RISE OF MOLTEN ROCK TO THE EARTH'S SURFACE 133 



FIG. 135. A sunken road filled with in- 

 drifted cocoa-colored ash from the Vesu- 

 vian eruption of 1906. 



lava which issued upon the 

 opposite flank of the moun- 

 tain (Fig. 136). 



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 far- 

 ther from the mouth. Tak- 

 ing advantage of each depression of the surface, the black stream 

 advanced slowly but relentlessly toward the cities at the south- 

 west base of the mountain. With a motion not unlike that of a 

 heap of coal falling over itself down a slope, the block lava 



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). 



FIG. 137. The main lava stream of 

 1906 advancing upon the village of 

 Boscotrecase. 



FIG. 138. An Italian pine snapped off 

 by the lava and carried forward upon 

 its surface as a passenger (after Haug). 



