LEAD 



77 



remaining bead of silver appears to become agitated by a rapid motion, which seeing 

 to make it revolve with great rapidity. At this stage tile motion will be observed 

 suddenly to cease, and the button becomes immoveable. This is called the brightening 

 of the assay, and a button of silver now remains on- the cupel. 

 Jf the cupel were now abruptly removed from the muffle, the globule of silver 



Showing the Quantity of Lead Ore raised and smelted, average Metallic Yield of Ore 

 per Cent., and Ratio of Lead produced in various Parts of the United Kingd&m, 

 during Ten Years ending 1857. 



Table of Lead Ores, Lead, and Silver produced from them in the United Kingdom from 

 the year 1848, showing the Quantity of Ore required to make 100 Tons of Lead, the 

 Quantity of Lead in 100 Tons of Ore, and the Ounces of SUver in a Ton of Lead, 

 for the same period. 



