Captain Solomon usually had the speed at which the ship was sailing measured several times every day. When he wanted that done, he called a sailor to "heave the log;" and the sailor came and took up a real log, or board, fastened to the end of a long rope, while one of the mates held an hour glass. But there wasn't sand enough in the glass to run for an hour, but it would run for half a minute. And when the mate gave the word, the sailor dropped the log over the stern of the ship and the mate turned the glass. And the sailor held the reel with the rope on it, so that the rope would run off freely, and he counted, aloud, the knots in the rope as it ran out. For the rope had knots of colored leather in it, and the knots were just far enough apart so that the number of knots that ran out in half a minute would show the number of sea miles that the ship was sailing in an hour. And when the sand in the glass had all run out, the mate gave the word again, and the sailor stopped the rope from running out. So Captain Solomon knew about how many miles the Industry had sailed on each course, and he could put it down in his book.
That wasn't a very good way to tell where the ship was, by adding up all the courses she had sailed and getting her speed on each course, and adding all these to the last place that they knew about, but, when Captain Solomon couldn't get an observation with his sextant, it was the only way there was. That isn't the way they tell, now-a-days, how many miles a ship has sailed, for there is a better way that gives, more exactly than the old-fashioned "log," the number of miles. But they still have to add up all the courses and the miles sailed on each course to find a ship's place, when they can't take an observation. That is what is called "dead reckoning," and it isn't a very good way at its best.
"LITTLE JACOB LIKED TO WATCH CAPTAIN SOLOMON"
Little Jacob liked to watch Captain Solomon writing up the log for the day. He always wrote it just after dinner. And when he had finished dinner, he would get out the book and clear a place on the table to put it; and then he took a quill pen in his great fist and wrote, very slowly, and with flourishes. And when he had it done he always passed the book over to little Jacob.
"There, Jacob," he said, with a smile. "That please you?"
"Oh, yes, sir," answered little Jacob. "Thank you, sir." And he began to read.
One day, when they had been out of Boston about three weeks, little Jacob watched Captain Solomon write up the log, and, when he got it, he thought he would turn back to some days that he knew about and read what Captain Solomon had said about them. And so he did.
October 2, 1796. 8 days out. Comes in fresh gales & Flying clouds. Middle & latter part much the same, with all proper sail spread. Imploy'd varnishing Deck and scraping Foreyard. Saw a Brig and two Ships standing to the N. & W. A school of porpoises about the ship a good part of the Morning, of which the Crew harpooned a good number and got them on deck. I fear they are too many for us to acct. for before they go Bad.
Course ESE 186 miles. Wind fresh from S. & W. Observatn, Lat. 34 20 N. Long. 53 32 W.