g6 ENGINEERING FOR LAND DRAINAGE. 



Drafting Instriimc7its. 



While there are other instruments which are some- 

 times desirable, the following are all that are essential 

 for ordinary work: A right-line pen, a scale divided to 

 tenths of an inch, a drawing-board 24 inches square, a 

 bottle of liquid India ink, a protractor for platting 

 angles, a T square with 24-inch blade, a bottle of car- 

 mine ink, a few thumb-tacks for fastening paper to the 

 board and some good steel pens. 



A serviceable paper for making working plats is 

 what is known as bond paper. The size of sheet most 

 convenient is 18 inches by 24 inches. The merit of 

 this paper is that it is flexible, does not crack when 

 folded and carried in the pocket, is partially transparent, 

 so that it can be used in making tracings, and also 

 constitutes a fair negative from which blue prints 

 can be made. Vellum or tracing-cloth is particularly 

 adapted to use in making duplicate copies where fine 

 blue prints are desired. 



For finished maps, Whatman's hot-pressed, un- 

 mounted paper should be used; sheets 17x22 are 

 convenient in size. 



Platting Compass Notes and Angles. 



The platting of a survey made with the compass con- 

 sists in drawing on paper the lines and angles which 

 have been measured on the ground. The lines should 

 be drawn to scale and the angles measured with a pro- 

 tractor. A protractor is a scale in the form of a semi- 

 circle of brass or celluloid divided into 180 parts or 

 degrees and numbered in both directions. The straight 



