TRANSACTIONS OF SECTION G.— PBESIDENTIAL ADDRESS. 809 



Section G.— ENGINEERING, 

 Presipicnt of tup (Section— Dvgald Clerk, F,E.8„ MJnst.C.E. 



THUESDA Y, SEPTEMBEIl 3. 



The Pretident deliveretl the following Address: — 



At the middle of the last century the steam engine had attained to a high degree 

 of perfection. Its development was, it is true, incomplete, but it had been suc- 

 cessfully applied to all the great duties of the mine, the waterworks, the factory, 

 the railway, and the steamship. The engines were mechanically excellent ; the 

 fuel economy was good, and they were built in units of thousands of horse-power. 

 Steam power, in fact, was revolutionising the whole of the social and industrial 

 conditions of the globe. Notwithstanding this great material and engineering 

 success, the world was in complete darkness as to the connection between steam 

 motive-power and heat. It was seen that motive power of almost any magnitude 

 could be obtained by the agency of heat ; but how it was obtained and how much 

 power was connected with a given quantity of heat was quite unknown. The 

 fuel consumptions of existing engines were known, and certain modes of improving 

 economy were evident, and engineers were busily engaged in testing these modes 

 by the slow but sure methods of invention, design, construction, and operation in 

 practical work : but in this they had but little aid from pure science. 



The science of thermodynamics did not yet exist. 



New light was dawning, however, which gradually illumined the whole world 

 of pure science and engineering practice. 



Men of the first rank in intellect — Newton, Cavendish, Eumford, Young and 

 Davy — had long before expressed the opinion that heat was not material in its 

 nature, but was a mode of motion ; but their opinions, although to some extent 

 supported by experiment, made little impression upon the scientific world, and in 

 1850 we still find the most distinguished physicists adhering to the ' caloric ' or 

 material theory of heat. 



The great change, from the errors of the old theories to the truth of the new, 

 was due to the work of Joule, Thomson, and Eankine in Great Britain, and of 

 Carnot, Meyer, Clausius, Helmholtz, and Hirn on the Continent. The story 

 begins with the work of Carnot in 1824-, who published in Paris in that year a 

 pamphlet entitled ' Reflections upon the Motive Power of Heat.' He was 

 attracted by the problem of the steam engine and the air engine. lie saw that 

 heat and motive power were connected in some manner, and he endeavoured to 

 settle in a quantitative way the limits of that connection by the invention of an 

 ideal series of operations by means of which the greatest conceivable amount of 

 mechanical power may be obtained from a given quantity of heat under given 

 circumstances. For the purpose of his demonstration he assumes only two 

 things : (1) That if heat be added to any body under standard conditions of 

 tejnperfiture, pressure, and voUnne, and the body be carried through any series of 



