The tunnellers relied on the strength of their arms, on their skills with a sledgehammer and a crowbar, and were also aided with gunpowder for blasting. In five weeks 18 men had driven a tunnel 8 square feet (2.4sq m) by 82 feet long (25m) into the Rock. It is interesting to compare this with the record of a fully mechanised tunnelling company in Gibraltar during World War II, who in a week advanced 180 feet (55m).

http://www.the-rock-of-gibraltar.com/Great-Siege-Tunnels/