S6 



ENGINEERING FOR LAND DRAINAGE. 



engineer will have to deal with. There is a variety of 

 forms for keeping level notes, as well as methods of 

 making drainage computations, but the methods here 

 described and recommended are in quite general use 

 among engineers and possess the merit of being simple 

 and adapted to all kinds of work coming within the 

 sphere of levelling. 



The Field-book, — A good form and size for a book 

 in which to record and keep the level notes is one with 

 pages about 4 inches by 6|- inches containing about 

 eighty-five leaves. Rule the left-hand page into five 



Fig. II. — Levelling. 



columns, and head them as shown in level notes ac- 

 companying Fig. 1 1 . The right-hand page will be 

 left for entering diagrams and explanatory notes. A 

 size larger than this is imnecessary and will also be 

 found inconvenient to carry in the pocket. 



Level Practice. — Select some bench-mark or other 

 point from which it is proposed to start, and if its ele- 

 vation has not been determined before, assume one 

 which will be convenient to use without introducing 

 minus expressions. If we begin low down on some 

 water-course, perhaps 10.00 will do; if higher up 20.00, 

 30.00, or 100.00 should be used as the elevation of the 



