4* IRRIGATION FARMING. 



If but little work is to be done a carpenter's com- 

 mon spirit level fastened onto a sixteen-foot strip of 

 board will answer very well. Instructions for running 

 grades are sent with each instrument. The first opera- 

 tion is to begin at the selected head and take 

 a series of long sight levels down the course of 

 the river to ascertain its approximate fall. 

 These levels should be taken with two rods to 

 save time, the locator making a sketch and 

 estimating roughly his distance at the some 

 time. Having gone down the river far enough 

 to satisfy himself as to its fall, he turns at 

 right angles as nearly as may be and continues 

 to level hill wards across the valley until he 

 records the elevation assumed as the head of 

 the works. He will now be able to fix the loca- 

 tion of any chosen grade upon the line of his 

 cross levels according to his estimated dis- 

 tance, and is therefore also in a position to es- 

 timate approximately the rate of his grade. 

 He knows from his sketch and estimated dis- 

 tance what area of the valley is behind him on 

 the upstream side bounded by the river, by the 

 canal and by the line of his cross levels. 



The next operation is to turn again at 

 right angle and continue leveling down the 

 valley more or less upon the line of the canal, 

 still approximating the distance and going up 

 or down if he thinks it worth while or necessary 

 to rectify position from time to time according 

 TARGET, to the distance estimated and the gradr as- 

 sumed. Having gone as far as it is intended to build 

 the canal, he should turn at right angles across the val- 

 ley back to the river and take his last line of levels. 

 Throughout the operations described as many good 

 bench marks as possible should be established for future 



