CONSTRUCTION 151 



records. In keeping field notes it is desirable to have 

 some definite method of indicating mains, sub-mains, and 

 the several laterals. The main is usually designated 

 simply as main. If there is more than one system of tile 

 drains on a farm, the systems should be numbered or 

 lettered, so that the main of any system would be indi- 

 cated, main of " system A " or " system 1." A sub-main 

 is simplest designated by the stake in the main at which it 

 discharges its water. If a sub-main united with a main 

 at stake 5 of the main, it would be designated as " sub- 

 main 5." A lateral is simplest indicated by the stake of 

 the sub-main or main at which it empties its water. A 

 lateral uniting with a main at stake 11 of the main may 

 be designated "lateral 11." A lateral emptying its 

 water at stake 13 of a sub-main would be designated 

 lateral from stake 13 of sub-main, if there was but one 

 sub-main; if more than one, the number of the sub- 

 main would need to be indicated. (See Table XX.) 



