468 lOSSIL INVERTEBRATED ANIMALS. 



waters of the sea have covered all those heights. These waters 

 could not be there without having extended to very consider- 

 able distances, as well in France as in other countries. They 

 must also have retired either slowly, or with rapidity. If they 

 retired slowly, all the parts, which are dry at present, must 

 have been shores in succession. Everywhere we should find 

 the traces of cliffs and escarpments, such as we now find on 

 the shores of the sea — and everywhere we should find flints 

 rounded by the waves. But nothing of the kind is to be seen. 

 There is every reason to believe that the retreat of the waters 

 was rapid, and this is the general opinion. In the last case, 

 when the level of the waters had come to that at the bottom 

 of the sea, and even before they must have furrowed it in 

 retiring, and gaining, on different sides, the lower grounds, 

 they must have found, in various directions, the long valleys, 

 at the bottom of which the streams and rivers flow at the pre- 

 sent day, and the principal of which are covered with rolled 

 flints. 



The bottom of that sea, which once covered the tracts of 

 land now inhabited, may have been unequal, like that which 

 the sea leaves at the present day. But the correspondence of 

 the strata on each side of the basins leads to the belief that 

 they have, in general, been formed by the breaking up of the 

 latter ; and the bodies which they contain, and which are 

 foreign to the places in which they are found, prove clearly 

 that the strata of more elevated countries must have been 

 broken up to furnish them. 



Before we quite dismiss this subject of petrifactions in ge- 

 neral, it may not be unamusing to our readers briefly to notice 

 certain speculations, which have been put forth, relative to 

 the process of petrifaction itself, or the change of an organized 

 body into stony matter. 



This subject was meditated very long and profoundly by the 

 ancient naturalists, and even by theologians, because it is 

 connected with the history of the creation of the world, and 



