12 THE PRESIDENTIAL ADDRESS 



It is clear that there was much need for the scientific leaven 

 which the new Association could, and did, provide. 



Another of the early concerns of the Association was with the 

 performance of steam engines. At the date of our foundation 

 more than fifty years had passed since the inventions of Watt 

 provided an engine fit to serve as a general means of producing 

 power. Its earliest application, and still at that date its most 

 common one, was in the pumping of mines. Engineers took a pro- 

 fessional and even sporting interest in what they called its ' duty,' 

 meaning the amount of water pumped through a given height for each 

 bushel of coal consumed. Nevertheless it is a remarkable fact that 

 neither they nor the physicists of that period had any notion that 

 the process involved a conversion of heat into mechanical work. 

 It is difficult for us now to imagine a world of physics and engineer- 

 ing where the idea had not yet dawned that there was such a thing 

 as energy, capable of Protean transformations, but in all of them 

 conserving its total amount. Enlightenment was soon to come, 

 and our meeting-rooms furnished the scene. In 1843 Joule brought 

 before one of the sections his first determination of the mechanical 

 equivalent of heat. He spoke with the modesty natural — in those 

 days — to a man of twenty-four. His paper was received in chilly 

 silence. Two years later, after further experiments, he reappeared ; 

 but again no notice was taken of the heresies of a youthful amateur. 

 Nothing daunted, he prepared a fuller case for the Oxford meeting 

 of 1847, perhaps remembering that Oxford is the home of lost 

 causes. In a narrative written many years later, Joule has told 

 how the Chairman suggested that as the business of the Section 

 pressed he should not read the paper, but merely give a brief account 

 of his experiments : 



' This [he says] I endeavoured to do, and discussion not being 

 invited, the communication would have passed without comment 

 if a young man had not risen in the Section and by his intelligent 

 observations created a lively interest in the new theory. The 

 young man was William Thomson.' 



But Thomson, though deeply interested, was not at first con- 

 vinced. Nearly four years more were to pass before he satisfied 

 himself that the doctrines of Joule did not clash with the teachings 

 of Carnot, of which he was then an enthusiastic proselyte. At 

 length he became a convert ; he saw, as we should now say, that 

 the First Law of Thermodynamics was in fact consistent with the 

 Second. Then indeed he accepted the principles of Joule in their 

 entirety and was eager in their support. Quickly he proceeded 

 to apply them to every part of the physical domain. Along with 

 Clausius and Rankine he formulated the principles which govern 



