232 VOLCANIC ACTION. SECT. XXV. 



little depth for years after its surface is cool. "Whatever the 

 radiation of the earth might have been in former times, certain 

 it is that it goes on very slowly in our days ; for M. Fourier 

 has computed that the central heat is decreasing from radiation 

 by only about the s^th part of a degree in a century. If so, 

 there can be no doubt that it will ultimately be dissipated ; but 

 as far as regards animal and vegetable life, it is of very little 

 consequence whether the centre of our planet be liquid fire or 

 ice, since its condition in either case could have no sensible effect 

 on the climate at its surface. The internal fire does not even 

 impart heat enough to melt the snow at the poles, though 

 nearer to the centre than any other part of the globe. 



The immense extent of active volcanic fire is one of the causes 

 of heat which must not be overlooked. 



The range of the Andes from Chile to the north of Mexico, 

 probably from Cape Horn to Behring Straits, is one vast dis- 

 trict of igneous action, including the Caribbean and the West 

 Indian Islands on one hand ; and stretching quite across the 

 Pacific Ocean, through the Polynesian Archipelago, the New 

 Hebrides, the Georgian and Friendly Islands, on the other. 

 Another chain begins with the Aleutian Islands, extends to 

 Kamtschatka, and from thence passes through the Kurile, 

 Japanese, and Philippine Islands, to the Moluccas, whence it 

 spreads with terrific violence through the Indian Archipelago, 

 even to the Bay of Bengal. Volcanic action may again be 

 followed from the entrance of the Persian Gulf to Madagascar, 

 Bourbon, the Canaries, and Azores. Thence a continuous 

 igneous region extends through about 1000 geographical miles 

 to the Caspian Sea, including the Mediterranean, and extending 

 north and south between the 35th and 40th parallels of latitude ; 

 and in central Asia a volcanic region occupies 2500 square geo- 

 graphical miles. The volcanic fires are developed in Iceland in 

 tremendous force ; and the antarctic land discovered by Sir 

 James Eoss is an igneous formation of the boldest structure, 

 where a volcano in high activity rises 12,000 feet above the 

 perpetual ice of these polar deserts, and within 19 of the 

 south pole. Throughout this vast portion of the world the sub- 

 terraneous fire is often intensely active, producing such violent 

 earthquakes and eruptions that their effects, accumulated during 

 millions of years, may account for many of the great geological 



