ce
where the chain of soundings are the same on the same course you are
steaming. This is the only method by soundings that you can use in thick
weather and it is an invaluable one.

Put in your Note-Book this diagram:

10 \ 8.30A.M. |
12 \ 9.00A.M. |
13 \ 10A.M. |
13-1/2 \ 10.30A.M. |
14 \ 11A.M. |
14-3/4 \ 11.30A.M. |

Assign for Night Work, Review for Weekly Examination to be held on
Monday.

Add an explanation of the Deviation Card in Bowditch, page 41.

Put in your Note-Book:

Entering New York Harbor, ship heading W 3/4 N, Variation 9 deg. W. Observed
by pelorus the following objects:

Buoy No. 1--ENE 1/4 E
" " 2--E 1/2 N
" " 3--NE 1/4 E
" " 4--NW 1/4 N

Required true bearings of objects observed.

Answer:

From Deviation Card in Bowditch, p. 41, Deviation on W 3/4 N course is 5 deg.
E. Hence, Compass Error is 5 deg. E (Dev.) + 9 deg. W (Var.) = 4 deg. W.

C. B. C. E. T. B.
ENE 1/4 E 70 deg. 4 deg. W 66 deg.
E 1/2 N 84 deg. 4 deg. W 80 deg.
NE 1/4 E 48 deg. 4 deg. W 44 deg.
NW 1/4 N 318 deg. 4 deg. W 314 deg.

WEEK II--DEAD RECKONING

TUESDAY LECTURE

LATITUDE AND LONGITUDE

[Illustration]

We have been using the words Latitude and Longitude a good deal since
this course began. Let us see just what the words mean. Before doing
that, there are a few facts to keep in mind about the earth itself. The
earth is a spheroid slightly flattened at the poles. The axis of the
earth is a line running through the center of the earth and intersecting
the surface of the earth at the poles. The equator is the great circle,
formed by the intersection of the earth's surface with a plane
perpendicular to the earth's axis and equidistant from the poles. Every
point on the equator is, therefore, 90 deg. from each pole.

Meridians are great circles formed by the intersection with the earth's
surface of planes perpendicular to the equator.

Parallels of latitude are small circles parallel to the equator.

The Latitude of a place on the surface of the earth is the arc of the
meridian intercepted between the equator and that place. It is measured
by the angle running from the equator to the center of the earth and
back through the place in question. Latitude is reckoned from the
equator (0 deg.) to the North Pole (90 deg.) and from the equator (