“Can’t say; don’t know her speed. Commandant said two hundred, and she’s made maybe forty or fifty since.”
“How in blazes are we going to find the blasted tub then?” Jim was feeling subconsciously the loss of ten thousand dollars.
“Say she’s making twenty, and we approximate a hundred, we ought to overhaul her in about three hours at the outside. Lay off her course on the chart from Philly to Havana; get on to it and take a high level after her.”
For ten minutes there was silence while Jim scribbled frantically with his pencil and the great machine roared and throbbed all round them. Finally:
“Huh,” came a grunt. “’Bout thirty miles out, and then south by east and keep guessing for luck.”
Rankin watched his clock for eight more minutes with infinite care, for when one is hurtling through the air at a hundred miles an hour delay means more than a little difference. Then he banked sharply over and swung round.
“Ought to be on her tail now,” he muttered. “Now figure drift and give me my variation.”
Technical sounding-stuff, but easy of explanation. Just as a boatman rowing across a tide rip has to point the nose of his boat several degrees into the current in order to hold a straight course for the desired landing, so an aeroplane rushing through a cross wind must “crab” sometimes.
Easy of explanation; but for an aeroplane flying over water with no landmarks to guide, a considerable calculation. And time! Every minute of time counted so vitally! To arrive at a correct conclusion many factors had to be taken into consideration, the least error in the smallest of which would mean many miles of difference.
The main factors, of course, were actual speed through the air and wind speed. The first was easy; an instrument gave it. But wind speed? On the ground, stationary, an instrument could give that too; but at five thousand feet in the air it had to be calculated. To do that one had to know the approximate length between the crests of the waves; and to approximate that, one had to know the exact height.