« AnteriorContinuar »
“ never discovered that the roots of any esculent vegetable “have obstructed a pipe. The trees which, by my own “personal observation, I have found to be most danger. “ous, have been red willow, black Italian poplar, alder “ ash, and broad-leaved elm. I have many alders in close “contiguity with important drains, and, though I have “ never convicted one, I cannot doubt that they are dan. “gerous. Oak, and black and white thorns, I have not “detected, nor do I suspect them. The guilty trees have “ in every instance been young and free growing; I have “never convicted an adult. These remarks apply solely “ to my own observation, and may of course be much “ extended by that of other agriculturists. I know an in“stance in which a perennial spring of very pure and (I “ believe) soft water is conveyed in socket pipes to a “paper mill. Every junction of two pipes is carefully “fortified with cement. The only object of cover being “protection from superficial injury and from frost, the “pipes are laid not far below the sod. Year by year these “pipes are stopped by roots. Trees are very capricious in “ this matter. I was told by the late Sir R. Peel that he “sacrificed two young elm trees in the park at Drayton “ Manor to a drain which had been repeatedly stopped by “ roots. The stoppage was nevertheless repeated, and “ was then traced to an elm tree far more distant than " those which had been sacrificed. Early in the autumn " of 1850 I completed the drainage of the upper part of a " boggy valley, lying, with ramifications, at the foot of “marly banks. The main drains converge to a commor "outlet, to which are brought one 3-inch pipe and three of 4 “inches each. They lie side by side, and water flows pe. “rennially through each of them. Near to this outlet did “ grow a red willow. In February, 1852, I found the 5 water breaking out to the surface of the ground about “ 10 yards above the outlet, and was at no loss for the “ cause, as the roots of the red willow showed themselves
* at the orifice of the 3-inch and of two of the 4-inch pipes. « On examination I found that a root had entered a joint “ between two 3-inch pipes, and had traveled 5 yards to " the mouth of the drain, and 9 yards up the stream, “ forming a continuous length of 14 yards. The root which “ first entered had attained about the size of a lady's little “ Anger; and its ramifications consisted of very fine and " almost silky fibres, and would have cut up into half a “ dozen comfortable boas. The drain was completely "stopped. The pipes were not in any degree displaced “ Roots from the same willow had passed over the 3-inch “pipes, and had entered and entirely stopped the first “ 4-inch drain, and bad partially stopped the second. At “ a distance of about 50 yards a black Italian poplar, “ which stood on a bank over a 4-inch drain, had com
pletely stopped it with a bunch of roots. The whole of “ this had been the work of less than 18 months, including " the depth of two winters. A 3-inch branch of the same " system runs through a little group of black poplars. “ This drain conveys a full stream in plashes of wet, and “some water generally through the winter months, but “ has not a perennial flow. I have perceived no indica« tion that roots have interfered with this drain. I draw “no general conclusions from these few facts, but they “may assist those who have more extensive experience in “ drawing some, which may be of use to drainers.”
Having considered some of the principles on which our work should be based, let us now return to the map of the field, and apply those principles in planning the work to be done to make it dry.
The Outlet should evidently be placed at the present point of exit of the brook which runs from the springs, cchects the water of the open ditches, and spreads over the flat in the southwest corner of the tract, converting it into a swamp. Suppose that, by going some distance into the next field, we can secure an outlet of 3 feet and
9 inches (3.75) below the level of the swamp, and that we decide to allow 3 inches drop between the bottom of the tile at that point, and the reduced level of the brook to secure the drain against the accumulation of sand, which might result from back water in time of heavy rain. This fixes the depth of drain at the outlet at 3, (3.50) feet.
At that side of the swamp which lies nearest to the main depression of the up-land, (See Fig. 21,) is the prop er place at which to collect the water from so much of the field as is now drained by the main brock, and at that point it will be well to place a silt basin or well, built up to the surface, which may, at any time, be uncovered for an observation of the working of the drains. The land between this point and the outlet is absolutely level, requiring the necessary fall in the drain which connects the two, to be gained by raising the upper end of it. As the distance is nearly 200 feet, and as it is advisable to give a fall at least five-tenths of a foot per hundred feet to so im. portant an outlet as this, the drain at the silt basin may be fixed at only 21 feet. The basin being at the foot of a considerable rise in the ground, it will be easy, within a short distance above, to carry the drains which come to it to a depth of 4 feet,—were this not the case, the fall between the basin and the outlet would have to be very much reduced.
Main Drains.—The valley through which the brook now runs is about 80 feet wide, with a decided rise in the land at each side. If one main drain were laid in the cen. ter of it, all of the laterals coming to the main would first run down a steep hillside, and then across a stretch of more level land, requiring the grade of each lateral to be broken at the foot of the hill, and provided with a silt basin to collect matters which might be deposited when the fall becomes less rapid. Consequently, it is best to provide two mains, or collecting drains, (A and C, ono lying at the foot of each hill, when they will receive the laterals at their greatest fall; but, as these are too far apart to completely drain the valley between them, and are located on land higher than the center of the valley, a drain, (B,) should be run up, midway between them.
The collecting drain, A, will receive the laterals from the bill to the west of it, as far up as the 10-foot contour line, and, above that point,-running up a branch of the valley, -it will receive laterals from both sides. The drain, B, may be continued above the dividing point of the valley, and will act as one of the series of laterals. The drain, C, will receive the laterals and sub-mains from the rising ground to the east of it, and from both sides of the minor valley which extends in that direction.
Most of the valley which runs up from the easterly side ** of the swamp must be drained independently by the drain
E, which might be carried to the silt basin, did not its continuation directly to the outlet offer a shorter course for the removal of its water. This drain will receive laterals from the bill bordering the southeasterly side of the swamp, and, higher up, from both sides of the valley in which it runs.
In laying out these main drains, more attention should be given to placing them where they will best receive the water of the laterals, and on lines which offer a good and tolerably uniform descent, than to their use for the immediate drainage of the land through which they pass. Afterward, in laying out the laterals, the use of these lines as local drains should, of course, be duly considered.
The Lateral Drains should next receive attention, and in their location and arrangement the following rules should be observed:
1st. They should run down the steepest descent of the land.
2d. They should be placed at intervals proportionate to their depth ;-if 4 feet deep, at 40 feet intervals; if 8 feet deep, at 20 feet intervals.