C 143 j 



gand's lamp, in a bason of porcelain, to a temperature 

 equal to 300 Fahrenheit ; and if a thermometer is not 

 used, the proper degree may be easily ascertained, by 

 keeping a piece of wood in contact with the bottom of 

 the dish ; as long as the colour of the wood remains 

 unaltered, the heat is not too high ; -but when the 

 wood begins to be charred, the process must be stop- 

 ped. A small quantity of water will perhaps remain 

 in the soil even after this operation, but it always af- 

 fords useful comparative results ; and if a higher 

 temperature were employed, the vegetable or animal 

 matter would undergo decomposition, and in conse- 

 quence the experiment be wholly unsatisfactory. 



The loss of weight in the process should be care- 

 fully noted, and when in four hundred grains of soil 

 it reaches as high as 50, the soil may be considered 

 as in the greatest degree absorbent, and retentive of 

 water, and will generally be found to contain much 

 vegetable or animal matter, or a large proportion of 

 aluminous earth. When the loss is only from 2O to 

 10, the land may be considered as only slightly absor- 

 bent and retentive, and siliceous earth probably forms 

 the greatest part of it. 



2. None of the loose stones, gravel, or large 

 vegetable fibres should be divided from the pure soil 

 till after the water is drawn off; for these bodies are 

 themselves often highly absorbent and retentive, and 

 in consequence influence the fertility of the land. The 

 next process, however, after that of heating, should be 

 their separation, which may be easily accomplished by 

 the sieve, after the soil has been gently bruised in a 



