Histories

The Persians besieged +Al Marj [20.833,32.5] (inhabited place), Al Jabal al Akhdar, Libya, Africa Barce for nine months, digging underground passages leading to the walls, and making violent assaults. As for the tunnels, a blacksmith discovered them by the means of a bronze shield, and this is how he found them: carrying the shield around the inner side of the walls, he struck it against the ground of the city;

all the other places which he struck returned a dull sound; but where there were tunnels, the bronze of the shield rang clear. Here the Barcaeans made a counter-tunnel and killed those Persians who were digging underground. Thus the tunnels were discovered, and the assaults were repelled by the townsfolk.