THE CRUST OF THE EARTH. 



the Mezenc, and the Megal, upon the borders of the Velay and the 

 Vivarais. They prevail also on the right bank of the Rhine, and 

 the Siebengebirge. They form immense groups in Hungary and 

 Transylvania, in the Caucasus, in Greece, where their continuation 

 appears in the islands of Milo and Argentiera and extends to the 

 centre of Santorin. Th^y reappear in the Lipari Islands, in the 

 Campania, in the Euganean mountains, in the Azores, in the 

 Canaries, in South America, where the loftiest heights of the Cor- 

 dilleras are composed of tjiem, in Central Asia, and in many of the 

 islands extending along its coast to Kamschatka. 



98. The trachytic formation presents itself not only in isolated 

 mounds, narrow bands, and sheets scattered over the surface of the 

 globe like those of the basalt, but also in vast mountains, gene- 

 rally assembled in large groups, forming the most elevated masses 

 and covered with terrific asperities. Their flanks are torn by 

 precipitous valleys and deep gorges. 



99. The matter composing these vast accumulations was evi- 

 dently ejected from the bowels of the earth by the disruption of 

 the crust, issuing in a state of pasty fusion through the opening 

 thus made in the super jacent stratified rocks, fig. 40. 



Fig. 40. 



80 



