"Knots always at sea. We rarely make any use of statute miles. I have directed Mr. Shafter to make his best speed, so that we sail six knots faster than the Maud. Gaining six knots an hour, it will take us twenty hours to overhaul the Maud," said the captain. "I shall expect to see her about eight o'clock to-morrow morning, when we shall be off Magrowa Point."
Captain Ringgold invited all the party to his cabin, where the chart of the Mediterranean Sea was spread out on the table. He pointed out Alboran Light to them, with a ring thirty miles in diameter drawn around it. On the northern edge of this circle was a cross, which was connected with Europa Point by a red line.
"What is the ring for?" asked Dr. Hawkes.
"It indicates the distance from all points at which the light can be seen," replied the commander.
"I suppose that red line shows the course we are sailing," added Uncle Moses. "But why is your course alone marked on the chart?"
"I marked that myself with a red pencil; it was not printed on the paper, as you seem to suppose. Captain Scott made just such a line on his chart," the captain explained.
"But it is not straight," the surgeon objected. "If you should keep on this course you would hit the African coast at Columbi Island," as he read the name from the chart.
"It was not intended to be straight," answered the commander. "I am following the course laid down by Captain Scott for the Maud, so that I shall be able to find him to-morrow morning. I should have gone farther to the north of Alboran, and I should not have seen it in consequence; but I thought he might need the light to assure him where he was."
"Here is another little red cross just north of Algiers, with a red line drawn from it to the one north of Alboran," said Dr. Hawkes, scrutinizing the chart very closely. "That, I conclude, is the course between the two crosses."
"Quite right, Doctor; you would easily become a navigator."