The surface features are exceedingly varied, the prevailing elements being steppes or treeless plains in the north-west, mountains west of the Pecos river, forests in the east, marshes adjacent to the coast, low prairies in the south-east, and a combination of prairies and broken hills, interspersed with forest growth and thickets of tall shrubs (chaparral), in the centre. These regions are classified as follows (see map below). (1) The coast plain is the direct geographical and geological continuation of the other States which border on the Gulf of Mexico. It includes all the country east of a line concentric with the coast, drawn from Texarkana in the north-east corner of the State to near Laredo on the Rio Grande. The general direction of its slope, in common with that of the rest of the State, is from north-west to south-east. Its altitude ranges up to 500 feet. The immediate coast strip is newly made marshland; west of this and north of the Colorado river are forests; and to the south of it the country is mostly a plain. (2) The black prairie region succeeds the coast plain on the west. Its western border is sharply defined from the Red river to the Rio Grande, beginning at Denison, passing through or near the cities of Sherman, Dallas, Waco, Austin, and San Antonio, and then deflected westward to Eagle Pass. It is a gently undulating prairie, covered with a rich black soil, and varies in altitude from 300 to 700 feet. (3) The central region extends from the black prairie region on the east to the eastern escarpment of the great plains on the north-west and the trans-Pecos mountains on the south-west. This is the only region of Texas which is not the direct continuation of the physical features of some adjoining political division. A great variety of conditions is embraced within its bounds. In its north-eastern part are two long belts of stunted forest (the Cross Timbers), extending from the Red river to the Brazos, and separated by a prairie 50 miles in width. This is the most fertile portion of the entire region. West of this sub-region and north of the Colorado is a broken, arid country (the Coal-measures), having a sandy, pebbly soil, covered with a scattered growth of vegetation. West of this, between the 100th meridian and the escarpment of the plains, is the gypsum country, consisting of the so-called “red beds” of the western United States, accompanied by massive deposits of gypsum and other salts. This country is much sculptured by erosion, and in places resembles the “bad lands” of the upper Missouri country. There are also extensive intervals of prairie here. Near the centre, in the counties of San Saba, Mason, and Llano, is a rough, semi-mountainous area of older formations. The southern half of the central region is a broken country of white limestone formation, semi-tropical in climate, and covered with scraggy vegetation, its physical features graduating into those of northern Mexico. The south-western part is a rolling plain, entirely destitute of streams. Throughout the region, at intervals of many miles, low, truncated hills (buttes) occur, representing the remains of limestone formations now being rapidly, eroded. The region, as a whole, is poorly watered. It is best adapted for cattle and sheep raising, and is the chief locality of those industries in Texas. The altitude varies from 700 to 2500 feet. (4) The plains region is the portion of the State west of the 101st meridian and north of the thirty-second parallel, commonly known as the “Staked Plain” (Llano Estacado). It is the direct southern continuation and termination of the great plains of the North American continent which extend along the eastern slope of the Rocky Mountains from British America to tho Rio Pecos. The eastern edge is well marked by a steep escarpment, which, in consequence of destructive erosion, is constantly receding to the westward. The surface is smooth, and utterly devoid of forest growth or streams of water. But there are many small ponds or lakes, and in the southern part these are saline. The soil is light, rich, and porous, and is covered with a good growth of grass. Until a few years ago this region was totally unpeopled, but many portions of it are now (1887) used for grazing purposes, water being secured by means of wells or artificially constructed reservoirs. The altitude ranges from 2500 to 4000 feet. (5) The trans-Pecos or mountainous region west of the Pecos river is composed of numerous mountain peaks and ranges, with intervening valleys of many miles in width. It is poorly watered, and the population outside the immediate Rio Grande valley is very sparse. The general level of the country is from 3000 to 5000 feet.

