128 



SILVER-LEAD DEPOSITS OF EUREKA, NEVADA. 



be observed that Nos. 9, 6, and 3 were finished first, showing that the draft 

 on that side of the muffle was the strongest. The assay which showed the 

 least loss was No. 7, which was in a position where the draft was the least 

 and the temperature the lowest and where the cupellation occupied nearly 

 the maximum time. The quantity of lead used with these assays was con- 

 siderably more than was necessary for a proper cupellation. It was used 

 in order to render the differences in loss as palpable as possible. 



Six assays of 5 grains silver with 25 grains lead gave the following 

 result : 



Back of muffle. 



FlG. 4. — Position of cupels in muti 



The order in which they were removed was 6-3-2-5-1-4; 5-1-4 being 

 finished at about the same moment, Here, also, the draft was greatest on 

 the right side of the muffle, and No. 4, which occupied the position of No. 7 

 in the former experiment, exhibited the least loss. The quantity of lead 

 was still too great for perfect cupellation. 



Two assays of 5 grains silver with 15 grains lead, cupelled side by side, 

 gave a loss of 3.5 and 3.8 thousandths of the unit of 5 grains. This loss 

 corresponds very nearly with that which Kerl" gives, and it is about as 

 small as it is possible to render it. 



Manner of removing buttons from cupels. As UiallV of tile silvd' bllttOllS obtained 



from the assays made of the Eureka rocks were so small that they could 

 scarcely be discovered by the naked eye, it was found next to impossible to 

 remove them from the cupel by raising them in pincers. Another method 



'• Bruuo Kerl, Hilttenkunde, IV., p. 35. Leipzig, 1865. 



