it on a nail, observing that the distance between the nail and middle of the plummet be 39 inches; then swing the plummet, and notice how often it swings while the glass is running out, and that will be the number of seconds meassured by the glass.

If the vessel's speed is greater than four knots the fourteen-second glass is used instead of the twenty-eight second, and the number of knots run out is doubled to ascertain the actual rate of sailing, as the line is graduated for the twenty-eight second glass. The twenty-eight and fourteen second glasses are called respectively the long and short glasses.

In addition to the chip log, vessels of war are furnished with "The Bliss Patent Taffrail Log" and "The Negus Improved Taffrail Log." The former is considered reliable for speeds up to ten or twelve knots, the latter for still higher speeds. The general features of both are the same.

The Bliss Patent Taffrail Log (Fig. 9). This is a mechanical. log, consisting of a rotator, or fly, which is towed well astern of the vessel, clear of the eddy currents; and of a series of geared wheels arranged in a brass cylinder secured to some convenient place on board ship well aft. The rotator, as it is drawn through the water, revolves like an ordinary propeller, and these revolutions are transferred to the geared wheels by means of a plaited rope about 200 feet long. The inner end of this rope is secured to the outer end of a spindle, the inner end of which is an endless screw, geared into two small wheels which transfer the turns to three registering wheels. The axes of the registering wheels carry pointers that register speed in knots and tenths, up to 100 knots.

The Negus Improved Patent Taffrail Log (Fig. 11). This log differs from the one just described, in that the system of geared wheels is provided with a fly wheel and a governor. The governor consists of a rod with a ball at each end, the line being attached to the middle of the rod. The movement of the geared wheels is similar to a clock made with strong and well proportioned springs. A length of line, varying with the speed of the vessel, is recommended for use with this log.

Both logs should be carried on the weather side of the taffrail, and the works kept well oiled. The rotator should be carefully watched to see that it is not fouled by sea-weed or other floating substances. It must also be remembered that no patent log of this description can register accurately in a heavy head sea.

The Ground Log is the common log line with a hand-lead attached, and is used in tideways and currents, in soundings, to ascertain the vessel's speed over the ground. The speed of steamers is generally estimated from the number of revolutions of the engines.

CHAPTER III.

ROPE.

THERE are four varieties of rope in the United States naval service: that made of the fibres of the hemp plant; the Manila rope, made of the fibres of a species of the wild banana; hide rope, made of strips of green hide, and wire rope.

In some countries, ropes made of horse hair, of the fibrous husk of the cocoanut, called coir-rope, and of tough grasses, are quite common. In our own country, rope has been made from fibres of the flax and cotton plants. The metals have also been put in requisition, copper-wire rope being used for particular purposes, principally for lightning conductors, and iron and steel wire are in general use for standing rigging: steel wire being some fifty per cent. stronger than iron wire of the same size.

Of the many vegetable substances that are adapted to rope-making, the best is hemp-hemp-rope possessing in a remarkable degree the essential qualities of flexibility and tenacity.

Hemp in its transit from its native fields to the ropewalk passes through the operations of dew-rotting, scutching and hackling. In the first process water dissolves the glutinous matter that binds the fibrous portion to the woody core, thus partly setting the fibres free; scutching breaks the stalk and separates it still further from the fibre, and hackling consists in combing out the hemp to separate the long and superior fibres from the short and indifferent ones or tow.

The hemp of commerce is put up in bundles of about 200 lbs. each. If good, it will be found to possess a long, thin fibre, smooth and glossy on the surface, and of a yellowish green color; free from "spills," or small pieces of the woody substance; possessing the requisite properties of strength and toughness, and inodorous.

Russian and Italian hemp are considered the best, for the generality of purposes. Rope made from the best quality of Russian hemp, is more extensively used in the navy than any other kind.

Italian hemp is only used in the navy for packing for engines, its cost being more than double that of Russian hemp.

The Native American dressed hemp, easily distinguished

by its dark grayish color, is preferred for many purposes, such as for marline, houseline, hambroline, and all cordage spun by hand, the fibre being finer than that of the Russian hemp.

Cotton is a poor substitute for hemp, in rope-making, lacking its strength and durability. It retains moisture when once wet, and is liable to rot.

Flax is used sometimes for deep-sea sounding-lines, though reeled piano wire has replaced it for this purpose where great depths are measured.

Sail Twine is made of cotton or flax.

The size of Rope is denoted by its circumference, and the length is measured by the fathom. The cordage allowed in the equipment of a man-of-war ranges from 1 (15-thread) to 10 inches inclusive.

ROPE-MAKING.

In rope-making, the fibres of hemp, not averaging more than three and a half feet in length, must necessarily be overlapped among themselves and compressed together so as not to be drawn apart. The required compression is given by twisting, the fibres being continuously drawn out together, from a bundle, in the right quantity to produce the required size of thread or yarn. 'Yarns are then combined by twisting, and form a strand; three or four strands, by twisting, form a rope, and three or four ropes, a cable. These successive steps, in each of which the twist is reversed, cause the strain to be more equally diffused among the fibres than it would be if these were laid together in sufficient quantity at once and twisted, and moreover, the alternating directions given to the twist in the several operations, cause the different portions to bind upon themselves, and form a permanently firm bundle. The fibres only once twisted, make but a loose bundle, which, though decidedly stronger than the same quantity made into a hard-twisted rope, is not so durable nor so well adapted to the ordinary purposes of rope.* The actual loss in strength, by twisting, as found by trial, is about one-third the full strength of the fibre; its loss in length, from the same cause, being also one-third.

