ACCOUNT OF BOOKS. 



941 



be only by pointing out essential 

 errors in my observations, that 

 my system can, with any founda- 

 tion, be farther attacked." 



The heads under which Mr. de 

 Luc points out the objects to be 

 proved by his Travels are as 

 follow : 



" Head 1. Since the opposite 

 sides of many valleys are formed of 

 different substances, these valleys 

 cannot be attributed to the action 

 of rivers cutting through a conti- 

 nuous mass. 



" 2. The difference between the 

 gravels on the heights and on the 

 declivities of the opposite sides of 

 valleys, and that between those 

 gravels and the stony strata which 

 border them, are also in contradic- 

 tion to this hypothesis. 



" 3. The dift'erences between the 

 opposite sides of valleys, in their 

 height and form, ai'e not less con- 

 trary to the hypothesis in ques- 

 tion. 



" 4. The breadth and depth of 

 valleys do not bear any proportion 

 to the size of the rivers which flow 

 in them. 



*' 5. The opinion that valleys 

 have been excavated by rivers is 

 also opposed by the great differ- 

 ences of declivity in thesame valley. 



*' 6. The widenings and con- 

 tractions of valleys are also a cir- 

 cumstance absolutely contrary to 

 this hypothesis. 



♦• 7. The aquatic plants, which 

 grow on the beds of rivers, show 

 directly that no erosion takes place 

 there. 



♦* 8. Running waters, far from 

 having produced the excavation of 

 valleys, have in many places 

 raised them to a higher level than 

 they originally possessed. 



" 9. Lakes also oppose an 

 absolute barrier to this system. 



" 10. The successive differences 

 in the gravel on the beds of such 

 rivers as flow in plains, after quit- 

 ting mountains, prove that the ma- 

 terials, which once filled the va- 

 cancies of the latter have not been 

 carried away by those streams. 



"11. Characteristic differences 

 between alluvial grounds, and such 

 gravelly soils as are out of the 

 courses of rivers. 



"12. The blocks of stone scat- 

 tered over our continents cannot 

 possibly have migrated on their 

 surface. 



" 13. Some valleys parallel to 

 the coasts, by which streams ar- 

 rive at the sea, are also contrary 

 to the hypothesis of the excavation 

 of valleys by running waters. 



" 14. Many rivers, which, be- 

 fore they arrive at the sea, discharge 

 themselves into gulphs, show par- 

 ticularly, at that end of their 

 course, that they have not dug 

 their own channels. 



" 15. The appearance of the 

 sides of valleys, and of their sum- 

 raits, leaves no doubt with respect 

 to the origin of all great sinuosities 

 in the surface of our continents. 



" 16. First consideration re- 

 specting the blocks and gravels, in 

 opposition to the idea of their 

 having been brought down from 

 mountains, resulting from their na- 

 ture. 



" 17. Second consideration re- 

 specting the blocks and gravels, 

 resulting from their situations ; by 

 which is excluded every idea of 

 their migration from any place on 

 the existing continents. 



'« 18. Effects of the sea on those 

 coasts which, at the birth of 

 the continents, extended towards 

 it with a gentle declivity. 



«* 19. General considerations on 

 steep coasts. 



«' 20. Effects 



