caused by the boys or men
falling through, a fall of about twenty and one half feet according to the
last measurements given for the frame.

An observatory of this kind will add greatly to the interest of a mountain
home or seaside home; it is a practical tower for military men to be used
in flag signalling and for improvised wireless; it is also a practical
tower for a lookout in the game fields and a delight to the Boy Scouts.

XVI

TREE-TOP HOUSES

BY the natural process of evolution we have now arrived at the tree-top
house. It is interesting to the writer to see the popularity of this style
of an outdoor building, for, while he cannot lay claim to originating it,
he was the first to publish the working drawings of a tree-house. These
plans first appeared in _Harper's Round Table_; afterward he made others
for the _Ladies' Home Journal_ and later published them in "The Jack of
All Trades."

Having occasion to travel across the continent shortly after the first
plans were published, he was amused to see all along the route, here and
there in back-yard fruit-trees, shade-trees, and in forest-trees, queer
little shanties built by the boys, high up among the boughs.

In order to build a house one must make one's plans _to fit the tree_. If
it is to be a one-tree house, spike on the trunk two quartered pieces of
small log one on each side of the trunk (Figs. 91 and 92). Across these
lay a couple of poles and nail them to the trunk of the tree (Fig. 91);
then at right angles to these lay another pair of poles, as shown in the
right-hand diagram (Fig. 91). Nail these securely in place and support the
ends of the four poles by braces nailed to the trunk of the tree below.
The four cross-sills will then (Fig. 95) serve as a foundation upon which
to begin your work. Other joists can now be laid across these first and
supported by braces running diagonally down to the trunk of the tree, as
shown in Fig. 95. After the floor is laid over the joist any form of
shack, from a rude, open shed to a picturesque thatch-roofed cottage, may
be erected upon it. It is well to support the two middle rafters of your
roof by quartered pieces of logs, as the middle rafters are supported in
Fig. 95; by quartered logs shown in Fig. 92.

Fig. 91. Fig. 92. Fig. 93. Fig. 94. Fig. 95. Fig. 96. Fig. 97.

[Illustration: Details of tree-top houses.]

If the house is a two-tree house, run your cross-sill sticks from trunk to
trunk, as