Precautions of this sort are necessary, for it is impossible to foretell the exact nature of the difficulties which will confront the pot-holer. The deepest known cave in the world is the Gouffre Berger near Grenoble. It extends to a depth of 3,723 feet. This immense chasm has been formed by an underground stream which has tunnelled a course through a flaw in the rocks.
The entrance to the cave is on a plateau in the Dauphiné Alps. As it is only six feet across at the entrance, it was literally a case of 'squeeze or burst'. The deepest part of the cave was reached by Captain Berger in 1950. He had been there many times, but always in the company of five or six people.
On this occasion, he decided to go down alone. He started from the entrance and began to descend. For the first time, he became aware that all around him was an immense, gloomy cavern. As he went deeper, he came to a narrow passage. He squeezed through a cleft in the rocks and found himself in an enormous cavern.
To his surprise, the floor of the cavern was split by a crevasse. He could hear the sound of a powerful waterfall. He lowered a rope and climbed down into the crevasse. At the bottom, he came upon a vast lake. The lake was dark and still. Fearing that his light might give out, he decided to return.
As he tried to climb up, his candle went out and he was left in complete darkness. He felt around with his hands and tried to find the rope. In his struggle, the rope broke and he tumbled back into the water. The situation now seemed hopeless. His cries for help echoed through the cavern, but there was no reply.