Which was
firmly attached by a ring, whilst the other hung in a loop over an iron
hook which formed the extremity of the shaft. The power employed to
discharge the sling was either the strength of a number of men, applied to
ropes which were attached to the short end of the shaft or lever, or the
weight of a heavy counterpoise hung from the same, and suddenly released.
[Illustration: Mediaeval Artillery Engines. Figs. 1, 2, 3, 4, 5, Chinese;
Figs. 6, 7, 8, Saracenic: the rest Frank.]
Supposing the latter force to be employed, the long end of the shaft was
drawn down by a windlass; the sling was laid forward in a wooden trough
provided for it, and charged with the shot. The counterpoise was, of
course, now aloft, and was so maintained by a detent provided with a
trigger. On pulling this, the counterpoise falls and the shaft flies
upwards drawing the sling. When a certain point is reached the loop end of
the sling releases itself from the hook, and the sling flies abroad whilst
the shot is projected in its parabolic flight.[4] To secure the most
favourable result the shot should have acquired its maximum velocity, and
should escape at an angle of about 45 deg.. The attainment of this required
certain proportions between the different dimensions of the machine and
the weight of the shot, for which, doubtless, traditional rules of thumb
existed among the mediaeval engineers.
