M. Pasteur on Aspartic and Malic Acids. 279 



the problem of celestial motions all the. simplicity which can be 

 consistent with its nature. 



In the case of chemical phsenomeua, on the contraiy, the 

 mechanical conditions of the motions and even their phases are 

 hidden from us. We are ignorant of the form and intimate con- 

 stitution of the coi'puscles which react upon each other. These 

 themselves, as well as the intervals which separate them, escape 

 the observation of our senses ; so that we are unable to ascertain 

 both the relations between their dimensions and their mutual di- 

 stances, or in what proportions the latter vary. The particular 

 forces which each corpuscle exercises within these inappreciable 

 limits of variation are unknown to us. The only character which 

 we are able to attribute to them is, that they decrease with such 

 rapidity when the distance is augmented that they become in- 

 efficacious at all distances sensible to us. Moreover these forces 

 alone do not determine the phsenomena, or at least their influence 

 is not absolute ; for we invanably see their effects modified by 

 the intervention of imponderable principles, which we employ as 

 agents without knowing in what their nature consists, or in 

 what manner they contribute to the production of the observed 

 results. Lastljr, to increase the complication, the actions thus 

 exercised are so powerful, that the respective masses of the cor- 

 puscles undergo a convulsive change which resolves them into 

 less complicated groups, or causes them to aggregate into new 

 ones. These convulsive alterations represent to us those 

 which, in proportions vastly magnified, would take place in the 

 fluids which cover oui- terrestrial spheroid, if the cosmical bodies 

 which cause their successive rise and fall were to approach suffi- 

 ciently near to its solid nucleus to remove them wholly or in 

 part from its influence. 



In this absence of direct data to set about the solution of a 

 problem so complicated, modern chemistry — to its honour be 

 it said — has not remained a pure science of facts. In propor- 

 tion as its progress has brought to light an enormous number of 

 facts, it became necessary to systematize them in accordance with 

 their most apparent relations. This labour of coordination has 

 brought to light those empirical laws, which, wdthin the sphere of 

 application which each one embraces, enable us to foretell almost 

 infallibly all the analogous results which ought to be produced, 

 if not extending to all their details, at least in all the general 

 circumstances of their fulfillment. From these all the inductions 

 have been drawn, which, in the majority of cases, proves with 

 great probability what mode of decomposition, of recomposition, 

 or of mutual replacement, must have mechanically taken place 

 in the substances placed in contact, and what systems of corpus- 

 cular groups have been defluitely disunited or formed in their 



