ized state of the soil has an influence upon the capillary diffusion of water, but especially its being equally or unequally pulverized, so that usually the distribution is more perfect throughout strata which are equal in this respect, than throughout those which are unequal.

The distribution of the water, which is drawn up from below through capillary attraction, is as unequal as the different kinds of earth. If one puts flowerpots, filled with sand, loam and humus soil, in dishes of water, the absorption of the same will take place in a very different way; and the length of time within which the absorbed. water will appear at the surface will vary very much, also.

CHAPTER III.

DRAINAGE REMOVES STAGNANT WATERS FROM THE SURFACE.

FROM the preceding chapter it will be seen that a drained soil is necessarily more porous than an undrained one; consequently, when a rain falls, the water which does not immediately flow off from the surface, escapes through the pores. On an undrained soil the water becomes stagnant, because the pores are already filled with water which has no means of escape other than by evaporation. A hard impervious subsoil prevents it filtering through it, and sinking down where the roots will be uninjured by it. Furnish under currents for the water, by means of drains, and there is no longer a necessity for the water to remain above ground, until it becomes changed from a healthful to a poisonous substance, by the continued action of heat and atmospheric air upon it.

The amount of water which may be evaporated from the surface, under the various influences which cause and control this evaporation, as well as the quantity which passes downward by means of filtration through the subsoil, or into the drains, is a matter of the greatest importance to every person engaged in the cultivation of the soil.

Chemists assert that fully four times the amount of heat is required to convert water into vapor, that is required to bring it to the boiling from the freezing point. It is no uncommon occurrence that rain to the depth of one inch falls in the course of a shower. The amount falling on a single acre then would amount to 360 hogsheads, and to evaporate this amount of water by sunshine, would require

an amount of heat that would convert upward of 1,500 hogsheads of water from the freezing to the boiling point. Every one must know that this evaporation is a very slow process, and that while it is going on the soil is kept wet, and consequently cold; that vegetation is retarded, if not absolutely checked, especially in the early spring time Now, if these 1,500 hogsheads of water were carried off by drains, this great amount of heat necessary to evaporate would be saved, and would be applied to warming the soil.

Some interesting facts, in relation to this subject, are furnished by Cuthbert W. Johnson, in a late number of the Farmer's Magazine. Observations were made for eight successive years, in Hertfordshire, and the mean amount of rain which fell, was found to be for each year 26 inches, of which over 11 inches passed into the soil and was filtrated, and over 15 inches were evaporated from the surface. During the colder months, the amount filtrated was from three to six times as great as the quantity which passed off in the form of vapor. On the other hand, the quantity evaporated during the hottest months, was more than fifty times as great as the amount filtrated, the latter indeed, not amounting during a whole month to the twentieth of an inch.

The greatest quantity evaporated, in a single year, was about 1,800 tuns per acre, and the greatest quantity filtrated was over 1,400.

The rate of evaporation is influenced by the amount of moisture required by the different soils for saturation, and the degree of exposure to sun and winds. Even the direction of the prevailing winds, characterized by the moisture they contain, has a material influence. Several examples are given, by which it appears that the average amount of rain at the places of observation, was about 25 inches per year; that the evaporation from water exposed

to both sun and wind, was about 35 inches per year; shaded from the sun, but exposed to the wind, it was about 23 inches; from soil, when drained, about 20 inches; and from undrained soil, saturated with water, about 33 inches, an excess of 13 inches of water to be charged against an undrained soil.

These experiments were made with bare earth, free from herbage of any kind. By means of other experiments made with plants in pots, it was found that 22 square inches of surface of bare mold, evaporates in twelve days, 1,600 grains of moisture, while a pot of the same size, containing a polyanthus, evaporated 5,250 grains; showing conclusively the great rapidity with which plants carry off moisture, and the great error of those who suppose that weeds can be of any use in shading the soil.

Many persons presume that a comparatively small amount only of the water which falls in rain, on the surface of the earth, is retained by the soil, or is evaporated, but are of opinion that nearly all finds its way into rivers or smaller streams.

Some writers assert that almost the entire mass of water, from rains, is absorbed in supplying springs, and other subterranean streams. Marriotte, a celebrated French writer, has examined the point, with direct reference to whether the quantity of rain water is sufficient to feed all the springs and rivers, and so far from finding a deficiency, he concludes upon the amount being so great as to render it difficult to conceive how it is expended. According to observations which have been made, there falls annually upon the surface of the earth, about 19 inches of water; but to render his calculation still more convincing, Marriotte supposes only 15, which makes 45 cubic feet per square toise, and 238,050,000 cubic feet per square league of 2,300 toises, in each direction. Now, the rivers and

springs which feed the Seine, before it arrives at the Pont-Royal at Paris, embrace an extent of territory about sixty leagues in length, and fifty in breadth, making 3,000 leagues of superficial area; by which, if 238,050,000, be multiplied, he have for the product 714,150,000,000 for the cubic feet of water which fall, at the lowest estimate, on the above extent of territory. Let us now examine the quantity of water annually furnished by the Seine. The river above the Pont-Royal, when at its mean hight, is 400 feet broad and five deep; when the river is in this state, the velocity of the water is estimated at 100 feet per minute, taking a mean between the velocity at the surface and that at the bottom. If the product of 400 feet in breath by five in depth, or 2,000 feet square, be multiplied by 100 feet, we shall have 200,000 cubic feet for the quantity of water which passes, in a minute, through that section of the Seine above the Pont-Royal. The quantity in an hour will be 12,000,000; in a day 288,000,000; and in a year 105,120,000,000 cubic feet. This is not the seventh part of the water which, as previously stated, falls on the extent of country that supplies the Seine; the large remainder, not received by the river, being taken up by evaporation, beside a prodigious quantity employed for the nutrition of plants.1

Now, if this astounding calculation is true of France, what must be the condition of Ohio, and many other states where the annual rainfall is about 40 inches, or nearly three times the amount assumed by Marriotte. Think for a moment of the entire surface of Ohio, being annually covered more than a yard deep, with rain water! The autumn rains average about 10 inches, and generally thoroughly saturate the earth with water, so that when

1 Gallery of Nature, page 263.