ON THE ACTION OF CURRENTS. 453 



have scooped out, either by a violent action, or by a 

 slow one, however long continued, any of those long and 

 broad longitudinal depressions, which are named valleys, 

 or of those narrow openings, with almost vertical walls, 

 which are named gorges or ravines. 



4. That, even when the deposites, which border these 

 valleys or these ravines, are composed of transportable 

 matter, the waters which at present flow in them could 

 not have scooped them out, even supposing them to have 

 been much larger in some than they now are ; the decli- 

 vity of the present deposite not being sufficiently great 

 to give to these masses of water the rapidity necessary 

 for producing this effect, and a power sufficient for car- 

 rying off* the moveable matters which filled the valley or 

 gorge. ydfcfl 



5. Lastly, that the present running waters, so far 

 from having contributed to form the numerous valleys, 

 glens, gorges and ravines, continually tend to fill them 

 up, and rather to level the surface of the globe than 

 to furrow it, more deeply than it is. 



Vid. Brongniart sur TEau. 



NOTE 



On the Connection of Geology with Agriculture and 

 Planting-*. 



THAT all sorts of soils are not equally adapted to all 

 productions, is a remark of Virgil's, the truth of which 



* The remarks on the connection of geology with agriculture and plant- 

 ing, are inserted here as an illustration of some of the details in the body 

 3 



