Of the large number of counties in this great State of Texas, it is
universally conceded, not only by the citizens of the State, but also by all passing immigrants, that for richness of soil, congeniality of climate, charming and delightful scenery, a cultivated and hospital people, Dallas county can not be surpassed. Truly has it been said that she is the "banner county of the State."
    Situated in the center of the northern portion of the State, on what might be called a high rolling plateau, it is bounded on the north by the county of Denton, east by Collin and Kaufman, south by Ellis and west by Tarrant.

    The geological formation of the soil of Dallas county and of the strata beneath belongs in geology to that period classed as Mesozoic time and in the Cretaceous period, the lower division of this being uncrystaline or of aqueous origin. There is a stratum of white limestone rock beneath the deep, rich, loamy black soil, which appears universal through the entire county. Sometimes it crops out and extends for miles, scattering here and there, giving a mixed soil of black with small white and greyish lime rocks. Especially is this frequently seen in the western portion of the county.
    This soil is very superiorly adapted to the growing of small grains of almost every kind. Beneath this limestone is sometimes found beds of gravel, which is most conveniently utilized in improving roads and streets. These beds are found to be of remarkable variation of depth and dimensions, and must have been formed here when the waters covered the surface, having been drifted hither and thither by the surging waters. This gravel is lasting, as it consists chiefly of quartz, and of course is never ground into powder when used, while the white and grayish limestone found immediately beneath the soil crumbles on being exposed to the elements, and of course is not only worthless for paving roads and avenues but also for all building purposes of any kind.
    The very best of lime has been manufactured out of this stratum of limestone, and, owing to this formation, nearly all the springs and streams are of hard water. There are exceptions, of course, as in the case of deep wells sunk beneath the strata and where water is found in gravel or in a stratum beneath that of the limestone.

    There is what is commonly, and most appropriately termed the "black strip" of soil, about sixty miles in width, beginning at Red river, the dividing line between Texas and the Indian Territory, sweeping through Texas and extending almost to the Gulf of Mexico, and embraces the richest and most productive soil in the State. Dallas county is largely in this strip. While the surface consists in the greater measure of rolling prairie most delightful to the eye, especially when clothed in spring time with fresh green verdure, it is traversed by cross timbers that cluster on the banks of the Trinity river, which flows diagonally almost through its center, also on smaller streams and ravines. The soil is of that black, rich, loamy texture characteristic of the most productive known to geologists, and in some portions of the county it consists of that black, waxy character most charmingly adapted to almost every product known to the Southern climate.
    The rich, black soil sometimes extends to the depth of four and five feet, and is said to never diminish its strength in giving forth produce like that of the sandy or clay-like soil. On this the finest vegetation grows. When this county was unsettled the wild grass would grow to the height of an ordinary man. It was proverbial that the hunter would sometimes become lost in the grass and, straying off from his companions, entail upon himself the greatest difficulty to find his bearings. This grass was not entirely over the county, but only in some sections. A heavy mat of turf, however, was extended over the entire surface of the soil, especially on the prairies, and it was so strongly matted, and the black, sticky soil so compact that it was of the greatest difficulty to break it up so as to make it arable for farming purposes. It was, therefore, common to see the farmer in primeval days of the county with from six to eight yoke of oxen, or with from four to six mules, hitched to a large plow, breaking up his prairie lands, doing what was commonly called "sodding;" but as the county became more thickly populated and rains fell more frequently, thereby moistening the surface, this task of "sodding" became less irksome so much so that at the present period of development it is common to see the farmer seated on his sulky plow, with only two horses, plowing this wild land; in other words, sodding his new lands. This soil, once thought to produce nothing with any certainty but corn and cotton, has been found to contain those elements and ingredients productive of all kinds of small grains, and in fact almost every kind of vegetation known to the Southern climate.

    There is but a small quantity of timber, comparatively speaking, in the county, and that is found as stated, clustering on the streams, and, while not adapted for building purposes, it affords great comfort and convenience to the citizen for fuel in winter as well as protection to stock from the cold blasts of the northern winds, commonly called the "Texas Norther." This timber consists of oak, sycamore, pecan, hack berry, walnut, cottonwood, red and white elm, blackjack, box-elder, red haw, locust, hickory, wild china, cedar, gum-elastic, ash and "bois d'arc" (osage orange); and a peculiarity about it is, it does not grow to a great height. It is mostly stumpy, except immediately on the banks of the Trinity river. Here you find occasionally a large cottonwood, elm or hackberry. This timber has also an undergrowth called "underbrush," which makes it sometimes very difficult to pass through.
    At an early date, the farmers enclosed their farms with rails and brush, hauled for miles from these cross timbers, but as the population increased, and the timber became more scarce, and dear in price, bois-d'arc hedges were substituted, and afterward the barbed wire.

