412 



HISTORY OF SCIENCE. 



Fire 



Region supposed to be occupied by a mass 

 kept in a semi-fluid state by internal heat, and 

 containing in this condition granite, gneiss, 

 porphyry, whinstone, basalt, etc. 



FIG. 186. 



Granite, basalt, etc., were the original matter of the earth, or have since 

 been formed by subterraneous action. On the granitic nucleus which 

 had become covered with the ocean were found beds of limestone, 

 marble, and chalk from the exuvice of marine animals. The globe 

 was then rent by the violence of the confined central fires, islands and 

 continents were heaved up, consisting in some parts of granite, in 

 others of lava or molten granite, in others of stratified limestone, and 

 great valleys and depressions were formed, into which the ocean re- 

 treated. On some parts of these continents and islands morasses were 

 formed by the accumulation of vegetable matter, and from these mo- 

 rasses, heated by fermentation, were produced clay, marl, coal, etc. 

 During the elevation of the mountain masses many deep fissures were 

 produced, and in these many of the metals and minerals were depo- 

 sited, partly from materials descending from above, and partly from 

 vapours raised from below by the subterranean fires. By rain and 

 snow precipitated on the summit of the new mountains, still glowing 

 with heat, their materials were cracked into innumerable fragments, 

 which descended into the valleys, and were there rolled about in the 

 vast rivers, and so formed the great beds of gravel. Subsequent earth- 

 quakes and convulsions at various periods produced local derange- 

 ments, so that the gravel which was once in the beds of the rivers was 

 in some cases raised to the tops of the mountains. The coal deposit 

 was washed down into the valleys and sea from the high masses, and 

 became covered with clay or gravel, or limestone deposit of marine 

 shells, etc. 



