Posteriori autem parti tympano medio axis versatilis est inclusus inque eo axi aenea mollis catena est involuta, ex qua pendet ex una parte phellos (sive tympanum), qui ab aqua sublevatur, altera aequo pondere phelli sacoma saburrale.
On the back part in the middle of the drum is fixed a revolving axle. On the axle a pliable brass chain is coiled. On one end hangs a cork or drum raised by the water; on the other, a counterpoise of sand equal in weight to the cork.
final_alignments\Vitruvius_Architecture_Book_9.json