142 Mr. D. Forbes' s Researches on the 



Native Tin. — The above analyses of Cassiterite were made in 

 hopes that some light might be thrown upon the occurrence of 

 the metallic tin previously described as occurring in the gold- 

 sands of the river Tipuani. It must, however, be admitted that 

 they do not much tend to dispel the mystery connected with its oc- 

 currence, further than that, as the metallic tin contained so much 

 lead alloyed with it, the idea that it could have originated from 

 the reduction of the Cassiterite in the sands of the river Tipuani 

 must seem very improbable. 



I must, however, add a postscript to this notice, inasmuch as 

 a late post from Bolivia has brought me from Tipuani, enclosed 

 in a letter from a friend, " two crystals of native tin " from the 

 sands of that river • these so-called crystals are small and distinct 

 six-sided prisms of undoubted metallic tin, the one a little over 

 and the other slightly under one quarter of an inch in diameter, 

 and respectively about three-sixteenths and five-sixteenths of an 

 inch in length. The planes bounding the sides are well defined, 

 but oxidized, so as to have no lustre, or permit any very satis- 

 factory measurement of their angles being made. There were 

 no terminal planes on the ends of either of the two specimens 

 here referred to, and the prisms appeared abruptly terminated. 



Summing up the evidence deduced from the facts here pro- 

 duced relative to the occurrence of native tin, I suppose that its 

 existence must be admitted, at least until further evidence is 

 brought forward to prove the contrary. Yet I cannot but retain 

 the impression on my mind that the tin in question does not 

 owe its origin to purely natural causes, however much the balance 

 of evidence goes against me. 



Gold, Carabaya, Peru. — This gold occurs in quartz-veins tra* 

 versing the Silurian slates of the High Andes of the south of 

 Peru on to the confines of Bolivia. The specimen examined was 

 procured from a vein situated in the Montanas de Monte Nello 

 in the Carabaya range. The quartz was colourless or white, and 

 along with the gold contained iron pyrites and a greenish^ 

 coloured silicate of undetermined character. The gold was of a 

 very fine colour, and found to possess a specific gravity equal to 

 18*43 at 60° F. The analysis was conducted in precisely the 

 same manner as that of the specimens of gold previously reported 

 on; and 11*43 grs. afforded 0*38 chloride of silver, or 



Gold . . , . 11-14 97-46 



Silver .... 0-29 2-54 



11-43 10000 



Gold from Rio de Cajones in Yungas. — This gold is derived 

 from the wearing down of the granitic rocks forming in Yungas 

 the eastern slope of the High Andes, where, although the oc- 



