ago 



INDUCTION. 



from oxygen and hydrogen, we should 

 have been forced to wait until the 

 casual thought struck some one of 

 passing an electric spark through a 

 mixture of the two gases, or inserting 

 a lighted paper into it, merely to try 

 what would happen. Besides, many 

 substances, though they can be ana- 

 lysed, cannot by any known artificial 

 means be recompounded. Further, 

 even if we could have ascertained, by 

 the Method of Agreement, that oxy- 

 gen and hydrogen were both present 

 when water is produced, no experi- 

 mentation on oxygen and hydrogen 

 separately, no knowledge of their 

 laws, could have enabled us deduc- 

 tively to infer that they would pro- 

 duce water. We require a specific 

 experiment on the two combined. 



Under these difficulties, we should 

 generally have been indebted for our 

 knowledge of the causes of this class 

 of effects, not to any inquiry directed 

 specifically towards that end, but 

 either to accident, or to the gradual 

 progress of experimentation on the 

 different combinations of which the 

 producing agents are susceptible ; if 

 it were not for a peculiarity belong- 

 ing to effects of this description, that 

 they often, under some particular com- 

 bination of circumstances, reproduce 

 their causes. If water results from 

 the juxtaposition of hydrogen and 

 oxygen whenever this can be made 

 sufficiently close and intimate, so, on 

 the other hand, if water itself be 

 placed in certain situations, hydrogen 

 and oxygen are reproduced from it : 

 an abrupt termination is put to the 

 new laws, and the agents reappear 

 separately with their own properties as 

 at first. What is called chemical ana- 

 lysis is the process of searching for 

 the causes of a phenomenon among its 

 effects, or rather among the effects 

 produced by the action of »ome other 

 causes upon it. 



Lavoisier, by heating mercury to a 

 high temperature in a close vessel 

 containing air, found that the mercury 

 increased in weight, and became what 

 waa then called red precipitate, while 



the air, on being examined after the ex- 

 periment, proved to have lost weight, 

 and to have become incapable of sup- 

 porting life or combustion. When 

 red precipitate was exposed 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 precipi- 

 tate when acted upon by heat. So, 

 if we decompose water by means of 

 iron filings, we produce two effects, 

 rust and hydrogen : now rust ia 

 already known, by experiments upon 

 the component substances, to be an 

 effect of the union of iron and oxy- 

 gen : the iron we ourselves supplied, 

 but the oxygen must have been 

 produced from the water. The re- 

 sult therefore is that water has dis- 

 appeared, and hydrogen 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 exist- 

 ence, and the causes of water are 

 found among its effects. 



Where two phenomena, between the 

 laws or properties of which, considered 

 in themselves, no connection 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 transforma- 

 tion. The idea of chemical composi- 

 tion is an idea of transformation, but 

 of a transformation which is incom- 

 plete, since we consider the oxygen 

 and hydrogen to b© present in the 

 water at oxygen and hydrogen, and 

 capable of being discovered in it if our 

 semes were tufficiently keen ; a tup- 



