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of the Amazon represents the waste of half the Andes. The delta of the Mississippi is a newly created world of every kind of mineral stuff ; some of it brought from the coal measures of Pennsylvania and Virginia; some of it from the devonian and silurian sandstones, slates, and limestone strata of Ohio, Indiana, Kentucky, and Tennessee; some of it from the granite hills, the iron ore beds, the copper traps, the huronian jasper rocks of Wisconsin and Minnesota; some of it from the great flat outspreads of cretaceous sands and clays of Arkansas, Kansas, Idaho, and Montana; some of it from the lignite and clay beds of the bad lands of the Missouri and its branches ; some of it from the trias, carboniferous, devonian, and silurian formations, the tertiary parks, the granite cañons, the trap dykes and gold veins of Colorado; and some of it from the most recent of all the formations, the northern drift, carried from the mountains of upper and lower Canada by ice, resting for a time on the northern belt of the United States, and afterwards swept, grain by grain, down to New Orleans.

The soil of Louisiana may, therefore, be truly said to represent the entire geology of North America, being a mixture of all known rocks reduced to a fine sand, loam, or mud. Hence its fertility.

The Susquehanna river is forming a delta in Chesapeake bay; and if this delta be ever lifted out of water by a slight rise of the continent, or a slight fall of the ocean, it will be fertile with all the elementary minerals translated from the coal measures, both anthracite and bituminous; the red shale of Catawissa and Trough valleys; the white and red sand washed from the flanks of all our mountains from the North or Kittatanny to the Bald Eagle and Allegheny mountains; the grey and olive Chemung and Portage sands and clays from the State of New York; the red shale of the Buffalo, White Deer, Stone, and Frankstown valleys where they mine the fossil ore; slate and limestone mud from the Nittany, Kishicoquilis, Cumberland, and Lancaster valleys; micaceous mud from the South mountains, and the plain of York county, and the red sand and clay of the trias belt in Lancaster, York, and Adams counties.

In this way all the varieties of soil are mixed together to make a delta soil. All the alkalies and all the metals are present. Silica is abundant in the pure form of minutely broken crystals and rounded grains. The silicates of alumina, lime, potash, magnesia, and soda are present as equally minute fragments or rounded grains of the mother rock. The carbonates of lime, magnesia, and iron, present in the same form; grains of gold, of silicate of zinc, of sulphide of iron, of sulphide of copper, of hornblende, of tourmaline; flakes of mica; grains of magnetic and titanic iron and brown and red hematite; my riads of microscopic fragments of shells, corals, fossil fish-bones and coal-make up the motley crowd.

Of course every plant that can bear the summer's heat or winter's cold of Pennsylvania, at the sea level, would find its mineral sustenance and stimulus in such a soil, and without working hard for it.

2. This is the second point, and one as important as the first. Not only are all the mineral elements there—not only are they all there in boundless profusion and unlimited plenty-they are there so thoroughly mixed and so loosely compacted that the indolence of the most feeble plant finds no excuse for going hungry; and they are mixed to such a depth that innumerable generations of plants cannot find bottom to this treasury of vegetable life.

The finest soil will remain barren, however, without moisture, and famines have occurred in India for lack of rain. In Egypt, where rain seldom falls, the periodical inundations of the Nile answer the purpose of rain. Each spreads a thin layer of fresh compound over the surface. During the dry months of the year a thin layer of calcareous sand blown from the desert is laid down. The delta is thus composed of alternate layers of lime, sand, and mud, which are mixed together by means of the plow and the hoe. The naturally rich soil receives from the hand of nature every year a top dressing of lime. These alternations have been bored through by scientific explorers to a depth of seventy feet, and the evidences of man's occupation of the surface have been found at all depths. Calculations of the rate of the deposit make it probable that the lowest layers reached in the borings were deposited seventeen thousand years ago. Man was even then rejoicing in a bounteous fertility of soil annually manured with lime by the river and the winds. This accounts for the fact that the Egyptian civilization preceded all others, and that the Roman Empire depended upon Egypt as its granary from century to century.

3 AGRICULTURE.

3. It is needless to pursue the foregoing train of thought to bring into strong relief another point, viz: the contrast between the soils of uplands and lowlands. This contrast can stated in a few words.

Lowland soils, especially the soils of river bottoms, resemble delta soils in the variety of their mineral elements, in the looseness with which they lie together, and in the natural manuring to which they are subjected in years of unusually high water. Rich in their origin, their fertility is restored and enhanced by every disastrous flood. Patches may be ruined by the local deposit of bowlders and gravel; but the whole is improved for the use of man. Parts may be washed away; but the stuff removed from the river bank bigher up manures the surface lower down the valley.

