970 REPORT—1885. 
As regards physical properties, the alkyl compounds (methides, ethides, pro- 
pides, &c.) of the elements exhibit exactly the same relationships as the correspond- 
ing halogen compounds; hence the allyl radicals, methyl, ethyl, propyl, &c., have 
the same function in these compounds as the halogens, chlorine, bromine, and 
iodine. 
Further, the halogen or alkyl compounds of the hydrocarbon radicals exhibit 
exactly the same relationships as those exhibited by the corresponding compounds 
of the elements, even when these relationships are of the most minute and intricate 
kind. The relationships, in the case of both elements and hydrocarbon radicals, 
and for either their halogen or alkyl compounds, are strictly periodic, the several 
periods corresponding exactly with the series of elements usually given in tables 
representing the natural classification of the elements according to the Periodic 
Law. 
It may, therefore, be inferred that the elements are built up of (at least) two 
primary elements, A and B, which by their combination produce a series of 
compounds (viz., our present elements) which are analogous to the hydrocarbon 
radicals. 
If the above theory as to the constitution of the elements be true, the Periodic 
Law would follow as a matter of course, and we should therefore be able to 
represent the elements by some such general formula as An Bonr+(2—x), analogous to 
that for the hydrocarbon radicals, C,H2n+(2—2), in which n=the series, and w the 
group to which the element or hydrocarbon radical belongs. 
4. On the Value of the Refraction Goniometer in Chemical work. 
By Dr. J. H. Guavstone, F.R.S. 
The principal points illustrated and enforced in this communication were: 
The index of refraction and the length of the spectrum are important physical 
properties of any substance. 
The specific refraction and specific dispersion may be serviceable: 1st, in de- 
termining the purity of a substance; 2nd, in the analysis “of such mixtures as 
ethylic and methylic alcohols ; 3rd, as a guide in the investigation of organic sub- 
stances; 4th, as an arbiter between rival theories as to the constitution or structure 
of particular chemical compounds. 
The double or treble refraction equivalents of carbon, oxygen, nitrogen, sulphur, 
phosphorus, iron, chromium, silicon, &c. offer a specially promising field of research. 
5. On the Refraction of Fluorine.’ By Grorcr Guapstone, F£.0.8. 
The author gave data for a more exact determination of the effect of fluorine 
on the refraction of light than has hitherto been published. A comparison of 
observations on fluor spar, cryolite, and various artificial compounds containing 
fluorine, showed that the refraction equivalent of this body must be considerably 
less than was previously supposed, and that it ranges between 0°3 and 0°8, the 
mean of the whole being 0°6; and that the specific refraction can, at the highest 
estimate, be scarcely equal to the half of that of any other substance Inown. 
6. Note on some Conditions of the Development, and of the Activity, of 
Chlorophyll. By Professor J. H. Gitpert, LL.D., F1.8. 
All who are accustomed to observe vegetation must have been struck with the 
great variety of shades of green which the foliage of different plants presents. With- 
out pretending to generalise further, it may be stated that, at any rate so far as our 
common agricultural plants are concerned, they show somewhat characteristic shades 
of colour, according to the Natural Order to which they belone—the Leguminosze 
1 Published in eatenso in the Phil. Mag. December, 1885. 
