207 



vol. 7, there is an exhaustive " Report on 

 the Analyses of the Ashes of Plants, by Thomas 

 Way, Professor of Chemistry at the Royal Agri- 

 cultural College, Cirencester," which gives the 

 result of sixty-two analyses of the ash of wheat, 

 from as many samples of that grain, mostly grown 

 on different soils and under different circumstances. 

 The report gives the quantity of wheat per acre, 

 the weight of straw cut near the ground, 

 and also that of the chaff. These researches 

 show that from 93 to 150 Ibs. of soluble silica are 

 required to form an acre of wheat ; and it would 

 appear from investigations that three-fourths of this 

 silica is demanded by nature during the sixty days 

 preceding the maturing of the crop. 



This is the period when the stem acquires solidity 

 and strength, and most of its incombustible earthy 

 matter, the quantity of which varies from three 

 to fifteen per cent, of the weight of the straw. 

 Professor Johnston and Sir Humphrey Davy 

 adduce instances when more than fifteen per cent, 

 of ash was found, while Professor Way states 

 cases where less than three per cent, was obtained. 

 The mean of forty samples was four-and-a-half 

 per cent. Dr. Sprengel gives three -and-a-half as the 

 mean of his analyses, while M. Baussingault found 

 an average of seven per cent. As silica is truly 

 the force of all the grass species, as cane, corn, oat, 

 rye, rice, millet, &c., imparting strength to them, 



