Davis.] 
880 
[January 18, 
the latter, Agnano and Averno, also the Piano di Quarto and the 
Pianura, similar craters but not well enough enclosed to hold 
lakes. North of Pome there are several lakes of larger size — 
Bracciano, ten miles in diameter, Bolsena, six and a half miles, 
and some others — as to the origin of which different opinions are 
held : one observer considers them of explosive origin, 1 another, 
the result of subsidence. 2 In Auvergne, lakes in the Puys du Bar, 
and de St. Sandoux, the Lacs de la Godivelle, de Monsiniere, 
and others come under this species. 3 
About Auckland, New Zealand, is a region extremely rich in 
lakes of this species, 4 and other volcanic countries afford further 
examples. 5 
Many volcanic lakes are peculiar from their contents. On the 
Island of Dominica there is a hot lake in a crater ; at the edge its 
temperature is 180° F., and in the middle it boils 6 . We might 
mention also those craters occupied by gaseous lakes strongly 
charged with carbonic acid, so as to render them deadly to all 
animal life; such a one is known in Java; its bottom is strewn 
with skeletons of animals that ventured over its fatal walls. 7 
Occasionally these lakes lie at great elevations, as in the crater of 
Toluca (Mexico), 11,490 ft., and Elbruz (Caucasus), 18,500 ft. above 
the sea. 8 Contrasted with these, are the isolated, oceanic crater- 
rings that appear just above sea-level ; one side is generally 
breached, giving an entrance to the quiet lake-harbor within. 9 
In our own country, while there have been large areas of vol- 
1 Judd, The Great Crater lakes of Central Italy, Geol. Mag. n, 1875, 349-356. 
2 G. v. Rath, Deutsch. geol. Ges. Zft., xvm, 1866, 516. 
3 A. v. Lasaulx, Niederrh. Ges. Sitz’b., xxv, 1868, 57. 
4 Heaphy, Geol. Soc. Journ. xvi, 1860, 242-252. Hochstetter, Peterm. Geog. Mittheil. 
1862, map 6. Geologie von Neu Seeland, 160. 
5 F. Junghuhn, Java, ii, 133, 902, describes eighteen crater lakes, of which eleven 
are acid, in subactive volcanoes, and seven fresh, in extinct cones. G. Hartung, Die 
Azoren, 311, describes and figures a number of caldeiras, one of which was formed 
in 1563. 
6 Nature, 1889, June, p. 296. 
7 Roy. Geogr. Soc. Journ. n, 1831, 60. 
3 Humboldt, Cosmos, iv, 1858, 275. 
9 Deception Island, among the South Shetlands, Roy. Geogr. Soc. Journ., i, 1830. 
St. Paul’s in the Southern Indian Ocean, Wien Geogr. Ges. Mitth. 1857, 146 ; A. 
Cazin, Club Alpin Fran?. Ann. n, 1875, 542. Barren Island in the Bay of Bengal, 
Geol. Mag. 1879, 16. 
