[Illustration:  Fig. 183.  Framework of the Cave.]

[Illustration:  Fig. 184.  The Siding and Flooring.]

The sides were now boarded up with upright slabs nailed to the stringpieces.  An opening 3 feet 6 inches high was left in the forward wall for a passageway.  Several slabs were now placed on the edge across the bottom of the cave, to serve as floor beams, upon which a flooring of slabs was laid.  Next the rafters were set in place, one on each upright slab.  Slots were cut in the ends of the uprights to receive the rafters, which were slabs placed on edge.  As the forward uprights were 2 feet shorter than the rear ones, the rafters were given a good slant, so that the roof would properly shed any water that might soak in through the ground above.

[Illustration:  Fig. 185.  Notching in the Rafters.]

The roof was laid on the same way that we had made the roof of our tree house; that is, a slab was first nailed at the forward end of the rafters with its edge projecting far enough to make a good eave; then the second slab was nailed on, with its edge overlapping the first, and a third with its edge overlapping the second, and so on with the rest.  At the rear end of the roof a hole was cut, into which we fitted a piece of stovepipe.  We didn’t plan to have a fire in the house, but set the stovepipe in place to provide the necessary ventilation.  As the pipe had an elbow in it, there was no danger of rain or dirt falling through it.  The upper end of the stovepipe was concealed among some rocks at the top of the knoll.

A suitable flooring was now laid in the passageway, and the sides were boarded up to a height of 2 feet from the floor at the entrance to a height of 3 feet 6 inches at the inner end.  A roof of slabs was nailed on, and then we were ready to cover our slab house with dirt.

Covering the Cave.

We avoided piling on the dirt very deep, because there was danger of breaking in the roof with a heavy load.  A thin layer of sand covered with the top-soil brought up the level to about that of the rest of the knoll.  Then the sod was laid back in place and well watered, and the few bushes planted back in their original positions.  Our sodding should have been done in the spring for best results.  The frost soon killed the grass, and the bushes withered away.  But a few cents’ worth of grass seed was sowed in, and in time gave the knoll a very natural appearance.  A bush at the bottom concealed the entrance of the cave, so that no one who was not in the secret would have suspected that beneath that innocent looking knoll were gathered the members of the “Big Bug Club.”

The Big Bug Club.

[Illustration:  Fig.186.  A Section through the Completed Cave.]