    At the present period of development, almost every farmer in the county has his enclosure fenced with barbed wire. The introduction of this wire was a great blessing to the people. In fact, it would have been almost impossible for the people in the county to have gotten along without it.
    Cotton, corn, wheat, and oats, raised per acre, in Dallas county, cannot be surpassed in any county in the State. Truly might it be said that the quantity per acre on some of the choice lands of this county, approximates that of the richest soil in the Mississippi valley. The cotton stalk is known to grow so high in placer, that a man can scarcely reach to the top, and the limbs so heavy with bolls that they sometimes break from the main stem. Corn and wheat are raised in great quantities. All vegetables are grown with ease. Sweet and Irish potatoes, sorghum, in fact almost all produce raised in a southern climate are produced on this soil. The largest, sweetest, finest quality of fruit, of almost every kind, such as peaches, apricots, apples, grapes, cherries pears, plums, etc., are produced.
    Watermelons are a marvel in size, in their season. The average yield of wheat per acre is from fifteen to thirty bushels; cotton from one-half bale to a bale, corn, from thirty to seventy bushels; oats, from thirty-five to eighty bushels; and hay, both native and cultivated, cannot be surpassed.
    The Johnson and Bermuda grasses, and millet, are raised in abundance. All of the above produce always brings the very highest prices in the markets of the country.

    Dallas county is one of the best-watered counties in the State. Besides the Trinity river, there is the Five-Mile creek, and the Ten-Mile creek, so denominated because of the distance from Dallas, the largest and central city in its borders.
    Almost all these smaller streams merge into the Trinity river. Beside these, there are many everflowing springs. The people are supplied with water by wells, in which any quantity can be secured by digging to only a shallow depth. Very frequently, at the depth of from fifteen to twenty feet, an abundance is secured. The wealthier citizens have flowing artesian wells, which are at present becoming quite common in this county. After boring down a few hundred feet, the artesian water, as clear as a crystal, will burst forth, sometimes as high as twenty feet above the surface. The water from the ordinary wells, springs and creeks is principally from magnesian limestone, and of course very healthful. That of the artesian wells is pure, a little warm, but delightful, after remaining exposed to the air a short while. Rain water in cisterns is used by many, and more especially in pools, called "tanks," which are denominated in the East as ponds. These tanks are commonly used by farmers for stock. They dam up a ravine or dig a place in some low spot on the prairie, so the water sometimes can bank up for the distance of a half mile. This is a very common means of securing water for cattle, and it was, indeed, more common with earlier settlers than now, when long droughts visited the county and lasted for several months. During the periods of droughts, the people would drive their cattle for miles, to a neighbor's tank. No such droughts now visit the county.

    Almost the entire time, during the summer season, a cool and delightful breeze is blowing: so the temperature in mid-summer ranges from about 75 to 90 degrees. The nights are generally very pleasant, as a cool and delightful gulf breeze prevails almost constantly. A sunstroke here is very uncommon.
    This county is superior in splendid facilities for traveling by private
conveyance, in addition to the numerous railroads. The county roads,
bridges, and all avenues, are in first-class order.

    The population of Dallas county in 1890 was 67,003, showing the largest of all counties in the State. It contains an area of 900 square miles, and an assessed valuation of its property, in. 1890, of $35,849,000. The lands are valued at from $10 to $50 per acre, the lands most valuable, near the city of Dallas, at from $100 to $200 per acre.

