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with characteristic fossils of that formation, and for the most part firmly cemented with a calcareous paste. Its average thickness here we have estimated at about fifty feet.

In Eastern Texas, Dr. F. Roemer encountered thick beds of loose sand and silex, which he refers to the Diluvial Period. These, he states, form a broad belt of "bad land," extending from north to south across a very considerable portion of the State.

This belt was crossed by the Expedition tinder your charge on the route from Indianola to San Antonio de Bexar, and was found extending in that direction from the Guadalupe River, in the vicinity of Victoria, W. N. W. to a point a few miles beyond Yorktown, occasionally interrupted, however, by several broad districts of fertile country. (Vide Journal) Over this district it consists chiefly of coarse silicious sand, with pebbles and small boulders of silex and other rocks disseminated through it, the whole reposing on the Cretaceous marls and clays.

Between San Antonio and the Guadalupe Mountains, deposits apparently of the same geological age are of frequent occurrence. At several points west of the Rio Pecos they present a thickness of more than a hundred feet, and are to be traced almost uninterruptedly from near the Horsehead Crossing of that stream to the Guadalupe Mountains, a distance of nearly a hundred and fifty miles.

Source.-As has already been remarked, these deposits become thicker and the materials coarser in proportion as we travel from east to west. There can, therefore, hardly be a doubt as to the direction whence they were derived. Indeed in several instances we have succeeded in tracing them for hundreds of miles to their original beds. Thus heavy accumulations of rolled fragments of white limestone and sandstone, agreeing precisely in lithological and paleontological characters with. the Upper Carboniferous limestone and sandstone of the Guadalupe Mountains, are found overlying the clays and sandstones of the Cretaceous System far to the east of that range, and no deposits of the same kind have been encountered west of it. (Vide Journal.)

Accumulations of rolled fragments of red porphyry and granite, presenting the same character as those of the Witchita Mountains, and which, as far as our own observations extend, are peculiar to that range, occur many miles to the eastward, but at no point west of these mountains have we succeeded in detecting any traces of them.

We have thus far spoken of the Boulder Formation only as it occurs east of the Rocky Mountains. We have, however, strong evidence of its existence much farther west. To the same geological period we would refer those extensive accumulations of loose materials which constitute the basins between the Guadalupe and Mimbres mountains. They consist chiefly of sands, clays, and coarse gravel, which have evidently been derived from the rocks, both stratified and unstratified, of the neighboring mountains. In