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in co-operation with your Survey, which brought with it a small remuneration for my services, which had previously been entirely voluntary.

The extent and character of the region to be surveyed, as set forth more fully in the accompanying paper, embraced an area of over 72,512 square miles, or over one-fourth (27.75 per cent) of the total area of the State-a region three times as large as the combined area of Massachusetts and Connecticutt, Rhode Island, New Jersey, and Delaware, or three times the size of West Virginia. Since it would have been a physical impossibility for the whole force employed upon your Survey to have covered this enormous area with even a reconnoissance, it became a matter of necessity that the region should be divided into working districts, and the work of my assistants limited to some certain portion.

In accordance with the necessity, the total area was subdivided, therefore, into the following artificial divisions for working convenience:

• 1. Northern District, or portion north of the Colorado, including 24,000 square miles.
• 2. Southern District, or portion south of the Colorado, including 48,000 square miles.
• 3. Isolated areas, including remnantal patches surrounding the buttes of Northwest Texas, or preserved in the mountain disturbances west of the Pecos, or exposed in the Tertiary areas of East Texas by denudation. Area not estimated.

The Northern District was chosen as the best adapted for preliminary operations, and the work has been confined to that field.

Unlike most districts of the State, this region has been thoroughly reconnoitered by previous investigations, and hence it was resolved to make what-so-ever work was undertaken of a complete and final character.

The absence of good geographic and topographic maps has been seriously felt, except in the small portion of the district covered by the United States work, but it has been impossible to devote time to the correction of these deficiencies, although some valuable data has been necessarily collected under this head.

Since all geologic products of economic value are derived from the rocks composing the strata, considerable work has been devoted to the ascertainment of the stratigraphic conditions of the region, part of which has been of the character of reconnoissance to ascertain and define the sequence of the rock sheets and a part to the making of carefully measured and delineated