It is possible to decide with greater certainty in regard to the practicability of glaciers. 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 numerous; and the second to see whether its angles are moderate or great. Should they be very steep, it may be better to avoid them altogether, and to mount even by difficult rocks; but upon glaciers of _gentle_ inclination, and with few open crevasses, better progress can always be made than upon the _easiest_ rocks. So much to explain why we were deceived when looking at the Brèche de la Meije from the Aiguille de la Sausse. We took note of all the difficulties, but did not pay sufficient attention to the distance that the Brèche was south of La Grave. My meaning will be apparent from the accompanying diagram, Fig. 1 (constructed upon the data supplied by the French surveyors), which will also serve to illustrate how badly angles of elevation are judged by the unaided eye. [Illustration: Diagram to show angle of summit of Meije, etc.] The village of La Grave is just 5000 feet, and the highest summit of the Meije is 13,080 feet above the level of the sea. There is therefore a difference in their levels of 8080 feet. But the summit of the Meije is south of La Grave about 14,750 feet, and, consequently, a line drawn from La Grave to the summit of the Meije is no steeper than the dotted line drawn from *A* to *C*, Fig. 1; or, in other words, if one could go in a direct line from La Grave to the summit of the Meije the ascent would be at an angle of less than 30°. Nine persons out of ten would probably estimate the angle on the spot at double this amount.(102)