714 ON THE VOLCANO OP TAAL, 



water, they often become the site of lakes. The beautiful circular 

 lake of Laach, in the Rhine Provinces, with the numerous similar 

 examplesof Central Italy — Albano, Nemi, Bracciano, and Bolsena — 

 the lakes of Campi Phlegraei (Agnano, Avernus, &c.), and some 

 similar lakes in the Auvergne, may be adduced as examples of 

 crater-rings which have become the site of lakes." 



" One of the most beautiful of the crater-lakes in the Auversfiie is 

 Lac Paven, which lies at the foot of a scoria-cone, Mont Chalme, 

 and is itself surrounded by masses of ejected materials. The 

 crater-lake of Bagno, in Ischia, has had a channel cut between it 

 and the sea, so that it serves as a natural harbour. The lake of 

 Gustavila, in Mexico, is an example of a crater-lake on a much 

 larger scale." 



" In many of these crater-rings the diameter of the circular space 

 enclosed by them is often very great indeed as compared with the 

 height of the walls." 



" Two of the largest crater-rings in the world are found in Central 

 Italy, and are both occupied by lakes, the circular forms of which 

 must strike every observer." 



"TheLago Bracciano, which lies to the north-west of Rome, is a 

 circular lake six and a-half miles in diameter, surrounded by hills, 

 which at their highest point I'ise to the height of 1,486 ft. above 

 the sea, while the sui'face of the waters of the lake is 540 ft. above 

 the sea-level. The Lago di Bolsena is somewhat less perfectly 

 circular in outline than Lago di Bracciano ; it has a length from 

 north to south of ten and a-quai'ter miles, and a breadth from east 

 to west of nine miles. The surface of the waters of this lake is 

 962 ft. above that of the waters of the Mediterranean. The lake 

 of Bolsena, like that of Bracciano, is surrounded by hills composed 

 of volcanic materials ; the highest points of this ring of hills rise 

 to elevations of 684, 780, and 985 ft. respectively above the waters 

 of the lake."* 



But if these lakes are distinguished for anything, it is for the 

 singular purity and clearness of their waters. Without citing 

 other instances, I may give one which belongs to Australia, 



• Judd on Volcanoes, p. 171. 



