INDEX. 



487 



Columbus determines astronomi- 

 cally a line of no variation, 54 ; 

 notice of an eruption on Tene- 

 riffe, by, 477. 



Comangillas, Aguas de, a hot 

 spring, 197. 



Commotion, waves of, in earth- 

 quakes, 171; theory of, 172; 

 attempt to explain the rotatory 

 shocks experienced in Calabria, 

 172. 



Commotions of the earth in earth- 

 quakes often confined within 

 narrovr limits, 182. 



Comoro islands, burning volcano 

 in the, 384. 



Compass. See Mariner's Compass. 



Compression, polar, 29. 



Couchagua, a volcano, 275. 



Conical volcanic mountains, 239. 



Conseguira, eruption of, 274. 



Copiapo, destruction of the town 

 of, 288. 



Coquimbo, volcano of, 288. 



Coral islands, number of, in the 

 Pacific, according to Dana, 390. 



Corcovado, Volcan de, 290. 



Cordilleras. See Andes. 



Corea, volcanoes of, 376. 



Cosima, small elevation of the 

 volcano of, 245. 



Costa, Col. A., his experiments on 

 mean annual temperature, 41. 



Cotopaxi, mineralogical composi- 

 tion of, 343. 



Craters of elevation, 226 ; distin- 



fuished from true volcanoes, 

 27. See also Volcanoes. 

 Crozet's group, traces of former 



volcanic action in, 387. 

 Crust of the earth, considerations 



on its varying thickness, 439. 

 Crystallized minerals of the Maars, 



234 ; greater number found on 



Vesuvius, 235. 

 Cueva de Autisana, 332. 

 Cyclades, volcanic phenomena in 



the, 267. 



Dana, James, his valuable re- 



searches in the Pacific, 388 ; 

 his grouping of the basaltic and 

 coral islands, 390 ; on the vol- 

 canoes of the Sandwich Islands, 

 392. 



Darwin, Charles, his enlarged 

 views on earthquakes and erup- 

 tions of volcanoes, 288 ; general 

 acknowledgment of obligations 

 of science to, 389. 



Dasar, sand-lakes of, 482 



Dechen, H. von, on volcanic phe- 

 nomena in the Eifel, 236 



Declination. See Magnetism. 



Degree, table of the increase in 

 length of the, from the equator 

 to the pole, 17. 



Demavend, volcano of, 356, 357 ; 

 question of its altitude, 356. 



Density of the earth, experiments 

 to determine, 30; Airy 's results, 

 vii. 



Detritus dykes, 331. 



Deville, on the structure and 

 colour of the mass in certain 

 volcanoes, 463. 



Devonian slate, 231. 



Diablo, Monte del, in California, 

 416. 



Diamagnetism, its discovery by 

 Faraday, 49, 78. 



Dio Cassius on the eruptions of 

 Vesuvius, 427. 



Diodorus Siculus on the Phlegrsean 

 fields, 428. 



Disturbances, magnetic, table of, 

 134. 



Djebel el Tir, a volcano, 356. 



Dome-shaped and bell-shaped 

 mountains peculiar aspect given 

 by, to the landscape, 229. 



Domite, origin of the term, 450. 



Dry fog of the summer of 1783, 

 421. 



Duperrey, his observations on the 

 magnetic equatoi*, 104. 



Earth, its size, configuration and 

 density, vii, 9 ; interior heat, 

 34, 246 ; magnetic activity, 49; 



