A little beyond the last pool the running water suddenly vanished.  We looked around to see if it had taken any side passage; but no:  it simply disappeared into the earth, although no hole was perceptible in its stony channel.  It passed by infiltration into some lower gallery, where the light of a candle had never shone, and is never likely to shine.  But we had not reached the end of the cavern, although the passage became so low that we had now really to go down on all-fours in order to proceed.  We had not to keep this posture long, for again the roof rose, although to no great height.  We walked on about fifty yards or more, and then came to the end.  There was no opening anywhere except by the way we entered.  We were like flies that had crawled into a bottle, and a very unpleasant bottle it might have proved to us.  We noticed—­at first with some surprise—­that, although there was not a drop of water now in this cul-de-sac, our feet sank into damp sand that had evidently been carried there by water.  Sticks were also lying about, and the walls up to the roof were covered with a muddy slime.  It was evident that this hole had been filled with water, and not very long ago; probably the last thunderstorm accounted for the signs of recent moisture.  While we were talking about this, a strange, muffled, moaning sound reached our ears.  We looked at one another over the tops of two candles.  ‘Thunder,’ said my companion.  In a few minutes the same dismal moan, long drawn out, came down the cavern, which acted like a speaking-tube between us and the outer world, and conveyed a timely warning.  Was it in time?  We were not quite sure of this, for as we issued from the cul-de-sac we heard the water coming down the rocks with a very different voice from that which it had not many minutes before.  It was clear that the storm was beginning to tell upon the stream, and if the rain had been falling for half an hour, as I had already seen it fall in the Quercy, we might find the work of recrossing those pools and climbing up the cascades anything but cheerful.  Already where we had been able to walk on dry stones the water was now up to our ankles.  The first cascade to surmount was the worst.  We decided to try it on the side opposite to the one by which we descended, for we observed a jutting and highly-polished piece of stalagmite, which promised to help the manoeuvre.  One went first, and the other waited, holding the candle.  I was in the rear.  When my companion had reached the top of the cascade, I threw him the coil of rope—­a useless encumbrance, as it happened—­and in so doing put out the candle.  Before I was sure that I had a dry match upon me, I failed to seize the humour, although I felt the novelty of the situation.  During those seconds of uncertainty, the sound of the water—­really fast increasing—­seemed to become a deafening roar.  However, we both had dry matches, and were able to relight our candles; but it might have been otherwise, wet as we were.  Without light we should have been as helpless beneath those rocks as mice in a pitcher.  The first cascade conquered, we felt much more comfortable, for the picture of being washed into that cul-de-sac had flashed upon the mind of each.