horizontal distance is 100 feet, and the
slope is at an angle of 15 deg., the rise will be 17-633/1000 feet.

Table No. 2 shows the rise of the slope for 100 feet of its own length. If
the sloping line, (at an angle of 15 deg.,) is 100 feet long, it rises 25.882
feet.

TABLE No. 1.
DEG. FEET.
5 8.749
10 17.663
15 26.795
20 36.397
25 46.631
30 57.735
35 70.021
40 83.910
45 100.--
50 119.175
55 142.815
60 173.205
65 214.451
70 274.748
75 373.205
80 567.128
85 1143.01

TABLE No. 2
DEG. FEET.
5 8.716
10 17.365
15 25.882
20 34.202
25 42.262
30 50.--
35 57.358
40 64.279
45 70.711
50 76.604
55 81.915
60 86.602
65 90.631
70 93.969
75 96.593
80 98.481
85 99.619

With the maps before him, showing the surface features of the field, and
the position of the under-ground rock, the drainer will have to consider
the following points:

1. Where, and at what depth, shall the outlet be placed?

2. What shall be the location, the length and the depth of the main drain?

3. What subsidiary mains,--or collecting drains,--shall connect the minor
valleys with the main?

4. What may best be done to collect the water of large springs and carry
it away?

5. What provision is necessary to collect the water that flows over the
surface of out-cropping rock, or along springy lines on side hills or
under banks?

6. What should be the depth, the distance apart, the direction, and the
rate of _fall_, of the lateral drains?

7. What kind and sizes of tile should be used to form the conduits?

8. What provision should be made to prevent the obstruction of the drains,
by an accumulation of silt or sand, which may enter the tiles immediately
after they are laid, and before the earth becomes compacted about them;
and from the entrance of vermin?

1. The outlet should be at the lowest point of the boundary, unless, (for
some especial reason which does not exist in the case under consideration,
nor in any usual case,) it is necessary to seek some other than the
natural outfall; and it should be deep enough to take the water of the
main drain, and laid on a sufficient inclination for a free flow of the
water. It should, where sufficient fall can be obtained without too great
cost, deliver this water over a step of at least a few inches in height,
so that the action of the dra