248 CAMPBELL'S SOIL CULTURE MANUAL 



prepared from pulverized clay was three and a half times 

 as great as from the soil with the coarse sand mulch. 



The conclusions of Prof. King after these experiments 

 have been fully corroborated by all of our observations, 

 there is no result without a cause and a theory can never 

 be accepted as a fact until the cause is fully understood. 



Under the head of capillary attraction we have learned 

 that moistures moves very much faster through small pores 

 in the soil than large ones, while it is true that soil abso- 





A. B. 



Cut No. 22. Soil Mulch and Dust Blanket before rain, (a) Soil 

 Mulch; (b) Dust Blanket. 



lutely void of moisture is minus any capillary attraction 

 yet, when the rays of the sun in a mid-July day pierces 

 the soil's surface the dry dust soon becomes so very warm 

 or hot that a vapor begins to rise from the surface of the 

 moist soil below and soon the lower particles of the dust 

 blanket become slightly moistened; then other particles 

 still above, while the lower ones become slightly more 

 moist until connection is sufficient to lift the moisture on 

 up to the surface where it is lost. 