The rivers are separable into several sub-systems. The Rio Grande and the Arkansas, constituting the north and south limits of the Texas drainage system, with their respective tributaries, the Pecos and the Canadian, originate in a limited district of northern New Mexico and Colorado, and ultimately reach the sea at points a thousand miles apart. The Canadian and the Pecos have cut deep canons through the Llano Estacado. The former continues eastward through Indian Territory, and the latter southward, joining the Rio Grande between 101° and 102° W. long, on the southern border of the State. The Rio Grande and the Pecos receive no tributaries of importance in Texas, but are constant in their flow. The next and most important group comprises the Red, the Brazos, and the Colorado, all of which originate along the eastern border of the Llano. They traverse similar regions, and have a general resemblance in character of sediment, irregularity of flow, velocity, and topography of drainage basins. Their brackish water is principally derived from the sudden precipitation of rainfall along the gypsiferous escarpments of the Llano. Its volume is ordinarily small, the flow often ceasing entirely west of the black prairie region. There are periodic freshets, however, which suddenly swell the volume to enormous proportions. These freshets, laden with the rich red loam of the plains, usually reach the lower inhabited sections of the State in periods of drought, and are termed “red rises.” Much of this sediment is deposited upon the flood plane of the lower valleys, and by this process the most valuable sugar and cotton lands of the coast plain have been built up. Another important group consists of the Sabine, the Trinity, the San Marcos, the Guadalupe, and the Nueces, most of which have their origin near the western border of the black prairie region. These streams have a greater volume and are more constant in flow than any others, and are usually without deep canons or wide bottoms. Many of them, especially those south of Austin, have their origin from large springs situated along the foot of the escarpment line extending from Austin southwestward. Another subsidiary system of streams originates in the narrow Quaternary region along the coast, within the district of the greatest rainfall. These streams are tidal, and sometimes navigable towards their mouths. Most of them are locally known as bayous. In general, the rivers of Texas are not adapted for irrigation or navigation. Neither do they afford much available water power north of Austin.

The entire geologic series, with a few exceptions, is represented in Texas. The earlier Palaeozoic rocks, including the pre-Cambrian (Keweenawian; A in accompanying geological map), the Potsdam (oc), and the Ordovician (oc), up to the Trenton, underlie the State, but are only exposed in two limited districts. The first of these is in the counties of Mason, Llano, Burnet, and San Saba in the central region; the other is in the disturbed mountainous portion of the trans-Pecos region. The Cambrian was deposited horizontally upon the upturned Keweenawian, and the Ordovician appears to rest conformably upon the Cambrian (Potsdam); but there λvas a continental elevation of the whole region, probably commencing at the close of the Trenton epoch, which continued until the beginning of the Coal-measure epoch, for the Upper Silurian, Devonian, and sub-Carboniferous are absent, and the earlier rocks are disturbed. These earlier Palaeozoic sediments present no marked stratigraphical or palaeontological differences from the same formations throughout the continent, and thus show the widely distributed uniformity of conditions which then existed. At the commencement of the Carboniferous period, however, that marked difference of faunal, lithological, and stratigraphical features began which distinguishes the synchronous deposits of the later formations of the western and eastern portions of the United States. The Texas region has been the transition ground, and hence all the geologic deposits, beginning with the Carboniferous, have two faces, dependent upon their geographical position east or west of 100° W. long., and representing the sediments either of interior continental basins or of the waters of the Atlantic during alternating periods of submergence and emergence. The Carboniferous rocks, and most of the succeeding formations, are exposed in two widely separated portions of the State, with entirely different lithological and faunal aspects. The mutual relations of these series have never been traced. The first occurs in the central region between 97° and 100° W. long., north of the Colorado river, and consists of clays, sandstones, conglomerates, limestones, and coal seams of workable thickness. It is the southwestern prolongation and termination of the Coal-measures of the eastern United States. These rocks, although in general similar to them, differ in some respects from those