“If it wasn’t for the magnetic variation,” explained Alan, “we would sail north, sixty-seven degrees east. But the magnetic variation in this place is thirty-three and one-half degrees. We’ve got to subtract this variation. As there are only ninety degrees in a quadrant this sixty-seven degrees north of east changes to seventy-nine and one-half degrees south of east. Or, by compass points, east by south. The first is the true course. The last is our magnetic course.”
“And the rest of our journey,” added Ned, “is made up of eleven straight flights across the Atlantic.”
He showed Buck the pilot chart on which these lines were indicated with the altered courses for each and the tabulation for the pilot’s use. These were now spread out on the operator’s table ready for the night’s long vigil. The tabulated matter was a maze of figures in this form:
Fogo Island to London—Rhumb Line Course:
MILES:
146 to 50° W. and 50° 40´ N.; True course N. 67 E.
Variation 33-1/2° W.; Magnetic course S. 79-1/2
E. or E. by S. Time 8.59 P. M.
199.6 to 45° W. and 51° 45´ N.; True course N. 71 E.
Variation 35° W.; Magnetic course S. 74 E., or