RISE OF MOLTEN ROCK TO THE EARTH'S SURFACE 139 



It was streams of this sort that buried the city of Herculaneum 

 after the explosive eruption of 79 A.D. 



After the mud flows have occurred, the Vesuvian cone, like all 

 similar volcanic cones under the same conditions, is found with 

 deep radial corrugations (Fig. 144), such as were long ago de- 

 scribed as " barrancoes " and supposed to support the " elevation 

 crater " theory of volcano formation. 



The dissection of volcanoes. To the uninitiated it might ap- 

 pear a hopeless undertaking to attempt to learn by observation 

 the internal structure of a volcano, and especially of a complex 

 volcano of the composite type. The earliest successful attempt 

 appears to have been made by Count Caspar von Sternberg in 

 order to prove the cor- 

 rectness of the theory 

 of his friend, the poet 

 Goethe. Goethe had 

 claimed that a little 

 hill in the vicinity of 

 Eger, on the borders 

 of Bohemia, was an ex- 

 tinct volcano, though 

 the foremost geologist 

 of the time, the fa- 

 mous Werner, had pro- 

 mulgated the doctrine 

 that this hill, in common with others of similar aspect, originated 

 in the combustion of a bed of coal. The elevation in question, 

 which is known as the Kammerbuhl, consists mainly of cinder, 

 and Goethe had maintained that if a tunnel were to be driven 

 horizontally into the mountain from one of its slopes, a core or 

 plug of lava would be encountered beneath the summit. The 

 excavations, which were completed in 1837, fully verified the 

 poet's view, for a lava plug was found to occupy the center of 

 the mass and to connect with a small lava stream upon the side 

 of the hill (Fig. 145). 



It is not, however, to such expensive projects that reference 

 is here made, but rather to processes which are continually going 

 on in nature, and on a far grander scale. The most important 

 dissecting agent for our purpose is running water, which is con- 



FIG. 145. The Kammerbiihl near Eger, showing 

 the tunnel completed in 1837 which proved the 

 volcanic nature of the mountain (after Judd). 



