20 NATURAL HISTORY, 



and thus, by means of the different motions and sedi- 

 ments, the bottom of the ocean, though formerly- 

 smooth, must soon he furrowed, and interspersed with 

 hills and chains of vast mountains, as we find it at pre- 

 sent. And the materials which consisted of sandy 

 and crystalline particles, would produce those masses 

 of rock and flint in which v, e find crystals and preci- 

 ous stor.es. Others composed of stony particles and 

 shells, produce lime stone and marble ; and, lastly, 

 particles of shells mixed with a pure earth, have given 

 risa to all our beds of rnarle and chalk. 



It may be said, however, that the greater number 

 of hills, whose summits consist of solid rocks of moor 

 stone, or marble, are founded upon small eminences 

 composed of lighter materials. But the explication of 

 this phenomenon is perfe :tly easy. The waters would 

 first operate upon the upper stratum, either of coasts, 

 or the bottom of the sea. This upper stratum general- 

 ly consists of clay, or sand ; and these light substances 

 being carried oiF and desposited sooner than the more 

 dense and solid, they woutd of consequence become 

 foundations for the more heavy particles to rest upon. 

 The harder and more ponderous substances would next 

 be subjected to the attrition of the water, and carried off 

 and deposited about the hillocks of sand or clay. These 

 small stony particles would, in process of time, form 

 those solid rocks which we now find on the tops of 

 hills and mountains. And as particles of stone are 

 heavier than those of either sand or clay, it is probable 

 that they were originally covered by superior strata 

 of considerable depth ; but that they now occupy the 

 highest stations, because they were last transported; 

 b.y the. waves.. 



