On the Cornbrash of the neighbourhood of Cirencester. 263 



The average rent may perhaps be gathered from the following 

 table:— 



the acre. 



1 . Stonebrash, Inferior Oolite 7*. to 20*. 



2. Stonebrash, Great Oolite 14*. to 25*. 



3. Cornbrash 20*. to 40*. 



This great difference in the productive powers of soils, which 

 a cursory examination only would lead to the conclusion were 

 nearly alike in character, may, to a considerable extent, be ex- 

 plained by the following analyses, which were made by Professor 

 Voelcker from specimens which I had the pleasure of procuring 

 for him ; and it may be remarked in passing, that as the analyses 

 were made by the Professor in order to ascertain the different 

 constituents of the rocks and not the soil, in each case typical 

 hand specimens were presented to him, and the result singularly 

 explains observed facts with regard to the crops upon the re- 

 spective substrata. 



Result of analyses by Professor A. Voelcker : — 



These analyses show that the phosphoric acid and sulphate of 

 lime — two important chemical agents in the growth of crops — 

 greatly predominate in the Cornbrash ; and besides this, the thick- 

 ness of Cornbrash soil is always greater than that upon the 

 Stonebrashes, as this rock more readily breaks up and becomes 

 disintegrated by atmospheric action. 



These remarks tend to show the great practical advantage of 

 geological and chemical knowledge, and fully explain how a 

 successful farmer near Cirencester has converted a " brash farm " 

 — which is in general a term of reproach — into one of the most 

 productive farms in the district, this brash being the fertile Corn- 

 brash. 



But not only is this thin stratum of interest on account of 

 the tine crops which it yields, but it will ever present a 

 charm to the geologist from the rich harvest of fossils which it 



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