36 
cuprous 'chloride and cupric chloride were formed and car- 
ried down into the fissures below, where, by the action of a 
heat which need not have exceeded 160°, the cuprous 
chloride (for the cupric chloride would be completely 
reduced to cuprous chloride by the action of the iron pyrites 
which is universally present in all crystalline and meta- 
morphic rocks) was decomposed into cuprite and cupric 
oxide and deposited in the fissures or lodes. The ferric 
sulphate simultaneously formed in the reduction of the 
cupric chloride would eventually decompose into hydrated 
ferric acid and accompany the cuprite in the lodes, whilst 
the free hydrochloric acid formed in this process would 
readily attack the neighbouring rocks, thus causing the 
deposition of gelatinous silica in the lodes. 
It will now be my next endeavour to study the chemical 
composition of all the rocks occurring in the immediate 
neighbourhood of copper mines, and particularly the evidences 
of decomposition of these rocks at the place of contact with 
the metalliferous lode, in order to ascertain whether the 
above conclusions are correct. In a future communication 
I hope to deal with the statement made by great authorities 
on this subject, that the sulphides of copper are the primary 
and oldest compounds of that metal. 
" On the Construction of a Room or Series of Rooms free 
from Germ Life, proposed for use in the performance of 
Surgical Operations,” illustrated by a Model Room and 
Apparatus, by William Thomson, F.R.S.E. 
My object in bringing this paper before the Society is to 
show what I consider to be a valuable application of a well- 
known principle, viz. : that of filtering from the ordinary 
air the innumerable spores which are constantly found 
floating about in it, and so to arrange a room or series of 
rooms, in which the air may be rendered optically pure* 
The practicability of producing, and afterwards retaining 
