The Plow and the Harrow 85 



that a soil is capable of holding depends directly on the 

 fineness of its particles. Then that plow which will break 

 and pulverize the soil most thoroughly is the one best 

 adapted to fit the soil for holding moisture. This point is 

 well illustrated by King, who says: "Since each indepen- 

 dent soil-grain of a moist soil is more or less completely 

 surrounded by a film of water, it is evident that, other 

 conditions being present, the largest aggregate surface 

 area may retain the most water per cubic foot. Now, a 

 cubic foot of marbles 1 inch in diameter possesses an 

 aggregate surface of 27.7 square feet, while if the marbles 

 were reduced in diameter to one-thousandth of an inch, 

 then the total area per cubic foot is increased to 37,700 

 square feet." From this it is evident that the total quantity 

 of water capable of being absorbed by a soil that is cloddy 

 and lumpy is very slight in comparison with the quantity 

 when the soil is in a finely divided state; and not only is its 

 absorbing power less, but its power of holding moisture is 

 also greatly reduced. 



Harrowing to save moisture. 



The harrow, besides pulverizing and fining the soil for 

 the seed-bed, is most efficient in making an earth-mulch. 

 The spring-tooth harrow is in reality a cultivator. When 

 used as an instrument to conserve moisture, the teeth 

 should penetrate to the depth of about 3 inches, and to 

 produce the best effect the ridges left by it should be 

 leveled off by a smoother, which can now be purchased as 

 an attachment to the harrow. The tillage of orchards by 

 the harrow is now practised extensively, and nothing short 

 of irrigation will so nearly meet the demands of trees for 

 moisture, particularly in the heavier soils. 



The Acme harrow is a most excellent implement on 



