September ii, 1919] 



NATURE 



=9 



money to small committees or individuals, to enable 

 them to carry on new researches ; and thirdly, by 

 recommending the Government to undertake expedi- 

 tions of discovery, or to make grants of money for 

 certain and national purposes, which were bevond the 

 means of the association." As a matter of fact it 

 has, since its commencement, paid out of its own 

 funds upwards of 80,000/. in grants of this kind. 



Developments Prior to the War. 



It is twenty-nine years since an engineer. Sir 

 l->ederick Bramwell, occupied this chair and dis- 

 coursed so charmingly on the great importance of the 

 next-to-nothing, the importance of looking after little 

 things which, in engineering, as in other walks of 

 life, are often too lightly considered. 



The advances in engineering during the last twenty 

 \ears are too many and complex to allow of their 

 description, however short, being included in one 

 address, and, following the example of some of my 

 I>redecessors in this chair, I shall refer only to some 

 of the most important features of this wide subject. 

 I feel that I cannot do better than begin bv quoting 

 from a speech made recently by Lord Inchcajx', when 

 speaking on the question of the nationalisation of 

 co.il : — " It is no exaggeration to say that coal has 

 been the maker of modern Britain, and that those 

 who discovered and developed the methods of working 

 it have done more to determine the bent of British 

 activities and the form of British society than all the 

 Parliaments of the past hundred and twenty vears." 



James Watt. — No excuse is necessary for entering 

 upon this theme, because this year marks the 

 Iiundredth anniversary of the death of James Watt, 

 .ind in reviewing the past it appears that England 

 has gained her present proud position bv her early 

 enterprise and by the success of the Watt steam- 

 engine, which enabled her to become the first countrv 

 to develop her resources in coal, and led to the estab- 

 lishment of her great manufactures and her immense 

 mercantile marine. 



The laws of steam which James Watt discovered 

 are simply these : — That the latent heat is nearly con- 

 stant for different pressures within the ranges used 

 in steam-engines, and that, consequentlv, the greater 

 the steam pressure and the greater the range of 

 expansion, the greater will be the work obtained from 

 a given amount of steam. Secondly, as may now 

 seem to us obvious, that steam from its expansive 

 force will rush into a vacuum. Having regard to the 

 state of knowledge at the time,- his conclusions appear 

 to have been the result of close and patient reasoning 

 by a mind endowed with extraordinary powers of 

 insight into physical questions, and with the faculty 

 of drawing sound practical conclusions from numerous 

 experiments devised to throw light on the subject 

 under investigation. His resource, courage, and 

 devotion w-ere extraordinary. 



In commencing his investigations on the steam- 

 engine he soon discovered that there was a tremendous 

 loss in the Newcomen engine, which he thought might 

 he remedied. This was the loss caused bv condensa- 

 tion of the steam on the cold metal walls of the 

 i\linder. He first commenced by lining the walls 

 with wood, a material of low thermal conductivity. 

 Though this improved matters, he was not satisfied ; 

 liis intuition probably told him that there should be 

 some better solution of the problem, and doubtless 

 he made many experiments before he realised that 

 the true solution lay in a condenser separate from the 

 cylinder of the engine. It is easy after discovery to 

 say, "How obvious and how simple," but many of 

 us here know how difficult is any step of advance 

 when shrouded by unknown surroundings, and we can 



NO. 2602, VOL. 104] 



well appj-eciatc the courage and the amount of inves- 

 tigation necessary before James Watt thought himself 

 'justified in trying the separate condenser. But to us 

 now, and to the youngest student who knows the laws 

 of steam as formulated by Carnot, Joule, and Kelvin, 

 the separate condenser is the obvious means of con- 

 structing an economical condensing engine. 



Watt's experiments led him to a clear view of the 

 great importance of securing as much expansion as 

 possible in his engines. The materials and appliances 

 for boiler and machine construction were at that time 

 so undeveloped that steam pressures were practically 

 limited to a few pounds above atmospheric pressure. 

 The cylinders and pistons of his engines were not con- 

 structed with the facility and accuracy to which we 

 are now accustomed, and chiefly for these reasons 

 expansion ratios of from twofold to threefold were the 

 usual i)ractice. Watt had given to the world an 

 engine which consumed from five to seven pounds of 

 coal per horse-power hour, or one-quarter of the fuel 

 previously used bv any engine. With this consump- 

 tion of fuel its field under the conditions prevailing at 

 the time was practically unlimited. What need was 

 there, therefore, for commercial reasons, to endeavour 

 still further to improve the engine at the risk of 

 encountering fresh difficulties and greater commercial 

 embarrassments? The cour.se was rather for him and 

 his partners to devote all their energy to extend the 

 adoption of the engine as it stood, and this they did, 

 and to the Watt engine, consuming from five to 

 seven pounds of coal per horse-power, mankind owes 

 the greatest permanent advances in material welfare 

 recorded in history. 



With secondary modifications, it was the prime 

 mover in most general use for eighty years, i.e. until 

 the middle of last century. It remained for others to 

 carry the expansion of steam still further in the com- 

 pound, triple, and, lastly, in the quadruple expansion 

 engine, which is the most economical reciprocating 

 engine of to-day. 



Watt had considered the practicability of the tur- 

 bine. He writes to his partner, Boulton, in 1784 : — 

 "The whole success of the machine depends on the 

 possibility of prodigious velocities. In short, without 

 God makes it possible for things to move them one 

 thousand feet per second, it cannot do us much 

 harm." The advance in tools of precision, and a 

 clearer knowledge of the dynamics of rotating bodies, 

 have now made the speeds mentioned by Watt feasible, 

 and, indeed, common, everyday practice. 



Turbines. — The turbine of to-day carries the expan- 

 sion of steam much further than has been found 

 possible in any reciprocating engine, and owing to 

 this property it has surpassed it in the economy of 

 coal, and it realises to the fullest extent Watt's ideal 

 of the expansion of steam from the boiler to the 

 lowest vapour pressure obtainable in the conden.ser. 



.Among the minor improvements which in recent 

 years have conduced to a higher efficiency in turbines 

 are the more accurate cur\-ature of the blades to avoid 

 eddy losses in the steam, the raising of the peri- 

 pheral velocities of the blades to nearly the velocity 

 of the steam impinging upon them, and details of 

 construction to reduce leakages to a minimum. In 

 turbines of 20,000-30,000 h. p., 82 per cent, of the avail- 

 able energy in the steam is now obtainable as brake- 

 horse-power; and with a boiler efficiency of 8^ per 

 cent, the thermodynamic efficiency from the fuel to 

 the electrical output of the alternator has reached 

 23 per cent., and shortly mav reach 28 per cent., a 

 result rivalling the eiTiciencv of internal-combustion 

 engines worked bv producer-gas. 



During the twenty years immediately preceding the 

 war turbo-generators had increased in size from 



