which most of the evil may lie. The nature of the bottom should be well tested by the iron-bar driven well into it and vent given to any veins which may be pent up below.

It would not be worth while to digress here to describe certain rare instances, on which I think too much stress has been laid by English drainers, where a stratum of clay, continuous with that which forms the permanent basis of the elevated ground, overlaps the porous soil of the elevation itself. Often, in these instances, a drain dug in a clayey soil affords but little water; but, on a hole being made with a boring instrument, water wells up profusely, because a tongue of clay is perforated which had extended up the elevation holding water imprisoned to a level much above the drain.

FIG. 5.

Fig. 5.-Imprisoned water liberated by a perforation through an overlapping tongue of clay.

The intercepting drain having been carried to a sufficient depth, it is to be tapped by other drains running to a suitable point of discharge, that the water received into its channel be quickly carried off. When these drains shall have been excavated, they should remain open, if possible, for some weeks, that their efficacy be thoroughly tested before they are filled and covered, of which we shall treat hereafter.

FIG. 6.

Fig. 6. Successful drainage. Drain cut exactly upon the "line of wet." We have thus considered the main features of what we have

termed active drainage; the principles of which cannot be too thoroughly understood by all whose agricultural lot is cast in a New England climate. There are few farms in our hilly country which would not be benefitted by some more or less modified form of this process.

PASSIVE DRAINAGE.

We started in our consideration of the subject of drainage with the assumption that water, retained upon or in the soil in excess, is prejudicial to vegetation. It will be worth staying here to consider how this acts unfavorably; and the importance of the process of drainage will, I think, be more apparent to the reader af'ter this has been considered. It will readily be admitted, that, whatever will raise the temperature of our cold soils will promote vegetation; and we take the belief for granted that retained water is the essential element in imparting to a soil that quality which we negatively term, cold. Water produces coldness chiefly by its evaporation. The coolness which succeeds the sprinkling of the floor of a warm room in summer, is a familiar instance of this. It is well known that ice can be produced in hot climates by evaporation simply. It is difficult to say, exactly, how much heat is extracted from a soil by the evaporation of a given amount of water; yet this result has been attained with at least an approximation to the truth. The evaporation of one pound of water from one hundred pounds of soil will reduce its temperature ten degrees; that is to say, if you put one hundred pounds of earth, then containing as much moisture as it will hold by ordinary attraction, into a vessel from which no water can escape by filtration, and then pour one pound of water additional to it, which must be liberated by evaporation simply, the latter process will carry from the whole of the soil ten degrees of heat. If, however, the vessel be so constructed that the excess of water can escape by filtration, no loss of heat will result. Now the records kept at the Massachusetts State Lunatic Hospital at Worcester show that, for the past four years, there has fallen during the six months of the year when vegetation is most active, an annual average of twenty inches of rain. It would be an interesting fact if we could know how much of this rain has been

soaked into the earth, and how much has evaporated from its surface. Unfortunately, we have not the data. If we can base conclusions from foreign experiments, we may assume that a little less than half of this quantity immediately passes beyond the direct influence of evaporation. If the soil on which this quantity of water falls is of a non-retentive or porous nature, the water pretty quickly passes by infiltration entirely beyond the sources of vegetable nutriment. Like the experiment we have already instanced, it exerts no evil influence on the temperature of the soil. But if the soil be of a retentive nature, like clay, or if there be below the surface, at a greater or less depth, an impenetratable stratum through which the water cannot pass, it is held in an inactive condition, and will prove, as we shall see, a source of evil. Now as all passive drainage is merely a method of facilitating the escape of water thus retained, the reader will perceive the conclusion to be arrived at. But this is not all. Water in its quiescent state is a very bad conductor of heat. It does not conduct heat at all, indeed, except as currents are established in it by heat applied below. Heat applied to the surface of still water, as all know, would be wholly ineffective. We will suppose that a retentive soil is charged with an excess of water, which has no escape but by the slow process of evaporation. Its ill effect is then two-fold; first, in carrying off the heat of the earth by evaporation, and, second, by preventing the solar heat of the surface from finding its way into the soil below. Suppose that water of the temperature of 48 degs. is retained in a stratum of "hard-pan," at three feet below the earth's surface, while the air at the surface is at 80 degs., a proportion most common to exist during warm summer weather. Now let a drain be cut through the same soil four feet in depth, which will immediately carry off the retained excess of water. The consequence will be, that the air at 80 degs. will find its way to fill the void caused by the departure of the water at 48 degs. This process is in constant operation in porous soils; after severe rains, water has supplanted the retained air in the soil, while the warm air of the surface, in its turn, takes the place of the water as it departs by a natural drainage below. This constant circu

