Many of the English, and nearly all the German ores, are, however, much poorer. Of five several experiments made by Vauquelin on ores from different mines in Germany, sixty-five per cent. of lead was the richest, and all were united with uncommon portions of carbonated lime and silex.
The button of metallic lead found at the bottom of the crucible in chemical assays, contains also the silver, and other metals, if any should be present in the ore. So also, in smelting in the large way, the metallic lead is always united with the other metals. When ores of lead contain any considerable portion of silver, they assume a fine steel grain; and the crystals, which are smaller than in common galena, oftener affect the octahedral, than the cubical figure. They are also harder to melt; and the lead obtained is not of so soft and malleable a nature as that procured from the broad-grained, easy-melting ore.
The proportion of silver in lead varies greatly. It is sometimes found to yield as high as twelve per cent., and is then called argentiferous lead-glance; but, in the poorest ores, it does not yield more than one ounce out of three hundred. To separate the silver from the lead, a process is pursued called the refining of lead, or cupellation. This is effected by exposing the lead to a moderate heat in a cupel, and removing the oxide as soon as it forms on the surface, until the whole is calcined, leaving the silver in the bottom of the cupel. The lead in this process is converted into litharge, the well-known substance of commerce; and the silver is afterwards refined by a second process, in which the last portions of lead are entirely got rid of. This process is known at the German refineries under the name of silber brennen, burning silver.
The rationale of cupellation is simply this. Lead on exposure to heat, with access of air, is covered by a thin pellicle or scum, called an oxide; and by removing this, another is formed; and so, by continuing to take off the oxide, the whole quantity of lead is converted into an oxide. It is called an oxide, because it is a combination of lead with oxygen (one of the principles of air and of water.) By this combination, an increase of weight takes place, so that a hundred pounds of bar-lead, converted into the state of an oxide, will weigh as much over a hundred, as the weight of the oxygen which it has attracted from the atmosphere. Silver, however, on being exposed to heat in the same situation, cannot be converted into an oxide; it has no attractive power for oxygen. Hence, when this metal is contained in a bar of lead, the lead only is oxygenated on exposure in a cupel; whilst the silver remains unaltered, but constantly concentrating and sinking, till the lead is all calcined. This is known, to a practised eye, by the increased splendor assumed by the metal.
I do not think the ore of Mine à Burton contains a sufficient quantity of silver to render the separation an object. This is to be inferred from its mineralogical character, from the mathematical figure and size of the crystal, its color, splendor, &c. The territory is not, however, it is believed, deficient in ores which are valuable for the silver they contain. The head of White river, the Arkansas, the Maramec, and Strawberry rivers, all afford ores of lead, the appearance of which leads us to conclude they may yield silver in considerable quantity.
SECTION V.
ANNUAL PRODUCT, AND NUMBER OF HANDS EMPLOYED.
On this head, it is very difficult to procure proper information. The desultory manner in which the mines have been wrought, and the imperfect method in which accounts have been kept, when kept at all, with other circumstances, which are in some measure incidental to the operations of mining in a new country, oppose so many obstacles in the way of obtaining the desired information, that I find it impossible to present a correct statement, from authentic sources, of the annual product of the mines for any series of years. When Louisiana was first occupied by the United States, Mine à Burton and Mine La Motte were the principal mines wrought; but the few Americans who had emigrated into the territory, under the Spanish government, were fully aware of the advantages to be derived from the smelting of lead, and, united to the emigrant population which shortly succeeded, made many new discoveries, and the business was prosecuted with increased vigor, and to a much greater extent. The interior parts of the country, and such as had before been deemed dangerous on account of the Indians, were now eagerly explored; and the fortunate discovery of several immense bodies of ore near the surface of the ground, whereby the discoverers enriched themselves by a few days' labor, had a tendency greatly to increase the fame of the mines, and the number of miners. But, as generally happens in new countries, among the number of emigrants were several desperate adventurers, and men of the most abandoned character. Hence, the mines soon became the scene of every disorder, depravity, and crime, and a common rendezvous for renegadoes of all parts. It is by such persons that many of the mines were discovered, and several of them wrought; and it is, therefore, no subject of surprise, that, on inquiry, no accounts of the quantity of lead made, and the number of hands employed, are to be found.
To secure the public interest, and remedy, in some degree, the irregularities practised at the mines, a law was passed in Congress, a few years after the cession of Louisiana, reserving all lead-mines, salt-springs, &c., which should be discovered on the public lands, subsequent to that period; and the Governor of the Territory was, at the same time, authorized to grant leases to discoverers for three years. The great defect of that law appears always to have been, that a specific agent was not at the same time authorized to be appointed for the general superintendence, inspection, and management of mines—an office which, from its nature, can never be properly incorporated with that of the territorial executive, and which, with every inclination, it is presumed his other avocations would prevent him from discharging either with usefulness to the public, or satisfaction to himself. But, whatever be the defect of the law, certainly the advantages which the government proposed to derive from it have not accrued. No revenue, it is understood, has yet been realized under it, and we are now as much at a loss how to arrive at a true statement of the mineral product of Missouri, as if the mines had never been a subject of governmental legislation.
When a discovery of lead has been made, the miners from the neighboring country have flocked to it, and commenced digging as usual, no one troubling himself about a lease; and thus the provisions of the act have been in a great measure disregarded. Men of respectability, and of sufficient capital to carry on mining in a systematic manner, have, it is believed, been frequently deterred from making applications for leases, from the short period for which only they can be granted. It would not warrant the expense of sinking shafts, erecting permanent furnaces, galleries, and other works necessary for prosecuting the business to advantage; for, no sooner would such works be erected, and the mines begin to be effectually wrought, than the expiration of the lease would throw them into the hands of some more successful applicant.