ACCEPTANCE OE ALL JOULE r S VIEWS. 131 



acumen of his deductions, no less than for the beauty of 

 his methods and the unequalled accuracy of his experiments. 



Such a recognition, coming after a careful and critical 

 consideration over a period of four years from such a 

 source, was well worth Joule's patience in waiting for it. 

 It not only assured him the full apprehension and appre- 

 ciation of his work, and what was yet more dear to him, 

 the truth of his philosophical deductions, but sounded his 

 trumpet with a blast which, while delightfully pleasant at 

 the time, was yet strong enough to awaken the scientific 

 sleepers all over the world, and go on echoing into succeed- 

 ing generations. 



In the meantime, Joule had been showing the importance 

 which he attached to the mechanical equivalent of heat by 

 a further investigation, into which he had thrown his whole 

 power ; and, aided by his experience and the perfection 

 of his appliances, had made the final determination. 



The paper containing this was communicated to the 

 Royal Society by Faraday, in June, 1849, before the publi- 

 cation of Rankine's paper. It was accepted and published 

 in the Philosophical Transactions \ 1850. The research con- 

 tains only one new departure from those previously published, 

 which was the determination of the equivalent from experi- 

 ments on the friction of cast-iron. But, in that the 

 experiments on fluid friction with water and with mercury 

 recounted in this paper, greatly exceeded in number those 

 previously given, being 41 with water, 52 with mercury, and 

 that they were made with more perfect apparatus, the 

 agreement between the results so obtained was closer; 

 besides being confirmed by the experiments with cast-iron. 

 These led Joule to the final conclusions ; — He says : " I 

 consider that 772^692, the equivalent derived from the 