    As the preceding sketch is a mere preliminary bird's-eye view of the section of which we are writing, we now present a fuller view of the geological character of the district in which Dallas county is situated.
    A thorough geological survey of northern Texas has never yet been made, but we give the substance of the surveys that have been made and published in the First Annual Report of the Geological Survey of the State.
    Dallas county lies in the Cretaceous system, characterized by chalk formations. The two series of rocks comprising this system occupy the area known as the Black Prairie, the Grand Prairie and the two Cross Timbers, besides unstudied areas in the eastern and trans-Pecos regions of the State.
    To these strata the State owes a large part of her agricultural and
general prosperity, for they are the foundation of the rich, black waxy and other calcareous soils of this region, and in addition to their, agricultural features they are the most productive source of building material, while adjacent to the parting between them, extending the entire length of the State and depending upon their stratigraphy, is a remarkable area of natural and artesian wells. That these formations are of great economic value is also shown by the fact that they are the site of our principal cities and the rich agricultural soils which surround them.
    This is in general a chalky country, and uniquely Texan, so far as the United States are concerned, constituting a distinct geographic region in every topographic, economic and cultural aspect, and one which should not be confused with other portions of the country. It covers an area of over 73,512 square miles, or over one-fourth (28.27 per cent.) the total area of Texas, forming a broad belt of fertile territory across the heart of the State, from the Ouachita mountains of the Indian Territory and Arkansas to the mountains of northern Mexico, an area larger than the average American State, and equal to the combined area of all the New England States.
One-third of this region lies north of the Colorado river, and the remainder to the southwest.
    This region, with its many different prairies, each covered by its
peculiar vegetation, its sweeping plains and diverse valleys, its undulating slopes clad with liveoak, its narrow strips of cross timbers, its ragged buttes and mesas, presents a landscape varied, yet possessing as a whole an individuality peculiarly its own. All of these features, with their different tints and tones of soil and vegetation, with their varied conditions for human habitation, are but the surface aspects of the system of chalky rocks (chalky sands, chalky clays and chalky limestones) upon which it is founded, and to which is primarily due every physical quality of the country. In fact it is the great chalky region of the United States.
    The rocks originated as sediments of the Atlantic ocean, laid down with great uniformity during two of the long epochs of subsidence and emergence when the waters covered this region many hundred fathoms deep. These ancient sediments are now more or less consolidated and elevated into a fertile land, which is decomposing under atmospheric conditions into soils and debris, and in turn being slowly transported to the ocean, where it will make other rock sheets. They now occur in regular sheets or strata, dipping beneath each other toward the sea, while the projecting western edges, each of which weathers into and imparts its individuality to its own peculiar belt of country, outcrops in long, narrow belts, sub-parallel to the present ocean outline. Thus it is that as one proceeds inland from the coast. He constantly crosses successively lower and lower sheets of these formations.
    The oldest, or lowest, in a geological sense, of these outcrops, forms the Upper Cross Timbers, those above these make the Grand Prairie, the next sheet forms the Lower Cross Timbers, and the next the Black Prairie, etc.
    Each of these weathers into a characteristic soil, which in its turn is adapted to a peculiar agriculture. Each, too, has its own water conditions and other features of economic value. Some of there rock sheets, like the Upper Cross Timber country, may be comparatively infertile in the region of outcrop, yet they may serve to carry the rain which falls upon the thirsty sands far beneath the adjacent country, where by artesian borings it becomes an invaluable source of water supply for a distant and more fertile region.
    The Cretaceous country of Texas, as a whole, like the system of rocks of which the surface is composed, is reparable into two great divisions, each of which in turn is subdivided still further. These two regions are known as the Black Prairie and Grand (or Fort Worth) Prairie regions, each of which includes in its western border, north of the Brazos, an elongated strip of timber known as the Lower and Upper Cross Timbers, respectively.

