some ditch or other superficial outlet. At 18 inches attraction will, on the average of soils, act with considerable power. Here, then, you have two obnoxious principles at work, both producing cold, and the one administering to the other. The obvious remedy is to destroy their united action; to break through their line of communication. Remove your water of attraction to such a depth that evaporation cannot act upon it, or but feebly. What is that depth? In ascertaining this point we are not altogether without data. No doubt depth diminishes the power of evaporation rapidly. Still, as water taken from a 30 inch drain is almost invariably two or three degrees colder than water taken from 4 feet, and as this latter is generally one or two degrees colder than water from a contiguous well several feet below, we can hardly avoid drawing the conclusion that the cold of evaporation has considerable influence at 30 inches, a much diminished influence at 4 feet, and little or none below that depth. If the water-table is removed to the depth of 4 feet, when we have allowed 18 inches of attraction, we shall still have 30 inches of defence against evaporation; and we are inclined to believe that any prejudicial combined action of attraction and evaporation is thereby well guarded against. The facts stated seem to prove that less will not suffice.

So much on the score of temperature, but this is not all. Do the roots of esculents wish to penetrate into the earth— at least, to the depth of some feet? We believe that they do. We are sure of the brassica tribe, grass, and clover. All our experience and observation deny the doctrine that roots only ramble when they are stinted of food; that six inches well manured is quite enough, better than more. Ask the Jerseyman; he will show you a parsnip as thick. as your thigh, and as long as your leg, and will tell you. of the advantages of 14 feet of dry soil. You will hear of parsnips whose roots descend to unsearchable depths. We will not appeal to the Kentucky carrot, which was

F

drawn out by its roots at the antipodes; but Mr. Mechi's, if we remember right, was a dozen feet or more. Three years ago, in a midland county, a field of good land in good cultivation, and richly manured, produced a heavy crop of cabbages. In November of that year we saw that field broken into in several places, and at the depth of 4 feet the soil (a tenacious marl, fully stiff enough for brickearth) was occupied by the roots of cabbage, not sparingly -not mere capilla-but fibres of the size of small packthread. A farmer manures a field of four or five inches of free soil reposing on a retentive clay, and sows it with wheat. It comes up, and between the kernel and the manure it looks well for a time, but anon it sickens. An Irish child looks well for five or six years, but after that time potato-feeding, and filth, and hardship, begin to tell. You ask what is amiss with the wheat, and you are told that when its roots reach the clay they are poisoned. This field is then thorough-drained, deep, at least four feet. It receives again from the cultivator the previous treatment; the wheat comes up well, maintains throughout a healthy aspect, and gives a good return. What has become of the poison? We have been told that the rain-water filtered through the soil has taken it into solution or suspension, and has carried it off through the drains, and men who assume to be of authority put forward this as one of the advantages of draining. If we believed it we could not advocate draining. We really should not have the face to tell our readers that water, passing through soils containing elements prejudicial to vegetation, would carry them off, but would leave those which are beneficial behind.* We cannot make our water so discriminating; the general merit of water of deep drainage is, that it contains very little. Its perfection would be that it should contain nothing. We understand that experiments are in progress

We do not deny that some subsoils contain matter prejudicial to vegetation, but generally they are not worse than a caput mortuum; seldom quite so bad.

which have ascertained that water, charged with matters which are known to stimulate vegetation, when filtered through 4 feet of retentive soil, comes out pure.*

But

to return to our wheat. In the first case, it shrinks before the cold of evaporation and the cold of water of attraction, and it sickens because its feet are never dry; it suffers the usual maladies of cold and wet. In the second case, the excess of cold by evaporation is withdrawn; the cold water of attraction is removed out of its way; the warm air from the surface, rushing in to supply the place of the water which the drains remove, and the warm summer rains, bearing down with them the temperature which they have acquired from the upper soil, carry a genial heat to its lowest roots. Health, vigorous growth, and early maturity are the natural consequences.

