The other early method used was the digging of bell pits with lateral tunnels, called drifts, following the vein.

At almost every level a few slaves turned off into these lateral tunnels which were well lighted, though not quite as brilliantly as the spiral.

They marched for a long distance down the lateral tunnel that led toward the north.

A perennial stream now flows through the cave and is fed by various lateral tunnels and seepage from the roof.

Nothing of the sort was perceived, though the carvings were in places rather sparse because of the numerous mouths of smooth-floored lateral tunnels.

Up to 34 lateral tunnels each ending in a brood chamber branch off from the main tunnel.

He returned to the canyon, where the lateral tunnel was now almost completely open.

Three shafts and a series of lateral tunnels known as drifts comprised the underground works.

Have the tunnel-boring machine dig the lateral retaining tunnel.

- Chapter 60 - The tunnel-boring machine and the Doodlebug had been secured in the lateral retaining tunnel.