Rope is made in long buildings called rope-walks. The size of the yarn varies according to the kind of rope for which it is intended. Forties--so-called because forty yarns will just fill a half-inch tube-are for the finer kinds of rope; twenties, requiring twenty to fill the tube, are for cables, hawsers, etc. From the spinning-room the bobbins containing the yarn are taken to the tar-house, where they are placed in frames conveniently arranged with reference to the tar-box. This is a long box filled with tar kept during the operation of tarring at a temperature of 220° F. by means

*The wires which compose the cables of the East River Suspension Bridge, N. Y., are not laid up," or twisted, but are run straight and bound together.

of steam heaters. The yarns are led from the bobbins in the frame through two or more guide-plates working in a vertical plane over the tar-box, and convenient for lowering into the tar; thence to the farther end (between metal rollers, which press out and return to the box the superfluous tar) on to a large wooden drum to cool them; through fair-leaders, and finally to a fresh set of bobbins, where they are wound up with the utmost regularity.

Rigging is so much exposed to moisture and heat that hemp would soon decay if not protected. Tar, though really injurious in its effects upon the hemp fibre, has been found indispensable to its general preservation.

The manila fiber is cut to the required length, oiled, drawn, and spun into yarns.

Varieties of Rope. In rope-making the general rule is to spin the yarn from right over to left. All rope yarns are therefore right-handed. The strand, or ready, formed by a combination of such yarns, becomes left-handed. Three of these strands being twisted together form a right-handed rope, known as plain-laid rope. Fig.

14. Plate 10.

White Rope. Hemp rope, when plain-laid and not tarred in laying-up, is called white rope, and is the strongest hemp cordage. It should not be confounded with Manila. It is used for log-lines and signal halliards. The latter are also made of yarns of untarred hemp, plaited by machinery to avoid the kinking common to new rope of the ordinary make. This is called "plaited stuff," or "signal halliard stuff."

The tarred plain-laid ranks next in point of strength, and is in more general use than any other. The lighter kinds of standing rigging, much of the running rigging, and many purchase falls are made of this kind of

rope.

Cable-laid or Hawser-laid Rope, Fig. 15, is left-handed rope of nine strands, and is so made to render it impervious to water, but the additional twist necessary to lay it up seems to detract from the strength of the fibre, the strength of plain-laid being to that of cable-laid as 8.7 to 6; besides this, it stretches considerably under strain.

Back-handed Rope. In making the plain laid, it was said that the readies were left-handed, the yarns and the rope itself being right-handed. If, instead of this, the ready is given the same twist the yarn has (right-handed), then, when brought together and laid up, the rope must come left-handed. This is called left-handed or back-handed rope. It is more pliable than the plain-laid, less liable to kinks and grinds when new, and is allowed, in the navy, for reeving off lower and topsail braces.

Shroud-laid Rope, Fig. 16, Plate 10, is formed

by adding another strand to the plain-laid rope. But the four spirals of strands leave a hollow in the centre, which, if unfilled, would, on the application of strain, permit the strands to sink in, and detract greatly from the rope's strength, by an unequal distribution of strain. The four strands are, therefore, laid up around a heart, a small rope, made soft and elastic, and about one-third the size of the strands.

Experiments show that four-stranded rope, when under 5 inches, is weaker than three-stranded of the same size; but from 5 to 8 inches, the difference in strength of the two kinds is trifling, while all above 8 inches is considered to be equal to plain-laid when the rope is well made.

All hemp or manila rope above 3 inches now issued to the Navy is four stranded. All laniard stuff is four stranded. The heart used in all rope is made of jute.

Tapered Rope is used where much strain is brought on only one end. That part which bears the strain. is full-sized, tapering off to the hauling part, which is light and pliable. Fore and main tacks and sheets are made of tapered rope.

Manila Rope seems to be better adapted to certain purposes on board ship than hemp, being more pliable, buoyant, causing less friction, and not so easily affected by moisture. It is used for hawsers, tow-lines, and for lightrunning rigging and gun-tackle falls.

Large hemp and manila cables have been generally replaced by steel wire hawsers; the latter being much lighter, stronger, and more durable.

Hide Rope is made of strips cut by machinery from green hides.

Bolt Rope is the name applied to rope used for roping sails. It is made of the best hemp and finest yarns, and is the most superior kind of cordage.

Small Stuff is the general term applied to small rope. It is particularized by the number of threads or yarns which it contains, and is further known either as ratline stuff or seizing stuff.

Ratline Stuff is three-stranded, right-handed small stuff of 24, 21, 18, 15 or 12 threads. It is measured by the fathom.

Seizing Stuff. Is of 9, 6, 4 or 2 threads, and is measured by the pound. While all varieties of small stuff may be spoken of as "24, 18, 9, &c., thread stuff," the smaller varieties have also special names, according to their number of threads and the manner of laying up. We have:

Hambroline, two-stranded, right-handed, and Roundline, three-stranded, right-handed. Both of these are made of fine back or left-handed yarns, so that the stuff itself is right-handed.