The workers began drilling the upper gallery, 37 metres (121 ft) above sea-level, with dynamite and mechanical drills (many mines at the time mostly used pickaxes) until they reached the sea. They then hung from ropes and began drilling the lower tunnel from the cliff-face, 16 metres (52 ft) above sea-level, going the opposite direction under the upper gallery. This way, they could dump the removed rocks directly into the sea.