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observed nowhere in Iowa except along the bluffs of the Big Sioux river, in Woodbury and Plymouth counties. They are composed of calcareous matcrial, but are not a true, compact limestone. The material of the upper portion is used for lime, the quality of which is equal to that of common limeetone. No good building material is obtained from these beds. Some fossil fish have been found in them.

Above all the formations above-mentioned rests the Post-Tertiary, or Drift deposit, which is more fully mentioned in connection with the Soils of Iowa.

ECONOMIO GEOLOGY.

Coal-Peat-Building Stone--Lime-Lead-Gypsum-Spring and Well Water-Clays

Mineral Paint.

COAL.

Every year is adding to our knowledge of, and attesting the importance and value of our vast coal deposits. In some unknown age of the past, long before the history of our race began, Nature by some wise process, made a bountiful provision for the time when, in the order of things, it should become necessary for civilized man to take possession of these broad rich prairies. As an equivalent for the lack of trees, she quietly stored away beneath the soil those wonderful carboniferous treasures for the use and comfort of man at the proper time. . The increased demand for coal has in many portions of the State led to improved methods of mining, so that in many counties the business is becoming a lucrative and important one, especially where railroads furnish the means of transportation. The coal field of the State embraces an area of at least 20,000 square iniles, and coal is successfully mined in about thirty counties, embracing a territory larger than the State of Massachusetts. Among the most important coal producing counties may be mentioned Appanoose, Boone, Davis, Jefferson, Mahaska, Marion, Dionroe, Polk, Van Buren, Wapello, and Webster. Within the last few years many discoveries of new deposits have been made, and counties not previonsly numbered among the coal counties of the State are now yielding rich returns to the miner. Among these may be mentioned the counties of Boone, Dallas, Hamilton, Hardin, and Webster. A vein of coal of excellent quality, seven feet in thickness, has been opened, and is now being successfully worked, about five iniles southeast of Fort Dodge, in Webster county. Large quantities of coal are shipped from that point to Dubuque and the towns along the line of the Dubuque and Sioux City Railroad. A few years ago it was barely known that some coal existed in Boone county, as indicated by exposures along the Des Moines river, and it is only within the last few years that the coal mines of Moingona have furnished the vast supplies shipped along the Chicago and Northwestern Rail. road, both east and west. The great productive coal field of Iowa is embraced chiefly within the valley of the Des Moines river and its tributaries, extending up the valley from Lee county nearly to the north line of Webster wunty. Within the coal_field embraced by this valley deep mining is nowhere necessary.

The Des Moines and its larger tributaries have generally cut their channels down through the coal ineasure strata.

The coal of Iowa is of the class known as bituminous, and is equal in qnality and value to coal of the •same class in other parts of the world. The veins which have so far been worked are from three to eight feet in thickness, but we do not have to dig from one thousand to two thousand feet to reach the coal, as miners are obliged to do in some countries. But little coal has in this State been raised from a depth greater than one hundred feet.

Prof. Gustavus Hinrich, of the State University, who also officiated as State Chemist in the prosecution of the recent Geological Survey, gives an analysis showing the comparative value of Iowa coal with that of other countries. The following is from a table prepared by him— 100 représenting the combustible:

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In this table the excess of the equivalent above 100, expresses the amonnt of impurities (ashes and moisture) in the coal. The analysis shows that the average Iowa coals contains only ten parts of impurities for one hundred parts combustible (carbon and bitumen), being the purest of all the samples analyzed, except the Anthracite from Pennsylvania.

PEAT.

Extensive deposits of peat in several of the northern counties of Iowa have attracted considerable attention. In 1866, Dr. White, the State Geologist, made careful observations in some of those counties, including Franklin, Wright, Cerro Gordo, Hancock, Winnebago, Worth, and Kossuth. It is estimated that the counties above named contain an average of at least four thousand acres each of good peat lands. The depth of the beds are from four to ten feet, and the quality is but little, if any, inferior to that of Ireland. As yet, but little use has been made of it as a fuel, but when it is considered that it lies wholly beyond the coal-field, in a sparsely timbered region of the State, its prospective value is regarded as very great. Dr. White estimates that 160 acres of peat, four feet deep, will supply two hundred and thirteen families with fuel for upward of twenty-five years. It must not be inferred that the presence of these peat beds in that part of the State is in any degree prejudicial to health, for such is not the case. The dry, rolling prairie land usually comes up to the very border of the peat marsh, and the winds, or breezes, which prevail through the summer season, do not allow water to become stagnant. Nature seems to have designed these peat deposits to supply the deficiency of other material for fuel

. The penetration of this portion of the State by railroads, and the rapid growth of timber may lcave à resort to peat for fuel as a matter of choice, and not of necessity. It thereföre remains to be seen of what economic value in the future the peat beds of Iowa may be. Peat has also been found in Muscatine, Linn, Clinton, and other eastern and southern counties of the State, but the fertile region of

Northern Iowa, least favored with other kinds of fuel, is peculiarly the peat region of tho Stato.

