Camping and woodcraft - Scoutmastercg.com

74 CAMPING AND WOODCRAFTflat and lay the compass on it with N-S line of dialexactly parallel with N-S line on map. Then revolvemap until needle shovi^s proper number ofdegrees allowance for local variation, if any. Allmeridians on the map will then be parallel with thelines they represent on the ground. Now you cantake the bearings of your objective, and if the instrumenthas a movable course arrow (see Vol. I., p.169) set it accordingly.The following table of declinations, prepared bythe U. S. Coast and Geodetic Survey, is copied fromthe World Almanac of 19 16. By adding or subtracting,as the case may be, the "annual change"multiplied by the number of years after 19 16, youwill get a close approximation to the variation fora future date, although the annual change is notconstant.Fig.10.—Compass Variation