266 



Bulletin 254. 



1907 and the character of the ditch cut 

 by it in fairly heavy clay soil containing 

 occasional boulders as large as one's 

 head is shown in Fig. 208. This ditch is 

 four feet deep and was cut at the rate 

 of about three feet per minute when the 

 machine was in operation. 



A stretch of 171^ rods, three feet deep, 

 was dug in clay soil in one hour and 

 forty-five minutes or at the rate of 10 

 rods per hour. Under favorable con- 

 ditions this rate can be maintained. The 

 expense of operating the machine is from 

 $5.00 to $10.00 per day. 



Except where large stones in the 

 bottom of the ditch may occasionally 

 mar its uniformity no hand finishing of 

 grade is necessary where the machine is 

 used. As a rule a better finish is given 

 than could be imparted by hand. 



(3) Grading. — The finishing of the 

 ditch is the delicate part of the operation 

 and is the final test of a piece of work. 

 The leveling may be ever so carefully 

 done but may be rendered of no avail 

 by lack of care in bringing the ditch 

 bottom to grade. In all hand work, a 

 reliable man should be employed for this 

 operation. The superficial excavation should never be made below 

 the "-rade line and in fact should not come nearer to it than an inch 

 or two. This permits the use of the grade scoop and the creation of 

 a clean smooth grade on firm soil which is the ideal foundation for 

 laving^ tile. The establishment 



I 



Fig. 208— a four foot ditch 

 cut ill heavy clay soil on 

 the University farm by the 

 steam ditciiing machine 

 shozi'n ill fiyure 207. 



. 



a 



^ 



t 





of an accurate grade is facili- 

 tated by a small flow of water --- .| ,-.-v 

 in the bottom of the ditch W^'MjiM 

 which will quickly reveal any 

 inequalities. Where this is not 

 available a carefully established 

 grade line accurately followed 

 is the most feasible method. 

 A method of correlating the 



grade line with the grade of the ditch is shown in b^ig. 209. The grade 

 cord is drawn at a definite uniform height above the finished bottom 



Fig. 209. — Method of correlating grade of 

 ditch with grade line. 



