VOLCANOES, THEIR ACTION AND DISTRIBUTION. 51 



up and open, forming a gaping fissure, within which incandescent mat- 

 ter was visible. Masses of stone and vast quantities of pumice and 

 mud were then thrown up to a great height for two days and nights, 

 and, falling on the sides of the vent, formed a great mound, which 

 was climbed up by adventurous persons on the third day, a quiet one. 

 The ejections were resumed on the next day, when several persons 

 who undertook to climb the hill were killed or injured, but ceased on 

 the seventh or eighth day. The mass of the hill, which is four hun- 

 dred and forty feet above the sea, was chiefly composed of the materials 

 which were thrown out during the first two days and nights. It con- 

 sists of scoriae, lapilli, and dust, and is now covered with a thick growth 

 of pines. The crater is marked by a steep, cup-shaped depression, the 

 bottom of which is but little above the level of the sea. The district 

 in which this mountain is situated contains a great number of hills, 

 strikingly resembling it, some of which are larger, some smaller than 

 it, but all so similar that " no stranger visiting the district, without 

 previous information on the subject, would suspect the fact that, 

 while all the other hills of the district have existed from time imme- 

 morial, and are constantly mentioned in the works of Greek and Ro- 

 man writers, this particular hill of Monte Nuovo came into existence 

 less than three hundred and fifty years ago." 



The form of the cones is modified by the character of the materials 

 thrown out, by the action of the weather, and by repeated eruptions. 

 Loose material, scorias and lapilli, roll till they reach a position of 

 rest, and leave a more or less regular cone. Very liquid lavas flow to 

 great distances, resting at a very slight slope, as in the volcanoes of 

 Hawaii, where, with a slope of only six or eight degrees, the mountains 

 have a diameter of seventy miles at their base, and reach a height of 



Fig. 8. Outlines op Lava-Cones. 1. Manna Loa, in Hawaii, composed of fluid lava ; 2. The 

 Schlossberg of Teplitz, Bohemia, composed of very imperfectly fluid or viscid lava. 



fourteen thousand feet. If, on the other hand, the lava is only imper- 

 fectly liquid, it tends to accumulate around the vent and form a more 

 or less steep-sided bulbous mass, as in number two of the figure (Fig. 8). 

 The shape of the cone may undergo changes during an eruption, as in 

 the accompanying outlines of Vesuvius (Fig. 9). Most of the great vol- 

 canic mountains belong to the class of " composite cones," and are built 



