130 Mr. D. Forbes' s Researches on the 



have been the prime cause of the gold being present. These 

 banks are flushed away by water, and the gold left behind 

 collected. 



The gold from these washings is extremely uniform in appear- 

 ance, possesses a very fine colour, and is considered to be some 

 of the purest of the whole district, and is invariably found in 

 fine scales or plates — very thin, as if beaten out, and from the 

 most minute size up to an eighth or even a quarter of an inch in 

 diameter, but very rarely larger, and has frequently its natural 

 colour heightened by a varnish, as it were, of oxide of iron 

 adhering firmly to it. 



Its specific gravity was determined on 210*48 grs. of these 

 scales, and found to be 18 "31 at 60° F. 



Two analyses were made of this gold. In the first case 14*472 

 grs. of these scales were dissolved in nitrohydrochloric acid, 

 leaving behind 0*99 gr. chloride of silver, equal to 0*755 gr. 

 silver ; and the solution precipitated by oxalic acid gave 13*698 

 grs. pure gold, after separating which, a little sesquioxide of iron 

 was precipitated by ammonia, and weighed 0*02 gr., equal to 0*013 

 gr. metallic iron, although it is more than probable that this 

 iron in reality was derived from the ferruginous varnish before 

 alluded to. 



In the second analysis 20*03 grs. were used, giving 1*39 

 gr. chloride of silver, equal to 1*049 metallic silver, and the 

 gold was estimated as loss. These results give the following 

 percentage composition : — 



Average. 

 Gold. . . . 94*64 94*76 94*73 



Silver . . . 5*22 5*24 5*23 



Iron .... 008 trace 004 



99*94 10000 10000 



No trace of copper was discovered. 



Gold from Piaya Gritada. — At this place the gold is washed 

 out of the bed of the river itself, which is turned off the one half 

 of its bed by dams ; and after extracting the gold, the other half 

 is in its turn treated in a similar manner. The gold, although 

 more or less distributed throughout the whole mass composing 

 the bed of the river, is found in greatest quantity on the rock 

 bed below all the gravel, sand, &c. ; and in this locality the firm 

 rock (Silurian clay-slate) is covered by no less than 30 feet of 

 stones, gravel, and sand, which must be removed before the gold 

 is reached. 



Silurian age, but a more exact examination of the fossils found in the rocks 

 altered by this granite leads Mr. Salter to think that some of the species 

 may be Upper Silurian, and consequently the granite must be considered 

 to be as late as the Devonian period. 



