MISCELLANEA. 
191 
very soils which from their qualities had previously been un- 
productive^ would l)e rendered fertile, by the simple extension 
of the natural process of irrigation or drainage ; for, we 
should remark, ere we quite forget the second part of our 
argument, that these two processes are dependent one upon 
the other. 
The following statement shows the nature of the various 
strata, &c., in their order of superposition : — 
Gravel and sand-beds, overlying many of the 
formations, uniformly porous. 
Porous. Non-Porous. 
Crag 
Freshwater beds 
London clay — Plastic clay 
Sands of the Plastic clay 
Chalk (all the beds) 
Greensand (ditto) 
Weald clay, &c. 
j Portland oolite 
Sand 
Kimmeridge clay 
1 Upper calcareous grit 
"S Coralline oolite 
l_ Lower calcareous grit 
Oxford clay 
Kelloway^s rock 
Clay 
r Combrash 
I Sand 
Forest marble 
Clay 
Bath oolite 
Fullers' earth (variable) 
