Adit

There will be no opportunity to drive an adit to a mine situated on a large flat plain, for instance.

Horizontal travel by means of narrow-gauge tramway or cable car is also much safer and can move more people and ore than vertical elevators.

In combination with shafts, adits form an important element in the ventilation of a mine: in simple terms, cool air will enter through an adit, be warmed by the higher temperature underground and will naturally exhaust from vertical shafts, some of which are sunk specifically for this purpose.

[6] Most adits are designed to slope slightly upwards from the entrance so that water will flow freely out of the mine.

One example is the Milwr tunnel in North Wales, which is about ten miles (16 km) long.

A side benefit of driving such extensive adits is that previously unknown ore-bodies can be discovered, helping finance the enormous cost.