2 Mr. D. Forbes's Researches on the 



Ctenodonta, &c. ; in fact hand specimens were obtained consist- 

 ing of ore and veinstone containing, in the latter, fossils in a 

 perfectly recognizable condition. 



The geological examination of the environs appeared to prove 

 that this and other veins in the neighbourhood had been pro- 

 duced by the eruption of the large mass of granite (auriferous) 

 farther to the west, with which the veins are most probably con- 

 temporaneous. 



The age of the granite itself was considered to be of the middle 

 Silurian period. 



The minerals found present in this vein were — Danaite or 

 cobaltiferous mispickel, mispickel, bismuth, bismuth-glance, bis- 

 muth-ochre, carbonate of bismuth, telluric bismuth, gold, apa- 

 tite, iron pyrites, zincblende, tourmaline, epidote, calcspar, and 

 quartz. The main mass of the lode was Danaite, which also 

 formed the base for the mining exploration. 



The native bismuth was found more abundantly on the sur- 

 face of the vein, and became very rare as the workings in the 

 mine increased in depth; it occurred in irregular lumps or 

 masses, and frequently as if wedged in between the walls of the 

 lode. The largest mass found in one piece weighed about 400 

 pounds, and had one side entirely overlaid with a thin plate 

 of gold of a rather light colour, not more than 0*05 inch in thick- 

 ness, adherent and as if soldered to the bismuth. 



No crystals of bismuth were observed; but on fracture the 

 basal cleavage was perfect, and the fresh surfaces showed the 

 peculiar reddish-white colour so characteristic of this metal. 



The specific gravities of two separate specimens quite free from 

 extraneous matter were found respectively to be 9*98 and 9*77 

 at 60° Fahr. The analysis was conducted as follows : — 



The arsenic was determined by fusing 25*08 grs. in fine 

 powder, with a mixture of 80 grs. pure nitrate of potash along 

 with 100 grs. pure carbonate of soda in a silver crucible; the 

 mass was extracted with water, acidified by hydrochloric acid, 

 and the arsenic precipitated as arseniate of magnesia and ammonia 

 by the addition of a mixture of ammonia, chloride of ammonium, 

 and sulphate of magnesia. 0*270 gr. arseniate of ammonia and 

 magnesia were obtained, equivalent to 0*097 arsenic^ or to 0*38 

 per cent, arsenic in the bismuth. 



The sulphur was determined by suspending 50'01 grs. bis- 

 muth in finest powder in a solution of potash, and passing a 

 stream of chlorine gas through until all the bismuth was oxidized 

 (this required a very long time) ; the solution was then rendered 

 more acid by addition of hydrochloric acid to prevent any tellu- 

 rate of barytes being simultaneously precipitated, and the sul- 

 phuric acid precipitated by the addition of chloride of barium. 



