216 SOILS 



grade boards nailed, upon a taut cord, and care- 

 ful measuring to the cord. The latter operation 

 is done with a rod and great care should be taken 

 to hold it exactly vertical. A spirit level will aid in 

 this. See that the cord does not stretch during 

 changes in the weather. When carefully executed 

 this simple method of grading gives very satis- 

 factory results. 



There are many other home-made devices for 

 establishing grades, as the walking level, and those 

 in which a spirit level is used. When the field 

 has a noticeable slope a careful workman can make 

 a fairly accurate grade by simply watching the 

 flow of water in the ditch. But it is not best to 

 depend upon the eye alone, except, perhaps, for 

 very small fields which have a pronounced slope. 



THE NUMBER AND DIRECTION OF DRAINS 



This is determined by the contour of the land and 

 the character of the soil. If a more or less con- 

 tinuous depression runs through the field, some- 

 where near the middle, the drains would probably 

 have but one outlet, with one main following the 

 depression, and with laterals running obliquely 

 from it to the surrounding higher land, unless 

 something could be gained by a short cut. If 

 there were two depressions there might be two 

 mains, which woula unite to make one outlet. If 

 the whole field slopes slightly in one direction, say 

 toward an open ditch, the water in which never 

 rises above the point at which the outlet of the 

 drains would be, mains might be dispensed with 

 altogether and the field drained by parallel lines of 

 small tile running from the upper end of the field 

 to the ditch, each having an independent outlet. 



