n
". There are 60" in each minute. Four degrees, ten minutes and thirty
seconds would be written thus: 4 deg. 10' 30".

Although this guide just given you is given as an aid to quickly
transfer a point course into a new or old compass course--or vice
versa--you should learn to do this yourself, after awhile, without the
guide.

Put in your Note-Book:

--------------+-----------+------------+--------------
Ship's Head | New | Old | By Point
--------------+-----------+------------+--------------
NE | 45 deg. | N 45 deg. E | NE
90 deg. | 90 deg. | N 90 deg. E | EAST
SE x E | 123 deg. 45' | S 56 deg. E | SE x E
S 20 deg. E | 160 deg. | S 20 deg. E | S x E 3/4 E
S 2 pts. E | 157 deg. 30' | S 22 deg. 30' E| SSE
NW 3/4 W | 306 deg. 34' | N 53 deg. W | NW 3/4 W
289 deg. 41' | 289 deg. 41' | N 70 deg. W | WNW 1/4 W
--------------+-----------+------------+--------------

I will show you just how each one of these courses is secured from the
guide just given you.

Note to Instructor: After explaining these courses in detail, assign for
reading _in the class room_ the following articles in Bowditch: Arts.
25-26-27-28-29-30-31-32, 74-75-76-77-78-79-80-81-82.

Every compass, if correct, would have its needle point directly to the
real or _true_ North. But practically no compass with which you will
become familiar will be correct. It will have an error in it due to the
magnetism of the earth. This is called Variation. It will also have an
error in it due to the magnetism of the iron in the ship. This is called
Deviation. You are undoubtedly familiar with the fact that the earth is
a huge magnet and that the magnets in a compass are affected thereby. In
other words, the North and South magnetic poles, running through the
center of the earth, do not point true North and South. They point at an
angle either East or West of the North and South. The amount of this
angle in any one spot on the earth is the amount of Variation at that
spot. In navigating a ship you must take into account the amount of this
Variation. The amount of allowance to be made and the direction (i.e.
either East or West) in which it is to be applied are usually indicated
on the chart. On large charts, such as those of the North Atlantic, will
be found irregular lines running over the chart, and having beside them
such notations as 10 deg. W, 15 deg.