EXPERIMENT STATION BULLETINS. 



487 



tween each two stakes, till the front-sight reading is taken on the last 

 stake. 



Caution : Be careful always before recording a reading to examine the 

 instrument to see that it is perfectly adjusted. 



KEEPING NOTES. 



A more extensive form must be employed now for keeping records of 

 readings, etc., than was shown on page 18. A table like the following is 

 suggested : 



TABLE III. 



In column one are recorded the stake numbers in order. 



In column two is recorded the distance of each stake from stake 1. 



With these distances the distance between any two stakes may be 

 found. 



As the work of leveling progresses, the back-sight readings should be 

 recorded properly in column 3 and the fore-sight readings should be 

 recorded in column 5. 



Usually all readings are taken before computations are begun to de- 

 termine the elevation of the several stakes. This of course includes the 

 determination of the height of instrument at the several places at which it 

 was set. 



To make the succeeding steps more clear, let us take up a piece of 

 actual work, with diagram and the data used in carrying it to comple- 

 tion. 



Fig. 14 A-B represents the profile of the surface of a portion of one 

 of the college fields in which it was necessary to place a tile drain. The 

 distance A to B is 500 feet. In the original drawing 2 inches horizontally 

 equaled 100 ft. while 14-inch vertically equaled 1 ft. Using different 

 scales for the two dimensions destroys the proportions and requires some 

 use of the imagination. A-C represents a fall which provided a good out- 

 let. Fig. 15 represents the same surface with grade stakes driven 

 50 feet apart according to directions on page 20, and numbered (1-11) 

 Only one finder is shown in place, and that at grade stake 7. 



Fig. 16 shows the level in the three positions described on page 22 (b), 

 i. e. : 1st, between stakes 1 and 2; 2nd, between stakes 2 and 3; 3rd, 

 between stakes 3 and 4. It shows, also, the leveling rod in the positions 

 successively at which it would be held to obtain the three back-sight 

 readings and three fore-sight readings spoken of above. There are 

 also shown the directions in which the three back-sight readings were 

 taken and the directions in which the three fore-sight readings were 

 taken with their values. These readings will be found in columns 3 and 

 5 in Table IV. 



