110 THE WONDERS OF GEOLOGY. LecT. I. 



rounding country being very numerous, and a hot spring still 

 existing on the land-side of the ruins. The change of level 

 is therefore easily accounted for, by supposing the temple 

 to have been built on the surface, when the rocks beneath 

 were expanded by the effects of a high temperature, and 

 that they subsequently contracted by slow refrigeration. 

 When this contraction had reached a certain point, if a 

 fresh accession of heat from the neighbouring volcano took 

 place and increased the temperature of the strata, they 

 would again expand, and thus raise the ruins to their 

 present level. 



Mr. Babbage carries out these view r s to explain the 

 elevation of continents and mountain ranges, assuming the 

 following facts as the basis of his theory : — 



1st. As we descend below the surface of the earth, the temperature 

 increases. 



2dly. Solid rocks expand by being heated, but clay and some other 

 substances contract. 



3dly. Eocks and strata of dissimilar characters present a corre- 

 sponding difference as conductors of caloric. 



4thly. The radiation of heat from the earth varies in different parts 

 of its surface ; according as it is covered by forests, mountains, 

 deserts, or water. 



5thly. Existing atmospheric agents, and other causes, are constantly 

 changing the condition of the surface of the globe. 



Thus wherever a sea or lake is filled up by the wearing 

 down of the adjacent lands, new beds are formed, conduct- 

 ing heat much less quickly than the water ; while the 

 radiation from the surface of the new land will also be 

 different. Hence, any source of caloric, whether partial 

 or central, which previously existed below that sea, must 

 increase the temperature of the strata underneath to a much 

 higher degree than before, because they are now protected 

 by a bad conductor ;* and their expansion must therefore 



* Sir John Herschel observes, that this process is precisely similar 

 to that by which a great coat, in a wintry day, increases the feeling of 



