628 GARDEN MANAGEMENT. 



and if nitric acid be added, it becomes gelatinous, — indications of the means 

 by which silica is treated in the great alembic of nature, and adapted for 

 absorption into the tissue of plants. 



1647. I^ preparing it for the more obvious mechanical purpose which it 

 serves in plant-culture, sand is divested of the other constituents of the soil, by 

 washing and sifting through a fine sieve. In this wa}-, all soils will yield a 

 portion of this element, and dry ; but the best mode of procuring it, is to 

 proceed to some stream running through any of the sandstone countries. 

 In such a stream there are few places where the winding eddies have not 

 formed a sand-bank, and one of these will generally furnish an ample supply. 



1648. When thoroughly washed, and all particles of clay extracted, let it 

 be thrown into a heap, sheltered from the rain, and turned vmtU it is 

 thoroughly aerated ; it should then be harvested in a dry place till wanted for 

 use. Sihca is a constituent of all the grasses, and is absolutely necessary iu 

 the cultivation of all those of the family cultivated in our hothouses and 

 gardens : it is also a necessaiy amelioratorin all clay soils. Its value is there- 

 fore beyond calculation to the gardener. 



1649. -A-fter soils are collected for use, they should not be washed by exces- 

 sive rains, and for that reason they should be in narrow upright ridges, so as 

 to throw the rain off; and after they have been turned a time or two, it 

 may be necessary to protect them by a slight covering of weather-boarding. 



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