Highland soil is just the reverse of all this. Its origin is not from a distance; but on the spot. The soil of a hill-side is a decomposition, or rather disintegration, of the rocks of the hill itself. The whole surface of the earth is mouldering. Every outcropping rock, whether hard or soft, granite, gneiss, greenstone, serpentine, mica slate, conglomerate, sandstone, clay, shale, coal, iron ore, limestone, is slowly but surely turning into soil under the influence of sunshine and frost. Heat expands it; cold contracts and cracks it; rain pervades it; frost pushes the particles asunder, and makes room for vegetable fibers, which widen and dea pen the fissures. Carbonic acid in the rain dissolves the crystals and rock grains, and thus each layer in the hill has its exposed edge sooner or later turned to soil, of a quality similiar to the rock out of which it has been made, and of a depth proportionate to hardness or softness, solubility or insolubility of the layers now underneath it.

The Quality and Thickness of Soils. It must be kept in mind that the term soil has two meanings; for there are two layers of it on the rock-an upper and an under; soil and subsoil. The latter is the geological soil; the former is the agricultural soil. As the sub-soil is made of the rocks beneath it by decomposition, so the soil, in its turn, is made of the sub-soil beneath it by composition. The first change is purely chemical and mechanical, and would take place if there were neither vegetable nor animal life on the earth. The second change takes place through the agency of plants and animals.

A tree takes in its food through a thousand mouths—its leaves and its rootlets. By its leaves it consumes carbonic acid from the air, and by its roots it consumes water from the earth. Its process of digestion consists in separating from the carbonic acid the carbon, and casting back the oxygen into the air; and from the water the hydrogen, again casting away the oxygen into the air. It compels carbon and hydrogen to combine, and fixes them in its body as wood, bark, leaf, blossom, fruit and gum. It sends them, thus combined, to its twigs, and to the tips of its rootlets; just as an animal sends its own food to the top of its head and to the extremities of its wings, hands, and feet. Thus the tree lengthens itself, expands itself, rises higher and broader into the air, and burrows deeper and wider into the soil.

But in doing so it not only breaks up the sub-soil but fills it with solid carbon. The herbs, the grasses perish and leave their lower parts a permanent part of the sub-soil, while their upper parts rot upon its surface.

Meanwhile the earth-worms, beetles, ants, ground squirrels, ground hogs, &c., move about in the mass, open it, compress it, turn it up, and turn it over like millions of tiny plowshares, and weave together the upper and lower layers (the soil and the sub-soil) permitting the carbon to sink, applying ammonia to the constituents, and converting the whole into a sponge which the rains keep soaked, and penetrate, to attack the face and fissures of the rocks beneath ; and thus the decomposition of the rock advances always more and more downward, and the sub-soil deepens; while the vegetation is adding layer on layer to the over-soil above.

1. The quality of the subsoil then must differ from the quality of the upper or true soil. The subsoil is the first change from the rock; the upper soil is a subsequent change from the subsoil. A geological survey should state, 1. The mineral qualities of the mother rock; 2. The mineral qualities of the subsoil; 3. The mineral qualities of the upper soil. And as these two sets of changes go on with different rapidity and in different manners according to the rock formation from which the change first starts, the investigation is a very broad one; in fact, should be pursued in every district of the State, and along the outcrop of every one of our formations.

The distinguished chemist, Doctor F. A. Genth, who is the official mineralogist of the Geological Survey, and chemist of the Board of Agriculture, has devoted a considerable part of his professional life to the analysis of soils and to the analysis of manures, both natural and artificial.

In speaking of the important part which ( as everybody knows) phosphorus plays in agriculture, he has assured me that of the many hundreds of analyses of rocks which he has made, he never found a single one which did not contain phosphorus; sometimes, of course in such small quantity as to afford a mere trace; but, nevertheless, always some.

This leads us to the sure conviction that no soil is destitute of phosphorus, although some soils undoubtedly hold an insufficient quantity, and would be benefited by the addition of more through manures.

Now, if the quantity of phosphorus in soils greatly varies, as it must, it is evident that the farmer ought to know beforehand how much his own farm soil holds ; so that he can decide what and how much of a phosphate dressing he shall give that soil, without having to go through a life time of experimenting himself/experimenting which must be, after all, as unsatisfactory and uncertain as it is tedious, anxious, and costly.

Still more needful to him is this scientific knowledge if his farm stretches across the edges of half a dozen different geological formations; for then he must necessarily have on his farm half a dozen belts of entirely different kinds of soil, each of which he knows by experience to require some sort of different treatment; but he ought to know exactly why the different fields in his farm cannot be farmed alike. He ought not to be content with suspecting that the soil in one of his fields has more phosphorus in it, and another less—or more sulphur, or more iron. He ought to be certain of it; and he ought to know exactly how much more, or how much less.

This is precisely the kind of knowledge which a geological survey is intended to give to farmers.

First, it should follow all the outcrops of the formation through the State.

It should find out the fixed order in which they lie to each other.
It should find out the width of the belt of soil which each one makes.

It should publish maps to show the farmer how these belts run through a county or a township. He can then easily find out for himself where they are in his neighborhood, and which of them cross his farm. He can decide for himself wbether the geologists are wrong or right. He can increase his own knowledge by correcting their mistakes. For all men, in all businesses, must make mistakes. And ten to one he will have his eyes opened to a good many very important truths which he never thought of before, and to some important facts which he never had given himself the pains to look at or ask questions about, because he never knew that they could concern him—a farmer—not a miner or a furnace manin any way at all.