lation of two essential elements of vegetation, is cf prime necessity for the healthy growth of plants. The accuracy of these statements may easily be tested by a simple experiment. Fill two leaching tubs of the common size for soap-making with soil of the same kind. Let one of these tubs drain itself freely, while the bottom of the other is tight. Collect the water as fast as it escapes from the drained one and pour it back at the top. A thermometer buried six inches in depth in each, respectively, will show a difference in favor of the soil in the drained tub, of several degrees.

The prime necessity of air for the growth of plants is acknowledged without dissent. Four-fifths of the benefit of hoeing and the use of the cultivator among plants arises from their rendering the soil permeable to air. Select a young and growing tree, around which, for ten feet from its body, spread a close plastering of clay. The diseased appearance which it will soon put on, and its eventual death, will demonstrate the necessity for the free introduction of this element. The reader will perceive, from an attentive consideration of these suggestions, the striking difference in effect produced by a shower during a hot day in summer, on a well drained and a retentive soil. The latter, already surfeited with moisture, declines the reception of any more-no change can take place in its temperature; the warm rain, with all its treasures of good, must flow off to the lower parts of its surface, and thence into the brook; while in the former, it will strike on the hot surface of the soil, and bear the heat there gathered into the greedy depths below, thence to pass away in readiness for the same providential repetition. .

We have made use of the terms retentive and non-retentive soils. A retentive soil is frequently made so, not from the inherent quality of the soil itself, but from the interposition of strata of too compact a texture for the water to find its way through them. In such a soil, the particular level at which water remains stagnant, is termed the "water-table." In a stiff clay this water-table is the surface of the ground itself; in a gravelly soil it may be two, three, or four feet from the surface. It is one of the purposes of drainage to remove the water-table beyond the

possibility of doing mischief to vegetation. We will endeavor to show some of the evils which follow when the water-table is within the proper sphere of vegetation.

When a dry sponge is suspended over a basin of water so that its lower part touches the surface, the water ascends, and, in process of time, fills the interstices of the sponge. This familiar occurrence is due to the power termed capillary attraction. Water will ascend in dry earth in a similar manner. Fill a common flower-pot, having a perforated bottom, with dry earth, and set it in a saucer filled with water. Of course the water in the earth will very soon reach the same height with the surface of that in the open saucer without. This level, which is supposed to be the same in both vessels, becomes the water-table. But from it water will continue to ascend by capillary attraction, till moisture is perceptible at the surface of the earth in the pot. It will be perceived then, that, however suitable for vegetation the temperature of the earth in the pot may be, the water standing below will be rising and being evaporated till earth and water very soon become of the same low temperature. All scientific florists, consequently, condemn this manner of supplying water to plants, which was formerly so common. We can hardly suppose that water below the surface of the earth, suspended by this water-table, will be above 45 degs. If the surface of the soil where the seed is deposited, and where vegetation is active, is at 65 degs., it will be seen, that there is an invisible cause at work constantly reducing them both to the same mean. Now if, upon a stratum of clay, a covering of loam of three inches is laid, the effect of the water-table so near the surface will be striking in a wet season even on plants requiring no great depth of earth, such as the grasses and cereals. They become yellow and dwarfish-their roots are bathed in too much water-they literally "take cold in the feet." If the water-table lies at the depth of eighteen inches, the effect is equally disastrous to taprooted esculents. The roots shrink from such a contact and become bulbous, or divide and seek the warmer upper soil instead of taking the usual direction. The obvious remedy for these