40 



northern portion of the Bristol Coalfield without profound convic- 

 tion of the enormous lapse of time which must have taken place, 

 or the forces employed during the New Red Sandstone period, 

 whether we consider it Tinder its powerful denuding agency, or 

 the chemical and mechanical deposits it has left behind it. 

 Again, if we wish to examine typical sections of the entire 

 series of this New Red group, we must look to the Valley of the 

 Severn at Tewkesbury, Newent, &c., for examples to aid our 

 research, where they occur 1400 feet thick. 



I believe, then, that it was during the process of the denu- 

 dation of the Palaeozoic Rocks by the seas of this New Red epoch, 

 that the faults and fissures, which had their prior existence, were 

 fiUed-in, either chemically or mechanically, or both combined. It 

 is evident, from the colour and nature of the New Red Marls and 

 Sandstones, that a vast abundance of the Peroxide and Protoxide 

 of Iron must have been present under some condition at the time 

 of deposition* perhaps through the rapid oxidation of the 

 denuded masses of Old Red Sandstone, Carboniferous Limestone, 

 and Coal Measures, &c. It is not improbable, either, but that 

 the chemical condition of the Saline waters, or waters at higher 

 temperature, may have tended more readily to deposit the Iron 

 in the faults, &c., &c. 



* In order to shew that some value may be attached to this view, I append an 



analysis of both the Grey and Red Marls of the New Red series, when it will be 

 seen that in both cases a large per ceutage of Iron occurs either in the form of 

 Protoxide or Peroxide, both of them being found in the Red Marls, and only the 

 Protoxide in the Grey or Blue. 



Eed Marl Grey or Blue Marl 



SiBca 48.69 48.62 



Protoxide of Iron .... 4.79 13.09 



Peroxide 9.09 0.00 



Alumina 8.77 9.01 



Lime 8.69 8.39 



Magnesia 0.94 1.00 



Soda 0.53 0.58 



Potash 3.15 3.30 



Sulphuric Acid 0.27 0.14 



Carbonic Acid 8.56 10.18 



Organic matter 1.18 1.90 



Water and loss 4.25 3.79 



Now the Metallic Iron contained in these Marls is considerable : they yield the 

 following results : — 



Red Marl 9.99 



Blue Marl 10.47 