occupies an elongated area extending the length of the State from Red river to the Rio Grande. The eastern border of the Black Prairie is approximately the southwestern termination of the great Atlantic timber belt. The Missouri Pacific and the International railroads from Denison to San Antonio approximately mark the western edge. A little south of the center, along the Colorado river, from Austin eastward to the Travis county line near Webberville, the Black Prairie is restricted to its narrowest limits. Westward this prairie is succeeded by a region of some superficial resemblance to it which on closer study is found to differ in all essential points. This is the Grand, or Fort Worth, Prairie, or chard-lime-rock region."
    The so-called mountains west of Austin are the remains of the Grand Prairie. In general, the Black Prairie region consists of a level plain, imperceptibly sloping to the southeast, varied only by gentle undulations and deep drainage valleys, unmarked by precipitate canons. It is transected at intervals by the larger streams, whose deep-cut valleys, together with their side streams, make indentations into the plain, but not sufficiently to destroy the characteristic flatness of its wide divides-remnants of the original plain, or topographic marine base level, which has not been completely scored by its still youthful drainage system. The altitude of the plain is between 600 and 800 feet. The surface of most of the Black Prairie region is a deep black clay soil, which when wet becomes excessively tenacious, from which fact it is locally called "black waxy." In general it is the residuum of the underlying clays, and contains an excess of lime, which, acting upon the vegetation by complicated chemical changes, causes the black color. It is exceedingly productive, and nearly every foot of its area is susceptible of a high state of cultivation, constituting one of the largest continuous agricultural regions in the United States. Large crops of cotton, corn, etc., are annually raised upon its fertile lands; and if there were facilities for proper transportation it would soon be one of the leading districts of our country.
     The Black Prairie is subdivided longitudinally into four parallel strips of country, differing slightly, and distinguishable only by slight differences in topography and in the underlying rocks. In the easternmost of these divisions north of the Brazos and Colorado rivers, however, the sand is hardly perceptible. Immediately interior of this is located the largest and, most characteristic area which is marked by the stiffest of the black waxy calcareous clay soils. Upon digging through this stratum, the subtecture is found to consist of a light blue or yellow calcareous clay, called by the residents "soapstone" and Joint clay," from its jointed and laminated structure. The surface, especially of t he high undrained divides, is also accompanied in many places by minute depressions known as I "hog-wallows," which are produced by the drying, cracking and disintegrating character of these excessively calcareous clays in poorly drained places.
    This, the main portion of the Black Prairie, constitutes fully two-thirds of its total area. The cities of Greenville, Terrell, Corsicana and Kaufman are situated near the border of the sandy and black waxy strips. Manor, Clarksville, Cooper, Taylor and Temple are all situated in the main black waxy belt.
    An outcrop of the "white rock" or chalky country, forming a narrow strip averaging two miles in width, from Red river to the Rio Grande, succeeds on the west the main black waxy Strip. Thia chalk region is marked by a topography more rounded and deeper incised, but still void of the sharper lines of stratification that characterize the Grand Prairie region. It is usually treeless, but occasionally marked by clumps of handsome evergreens and oaks. The western edge of this chalky region, as seen at Oak Cliff, near Dallas, at Sherman, Hillsboro and other places, usually ends in an escarpment overlooking a valley containing the minor Black Prairie and Lower Cross Timber strips. It is upon this chalk that the most prosperous of the interior cities of Texas are located, including Paris, Sherman, McKinney, Dallas, Waxahachie, Waco, Austin, New Braunfels and San Antonio, all of
which are dependent upon the agricultural products of the adjacent prairies.
    West of the "white rock" or chalky division, and generally at a slightly lower altitude, occupying a valley across the State, is a second narrow strip of black clayey land of a nature similar to that of the main black waxy area, and likewise accompanied by hog-wallows. This is the country east of Denton and Whitesboro, in the Mountain creek district of Dallas county, and along the line of the Missouri Pacific railway from Alvarado to Waco.
    The Lower Cross Timbers (a narrow belt of forest country extending from the Red to the Brazos rivers) represent the westernmost strip of the Black Prairie region, and belong to it geographically, as will presently be shown.
    Let us now consider the substructure of the Black Prairie region in five divisions, commencing with the lowest, namely, the Upper Arenaceous, or Glauconitic; the main Black Prairie, the surface of the marine clays, called the Ponderosa marls, the white-rock division, which is the outcrop of the Austin Dallas chalk, aggregating about 600 feet in thickness; the minor Black Prairie, also composed of clays like those of the main division, and consequently having a similar topography; and the Lower Cross Timbers. All the foregoing rock sheets, between which there is no Stratigraphic break, represent the sediment deposited in the oceanic waters during a long continued subsidence, geologically known as the Upper Cretaceous period, for which collectively we have chosen the name of Black Prairie Series. This Upper Cretaceous series has five conspicuous Stratigraphic and lithologic divisions, which approximately correspond with the topographic divisions of the Black Prairie above mentioned.

1. - THE LOWER CROSS TIMBER BANDS.
    From the Brazos river northward to Red river the base of the upper series is composed of a brown, more or less ferruginous, predominantly sandy littoral deposit, resting unconformably upon various horizons of the semi-chalky beds of the Washita division, or top of the Comanche series. These sandy deposits present an infinite variety of conditions of cross-bedding, clay intercalations, lignitic patches, and variation in fineness of size and angularity of the uncemented particles, characteristic of typical littoral deposits, while occasionally there are found fossiliferous horizons.
    In the vicinity of Denison these sands are covered by a post-Tertiary sand, which confuses their identity there.
    The Lower Cross Timber region abounds in rich sandy roils, which support a vigorous timber growth, this Structure being especially for deep-rooted plants, and are specially adapted to fruit-growing, as seen near Denison and Paris. There is also considerable lignite and iron in the beds of this region.
    The lignite is frequently discovered and mistaken for bituminous coal. It is doubtful whether either exists in sufficient quantities for commercial use. The Cross Timbers are also in the line of the Central Texas artesian belt, and it is probable that in any portion of its area an artesian well sunk through the rock of the underlying Comanche series would find an abundant flow of water. These .sands are also valuable for water-bearing purposes, and the wells along the margin of the minor Black Prairie area are supplied from them.

