and the Theory of Mechanical J'ypes. 505 



hydrogen, it is of importance to remark here, that M. Laurent 

 insisted on the identity of the function of the chlorine with 

 that of the hydrogen in bodies formed by substitution long 

 before it had been positively established by experience. 



It will not be my object now to write the history of the 

 theory which occupies us ; when experience shall have sounded 

 all the parts in succession, it will be useful to go into the dis- 

 cussion of the a -priori ideas which may have often predicted 

 the results. 



Thus putting aside every historical question, and stopping 

 only at facts, at the experiments which have served as a basis 

 to my own convictions, in a word, consulting only my per- 

 sonal impressions, I must say, that the first results in which 

 I believed I could recognise in a decisive manner the ele- 

 ments of a view arrested by this subject, are those which or- 

 ganic chemistry owes to M. Malaguti. In fact, we know that 

 this skilful observer has recognised, that aether, whether free 

 or combined, may always lose two equivalents of hydrogen 

 and gain two equivalents of chlorine, without any of its es- 

 sential chemical characters undergoing alteration ; for its 

 power of combination remains exactly the same ; chloridated 

 aether then is still aether. 



My conviction became complete, when I was able to re- 

 cognise the precise nature of chloracetic acid, and when I saw 

 chlorine take the place of all the hydrogen of the acetic acid, 

 without modifying its capacity of saturation, without in any 

 way altering what I term its fundamental properties ; chlo- 

 ridated acetic acid then is still acetic acid. 



It is by setting out from these two facts, it is by adding 

 those which M. Regnault had himself observed in the action 

 of chlorine on the liqueur des Hollajidais, that I have tried to 

 show that there exist, in organic chemistry, types capable of 

 undergoing, without being destroyed, the most singular trans- 

 formations as to the nature of their elements. 



More recently M. Regnault, in the memoir on the Aethers 

 which I have already quoted, giving a still greater extension 

 to those views, considered the bodies formed by substitution 

 as belonging to one mechanical system. We may wait with 

 confidence for the developments which he promises to give to 

 these first views. 



[To be continued.] 



