a Theory of the Earth. 295 



vcrfal ; and thofe which follow an indeterminate direction, 

 oblique. 



2. To obferve this direction, efpecially in regard to that of 

 the planes of the ftrata of the mountains. 



3. Dimenfions of the valleys; their length, breadth, depth, 

 and the form of their tranfverfal feclion. 



4. The re-entering and falient angles : whether oppofite 

 to each falient angle, which forms a fide of the valley, the 

 fide or oppofite mountain forms a re-entering angle; or, ou 

 the other hand, whether the valley does not prefent alternate 

 conftrictions and fwellings ? 



5. Whether the oppofite mountains correfpond by their 

 height, their form, the inclination of their corresponding 

 faces ; the fituation of their ftrata, or their nature ? 



6. Anfwers to thefe queftions will ferye to determine 

 whether the valley may or may not be confidered as a large 

 fiffiire produced by the burfting afunder of the mountains 

 which it traverfes. 



7. If the lateral valleys which terminate at a principal 

 valley, as the branches of a tree at its trunk, correfpond or 

 not ; or, in other words, whether the branches of that trunk 

 arc oppofite or alternate ? 



The anfwers to thefe two queftions are very important for 

 the folution of this queftion : Whether the valleys have been 

 excavated by currents of the fca ? 



9. Whether there arc l'een a great number of narrow val- 

 Jeys, of no great depth at their moft elevated part, but be- 

 coming witlcr and deeper in proportion as they defcend 

 lower, which would feein to indicate that their excavation 

 has been the cffccl of the fall and defcent of water; efpecially 

 if the ftrata have the fame inclination on each fide of the 

 valley, and if its formation cannot be explained by a finking 

 down or heaving up of the earth. 



10. To obferve in a valley, the corresponding mountains 

 of which are of the fame nature, whether the ftrata of the' 

 mountain* do. not defcend on each fide towards the bottc 



U 4 



