Man on the Ocean: A Book about Boats and Ships. Robert Michael Ballantyne
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disposition will naturally ask. We do not say that all youths will make this inquiry. Many there are who will at once say, “Oh, I know! It’s a needle with a card on the top of it—sometimes a needle with a card under it—which always points to the north, and shows sailors how to steer their ships.”
Very well explained indeed, my self-sufficient friend; but you have not answered the question. You have told us what a compass is like, and one of the uses to which it is applied; but you have not yet told what it is. A man who had never heard of a compass might exclaim, “What! a needle! Is it a darning needle, or a knitting needle, or a drawing-through needle? And which end points to the north—the eye or the point? And if you lay it on the table the wrong end to the north, will it turn round of its own accord?”
You laugh, perhaps, and explain; but it would have been better to have explained correctly at first. Thus:—
The mariner’s compass is a small, flat bar of magnetised steel, which, when balanced on a pivot, turns one of its ends persistently towards the north pole—the other, of course, towards the south pole; and it does this in consequence of its being magnetised. A card is fixed above, sometimes below, this bar of steel (which is called the needle), whereon are marked the cardinal points—north, south, east, and west—with their subdivisions or intermediate points, by means of which the true direction of any point can be ascertained.
“Aha!” you exclaim, “Mr Author, but you yourself have omitted part of the explanation. Why is it that the magnetising of the needle causes it to turn to the north?”
I answer humbly, “I cannot tell;” but, further, I assert confidently, “Neither can anybody else.” The fact is known, and we see its result; but the reason why magnetised steel or iron should have this tendency, this polarity, is one of the mysteries which man has not yet been able to penetrate, and probably never will.
Having explained the nature of the compass, as far as explanation is possible, we present our reader with a picture of one.
It will be seen that there are four large points—N, S, E, and W—the cardinal points above referred to, and that these are subdivided by twelve smaller points, with one little black triangular point between each, and a multitude of smaller points round the outer circle. To give these points their correct names is called “boxing the compass,”—a lesson which all seamen can trip off their tongues like A, B, C, and which most boys could learn in a few hours.
For the sake of those who are anxious to acquire the knowledge, we give the following explanation: Let us begin with north. The large point midway between N and E (to the right) is north-east. The corresponding point midway between N and W (to the left) is north-west. A glance will show that the corresponding points towards the south are respectively south-east and south-west (usually written S.E. and S.W., as the two former points are written N.E. and N.W.). Now, to read off the compass with this amount of knowledge is very simple. Thus: North, north-east, east, south-east, south, south-west, west, north-west, north. But be it observed that, in the language of the sea, the th is thrown overboard, except when the words north and south occur alone. When conjoined with other points they are pronounced thus: nor’-east, sou’-east; and so on.
To come now to the smaller subdivisions, it will suffice to take a quarter of the circle. The point midway between N.E. and N. is “nor’-nor’-east” (N.N.E.), and the corresponding one between N.E. and E. is “east nor’-east” (E.N.E.). These points are again subdivided by little black points which are thus named:– The first, next the N., is “north by east” (N. by E.); the corresponding one next the E. is “east by north” (E. by N.). The second black point from N. is “nor’-east by north” (N.E. by N.), and the corresponding one—namely, the second black point from east—is “nor’-east by east” (N.E. by E.). Thus, in reading off the compass, we say—beginning at north and proceeding to east—North: north by east; nor’-nor’-east; nor’-east by north; nor’-east; nor’-east by east; east nor’-east; east by north; east;—and so on with the other quarters of the circle.
So much for “boxing the compass.” The manner in which it is used on board ship, and the various instruments employed in connection with it in the working of a vessel at sea, will be explained shortly; but first let us glance at the history of the compass.
It is a matter of great uncertainty when, where, and by whom the mariner’s compass was invented. Flavio Gioia, a Neapolitan captain or pilot, who lived about the beginning of the fourteenth century, was generally recognised throughout Europe as the inventor of this useful instrument; but time and research have thrown new light on this subject. Probably the Neapolitan pilot was the first who brought the compass into general notice in Europe; but long before 1303 (the year in which it was said to have been invented) the use of the magnetic needle was known to the Chinese.
Loadstone, that mineral which has the mysterious power of attracting iron, and also of imparting to iron its own attractive power, was known to the Chinese before the year 121, in which year a famous Chinese dictionary was completed, wherein the word magnet is defined as “the name of a stone which gives direction to a needle.” This proves not only that they knew the attractive properties of the loadstone, and its power of imparting these properties to metal, but also that they were aware of the polarity of a magnetised needle. Another Chinese dictionary, published between the third and fourth centuries, speaks of ships being guided in their course to the south by means of the magnet; and in a medical work published in China in 1112, mention is made of the variation of the needle, showing that the Chinese had not only used the needle as a guide at sea, but had observed this one of its well-known peculiarities—namely, the tendency of the needle to point in a very slight degree away from the true north.
In the thirteenth century, too, we find mention made of the needle by a poet and by two other writers; so that whatever Flavio Gioia may have done (and it is probable he did much) in the way of pushing the compass into notice in Europe, he cannot be said to be the inventor of it. That honour doubtless belongs to the Chinese. Be this as it may, the compass was invented; and in the fourteenth century it began that revolution in maritime affairs to which we have alluded.
The first compasses were curiously formed. The Chinese used a magnetised needle, which they placed in a bit of rush or pith, which was floated in a basin of water, and thus allowed to move freely and turn towards the poles. They also made needles in the form of iron fish. An Arabian author of the thirteenth century thus writes:– “I heard it said that the captains in the Indian seas substitute for the needle and reed a hollow iron fish magnetised, so that, when placed in the water, it points to the north with its head and to the south with its tail. The reason that the iron fish does not sink, is that metallic bodies, even the heaviest, float when hollow and when they displace a quantity of water greater than their own weight.”
The use of the compass at sea is so simple, that, after what has been said, it scarcely requires explanation. When a ship sets sail for any port, she knows, first of all, the position of the port from which she sets sail, as well as that to which she is bound. A straight line drawn from the one to the other is her true course, supposing that there is deep, unobstructed water all the way; and if the compass be placed upon that line, the point of the compass through which it passes is the point by which she ought to steer. Suppose that her course ran through the east point of the compass: the ship’s head would at once be turned in that direction, and she would continue her voyage with the needle of the compass pointing straight across the deck, and the east and west points straight along it.
But various causes arise in the actual practice of navigation to prevent a ship keeping her true course. Winds may be contrary, and currents may drive her either to the one side or the other of it; while land—promontories, islands, and shallows—compel her to deviate from the direct line. A vessel also makes what is called “leeway;” which means that, when the wind blows on her side, she not only advances forward, but also slides through the water sidewise. Thus, in the course of a day, she may get a considerable distance off her true course—in sea parlance, “make a good deal of leeway.”
To perform the voyage