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• 1. There is generally found a cap of iron ore on the benches as well as on the top of the hill, and of the same nature and the same thickness in both places. Yet where a clean section of the deposit underlying the top ore bed is seen, it is very rare that lower beds are found, and when they do occur they are thin, discontinuous, and of a physically different ore than the main bed. This would tend to show that the ore bed found on the benches belonged at the level of and had once been part of the main bed.
• 2. The greensand underlying the ore bed varies from thirty to forty feet thick, yet when there are several benches on the hill slope, and we measure the vertical thickness of the greensand from the upper ore bed to the base of the outcrop, it often appears almost a hundred feet thick. This can only be explained by supposing the edge of the hill to have slipped.

The alternation of hard and soft strata doubtless causes the formation of many benches, but this generally occurs in the country north of the Sabine, where almost all the benches are due to it. The soft strata over a harder one are worn away, until the eroding agencies come to the hard floor, which temporarily arrests the denudation, and hence arises a bench. The number of benches that can be explained as sea beaches, or river and lake terraces, is exceedingly doubtful, and the want of contour maps, as well as the concealed condition of all the strata, makes it still more difficult to determine the extent to which this cause has operated. No satisfactory work can be done in the matter until good maps are obtainable.

Though the beds underlying the whole of East Texas are characterized by their soft and a more or less incoherent nature, yet there are very often found spots in these strata that have become hardened by local chemical action. Such places, though limited in area, are very numerous, and supply a most valuable source of structural materials for local use. They are at present rarely used except for foundations, chimneys, and such purposes, but many of them are capable of being applied to much more extensive structures. These rocks may be divided into two classes:

• 1. Sandstones and Claystones.
• 2. Limestones.

The most important of the sandstones are a series of local and limited deposits formed by the action of ferruginous solutions on the original loose sands. This variety varies from a comparatively soft friable mass to a