1o. RULE XXII. When latitude and true difference of latitude have like namesTo the latitude from add the true difference of latitude (turned into degrees, minutes, and seconds, if necessary); the sum will be the latitude in, of the same name as the latitude from. 2o. When the latitude from and true difference of latitude have unlike names- -Under the latitude from, put the true difference of latitude (in degrees and minutes, if necessary); the remainder marked with the name of the greater is the latitude in. I. 2. 29 38 N. 104 S. Find the latitude in, in each of the following examples : Lat. from 31° 10' N. D. lat. 172 N. 9. Lat. from o° 8' N. D. lat. 182 S, 3 2 S, 190 N. 50 31 S. 2 56 S. 6. 189 N. 357 N. 12. 13. 49 5 N. 164 S. I 27 S. 4 48 S. 35 25 S, 102 N. 168 S. 15. 38 41 S. N. 110 N. 229 S. 66 S. 243 N. To find the middle latitude, having given the latitude from and latitude in. (For definition, see page 47.) RULE XXIII. The names being supposed alike, that is, both North or both SouthAdd together the true latitudes, and take half the sum; the result is the middle latitude. NOTE. When the names are unlike, the middle latitude (which is seldom required, but for obtaining the departure) should be found by means of a table; but in this case, it may perhaps be as well to avoid the use of the middle latitude in any of the common problems of navigation. To find the difference of longitude, having given the longitude from and the longitude to. RULE XXIV. To find the difference of longitude. (For definition, see page 47.) -Take their difference 1st. When the longitudes are of the same name— and reduce the same to minutes, place E. or W. against the remainder, according as the long. to is East or West of long. from. 2nd. When the longitudes are of contrary names--Take the sum of the two longs., and attach E. or W., according as the long. to is East or West of long. from. NOTE. If the difference of longitude found by the preceding rule exceeds 180°, subtract it from 360°, and reduce the remainder thus found to minutes, attaching to it the contrary name to that found in the usual way. Required the difference of longitude between a place A and a place B, in each of the following examples: To find the longitude in, having given the longitude from and the difference of longitude. RULE XXV. 1o. When the longitude from and the difference of longitude have like names-To the longitude from, add difference of longitude (turned into degrees, if necessary); the sum will be the longitude in of the same name as the longitude from. 2°. When the longitude left and difference of longitude have unlike names-Under longitude from, put difference of longitude (in degrees and minutes, if necessary); take the less from the greater; the remainder, marked with the name of the greater, is the longitude in. NOTE. If the longitude in, found as above, exceed 180°, subtract it from 360°, and attach to the remainder the contrary names to the one directed in the Rule. |