The lead-ashes are reckoned to yield fifteen per cent. of lead (zane and all), which, added to the first smelting, makes an average product of sixty-five per cent. This estimate will hold good uniformly, when the ores have been properly dressed, and the smelting well performed. Any spar adhering to the ore, renders it refractory; blende and pyrites have the same effect. The latter is particularly injurious, as it consists chiefly of sulphur; a substance known to render all ores refractory.
The slag created by the ash-furnace is a heavy, black, glassy substance, well melted, and still containing a portion of lead. Some attempts have been made to obtain a further portion of lead from it, by smelting with charcoal in a blast-furnace; but the undertaking has not been attended with complete success, and is not generally thought to warrant the expense. The per centage of lead recovered from the slag is not estimated at over ten, and, with the utmost success, cannot be reckoned to exceed twelve.
Some practical and miscellaneous observations may here be added. Metallic lead in the pig is now (Feb. 1819) worth $4 per cwt. at the mines. It sells for $4 50 on the banks of the Mississippi, at St. Genevieve and Herculaneum; for $5 50 in New Orleans; and is quoted at $6 in Philadelphia. This is lower than has ever been known before, (except at one period,) and a consequent depression in the mining business is felt. There is a governmental duty of one cent per pound on all bar and pig lead imported into the United States; but it does not amount to a prohibition of foreign lead from our markets. Perhaps such a prohibition might be deemed expedient. It is what the lead-smelters here call for; and certainly the resources of this country are very ample, not only for supplying the domestic consumption, but for exportation.
Those who dig the ore do not always smelt it. The merchants are generally the smelters, and either employ their own slaves in raising the ore, or pay a stipulated price per cwt. to those who choose to dig. For every hundred pounds of ore, properly cleaned, the digger receives two dollars. He works on his own account, and runs the risk of finding ore. It is estimated that an ordinary hand will raise a hundredweight per day, on an average of a year together. This, however, depends much upon luck; sometimes a vast body is fallen upon, with a few hours' labor; at others, many weeks are spent without finding any. He who perseveres will, however, generally succeed; and the labor bestowed upon the most unpromising mine, is never wholly lost. The above average has been made by those long conversant with the business, and upon a full consideration of all risks.