The place was the Piz Morteratsch, in the Engadine, and the time the month of July, 1864. Professor Tyndall's companions were Mr. Hutchinson and Lee Warner, and the guides Jenni and Walter. Jenni was at that time the dictator of Pontresina, and he seems to have set out with the deliberate intention of showing his _Herren_ how great and brave a man he was. The ascent was accomplished without any incident of note. On the way down the party reached a broad _couloir_, or gully, filled with snow, which had been melted and refrozen, so as to expose a steeply sloping wall of ice. The question arose whether it would be better to descend this wall of ice, or to keep to the steep rocks by the side of it. Professor Tyndall preferred the rocks; Jenni inclined towards the slope, and started to lead the way upon it. [Illustration: THE NEEDLE OF THE GIANTS AND MONT BLANC.] There was a remonstrance from the professor: "Jenni," he said, "do you know where you are going? The slope is pure ice." "I know it," the guide replied, "but the ice is quite bare for a few rods only. Across this exposed portion I will cut steps, and then the snow which covers the ice will give us a footing." So they started, roped together, Jenni in front, Mr. Tyndall next, followed by Mr. Hutchinson, Mr. Lee Warner, the one inexperienced member of the party, and, last of all, the guide Walter, ready to check on the instant any false step that Mr. Lee Warner might make. After a few steps Jenni began to see that the slope was less safe than he had supposed. He stopped and turned round to speak a word of warning to the three men above him. "Keep carefully in the steps, gentlemen," he said; "a false step here might start an avalanche." And, even as he spoke, the false step was made. There was a sound of a fall and a rush, and Professor Tyndall saw his friends and their guide, all apparently entangled, whirled past him. He planted himself to resist the shock, but it was irresistible; he, too, was torn from his foothold, and Jenni followed him, and all five found themselves riding downwards, with uncontrollable speed, on the back of an avalanche, which a single slip had started. "Turn on your face, and grind the point of your axe or baton through the moving snow into the ice"--that is the golden rule for cases of the kind, the only way in which the faller can do anything to arrest his speed. But it seldom avails much, and in this instance it availed nothing.