We think we have established that all soils will be benefited by the removal of the water-table to 4 feet, which must suffice under this head: and we think every candid reader will be convinced that, by this single operation of lowering the water-table, many soils, hitherto sterile, and consequently much underrated, may be made into useful agricultural land. We will take together the fourth and fifth heads they will occupy only a few sentences. They relate to the depth and direction of the drains by which the water-table is to be lowered.

Water can only get into drains by gravity, which only acts by descent-technically, by fall; the fall must be proportioned to the friction which the water encounters on its passage. Suppose drains 4 feet deep to be placed 12 yards apart on level land, it is plain that water at that depth, lying at the intermediate point between the two drains, will not get into either of them. A fall of some inches will be required to enable it to overcome the friction of 6 yards of retentive soil. In order, therefore, to lower the water-table to 4 feet at all points, the drains must be

* Since this Essay was first printed, a portion of these experiments has been communicated to the public by Professor Way.

some inches deeper than 4 feet. If the land lies on a slope (say 4 inches to the yard), drains of 4 feet, if driven on the line of steepest descent, will effect the object; because, though water at 4 feet, lying at the intermediate point between two drains, in a line at right angles to them, cannot for want of fall get into either of them by travelling 6 yards, it will find a fall of 4 inches at less than 7, and of 8 inches at less than 8, yards. If we must speak quite correctly, this intermediate water will never get into the drain till there is a fresh supply; it will descend perpendicularly, pushing out that which lies below it, and will be itself displaced by a fresh arrival from the heavens. In order that the whole soil, if homogeneous, or nearly so, may be drained evenly, it is manifest that the drains must be parallel. Extra friction in the soil must be met either by making the drains deeper, or by placing them nearer. On this point, which is one of practice rather than of principle, each case must be left to the sagacity of the operator. We doubt whether in any natural soil the friction is so great as to resist a fall of 1 inch in a yard. If we are right in this point, we should always attain the object of lowering the water-table to 4 feet by 4 feet 6-inch drains, parallel, and 12 yards apart. We have already stated one advantage which results on a slope from driving the parallel drains in the line of steepest descent: to wit, that when they are so driven, all water which lies at the same depth from the surface as the bottoms of the drains, can find a fall into one or the other by travelling a little more than half the distance between them; whereas, if the drains are driven across the slope, half the water so situated as to depth can only find a fall into the lower drain, and in order to reach it must travel distances varying from one-half to the full interval between the two. Smith, of Deanston, stated one reason for the steep course, namely, that on slopes alternate horizontal beds of porous and retentive soil frequently cropped out; that the water issuing from the lower edge of the porous runs over the

surface of the retentive; that a drain driven across the slope in the retentive leaves this issue untouched: whereas, a drain driven in the line of the slope cuts every one of these horizontal beds, draws the water to the depth of the drain out of the porous, and stops the overflow. Some one comes forward, and says,—"I have seen a case where the alternate beds are parallel, not overlying, perpendicular, not horizontal, and lie in the line of the slope. There your rule will not apply." Quite true! but Smith's case frequently occurs, and is worthy of a general observation; yours is very rare, and is not. You must deal with it according to your ingenuity. But perhaps the greatest recommendation of the steep drain is, that the water gets so freely out of it: it is no sooner in the drain than you are rid of it: whereas, in the horizontal drain it lingers, lying against the lower side, oozing through the land and inviting attraction. In very steep lands, the general direction of the natural cracks is across the line of slope, for the same reasons of gravity as in landslips, breaks in embankments, and other similar cases. Many valleys seem to have obtained their present form by a succession of little landslips, which are still in progress where a stream is washing away the foot. In such cases the steep drain cuts through all the cracks, and relieves them of their water. We now come to the conduit.

If sticks, straw, clods, and the mole-plough have not entirely fled before modern improvements, we should unworthily detain our readers by occupying a single line in giving them a parting kick. Stones must not be dismissed quite so summarily: they form an imperfect conduit, but we cannot say that in no situation is it advisable to use them. Many wet common lands on their enclosure, and many of the slopes of moorland hills when first brought into arable cultivation, are exceedingly encumbered with stones. It is almost as cheap to bury them in 4 or 5-feet drains as to cart them into heaps. We have seen instances where as many stones came out of the drain as would form