ngitude on the chart, or be exactly parallel to
one, and will intersect the point from which you intend to depart. Then
stretch your string along the course you desire to steam. Where this
string cuts the compass card, will be the direction of your course.
Remember, however, that this will be the _true_ course to sail. In order
to convert this true course into your compass course, allow for
Variation and Deviation according to the rules already given you.

In case you know the exact amount of Variation and Deviation at the time
you lay down the course--and your course is not far--you can get your
compass course in one operation by setting the North point of your
protractor as far East or West of the meridian as the amount of your
compass error is. By then proceeding as before, the course indicated on
the compass card will be the compass course to sail. This method should
not be used where your course in one direction is long or where your
course is short but in two or more directions. The reason for this is
that in both cases, either your Variation or Deviation may change and
throw you off.

Practically all navigation in strange waters in sight of land and in all
waters out of sight of land depends upon the determination of angles.
The angle at which a lighthouse is seen from your ship will give you
much information that may be absolutely necessary for your safety. The
angular altitude of the sun, star or planet does the same. The very
heart of Navigation is based upon dealing with angles of all kinds. The
instrument, therefore, that measures these angles is the most important
of any used in Navigation and you must become thoroughly familiar with
it. It is the sextant or some member of the sextant family--such as the
quadrant, octant, etc. The sextant is the one most in use and so will be
described first.

Put in your Note-Book:

The sextant has the following parts: (Instructor points to each.)

1. Mirror
2. Telescope
3. Horizon Glass
4. Shade Glasses
5. Back Shade Glasses
6. Handle
7. Sliding Limb
8. Reading Glass
9. Tangent Screw
10. Arc

In getting angles of land-marks or buoys, the sextant is held by the
handle No. 6 in a horizontal position. The vernier arrow in the sliding
limb is set on zero. Now, suppose you wish to get the angular distance
between two lighthouses as seen from the bridge of your ship. (Draw
diagram.)

[Illustration]

Look at one lighthouse through the line of sight and true hori