2. - THE EAGLE FORD CLAY SHALES.
    These lie to the eastward and immediately above the Lower Cross Timber sands, and are the foundation of the minor Black Prairie streak.
    Beneath the scarp of the white rock (Austin-Dallas chalk) at Dallas, and extending westward through the Mountain creek country to the Lower Cross Timbers, can be seen typical localities of this division, the thickness of which is estimated at 400 feet. These clays in their medial portion are dark blue and scaly, highly laminated, and occasionally accompanied by gigantic nodular septariae, locally called "turtles." The uppermost beds gradually become more calcareous, graduating rather sharply into the chalk. There are also occasional bands of thin, impure limestones, which are readily distinguishable from all other Upper Cretaceous limestone by their firmness and lamination. Fossil remains of marine animals are also found in these
clays, including many beautifully preserved species, the delicate color and nacre of shells being as fresh as when the animals inhabited them. Among these, oysters, fish teeth, chambered shells and Inocerami are the most abundant.
    The chief economic value of the minor Black Prairie will ever be its
magnificent black calcareous soil, while some of the chief geological
considerations are the ascertainment of means to make this soil more easily handled and less tenacious by devising suitable mixtures, the discovery of road-making material, and the increase of water for domestic and agricultural purposes. Owing to its clay foundation the soil now retains for plant use treble the quantity of moisture of some of its adjacent sandy districts, but surface and flowing water is scarce. Fortunately, however, this district is also within the Central Texas artesian well area, and an abundant supply of water can always be had at a depth of less than 1,500 feet, as has been proved in the course of our investigations. When this fact is fully appreciated the region will be one of the most prosperous in Texas.
    In the valleys of most of the streams running eastward across the east half of the minor Black Prairie, artesian water can be obtained at from 100 to 300 feet. The source of this water is in the Lower Cross Timber sand. Many of the concretions and calcareous layers are probably Suitable for making cement; but tests must be made. The clays may also prove of commercial value.

