164 
BRITISH ASSOCIATION. 
the first to adopt them from us. He gave a system of organic chemistry on that plan, and 
his book has been of immense service to the development of our science. The extension 
of these principles to mineral chemistry had been commenced in the cases of the com¬ 
monest acids and bases, but their general introduction met with difficulties, and some¬ 
times seemed wanting to their complete success. I must now travel southward for a 
short time, and ask you to accompany me to that sunny land of glorious memories, and 
to its southern dependency—the island of Sicily. It was reserved for Professor Canniz¬ 
zaro, of the University of Palermo, to show us how the remainder of the knot could 
be untied. He argued, upon physical as well as chemical grounds, that the atomic 
weight of many metals ought to be doubled, as well as those of oxygen, sulphur, and 
carbon. His conclusions are confirmed by the constitution of those organo-metallic 
bodies which I mentioned just now, and it certainly does seem to supply what was still 
wanting for the extension of our system of classification from the non-metallic elements 
t) the heavy metals themselves. The elements are now arranged into two principal 
groups:—1. Those of which each atom combines with an uneven number of atoms of 
chlorine or hydrogen. 2. Those of which each atom combines with an even number of 
atoms of chlorine or hydrogen. Like every classification founded upon nature, this one 
draws no absolute line, as some elements belong to both classes. The first group in¬ 
cludes the monatomic elements of the chlorine family, the triatomic elements of the 
nitrogen family, hydrogen and the alkali metals, silver and gold,—in all about eighteen 
elements. The usual atomic weights of these are retained. The usual atomic weights 
of all the other elements, biatomic, tetratomic, etc., are doubled. This second group in¬ 
cludes the oxygen family, carbon, silicon, and the alkaline earths, the metals zinc, iron, 
copper, lead, etc. Every step in our theoretical development of chemistry has served to 
consolidate and extend the atomic theory, but it is interesting to observe that the reten¬ 
tion of that theory has involved the necessity of depriving it of the absolute character 
which it at first possessed. Organic compounds were long ago discovered, containing 
atoms of carbon, hydrogen, and oxygen in proportions far from simple ; and the atomic 
theory must have been abandoned but for the discovery that the atomic, or rather 
molecular, weights of these compounds correspond invariably to entire numbers of the 
elementary atoms. We now use the term “molecule ” for those groups which hold to¬ 
gether during a variety of transformations, but which can be resolved into simpler consti¬ 
tuents ; whilst we reserve the word “ atom ” for those particles which we cannot break 
up, and which there is no reason for believing that we ever shall break up. Amongst 
the most brilliant extensions of our means of observation have been the researches in 
spectrum analysis. The application of these beautiful methods to the investigation of 
minerals, has already led to the discovery of three volatile metals which had previously 
escaped observation, whilst its extension to the investigation of the light which reaches 
our planet from the heavenly bodies, has led to the recognition, in several of them, of ele¬ 
ments identical, in this respect at least, with some of our elements in this earth. An emi¬ 
nent French chemist has recently taken occasion, in reporting the results of some researches 
on the new metal “ thallium,” to volunteer insinuations against Mr. Crookes’s claim to 
that discovery. M. Dumas considers it corroborative of his views that Mr. Crookes did 
not refer the consideration of his claims, on the first opportunity, to a jury of gentle¬ 
men, formed for examining products of manufacturing industry at the National Ex¬ 
hibition of 1862. I have felt it my duty to allude publicly to this proceeding, because 
it occurred in a report of a commission of the French Academy, published by the order 
of that distinguished body. 
The following is a list of the papers read in this Section :— 
Address by the President.—Papers on Local Manufactures (Glass and Earthenware). 
Joseph Cowen, Blaydon Burn : Fire-Clay Goods. R. W. Swinburne, South Shields: 
Glass. C. T. Maling, Newcastle: Earthenware.—Professor Wanklyn, F.C.S.: On the 
Oxidation of /3 Hexylic Alcohol.—F. A. Abel, F.R.S.: Some results of Experiments on 
Lucifer Matches and others ignited by Friction.—T. Richardson, Ph.D.: On the presence 
of a Salt of Baryta in Colliery Water.—George Gore, Birmingham: On a New Gas Fur¬ 
nace for Scientific and Practical Purposes.—H. B. Condy, F.C.S., Battersea: On Disin¬ 
fectants.—Report of the Committee on Gun Cotton.—Papers on Local Manufactures. 
J. C. Stevenson, R.C., Clapham, and T. Richardson : Chemical Manufactures.—J. Pattin- 
son : On the various kinds of Pyrites used on the Tyne and neighbourhood for the 
Manufacture of Sulphuric Acid.—Professor Wanklyn : On Fractional Distillation.—Dr. 