of the same formation further east, and also exhibit a few resemblances to the strictly marine Carboniferous of the Rocky Mountain region (κ 2 ), To the other series belongs the trans-Pecos Carboniferous (κ 1 ). Although this is of the same geologic age as the eastern Coal-measures, it is a purely marine deposit of limestones and sandstones, and is barren of vegetable remains. It is exposed along the Guadalupe and other mountains of the trans-Pecos region, forming the most eastern outcrops of the non-coal-bearing Carboniferous of the west. The study of the areal distribution and relation of the strata intervening between the Carboniferous and the fully-identified Cretaceous in Texas has not been begun. The Permian, Triassic, and Jurassic, if they exist, have not been clearly diagnosed, although these names have been applied to the series of rocks west of the central Carboniferous region. The thickness of the sediments belonging to these undetermined strata is very great. They are mostly un∙ fossiliferous, and the presence of stratified gypsum and other salts indicates that they were laid down in an interior basin cut off from oceanic waters and were too highly concentrated for the existence of molluscan life. Certain of these deposits, known as “red beds” or “Jura-Trias” (jt), extend beneath the Llano Estacado, across New Mexico, and into Arizona. The Cretaceous is by far the most conspicuous and extensive of the geologic formations of the State. It once covered the entire territory, but has been eroded away in many places west of the black prairie region, exposing the older formations, and is covered to the east of that region by more recent deposits. From the fact that the lowest member of the series is found resting directly upon the pre-Cambrian in Llano county, the Carboniferous in Lampasas and the counties northward, the Silurian in the trans-Pecos region, and the Jura-Trias beds in the plains region, it is evident that its beginning marked a period of continental submergence, and that this submergence, from the great thickness of pelagic sediments in it, was long continued. The lowest member of the series, the oldest known of the American Cretaceous, is unknown elsewhere in the United States, and its peculiar features give individuality to the central region. This member (cn), which may be called the Texas group, is the equivalent of the Neocomian of Europe, and many of its fossils are common to Europe and America. It is not exposed east of the central region, except (probably) in the salines of Louisiana. There was a great elevation of this deep-sea formation at its close, as is attested by the shallow water sediments of later groups deposited unconformably upon it. The Middle (cc, cs 1 ) and the Upper Cretaceous (cs 3 and cs 1 ) are also well exposed. The black prairie region is underlain by the middle and upper groups of the marine Cretaceous characteristic of the other Gulf States and known as the Rotten Limestone (cs 1 ) and Ripley (cs 1 ) groups. The Cretaceous groups of the Rocky Mountain region extend into Texas, and are exposed in the trans-Pecos region and along the lower Rio Grande. The Tertiary formations, so far as recognized, are purely marine, and, like the marine Upper Cretaceous of the black prairie region, are the direct geographical continuation of the formations of the other Gulf States. They occupy the coast plain, in bands approximately concentric with the shore of the Gulf of Mexico, and represent the sediments of its receding waters. The alleged occurrence of the fresh-water Miocene, the Loup river group (m), upon the Llano Estacado has not been demonstrated. Quaternary (q) and other recent alluvial deposits occur along the coast and the upper terraces of the three older river systems as far west as the eastern border of the central region. This is attested by the character of the deposits, accompanied by well-authenticated remains of the elephant and mastodon. These Quaternary soils are mostly the redeposited detritus of the strata of the eastern escarpment of the Llano Estacado, which is carried down by the “red rises.” The surface features of the central region are the result of sub-aerial denudation. The black prairie is protected from this destructive erosive process by the tenacious character of its soil; and the coast plain is covered by a luxuriant forest growth, and is constantly extending eastward by the recession of the shore line. The final emergence of the State began in Middle Cretaceous time, and was connected with the same movements that brought up the Rocky Mountain system. The strata of Texas, except the Palaeozoic groups, are soft, and yield readily to disintegration. A few eruptive sheets are found in the trans-Pecos region and along the lower Rio Grande, being remnants of the eastern edge of the great eruptive area of the Rocky Mountain region. Granitic masses occur, as extrusions from the preCambrian, in the central and trans-Pecos Palaeozoic deposits.

