112 DEPTH AFFECTING DISTANCE. 



be regulated with reference to the mfiuence of cli- 

 mate on evaporation. Drains have been known to 

 emit water on account of the density of the atmos- 

 phere ; therefore, when the predominating weather 

 is cloudy, and the air dense, much more water will 

 remain to be carried off than when a bright, un- 

 clouded sun increases the evaporation. Besides 

 this, the intervals should depend upon the character 

 of the soil. If the drains are forty feet apart, the 

 moisture could find its way more easily and in 

 quicker time through a porous than a close soil, 

 because of the less degree of attraction. In the 

 former the distance might be made fifty feet, while 

 in the latter it would be necessary to reduce it to 

 thirty or even twenty. 



The depth of the drain should also aff"ect the in- 

 tervals between them in porous soils. It is self- 

 evident that a drain four feet in depth will reach 

 further, and draw off the water from a greater dis- 

 tance, than one of three feet in such a soil ; yet in 

 clay it is not safe to rely upon it to a great extent. 

 There is an argument of still more force for the 

 frequency of drains in the orchard, which is seldom 

 alluded to, but which is, nevertheless, a considera- 

 tion of importance. It is the prevention of obstruction 

 from the roots of trees growing into the j^ipes. This 

 sometimes occurs on account of the moisture in 

 them during the summer ; and, although there have 

 been few instances in which drains have been 



