FIXING THE GRADE OF DRAINS. 93 



served in another chapter, the object of thorough drain- 

 age is to bring all the soil under the influence of drains 

 either natural or artificial. There are soils where drains 

 200 feet apart give good drainage for farm crops. 

 There are others where 33 feet is none to near to lay 

 the drains. These conditions vary so widely that one 

 familiar with one kind of soil is inclined to disbelieve a 

 statement regarding the other. Here is where the ex- 

 perience and close observation of the engineer come 

 into use and should be worth many dollars to the land- 

 owner. It cannot be urged too strongly upon the en- 

 gineer who is entering upon this class of work, to famil- 

 iarize himself with that very interesting subject, the 

 behavior of soils under different methods of treatment 

 and also acquaint himself with the physical differences 

 of soils with reference to drainage. 



This is a field for the exercise of close observation 

 upon the ground. As a hint along this line, it may 

 be said that the vegetation is a good index to the nat- 

 ural character and condition of the soil. Certain plants 

 grow luxuriantly upon some kinds of soil and not on 

 others. Learn what these are and keep them in mind 

 when reviewing the land. There may be some open 

 ditches of greater or less magnitude which affect the 

 adjoining land more or less widely as to its drainage. 

 This effect may be known by the appearance of the 

 land and vegetation which is found upon it. If it is 

 the spring of the year, dig a post-hole and note how 

 rapidly it fills with water. These observations may 

 suggest the means by which may be gained that knowl- 

 edge of the soil which is necessary to an intellierent 

 location of drains as to depth and distance apart. 



