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28 THE Marine REVIEW ~ Modern Methods of Lake Navigation for the Latitude. . The earth is divided by imaginary ~ lines running both north and south and east and west. -These lines are for the purpose of location of places, etc. The lines running north and south are meridians of longitude and the lines running east and west are -parallels of latitude. If you were told -that a certain place was at latitude 40 and longitude 20 you would look for it where the east and west line marked 40 crosses the north and south line marked 20. . Thus-- PARALLELS. FIG. 14. me. eo 2020 0 20 al 60 60 40 40 201 \20 40 LO O Fic. 16, Now in figuring for latitude and longitude there must be a place selec- ted to place the first lines. Then the other lines figure from here. All fig- uring for latitude and longitude is done in degrees and parts of a de- gree. Every circle has 360 degrees. Therefore as the parallets~of latitude go clear around the earth each line - Beginner. is 360 degrees long. But the meri- dians of longitude are only 180 de- MERIDIANS. mic; - 15. grees long. They go only from pole to pole and this makes just half a circle. We will illustrate these lines by using a ball to represent the earth and mark the lines on ourselves. *¥1G. 17. Fig. 17 illustrates how our ball looks with no lines on it. We have now marked a north and south pole on our ball: (Fig. 18) and divided it in the mid- dle with a line that runs ex- actly east and west. This fine js the equator and is a starting point for figuring latitude, Anything north of this line is in north latitude and any- thing south of it is in south latitude. We have now drawn several paral- lels of latitude on our ball, Fig: 19, YOU can set. them any dis- tance apart you wish, Re- member it is just 90 degrees from the equator to either pole. The Great NORTH POLE WEST es s warcerteditates EAST SOUTH POLE Fic, 1 Fic. 19, Lakes are between latitude 41 and 49 north of the equator. We now show some longitude' on our ball, The first meridian N meridians of Fig. 220 is called e FIG. 20, the prime meridian and is marked 0. Then if you travel west the longitude is called west longitude until you get half way around the ball (to the 180th meridian). Then it is east longitude for the other half.