cted horizon form one
unbroken line. Clamp the limb and read the angle. This is the IE. If the
vernier zero is to the left of the zero on the arc, the IE is minus and
it is to be subtracted from any angle you read, to get the correct
angle. If the vernier zero is to the right of the zero on the arc, the
IE is plus and is to be added to any angle you read to get the correct
angle. Index error is expressed thus: IE + 2' 30" or IE - 2' 30".

Quadrants, octants and quintants work on exactly the same principles as
the sextant, except that the divisions on the arc and the vernier differ
in number from the sixth divisions on the arc and vernier of the
sextant.

If any time is left, spend it in marking courses with the protractor and
handling the sextant.

Assign for Night Work the following Arts. in Bowditch:
134-135-136-138-142-144-145-151-152-157-158-159-160-161-162-163.

SATURDAY LECTURE

FIXES, ANGLES BY BEARINGS AND SEXTANT

There are five good ways of fixing your position (obtaining a "fix," as
it is called) providing you are within sight of landmarks which you can
identify or in comparatively shoal water.

Put in your Note-Book:

1. Cross bearings of two known objects.

2. Bearing and distance of a known object, the height of which is known.

3. Two bearings of a known object separated by an interval of time, with
a run during that interval.

4. Sextant angles between three known objects.

5. Using the compass, log and lead in a fog or in unfamiliar waters.

1. Cross bearings of two known objects.

Select two objects marked on the chart, so far apart that each will bear
about 45 deg. off your bow but in opposite directions. These bearings will
be secured in the best way by the use of your pelorus. Correct each
bearing for Variation and Deviation so that it will be a true bearing.
Then with the parallel rulers carry the bearing of one object from the
chart compass card until you can intersect the object itself and draw a
line through it. Do exactly the same with the other object. Where the
two lines intersect, will be the position of the ship at the time the
bearings were taken.

[Illustration]

Now supposing you wish to find the latitude and longitude of that
position of the ship. For the latitude, measure the distance of the
place from the nearest parallel with the dividers. Take the dividers to
the latitude scale at the side of the chart and put one point of them on
the same parallel. Wh