42 



THE IRRIGATION AGE. 



lateral ditches in such a way as to accommodate large 

 volumes for short periods of time. There is no other 

 system practiced in the West which enables one man 

 to handle from ten to twenty cubic feet per second 

 without assistance and with such little waste. 



LAYING OUT CHECKS. 



The plan followed in laying out checks differs more 

 or less in each district and on neighboring farms. It is 

 seldom that two engineers or surveyors adopt 'the same 

 methods. In the description which follows there has 



MM* 



Check box. Section across length at bottom of page, section 

 in middle, and longitudinal section showing floor at 



been given in a general way and with some changes the 

 plan followed by Mr. P. E. Smith, of Ceres, Cal. 



One man is equipped with an ordinary engineer's 

 level, another with a leveling rod, and a third, if he is 

 available, carries a hatchet and stakes er else a long- 

 handled shovel. The instrument man, by taking rod 

 readings at different points of the field, gains a general 

 knowledge of the high and low places as well as the 

 different slopes. He then sets up his level to command 

 the upper end of the field, which we shall assume con- 

 tains forty acres, and sends the rodman to the highest 

 corner, where he drives a stake flush 

 with the average ground surface and 

 takes a reading. It is well to locate 

 this starting point by a witness stake, 

 on which is written the assumed ele- 

 vation, so that this bench can be 

 readily found when needed to check 

 levels. If three-inch contours are de- 

 sired, the rodman raises the target 

 five and two-tenths feet and proceeds 

 from the high corner down one of 

 the margins of the field until the level 

 line from the instrument again in- 

 tersects the middle of the target, 

 where a stake is driven to mark the 

 beginning of the first contour. The 

 rodman then proceeds with clamped 

 rod to locate the first contour by shift- 

 ing the rod from place to place at 

 intervals of, say, thirty paces until 

 the target is on a level with the in- 

 strument. These points on the con- 

 tour may be marked by small piles 

 of dirt or by temporary stakes. It 

 is a good plan to follow the rodman, 

 keeping about 200 feet in his rear, 

 with some sort of ditch plow which 

 marks each contour by a furrow. A 

 walking plow is not suitable for this 

 purpose, since the plowman must be 

 elevated in order to see over the horses 

 and improve on the line indicated 

 by the stakes, or marks, by rounding 

 out the angles. In like manner other 

 contours are laid out unjil the forty- 

 acre tract presents the appearance 

 shown in Fig. 6. 



The next task is to subdivide the 

 space between the contours into 

 checks of suitable size and provide 

 for the location of boundary and field 

 ditches to convey water to each check. 

 No hard and fast rule can be laid 

 down for the arrangement of the 

 ditches. The field under considera- 

 tion may be subdivided as shown in 

 Fig. 7, in which the double lines in- 

 dicate the ditches and single lines 

 levees. This forty-acre tract would 

 contain about forty checks. If con- 

 ditions were favorable and it was 

 deemed advisable to have the checks 

 contain on an average two acres 

 instead of one, the same diagram 

 would apply to an eighty-acre tract. 



across side 

 top. 



