742 Meeting of the British Association. | Oct., 
the machine had done the work; the sculptor had given the finishing 
touches to the model; and the bust complete, a most striking likeness, 
was then exhibited to the meeting. 
Cuemistry. (Section B.) 
President’s Address.—Daubeny on the Bath Thermal Waters.—Report 
of the Gun-cotton Commitiee—Miller on Wheal Clifford Hot Spring. 
—King on the Frescoes inthe House of Commons.—Calvert on the 
Extraction of Gold from Auriferous Rocks.—Field on Tin Ore, &e.— 
Spence on Copper Smelting. — Papers by Herapath, Catton, Paul, 
Phipson, and Machattie. 
Tue proceedings of the Chemical Section were opened by the Pre- 
sident, Dr. Odling, F.R.S., who, in a short but eloquent address, placed 
before his audience a comprehensive view of the reformation which, 
within the last dozen years or so, has been effected in the opinions 
concerning the combining proportions of the elementary bodies and 
the molecular weights of their most important compounds. The 
development of the matured views of chemical philosophy which now 
prevail must, the President said, be traced to Gerhardt’s division of 
volatile bodies into a majority whose recognized molecules corresponded 
with four volumes of vapour, and a minority whose recognized mole- 
cules corresponded respectively with but two volumes of vapour; and 
from Gerhardt and Laurent’s proposal to double the molecular weights 
of these last, so as to make the molecules of all volatile bodies corre- 
spond each with four volumes of vapour. Prior to the time of 
Gerhardt, the selection of molecular weights for different bodies, ele- . 
mentary and compound, had been almost a matter of hazard. Relying 
conjointly upon physical and chemical phenomena, he first established 
definite principles of selection by pointing out the considerations upon 
which the determination of atomic weights must logically depend. He 
thus established his classification of the non-metallic elements into— 
mon-hydrides, represented by chlorine; di-hydrides, represented by 
oxygen ; ter-hydrides, represented by nitrogen; &c.: and relying upon 
the same principles, later chemists have given to his method a develop- 
ment and unity which have secured for the new system the impregnable 
and acknowledged position which it at present occupies. Dr. Odling 
then made a passing allusion to the researches of Professor Kopp on 
specific heat, and expressed the obligations chemists were under to 
him for the great additions he had made to this subject; and then 
proceeded to the oft-debated question of chemical notation. This is 
at present in anything but a satisfactory state. The sign of addition, 
so frequently used to express the fine idea of chemical combination, is 
about the last one would deliberately select for such a purpose. The 
placing of symbols in contiguity with or without the introduction of a 
point between them is far preferable ; but here, as pointed out by Sir 
John Herschel, we violate the ordinary algebraic understanding, which 
assigns very different numerical values to the expressions ay and 
