a fine sand, usually yellow or light brown, as if formed from the sandstone adjoining that river towards the north. These are generally arranged in hillocks, with intervening round hollows or basins, such as are cominon in drift districts. This sand, on the surface, is nixed more or less with mould, forming a light soil, but at a small depth is sufficiently pure for mortar. A tract of 2-3 square miles. covered with such drift, and remarkable for its hillocks and hollows, extends from the bluffs of the Mississippi to the valley of the Great Menominee, S. W. of Jamestown village, and similar accumulations are met with on the high lands, adjoining the Mississippi, between Potosi and Cassville. On the summits of the river bluffs, particularly in the vicinity of Cassville, small rolled fragments of the same materials as those composing the gravel drift, above noticed, are often profusely scattered. These facts indicate the passage of a peculiar drift current along the course of the Mississippi, and it is worthy of remark, that the points where those accumulations are most remarkable are a little below two large bends in that river, namely, that from south to southeast just above Cassville, and that to the south between Dubuque and Potosi. Such a deflection would naturally cause an eddy, and thus lead to those accumulations.

MINERAL DEPOSITS.

The first object of the present survey is the investigation of the Lead Mines of the mineral district, and of the different useful minerals connected with them. The previous description of the strata is important, as fixing definite limits in mining, and from their peculiar connexions with the mineral deposits.

The metallic ores found in the mineral district are chiefly the sulphurets of lead, zinc, iron and copper. Other ores of these metals are also found, formed apparently by recomposition from the decomposed sulphurets. Such are the sulphate and carbonate of had, the carbonate and silicate of zinc, the sulphate and hydrated oxyd of iron, and the carbonate of copper. The black oxyd of

manganese also frequently accompanies the mineral deposits. Of these ores, the sulphuret of lead (galena) is the most important, and that which has been hitherto the sole object of mining in the mineral district, except in one instance (that of the copper, at Mineral Point.) I shall therefore make it the first object of my attention, and notice the others only as far as they have an immediate connexion with it. The term mineral, in the mining district, is restricted to the ores of lead, and without addition to the sulphuret, and is the term generally used there for the latter. I shall for convenience use it in that sense, in what follows.

The first subject to be considered, is the manner in which the mineral is deposited. It is a matter of great interest to determine, whether the mineral is arranged in continued veins, or in detached and casual deposits. The prospects of mining must be much greater, if the former arrangement prevails, than if the latter. During the whole course of my examination of the mines, I have made this a particular object of attention, and although interruptions in the deposit of the mineral are general, as I believe is the case in all veins, yet the characters of a vein arrangement have appeared every-where to predominate.

The mineral deposits, whatever may be their character, are usually arranged along continued lines, having a certain direc tion, thus forming ranges or leads (lodes.) These ranges are mostly combined, in a certain systematic order, into different groups, called diggings, between which there is a greater or less extent of country in which little or no mineral has been discovered. These groups are also connected, in a corresponding order, in more extensive series, showing the general prevalence of systematic arrangement. As little has been done in deep mining, and the deepest shafts yet sunk have been abandoned, I have had fewer opportunities than I could wish, of tracing the mineral, at the same point, through different strata. Still in several instances I have followed it without interruption, or with only such minor interruptions as are common in veins, through different strata. The mineral deposits exhibit too, in the different strata, peculiar arrango

ments, which are common to each throughout the mineral district, subject only to local modifications; thus showing the prevalence of arrangement in a vertical as well as horizontal order.

The ranges or leads have different directions, which preserve a great degree of regularity in the different groups or even more extended series. Three different classes of ranges are recognized, according to their direction, namely, East and West, North and South, and quartering; the last intermediate between the two former. Of these, the East and West are the most important, and apparently have had a leading influence in the arrangement. The term East and West is not limited to such as are due east and west, or nearly so, but in different groups is applied to the predominant ranges having a general east and west bearing, although in some instances they may deviate even 45° from a due east and west course. The term North and South is also applied to ranges which deviate considerably from a due north and south course, but rarely to those which deviate] more than one sixteenth. Quartering ranges (called by the miners swithers and contras) include all such in a group as do not belong to either of the preceding divisions. They are such ranges as meet a leading range, particularly an East and West, at an oblique angle; consequently when the leading East and West ranges deviate from a due east and west course, a due East and West range would be considered quartering.

