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XXXI. Remarks on an Article entitled "Energy " in ' Good 

 Words. 9 By John Tyndall, F.R.S* 



THE time which I am able to devote to unscientific reading 

 is so stinted as to leave me in almost utter ignorance of 

 the general periodical literature of this country. Hence it is that 

 until the 20th of February I was not aware of the existence of an 

 article in the October Number of a journal called ' Good Words/ 

 from the combined pens of the Professors of Natural Philosophy in 

 Glasgow and in Edinburgh — Professor William Thomson and 

 Professor Tait — in which, though not mentioned by name, I am 

 referred to in a manner which it might be expected would have 

 come to my knowledge long ago. When, however, it is known 

 that the other articles in the number to which I refer, bear such 

 titles as "The Childhood of Jesus," "The Trial Sermon," 

 "The Bands of Love," "At Home in the Scriptures," &c, I 

 think I may be excused if an article on Energy, in the scientific 

 sense of the term, imbedded in such matter as those titles indi- 

 cate, escaped my attention. 



The article referred to contains the following paragraph : — 

 " Curiously enough, although similar coincidences are com- 

 mon, while Joule was pursuing and publishing his investigations, 

 there appeared in Germany a paper by Mayer, of Heilbronn. 

 Its title is 'Bemerkungen liber die Krafte der unbelebten Natur/ 

 and its date 1842. In this paper the results obtained by pre- 

 vious naturalists are stated with precision (among them the 

 fundamental one of Davy), new experiments are suggested, and 

 a method for finding the mechanical equivalent of heat is pro- 

 poundedf. On the strength of this publication an attempt has 



* Communicated by the Author. 



f To this portion of t their paragraph Messrs. Thomson and Tait have 

 appended the following note, which I leave to the consideration of those 

 who are acquainted with Mayer's publications. I purposely abstain from 

 making any scientific comment on either the article or the note; moral 

 considerations alone now interest me. " Mayer's method," writes the 

 northern philosophers, "is founded on the supposition that diminution of 

 the volume of a body implies an evolution or generation of heat ; and it 

 involves essentially a false analogy between the natural fall of a body to the 

 earth, and the condensation produced in an elastic fluid by the application 

 of external force. The hypothesis on which he thus grounds a definite 

 numerical estimate of the relation between the agencies here involved, is 

 that the heat evolved when an elastic fluid is compressed and kept cool, is 

 simply the dynamical equivalent of the work employed in compressing it. 

 The experimental investigations of subsequent naturalists have shown that 

 this hypothesis is altogether false for tbe generality of fluids, especially 

 liquids, and is at best only approximately true for air ; whereas Mayer's 

 statements imply its indiscriminate application to all bodies in nature, 

 whether gaseous, liquid, or solid, and show no reason for choosing air for 

 the application of the supposed principle to calculation, but that at the 

 time he wrote air was the only body for which the requisite numerical data 

 were known with any approximation to accuracy." 



