The ratio in the last column is obtained by dividing the figures under artesian well by those under spring; or the ratio expresses how many times the water of the artesian well contains the amount of the elements in the spring water. If the elements were present in both of these waters in the same proportion, then 7.3, the ratio of the totals, would be the ratio for the several elements also. In fact, only the ratio for oxygen approaches to this ratio; all others differ very much from 7.3, &c. The ratio for sodium, sulphur and chlorine are particularly great; or in words, the water from the deep (artesian) well contains proportionally much more of sodium, sulphur and chlorine, than the water from near the surface (spring). The two waters, both from the same place, but from very different depths, therefore differ very much, not only in the total amount of mineral matter, but even more so in regard to the quality of the

The names in parenthesis are added for those of the readers who may not be familiar with the names of the salts.

The amount of salts even in the artesian well may appear insignificant only about one - fourth of one per cent! But when larger quantities of the waters are used, then these salts become plainly manifest to everybody. The steam engine at the Iowa Hospital for the Insane is reported to have pumped the water for use at the rate of ten thousand gallons an hour. This is more than eighty thousand pounds an hour, and the insignificant amount of salts is more than two hundred pounds per hour! At that rate the following pounds of the different salts would be brought up with the water each hour:

In the course of ten hours these salts would amount to a ton! Only a small amount of these used in a boiler would quickly produce a thick incrustation; the sulphates would remain pretty long in solution, so that a pretty concentrated brine might result-all of which has been so abundantly experienced that the water is no longer used for such purposes. In the proximate analysis of 1865 the chlorine was not determined. By my recent careful and complete analysis recorded above, it is seen that there is plenty of chlorine, which, in the presence of sulphuric acid and some free carbonic acid, may set free the corroding vapors of hydrochloric acid.

I intend to subject this water to still more scrutinizing analyses; then, together with the investigations of the specimen rock from the boring, the boiler deposits, the corroded iron tubes, and the surface water from the same place will form a whole of well ascertained facts for various levels from the surface to a depth of one thousand one

hundred and twenty-five feet, which I hope will lead to some general results.

One very interesting general result may already here be pointed out. If we calculate the per centage of the various salts in the two waters, we find:

SALTS.

PER CENTAGE.

Spring. Art'n Well.

Sodium sulphate.
Sodium chloride....

Magnesium sulphate.
Calcium sulphate.
Calcium carbonate..

This shows a marked decrease in the proportion of the lime salts, while the magnesium salts, and particularly the alkali, increase as we descend below the surface. The surface water is a calcareous carbonated water; the water from the deep is sulphated and alkaliwater. The latter are by far the most soluble of these salts; and this circumstance causes their accumulation in the deeper waters. Quite a similar change our surface waters undergo in their course toward the ocean. In the rivers there is but a small amount of mineral matter, and the carbonates of lime and magnesia dominate; both become less and less, both being deposited on the way to the ocean, which, like the water from the deep well at Mount Pleasant, only contains the most soluble salts. The more immediate cause of this change in the rivers is the life of aquatic animals; in the rocks the same change is brought about by the constant metamorphosis of the rock itself.

The preceding contains all the results ascertained in regard to the waters of the State. Compared with what remains to be done, it is very little; but compared with what had been done previously it is a good deal. So much is certain, a correct interpretation of the constitution of the rocky framework of the State can only be obtained by a careful chemical study of both the rocks and the waters they

contain.

II. THE ROCKS.

The rocks of Iowa belong to only four kinds; they are either calcareous, arenaceous, argillaceous, or carbonaceous. To the first

belong limestones and dolomites, both effervescing (at least) with hot acids. They greatly dominate in the State. The finest arenaceous rock of Iowa is the St. Peter's sandstone, exposed in the northeastern corner of the State; good sandstones are also found in the coalmeasures of Southern Iowa, and finely crystalized silicia, that is, quartz, abounds in the geodes found near Keokuk and other places. Shales are the most common representatives of the argillaceous rocks, passing by the dark, more or less combustible varieties gradually into coal, the most valuable carbonaceous rock of Iowa. Geologically, coal is as much rock as the limestone underlying the same, or the sandstone above it; it is found stratified like either of these two rocks.

These four kinds of rock are composed of but six different chemical elements. Three of these are metals, having, when pure, a lustre peculiar to these bodies; the other three are metalloids, being devoid of such lustre. The three metals are calcium, magnesium and aluminum, of which the last two are already quite frequently used in the arts; magnesium, the metal contained in epsom salts, being used for illuminating purposes, since it gives a most dazzling light; aluminum, the metal of clay, remarkable for its beautiful silver-like appearance and its excessive lightness, being not heavier than paper, is considerably used for certain alloys. Calcium has as yet not found any application in the arts. About forty pounds in every hundred pounds of pure limestone is calcium.

The three metalloids are oxygen, carbon and silicon. The first constitutes about one-fifth of the air we breathe, and is really the vital principle of the air; in our rocks it is present in much greater quantity than in the air, for it constitutes about one half of all of them (excepting coal). The second, carbon, is well known; in charcoal we have it nearly pure. Silicon is very closely allied to the former, sand being composed of silicon and oxygen in nearly equal proportions.

The following table will give a correct idea of the elementary composition of our Iowa rocks, by means of the per centage composition of the purest of each kind. The first three are very frequently met with almost chemically pure in crevices and openings in the rocks, constituting crystals. In limestone we thus find calcite or

calcium carbonate in beautiful crystals. If the limestone contains also the metal magnesium, we usually find the crystals to have a peculiarly pearly lustre, and somewhat curved faces; these crystals are called dolomite. In arenaceous rocks we find under similar circumstances the beautiful crystals of quartz. The other two rocks hardly ever occur quite so pure as here given, except it be carbon as diamond. These pure forms are the minerals corresponding to the rock; they are the rock purified by nature herself:

In dolomite, which in the north of the State forms immense fields contains one fifth by weight of the metal magnesium; if this is separated, it burns with great splendor. We may now readily conceive what an immense amount of heat and light has some time been produced when those elements, that are now dormant and under our feet, were still uncombined in the atmosphere, perhaps. Tolerably pure limestone contains twelve per cent, dolomite about thirteen per cent of pure coal; every hundred feet of limestone contains enough of pure coal to form a bank of anthracite of ten to twelve feet in thickness. But all of this combustible, both metalic and carbonaceous, is now unavailable, since these elements are in the rock, combined with oxygen; that is they are burnt. The only exception to this rule is the coal; for this reason it has so great economic value.

The coal having been at length considered in the first chapter, I