toward the south (Fig. 1). First a wall of stalagmite barred our road; then we had to scramble over a series of pot-holes, some of which were full of water; and we then entered the passage of the bowlders, enormous blocks fallen from the roof or the walls and
carried along by the waters, worn and polished, which were chaotically piled upon one another along the rapid descent (Couloir des Gours and Gros Éboulis). Around these blocks we walked upon a shingle of small worn fragments of stalactite, flattened by the violence of the waters. There was still a pot-hole more than six feet deep separated from another lake by a mass of stalagmites on which we would have to balance ourselves in order to hoist the boat. It was so narrow that we could not do this, and we had to invent a novel system of ballistics to get the Microbe, which was upward of two hundred yards away, through the difficult passage. And it was very vexing to be stopped, for in a moment the river turned to the west, toward the Rochemale Spring, which we regarded as an issue of the Midroï. With all requisite precautions we took up specimens of the water from this pot-hole, which we planted in culture tubes for the microbiological researches we were prosecuting on the water of caverns. The thermometer, which marked 29° C. outside, had fallen to 14° C.