180 MR, W. THOMSON ON THE CONSTRUCTION OF 



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 evi- 

 dences of decomposition of these rocks at the place of con- 

 tact 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. 



XXIII. On the Construction of a Room or Series of Rooms 

 free from Germ Life, proposed for use in the perform- 

 ance of Surgical Operations. By William Thomson, 

 r.R.S.E. 



Read November 27th, 1877. 



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 



