EXPLANATION OF TABLES. 
TABLE 1.—RADIO BEARING CONVERSION. 
This table is used to convert the radio or true bearing into the mercator bearing, when it is 
desired to plot the bearing on a mercator chart. The arguments used to find the correction are 
the middle latitude between the sending radio station and the vessel’s D. R. position, and the differ- 
ence of longitude between the radio station and the vessel. The sign of the correction is as follows, 
ezsunand of the station, the correction is paddies 
westward subtractive 
In south latitude, when the vessel is ESSERE of the station, the correction is subuaciiNes 
westward additive 
Should the bearing be observed from the vessel, the sign of the correction as given above is 
reversed. 
Exampie: A vessel in D. R. Lat. 38°03’ N.; Long. 55° W.; receives a radio bearing of 118° 
from Bar Harbor, Maine, radio station (Lat. 44°19’ N.; Long. 68°11’ W.). Find the Mercator 
bearing. 
Bar Harbor station, Lat. 44°19’ N.; Long. 68°11’ W. 
Vessel (D. R. position), Lat. 38°03’ N.; Long. 55°00’ W. 
Middle Lat. 41°11’ N.; Diff. Long. 13°11’ W. 
Enter table with Mid. Lat. 41° and Diff. Long. 13°.2; the correction is +4°.4. 
Mercator bearing= Radio bearing plus correction, or 118°-++4°-4=122°.4. 
The table is computed from the formula, tan Gores ovine Mss dha, fey et on, 
Diff. Lat. 2 
cos 
2 
In north latitude, when the vessel is 
TABLE 2.—CONVERSION OF POINTS TO DEGREES. 
This table gives the 22 points of the compass arranged in order from North to East, East to 
South, South to West, and West to North. The process of naming these points in this order is 
called ‘‘Boxing the Compass.’’ The names of the whole points and fractional points are readily 
converted by this table into the corresponding degrees, minutes, and seconds, from 0° to 360°. 
TABLE 3.—TRAVERSE TABLE, DEGREES. 
This table contains the difference of latitude and departure corresponding to distances up to 
600 miles and for courses for every degree of the compass. The table may also be employed in the 
solution of any right triangle. ‘The manner of using these tables is particularly explained under the 
different problems of Plane, Middle Latitude, and Mercator Sailing in Chapter V, and the inter- 
changes of the designations of the headings of the different columns in order to subserve these various 
uses, are summarized in the marginal diagram at the foot of each page. 
TABLE 4.—CONVERSION OF DEPARTURE INTO DIFFERENCE OF LONGITUDE. 
This table is computed from the formula, Departure= Diff. Long.Xcosine Mid. Lat., or 
Diff. Long.=—55. Mid. Lat. er: Lat The body of the table gives the difference of longitude (D. Lo.) 
for every mile of departure from one mile to sixty. The middle latitudes are given from 4° to 60°. 
The table is entered with the arguments, Mid. Lat. at the top of the page, and the Dep. at the side 
of the page, from which is found the D. Lo. 
Exampue: In Mid. Lat. 59°30’, the departure was 30 miles. Find the D. Lo. 
Under Mid. Lat. 59°30’ and opposite Dep. 30, is found D. Lo. 59/1. 
Exampue: In Mid. Lat. 54° the D. Lo. was 51.’ Find Dep. 
Under Mid. Lat. 54° and in the D. Lo. column is found 51’, opposite in Dep. column is found 
30 miles. 
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