"The color-effects are rich and wonderful. They are due to the inherent colors of the rocks, modified by the atmosphere. Like any other great series of strata in the Plateau Province, the carboniferous has its own range of characteristic colors, which might serve to distinguish it even if we had no other criterion. The summit strata are pale-gray, with a faint yellowish cast. Beneath them the cross-bedded sandstone appears, showing a mottled surface of pale-pinkish hue. Underneath this member are nearly 1,000 feet of the Lower Aubrey sandstones, displaying an intensely brilliant red, which is somewhat masked by the talus shot down from the gray, cherty limestones at the summit. Beneath the Lower Aubrey is the face of the Red Wall limestone, from 2,000 to 3,000 feet high. It has a strong red tone, but a very peculiar one. Most of the red strata of the west have the brownish or vermilion tones, but these are rather purplish-red, as if the pigment had been treated to a dash of blue. It is not quite certain that this may not arise in part from the intervention of the blue haze, and probably it is rendered more conspicuous by this cause; but, on the whole, the purplish cast seems to be inherent. This is the dominant color-mass of the cañon, for the expanse of rock surface displayed is more than half in the Red Wall group. It is less brilliant than the fiery-red of the Aubrey sandstones, but is still quite strong and rich. Beneath are the deep-browns of the lower carboniferous. "The dark iron-black of the horn-blendic schists revealed in the lower gorge makes but little impression upon the boundless expanse of bright colors above." [Illustration: OIL WELL. CHICAGO: A. W. MUMFORD, PUBLISHER.] OIL WELLS. Oil is found in Pennsylvania in oil-bearing sand-rocks, which are considered as the reservoirs in which the distilled product has found a permanent lodgment. The depth of the oil-sand or sand-rock in this state is from 800 to 1,900 feet. There are often several strata, one above the other, containing oil. It is the uniform experience that the lightest oils are found in the lowest sandstones, while the heaviest oils are drawn from the shallowest wells; and as we approach the surface where it is gathered from the pools dug to the depth of only a few feet, it becomes sticky, semi-fluid, and finally a solid asphalt. Man made no attempt to bore a deep hole through soil and rock, hundreds of feet down, to reach oil, until the summer of 1859. The first oil company was formed in 1854, with Mr. George H. Bissell at its head, which bored the first oil well in the summer of 1859 under the direction of E. L. Drake. It was about the middle of June that "Uncle Billy Smith" and his two sons arrived in Titusville, on Oil Creek, Pa., the scene of operations.