THE HOSE-LEVEL 185 



the grade bar mark to the grade stake, and record in column 

 5 of your notes. Then pass to stake 3 and determine 

 distance from grade bar mark to grade stake, and so on 

 to stake 8. In the case in hand, these measurements, 

 if correctly made, would appear in the notes as in column 

 5 of Table XXI. 



243. Breaking the grade. The depth of ditch at any 

 point is found by subtracting the height of the grade bar 

 from 5 feet 6 inches. The depths as shown in column 5 of 

 Table XXI range as great as 4 feet 1| inches. This is 

 not objectionable except for the extra expense in digging. 

 Raising the grade bar 4 inches at stake 5 would mean a 

 break at that point in the grade or fall of the drain, but 

 would still leave a good fall for the upper half of the drain. 

 Such a change would require another set of computations. 

 But such computations are simple. 1 It would require also 

 that a new set of marks be established for the grade bars. 



244. Placing the grade bars. With the grade or fall 

 definitely established, the computations completed and 

 the proper heights for the grade bars marked on the inner 

 edges of the stakes, the grade bars should be placed. At 

 each stake, and three to four feet from it, on the opposite 

 side of the proposed ditch, should be driven a second 

 stake of proper height. The grade bar, in each case 

 straight edge up with a spirit level resting upon it, should 

 be brought into position against the front side of the 

 stakes so that, when level, the upper edge rests even with 

 the mark previously put upon the inner edge of the first 



1 If the mark B 5 at 5 were raised 4 inches, the distance from 

 Z/s to B 5 would then be (0-8-6) and this would represent the 

 fall from B 9 to B$. The fall from B 5 to BI would be (2-1-4) 

 less (0-8-6) = (1-4-6). (0-8-6) 4- 4 = (0-2-l|), the fall per 

 50 feet between stake 9 and stake 5, while (1-4-6) -5- 4 = 

 (0-4-1^), the fall per 50 feet between stake 5 and stake 1. 



