WISLIZENUS — THOUGHTS ON MATTER AND FORCE. 301 



of Forces) will give but a brief summary of our present 

 knowledge thus acquired : 



" Forces are causes, in which full application of the axiom 

 must be found, that every cause must produce an effect which 

 corresponds and is equal to the cause. Causa squat affectum. 

 All these causes as far as relates to their quantity, possess 

 the property of indestructibility, and to their quality, of con- 

 vertibility." — Dr. Mayer. 



" We cannot create force any more than we can create 

 matter; neither can we annihilate either of them. 



" When a body falls to the ground by the force of gravi- 

 tation, or if by some mechanical motion a body is thrown 

 upon another, it was formerly supposed that the force of 

 impact was lost by the fall, concussion, friction, or com- 

 pression. We now admit no loss, but assume that it is 

 simply a case of transference and not of annihilation — the 

 mechanical motion is transferred into heat. 



" When a weight falls down and strikes the earth, its 

 motion is stopped, and partly reappears as heat in both 

 earth and weight; partly it conveys away or continues 

 the force expressed by the cohesion of the weight (its 

 specific gravity) to the earth, by making the latter vi- 

 brate through its mass, and changing its position in the 

 universe by increase of gravity. 



" Whenever friction is overcome, heat is produced, and the 

 heat produced is the measure of the force expended in over- 

 coming the friction. 



"The quantity of heat generated by the same amount of 

 force is fixed and invariable. Vice versa, heat is thus con- 

 verted into mechanical energy. 



"The grand principle of conservation of force is well- 

 illustrated, in the steam engine. For every stroke of work 

 done by the steam engine, for every pound it lifts, and for 

 every wheel it sets in motion, an equivalent of heat disap- 

 pears. 



" Where the mutual impinging bodies are homogenous, 

 heat alone is the result of friction and percussion. Where 

 the bodies impinging are heterogeneous, electricity and heat 

 are produced. 



" Of the various forces of matter, either of them may me- 

 diately or immediately produce the others. Where at pres- 

 ent no immediate relation is established, electricity gene- 

 rally forms the intervening link of middle term. 



"A great number of bodies chemically combine in equal 

 volumes, that is, in the ratios of their specific gravities. 

 Here we have, to some extent, an equivalent relation between 

 gravitation and chemical affinity. 



" Faraday, Brucke, Airy, Chase, and others, have consid- 

 ered the mutual convertibility of gravitation and magnetism, 



