THE HOSE-LEVEL 111 



for the reading is higher than the one on which the long 

 rod stood. It should be introduced into the column in 

 the table for positive readings, and after the number of 

 the stake for which it was taken. 



230. Negative readings. A negative reading indicates 

 that the stake for which it was taken is lower than the stake 

 from which it was taken. It should be introduced into 

 the column for negative readings in the table and after 

 the number of the stake for which it was taken, the 

 stake upon which the short rod stood. 



231. Computing elevations. Computing the eleva- 

 tions of the several grade stakes becomes a very simple 

 matter with the readings obtained by the hose-level. 

 The reading for any stake indicates how much higher or 

 lower it is than the stake from which the reading was taken. 

 There is no height of instrument to determine or to work 

 from. 



In Table XIX the level reading for stake 2 is positive 

 .50 foot. This reading was taken from stake 1, and the 

 fact that it is a positive reading indicates that stake 2 is 

 .50 foot higher than stake 1. Adding this reading to the 

 elevation of stake 1 gives 10.50 feet as the elevation of 

 stake 2. The reading for stake 3 is negative .17 foot, 

 and the fact that it is a negative reading indicates that 

 stake 3 is .17 foot lower than stake 2, from which the 

 reading for stake 3 was taken. Substracting this reading, 

 .17 foot, from the elevation of stake 2 gives 10.33 feet. 



232. The rule is apparent. To determine the eleva- 

 tion of a stake, add its reading, if positive, to or subtract 

 its reading, if negative, from the elevation of the stake 

 from which its reading was taken. 



When the elevations have been correctly computed 

 from the readings in Table XIX, they are found to corre- 



