42 Observations on the 



dense, is generally preferred, though it requires more protract- 

 ed calcination. The same weight of both denser and looser 

 limestones furnish, (as is, I believe, exhibited by the admirable 

 Bishop Watson's experiments), the same quantity of lime, or very 

 nearly. These are the results of my analysis : — 



The blue, or mountain limestone, 100 grains. 



Grs. 



Of carbonic acid, , 40 



Lime and a few grains of coloured earthy"! 

 matter, , J 



Brown limestone, 100 grains. 



Of carbonic acid, 44 



Lime, Sfc 56 



Looser in its aggregation, and containing more water than the 



blue. 



Limestone is seen in large denuded mountain masses, form- 

 ing the crown of the hills, and their upper sides at the New 

 Weir ; and at WindclifF the Wye flows through a serpentine 

 channel principally formed of it. Smith thus classes the geo- 

 logy of this extremity of the country ; 



28. Red marl, and floetz sandstone. 



29. Floetz and magnesian limestone. 



30. Red and dun stone alternating. 



When we stand on the limited edge of one of these immense 

 and continuous cliffs, one idea must strike the mind, that it could 

 be no other than a mountainous trench to draw off those im- 

 mense waters which framed a great portion of the formations 

 which I have wandered over, here entering and here retiring. 

 The general elevation diminishes from Ross to Chepstow, so 

 precipitously that it has been stated by some, that the mensura- 

 tion of Syraond's Yate is 2,000* yards above the level of the 

 sea ; but this is obviously incorrect, My opinions axe, that the 

 low-ground of the Wye has been an entire swamp ; that the 



* According to Col. Mudge, the height of the M^lverns doe* not ex- 

 ceed l,4ii feet. 



