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'economy in using horse power, and even for this depth it will be necessary to use a plow having only one stilt.
Before the main line is cut into the open brook, this should be furnished with a wooden trough, which will carry the water across it, so that the ditch shall receive only the nitration from the ground. Those laterals west of the main line, which are crossed by the brook, had better not be opened at present,—not until the water of the spring is admitted to and removed by the drain.
The other laterals and the whole of the main line, having been cut to a depth of 3 feet, take a finishing spade, (Fig. 25,) which is only 4 inches wide at its point, and dig to within 2 or 3 inches of the depth marked on the stakes, making the hot- Fig. 25.—Pintorn tolerably smooth, with the I8HIIio SPADBaid of the finishing scoop, (Fig. 26,) and giving it as regular an inclination as can be obtained by the eye alone.
Often, large stones, which would cost much labor to remove, will be encountered in the digging. If these lie from 6 inches to a foot above the final grade, and are not too large, it will be easier to tunnel under them than to take them out, or to go around them; but, if they are very large, or he close to the bottom, (or in the bottom,) the latter course will be necessary.
If the ground is "rotten," and the banks of the ditches incline to cave in, as is often 'the case in passing wet places, the earth which is thrown out in digging must be thrown back sufficiently far from
to prevent its weight from increasing the tendency; and the sides of the ditch may be supported by bits of board braced apart as is shown in Fig. 27.
The manner of opening the ditches, which is described above, for the main A and its laterals, will apply to the drains of the whole field and to all similar work.
Grading the Bottoms.—The next step in the work is to grade the bottoms of the ditches, so as to afford a bed for the tiles on the exact lines which are indicated by the figures marked on the different stakes.
The manner in which this is to be done may be illustrated by describing the work required for the line from CIO to C17, (Fig. 20,) after it has been opened, as described above, to within 2 or 3 inches of the final depth.
A measuring rod, or square, such as is shown in Fig. 28,* is set at C 10, so that the lower side of its arm is at the mark 4.59 on the staff, (or at a little less than 4.6 if it is divided only into feet and tenths,) and is held upright in the ditch, with its arm directly over the grade stake. The earth below it is removed, little by little, until it will touch the top of the stake and the bottom of the ditch at the
* The foot of the measuring rod should be shod with iron to prevent Its being worn to less than the proper leugth.
same time. If the ground is soft, it should be cut out until a flat stone, a block of wood, or a piece of tile, or of brick, sunk in the bottom, will have its surface at the exact point of measurement. This point is the bottom of the ditch on which the collar of the tile is to lie at that stake. In the same manner the depth is fixed at C11 (4.19,) and G12 (4.41,) as the rate of fall changes at each of these points, and at 015 (3.89,) and C17 (4.17,) because (although the fall is uniform from (712 to C17,) the distance is too great for accurate sighting.
Having provided boning-rods, which are strips of board 7 feet long, having horizontal cross pieces at their upper ends, (see Fig. 29,) set these perpendicularly on the spots which have been found by measurement to be at the correct depth opposite stakes 10, 11, 12, 15, and 17, and fasten each in its place by wedging it between two strips of board laid across the ditch, so as to clasp it, securing tliese in their places by laying stones or earth upon their ends.
As these boning-rods are all exactly 7 feet long, of course, a line sighted across their tops will be exactly 7 feet higher, at all points, than the required grade of the ditch directly beneath it, and if a plumb rod, (similar to the boning-rod, but provided with a line and plummet,) be set perpendicularly on any point of the bottom of the drain, the relation of its cross piece to the line of sight across the tops of the boning-rods will show whether the bottom of the ditch at that point is too high, or too low, or just right. The manner of sighting over two boningrods and an intermediate plumb-rod, is shown in Fig. 31.
Three persons are required to finish the bottoin of the
ditch; one to sight across the tops of the boning-rods, one to hold the plumb-rod at different points as the finishing progresses, and one in the ditch, (see Fig. 30,) provided with the finishing spade and scoop,—and, in hard ground, with a pick,—to cut down or fill up as the first man calls
"too high," or "too low." An inch or two of filling may be beaten sufficiently hard with the back of the scoop, but if several inches should be required, it should be well
rammed with the top of a pick, or other suitable instrument, as any subsequent settling would disarrange the fall.
As the lateral drains are to be laid first, they should be the first graded, and as they are arranged to discharge into the tops of the mains, their water will still flow off, although the main ditches are not yet reduced to their final depth. After the laterals are laid and filled in, the main should be graded, commencing at the upper end; the tiles being laid and covered as fast as the bottom is made ready, so that it may not be disturbed by the water of which the main carries so much more than the laterals.
Tile-Laying.—Gisborne says: "It would be scarcely "more absurd to set a common blacksmith to eye needles "than to employ a common laborer to lay pipes and col
* lars." The work comes under the head of skilled labor, and, while no very great exercise of judgment is required in its performance, the little that is required is imperatively necessary, and the details of the work should be deftly done. The whole previous outlay,—the survey and staking of the field, the purchase of the tiles, the digging and grading of the ditches—has been undertaken that we may make the conduit of earthenware pipes which is now to be laid, and the whole may be rendered useless by a want of care and completeness in the performance of this chief operation. This subject, (in connection with that of finishing the bottoms of the ditches,) is very clearly treated in Mr. Hoskyns' charming essay,* as follows:
"It was urged by Mr. Brunei, as a justification for more 'attention and expense in the laying of the rails of the "Great Western, than had been ever thought of upon "previously constructed lines, that all the embankments "and cuttings, and earthworks and stations, and law and "parliamentary expenses—in fact, the whole of the out"lay encountered in the formation of a railway, had for its u main and ultimate object a perfectly smooth and level "line of rail; that to turn stingy at this point, just when
* you had arrived at the great ultimatum of the whole "proceedings, viz: the iron wheel-track, was a sort of "saving which evinced a want of true preception of the "great object of all the labor that had preceded it. It
* " Talj*, or the Chronicles of • Clay Faro."