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direction. Those of quartz are apparently much more abundant in the porphyry than in the granite. Near Cache Creek several of them are seen traversing the mountains from top to bottom. The quartz in that situation is highly ferruginous, often exhibiting distinct crystals of bisulphuret of iron, and contains small irregular cavities partially filled with liquid naptha. In Otter Creek, a small affluent of Red River, having its sources in these mountains, two specimens of bluish yellow quartz, each containing a small particle of gold, were found. Black ferruginous sand has also been discovered in great abundance in several of the streams flowing from these mountains.

Igneous Protrusion near Fort Washita.-This protrusion has been traced in a northeasterly and southwesterly direction for the distance of about thirty miles, with an average width of about six miles. It consists altogether of coarse porphyritic granite and quartzose rock. The granite is mostly hard, of a reddish color, and contains distinct crystals of feldspar of the flesh colored variety. It is traversed by the quartz in thick veins, which are in some localities quite numerous. This rock is mostly white and very compact. In a few places it is highly discolored with oxide of iron.

MOUNTAIN RANGES.

Eight different ranges of mountains have been examined by myself in Texas and New Mexico. Of these four are composed entirely of eruptive rocks, one partly of eruptive and partly of sedimentary rocks, and three altogether of sedimentary rocks. Those composed entirely of eruptive rocks are the Witchita, Limpea, Hueco, and Membres Mountains. The Organ Mountains consist partly of sedimentary and partly of eruptive rocks, while those altogether sedimentary in their composition are the Guadalupe, the Sacramento, and the Horse Mountains, the last including the Fra Cristoval and Robledo Mountains, both of which are but detached portions of the same range. Although differing remarkably in their general composition, these different ranges possess certain features in common which at once serve to distinguish them from any of the mountains occurring east of the Plains. With the exception of the Witchita range they all have a general north and south bearing, and the parallelism of the lines of eruption or of upheaval are usually exceedingly well marked, the different chains being sometimes traced continuously for hundreds of miles, with the same general curves, and with broad, smooth intervening valleys, open only at their northern and southern extremities. Owing to the great thickness of the quaternary deposits of western Texas and New Mexico, the minor inequalities of the surface of the country are generally obliterated, so that the mountains are usually seen rising abruptly from smooth level or gently ascending plains, while for the same reason many of the igneous protrusions of these regions appear completely isolated that would otherwise be exhibited in continuous chains, their lower portions being covered by these deposits.