No. 7.] WURTZ — THEORY OF AfOJIS'. 387 



distributes their radiations tlirougb all the universe ; arid that 

 which it loses in vibratory energy when it penetrates a cold body, 

 which it warms, it communicates to the atoms of this body and 

 augments the intensity of their movements ; and that which it 

 gains in energy by contact with a warm body, which it cools, it 

 withdraws from this body and diminishes the intensity of their 

 vibratory movements. And this kind of light and heat which 

 comes from material bodies is transmitted across space to other 

 material bodies. You will remember in reference to tliis the 

 words which Goethe put into the mouth of the Prince of Dark- 

 ness in cursinof the lis-ht — '*' It is born of bodies, it is brouirht 

 forth and maintained by bodies, and it will perish with them." 



But this exchange of forces which circulate from ether to ato'ms 

 and from atoms to ether, must it manifest itself always in the 

 phenomena of light or heat? This vibratory force which is 

 transmitted by ether, can it not be preserved and stored up by 

 matter, or appear under other forms? 



It can be preserved as affinity, liberated as electricity, trans- 

 formed into dynamic movements. It is this which is stored 

 up in the innumerable compounds elaborated by the vegetable 

 kingdom ; it is this which provokes the decomposition of carbonic 

 acid and of the vapour of water by the most delicate organs of 

 plants which blossom in the sunlight. Originating with the sun, 

 luminous radiation becomes affinity in the immediate organic 

 principles which are formed and accumulated in vegetable cellules. 

 That mode of motion of ether which was '^lijiht'' is become an- 

 other mode of motion which is "affinity," and sways the atoms 

 of an organic compound. In its turn this force thus stored up 

 is expended again when the organic compounds are destroyed in 

 the phenomena of combustion. Affinity, satisfied and as it were 

 lost by the combination of combustible elements with oxygen. 

 again becomes heat or electricity. "Wood in burning, and carbon 

 in becoming oxidised, produce sparks or flames: a metal whicli 

 exhausts its affinities in decomposing an acid warms the liquid 

 or, under other conditions, produces an electric current, warming- 

 it less when the current is exterior. And in another order of 

 phenomena, heat which distributes or propagates itself unequally 

 between two surfaces, rubbing one against the other, or in ;i 

 crystal that is warmed, or in two metals united by solder, di.s- 

 appears partially as such and manifests itself as static electricity 

 or as an electric current. Thus all these forces are equivalent 



