NATURAL HISTORY OF CREATION. Si 



luulerstund how such strata were foniiod in an age 

 marked by ultra-tropical heat and frequent volcanic dis- 

 turbances. An estuary, cut off by an upthrow of trap, 

 or a change of level, and left to dry up under the heat 

 of the sun, would quickly become the bed of a dense 

 layer of rock salt. A second shift of level, or some other 

 volcanic disturbance, connecting it again with the sea, 

 would expose this stratum to being covered over with 

 a layer of sand or mud, destined in time to form the 

 next stratum of rock above it. 



The plants of this era are few and unobtrusive. 

 Equiseta, calamites, ferns, Voltzia, and a few of the 

 other families found so abundantly in the preceding 

 formation, here present themselves, but in diminished 

 size and quantity. 



This seems to be the proper place to advert to certain 

 memorials of a peculiar and unexpected character re- 

 specting these early ages in the sandstones. So low as 

 the bottom of the carboniferous system, slabs are found 

 marked over a great extent of surface with that peculiar 

 corrugation or wrinkling which the receding tide leaves 

 upon a sandy beach when the sea is but slightly agitated ; 

 and not only are these ripple-marks, as they are called, 

 found on the surfaces, but casts of them are found on 

 the under sides of slabs lying above. The phenomena 

 suggest the time when the sand ultimately formed into 

 these stone slabs, was part of the beach of a sea of the 

 carbonigenous era; when, left wavy by one tide, it was 

 covered over with a thin layer of fresh sand by the next, 

 and so on, precisely as such circumstances might be 

 expected to take place at the present day. Sandstone 

 surfaces, ripple-marked, are found throughout the sub- 

 sequent formations : in those of the new red, at mor6 



