Fig. 6.—Sketch plan of a Catapult for slinging Stones its Arm being partly wound down.
Approximate scale: ¼ in. = 1 ft.
The addition of a sling to the arm of a catapult increases its power by at least a third. For example, the catapult described in Chapters LV., LVI., of my book,[6] will throw a round stone 8 lbs. in weight, from 350 to 360 yards, but the same engine with the advantage of a sling to its arm will cast the 8-lb. stone from 450 to 460 yards, and when its skein is twisted to its limit of tension to nearly 500 yards.
[6] The Crossbow, etc.
If the upper end of the arm of a catapult is shaped into a cup to receive the stone, as shown in [fig. 5], p. 11, the arm is, of necessity, large and heavy at this part.
If, on the other hand, the arm is equipped with a sling, as shown in [fig. 6], opposite page, it can be tapered from its butt-end upwards, and is then much lighter and recoils with far more speed than an arm that has an enlarged extremity for holding its missile.
When the arm is fitted with a sling, it is practically lengthened by as much as the length of the sling attached to it, and this, too, without any appreciable increase in its weight.
The longer the arm of a catapult, the longer is its sweep through the air, and thus the farther will it cast its projectile, provided it is not of undue weight.
The difference in this respect is as between the range of a short sling and that of a long one, when both are used by a school-boy for slinging pebbles.
The increase of power conferred by the addition of a sling to the arm of a catapult is surprising.