GROWTH OF GEOLOGY. 257 



found in submerged forests and even villages. 

 Proofs of the gradualness of these changes prevailed 

 against theories of sudden oscillations. Almost all 

 the eminent geologists of the century have contrib- 

 uted to the subject. 



While the prevailing interpretation has always 

 been that the local level of the land changed while 

 that of the sea remained constant, there have been 

 many who have insisted that the sea-level may also 

 change, — in consequence of great subsidences, accum- 

 ulations of sediment, formation of polar ice-caps, 

 and so on. 



The complications of the problem and the difficul- 

 ties in the face of any general theory are recognised 

 in the splendid work of Suess (Antlitz der Erde) 

 which touches the high-water mark in this depart- 

 ment of geology. 



Mountain-Mahing. — Far ahead of his time, Steno, 

 in 1669, tried to interpret the hills and valleys of 

 Tuscany in terms of the collapse of the earth^s 

 crust, the uplift of stratified rocks, and the accum- 

 ulation of volcanic material. Long afterwards, 

 Hutton found satisfaction in referring elevations 

 of the crust to the expansive power of the subterra- 

 nean heat, to which volcanoes acted as safety valves. 

 Leopold von Buch and Poulett-Scrope were among 

 those who upheld LIutton's theory, and sought to 

 improve upon it. From 1829 to 1852 Elie de Beau- 

 mont illustrated the important idea that the gradual 

 cooling of the earth led to the crumbling of the crust. 

 James Hall in 1859 pointed out that the gradual 

 accumulation of sedimentary masses in areas of 

 depression may be associated with a corresponding 

 elevation of mountain chains elsewhere. Dana 

 returned to the consideration of the effects produced 

 17 



