12Beams of considerable length must be procured, upon which are fixed cheeks in which the axles are retained; in the middle of those beams holes are made, into which are received the capitals of the catapultæ, well tightened with wedges, so that the strain will not move them. Then brazen stocks are fixed for the reception of the capitals, in which are the small iron pins which the Greeks call ἐπισχίδες.
2The ends of the ropes pass through the holes of the capitals, and brought through on the other side, they are then passed round the axle of the windlass, which is turned by the aid of levers, till the ropes, both drawn tight, give the same tone when struck by the hand. Then they are confined at the holes with wedges, to prevent their slipping. Being passed through to the other side, they are in a similar way tightened by the levers and axles till the tones are similar. Thus by the use of the wedges, catapultæ are adjusted, according to the effect of musical tones on the ear.