188 FARM ARITHMETIC. 



of 2 inches per 100 feet to drain six acres, using the quar- 

 ter-inch standard ? 60 acres ? 



Important truth. In addition to a careful calculation 

 of the size of drains good judgment must be used in the 

 application of the results. A tract of land may have such 

 surface conditions that the underdrains will be called upon 

 to take care of a much larger area than at first apparent. 

 It is also important to take into account the facilities for 

 natural drainage. Too large a tile may involve an ex- 

 pense greater than the returns would warrant, while too 

 small a tile may entail loss that will soon greatly exceed 

 the saving in first cost. 



