tions with the drains in process of construction, will be obvious. When the drains are all completed it may be necessary to find a particular drain, in case of obstruction, or for other reasons, and the map will then be found a great convenience and a saving of labor.

Locating Drains and Making the Map.-There are two methods of locating the drains and plotting them on the map, each of which has its advantages. An engineer, to secure accuracy and conformity to a definite plan in all parts of the work, would make a topographical survey of the area to be drained, by taking levels at frequent and regular intervals over the field, which would be represented on the map by contour lines, or lines of equal elevation, to indicate the shape of the surface. These would serve as guides in locating the drains so that they would run directly down the slope, or perpendicular to the contour lines, and the depth and rate of fall would be marked on the line of each drain. The entire system of drainage would, therefore, be first laid down on the map, and the drains in the field would be staked out from this record, as the work of construction was carried on. There are cases, perhaps, in which the expense involved in this method would be saved in economy of construction, if the engineer making the surveys was an expert in land draining.

Farmers who lay out the drains on their own farms, and carry on the work of construction as labor can be spared for the purpose, will, however, prefer a simpler and less expensive method, which answers quite as well, if a reasonable degree of intelligence or common sense is exercised in its application. Instead of making a plan on paper to serve as a guide in the field, the drains will be first staked out in the field from time to time, as required in the progress of the work, and they can then. be plotted on a map with sufficient accuracy to serve all practical purposes of a convenient and permanent record,

without making use of any expensive surveying or engineering instruments.

All that is absolutely required in the field work is the means of accurately measuring the lines of drains, and their distance from certain land marks. A surveyor's chain, or tape, will be found convenient, but in their absence a rod pole, divided in feet and inches, will serve the purpose of providing the data for making a record of the work on the map. The cheap measuring tapes in common use should be discarded, as they are not always accurate, and if wet they are liable to stretch and vary in length, and the results obtained with them are often misleading.

When the surface of the field is undulating there will be no difficulty, in most cases, in deciding upon the location and course of the proposed drains by the eye alone, without taking levels with an instrument, but the precaution should always be taken when the fall is slight, to look over the proposed line from both ends of it before deciding upon its exact location, as appearances are sometimes deceitful if we look in one direction only. A farmer who is familiar with his fields, and observes the direction water flows over the surface in the spring, will seldom hesitate in regard to the direction of the slope and the course of lines running directly down hill. In cases of doubt as to the fall, on land that is nearly level, a simple and convenient method of determining the slope, or grade, of the drain, will be given in the chapter on construction.

Writers on draining have, with few exceptions, given directions for digging and finishing the ditches throughout their entire length before any tiles are laid, and when this is done, directions are given to lay the first tiles at the upper end of the drain and continue the work towards the outlet. This method is, however, impracticable, if there is water running in the ditch, or

if quicksand is found anywhere in its course, and in all cases better work can be done by beginning at the outlet to lay the tiles, and the ditch should only be finished as the tiles are laid. The main drain should always be laid first, to furnish an outlet for the discharge of water that may be running in the ditches in the progress of the work of construction.

In laying out and mapping the drains, attention will, therefore, be first directed to the main, and the laterals, or branches, will then follow in the order of their importance. Having placed stakes in the field to mark the line of the main drain, its place on the map may be determined, as follows. To facilitate the description of the different steps in the process, let us suppose a case in which the main drain crosses the north line of the field at, or near, the outlet.

Set a stake marked A at the point where the drain crosses or intersects the north line of the field, and determine its position by measuring on the boundary line of the field, in either direction, as may be most convenient, to the corner of the field, or to some permanent object, and make a record of this distance and position of the stake on the map, which should, of course, be drawn to a definite scale. Then set a stake marked B at the upper end of the proposed drain, or at the point where a change in direction will be necessary. Measure the distance from A to B, and to determine the exact course take the range of the two stakes, and ascertain where the line between them would, if continued, strike the opposite side of the field, and drive a stake marked b to mark the place. The position of b can now be determined by its distance from the corner of the field, or some permanent object, measured on the south line of the field, as was done to fix the point A on the north line. The drain A-B can now be plotted on the map by marking the point A on the north boundary of the

field, and the point b on the south boundary, and a rule touching the two points will give the course and position of the drain. The point B is then fixed by laying off the proper distance from A on this line.

If the main drain is now to be continued in a different direction, place a stake Cat the end of the next course, ascertain where the line B-C, if continued, would intersect the boundary of the field, by taking the range of the two stakes, and mark the place with a stake c, the position of which is determined by its distance from b, or from any other known point, as in fixing the position of A and b. In plotting, place the rule on the map touching the points B and c, and measure on the line indicated the proper distance from B to C.

To locate the laterals proceed in the same way, taking as the starting point their junction with the main drain. If, for example, they are branches of the drain A-B, fix the point of junction by measuring the distance from A, or, if on the line B-C, determine the distance of the starting point from B. The laterals are then plotted on the map, by measuring their length from the main, and fixing their course, by ascertaining the point at which the line, if continued, would intersect the boundary of the field, and proceed as before. If there are several parallel laterals, the course of one may be fixed as above, and this may be taken as a base line from which the others may be laid out or located.

The whole process of locating and mapping the drains by this empirical method is so simple, that any one of average intelligence should be able to perform the work without any technical knowledge of surveying or engineering; and if the measurements are accurately made and the figures representing distances are entered on the map in their proper place, the record will be sufficiently accurate, even if the greatest exactness is not secured in drafting the lines on the map. A con

venient scale for the map is fifty feet to the inch, but a scale of one hundred feet to the inch will give satisfactory results when there are but few drains to be recorded. As the drains are all located and staked out in the field, the map may consist simply of an outline of the field drawn to a definite scale, on which the lines of drains, as decided upon, may be drawn, with figures representing all distances, and letters or numbers to indicate each particular drain.

CHAPTER VIII.

QUALITY AND SIZE OF TILES.

There are a number of particulars in regard to the selection of tiles, that should receive careful attention, as the best for the purpose are the cheapest, if the draining of land is made, as it should be, a permanent improvement.

Round Tiles.--In describing the different kinds of tiles the conclusion was reached that round tiles should be exclusively used, as they have none of the defects of other forms, and it may be well to notice more particularly some of their most important advantages. When but little water is running in a drain of round tiles, it is confined to a narrow channel, and the force of the current is thereby increased, so that obstructions from silt are not likely to occur. The ends of the tiles vary but little from a right angle to the axis, and closefitting joints can be secured in laying them, by turning them in their bed, if necessary, as it is a matter of indifference which side of the cylinder is up. When laid in the groove prepared for them by a draining scoop of proper size, they are not liable to be displaced by firmly