ts of the
ocean. The navigator knew not whither he was hurrying over the wild
waste of waters; but by observing the relative position of some of the
fixed stars to his course while sailing out to sea, he could form a
rough idea of the proper course to steer in order to return to the port
whence he had started.

The compass, then, shows the sailor the course he has been going, and
the _log_ (of which more presently) enables him to ascertain the rate at
which he has proceeded; while his chronometers, or time-keepers, tell
him the _time_ during which the course and rate of sailing have been
kept up. And many a long cruise on the unknown deep has been
successfully accomplished in days of old by bold seamen, with this
method of dead-reckoning; and many a mariner at the present day depends
almost entirely on it, while _all_ are, during thick, stormy weather,
dependent on it for days and sometimes weeks together.

The _log_, to which we have referred, is the instrument by which is
determined the rate at which a ship is progressing. It is a very simple
contrivance: a triangular piece of wood about the size of a large
saucer, with a piece of stout cord fastened to each corner, the ends of
the cords being tied together, so that when held up, the "log," as it is
called, resembles one of a pair of scales. One of the cords, however,
is only temporarily attached to its corner by means of a peg, which when
violently pulled comes out. One edge of the triangle is loaded with
lead. The whole machine is fastened to the "log-line,"--a stout cord
many fathoms long, which is wound on a large reel.

"Heaving the log," as we have said, takes place every hour. One sailor
stands by with a sand-glass which runs exactly half a minute. Another
holds the wooden reel; and a third heaves the log overboard, and "pays
out" line as fast as he can make the reel spin. The instant it is
thrown the first sailor turns the sand-glass. The log, being loaded on
one side, floats perpendicularly in the water, remaining stationary of
course; while the man who hove it watches sundry knots on the line as
they pass over the stern of the ship, each knot representing a mile of
rate of speed in the hour. As the last grain of sand drops to the
bottom of the glass the first sailor gives a sharp signal, and the
second clutches and checks the line, examines the knot nearest his hand,
and thus knows at once how many knots or miles the ship is sailing at
that tim