It is astonishing how important to us certain things sometimes turn out to be which we have always thought concerned only other people.

A geological survey then having studied the order, the thickness, and the direction which different rock formations take across country and through the farms, its next business is to study the individual beds of each formation to see whether they are sandy, clayey, or limy, and whether they contain phosphorus, sulphur, potash, soda, magnesia, iron, &c., in large or small quantities relatively to each other. I do not mean as ores, but as rocks. For rocks are gradually turned into soils; and this study of the rocks leads directly to the knowledge of the soils.

If a rock is full of iron—not enough to make it an iron ore—it will make a soil rich in iron. If the iron is in the rock in the form of crystals or grains of iron pyrites, (sulphide of iron,) then its soil will contain a considerable quantity of sulphur.

If the formation be of limestone, and some of its beds are made up half of carbonate of lime and half of carbonate of magnesia, then the farmer's fields must necessarily be streaked with magnesian soils. He will call his farm - limestone land; " but in fact, his real limestone land lies only in streaks across his farm, the intermediate streaks being dolomite land, that is, half lime, half magnesi

If a great many beds together are limestone, his streaks of limestone soil will be broad, and very distinct from his magnesiau soil. But if on the contrary every alternate bed in the formation be limestone, and every alternate bed dolomite, then the streaks of different soil will be so narrow and numerous that the plowing of many years, and the slow creeping of the soil itself on the rock through ages, will have mixed the different streaks of soil together, and the whole surface will be of one general character, intermediate between pure limestone land and dolomite land.

When a farmer has resolved to lime his land he opens a quarry, and burns the stone. But what beds does he quarry and burn? The quality of his quicklime will depend entirely on which bed of rock he quarries. If he takes, as most farmers do, any rock which happens to stick its head above the surface, it may be a limestone almost pure from magnesia, or it may be a bed of dolomite, half carbonate of lime, half carbonate of magnesia.

A chemist ought to be able to tell him the difference, after analysing the rock. But the geologist alone can tell him whether the pure lime rock which he needs lies concealed to the right or to the left, above or below, north or south of the one which he has badly chosen for his quarry.

Still more important would it be if we knew how much phosphorus each of the limestone beds in a whole formation contained ; for then those particular beds might be selected for quarrying and burning.

It was to settle the possibility of such precise knowledge, so useful to the farmer, that the geological survey undertook last spring a chemical investigation of about one hundred beds in the middle of the great limestone formation at Harrisburg. The investigation is not yet finished, but already knowledge has been obtained, which is new to geologists, and important, not only to farmers, but to iron men and others who use lime.

We have long known that the older limestone formations were highly magnesian.

We have long known also that in the midst of the magnesian limestones (or dolomites) lay beds of almost pure limestone; but it was not known what proportion of the limestone beds were magnesian, nor whether there was any order or regularity in the deposits.

We now discover a very remarkable (and still unexplained) alternation of magnesian and non-magnesian beds, as the following table will show.

The mixture of magnesia with lime in dolomite rocks has always stimullated and baffled geological speculation, and given birth to opposite hypotheses; some of them, such as that of the issue of magnesium vapors from the interior of the earth, absurd enough; others, such as that recently propounded by Mr. W. L. Green, British minister at Honolulu, who derives the magnesia from olivine in lava, very suggestive.

I have long felt that no sound basis for speculation was secured so long as the collection of facts consisted merely of analyses of sporadic specimens of limestone and dolomite rocks. I therefore directed Mr. R. H. Sanders, of the Pennsylvania Geological Survey, to make a careful section of the siluro-cambrian strata exposed for a quarter of a mile along the west bank of the Susquehanna river, opposite Harrisburg, both by the deep cuttings of the Northern Central railroad and by quarries. This was done in connection with his field work in Cumberland county.

The beds in the exposure lie perfectly comformable one upon the other, and dip regularly about 30° to the southward, down the river, and without plications.

Mr. Joseph Hartshorne was also directed to take duplicate samples from every stratum, thick or thin, in this section; one at railway grade, and the other at the top of the exposure (sometimes thirty feet high) and to analyse them in the laboratory of the survey at Harrisburg. This he has done, and is still doing, devoting his entire time and attention to the selection of the samples in situ, and their determination in the laboratory. In all cases of doubt, the analyses have been duplicated, and sometimes triplicated.

When analyses of the first forty-six beds (from the top) had been made, it was evident that the generalization which must, sooner or later, come out of this series of analyses and of others similar to it which geologists would undoubtedly institute, must be both interesting and important. I availed myself therefore of an opportunity at a meeting of the American Philosophical Society in Philadelphia, held December 21, 1877, to state what had been done by Mr. Hartshorne in the laboratory of the survey

at Harrisburg up to that time, for the information of chemists and geologists at home and abroad; and this was published in the proceedings of the society in the following January.

In the course of the winter of 1878, Mr. Hartshorne continued his analyses. But in revising his work and comparing his numbers with those

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