Custom has established a number of laws among the miners, with regard to digging, which have a tendency to prevent disputes. Whenever a discovery is made, the person making it is entitled to claim the ground for twenty-five feet in every direction from his pit, giving him fifty feet square. Other diggers are each entitled to twelve feet square, which is just enough to sink a pit, and afford room for throwing out the earth. Each one measures and stakes off his ground, and, though he should not begin to work for several days afterwards, no person will intrude upon it. On this spot he digs down, but is not allowed to run drifts horizontally, so as to break into or undermine the pits of others. If appearances are unpromising, or he strikes the rock, and chooses to abandon his pit, he can go on any unoccupied ground, and, observing the same precautions, begin anew. In such a case, the abandoned pit may be occupied by any other person; and sometimes large bodies of ore are found by the second occupant, by a little work, which would have richly rewarded the labors of the first, had he persevered.
In digging down from fifteen to twenty feet, the rock is generally struck; and as the signs of ore frequently give out on coming to the rock, many of the pits are carried no further. This rock is invariably limestone, though there are many varieties of it, the texture varying from very hard and compact, to soft and friable. The former is considered by the diggers as a flinty stone; the latter is called rotten limestone; and, from its crumbling between the fingers, and falling into grains, there is a variety of it called sandstone. It is all, however, a calcareous carbonate, will burn into quicklime, and, as I find on experiment, is completely soluble in nitric acid. As no remains or impressions of shells, animalculæ, or other traces of animal life, are to be found in it, I conclude it to be what geologists term metalliferous limestone; a conclusion which is strengthened by its semi-crystalline fracture. It exhibits regular stratification, being always found in horizontal masses. How far this formation extends, it would be difficult to determine; but, so far as my observation goes, it is invariably the basis on which the mineral soil at Mine à Burton, and the numerous mines in its vicinity, reposes. It is overlaid by secondary limestone in various places on the banks of the Mississippi, between Cape Girardeau and St. Louis. It is also seen passing into a variety of secondary marble, in several localities. I have seen no specimens of this mineral, however, which can be considered as a valuable material in sculpture.