190 Geological Collections. 



The fusible scoriae of the reverberating furnace at Lea, by recasting, 

 would serve very well for this purpose. 



We may also employ a mixture of 88 sulphate of lead, and 12 of chloride 

 of lead ; or 92 sulphate of lead, and 8 of litharge. 



The mixtures which contain a huge quantity of sulphate of lead would 

 have the advantage of great fusibility ; and, from their density, of great stability 

 also, but perhaps they might be too soft. A great porportion of fluor spar, 

 on the contraiy, would produce hardness ; but these mixtures would cost 

 dearer than those in which the sulphate of lead predominates, which is at 

 present at a very low price. It would be very easy to colour the different 

 compounds, by adding some metallic substances, such as chromate of 

 lead, &c. 



TeUurets of Silver and Lead from the Altai Mountains During the journey- 

 through Russia and Siberia, which M. Rose, of Berlin, lately made in the 

 company of MM. Humboldt and Ehrenberg, he found two ores of tellurium 

 in the silver mines of Sawodinski, near those of Siranowski, at the river 

 Buchtharma ; and as this metal has hitherto been only found in the gold 

 mines of Transylvania and in Norway, this discovery is of the greatest 

 interest. We extract the description of tellurium-silver and tellurium-lead 

 as it is given by M. Rose in Poggendorff's Annalen. 



He first saw these two ores in the Museum of the town of Barnoul, near 

 the river Ob ; besides numerous smaller pieces, there were two large blocks 

 of about a cubic foot each, which, on account of their malleability, and the 

 large quantity of silver they contained, were considered to be silver-glans, 

 (sulphuret of silver,) from which they, however, were found to differ greatly. 

 Tellurium-silver is of granular texture, not crystallized nor cleavable ; has 

 much metallic lustre, and its colour is between that of lead and steel : it is 

 malleable, though to a less degree than silver-glans ; and its specific gravity 

 was found, by two different experiments, to be 8.565 and 8.412. The 

 specimens which were examined by M. Rose were adhering to greenish 

 gray talc slate, and the ore was mixed with black blende, small quantities of 

 sulphate of iron and of copper, and tellurium-lead. 



When tellurium-silver was heated before the blowpipe on charcoal, it 

 fused to a black mass, which, on cooling, became covered with numerous 

 white points and ramifications of metallic silver. It fused also in open and 

 closed vessels ; and, when ignited in a retort, tinged the glass with which it 

 was in contact of a yellowish colour : in the open tube it deposited a small 

 quantity of white sublimate, part of which was volatilized by directing the 

 flame upon it, the rest contracting into small globules. 



According to the first analysis, tellurium-silver consists of — 

 Silver . . . . 62.42 



Tellurium . . . . 36.96 



Iron 0.24 



According to the second, of — 



Silver .... 62.32 



Tellurium . . . . 36.89 



Iron 0.50 



And if tellurium-silver be considered as a compound of one atom of silver 

 = 62.63, and one of tellurium = 37.37, the above results are nearly con- 

 firmed. * 



The other mineral, tellurium-lead, is, like the former, not crystallized, but 

 cleavable in three directions ; the planes of cleavage are not quite even, but 



♦ According to Berzelius, the atomic weight of silver is 1351.005. and that of tellurium 

 806.45, oxygen being 100. 



