ied over to the cliff. Then we carried them on our backs,
three or four at a time, up the slanting hillside to the first ledge.
From there up, owing to the steepness of the ascent, we had to employ
different tactics.

THE DERRICK.

[Illustration: Fig. 137. The Derrick in Use.]

A derrick was constructed of two sticks 10 feet long, which were bolted
together at the top, and secured about five feet apart at the bottom by
a cross piece, as shown in Fig. 136. The derrick was then taken apart
and with some difficulty hauled piecemeal up to the next ledge above.
Here it was put together again. The fall and tackle used in our aerial
railway was attached to the apex of the derrick, and the latter was then
erected with the legs set into depressions in the ledge and the upper
ends slanting outward but kept from falling over the edge by a rope tied
to one of the fixed rungs set in the fissure. With this derrick we
hoisted up the boards in a few hauls. The job was a very ticklish one,
but Bill used the greatest care to prevent accident. The derrick, rope
and tackle were carefully tested before used, and as soon as the load
was attached to the lower pulley block the two who did the loading were
instructed to crawl back into the fissure so as to be out of danger in
case anything gave way. At one time a stick which had been carelessly
tied did fall, and it might have badly hurt some one had we not observed
this precaution. When we had raised the material to the second ledge we
transferred operations to the top ledge, and when the materials had been
hauled up to this point we finally rigged up our fall and tackle in the
old oak tree itself.

THE TREE HOUSE.

[Illustration: Fig. 138. Main Girder of the Tree House.]

[Illustration: Fig 139. Top View of the Platform.]

The tree had two large limbs which extended out at a wide angle from the
main trunk. Across these two limbs, at about seven feet out, we laid our
first girder, nailing it securely in place. Then to the main trunk we
nailed the second girder on a level with the first. Diagonal braces were
extended from the trunk to support the ends of this girder, and a tie
piece was nailed to the braces, as shown in Fig. 138, to prevent them
from spreading. The girders were rough sticks about 4 inches in diameter
and 10 feet long. We cut flat faces on them at the points where they
were nailed to the tree, and then, to make them doubly secured, we
nailed cleats, or blocks of wood