2 M. L. A. Colding on the Universal Powers of 



various energies must evidently call forth the idea that they also 

 are produced and developed for the purpose of disappearing after 

 having performed one or another effect on the particles of mat- 

 ter ; for, in the first place, it is well known that every kind of 

 energy (as, for example, energy of heat, mechanical energy, 

 electric energy, &c.) is able to produce all these energies ; and, 

 secondly, we know that when quantities of mechanical work, 

 quantities of heat, &c. are produced through certain quantities 

 of work, quantities of heat, &c, then these energies disappear 

 by degrees as new ones are produced. It is a well-known fact, 

 too, that the production of heat through heat, or of quantities 

 of mechanical work through quantities of mechanical work, &c, 

 is in reality nothing but the energy imparted from one system of 

 material particles to another, and no new production, and also 

 that the receiving body can at most merely receive an increment 

 of energy of the same quantity as that which the imparting body 

 loses; on the contrary, keeping to the indistinct view of the 

 energies having acted their parts when certain material results 

 have been produced, we have not as yet formed a clear idea of 

 the general proportion between the acting and the producing 

 forces. Thus, for example, when the mechanical energy con- 

 tained in a quantity of water falling upon a water- wheel drives a 

 saw-mill, then it produces every moment a certain material 

 result, but the corresponding mechanical energy itself is lost. 

 Or when heat, developed by burning coal under a steam-boiler, 

 moves a corn-mill by means of a steam-engine, then the heat 

 likewise every moment produces a material result, at which the 

 common idea stops ; but the energy of heat which has produced 

 this result exists no more, and w^e say it has become latent. In 

 the same manner, when the electrical current developed by che- 

 mical forces is performing a certain work by means of an electro- 

 magnetic machine, then its energy disappears during the work, 

 &c. That new forces, as heat, electricity, &c, are developed 

 along with the material work is indeed well known ; but this is 

 generally considered a secondary thing. This view has, how- 

 ever, always appeared to me a very unpleasant one; and I 

 think, on the contrary, that the only natural view of this subject 

 is, as I explained before : That the forces by no means vanish in 

 matter, and consequently it must be a general law of nature that 

 the forces, without exception, undergo a mere change when they 

 seem to vanish, and afterwards reappear as active sources of power 

 of the same quantity but under different forms*. 



If the alleged proposition is correct, it is evident that the 



* See Die organische Bewegung in ihrem Zusammenhange mit dem 

 Stoffwechsel, by I)r. J. R. Mayer (Heilbronn, 1845) ; and Helmholtz, Ueber 

 die Erhaltung der Kraft (Berlin, 184 7). 



