86 Theory of the Earth. 



The fea changes the equilibrium of the earth. The oyflers and other (hells which ase 

 formed in the mud of the fea, atteft the change which the earth has undergone about the 

 centre of the elements. Large rivers always wear away the earth which they detach by 

 friftion from their beds. This corrofion difcovers to us many banks of fhells heaped to- 

 gether in different layers, and the fnell-fiih have lived in the fame place when the waters 

 of the fea covered them. Thcfe banks in the courfe of time have been covered by other • 

 ftrata of mud of different thickneffcs; fo that the fiiells have been bedded in the mud 

 heaped above them in fuch a manner as to rife above the furface of tlie water. At the 

 prefent time thefe beds are at the height of hills and mountains, and the rivers, by wear- 

 ing them away, difcover the ftrata of fhells at their fummits. Here then is a portion of 

 the earth become lighter, which continually rifes while the oppofite parts approach 

 nearer and nearer to the centre of the earth ; and that which was formeriy the bottom of 

 the fea is now become the fummits of the mountains. 



When a river forms banks of mud or fand, and afterwards quits them, the water that 

 runs fvom thefe maffes flie ws the manner in which the mountains and valleys may by degrees 

 be formed in a foil riGng from the bottom of the fea, though this ground might at firft 

 have been nearly plain and uniform. The water which flows from this land elevated from 

 the bottom of the ocean, begins to form currents at the lower parts, and excavates the beds 

 of rivulets which receive the fluid from the neighbouring parts. The rivulets, afterwards 

 fed by the rain waters^ become broader and deeper every day, and are converted into tor- 

 rents paffmg through ravines : they unite into rivers, and by continually wearing away 

 their banks they convert the land between them into mountains. The rains have in- 

 ceffantly fwept and degraded thefe mountains. The elevated rock remains furrounded by 

 the air ; the earth of the fummit and its fides has defcended to its bafc, and, by raifing 

 the bottom of the fea which furrounded that bafe itfelf, has forced it to retire to a 

 diftance. 



Vinci is here the firft among modern philofophers who maintained that the greateft 

 part of the continents have formerly exifted at the bottom of the fea. We cannot reje£l 

 this do£lrine, which is proved by every geological obfcrvation ; but we do not yet difcern 

 the means of reconciling the fucceffive tranfportation of the fea, on the furface of the globe, 

 with the laws of gravitation. L. de Vinci offers an explanation which may well deferve 

 fome examination. It is different from the opinion of Bernier, wlio has afcribed a motion 

 to the centre of gravity, without changing the arrangement of the folid parts of the earth. 

 But the profound geometer, who has lately traced the fyftem of the world, agrees that the 

 obfervations of Bouguer and Mafkelyne on the attra£lion of mountains do not entirely de- 

 termine the denfity of the Interior part of the earth *. "We may therefore ftill fuppofe at 

 prefent, as Vinci does in his writings, that the fluid mafs in our globe is equal, or may be 

 even greater than the folid portion : or, if this hypothefis be not admitted, it will be fuflS- 

 cient if we fuppofe that there are feveral detached folid maffes in our globe, fo that each 

 continent may be conCdered as a fmall part of the total mafs of the earth. Whence the 

 mafs of matter tranfported by the rain during the lapfe of centuries from the fummits of 

 mountains to the bottom of the fea, may be fufficiently great, in proportion to the mafs of 

 each continent, to caufe thofe coiitinents to emerge more and more above the furface, or 



* Expofitiori du Syfttme du Monde, par P. S. La Place. 



to 



