8 ROYAL SOCIETY OF CANADA 
contain chlorine, and in the case of beryl, which Penfield has shown to 
contain alkalies (soda, lithia and cæsia) replacing beryllia to the extent 
of from 0:25 per cent up to 5 per cent. 
Thus far attention has been called mainly to questions in connection 
with the practical or laboratory side of mineral chemistry, but 1 wish also 
to say a few words with regard to some of the recent developments on the 
theoretical side. And here let me remark that there seems even to-day to 
be a vague impression in the minds of many that the chemistry of natural 
minerals is in some way distinct from that of bodies produced by artificial 
methods—an ill-defined idea that the laws regulating the production of 
chemical compounds in nature are somehow different from those with 
which the chemist has to deal in his laboratory. I need scarcely say that 
this is a mistaken idea. The laws are the same in both cases, but the 
bodies formed in nature are often highly complex in their composition, 
involving special methods of investigation and affording problems of 
special character. The existence of a special department of mineralogical 
chemistry depends simply upon convenience. 
Those who are familiar with the efforts that have been made to explain 
the chemical constitution of mineral species know with what great dif- 
ficulties the path is beset. The methods of ascertaining chemical constitu- 
tion and molecular weight made use of in the study of organic compounds 
are rarely available here, where as a rule we have to deal with non-volatile 
bodies and bodies which often resist the action of all ordinary solvents. 
Where chemical reagents have any marked effect the varying power of 
resistance to their action is valuable as pointing to differences of chemical 
or physical constitution. Experiments recently made seem to show that 
marcasite is more rapidly oxydised by potassium permanganate than 
pyrite Clarke, in his study of a number of magnesian minerals, found 
that on heating them for some time in hydrochloric acid gas, part of the 
magnesium was converted into soluble chloride, and drew certain conclu- 
sions as to the condition of the magnesium in the molecule, regarding the 
part dissolved as having been present in combination with hydroxyl as 
—Mg-OH. Whether his conclusions on this subject are always justifiable, 
some may doubt, but no one can fail to recognise the importance of many 
of his results, nor to feel that the line of work which he has taken up is 
in the right direction. The experiments of the late Mr. J. B. Mackintosh 
with regard to the resisting power of different silicates to the action of 


| Berzelius insisted strongly upon minerals being regarded as chemical com- 
pounds whose composition was dependent upon the same laws as that of compounds 
artificially produced. 
2 The results obtained by Prof. Edgar F. Smith with the electric current are 
interesting in this connection. Smith found that a current which would completely 
oxydise the sulphur in marcasite in a given time would oxydise less than half of the 
sulphur in pyrite in the same time. (Jour. Franklin Inst., exxx., pp. 152-154.) 
