X48 Hints for the Formation of 



often fufficient to feparate, in diftinct bands or zones, par- 

 ticles of different gravity *. 



8. Nature of the rolled pebbles found on their borders. 



9. The quantity and kinds of fith by which they are cha- 

 racter! fed. 



10. To enquire, as in regard to the fea, whether it ap- 

 pears that they contain more or lefs water than formerly, 

 and whether they have changed their courfes. 



11. As the greater part of thefe queftions may be applied 

 to lakes, it is not necelTary to make them the fubje£t of a 

 feparate chapter. I mall infift only on their nature and the 

 meafure of their depth ; on the temperature of their bottom 

 compared with that at their furface in different feafons ; and 

 alfo on the veftiges of their extent and height in the remotefl 

 ages, compared with their prefent ftate. 



CHAP. VII. 



Obfrvations to be made on the Plains. 



1. The extent, limits and inclination of a plain; its 

 height above the level of the fea; its relation with the hills 

 or mountains bv which it is bordered. To form a proper 

 idea of it as a whole, it would be necefiary to afcend fome 

 eminence commanding a view over it. 



2. The vegetable earth ; its nature and thicknefs in dif- 

 ferent parts, compared with the time fince it has been culti- 

 vated, with its productions, and the kind o culture. The 

 nature of the bauson which that earth refts. 



3. Rolled pebbles. {See Chap, viii.) 



4. Sand, argil ; their nature ; thicknefs of their beds. 



5. Nature and thicknefs of the ftrata of the earth at the 

 grcateft depth poffible to be reached, by taking advantage of 

 the time when wells, mines and other excavations are dug. 



* Moycns cie rendre utiles les voynges des naturaliftes, Efprit des Jour- 

 H*ux. .Aval 1 /.«h. 



This 



