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196 things lie is looking at) a good deal, and will enable him to steer clear of many difficulties against which he might otherwise blindly run, it will seldom allow one to pronounce positively upon the practicability or impracticability of the whole of the route. No living man, for example, can pronounce positively from a distance in regard to rocks. Those just mentioned are an illustration of this. Three of the ablest and most experienced guides concurred in thinking that they would be found very difficult, and they proved to be of no difficulty whatever. In truth, the sounder and less broken up are the rocks, the more impracticable do they usually look from a distance; while soft and easily rent rocks, which are often amongst the most difficult and perilous to climb, very frequently look from afar as if they might be traversed by a child.

It is possible to decide with greater certainty in regard to the practicability of glacier. When one is seen to have few open crevasses (and this may be told from a great distance), then we know that it is possible to traverse it; but to what extent it, or a glacier that is much broken up by crevasses, will be troublesome, will depend upon the width and length of the crevasses, and upon the angles of the surface of the glacier itself. A glacier may be greatly crevassed, but the fissures may be so narrow that there is no occasion to deviate from a straight line when passing across them; or a glacier may have few open crevasses, and yet may be practically impassable on account of the steepness of the angles of its surface. Nominally, a man with an axe can go anywhere upon a glacier, but in practice it is found that to move freely upon ice one must have to deal only with small angles. It is thus necessary to know approximately the angles of the surfaces of a glacier before it is possible to determine whether it will afford easy travelling, or will be so difficult as to be (for all practical purposes) impassable. This cannot be told by looking at glaciers in full face from a distance; they must be seen in profile; and it is often desirable to examine them both from the front and in profile,—to do the first to study the direction of the crevasses, to note where they are most and least