In the report on the lead and zinc deposits of the State, Winslow and Robertson* have recorded the facts bearing upon the occurrence of lead and, also have referred to the geological features.

Finally, Haworth has described the crystalline rocks of southeast Missouri, some of the most important observations having been made within the limits of the Mine la Motte sheet.

PHYSIOGRAPHY.

SURFACE RELIEF.

Main Characteristics. The Mine la Motte lies on the southern slope of the Ozark dome near the crest of the elevation. It is a semi-alpine region, with prominent, solitary peaks irregularly arranged, rather than arrayed in ranges and ridges. The extremes of altitude are about 540 and 1400 feet above tide-level. The general elevation is in the neighborhood of 1000 feet. Areas of equal altitude for every 200 feet are displayed on the accompanying diagram, figure 2.

In general two principal types of topography are represented. One is a very much broken or hilly region; the other is a broad plain with rather rough, rolling surface. The first of these comprises the porphyry peaks of the southwestern part of the district. (See plate iv). The elevations are in reality only the eastern members and outlying spurs of the St. Francois mountains, a group of more or less rugged hills which stretch away to the southwest in an interminable succession of peaks of nearly uniform height. There is no systematic arrangement discernible in these prominent surface features. Although indistinctly defined ridges may be sometimes made out, the rule is insolated mounds, large and small, rising irregu larly behind one another. The landscape presents numbers of the more important ones, all about of equal height, equally distant from one another and surrounded by smaller hills. As in other parts of the region, the granite or porphyry peaks stand out in marked contrast above the surrounding plain.

*Missouri Geol. Sur., VII, 646-676, 1895.

Missouri Geol. Sur., VIII, 81-224, 1835.