ERA OF THE SUPERFICIAL FORMATIONS. 95 



One remarkable circumstance connected with the tertiary 

 formation remains to be noticed, the prevalence of volcanic 

 action at that era. In Auvergne, in Catalonia, near Venice, 

 and in the vicinity of Rome and Naples, lavas exactly resem- 

 bling the produce of existing volcanoes are associated and 

 intermixed with the lacustrine as well as marine tertiaries. 

 The superficies of tertiaries in England is disturbed by two 

 great swells, forming what are called anticlinal axes, one of 

 which divides the London from the Hampshire basin, while 

 the other passes through the Isle of Wight, both throwing the 

 strata down at a violent inclination towards the north, as if 

 the subterranean disturbing force had waved forward in that 

 direction. The Pyrenees, too, and Alps, have both under- 

 gone elevation since the deposition of the tertiaries ; and in 

 Sicily there are mountains which have risen three thousand 

 feet since the deposition of some of the most recent of these 

 rocks. The general effect of these operations was of course to 

 extend the land surface, and to increase the variety of its 

 features, thus improving the capability of natural drainage, 

 and generally adapting the earth for the reception of higher 

 classes of animals. 



EKA OF THE SUPERFICIAL FORMATIONS EXISTING 



SPECIFIC FORMS ABUNDANT. 



WE have now completed our survey of the series of strati- 

 fied rocks, and traced in their fossils the progress of organic 

 creation down to a time which seems not long antecedent to 

 the appearance of man. There are, nevertheless, memorials 

 of still another era or space of time which it is all but certain 

 did also precede that event. 



The first that calls for notice is the phenomenon to which 

 geologists have applied the term denudation. Great hitches 

 and slips are detected in superficial strata, such as, if left in 

 their original state, must have caused considerable inequalities 

 on the face of the country ; yet all is found as smooth the 

 joinings are all as much reduced to a common level as if 

 some gigantic artificial force had been used for the purpose. 

 Again, a great valley has been scooped out in the midst of 

 sedimentary strata, leaving the edges of these facing each 

 other from the opposite sides, with perhaps here and there an 

 isolated mass starting up to the height of the two sides, being 

 composed of matter which has resisted the agency by which 



