had the foundation dug. He wrote the author a long
letter complaining of the hard work; at the same time the author was
receiving letters from _boys_ telling how much fun they had in building
and finishing their underground houses.

Caves

Ever since "Robinson Crusoe" and "Swiss Family Robinson" were written cave
houses have been particularly attractive to boys; no doubt they were just
as attractive before these books were written, and that may be the reason
the books themselves are so popular; at any rate, when the author was a
small boy he was always searching for natural caves, or trying to dig them
for himself, and so were all of his companions. One of the most charming
features of the "Tom Sawyer" and "Huckleberry Finn" stories is that part
connected with the cave.

Fig. 155. Fig. 156. Fig. 157. Fig. 157.A. Fig. 157.B. Fig. 157.C.

Fig. 158. Fig. 159. Fig. 160. Fig. 161.

[Illustration: The original American boy's hogan or underground house.]

Dangerous Caves

The trouble is that with caves which the boys dig for themselves there is
always serious danger of the roof falling in and smothering the young
troglodytes, but a properly built underground hogan is perfectly safe from
such accidents.

Framing

After you have levelled off the foundation erect the rear posts of
two-by-fours _A_, _B_ and _C_, _D_ (Fig. 156). These posts should be of
the same height and tall enough to allow the roof to slant toward the
front as in Fig. 155. The front posts _E_, _F_ and _G_, _H_, although
shorter than the back posts, should be tall enough to allow headroom. One,
two, or three more posts may be erected between the post _A_, _B_ and the
post _C_, _D_ if additional strength is required. The same is true of the
sides, and in place of having only one post in the middle of each side
(_M_, _N_ and _O_, _P_, Fig. 156), there may be two or three posts, all
according to the size of the house you are building; the main point is to
make _a compact and strong box_ of your framework so that in the wet
weather the banks surrounding it will not be tempted to push in the sides
and spoil your house.

Decaying Wood

Locust, chestnut, and cedar will last longer than other varieties of wood
when exposed to contact with damp earth, but common wood, which rots
easily, may be protected by preservatives, one of which is boiled
linseed-oil with pulverized charcoal stirred into it until a black paint
is produced. Some people say that