The eastern ranges of the Rocky Mountain system are deflected towards the Gulf of Mexico after passing south of 33° N. lat., and take a south-easterly course through Texas into Mexico, the trend of their axes being generally parallel to the direction of the Rio Grande and its principal tributaries. The only true mountains in Texas are situated west of the Pecos, with the exception of a few foot-hills (domitas) which re-enter the State from Mexico near Eagle Pass and follow the river to an undetermined point below Laredo. The principal ranges are the Guadalupe, Limpia, Chinali, Los Chisos, Organ, and Franklin Mountains. They are composed of older rocks, in most places; the later formations have been washed away, except where protected by eruptive flows. The most eastern and northern of these mountains are usually the highest. Guadalupe Peak is 9000 feet; Limpia Peak and the crest of the Chinalis, from 3500 to 8000 feet; Eagle Mountains, 7000; and the intervening valleys from 3500 to 5000 feet. The low buttes of the central region are miscalled mountains upon most maps. There are several well-defined escarpments extending for long distances, approximately north and south The step of the first of these, from Austin to Eagle Pass, is from 200 to 500 feet high, and is the result of an elevation at the close of the early Cretaceous period. Near the 100th meridian another escarpment occurs, and along the eastern and southern borders of the Staked Plain still another. The western part of the coast plain has a few low hills. The rest of the State has no notable prominences.

The mineral resources of Texas have not been mapped or studied, and hence the State ranks last in mineral products. The trans-Pecos region is rich in silver and lead ores; but the State owus the mineral rights of nearly all the land, and has hitherto declined to open them to development. Only one mine is worked here. Silver and gold have also been discovered and mined in Llano and Mason counties, but without successful results. Gold occurs throughout the marine limestones of the lowest (Texas) group of the Cretaceous, but not in sufficient quantity for profitable extraction. Rich but not abundant copper ores occur in the drift of the gypsum country. Iron ore is found in the Tertiary of eastern Texas, and is profitably reduced in a few charcoal furnaces by the aid of convict labour. At present these are remote from coal and suitable means of transportation. Magnetic iron ore occurs in the pre-Cambrian rocks of Mason county, and recent analyses show it to be equal in quality to the best Swedish ores. It is in great abundance, but remote from means, of transportation and fuel. Ores of iron (sphaero-siderite) occur in the central Carboniferous formation, but their commercial value is unknown. The non-metals occur in great abundance in different portions of the State, including salt, gypsum, magnesium sulphate, natural cements, kaolin, and other clays. The unutilized beds of massive gypsum are, with the exception of those of the Sahara and the Andes, the purest and most extensive in the world. Salt is gathered from lacustral deposits or mined at El Paso, Colorado City, and along the lower Gulf coast for local use. The coals of the central Carboniferous area have been worked to some extent, but are generally of inferior quality, having from 50 to 70 per cent, of ash. A ery recent discoveries of better quality have been reported. Tertiary fibrous lignite, of light specific gravity, is found in great abundance all along the junction of the coast plain and black prairie regions. It is worked to a small extent, but has no commercial value. The most important coal area is the semi-bituminous lignite belt of the trans-Pecos and lower Rio Grande regions, which is the direct geographical continuation of the late Cretaceous coals of New Mexico and Colorado. It is worked at Eagle Pass and Santa Toma, near Laredo. The beautiful marbles and other ornamental stones of the State are untouched, with the exception of the Llano county granite.

The amount and regularity of the rainfall decreases inland, the mean annual varying from 52’3 inches at Galveston to 13 at El Paso in the extreme west and 23 at Mobeetie in the extreme north. The subjoined table gives the mean temperature and rainfall of certain representative localities :— [table]

The coast plain and the black prairie regions have abundant rainfall for agricultural purposes. It decreases, however, to the west, and varies greatly in different years, sometimes being ample; but in 1885-86 it did not average 10 inches. The precipitation is also very sudden, seldom lasting more than a few minutes at a time. Only 52 per cent, of the 20 inches of rainfall in the central region and west of it falls in the agricultural season, one-half being in summer and the remainder in autumn, so that it is equivalent to only 15 inches in regions where the rainfall occurs in more propitious seasons. This condition is, however, especially favourable for grazing. There are few statistics of the plains region; but the rainfall along its eastern escarpment is slightly greater and more regular than that of the central region. The temperature varies greatly throughout the State, both in extremes and means. Fort Ringgold on the lower Rio Grande is the hottest point in the United States, except Key West, Fla. Its mean temperature is...