Fig. 217. - A Spring Engine.

Criticism - A drawing of mediaeval character. It shows, however the principals of the weapon.

The grooved block on which the arrow was laid was raised or lowered by the prop beneath it. The upper end of the prop was hinged to the block which supported the arrow. Its lower end rested on the notches of the upright according to the trajectory required. The arm or spring was pulled back by a windlass and tackle, and on being released violently struck the butt end of the arrow and projected it forward.