66 



NATURE 



[May i8, 1893 



faom the endless variations in the physical, moral, and mental 

 powers of human beings, and therefore to be as unalterable at 

 the bidding of man as these attributes are. It only remains for 

 us to recognise the fact, to make the best of it, and to avoid the 

 gross wickedness of attempting to delude the poorer and more 

 ignorant members of the community by incessant representations 

 that it is the greed and selfishness of the wealthy which keep 

 them low. 



If the so-called "working man" be the embodiment of all 

 that is needed for the industrial prosperity of a country, and if 

 the possession of capital and the far wider consequence, the 

 existence of credit, be a crime, why does he not arise in his 

 strength and exhibit the faculties of combination which are so 

 well illustrated in the trades unions, and establish engineering 

 works and manufactories, or undertake engineering enterprises 

 from which he will be able himself to reap the golden harvest 

 which the capitalist and the shareholder are supposed to gather, 

 and who thereby excite his envy and arouse his hatred. 



In deference, I presume, to the immense numerical import- 

 ance of the operative classes, politicians are vieing with each 

 other in supporting the impossible claims put forth — claims 

 which, if conceded, will only precipitate the ruin of the class 

 they profess to benefit, and which already is the form of what 

 may be termed benevolent legislation in favour of the operative, 

 is heaping up elements of cost which our productive energy is 

 unable to bear. The absurd cry that manual labour is the sole 

 source of wealth has been well combated by that acute reasoner, 

 Mr. Macfarlane Gray, who, in a recent discussion on the labour 

 question, happily compared the body politic to a tree. The 

 popular belief is that plants are nourished through their roots, 

 which for that reason are believed to be the all-important parts, 

 while the leaves are mere ornaments, enjoying the upper air and 

 sunshine and profiting by the work done underground. But a 

 juster knowledge, one of the fruitsof abstract investigation, tells 

 us that the roots are mainly useful in holding the tree erect, and 

 have comparatively little to do with providing the materials for 

 building up its structure. It is the leaves which form the great 

 laboratory in which the main components of the plant are ex- 

 tracted from the region where superficial observers would least 

 expect to find them — namely, from the atmosphere. He com- 

 pares the roots to the operatives' part of the community ; the 

 trunk and leaves to the monetary, the scientific and the com- 

 mercial part which drew from far and wide that which i.s neces- 

 sary to keep the growth advancing and maintain it in health. 

 The roots may just as well claim to be the sole sources of life in 

 the tree as the operatives may claim to be the only producers of 

 wealth, and conversely the leaves could, with as much reason, 

 consider themselves as the only essential portion of the plant as 

 the merchant or the capitalist claim to be independent of the 

 operatives. Each grade in the body politic is essential to the 

 other ; it is an axiom that there can be no degrees of comparison 

 between essential parts; and those who, fiom ignorance or from 

 interested motives, persistently preach the doctrine of the iuperior 

 importance of the "masses" over the "classes" are inflicting a 

 deep injury on the prosperity of the country, and especially on 

 those whom th^y so grossly flatter. 



Nothing, save bitter experience, will alter the course of events. 

 It seems to be the fate of peoples to attack social problems from 

 the wrong end, to solve them by the painful and dilatory pro- 

 cess of trial and error, rather than by means of investigation 

 based on first principles. And this method is commonly ap- 

 plied to engineering problems also. Random trials, as a rule, 

 are the methods by which great results have been achieved, while 

 the application of the scientific principles involved have been 

 left to other heads long after the results sought have been at- 

 tained at much needless cost, and by much unnecessary expen- 

 diture of labour and of time. 



It is not often that a genius of the order of James Walt rises in 

 the mechanical world. Up to his time the " fire-engine," as it 

 was most properly called, was being slowly developed without 

 any exact knowledge of the properties of the agent by means of 

 which the heat generated by the combustion of fuel was con- 

 verted into work, and this in spite of the circumstance that such 

 a master mind as that of Smeaton had been directed to per- 

 fecting the new method of utilising the potential energy of fuel, 

 and of applying it to engines of large power, and on an extensive 

 industrial scale. 



