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of these particular grasses depends upon the presence of a 
certain quantity of alumina. And the evidence, as far as it 
goes, proves this to be the only necessary condition, as far 
as the texture or earthy ingredients are concerned ; for the 
quantity of silica and calcareous matter is indefinite. But 
it would have been as absurd in me to assert that the bare 
earthy ingredients in the best constituted soil, without the 
addition of manures, would produce the best grasses in the 
highest perfection, — as it would be in the Professor to say 
that either bones alone, or bones placed in a soil of simple 
sand or simple clay, would have the same effect. The Lias 
contains probably, from its organic remains, abundance of 
phosphates, and also the limited quantity of alumina ; hence 
its superiority in the formation of grazing soils. 
