174 Mr. D. Forbes' s Researches in 



nifier, consisted of polytelite, along with some little galena and 

 considerable amount of iron pyrites, blende and copper pyrites, 

 and a little quartz sand ; whilst the lighter or earthy portion con- 

 sisted chiefly of quartz and rock debris, along with some few 

 specks of polytelite, copper and iron pyrites, and blende. 



The assay of these three ultimate products of this experimental 

 washing now showed the distribution of the silver as follows : — 



(1) The heavier or argentiferous galena, which corresponded 

 to the dressed ore obtained on the large scale in the Company's 

 operations contained 60 ounces of silver per ton, along with 

 about 80 per cent, of lead. On the large scale it is stated, in the 

 before-mentioned report, that the results varied from 55 to 78 

 per cent, of lead, along with from 45 to 53 ounces of silver per 

 ton washed ore. 



(2) The less dense metallic part, which evidently contained 

 most of the polytelite, and the greater part of which would, in 

 the ordinary process of washing on the large scale as adopted at 

 Tyddynglwadis, have been carried away and lost, was far richer 

 than the preceding, and contained 182 ounces of silver to the ton, 

 with a little lead and more copper and zinc. 



(3) The third product consisted of the lighter non-metallic 

 particles, chiefly quartz and rock debris, along with traces of the 

 lighter metallic compounds, and only contained a mere trace of 

 silver. 



Sulphide of Iron and Nickel. 



Locality : nickel mine in the woods above Inverary Castle, 

 Argyleshire ; the mineral occurring in a lode running nearly east 

 and west with a dip of about 42° to the north, which traverses 

 the metamorphic slates and schists. 



The characters of this mineral were as follows : — massive ; 

 fracture between granular and semicrystalline ; brittle; opake; 

 lustre metallic ; colour light bronze-brown ; streak greyish black; 

 powder bronze-brown ; hardness 3*5, scratching calcite but not 

 fluor-spar; strongly magnetic. Specific gravity 4*50 at 60° F. 

 After some time, on exposure to the air the mineral crumbles to 

 pieces, some specimens breaking up after a few months, whilst 

 others have resisted as many years. 



Heated in a closed tube it remains unchanged, but occasionally 

 shows traces of a sublimate of sulphur on the sides of the tube, 

 whicli possibly may be due to the presence of an admixture of 

 iron pyrites. Heated in an open tube it evolves sulphurous acid. 



On charcoal alone it does not decrepitate, but fuses readily to 

 a globule, which upon breaking possesses a bronze-yellow frac- 

 ture and metallic glance. When this globule is treated with 

 borate in the oxidating-flame, it by degrees gives up all its iron 



