266 HISTORY OF GEOLOGY AND PALEONTOLOGY. 



hypothesis of Elevation-Craters had to be given up, and with it 

 the classification of volcanoes into "True" or "Eruptive 

 Volcanoes" and "Craters of Elevation" which had been so 

 long associated with the names of Buch and Humboldt. 



Karl von Seebach then proposed a new classification ; he 

 distinguished as Stratified Volcanoes those which have a crater 

 and are composed of layers of lava and loose volcanic ash and 

 scoriae ; as Homogeneous Volcanoes those which have no crater 

 and no loose ejected material but have originated as massive 

 effusions and have the form either of volcanic domes or 

 horizontal sheets. The homogeneous volcanoes have been 

 formed by viscous lavas, the stratified volcanoes by more 

 liquid lavas strongly impregnated with vapour and gases. 

 This sub-division into stratified and homogeneous volcanoes 

 was adopted in most of the text-books, and was afterwards 

 more firmly established by Sir Archibald Geikie and Dr. Reyer. 



It is beyond the scope of this volume to enter into the 

 extensive descriptive literature which is occupied chiefly with 

 the configuration, composition, geographical distribution, erup- 

 tive phenomena, and history of the volcanoes. Humboldt 

 published an epitome of all known volcanoes, and the works 

 of Hoff, Daubeny, Scrope, and others supplemented the 

 earlier lists. 



Vesuvius is the best known volcano in the world, and 

 during the prolonged controversy about elevation-craters 

 was made more than ever the subject of close attention. 

 Monticelli for thirty years, from 1815 to 1845, took observa- 

 tions on Vesuvius and its discharges; from 1855 to 1892 

 Palmieri published regular reports of the observations made 

 in the Observatory of this mountain. Angelo Scacchi and 

 Gerhard vom Rath examined the minerals of Vesuvius ; the 

 lavas were described by Justus Roth, the author of a 

 monograph of Mount Vesuvius (1857), and by C. W. C. Fuchs. 

 The last-named author also mapped and described the Island 

 of Ischia (1872). Within recent years Vesuvius has been con- 

 stantly under observation by Johnston Lavis and Matteucci. 



The name of Baron Sartorius von Waltershausen is indelibly 

 associated with Etna. His geological map (scale, i : 50,000) 

 of this volcano appeared in 1861, and his descriptive text was 

 published posthumously in 1880 by Lasaulx. The scrupulous 

 accuracy and exhaustive details of both map and text amply 

 entitle them to their rank as the fundamental work on Etna. 



