rs how to build this bridge, as it
required the utmost care, and had to be built just so to avoid disaster.
Bridge building is a serious business, and I would not advise any one to
attempt building this, of all bridges, who does not propose to follow
instructions implicitly. Uncle Ed told us that if we built it properly,
and with sound timbers, we would find the bridge strong enough to
support a dozen boys, but he warned us not to crowd more than that
number on it.

FRAMES FOR THE CANTILEVER BRIDGE.

[Illustration: Fig. 305. A Frame (make four).]

[Illustration: Fig. 306. B Frame (make four).]

[Illustration: Fig. 307. C Frame (make four).]

[Illustration: Fig. 308. D Frame (make four).]

The frames with which the cantilever bridge was built were made of
saplings from 3 to 4 inches in diameter. We procured them from Mr.
Schreiner's lands up the river. In making the frames the sticks were
fastened together with 1/2-inch bolts 6 inches long. It was quite a
strain on our pocketbooks to buy these bolts, but Uncle Ed had written
that nails or spikes would be useless to stand the strains of so large
a bridge, and that if we could not get any bolts we had better give
up the idea of building a cantilever bridge. To make sure that we
made no mistakes, Uncle Ed had made a drawing of each different
size of frame we would need, designating each with a different
letter, and then these same letters were marked on a general
view of the bridge, so that we would know exactly where the
frames belonged. These drawings are reproduced here in Figs. 305
to 316 and 318. We had to make four frames each, of the _A_, _B_,
_C_ and _E_ sizes, two each of the _F_, _G_ and _L_ sizes and
one each of the _H_, _I_, _J_ and _K_ sizes. Of the _D_ frames
two were made with the ends cut away on the outer half, as illustrated
in Fig. 308, and two were cut away at the inner side, the reason for
which will appear presently. When fastening the timbers together we cut
notches in each stick, as shown in Fig. 317. The depth of each notch was
just one-quarter the diameter of the stick; that is, the notch was 3/4
of an inch deep in a 3-inch stick and 1 inch deep in a 4-inch stick.
Care was taken not to exceed this depth, for fear of weakening the
sticks. In the case of frame _D_, the sticks were not notched or
mortised together. It will be noticed that the measurements are given to
the inner edges of the sticks in some cases, and to the outer edges in
oth