“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. The glass, which was to mark the time of the log’s running, was shaped like an hour-glass, but was much smaller, and the sand contained in it occupied only half a minute in running from one end to the other. Now, half a minute is the one hundred and twentieth part of an hour, and fifty-one feet is the same portion of a nautical mile, which is 6120 feet, or 840 feet longer than a geographical or land mile. Thus, when we say that a vessel sails six knots (or miles) an hour, we mean that six knots, or three hundred and six feet, of the log-line ran out in half a minute. The log-line is wound on a reel that turns very easily. In the present instance Nimbus dropped the log into the water over the lee quarter of the brig, and held the reel in his hands. When the first fifty feet, which is called the “stray-line,” and is sufficient to carry the log clear of the vessel’s eddy, had run out, and Nimbus saw the first red rag touch the water, he sang out, “Turn!” Captain McCloud turned the half-minute glass, so that the sand in it began to drop to the other end, and answered, “Done!” The instant it stopped running he cried, “Stop!” and Nimbus held the reel, so that no more line should run out. “Seben knot, five fadom, sah,” he reported to the captain.