re, seek in
Table 2 for the page where the nearest agreement of Difference of
Latitude and Departure can be found. The number of degrees at the top or
bottom of the page (according as to whether the Diff. of Lat. or Dep. is
greater) will give you the true course made good, and the number in the
distance column opposite the proper Difference of Latitude and Departure
will give you the distance made.

It is often convenient to use the reverse of the above method, i.e.,
being given the latitude and longitude of the position left and the
latitude and longitude of the position arrived in, to find the course
and distance between them by Middle Latitude Sailing. The full rule is
as follows:

1. Find the algebraic difference between the latitudes and longitudes
respectively.

2. Using the middle (or average) latitude as a course, find in Table 2
of Bowditch the Diff. of Lo. in the distance column. Opposite, in the
Diff. of Lat. column, will be the correct Departure.

3. With the Diff. of Lat. between the position left and the position
arrived in, and the Departure, just secured, seek in Table 2 for the
page where the nearest agreement to these values can be found. On this
page will be secured the true course and distance made, as explained in
the preceding method.

4. Use this method only when steaming approximately an East and West
course.

For an example of this method, see Bowditch, p. 77, example 3.

THURSDAY LECTURE

EXAMPLES ON PLANE AND TRAVERSE SAILING (_Continued_)

1. Departure taken from Cape Horn. Lat. 55 deg. 58' 41" S, Lo. 67 deg. 16' 15"
W, bearing by compass SSW 20 knots. Ship heading SW x S, Deviation 4 deg. E,
steamed the following courses:

---------+----------+------------+-----------+----------
C. Cos. | Wind | Leeway | Deviation | Distance
---------+----------+------------+-----------+----------
SW x S | SE | 1 pt. | 4 deg. E | 40
WNW | N | 2 pts. | 5 deg. E | 25
S 40 deg. E | NE | 2 pts. | 4 deg. W | 20
---------+----------+------------+-----------+----------

_Remarks_

Variation 18 deg. E throughout. Current set NW magnetic 30 mi. for the day.
Required Latitude and Longitude in and course and distance made good.

2. Departure taken from St. Agnes Lighthouse, Scilly Islands, Lat. 49 deg.
53' S, Lo. 6 deg. 20' W, bearing by compass E x S, distance 18 knots,
Deviation 10 deg. W, Variation 23 deg