APE;NDIX a 481 



viduality is so limited by the all-grasping, all-powerful 'universal, that it. Is 

 merely a point of support for the understanding of multitude in unity. 



Having touched upon the metaphysical bases of the conception of a 

 unique matter which is supposed to enter into the composition of all bodies 

 I think it necessary to dwell upon another theory, akin to the above concep- 

 tionthe theory of the compound character of the elements now admitted by 

 someand especially upon one particular circumstance which, being related 

 to tfie periodic law, is considered to be an argument in favour of that hypo- 

 thesis. 



Dr. Pelopidas, in 1883, made a communication to the Russian Chemical 

 and Physical Society on the periodicity of the hydrocarbon radicles, pointing 

 out the remarkable parallelism which was to be noticed in the change of 

 properties of hydrocarbon radicles and elements when classed in groups. 

 Professor Carnelley, in 1686, developed a similar parallelism. The idea of 

 M. Pelopidas will be easily understood if we consider the series of hydro-' 

 carbon radicles which contain, say, 6 atoms of carbon : 



i. n. in. iv. v. vi. vn t vni. 



C 6 H 13 C 6 H 13 C 6 H n C0H 1Q CaHa 6 H 8 6 H 7 



The first of these radicles, like the elements of the 1st group, combines with, 

 Cl, OH, and so on, and gives the derivatives of hexyl alcohol, C e H 13 (OH) ; 

 but, in proportion as the number of hydrogen atoms decreases, the capacity 

 of the radicles of combining with, say, the halogens increases. 6 H W already 

 combines, with 2 atoms of chlorine ; C H U with 3 atoms, and so on. The 

 last members of the series comprise the radicles of ae.ids : thus C 6 H 8 , which 

 belongs to the 6th group, gives, like sulphur, a bibasio acid, 9 H 8 O 2 (OH) 2 , 

 which is homologous with oxalic acid. The parallelism can be traced still 

 further, because C 6 H 5 appears as a monovalent radicle of benzene,- and with 

 it begins a new series of aromatic derivatives, so analogous to the derivatives of 

 the aliphatic series. Let me also mention another example from among those 

 which have been given by M. Pelopidas. Starting from the alkaline radicle 

 of monomethylammonium, N(CH3)H 3 ,- or -NCH 6 , which presents many 

 analogies with the alkaline metals of the 1st group, he arrives, by successively 

 diminishing the number of the atoms of hydrogen, at a 7th group which 

 contains cyanogen, CN, which lias long since been compared to the halogens 

 of the 7th group. 



The most important consequence which, in my opinion, can be drawn 

 from the above comparison is that the. periodic law, so apparent in the 

 elements, has a wider, application than might appear at first sight ; it opens 

 tip a new vista of chemical evolutions. But, while admitting the fullest 

 parallelism between the periodicity of the elements and that of the compound 

 radicles, we must not forget that in the periods of the hydrocarbon radicles 

 we have a* decrease of mass as We pass from the representatives of the first 

 group to the 1 next, while in the periods of the elements the mass increases 

 during the progression. It thus becomes evident that we cannot speak of an 

 identity of periodicity in both, cases, unless we put aside the ideas of mass 

 and attraction* which are the real corner-stones of the whole of natural 

 science, and even enter into those very conceptions of simple substances which 



