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were left by it when it was withdrawn to its present level. 

 On this point no decisive opinion can be offered : it cannot, 

 however, fail to call to our contemplation the consequences 

 of that revolution which this planet sustained, when its 

 surface was broken up, and extensive tracts entirely re- 

 moved, even to the solid granite, by the inconceivable 

 agencies of Divine power. 



To give to the world, formed anew from the shattered 

 fragments of that which preceded it, that state and form 

 which were requisite for the purposes to which it had been 

 decreed by the Almighty, numerous and extensive ope- 

 rations must have been ordained ; and from some of these, 

 it is not improbable that the phenomenon just mentioned 

 may have resulted ; and to similar causes may, perhaps, be 

 referred numerous other phenomena observable in the 

 structure of the earth. One of these, the appearance of 

 considerable tracts, bearing marks of the sea and fresh water, 

 having borne alternate sway over them, demands the earnest 

 attention of those who have engaged in these studies. 



That the tracts here referred to have been formed partly 

 by deposition from fresh water, is supposed to be proved by 

 the near agreement of many of the fossil shells which they 

 contain, with those which are now to be found actually 

 living in our rivers and marshes, and on the surface of the 

 earth. The first of these, considered as the lower fresh- 

 water formation, is found over fossil sea shells : and in 

 France, with alternate beds of gypsum and of marl, and with 

 the remains of land animals which, it is supposed, inhabited 

 the borders of the lakes in which the inhabitants of those 

 shells lived. Above this formation are found marine shells, 

 and above these, another fresh-water formation. 



From these facts M. Brongniart inferred that these dif- 

 ferent beds demonstrated the repeated alternations of sea 

 and of fresh-water on the same tract ; and that, at the 

 period when the sea was forming marbles, schists, &c. the 



