CT 1h--25m--45s
WT 4h--13m--25s

(+12 hrs.) CT 13h--25m--45s
WT 4 --13 --25
----------------
C-W 9h--12m--20s

WT 6h--13m--25s
+ C-W 9 --12 --20
----------------
15h--25m--45s
(-12 hrs.) 12
----------------
CT 3h--25m--45s

There is one more very important fact to know about the chronometer. It
is physically impossible to keep it absolutely accurate over a long
period of time. Instead of continually fussing with its adjustment and
hands, the daily rate of error is ascertained, and from this the exact
time for any given day. It is an invariable practice among good mariners
to _leave the chronometer alone_. When you are in port, you can find out
from a time ball or from some chronometer maker what your error is. With
this in mind, you can apply the new correction from day to day. Here is
an example (Put in your Note-Book):

On June 1st, CT 7h--20m--15s, CC 2m--40s fast. On June 16th, (same CT)
CC 1m--30s fast. What was the corresponding G.M.T. on June 10th?

June 1st 2m--40s fast
16th 1m--30s fast
----------------
1m--10s
60
--
60
10
--
15) 70s (4.6 sec. Daily Rate of error losing

June 1st-10th, 9 days times 4.6 sec. = 41 sec. losing
June 1st 2m--40s fast
June 10th 41s losing
---------
June 10th 1m--59s fast

CT 7h--20m--15s
CC -- 1 --59
------------
G.M.T. 7h--18m--16s on June 10th

If CC is fast, subtract from CT
If CC is slow, add to CT

WEEK III--CELESTIAL NAVIGATION

TUESDAY LECTURE

CELESTIAL CO-ORDINATES, EQUINOCTIAL SYSTEM, ETC.

We have already discussed the way in which the earth is divided so as to
aid us in finding our position at sea, i.e., with an equator, parallels
of latitude, meridians of longitude starting at the Greenwich meridian,
etc. We now take up the way in which the celestial sphere is
correspondingly divided and also simple explanations of some of the more
important terms used in Celestial Navigation.

As you stand on any point of the earth and look up, the heavenly bodies
appear as though they were situated upon the surface of a vast hollow
sphere, of which your eye is the center. O