In the Middle Ages, however, geology was an undiscovered science, and the human mind was compelled—­perhaps with much advantage to itself—­to seek supernatural causes in order to explain the mysterious phenomena of nature, many of which, so far as subsidiary causes are concerned, have ceased to be mysterious.  This spot—­called the Pas de Souci—­has, therefore, its poetic and miraculous legend.  St. Enimie, when she established her convent near the fountain of Burlats, higher up the Tarn, interfered with the calculations of the devil, who had found the numerous orifices in this region communicating with the infernal kingdom exceedingly convenient for his terrestrial enterprises.  He therefore lost no time in entering upon a tug-of-war with the saintly interloper.  But she was more than a match for him.  Her nuns, however, were of weaker flesh, and so he tried his wiles upon them.  Their devotions and good resolutions were so much troubled by the infernal teaser of frail humanity that St. Enimie, realizing the great danger, rose to the occasion.  One day or night she caught the devil unawares in the convent and tried to chain him up; but he was too strong or too crafty for the innocent virgin, and made his escape down the gorge of the Tarn, intending to reach his own fortress by the hole down which the stream plunges at the Pas de Souci, and which the peasant believes existed from the beginning of the world.  St. Enimie followed at his heels as closely as she could, and he led her a wild scamper over the rocks.  She hoped that St. Ilere, her confessor, who lived in a cavern of the gorge, would stop the fiend in his flight, but the saint was so busy praying that he did not notice the arch-enemy as he sped on his frantic course.  St. Enimie was quite out of breath and ready to drop from exhaustion when she drew near the Pas de Souci, a little in the rear of the tormentor of souls, and he was just about to plunge into the gulf.  The saint threw herself upon her knees, and exclaimed:  ’Help me, O ye mountains and crags!  Stop him, fall upon him!’ Thereupon there was a great commotion of the ancient rocks far above under the calm sky, and they fell, one after the other, with a frightful crash.  It was, however, the immense block, since named La Sourde, that stopped the devil; the others he shook off as if they had been pebbles.  When La Sourde struck him it was more than he could contend with, and it flattened him out.  The Needle Rock was just about to tumble, when La Sourde cried out:  ’Hold on, my sister!  You need not trouble yourself; I have him fast!’ This explains why the Needle Rock has ever since looked so undecided.  For centuries La Sourde bore the impress of a sanguinary hand, left upon it by Satan in his frantic efforts to get free, but some years ago it was washed away by an exceptionally high flood.