not mean only of doing this for its own 

 sake, but because if a man cannot say or write clearly what he 

 means it is improbable that he can think clearly By the power 

 of expression I do not mean, of course, the mere power of 

 speaking fluently in public, a thing which appears physically 

 impossiule to some people ; I mean rather the power of ex- 

 pression in writing, which carries with it clearness and con- 

 secutiveness of thought. It is difficult to know how this matter 

 can be taught, but at least it can be insisted upon probably 

 to a much greater extent than is commonly the case. A 

 man requires to see clearly not only the exact thing which he 

 wants to say, but the whole environment of that thing as it 

 appears to him. Not only this hut he must see the whole en- 

 vironment of the same thing as it app.'ars to the persons for 

 whom he is writing, or to whom he is speaking. He has to see 

 what they know about the matter, what they think, and what 

 they think they know, and if he wishes to be really understood 

 has got to do much more than merely write the thing he means. 

 He has carefully to unwrite, if I may use the expression, the 

 various things that other people will be certain to think that he 

 means. For after all the great majority of people are very care- 

 less listeners and readers, and it is not for the small minority 

 who are really exact in these m.itters that one has to write. 

 Moreover, it is a great help to clearness of thought and expres- 

 sion to keep before one always an ideal audience of people who 

 will certainly misunderstand every single sentence about which 

 any misunderstanding is in any way possible, and some others 

 as well. 



In attempting to think out or to discuss any question, whether 

 it be technical or non-technical — in fact as long only as it is non- 

 political — the first necessity is probably a knowledge of the 

 question itself ; and not only this, but also a proper under- 

 standing of its whole environment. This knowledge must be 

 of such a kind as to distinguish what parts of it are important, 

 what parts of it are unimportant, what parts can be described 

 in two sentences, and what others may require as many para- 

 graphs ; what parts affect the result but little, however large 

 they seem ; and which ones must be considered vital, although 

 their very existence is difficult to discover. The faculty which 

 enables a man to handle his knowledge in this fashion may be 

 summed up in the single expression, "sense of proportion." 

 Moreover, the knowledge, to be of real value, must be as totally 

 free from prejudices and prepossessions as in the most rigorous 

 branch of pure science, and as thoroughly imbued with a healthy 

 spirit of scepticism. 



One is accustomed to think of engineering work as mainly 

 constructive. Uut after all it is quite as much critical. In 

 almo-it every department of mechanical work there are half a 

 dozen ways of solving any particular problem. In some fashion 

 or other the engineer must be able to judge between these 

 various methods, methods which arc often very much alike, but 

 each of which may possess certain particular advantages and 

 certain particular drawbacks. The arithmetical criticism which 

 merely counts the advantages and the drawbacks, and puts an 

 equal number of the one against an equ.il number uf the other, 

 i» common enough, but obviously useless. The very first 

 necessiiy to the critic is that he should have what I have just 

 called the sense of proportion, a sense which will enable him to 

 distinguish mere acailcmical objections from serious practical 

 dilficultics, which shall enable him to balance twenty advantages 

 which can be enumerated on paper by one serious draw- 

 back which will exist in fact, which will enable him in 

 (act to place molehills of experience against mountains of 

 talk. It is perhaps a doubtful point how lar this sense of pro- 

 portion can t)e taught at all. No doubt it can only be built up 

 upon »ome natural tiasis. I am sure that in engineering we all 

 know men whoac judgment as to whether it was advisable to take 

 B particular course we would accept implicitly, because wc know 

 that it i> ba.ied on large general criticism, in spite of the most 

 elaborate and specioui arguments against it set down o.i paper. 



