116 ON THE MANAGEMENT OF GRASS LANDS IN ENGLAND. 



clay soil in the same part of England. The latter has very mnch 

 the character of the unmitigated Oxford clays ; it was made on 

 private account, and has never been published. Its tenacity is 

 the chief impediment to tlie luxuriant growth of crops, and to 

 laying down with seeds : — 



Aylesbury Soil. Oxford Clay Soil. 



Organic matter and comlun. water, . KVIO 6"10 



12-30 



Oxide of iron, .... 6'70 



Alumina. . . . . . 1'21 



Carl)onate of lime, .... 9-26 17-96 



Mao-nesia, ..... 0-44 1-01 



Potasis, . . . . .1-15 0-85 



Soda, . . . . .1-64 0-34 



Phosphoric acid .... 0-58 trace 



Sulphuric acid, . . . .1-63 ,, 



Insoluble in acids, .... 57-11 61-43 



100-00 100-00 



The insoluble Aylesbury soil is represented as under : — 



Silica, ...... 50-06 



Alumina, ..... 4-41 



Lime, ...... 0-57 



Magnesia, . . . . . 1-08 



Potass, ...... 0-99 



57-11 



Both analyses were made by the chemists of the Eoyal English 

 Society, but in the first column carbonic acid is shown along 

 with the lime, whereas in the Journal it is entered at 3-29 and 

 given separately. What are called clay soils owe their tenacity 

 to alumina, which is a kind of Hercules among the earths, as 

 sulphuric acid is among the acids. A very small per cent of 

 alumina imparts its genuine characteristics to a soil — plasticity 

 and cohesiveness. So far as we may infer from the analyses, 

 there may be little more alumina in the sample of Oxford clay 

 than there is in that of Aylesbury, notwithstanding the wide dif- 

 ference of their characters. Eew of tlie clay soils, and even those 

 styled strong clays, hold more than eight or ten per cent of 

 alumina, but in ordinary circumstances it makes its dominant 

 character conspicuous ; and to the other constituents of the 

 Aylesbury soil we must look for the explanation of the anomaly. 

 Organic matter is well known to possess the property of loosen- 

 ing and imparting friability to clay soils, and there are good 

 grounds for assertinor that the large amount of oriranic matter in 

 the Aylesbury soil is the means of making it what it is, so differ- 

 ent in its physical properties from the other.* 



* We have long thouglit the classification of soils has liitlierto been defective 

 If soils were grouped and named according to the preponderance of a particular 

 constituent, then tliey would be necessarily reduced to one class only, namely , 



