Joule, • 339 



heat. We have the pleasure of knowing that he went still 

 further, and showed that whilst the heat itself resulted in 

 force, that force had a definite limit, and could be estimated 

 by the amount of chemical action or by the combinations 

 taking place between the elements. In other words, he 

 showed the connection between chemical action, electricity, 

 heat, and mechanical force. The long train of papers on 

 this subject written by Dr. Joule would astonish many who 

 receive his results in a few lines and are satisfied with 

 their simplicity ; but it would also be a very simple thing 

 if after living to maturity in a pit, with artificial light only, 

 we were to come up and see the sun. How simply we 

 should then get light — no candle used, no wax, no oil, no 

 paraffin ; the sun laughs at all our methods of illumination, 

 and we, too, may laugh at ourselves when we think how 

 short was our view in the direction indicated before Dr. 

 Joule discovered the mechanical equivalent of heat. To 

 show the fullest early form in which the author approached 

 the subject we quote farther on. (See Mem. of the Lit. and 

 Phil. Soc. of Manchester, Vol. VII., Second Series, pp. 

 103, 104, and no.) We shall further quote a paper read 

 January 24, 1843, his 20th paper on heat, electricity, and 

 magnetism, though still a youth. 



When speaking of Dr. Joule we must not forget to 

 put before ourselves clearly the position taken up by 

 Faraday in the development of measurable quantity, a 

 position which is gained by the vantage ground of the 

 atomic theory, and stands between that of Dalton's and 

 Joule's, to whose wider generalisations it tended. In his 

 ' Experimental Researches in Electricity,' § 704 (ed. 

 1839), we find one of his papers read in January 1834: 

 ' I have already said, when engaged in reducing common 



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