372 M. J. R. Mayer on the Forces of Inorganic Nature. 



and how arc different forces related to each other ? Whereas 

 the term matter implies the possession, by the object to which it 

 is applied, of very definite properties, such as weight and exten- 

 sion ; the term force conveys for the most part the idea of some- 

 thing unknown, unsearchable, and hypothetical. An attempt to 

 render the notion of force equally exact with that of matter, and 

 so to denote by it only objects of actual investigation, is one 

 which, with the consequences that flow from it, ought not to be 

 unwelcome to those who desire that their views of nature may be 

 clear and unencumbered by hypotheses. 



Forces are causes : accordingly, we may in relation to them 

 make full application of the principle — causa cequat effectum. If 

 the cause c has the effect e, then c = e; if, in its turn, e is the 

 cause of a second effect/, we have e =f } and so on : c = e =/. . . = c. 

 In a cjiain of causes and effects, a term or a part of a term can 

 never, as plainly appears from the nature of an equation, become 

 equal to nothing. This first property of all causes we call their 

 indestructibility. 



If the given cause c has produced an effect e equal to itself, it 

 has in that very act ceased to be : c has become e ; if, after the 

 production of e, c still remained in whole or in part, there must 

 be still further effects corresponding to this remaining cause : 

 the total effect of c would thus be :> e, which would be contrary 

 to the supposition c=e. Accordingly, since c becomes e } and e 

 becomes /, &c, we must regard these various magnitudes as dif- 

 ferent forms under which one and the same object makes its 

 appearance. This capability of assuming various forms is the 

 second essential property of all causes. Taking both properties 

 together, we may say, causes are (quantitatively) indestructible 

 and (qualitatively) convertible objects. 



Two classes of causes occur in nature, which, so far as expe- 

 rience goes, never pass one into another. The first class consists 

 of such causes as possess the properties of weight and impene- 

 trability ; these are kinds of Matter : the other class is made up 

 of causes which are wanting in the properties just mentioned, 

 namely Forces, called also Imponderables, from the negative 

 property that has been indicated. Forces are therefore inde- 

 structible, convertible, imponderable objects. 



in Anderson's University, Glasgow. — Considerable attention having of late 

 been called to the author of this paper, as one of the earliest propounders 

 of the doctrine of the Indestructibility of Force, and especially of the idea 

 of the equivalence of Heat and Work, it will probably interest many readers 

 of the Philosophical Magazine to have placed in their hands his earliest 

 publication on the subject. For some account of Mayer and of his further 

 labours, see Prof. TyndalPs lecture " On Force,'' Phil. Mag. S. 4. vol. xxiv. 

 pp. C4-66. 