In general, the space in which the mineral is deposited, or through which it is distributed, if of much extent, is called an opening. This is sometimes filled with loose materials, and these by settling often leave a void between them and the roof, usually of no great extent; but in some instances larger cavities, or caves, have been so formed. In other instances, the opening is merely a certain extent of the rock, more for less modified, through which the mineral is distributed. Indeed, in nearly all those instances in which the openings are filled with loose materials, these appear obviously to have been derived from the decomposition of the rock, and not from materials deposited subsequently. Such open

1

ings differ from those in which the rock is only modified, by the greater degree of decomposition the rock has undergone. The rock immediately adjoining the openings is usually harder and more compact than the rock in general. That included in the openings is generally softer and more decomposed, and more or less stained with oxyd of iron. Different substances are also deposited in it, besides the mineral, such as other metallic ores, clay, calcareous spar and sulphate of barytes.* Openings, according to their direction and the manner in which the mineral is arranged in them, are vertical, flat (horizontal,) or pitching (oblique). The two first mark an important distinction in the arrangement in the different strata; the vertical openings predominating in the upper part of the upper magnesian; the flat openings in the middle and lower portions of the same, and in the blue limestone.

Although there are certain general principles which seem to have governed the arrangement of the mineral, yet numerous modifications occur, the details of which may be first given, before stating the former. In this detail, I shall commence with the arrangements observed in the upper part of the upper magnesian. The first and simplest form is that of the crevice. This may be either a joint in the rock, marked by an iron stain, or a fissure of little width, occupied by a seam of clay, or of ochre and iron rust (hematite); the two latter derived from the decomposition of iron pyrites, which sometimes, though rarely, is found in their place. Though the walls of the fissure are nearly parallel, yet it is usually marked by enlargements and contractions of little extent. In such a fissure, the mineral occurs as a sheet, either closely wedged in the rock, or separated from it by a thin seam of clay or iron. Such sheets usually conform on their surface to the adjoining sub

Silex, in the form of quartz or otherwise segregated, except as flint, rarely accompanies the mineral, or is disseminated in the opening rock. In one of the North and Souths, t Skidmore's Diggings, a fine-grained silicious grit accompanied the sheat of mineral, as a matrix, arranged in sheet form between it and the rock; and in a brown rock opening, on the west side of Coon Branch, near Benton village, crystalline quartz was found disseminated through the opening rock, in place of the calcareous spar usually disseminated.

stance, but occasionally present a more or less regular form, where the fissure is somewhat enlarged and the sheet is imbedded in clay. They are usually less interrupted than other forms of arrangement; in some instances, very little interrupted; in others, more so, when they are called broken sheets. When interrupted, they are replaced by clay or iron ore, and sometimes by calcareous spar, sulphate of barytes or zinc ore; but very rarely by the three latter in the upper part of the upper magnesian. Calcareous spar not unfrequently interrupts the vertical sheets in the lower part of that rock, and the mineral, when in contact with it, shows the same tendency to regular forms, as when imbedded in clay.* These sheets vary in thickness from a mere seam or film to a foot or more, and when even less than an inch in thickness, are generally profitable, from their little interruption, and when of great thickness, are, from the same circumstance, of extraordinary value. They may be either vertical, pitching or flat (horizontal;) but the flat sheets are rather parts of a more complex arrangement, while the vertical and pitching sheets may occur separately. These last are found with all the different bearings above specified; but the North and South sheets are the most common and the most important. Not unfrequently two or more sheets are connected; the rock between them being softer and more jointed, and forming properly an opening. In such instances, more clay and iron are usually present than where a single sheet only occurs. Such sheets often unite, in their course, in, a single sheet, which again divides, or are connected by cross sheets, usually in a quartering direction. In such instances, there is generally an enlargement at the junction of the sheets, where the mineral often assumes its more regular forms, and even loses its sheet character, and takes that more peculiar to the wider openings.

Vertical sheets have been sometimes worked to a great extent and with little interruption, vertically as well as horizontally, and

• The calcareous spar in such instances is sometimes distinctly crystallized,particularly in the form of dog-tooth spar.