Walls 



47 



earth beneath is taken away, as by water, 

 and the wall just " naturally " drops. 

 An open tile pipe beneath the wall, if given 

 a pitch, helps to carry away moisture. 

 But this pipe must be able to lead some- 

 where away from the wall and empty or 

 else it will become merely a cistern and 



The solid retaining wall needs a drain at the bot- 

 tom. Here are two satisfactory methods of 

 laying drain tiles 



hold the water instead of discharging it. 

 If the wall is a retaining wall it is doubly 

 important that no water collects near 

 the bottom. The illustration shows the 

 method for draining this type of wall. 

 (See Fig. 15.) 



