CH. 11.] THE ROOT. 103 



enced by the state in which it is presented to 

 the atmosphere. In a finely divided state, mere 

 capillary attraction assists it : hence, as before in- 

 sisted, the importance of keeping the soil fre- 

 quently stirred, by hoeing, &c. But a mere mass of 

 cotton, by means of capillary attraction, will absorb 

 moisture from the aii', yet it parts with it at a very 

 slight elevation of temperature ; it is of importance, 

 therefore, to ascertain which are the manures that 

 not only absorb but retain moisture powerfully The 

 following results of my experiments throw some 

 light on this point : — 



Minutes, 

 ^ Pig dung evaporated to diTuess at a 



temperature of 106°, and then mois- 

 tened with 6 parts of water, required 

 for being reduced to diyness again, at 



the above temperature 135 



Horse dung, under similar circumstances 90 



o 

 n 



^ \ Common salt .75 



v 



Soot 75 



Rich Soil 32 



Chalk 29 



Poor soil (siliceous) 23 



Gypsum 18 



These experiments point out a criterion by which 

 we easily ascertain the comparative richness of any 



