470 MANCHESTER CHEMISTS AND DRUGGISTS’ ASSOCIATION. 
Mr. Siebold in commencing, referred briefly to the great changes which the science 
of Chemistry has undergone within the last fifteen years. He illustrated volumetric 
composition by reference to, and diagrams of, hydrochloric acid, ammonia, and steam, 
and showed that the smallest quantity of any gaseous compound which can be produced 
from its elementary constituents, measures two volumes ; he also reviewed the ponderal 
composition of the three substances named, and pointed cut the identity of the com¬ 
bining weights with the vapour-densities of nearly all elementary substances. 
He next spoke on the law of combination in definite and unalterable proportions and 
in multiple proportions, and then proceeded to the consideration of the divisibility of 
matter. He defined molecules as the smallest particles of matter resulting from a divi¬ 
sion by mechanical and physical means, and atoms as the smallest particles of elemen¬ 
tary substances resulting from the chemical decomposition of molecules. He explained 
that all molecules must be of equal size, and showed that the atoms of elementary sub¬ 
stances fill half the space of a molecule, with the exceptions of phosphorus and 
arsenic, whose atoms are one-fourth of a molecule, and mercury and cadmium, whose 
atoms are equal to a molecule. He showed that a molecule of hydrogen would consist 
of two atoms of hydrogen. The lecturer then compared matter in the solid, liquid, 
and gaseous state, and spoke of molecular attraction or cohesion as being most active in 
solids; and of molecular repulsion keeping apart at longer distances the molecules of a 
gas. The theory that the spaces between the molecules of a gas are occupied by 
spheres of latent heat, he supported by strong and convincing arguments, based on 
experiments. After dwelling at some length on quantivalence, or the atom-fixing and 
atom-replacing power of elementary substances, Mr. Siebold pointed to the import¬ 
ance and enormous utility of the modern molecular and atomic theory, laying stress 
on its services to organic chemistry and to the artificial preparation of organic substances 
from their elementary constituents, and concluded by thanking his audience for their 
attention. 
Mr. Siebold’s lecture was listened to with very great pleasure; the ease and fluency 
with which it was delivered being the more remarkable, from the fact that the lecturer 
is a German, and was speaking in English without the help of notes. 
The next meeting will be held on Friday, February 4th, at 3 p.m. 
Mr. Wilkinson will read a paper on the “Additions to the Poison Schedule, and the 
Proposed Regulations as to the Keeping of Poisons.” 
ABERDEEN ASSOCIATION OF ASSISTANT CHEMISTS AND DRUGGISTS. 
The Second Annual Assembly of this Association was held in the Mechanics’ Hall, 
Market Street, on Thursday, January 6th, 1870; Mr. James Thom, President, in the 
chair. 
The objects of the meeting were of a social and convivial character, commencing with 
tea and terminating with a ball. 
The Chairman, at the conclusion of the first part of the proceedings, delivered a 
short address, in which he referred to the objects of the Association, viz. the improve¬ 
ment of its members in the scientific details of the business of a Chemist and Druggist; 
he also alluded to the prospective appearances of the future progress of the Association, 
and the benefits to Assistant-Druggists of having opportunities of meeting together. 
The meeting consisted of about a hundred and thirty members and their friends, in¬ 
cluding several masters, and among them Mr. Kay, of Messrs. C. Davidson and Co., 
along with Mrs. Kay ; Messrs. G. and W. Shepherd, jun., of Messrs. Souter and Shep¬ 
herd ; Mr. H. Paterson, of Messrs. W. Paterson and Sons; Mr. Duncan, Castle Street; 
and Mr. Ross, Castle Street. 
It is gratifying to state that on this occasion the masters allowed those in their 
respective shops to leave earlier than usual. 
