(called knots) are pieces of fish line running through the strands of
the reel line to the number of two, three, four, etc. A piece of white
bunting marks every two-tenths of a knot. This is because the run of the
ship is recorded in knots and tenths. The knots of fish line are 47 feet
4 inches from each other.

The log glass measures 28 seconds in time. For high rates of speed, a 14
second glass is used. Then the number of knots shown by the log line
must be doubled. The principle of the chip log is that each division of
the log line bears the same ratio to a nautical mile that the log glass
does to the hour. In other words, if 10 knots or divisions of the log
line run out while the 28 second glass empties itself, the ship's speed
is 10 knots per hour. If ten knots or divisions run out while the 14
second glass empties itself, the ship's speed is 20 knots per hour.

The patent or towing log consists of a dial, line and rotator. The large
circle of the dial records the knots and the small circle tenths of
knots. When changing course, read the log and enter it in the log book.
When changing course again, read the log again. The difference between
the two readings will be the distance run.

Both logs are liable to error. A following sea makes them under-rate, a
head sea over-rate. With both logs you must allow for currents. If a
current is against you--and you know its rate--you must deduct its rate
from that recorded in the log and vice versa. The reason for this is
that your log measures your speed through the water. What you must find
is your actual distance made good over the earth's surface.

Put in your Note-Book:

Between Sandy Hook and Fort Hamilton, bound due North, speed by chip-log
was 10 knots, tidal current setting North 2 knots per hour; what did the
ship make per hour? Answer: 12 knots.

At sea in North Sea ship heading S x W, patent log bet. 8 A.M. and 12 M.
registered 32 miles, current running N x E 2 knots per hour; what was
the actual distance made good? Answer: 24 miles.

Directions for allowing for a current setting diagonally across a ship's
course will be given in the proper place.

Assign for Night Work the following articles in Bowditch: Arts.
161-162-163-164-165.

THURSDAY LECTURE

THE CHART

_Aids to Navigation_

A chart is a map of an ocean, bay, sound or other navigable water. It
shows the character of the coast, heights of mountains, depths at low
water, direction and