3. - THE WHITE ROOK, OR AUSTIN-DALLAS CHALK.
    Immediately above and to the east of the Eagle Ford clays comes the white rock, or Austin-Dallas chalk, which is the most conspicuous representative division of the whole Upper Cretaceous system. This occupies the narrow strip, as noted in the preceding topographic description, marking the western border of the main Black Prairie region, separating it from the minor Black Prairie. The outcrop of this chalk begins in the southwest corner of the State of Arkansas and in the Indian, Territory. It crosses Red river, the exposure continuing westward up to the south. side of the valley of that stream to the north of Sherman, from which place it deflects southward, passing near McKinney, Dallas, Waxahachie, Hillsboro, Waco, Belton, Austin, New Braunfels, San Antonio and Spofford Junction, beyond which it bends northward, appearing in the disturbed mountains in the vicinity of El Paso and New Mexico. It is distinguished. above all by its
peculiar chalky substructure.
    The words "limestone" and "chalk" are used on these pages as follows:
    Limestone is employed generically for species of widely different origin and structure, namely, of five kinds: 1. Breccias composed of more or less comminuted and cemented shells of ancient bottoms or shores. 2. Concretions or segregations formed by the segregation of lime in clays and sands after original deposition, rare in our rocks. 3. Chalks are composed of amorphous calcium carbonate, usually more or less foraminiferous, void of laminations, and of comparative deep-sea origin. These may be hardened by metamorphism into firm limestones. Hence the term "chalky limestones" will imply chalky origin. 4. Laminated, impure limestones, occurring as alternating beds in sands and clays, indicative of shallower origin then chalk. 5. Metamorphosed limestones, or any of the above which have undergone induration or secondary change. All laminated limestones thus far found in the Texas Cretaceous are in the basal beds, and are more or less arenaceons or argillaceous, further proving their origin to have been in shallower water than those in which chalk is laid down.
    The rock of the Austin-Dallas chalk formation is a massive, nearly pure, white chalk, usually free from grit and easily carved with a pocket-knife. Under the microscope it exhibits a few calcite crystals, particles of amorphous calcite, and innumerable shells of foraminiferae. The air-dried indurated surfaces are white, bat the saturated subterranean mass has a bluish white color. The rock weathers in large conchoidal flakes, with an earthy fracture.
    In composition it varies from 85 to 94 per cent. of calcium carbonate, the residue consisting of magnegia, silica and a small percentage of ferric oxide.
    The thickness of this chalk is about 500 feet. So far as observed in
Texas it averages the same thickness at Austin, Sherman and Dallas. It is of great uniformity throughout its extent; but there are a few local differences in hardness, which are sometimes due to surface induration and to igneous action, having been converted into marble in some places.
    A great portion of the former extent of this chalk has been destroyed by erosion, and its western border in Central Texas is now receding eastward under the influence of excessive atmospheric decomposition and denudation.
    The group may have extended at one time all the way to the Rio Grande. This formation abounds in fossils, most of which, however, are but poorly preserved casts.
    The economic advantages of the white rock are various. It affords good locations for the building of cities and communities, not only on account of the firm foundation for building and road-beds and good drainage which it always affords, but also on account of its sanitary conditions, produced by the irnbibing capacity of the chalk. When accurate statistics are kept, it will be proved that dwellers upon the chalky lands have a great hygienic advantage over those upon sands and clays. The chalks are also water-bearing, and while yielding their moisture slowly they afford an abundance for domestic purposes, and play an important part in the transmission of the rainfall to depths from which it can be abstracted, perhaps, in east Texas, by artesian wells. This chalk is also valuable for the manufacture of whiting, rouge, etc. Chalk is most used in England,
however, where scientific agriculture has attained its highest development for dressing lands. Thousands of tons are used annually on the non-ealcareous lands of England, where it is usually applied at the rate of twenty tons per acre, just as it will ultimately be used upon the non-caleareous lands of east Texas as Boon as our agriculture advances to a stage where its necessity will be appreciated.
    Chalk makes a cheap, convenient land dressing for non-chalky lands, performing in a more satisfactory manner the functions of quick-lime in making available other constituents of the Boil, besides contributing to it minute but valuable proportions of phosphates, potash and other plant foods.
    The chalk will also prove of great use in the manufacture of Portland cements. It is the material used in the manufacture of most of the imported cements; and when the people of this State properly appreciate what an immense industry lies at their doors-a natural, Texas monopoly-this region will become a great cement center for the United States.

4. - THE EXOGYRA PONDEROBA MARLS.
    The name given to these marls is that of a large fossil oyster, which occurs in immense quantities in certain beds.
    The eastward continuation of the Austin Dallas chalk is covered by what is the most extensive and valuable, but least appreciated, geological formation in the United States, namely, a remarkable deposit of chalky clays, aggregating some 1,200 feet in thickness, according to reported well-borings and estimates of the normal dip. In fact these clays are so little known that no popular name has yet been accorded them; and hence they are called after the immense fossil oyster found in them.
    These clays occupy the whole of the main Black prairie region east of the Austin-Dallas chalk, and form the basis of the rich, black, waxy soil. Notwithstanding their horizontal extent, good outcrops of the unaltered structure are seldom seen, owing to their rapid disintegration. Usually they are seen only in ravines, creeks, or fresh diggings. They are of a fine consistency, unconsolidated and apparently unlaminated until exposed to the weather, when their laminated character is developed. They are light blue before atmospheric exposure, but rapidly change into a dull yellow, owing to the oxidation of the pyrites of iron in them. Their chief accessory
constituent is lime in a chalky condition, and they are more calcareous at the bottom than at the top. Near the top of these and other exposures there is to be seen a rapid transition into the black, calcareous, clay soil, characteristic of chalk and chalky clays whenever their excess of lime comes in contact with vegetation. They are more calcareous and fossiliferous at their base.
    The economic value of these chalky clay marls is in the fact that they are the foundation and source of the rich soil of the main black, waxy prairie, the largest continuous area of residual agricultural soil in the United States, apparently inexhaustible in fertility; for as the farmer plows deeper and deeper he constantly turns to light the fertile marls which renew the vitality of the surface. These soils can be much improved by further geologic study.

5. - THE UPPER ARENACEOUS OP. GLAUCONITIO DIVISION.
    This is the continuation of the Ponderosa marls, exhibiting itself chiefly in northeastern Texas and southwest Arkansas.
    Dallas county also borders upon the Grand prairie or Fort Worth section, the features of which are reported at length by the State Geologist, so far as studied; but as it comes outside of our district, we omit it here.