536 THE POPULAR SCIENCE MONTHLY. 



and mercury on the other, form, it is true, notable exceptions ; never- 

 theless, the bulk of the facts sustain this law, and indicate that the 

 genesis of those elements which we know only as solids or liquids, and 

 which we have supposed to have taken place during the fiery ordeal 

 through which the solar system has had to pass, is rather a process of 

 integration than of subdivision, since they have much larger mole- 

 cules than the gases that exist in the nebulfe, and out of which we 

 have supposed them to be formed. 



We have seen that matter, in its cosmical history, as enacted in the 

 development of a planetary system, assumes a great variety of forms, 

 and resolves itself into numerous specifically distinct molecular aggre- 

 gates. The different substances which we know on our planet are the 

 result of the cohesion into homogeneous masses of these different ag- 

 gregates, all the constituent units of any one of these masses consist- 

 ing of the same species of molecular aggregate. "We saw reason to 

 suppose that, at an early period in the development of the solar system 

 (and we may infer the same for all systems), the number of distinct 

 substances was small, and that these substances were gaseous at very 

 low temperatures. The two abundant gases, nitrogen and hydrogen, 

 exist in the irresolvable gaseous nebulae, and these, doubtless, went far 

 to constitute the original substance of our infant system. These 

 gases, though differing greatly from each other in their atomic weights, 

 nevertheless have small molecules compared with those of most sub- 

 stances now found in the earth, and which are, for the most part, either 

 solid or liquid at life-supporting temperature^ There has, therefore, 

 been upon the w^hole increase of mass among the molecules of sub- 

 stances later developed. 



When we rise to the point of view which removes all distinction 

 between elements and compounds, except the subjective one that in 

 the former we do not know and cannot prove their composition, while 

 in the latter we can do this in so far as to resolve them into the former, 

 we can make the further generalization that along with this increase 

 of mass there has gone decrease of stability in such molecules. We 

 are of course unable to predicate this, except inferentially, of the ele- 

 ments which we can not decompose, although these, doubtless, vary 

 greatly in their relative stability, and, as before remarked, some sub- 

 stances which had been supposed to be elementary have already been 

 reduced to simpler forms, and others may still be so reduced. More- 

 over, those which have thus yielded possess large molecules (counting 

 that of the compound), and this should serve as an index to future 

 attempts of a like nature. There is, for example, little hope of re- 

 solving hydrogen or carbon into simpler elements, but the reverse of 

 the alchemist's dream may yet be realized, and gold reduced, if not to 

 baser, at least to simpler materials. 



All the known chemical compounds must be supposed to have been 



