Page:Encyclopædia Britannica, Ninth Edition, v. 1.djvu/359

Rh OPERATIONS.] AGRICULTURE 333 clay soils seems also a reason why in such cases it should get the benefit of a greater fall, by making the drain deep. Draining is always a costly operation, and it is therefore peculiarly needful to have it executed in such a way that it shall be effectual and permanent. We advocate a minimum depth of four feet, because of our strong conviction that such drains carefully made will be found to have both these qualities. And this opinion is the result of dear-bought experience, for we have found it necessary in our own case to re-open a very considerable extent of 30-inch drains in consequence of their having totally failed to lay the land dry, and to replace them by four feet ones, which have proved perfectly efficacious. In doing this we have seen a 30-inch drain opened up and found to be perfectly dry, and yet when the same trench was deepened to four feet there was quite a run of water from it. Now also that steam power has become available for the tillage of the soil, and is certain, at no distant day, to be in general requisition for that purpose, it is peculiarly expedient to have the drains laid at such a depth as to admit of that potent agency being used for loosening the subsoil to depths hitherto unattain able, not only without hazard to the drains, but with the certainty of greatly augmenting their efficiency. Therefore we earnestly dissuade all parties who are about to undertake drainage works from giving ear to representations about the sufficiency and economy of shallow drains. These, doubtless, cost somewhat less to begin with, but in thousands of cases they fail to accomplish the desired end, and the unfortunate owners, after all their outlay, are left to the miserable alternative of seeing their land imperfectly drained, or of executing the works anew, and thus losing the whole cost of the first and inefficient ones. The extreme reluctance with which the latter alternative is necessarily regarded will undoubtedly operate for a long time in keeping much land that has been hastily and imperfectly drained from partici pating in the benefits of thorough drainage. The distance apart at which the drains should be cut must be determined by the nature of the subsoil. In the most retentive clays it need not be less than 18 feet. On the other hand, this distance cannot safely be exceeded in the case of any sub soil in which clay predominates, although it should not be of the most retentive kind. In all parts of the country instances abound in which drains cut in such subsoils, from 24 to 30 feet apart, have totally failed to lay the land dry. When ground is once pre-occupied by drains too far apart, there is no remedy but to form a supplementary one betwixt each pair of the first set ; and thus, by exceeding the proper width at first, the space betwixt the drains is unavoidably reduced to 12 or 15 feet, although 18 feet would originally have sufficed. It is only with a decided porosity in the subsoil, and in proportion to the degree of that porosity, that the space between drains can safely be increased to 24, or 30, or 36 feet. In those exceptional cases in which drains more than 36 feet apart prove effectual, their success is due to the principle on which Elkington s system is founded. A few years ago an opinion obtained currency, that as the depth of drains was increased their width apart might with safety be increased in a corresponding ratio. And hence it came to be confidently asserted, that with a depth of 5 or 6 feet a width of from 40 to 60 feet might be adopted with a certainty of success, even in the case of retentive soils. We believe that experience has already demonstrated the unsoundness of this opinion. At all events, in recommending a minimum depth of 4 feet, we do so on the ground that (other things being equal) the whole benefits of drainage are more fully and certainly secured by drains of this depth than by those of 2| or 3 feet. In ordinary cases an increase of depth does not compensate for an increase of the width apart of the drains. Draining can be carried on at all seasons, but is usually best done in summer or autumn. The digging is usually paid for by task work, and the setting of the pipes by day s wages. A thoroughly trustworthy and experienced workman is selected for the latter work, with instructions to set no pipes until he is satisfied that the depth of the drains and level of the bottoms are correct. When the soil is returned into the drains all defects are of course buried, and it therefore be hoves the landlord, or his substitute, whether tenant cr bailiff, to exercise a vigilant oversight of draining operations. Unless carefully executed they cannot be efficient; and with out efficient drainage all other agricultural operations must be carried on under grievous disadvantages. The extent of land in Great Britain naturally so dry as not to need artificial drainage is very much less than even practical farmers, who have not studied the subject, are at all aware of. Cylindrical pipes with collars are undoubtedly the best Pipes, draining material that has yet been discovered. The collars referred to are simply short pieces of pipe, just so wide in the bore as to admit of the smaller pipes which form the drain passing freely through them. In use, one of these collars is so placed as to encase the ends of each contiguous pair of tubes, and thus forms a loose fillet around each joining. The ends of these pipes being by this means securely kept in contact, a continuous canal for the free passage of water is infallibly insured, the joinings are guarded against the entrance of mud or vermin, and yet sufficient space is left for the admission of water. Pipes of all diameters, from 1 inch to 1 6 inches, are now to be had ; those from 1 to 2 inches in the bore are used for subordinate drains ; the larger sizes for sub-main and main receiving drains. Collars are used with the smaller sizes only, large pipes not being so liable to shift their position as small ones. In constructing a drain, it is of much importance that the bottom be cut out just wide enough to admit the pipes and no more. Pipes, Avhen thus accurately fitted in, are much less liable to derangement than when laiel in the bottom of a trench several times their width, and into which a mass of loose earth must necessarily be re turned. This accurate fitting is now quite practicable in the case of soils tolerably free from stones, from the excellence of the draining tools that have lately been introduced. The following cut represents the most import ant of these tools. c and e are long tapering spades for digging out the miel- dle and bottom spits. a, d, and/ recurve el scoops for clearing out the debris, and b a pipe-layer, by means of which a workman standing at the margin of a drain hooks up a pipe and collar, and deposits them easily and accurately in the deep narrow trench. If a quicksand is encountered in constructing a drain, it will be found expedient to put a layer of straw in the bottom of. the trench, and then, instead of the ordinary pipe and collar, to use at such a place a double set of pipes one within the other taking care that the joinings of the inner set are covered by the centres of the outer ones. By such precautions the water gets vent, and the running sand ia excluded from the drain. When a brook has been diverted from its natural course for mill-power or irrigating purposes, it often happens that portions of land are thereby deprived of the outfall required to admit of their being drained to Dr. iimii&quot; Tools.