To turn from rock to snow climbing. Accidents are constantly happening on glaciers; yet the observance of the most elementary precautions ought to make such accidents absolutely impossible. An open glacier, of course, is safe enough under any circumstances. The one thing needful is to look where you are going and not try to make flying leaps across crevasses. But even when the crevasses are masked by snow all danger may still quite easily be obviated. The simple rule is that the party crossing the glacier should never consist of less than three, and that the three should be roped together in such a way that, if one falls into a crevasse, the other two can pull him out. And this, of course, involves the further rule that the rope must always be kept taut, so that a fall may be checked before it has gained an impetus which would make it difficult to resist. [Illustration: PASSAGE OF A CREVASSE, MONT BLANC.] By experience it is possible to recognize a crevasse, with tolerable accuracy, in spite of its snow covering; and by sounding with the ice-axe before treading on it, one ought to be able to tell whether the snow bridge will bear one's weight. But, now and again, it will happen that the most experienced man's judgment is at fault. Relying upon their instinctive perception of such things, the Swiss peasantry constantly traverse glaciers alone in mid-winter. But accidents are very frequent, and when guides, tourists, or porters have attempted the same thing, accidents have constantly befallen them as well. As an illustration may be quoted the case of a reporter, who foolishly ventured to return alone over the Loetschen pass. A snow bridge broke and he fell into a crevasse, where only his knapsack saved him from breaking his neck. He lay on his back, wedged into the ice in such a way that he could not move, and it was by the merest accident that he was discovered in time, and rescued by a party journeying in the same direction. So much, as Herodotus would say, for crevasses. Another serious Alpine danger is the danger of bad weather; and bad weather, as Leslie Stephen has pointed out, may make the Righi at one time as dangerous as the Matterhorn at another. To a certain extent, of course, bad weather can be foreseen; but meteorology is not yet an exact science, and even the acquired instinct of the guides is sometimes at fault, so that grave mistakes, often followed by fatal consequences, are made almost every year. DANGERS OF BAD WEATHER. Mont Blanc is probably the mountain in which bad weather makes the greatest difference. On a fine day, the ascent of it is scarcely more dangerous than the ascent of Primrose Hill; but in a storm you will lose your way, and wander round and round, until you sink down exhausted, and freeze to death.