BUILDING STONE

Thore is no scarcity of good bnilding stone to be found along nearly all the streains east of the Des Moines river, and along that stream from its month up to the north line of Humboldt county. Some of the counties west of the Des Moines, as Cass and Madison, as well as most of the southern counties of the State, are supplied with good building stone. Building stone of peculiarly fine quality is quarried at and near the following places: Koosauqua, Van Buren county; Mt. Pleasant, Henry county; Fairfield, Jefferson county; Ottumwa, Wapello county; Winterset, Madison county; Ft. Dodge, Webster county; Springvale and Dakota, Humboldt county; Marshalltown, Marshall county; Orford, Tama connty; Vinton, Benton county; Charles City, Floyd county; Mason City, Cerro Gordo county; Mitchell and Osage, Mitchell county; Anamosa, Jones county; Iowa Falls, Hardin county; Hampton, Franklin county; and at nearly all points along the Mississippi river. In some places, as in Marshall and Tama counties, several species of marble are found, which are susceptible of the finest finish, and are very beantiful.

LIME.

Good material for the manufacture of qnick-lime is found in abundance in nearly all parts of the State. Even in the northwestern counties, where there are but few exposures of rock “in place,” limestone is found among the boulders scattered over the prairies and about the lakes. So abundant is limestone suitable for the manufacture of quick-lime, that it is needless to mention any particular locality as possessing

superior advantages in furnish. ing this useful building material. At the following points parties have been engaged somewhat extensively in the manufacture of lime, to-wit: Ft. Dodge, Webster county; Springvale, Humboldt county; Orford and Indiantown, Tama county; Iowa Falls, Hardin county; Mitchell, Mitchell county; and at nearly all the towns along the streams northeast of Cedar river.

LEAD.

Long before the permanent settlement of Iowa by the whites lead was mined at Dubuque by Julien Dubuque and others, and the business is still carried on successfully. From four to six million pounds of ore have been smelted annually at the Dubuque mines, yielding from 68 to 70 per cent of lead. So far as known, the lead deposits of Iowa that may be profitably worked, are confined to a belt four or five miles in width along the Mississippi above and below the city of Dubaque.

GYPSUM.

One of the finest and purest deposits of gypsum known in the world exists at Fort Dodge in this state. It is cunfined to an area of about six by three miles on both sides of the Des Moines river, and is found to be from twentyfive to thirty feet in thickness. The main deposit is of uniform gray color, but large masses of almost pure white (resembling alabaster) have been found embedded in the main deposits. The quantity of this article is practically inexhaustible, and the time will certainly come when it will be a source of wealth to that part of the State. It has been used to a considerable extent in the manufacture of Plaster-of-Paris, and has been found equal to the best in quality. It has also been used to a limited extent for paving and building purposes.

SPRING AND WELL WATER.

As before stated, the surface of Iowa is generally drained by the rolling or undulating character of the country, and the numerous streams, large and small. This fact might lead some to suppose that it might be difficult to procure good spring or well water for domestic uses. Such, however, is not the case, for good pure well water is easily obtained all over the State, even on the highest prairies. It is rarely necessary to dig more than thirty feet deep to find an abundance of that most indispensible element, good water. Along the streams are found many springs breaking out from the banks, affording a constant snpply of pure water. As a rule, it is necessary to dig deeper for well water in the timber portions of the State, than on the prairies. Nearly all the spring and well waters of the State contain a small proportion of lime, as they do in the Eastern and Middle States. There are some springs which contain mineral properties, similar to the springs often resorted to by invalids and others in other States. In Davis county there are some “Salt Springs," as they are commonly called, the water being found to contain a considerable amount of common salt, sulphuric acid, and other mineral ingredients. Mineral waters are found in different parts of the

. State. No one need apprehend any difficulty about finding in all parts of Iowa an abundant supply of good wholesome water.

OLAY

In nearly all parts of the State the material suitable for the manufacture of brick is found in abundance. Sand is obtained in the bluffs along the streams and in their beds. Potter's clay, and fire-clay suitable for fire-brick, are found in many places. An excellent article of fire-brick is made at Eldora, Hardin county, where there are several extensive potteries

in operation. Fire-clay is usually found anderlying the coal-seams.

There are extensive potteries in operation in the counties of Lee, Van Buren, Des Moines, Wapello, Boone, Hamilton, Hardin, and perhaps others.

MINERAL PAINT.

In Montgomery county a fine vein of clay, containing a large proportion of ochre, was several ycars ago discovered, and has been extensively used in that part of the State for painting barns and out-houses. It is of a dark red color, and is believed to be equal in quality, if properly manufactured, to the mineral paints imported from other States. The use of it was first introdued by Mr. J. B. Packard, of Red Oak, on whose land there is an extensive deposit of this material.

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