PRACTICAL NOTES ON UNDERDRAINING. 587 
to the water-course of the drain, and will wash mellow earth down between the stones, 
thus obstructing the flow of the water in its proper channel. 
. It is always desirable, so far as may be practicable, to make the water-course of a 
drain only equal to the fullest capacity of the stream at any time. In many ditches, 
tiles having a bore of one and a half or two inches in diameter, will carry all the water 
that the drain will ever draw. In such places small tiles would be preferable to ethers 
twice as large, as a smal] passage, carrying a stream about equal to its capacity, will 
be kept ‘clear longer than one much larger. Economy may be exercised, in many 
places, by laying tiles of the smallest size, say one-inch tiles, at the upper end of the 
ditch, for a distance of several rods; then, for another distance, lay one and a half inch 
tiles; then, as the capacity of the stream increases, use two-inch tiles, increasing to 
three-inch, four-inch, five-inch, at given sections of the distance. In many instances a 
stone drain or plank drain is made through a field as the main drain, or four-inch tiles 
are employed, into which not a few branches, some short and others long, empty their 
water. In many such branches one to two inch tiles would serve the purpose of 
four-inch tiles. 
The size and form of the stones to be used in filling a drain must be taken into con- 
sideration when cutting the ditch. If the side stones are about six inches in diameter, . 
and the stream seldom fills a four-inch tile, the bottom of the ditch shouid be made 
fourteen inches wide, which will give a water-course four inches up and down, and 
two inches wide. If the ditch be made of the size indicated, the same kind of stones 
may be used for covering the water-course that are employed in the side. It is im- 
portant that the width of a ditch should conform to the size and shape of the stones. 
Draining large marshes.—The first. consideration in draining a marsh is to determine 
the source of the water. If the water backs up and overflows from a river, lake, or 
other body, the construction of a dike should be the first step. If the surplus water 
flows down from the uplands, or issues from springs near the foot of a slope, spreading 
over the surface of the low ground, a deep drain should’ be made between the slope of 
the marsh, called a “catch-water drain,” for the purpose of receiving the water as it 
spreads along on the surface or through the soil at a period of high water. A good 
drain in the right place, near the source of surplus water, will often be more effectual 
in draining the soil than four times the length of drain made directly through the 
marsh. Marshes are always supplied with surplus water from a source higher than 
the surface. In many instances a small stream flows directly through the marsh dur- 
ing the greater part of the growing season, and at periods of high water the stream 
will be so large that the water cannot be conveyed in an underdrain. _ In such a case 
the first step will be to cut a broad, open ditch through ‘the middle. This should be 
done when there is little or no water. In some instances laborers must do the first ex- 
cavating in mud and water ankle deep. In case the natural course of a stream lies 
directly across a field, an open ditch, to carry the flood water, may often be made more 
conveuieutly on one side of the swamp, which will sometimes serve the double pur- 
pose of an open ditch and a main drain, into which branches may empty. If, for in- 
stance, as is frequently the case, a spring issues from one side of a swamp, so that the 
water spreads over the surface of a broad area, ascertain and stake out the most con- 
venient place for a deep underdraiy, to extend from the. spring to some river, and let 
the water be all collected at the head of a ditch before any portion of it is allowed to 
spread over the low ground. One good drain will sometimes be sufficient to relieve 
several acres of all surplus water. 
In many instances swampy depressions are found on table-land having no natural out- 
let of sufficient depth to draw off all the water, even in the driest month of the year. 
The source of the water in such “ pond-holes” or “cat-holes,” as they are sometimes 
denominated, can be found in no particular place, but it soaks in on every side. The 
proper way to render such places dry is to sink a deep ditch entirely around the outer 
edge, a rod or more distant from the lagh-water mark. Of course the distance of the ditch 
from theedye of the swamp will depend on the slope of the land, In case the land is dry 
enough to be plowed and cultivated close to high-water mark, let the ditch be made 
only a few feet from that point. On the contrary, if the partially dry land near the 
swamp is only a few inches higher than the level with high-water mark, and wild, 
coarse grass appears over the surface for a distance of several rods from the swamp, let 
the ditch be sunk a few feet beyond everything that indicates wet land. Such ditches 
should be made not less than thiee feet deep, having a good outlet, so that water from 
the farthest side will flow away as readily as from the side nearer the outlet. Fig. 2 
furnishes a more correct idea of the true manner, of draining “cat-holes” and frog- 
pouds on table-land, The irregular line W indicates high-water mark. The dotted 
line L represents tho extreme point occupied by wild and coarse grass and aquatic 
plants. AtOis the ontletofa tiledrain, where it may be necessary tosink the main ditch 
four or five feet deep in order to secure a true descent from T to O on both sides of the 
wet ground. It isa rare occurrence that a cat-hole is not thoroughly drained when 
tiles are laid entirely around the outside,as indicated. The grand difficulty in many 
instances is that the ditch is sunk on one or both sides of the wet ground deeper than 
