of the glasses, leaving my hands free for the purpose of swimming. (See
also, under "Fishing;' 'To see Things deep under Water.')

RAFTS AND BOATS.

Rafts.--Rafts of Wood.--Rafts are made of logs of wood, held together by
pairs of cross-bars, one of each pair lying above the raft and the other
below; then, the whole may be made quite firm by a little judicious
notching wherethe logs cross, and a few pegs and lashings. Briers,
woodbines, etc., will do for these. If the logs are large, they should be
separately launched into the river, and towed into their proper places.
Outriggers vastly increase the stability of a raft. The raft-fastening in
common use is shown in f. 1: it is a stout, little wand, bent over the
cross piece, and wedged into holes in the framework.

[Sketch of raft].

[Fig 1 and Fig 2 show fastening arrangements].

The rafts of European rivers are usually built on shore, and launched
into the water: three slides are laid for the purpose, on the sloping
bank of the river; upon these are laid the four poles, secured together
by their ends, which are to form the framework of the raft (fig. 2).
Other poles are put in between, until the whole is complete.

Bamboo rafts.--Where bamboo is plentiful, it is preferable to any other
material for rafts. A few bamboos lashed into the shape of an ordinary
field gate, but with two diagonals, and with handfuls of grass thrown on
to make a platform, is very buoyant and serviceable.

Floating power of various Woods.--The floating power of a raft depends on
the buoyancy of the wood of which it is made. I give, in a Table (p. 90),
a list of the specific gravities of a few well-known woods; and have
annexed to them a column of what may be called their "specific floating
powers."*

[Footnote] *Specific floating power = (1/Spec. Gr.)--1. (Mem., the Table
of these, in previous editions is incorrect.) Burden = weight of raft x
specific floating power. Weight of wood required to support a given burden =
Burden x (Spec. Gr./1-Spec. Gr.); the last column gives the latter
factor.

Hence, to find the actual floating power of a raft, it is simply
necessary to multiply its weight into the specific floating power of the
wood of which it is made.

Thus, a raft of 12 logs of larch, averaging 30 lbs. each, weighs 360
lbs.; this multiplied by .47, is equal to 169 lbs. very nearly, which is
the weight the raft will support without sinking. Poplar is the lightest
on the list