Bringing the sextant on deck, Captain McCloud gazed through it at the sun, as reflected in a small mirror, until it had reached its greatest altitude and stood exactly above the meridian, or, in other words, until it was noon. By looking at the chronometer, which was set to Greenwich time, the difference between the noon where they then were and Greenwich noon was found to be three hours and twenty-six minutes, or two hundred and six minutes. As the earth revolves from west to east at the rate of one degree--which at the equator is sixty miles--every four minutes, the whole number of minutes divided by four gave fifty-one and a half, or 51° 30´, as the longitude of the brig west from Greenwich.
The latitude of the place--its distance north or south from the equator--was obtained by another observation of the sun, taken with the sextant, for the purpose of finding the angle between it and the zenith, or point directly overhead. A glance at the Nautical Almanac under the date of that day, and a minute’s figuring, gave the required result. The latitude thus found was 43° 37´, and of course, being north of the equator, it was north latitude, or 43° 37´ north.
Having obtained these two figures, Captain McCloud got out a chart of that portion of the Atlantic, and drawing on it a fine north and south line through meridian of longitude 51° 30´ west, and a delicate east and west line to indicate parallel of latitude 43° 37´ north, he made a small cross at their point of intersection, and showed it to Breeze as the position of the brig at that moment. It was very near the southern point of the Grand Bank and almost due east from Gloucester, but over eight hundred miles from that port.
“There!” said Captain McCloud when he had finished these operations, in all of which Breeze had been greatly interested. “If we steer due west, and hold this wind, we ought to sight Sable Island by day after to-morrow, and run into port inside of three days more. How would that suit you, my boy?”
“It seems as though I couldn’t wait for the time to come, father. Won’t it be glorious to sail into Gloucester harbor and take everybody by surprise? But, father, while we are on this cruise I wish you would teach me something of navigation. I never saw an observation taken before. They don’t take them on board fishing schooners, do they?”
“Not often. Most fishing skippers trust to their lead, log, and compass. They can generally tell by the sort of bottom the lead brings up where they are. You have often, I dare say, noticed skippers examining the sand and shells that stick to the tallow in the bottom of the lead.”
Breeze said he had, but that he should think it would be pretty hard to remember what the whole bottom of the ocean was made of.
“We don’t try to,” laughed his father, “we only remember what sort of material forms a few of the principal banks and reefs. For the rest we examine the charts, where it is all laid down. Now I am going to show you an old-fashioned-log, and how to use it. It is the only one I can find aboard, though many vessels nowadays use patent self-registering logs.”
“Of course I have often heard of heaving the log,” said Breeze, casting an eye aloft at the sails, then glancing at the compass, and giving the wheel a spoke or two to keep the brig on her true westerly course, “but I never knew exactly how it was done.”
Captain McCloud called upon Nimbus to bring him the log and the glass, and made ready to use them. The log was a triangular piece of thin board, having its base rounded and weighted with lead. Three short lines extending from the three corners fastened it to the log-line, much as a kite is hung. The log-line was about a thousand feet long, and had a number of red rags, or “knots,” tied to it, at distances of fifty-one feet apart. Each of these long spaces was divided into ten short spaces, called “fathoms,” by bits of leather twisted into the line.