above the
ground level. If a tree had been in line with the drain line this might
have been used and saved driving the stakes. Across the stake, at right
angles to it, a board with a perfectly straight edge was nailed. This
board was about four feet long, one end pointed at the drain line. At
the other end Jay placed his eye looking across this to where Albert had
driven stakes.

One stake had been driven into the ground at the beginning where the
drain was to be dug; another at the extreme end or outlet of the drain.
Albert stood at the first stake and ran a little piece of paper slowly
up and down the stake until Jay raised his hand. This meant that the
paper was on the same line with the sighting board. Then Albert ran to
the other stake and did the same. The difference in these two points
gives the difference in level of the ground. Albert measured from the
ground to his mark on the first stake, and, doing the same in the case
of the other stake, found the difference to be eight inches. This was
too great a drop. Then the boys drove two stakes in between these others
and did the same work of level finding. From stake 1 to 2, or for the
first twenty-five feet there was no difference in level. For the first
fifty feet there was four inches drop; for the next twenty-five feet,
five inches rise; and the last twenty-five feet, six inches drop. They
marked all this on the stakes in order to make sure they got the level
right. The bed must, you see, drop one inch for every twenty-five feet.
For the first fifty feet of the line the drop was just twice too much;
then came the abrupt rise and drop.

Albert ploughed a furrow straight along the line and ploughed back
again. Then he reploughed. The boys then began to dig, making a ditch
three feet deep right through the land. In order to get the right level
they used a home-made device and plumb-line which can be made as
follows: Nail the ends of two six-inch boards ten feet long, so as to
make a right angle; then across the open end of the triangle, nail
another six-inch board having the lower edge about a foot from the ends
of the boards. Cut off the ends of the boards on a level, so that they
will rest evenly on the ground. Next drive a nail into the apex of the
triangle, and to it tie a line long enough so that when the triangle is
stood on its legs, the plumb-bob, which you will tie on the other end of
it, will almost reach the ground.

The centre must next be determine