Part 16 (2/2)

The quartermaster took the gla.s.s, and Gordon, then officer of the watch, the chip, which he cast into the water over the stern of the s.h.i.+p.

”Turn!” said he, when the stray line had run out.

Now, Smith, at this particular moment, was watching a vessel over the quarter, and he did not instantly turn the gla.s.s, as he should have done; but Peaks said nothing.

”Up!” cried the quartermaster, when the sand had all run through the gla.s.s.

Gordon stopped the reel from which the line was running out, and noted the mark.

”Seven knots,” said he.

”Not right,” replied the boatswain, sharply. ”This s.h.i.+p is going nine or ten knots an hour, and any man who has snuffed salt water for six months could guess nearer than you make it. Now try it once again, and if you don't hit nearer than that next time, you may as well throw the reel overboard, and hire a Yankee to guess the rate of sailing.”

”I thought we knew all about it,” added Smith.

”I think you do, young gentlemen; but you were star-gazing when you ought to have been all attention. The line ran out two or three knots before you turned the gla.s.s.”

Gordon took the chip again. It was a thin piece of board, in the form of a quarter circle. The round side was loaded with just lead enough to make it float upright in the water. The log-line was fastened to the chip, just us a boy loops a kite, two strings being attached at each end of the circular side, while the one at the angle is tied to a peg, which is inserted in a hole, just hard enough to keep it in place, while there is no extra strain on the board, but which can be drawn out with a smart pull. When the log-line has run out as far as desired, there would be some difficulty in hauling in the chip while it was upright in the water; but a sudden jerk draws the peg at the angle, and permits the board to lie flat, in which position the water offers the least resistance to its pa.s.sage.

The half-minute gla.s.s used on board the Young America, held by the quartermaster, was like an hour gla.s.s, and contained just sand enough to pa.s.s through the hole in the neck in thirty seconds. The log-line was one hundred and fifty fathoms in length, and was wound on a reel, which turned very easily, so that the resistance of the chip to the water would unwind it. The log-line is divided into certain s.p.a.ces called knots, the length of each of which is the same fractional part of a mile that a half minute is of an hour. If there be sixty-one hundred and twenty feet in a nautical mile, or the sixtieth part of a degree of a great circle, which is not far from accurate, and the s.h.i.+p be going ten knots an hour, she will run sixty-one thousand two hundred feet in an hour. If the chip were thrown overboard at eight o'clock, and the line were long enough, the s.h.i.+p would have run out sixty-one thousand two hundred feet, or ten miles, at nine o'clock, or in one hour. In one minute she would run one sixtieth of sixty-one thousand two hundred feet, which is ten hundred and twenty feet; in half a minute, five hundred and ten feet.

The half-minute gla.s.s is the measure of time generally used in heaving the log. While the sand is dropping through, the line runs out five hundred and ten feet, the s.h.i.+p going ten knots an hour being the basis of the calculation. One knot, therefore, will be fifty-one feet. If the line pays out five hundred and ten feet in thirty seconds, by the gla.s.s, the s.h.i.+p is going ten knots an hour. If it pays out four hundred and eight feet in half a minute, or eight hundred and sixteen feet in a minute, she will pay out a mile in as many minutes as eight hundred and sixteen feet is contained in sixty-one hundred and twenty feet, which is seven and a half minutes. Then the s.h.i.+p goes a mile in seven and a half minutes, or eight miles an hour.

A knot on the log-line is therefore invariably fifty-one feet; and the number of knots of the line run out in half a minute indicates also the s.h.i.+p's speed per hour, for fifty-one feet is the same part of a nautical mile that half a minute is of an hour. The calculations are given without allowances, merely to show the principle; and both the gla.s.s and the line are modified in practice.

On board the Young America, ten fathoms were allowed for ”stray line;”

this length of line being permitted to run out before the measuring commenced, in order to get the chip clear of thee eddies in the wake of the s.h.i.+p. The ten fathoms were indicated by a white rag, drawn through the line; and when the officer paying out comes to this mark, he orders the quartermaster to turn the gla.s.s, and the operation actually begins.

At every fifty-one feet (or forty-seven and six tenths, making the allowances) there is a mark--a bit of leather, or two or more knots. The instant the sands have all run through the gla.s.s, the quartermaster says, ”Up,” and the officer notes the mark to which the line has run out. Half and quarter knots are indicated on the line.

”Now, quartermaster, mind your eye. When the officer of the deck says, 'Turn,' you repeat the word after him, to show that you are alive,”

continued Peaks.

”Ready!” said Gordon.

”Ready!” replied Smith.

The lieutenant threw the chip into the water, and when the stray line had run off, he gave the word to turn the gla.s.s.

”Turn!” repeated Smith.

Gordon eased off the log-line, so that nothing should prevent it from running easily.

”Up!” shouted Smith; and Gordon stopped the line.

”Very well,” added Peaks. ”What's the mark?”

<script>