312 Ground Water, Wells and Farm Drainage. 



own place it is quite important for him to have a clear con- 

 ception of the general principles of drainage and of what 

 constitutes thoroughly good detail practice. 



FIG. 131. Showing forms of drainage tools. 



380. Means for Determining Levels As a general rule 



the laying out of a system, of drains should only be at- 

 tempted with good instruments, two of which are repre- 

 sented in Fig. 131. Where a good drainage level cannot be 

 had the best substitute is the water level, one form of 

 which is represented in Fig. 131 and another in Fig. 132 ; 

 which consists of a piece of gas pipe about 3 feet long 

 mounted on a standard and provided with two elbows into 

 which are cemented two pieces of water gauge glass. When 

 the instrument is filled with water the surfaces in the two 

 tubes stand on a level and can be used to sight across. To 

 move the instrument close the ends of the tubes with corks. 



As a substitute for the gas pipe a piece of rubber tubing 

 may be used or a piece of garden hose. 



A less reliable level can be improvised by arranging au 

 arm upon a standard upon which a carpenter's level may 

 be set. Or a still more crude level may be made from a 



