INTERMIXTURE OF EFFECTS. 491 



to have lost weight, and to have become incapable of sup 

 porting life or combustion. When red precipitate was ex 

 posed to a still greater heat, it became mercury again, and 

 gave off a gas which did support life and flame. Thus the 

 agents which by their combination produced red precipitate, 

 namely the mercury and the gas, reappear as effects resulting 

 from that precipitate when acted upon by heat. So, if we 

 decompose water by means of iron filings, we produce two 

 effects, rust and hydrogen : now rust is already known by 

 experiments upon the component substances, to be an effect 

 of the union of iron and oxygen : the iron we ourselves supplied, 

 but the oxygen must have been produced from the water. 

 The result therefore is that water has disappeared, and hydro 

 gen and oxygen have appeared in its stead : or in other words, 

 the original laws of these gaseous agents, which had been 

 suspended by the superinduction of the new laws called the 

 properties of water, have again started into existence, and the 

 causes of water are found among its effects. 



Where two phenomena, between the laws or properties of 

 which considered in themselves no connexion can be traced, 

 are thus reciprocally cause and effect, each capable in its turn 

 of being produced from the other, and each, when it produces 

 the other, ceasing itself to exist (as water is produced from 

 oxygen and hydrogen, and oxygen and hydrogen are repro 

 duced from water) ; this causation of the two phenomena by 

 one another, each being generated by the other s destruction, 

 is properly transformation. The idea of chemical composition 

 is an idea of transformation, but of a transformation which is 

 incomplete ; since we consider the oxygen and hydrogen to be 

 present in the water as oxygen and hydrogen, and capable of 

 being discovered in it if our senses were sufficiently keen : a 

 supposition (for it is no more) grounded solely on the fact, 

 that the weight of the water is the sum of the separate 

 weights of the two ingredients. If there had not been this 

 exception to the entire disappearance, in the compound, of the 

 laws of the separate ingredients; if the combined agents had 

 not, in this one particular of weight, preserved their own laws, 

 and produced a joint result equal to the sum of their separate 



