"Aden, from which we sailed the other day, is in longitude 45° east. Every degree by meridians is equal to four minutes of clock-time. Multiply the longitude by four, and the result in minutes is the difference of time between Greenwich and Aden, 180 minutes, or three hours. When it is noon at Greenwich, it is three o'clock at Aden, as you see in the diagram before you."
"Three o'clock in the morning, Mr. Scott?" queried the commander.
"In the afternoon, I should have added. Going east the time is faster, and vice versa," continued the young officer. "At our present speed our clocks must be put about twenty minutes ahead, for a third of an hour has gone to Davy Jones's locker."
"I understand all that perfectly," said Miss Blanche with an air of triumph.
"You will be a sea-monster before you get home. The sirens were beautiful, and sang very sweetly," added Scott jocosely.
"They were wicked, and I don't want to be one. But I do not quite understand how you found out what time it was at noon to-day," added the young lady.
"For every degree of longitude sailed there is four minutes' difference of clock-time," Scott proceeded. "You know that a chronometer is a timepiece so nicely constructed and cared for, that it practically keeps perfect time. Meridians are imaginary great circles, and we are always on one of them. With our sextants we find when the centre of the sun is on the celestial meridian corresponding to the terrestrial one; and at that instant it is noon where we are. Then we know what time it is. We compare the time thus obtained with that indicated by the chronometer, and find a difference of four hours."
"I see it all!" exclaimed the fair maiden, as triumphantly as though she had herself reasoned out the problem. "Four hours make 240 minutes, and four minutes to a degree gives 60° as the longitude.
"Quite correct, Miss Woolridge," added Scott approvingly.
"If I could only take the sun, I could work up the longitude myself," the little beauty declared.