"strand" (_C_, Fig. 1). Three or more strands form a rope (_D_, Fig.
1), and three ropes form a cable (_E_, Fig. 1). To form a strand the
yarns are twisted together in the opposite direction from that in
which the original fibres were twisted; to form a rope the strands are
twisted in the opposite direction from the yarns of the strands, and
to form a cable each rope is twisted opposite from the twist of the
strands. In this way the natural tendency for each yarn, strand, or
rope to untwist serves to bind or hold the whole firmly together (Fig.
1).

[Illustration: FIG. 1.--Construction of rope.]

Rope is usually three-stranded and the strands turn from left to right
or "with the sun," while cable is left-handed or twisted "against the
sun" (_E_, Fig. 1). Certain ropes, such as "bolt-rope" and most
cables, are laid around a "core" (_F_, Fig. 2) or central strand and
in many cases are four-stranded (Fig. 2).

[Illustration: FIG. 2.--Bolt-rope.]

The strength of a rope depends largely upon the strength and length of
the fibres from which it is made, but the amount each yarn and strand
is twisted, as well as the method used in bleaching or preparing the
fibres, has much to do with the strength of the finished line.

Roughly, the strength of ropes may be calculated by multiplying the
circumference of the rope in inches by itself and the fifth part of
the product will be the number of tons the rope will sustain. For
example, if the rope is 5 inches in circumference, 5 X 5 = 25,
one-fifth of which is 5, the number of tons that can safely be carried