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soil may have been derived either from residual decay or transportation or more likely from both causes combined.

At Colorado City, on the Colorado river, there is a great development of sandstone and conglomeritic sandstone appearing both in the broken hills and bluffs and as a residual soil on the surface. A well bored to the depth of nine hundred feet at Colorado City passes chiefly through sandstone to a stratum of water which rises to within two hundred feet of the surface. A bed of rock salt encountered in the boring changes the water to a brine and this is pumped to the surface and used in the manufacture of salt.

Throughout much of the sandstone there is some salt, and in a creek bed four miles west of Colorado City the water is saline.

The dip of the Permian strata has been uniformly northwest but at a decreasing angle. So small is the angle of dip that it is almost impossible to tell in which direction the rock is tilted, and this difficulty is increased by the peculiar nature of the beds. many of which are so easily eroded that the exact outcrop edge is either very irregular or entirely covered. Near Colorado City the strata are so nearly horizontal that I have been unable to make any determination of the direction of dip.

The mesa country commences just west of Westbrooke in the valley of the Colorado. At this point a gentle undulating prairie is succeeded westward by a mesa with broad prairie-like top and with abrupt faces on the southwest side. Here the beds are chiefly red clay with bands of red shale and some thin limy layers. The lithologic appearance of this country is so much like the Permian farther east that one would not suspect that there was a possibility of its being of a different age. The occurrence of selenite crystals in the clay is worthy of note. The abundance of clay in these beds is quite noticeable in distinction to its absence in the upper beds of the Permian just passed over.

At Iatan, another more marked mesa facing eastward is encountered. A broken wall varying from fifty to one hundred and twentyfive feet in heighth extends in a general north and south course. The lower seventy-five feet of the mesa wall consists chiefly of red clay with occasional bands of red shale and sometimes bands of limestone. This is overlaid by twenty feet of white sandstone very much cross bedde, the layers in some instances dipping at diverse angles as high as ten or fifteen degrees. This sandstone is limy with occasional small pebbles. Above the sandstone on the top of the mesa is twenty feet of a remarkable quartzitic comglomerate very hard and flinty, quite compact, and breaking into angular pieces. It contains