Fig. 134.—The central cone of Vesuvius as it appeared after the eruption of 1906, but with the earlier profile indicated. The truncation represents a lowering of the summit by some five hundred feet, with corresponding increase in the diameter of the crater (after Johnston-Lavis).
When the heavy curtain of ash, which now for a number of succeeding days overhung all the circum-Vesuvian country, began to lift ([Fig. 133]), it was seen that the summit of the cone had been truncated an average of some 500 feet ([Fig. 134]). All the slopes and much of the surrounding country had the aspect of being buried beneath a cocoa-colored snow of a depth to the northeastward of several feet, where it had drifted into all the hollow ways so as almost to efface them ([Fig. 135]). More than thrice as heavy as water, the weak roof timbers of the houses at the base of the mountain gave way beneath the added load upon them, thus making many victims. Inasmuch, however, as the ash-fall partakes of the same general characters as in eruptions from cinder cones, we may here give our attention especially to the streams of lava which issued upon the opposite flank of the mountain ([Fig. 136]).
Fig. 135.—A sunken road filled with indrifted cocoa-colored ash from the Vesuvian eruption of 1906.
Fig. 136.—View of Vesuvius taken from the southwest during the waning stages of the eruption of 1906. In the middle distance may be discerned the several lava mouths aligned upon a fissure, and the courses of the streams which descend from them. In the foreground is the main lava stream with scoriaceous surface (after W. Prinz).
————
The main lava stream descended the first steep slopes with the velocity of a mile in twenty-five minutes, about the strolling speed of a pedestrian, but this rate was gradually reduced as the stream advanced farther from the mouth. Taking advantage of each depression of the surface, the black stream advanced slowly but relentlessly toward the cities at the southwest base of the mountain. With a motion not unlike that of a heap of coal falling over itself down a slope, the block lava advances without burning the objects in its path ([Fig. 137]).
