A HISTORY OF SCIENCE 



large areas, due to earthquakes, was brought forward in 

 abundance. Cumulative evidence left it no longer open 

 to question that such oscillatory changes of level, either 

 upward or downward, are quite the rule, and it could 

 not be denied that these observed changes, if continued 

 long enough in one direction, would produce the highest 

 elevations. The possibility that the making of even 

 the highest ranges of mountains had been accom- 

 plished without exaggerated catastrophic action came 

 to be freely admitted. 



It became clear that the supposedly stable-land sur- 

 faces are in reality much more variable than the surface 

 of the "shifting sea"; that continental masses, seem- 

 ingly so fixed, are really rising and falling in billows 

 thousands of feet in height, ages instead of moments 

 being consumed in the sweep between crest and hollow. 



These slow oscillations of land surfaces being under- 

 stood, many geological enigmas were made clear- 

 such as the alternation of marine and fresh-water for- 

 mations in a vertical series, which Cuvier and Bron- 

 gniart had observed near Paris ; or the sandwiching of 

 layers of coal, of subaerial formation, between layers 

 of subaqueous clay or sandstone, which may be ob- 

 served everywhere in the coal measures. In particular, 

 the extreme thickness of the sedimentary strata as a 

 whole, many times exceeding the depth of the deepest 

 known sea, was for the first time explicable when it 

 was understood that such strata had formed in slowly 

 sinking ocean-beds. 



All doubt as to the mode of origin of stratified rocks 

 being thus removed, the way was opened for a more 

 favorable consideration of that other Huttonian doc- 



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