THE LAW OF SUBSTANCE. 227 



probable that they are not absolute species of ponder- 

 able matter — that is, not eternally unchangeable 

 particles. The seventy elements have in that system 

 been distributed into eight leading groups, and 

 arranged in them according to their atomic weight, 

 so that the elements which have a chemical affinity 

 are formed into families. The relations of the 

 various groups in such a natural system of the 

 elements recall, on the one hand, similar relations 

 of the innumerable compounds of carbon, and, again, 

 the relations of parallel groups in the natural arrange- 

 ment of the animal and plant species. Since in the 

 latter cases the " affinity " of the related forms is 

 based on descent from a common parent form, it 

 seems very probable that the same holds good of 

 the families and orders of the chemical elements. 

 We may, therefore, conclude that the " empirical 

 elements " we now know are not really simple, 

 ultimate, and unchangeable forms of matter, but 

 compounds of homogeneous, simple, primitive atoms, 

 variously distributed as to number and grouping. 

 The recent speculations of Gustav Wendt, Wilhelm 

 Preyer, Sir W. Crookes, and others, have pointed out 

 how we may conceive the evolution of the elements 

 from a simple primitive material, the prothyl. 



The modern atomistic theory, which is regarded 

 as an indispensable instrument in chemistry to-day, 

 must be carefully distinguished from the old philo- 

 sophic atomism which was taught more than two 

 thousand years ago by a group of distinguished 

 thinkers of antiquity — Leucippus, Democritus, and 

 Epicurus : it was considerably developed and modified 

 later on by Descartes, Hobbes, Leibnitz, and other 

 famous philosophers. But it was not until 1808 that 



