The ships and sailors of old Salem

by Ralph Delahaye Paine

The Yorkshire watchmaker, after a lifetime of service, had won a momentous victory, but more exacting tests were demanded of his masterpiece and he was threatened with death from old age before he was finally given the twenty thousand pounds. Thenceforth the chronometer slowly made its way among ship owners as a necessary article of the captain’s equipment and the most important contribution to navigation since the magnetic compass.

Nathaniel Bowditch, author of “The Practical Navigator”

Old-fashioned mariners with an eye to expense continued to find their longitude by means of lunar observations for half a century and more after the chronometer had been perfected, and in American merchant vessels the chronometer may be said to belong to the nineteenth century era of navigation. “Dead reckoning” and lunar observations were the main-stays of the Salem sea captains in the days of their greatest activity over distant seas, and their fellow-townsman, Nathaniel Bowditch, author of “The Practical Navigator,” was a far greater man, and more useful to them, than John Harrison of Yorkshire.

The log-line and sandglass have been discarded on steamers of to-day in favor of the patent log with its automatic registering mechanism, but the old-fashioned method of measuring the ship’s course is used on sailing vessels the world over. It gave to the language of the sea the word “knot” for a nautical mile, and the passenger on board the thirty-thousand-ton express liner of the Atlantic “steamer lanes” talks of her six hundred and odd knots per day without knowing how the word came into use, or that at the taffrail of the white-winged bark or ship passed in midocean the log-line and glass are being used to reckon the miles in genuine old-fashioned “knots,” just as they were employed a century ago.

The “log” is a conical-shaped canvas bag, or a triangular billet of wood so attached to the “log-line” that it will drag with as much resistance as possible. The line is wound round a reel, and is divided at regular intervals into spaces called “knots.” These are marked on the line by bits of rag or leather; at the first knot is a plain piece of leather, at the second a piece of leather with two tails; at the third a knot is tied in the line, and so on according to a simple system which enables the observer to identify the sequence and number of the “knots.” The glass is like an hourglass, but the sand is carefully measured to run through in exactly fourteen or twenty-eight seconds. The log-line and its knots are carefully measured to correspond with the glass. That is, if the sand runs out in twenty-eight seconds, the distance between two knots of the line bears the same ratio to the length of a real “knot,” or nautical mile as the twenty-eight seconds for which the sandglass is set bears to an hour of time. Therefore the number of “knots” of the line unreeled out over the stern of the ship while the sand is running in the glass gives the number of miles which she is traveling per hour.

When the speed is to be read, one man throws overboard the “log” and line, while another stands ready with the glass. The first twenty or thirty fathoms of line are allowed to pay out before the knots are counted. When the drag has settled quietly in the sea astern and anchored itself, a white rag tied to the line marks the instant for turning the glass. As the bit of white rag flashes over the rail the man with the reel begins to count the knots that slip past, the glass is set running, and when the last trickle of sand has sifted through, the man holding it shouts “stop her.” The other man with the log reel notes the number of knots paid out, and down on the ship’s log-book go the figures as the number of miles per hour the ship is making through the water.

The log and sandglass, along with the sounding lead, are survivals of a vanished age of sea life, perhaps the only necessary aids to navigation which are used to-day precisely as our forefathers used them. For this reason, and also because the log and glass played so vital a part in the day’s work of the navigators of such ports as Salem, they have been discussed at some length in this introduction to a sketch of the life of Nathaniel Bowditch, for his place among the truly great men of his time, great in benefactions to humanity, cannot be perceived by the landsman without some slight knowledge of the conditions which then existed in the vastly important science of deep-water navigation.

The nineteenth century had to thank this seafaring astronomer of Salem for its most valuable working treatise on navigation which illustrates with singular aptness the fact, often overlooked, that the ship captain is a practical astronomer and this his calling has been more and more safeguarded by methods of applied science. Or as Professor Simon Newcomb has expressed it:

“The usefulness of practical astronomy and the perfection it has attained may be judged from this consideration: take an astronomer blindfolded to any part of the globe, give him the instruments we have mentioned, a chronometer regulated to Greenwich or Washington time, and the necessary tables, and if the weather be clear so that he can see the stars, he can, in the course of twenty-four hours tell where he is in latitude and longitude within a hundred yards.”