TENTH ANNUAL YEAR BOOK— PART X 565 



soil when wet does perhaps more injury than if it were not plowed at 

 all, because if plowed when wet it becomes lumpy and difficult of culture. 



Drainage prevents surface washing. Many plowed fields, especially 

 where the land is rolling, suffer greatly in spring and fall time from 

 washing by heavy rains. On drained land the rain is at once absorbed 

 and washing is thus prevented. 



Principles to be used in locating drains: 



No. 1. Lay mains in the line of natural drainage. There are but few 

 tracts of land that do not have some natural surface drainages, or places 

 where the water gathers and in floodtime flows off. It is also true that 

 as a rule the direction of the water of the soil is toward these places, 

 and in order to intercept it and carry it off, the main should be located 

 there. We must, if possible, work in the line of natural drainage if we 

 expect to obtain efficiency of work and economy in construction. 



If we consider the drainage of some distinct point or tract without 

 reference to benefiting lands along the line by which it may be reached 

 by a drain, then the question hinges upon the difference in cost of the 

 line by the way of some near cut, and the more circuitous and natural 

 route. The shortest and straightest drain is the best, provided it does the 

 desired work as well. It is usually the case that the line of natural 

 drainage may be straightened by short cuts here and there, making the 

 drain less expensive and more efficient without impairing its value as 

 a drain in the natural course. 



It should be said in this connection that there are many flats, ponds, 

 basins, etc., which can be reached by a main drain through some shorter 

 cut than by the natural overflow channel. These matters should be ex- 

 amined with care before a location is made. 



2. Laterals should be laid in the line of greatest slope. 



Many think by extending a drain across a slope, water coming through 

 the soil from above will be intercepted by the drain and thus prevented 

 from passing further toward the foot of the slope. Practice has proved 

 this to be a mistake. Lines for conveying the drainage water may be 

 located at right angles to the slope if placed so far down on the bottom 

 land that the grade of the drain is greater than the slope of the surface 

 at the sides, as a few facts will show. Water oozes through the soil along 

 the line of the steepest slope, at all times seeking a lower place, where 

 it can remain at rest. 



If a drain is placed across this course of soil water, the descent of 

 the soil channels being greater than that of the drain, the water will flow 

 out of the joints of the drain and continue to ooze through the soil, only 

 a part being carried away in the drain. Place the drains up and down 

 the slope, and all water coming into the drain will be carried away 

 quickly, and little currents induced to flow toward the drain from both 

 sides. 



The above refers particularly to hillsides, requiring drainage, and is 

 applicable to flat lands, having any slope whatever. 



There are sags, swamps and points into which an outlet tile must be 

 extended by the most feasible course, after that the general course 

 supplies. 



