AQUEOUS SOKUTIOX OF THE SOIL. 309 



years without perceptibly yielding aught of its mass to the 

 liquid, does, nevertheless, slowly dissolve. We may make 

 its solubility perceptible by a simple expedient. Pulver- 

 ize the bottle to the fiiiest dust, and thus extend the sur- 

 face of glass many thousand or million times; weigh the 

 glass-powder accurately, then agitate it for a few minutes 

 with water, remove the liquid, dry and weigh the glass 

 again. We shall thus find that the glass has lost several 

 per cent of its original weight (Pelouze), and by evapo- 

 rating the water, it will leave a solid residue equal in 

 weight to the loss experienced by the glass. 



AQUEOUS SOLUTION OF THE SOIL. 



The soil and the rocks from which it is formed would 

 commonly be spoken of as insoluble in water. They are, 

 however, soluble to a slight extent, or rather, we should 

 say, they contain soluble matters. 



The quantity that water dissolves from a soil depends 

 upon the amount of the liquid and the duration of its 

 contact ; it is therefore necessary, in order to estimate 

 properly any statements respecting the solubility of the 

 soil, to know the method and conditions of the experi- 

 ment upon which such statements are based. 



We subjoin the results of various investigations that 

 exhibit the general nature and amount of matters soluble 

 in water. 



In 1852 Verdeil and Risler examined 10 soils from the 

 grounds of the Instltut Agronomlque, at Versailles. In 

 each case about 22 lbs. of the fine earth were mixed with 

 pure lukewarm water to the consistence of a thin pap, 

 and after standing several hours with frequent agitation 

 the water vras poured ofi"; this process was repeated to 

 the third time. The clear, faintly yellow solutions thus 

 obtained were evaporated to dryness, and the residues 

 were analyzed with results as folloAvs, per cent • 