NO. 1294, VOL. 50] 



Any third-year student— not to go still further back — can 

 criticise perfectly along certain very narrow lines, just as anyone 

 can learn the rules of harmony and can write something in ac- 

 cordance with them which purports to be music. Hut after all 

 the music may be music only in name, and the criticism may 

 not be worth the paper it is written upon, however formal it 

 may appear to be, unless the writer is thoroughly imbued with a 

 sense of the proportionate value of the different points which he 

 makes. To take the commonest possible case, I d.are say we 

 have all of us heard certain methods, mech.inical, chemical, or 

 other, stigmatised as totally wrong and absolutely useless 

 because they contain certain easily provable errors I am sure, 

 too, that most of us could give illustrations of cases in which 

 this has has been said with the very greatest dogmatism when 

 the errors of the impugned method are not one-tenth p.art as 

 great as the equally unavoidable errors of observation in the 

 most perfect method. 



Probably the best special education in proportion which a man 

 can have is a course of quantitative experimental work. I say 

 quanlilative with emphasis, as meaning something much more 

 than mere qualitative work. Here, I think, comes in the use- 

 fulness of the engineering laboratory. We require that the 

 training should be not only in absolute measurement, but in 

 relative measurement, the latter being quite as important as the 

 former. Many kinds of measurements stand more or less upon 

 a level as a training of the faculties of observation in themselves, 

 but no single kind of me.tsurement is sufticient as a training in 

 proportion. A year spent in calibrating thermometers or gal- 

 vanometers might make an exceedingly accurate observer in a 

 perticular line, but it would not give the observer a knowledge 

 of what even constituted accuracy in other directions ; for 

 accuracy is a relative and not an absolute term. In most 

 engineering matters the conditions are, unfortunately, of a 

 most complex kind ; so complex that our problems are in- 

 capable of any solution sufficiently exact to satisfy the mathe- 

 matician or physicist. The temptation to treat these problems 

 as the mathematician treats those with which he deals — namely, 

 to alter the .-issumed conditions in order to get an exact solution 

 — is a very strong one. I am afraid it is most strong often in 

 I those engineers who are the best mathematicians. It is a 

 temptation, however, steadily to be resisted. We must assume 

 our conditions to be what they actually are, and not what we 

 should like them to be ; and il we cannot obtain an exact solu- 

 tion of our problem with its actual conditions, so much the worse 

 for us, not so much the worse for the conditions. Our first duty 

 is generally to find out the conditions ; if they are disadvan- 

 tageous (in fact I mean, and not merely in the problem) to alter 

 them if they can be altered, but not to ignore them because they 

 are inconvenient. We have then to find out the extent 10 

 which the known conditions permit any exactness of solution at 

 all, and, finally, we have to keep this in view as a measurement 

 of the highest accuracy which is attainable. To work out ceitain 

 branches of the problem with such minuteness as to give 

 us apparently very much greater accuracy than this is not 

 only useless, but is apt to be positively misleading, as giving an 

 impression of an accuracy which has no real existence. 



The relative value of accuracy in dilferent sets of observations 

 is in itself a matter in which a sense of proportion is wanted, 

 and often very badly wanted. Where one has to measure half 

 a dozen things of which two are very easily measured and the 

 remaining four are only measurable with great dilliculty, it is 

 only human nature that we should spend our energies on getting 

 extremely accurate results with the first two and roughly do our 

 best with the others. It is very dillicult under such circum- 

 stances to remember that the accuracy of the whole is not the 

 .accuracy of the best part of our work, but of the worst. 



The extraordin.iry eU'ect of a want of sense of pro))orlion IS 

 nowhere butter shown than in the absurd statements which are 

 constantly made as lo technical matters in public prospectuses, 

 and the still more absurd statements made in those very nume- 

 reus documents of a similar kind of which some o( us see a great 

 many, but which do not finally emerge into public view, lor- 

 luncsarc apparently to be made by inventions which, although 

 doubtless ingenious, yet only concern one way of doing a thing 

 which coulil be done equally well in half a ilozen other w.iys. 

 Every one is expected to run alter a piece of apparatus which is 

 to save 50 per cent, of something, the total cost of that some- 

 thing, however, being so very small that nobody cares to save in 

 it at all. I need hardly mention the all too common case where 

 a contemplated saving of 10 per cent in the cost of a material 



