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 schoolboy for slinging
The increase in power conferred by the addition of a sling
to the arm of a catapult is surprising.
A small model I constructed for throwing a stone ball, 1 lb. in weight,
will attain a distance of 200 yards when used with an arm that has a cup
for holding the ball, though when a sling is fitted to the arm the range
of the engine is at once increased to 300 yards.
The only historian who distinctly tells us that the catapults of the
Greeks and Romans had a sling to its arm, is Ammianus Marcellinus. This
author flourished about 380 A.D., and a closer study of his writings, and
those of his contemporaries, led me to carry out experiments with catapult
and balistas which I had not contemplated when my work dealing with the
projectile engines of the ancients was published.
Ammianus writes of the catapult 1:
'In the middle of the ropes 2 rises a wooden arm like a chariot
pole… to the top of the arm hangs a sling... when battle is commenced a
round stone is set in the sling… four soldiers on each side of the engine
wind the arm down till it is almost level with the ground… when the arm
is set free it springs up and hurls forth from its sling the stone, which
is certain to crush whatever it strikes. This engine was formally called
because it has its sting erect,3 but later ages have given it
the name Onager,
or Wild Ass, for when wild asses are chased they kick the stones behind
Fig. 2. - Catapult (With a Sling), See Opposite Page.
A. The arm at rest, ready to be wound down by the rope attached to it
and also to the wooden roller of the windlass. The stone may be seen in
The upper end of the pulley rope is hitched by a metal slip hook (fig.
1. p.10) to a ringbolt secured to the arm just below the sling.
B. The position of the arm when fully wound down by means of the windlass
and rope. See also EE, fig. 3. p.14.
C. The position of the arm at the moment the stone D leaves the sling,
which it does at an angle of about 45 degrees.
1 Roman History, Book XXIII, Chapter
2 i.e. in the middle of the twisted skein formed
of ropes of sinew or hair.
3 The upright and tapering arm of a catapult,
with the iron pin on its top for the loop of the sling, is here fancifully
likened to the erected tail of an angry scorpion with it sting protruding.