llow. The
courses to sail and the distance between each course are easily
ascertained from the information on the chart. This is the way it is
done:

(Note to Instructor: Provide yourself with a chart and explain from the
chart explanation just how these courses are laid down.)

Spend the rest of the time in having pupils lay down courses on the
different kinds of charts. If these charts are not available assign for
night work the following articles in Bowditch, part of which reading can
be done immediately in the class room--so that as much time as possible
can be given to the reading on Dead Reckoning:
167-168-169-172-173-174-175-176--first two sentences
178-202-203-204-205-206-207-208.

Note to pupils: In reading articles 167-178, disregard the formulae and
the examples worked out by logarithms. Just try to get a clear idea of
the different sailings mentioned and the theory of Dead Reckoning in
Arts. 202-209.

WEDNESDAY LECTURE

USEFUL TABLES--PLANE AND TRAVERSE SAILING

The whole subject of Navigation is divided into two parts, i.e., finding
your position by what is called Dead Reckoning and finding your position
by observation of celestial bodies such as the sun, stars, planets, etc.

To find your position by dead reckoning, you go on the theory that small
sections of the earth are flat. The whole affair then simply resolves
itself into solving the length of right-angled triangles except, of
course, when you are going due East and West or due North and South. For
instance, any courses you sail like these will be the hypotenuses of a
series of right-angled triangles. The problem you have to solve is,
having left a point on land, the latitude and longitude of which you
know, and sailed so many miles in a certain direction, in what latitude
and longitude have you arrived?

[Illustration]

If you sail due North or South, the problem is merely one of arithmetic.
Suppose your position at noon today is Latitude 39 deg. 15' N, Longitude 40 deg.
W, and up to noon tomorrow you steam due North 300 miles. Now you have
already learned that a minute of latitude is always equal to a nautical
mile. Hence, you have sailed 300 minutes of latitude or 5 deg.. This 5 deg. is
called difference of latitude, and as you are in North latitude and
going North, the difference of latitude, 5 deg., should be added to the
latitude left, making your new position 44 deg. 15' N and your Longitude the
same 40 deg. W, since you ha