The lucky chance which presented itself of having to put in 

 order a working model ofaNewcomen engine illustrates in an 

 interesting manner how, in pursuance of his business, he quickly 



NO. 1229, VOL. 48J 



executed the necessary repairs and alterations, andaflerwards, at 

 greater leisure, attacked the problem which the failure of the 

 model presented, from the theoretical side, but soon found that 

 the then state of knowledge did not afford the means of explain- 

 ing the failure, and compelled him to set about the determination 

 of such elementary data as the specific volume of steam, the 

 latent heat of evaporation, and the law of tension of steam under 

 varying temperatures. In the astonishingly short period of two 

 years, and with the rudest and cheapest apparatus, he had fur- 

 nished himself with the abstract knowledge required for explain- 

 ing in a definite manner the action of ihe steam engine, and he 

 bad no difficulty, as soon as his theoretical ground was sure, in 

 determining what mechanical arrangements were necessary to 

 realise the conditions imposed by .<-cience. From investigations 

 apparently of an abstract or non-practical character, sprung at 

 once the separate condenser, the closed cylinder and the equi- 

 librium working of a single-acting engine, the steam jacket, the 

 air-pump, the theory of expansive working, the function of the 

 momentum of the moving parts, and the exact calculations based 

 on first principles by means of which the proportions of engines 

 could be fixed, and the quantities of steam, water, and of fuel 

 calculated. Watt, of course, was a born mechanic, as well as a 

 seeker after physical knowledge. The workshop in his house 

 near Birmingham, happily preserved to this day as he left it, 

 shows that his mind was ever bent on mechanical contrivances 

 which his own hands were skilful enough to carry out ; his valve- 

 gear, the stuffing box, the parallel motion, the governor, are all 

 instances of that happy blending of mechanical skill and of 

 scientific research which must ever mark the qualifications of a 

 great mechanical engineer. 



A contrast to Watt's achievements is the singular history of th& 

 development of iron and steel bridge building, which necessarily 

 followed the introduction of railways. Watt lelt the want of first 

 principles by which to shape his actions, and set about discover- 

 ing them ; but the principles which underlie the determination of 

 stresses in braced structures, such as roofs and frameworks of 

 various kinds, as well as those in solid bars subjected to the action 

 of transverse forces, have long been known ; and early iii this cen- 

 tury Navier made them the subjects of lectures at the Ecole des 

 Fonts et Chaussees, yet engineers in this country seem to have 

 been but dimly aware of them, or, at any rate, to have made little 

 use of the knowledge which was at their disposal. It is difficult, 

 from the published histories of such enterprises as the Conway 

 and Britannia bridges, to arrive at any conclusion as to the ex- 

 tent of knowledge, or rather ignorance, which existed among 

 engineers before these works were commenced. It is suffi- 

 ciently evident, however, from the long series of purely tenta- 

 tive experiments by which the proportions of the Conway and 

 Britannia bridges were determined, as well as from the singular 

 vagaries to be noticed in the smaller bridges of that day, that 

 only the haziest ideas of the disposition of stresses, and of the 

 functions of the component members of girders existed. 



In the experimental investigations of the time, the function of 

 the web or vertical member of a girder was completely ignored, 

 for it was looked upon merely as the means of keeping the top 

 and bottom flanges in their relative positions, while the essential 

 difference in effect of a uniformly distributed load, or of a 

 rolling load, as compared with a load concentrated at the centre, 

 on the vertical member of a girder, and even on the flanges, 

 appears to have been overlooked till made evident by the results 

 of experiment. Yet the principle that a force cannot change its 

 direction unless combined with another force acting in a direc- 

 tion inclined to it, was perfectly well known, and should have 

 led to the discovery that it is only by diagonal stresses in the 

 vertical members that the load resting on a beam can be trans- 

 mitted to the abutments ; that the stresses due to loads concen- 

 trated at the centre were very different to those arising, both ia 

 the vertical web and in the flanges, from the action due to a 

 load distributed in a given manner along the top or the bottom 

 flanges, and that a rolling load would produce effects peculiar 

 to itself. 



The girder with diagonally braced webs, or the lattice girder, 

 as it is commonly called, appears to have had its origin ia 

 Ireland ; at any rate it was in that country that it received its 

 earliest and chief development ; and in the hands of Wild, 

 Barton, Bow, and Stoney, the true principles began to assert 

 themselves, and Mr. Barton's Cusher River bridge, of 70 feet 

 span, on the Great Northern of Ireland Railway, was probably 

 the first example of a lattice girder in which the cross-sections 

 of the members of the webs as well as those of the flanges were 



I 



