CLAIMS OF JOULE, GKOVE, AND MAYER. XXIX 



According to the strict rule of science, that in all those cases 

 where experimental proof is possible, he who first supplies it is the 

 true discoverer, Dr. Joule must he assigned the foremost place 

 among the modern investigators of the subject. He dealt with the 

 whole question upon the basis of experiment. He labored with 

 great perseverance and skill to determine the mechanical equivalent 

 of heat the corner-stone of the edifice ; and in accomplishing this 

 result in 1850, he may be said to have matured the work of Kumford, 

 and finally established upon an experimental basis the great law of 

 thermo-dynamics, to remain a demonstration of science forever. 



Professor Grove has also worked out the subject in his own in- 

 dependent way. Combining original experimental investigations 

 of great acuteness, with the philosophic employment of the gen- 

 eral results of science, he was the first to give complete and system- 

 atic expression to the new views. His able work, which opens 

 the present series, is an authoritative exposition, and an acknowl- 

 edged classic upon the subject. 



Again, the claims of Dr. Mayer to an eminent and enviable 

 place among the pioneers of this great scientific movement, are un- 

 questionable. There has evidently been, on the part of some Eng- 

 glish writers, an unworthy inclination to depreciate his merits, 

 which has given rise to a sharp and searching controversy. The 

 intellectual rights of the German philosopher have, however, been 

 decisively vindicated by the chivalric pen of Prof. Tyndall ; and it 

 is to the public interest thus excited, that we are indebted for the 

 translation of Mayer's papers, which appear in this volume. Mayer 

 did not experiment to the extent of Joule and Grove, yet he well 

 knew its importance, and made such investigations as his apparatus 

 and the duties of a laborious profession would allow. Yet his 

 views were not therefore mere ingenious and probable conjectures. 

 Master of the results of modern science, and of the mathematical 

 methods of dealing with them, possessing a broad philosophic 

 grasp, and an extraordinary mental pertinacity, Dr. Mayer entered 

 early upon the inquiry, and not only has he developed many of its 



