G.— ENGINEERING. 131 



unit. These two discoveries of Rontgen and Planck form the starting- 

 point of that most important branch of modern Physics which has increased 

 our knowledge of the constitution of matter, a science which is just 

 beginning to find its field of application in engineering practice, as in the 

 thermionic valve and the modern power transformers on the same lines. 

 From these and other applications great advances are still to be expected. 

 In reviewing the discoveries in Physics which have had most effect in 

 developing new industries and thus calling forth new inventions, one is 

 struck by the great results in this respect which have arisen from applica- 

 tion of the Second Law of Thermodynamics, first stated by Carnot in 1824. 

 Carnot described his ideal heat engine and showed that the efficiency of 

 this engine is independent of the working substance used. Looking back 

 upon the history of the science of thermodynamics of the last century it is 

 unfortunate that no one seems to have employed this statement of Carnot's 

 as a general text, and developed it to find what information could be derived 

 from it by using different working substances and mixtures in order to 

 discover something about all the substances used. Had anyone done so, 

 progress might have been greatly accelerated. James Thomson was the 

 first to use this Second Law to determine the lowering of the freezing-point 

 of water due to pressure. His brother, Lord Kelvin, followed with the 

 application to the change from liquid to vapour. Helmholtz used the 

 voltaic cell as the working substance and determined the temperature 

 co-efficient of its electro-motive force. Then followed at long intervals the 

 application to chemical changes which have resulted in the modern science 

 of thermodynamic chemistry with which the names of Helmholtz, 

 Ostwald, Nernst, Van 't Hoff and Gibbs are so closely associated, and 

 upon which the modern industry of chemical engineering is based. It is 

 a wonderful development to be able to prophesy that under certain condi- 

 tions a certain chemical reaction will take place, say, that the nitrogen and 

 oxygen of the air will combine at certain temperatures and pressures in 

 a definite proportion, and that the resultant oxide can be recovered and 

 converted to nitrate and used as fertiliser to replace the imported article 

 at an economic price. 



The applications of thermodynamic chemistry to explosives enable us 

 to calculate the maximum pressure to be obtained by detonating an ex- 

 plosive, or to calculate the temperatures and pressures throughout the 

 explosion of cordite in a gun from the chemical constituents of the cordite. 

 This possibility has gone far to raise internal ballistics from an empirical 

 science to a branch of Natural Philosophy. 



The advances which have taken place in the commercial development 

 of chemical processes based upon this important new science of thermo- 

 chemistry, although already considerable, are only in their infancy, but 

 the men with the experience gained in practical development are very few ; 

 and as the experiments are generally very lengthy and expensive, the 

 development of the industry is necessarily slow. The resultant saving to 

 the country, however, will far outweigh the cost. 



Invention forms the natural link between Physics, Chemistry and 

 Engineering, and every advance in one or other of these produces a reflex 

 action on the other. For instance, a discovery in physics which increases 

 accuracy of measurement by providing an indicator more sensitive than 



k2 



