[00:01.080]--- lesson 42 modern caveman
[00:05.720]--- Listen to the tape then answer the question below.
[00:11.320]--- With what does the writer compare the Gouffre Berger?
[00:17.760]Cave exploration, or pot-holing, as it has come to be known, is a relatively new sport.
[00:24.800]Perhaps it is the desire for solitude or the chance of making an unexpected discovery that lures people down to the depths of the earth.
[00:35.200]It is impossible to give a satisfactory explanation for a pot-holer's motives.
[00:40.880]For him, caves have the same peculiar fascination which high mountains have for the climber.
[00:47.480]They arouse instincts which can only be dimly understood.
[00:52.720]Exploring really deep caves is not a task for the Sunday afternoon rambler.
[00:58.880]Such undertakings require the precise planning and foresight of military operations.
[01:05.800]It can take as long as eight days to rig up rope ladders and to establish supply bases before a descent can be made into a very deep cave.
[01:17.160]Precautions of this sort are necessary,
[01:20.360]for it is impossible to foretell the exact nature of the difficulties which will confront the pot-holer.
[01:27.520]The deepest known cave in the world is the Gouffre Berger near Grenoble.
[01:33.440]It extends to a depth of 3,723 feet.w
[01:38.680]This immense chasm has been formed by an underground stream which has tunnelled a course through a flaw in the rocks.
[01:47.360]The entrance to the cave is on a plateau in the Dauphine Alps.
[01:52.640]As it is only six feet across, it is barely noticeable.
[01:56.960]The cave might never have been discovered has not the entrance been spotted by the distinguished French pot-holer, Berger.
[02:05.120]Since its discovery, it has become a sort of potholers' Everest.
[02:10.240]Though a number of descents have been made, much of it still remains to be explored.
[02:16.200]A team of pot-holers recently went down the Gouffre Berger.
[02:20.840]After entering the narrow gap on the plateau, they climbed down the steep sides of the cave until they came to a narrow corridor.
[02:29.720]They had to edge their way along this, sometimes wading across shallow streams, or swimming across deep pools.
[02:38.520]Suddenly they came to a waterfall which dropped into an underground lake at the bottom of the cave.
[02:45.920]They plunged into the lake, and after loading their gear on an inflatable rubber dinghy, let the current carry them to the other side.
[02:56.160]To protect themselves from the icy water, they had to wear special rubber suits.
[03:02.080]At the far end of the lake, they came to huge piles of rubble which had been washed up by the water.
[03:08.360]In this part of the cave, they could hear an insistent booming sound
[03:13.720]which they found was caused by a small waterspout shooting down into a pool from the roof of the cave.
[03:20.600]Squeezing through a cleft in the rocks, the pot-holers arrived at an enormous cavern, the size of a huge concert hall.
[03:29.640]After switching on powerful arc lights, they saw great stalagmites -- some of them over forty feet high -- rising up like tree-trunks to meet the stalactites suspended from the roof.
[03:43.000]Round about, piles of limestone glistened in all the colours of the rainbow.
[03:48.640]In the eerie silence of the cavern,
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