6o IRRIGATION FARMING. 



the line of the canal, still approximating the distance 

 and going up or down if he thinks it worth while or 

 necessary to recflify position from time to time, 

 according to the distance estimated and the 

 grade assumed. Having gone as far as it is 

 intended to build the canal, he should turn at 

 right angles across the valley back to the river 

 ^>-|^ and take his last line of levels. Throughout 

 ^JBfc the operations described, as many good bench 

 ^B./ marks as possible should be established for 

 ^' future reference. The taking of these levels 

 being done, he should finish his track survey 



Uof the river-bank up the stream to the point at 

 which his first line of cross levels originated. 

 Having established the objecflive point in this 

 way, the matter of running the transit to the 

 target and placing the grade stakes is very 

 simple, and any schoolboy ought to be able to 

 locate the grade line corredlly. 



In case a surveyor is not engaged and the 

 spirit-level is to be employed the procedure is 

 very simple. Take a pine plank two by six 

 j! inches by sixteen and a half feet, surfaced on 

 all sides, the edges of which should be reduced 

 to a true, straight edge. Exadlly midway of 

 the stick, on one edge, fasten a carpenter's 

 spirit-level with such accuracy that when the 

 plank is set on edge on a level surface the in- 



TARGET. ^ .,, . f. ^ 1 ATA ^ 



strument will mdicate a level. To locate a 

 ditch with a fall of one-fourth of an inch to the rod, 

 attach at the extreme end of the plank, on the opposite 

 edge to the level, a block of wood one-fourth of an inch 



