ATOM. 



of all the molecules which did not fall under one of the very limited 

 of kinds known to us; and to get rid of a number of indestructible 

 exceeding by fer the number of the molecules of all the recognised 

 kinds, would be one of tot seraest labours ever proposed to a cosmogonist. 



* well known that living beings may be grouped into a certain number 

 of species, defined with more or less precision, and that it is difficult or im- 

 possible to find a tfltfr^ of individuals forming the links of a continuous chain 

 holms* one species and another. In the case of living beings, however, the 

 generation of individuals is always going on, each individual differing more or 

 less from its parents. Each individual during its whole life is undergoing 

 modification, and it either survives and propagates its species, or dies early, 

 accordingly as it is more or less adapted to the circumstances of its environ- 

 ment. Hence, it has been found possible to frame a theory of the distribution 

 of organisms into species by means of generation, variation, and discriminative 

 destruction. But a theory of evolution of this kind cannot be applied to the 

 case of molecules, for the individual molecules neither are born nor die, they 

 have neither parents nor offspring, and so far from being modified by their en- 

 vironment, we find that two molecules of the same kind, say of hydrogen, 

 have the same properties, though one has been compounded with carbon and 

 buried in the earth as coal for untold ages, while the other has been "oc- 

 cluded " in the iron of a meteorite, and after unknown wanderings in the 

 heavens has at last fallen into the hands of some terrestrial chemist. 



The process by which the molecules become distributed into distinct species 

 is not one of which we know any instances going on at present, or of which 

 we have as yet been able to form any mental representation. If we suppose 

 that the molecules known to us are built up each of some moderate number 

 of atoms, these atoms being all of them exactly alike, then we may attribute 

 the limited number of molecular species to the limited number of ways in 

 which the primitive atoms may be combined so as to form a permanent system. 



But though this hypothesis gets rid of the difficulty of accounting for the 

 independent origin of different species of molecules, it merely transfers the diffi- 

 culty from the known molecules to the primitive atoms. How did the atoms 

 come to be all alike in those properties which are in themselves capable of 

 assuming any value ? 



If we adopt the theory of Boscovich, and assert that the primitive atom 

 is a mere centre of force, having a certain definite mass, we may get over the 



