274 



STATE BOARD OF AGRICULTURE. 



a small scale, would show the advantages and disadvantages of applying our 

 principle of location. 



Drains should run directly down the slope. Thus in Fig. 5, drains marked 

 1, 2, 3, and 4 run directly down the slope; each has then the maximum fall 

 to be obtained on that ground ; that is, they strike the main drain at a point 

 near the outlet and are short as compared with drains marked 5 and 6. 



Again, drain 5, being on lower ground than 6, receives water principally from 

 one side, viz.: toward 6 ; on the other hand, each of the drains 1, 2, 3, and 4 

 receives water equally from both sides, consequently the water has to travel 

 through the ground nearly twice as far, on the average, to reach drains 5 and 

 6 as to reach drains 1, 2, 3, and 4. 



The actual locating of a drain can usually be done more accurately by 

 working from the outlet towards the source, as the eye can estimate a small 

 rise better than a corresponding fall. Again, in the progress of leveling, the 

 calculations are more simple in running up hill than down; for that reason 

 all directions given here are, that we start at the outlet and work toward tho 

 source. If work is done in the reverse direction, it will be easy to change the 

 application of what is stated here. The convenience or accuracy of either 

 depends largely on habit, and it is not essential which end is the starting point. 

 The general direction for laying out a system of drains would be to start, 

 at the outlet, run as directly as possible up the drainage valley of the area to 

 be drained ; when necessary, run in branches, which shall make as small an 

 angle as possible with tho main ; if the general direction of the branch differs 

 more than sixty degrees from the main, it should be connected with a curve. 

 If the two streams, from branch and main drain, Join at a large angle, they 

 will oppose each other very much in their flow, and a bar or obstruction is 

 likely to be formed across the smaller stream ; if they have the same general 

 direction before uniting, one current will accelerate the other. To secure the 

 most efficient drainage with the least expenditure, the final laterals should be 

 parallel with each other. This will frequently require some drains to be run 

 diagonally down the slope. The person locating the drains will have to decide 

 which principle should be sacrificed to give the best results. 



SILT BASIN". 



To prevent loss of velocity, and also to keep the main drain clear, a silt 

 basin was constructed, as shown in Fig. G. It was made as follows: Depth 

 below main drain, 12 inches; diameter, 12 inches; main drain, 4 inches 

 below the laterals. Its full depth was five feet; the lower three feet were con- 

 structed of brick, laid in cement mortar, laid square 12 inches in the clear. 



On the top of the brick-work was a 12- 

 inch sewer-pipe placed socket upwards ; a 

 cover was provided slipping inside the 

 sewer-pipe and resting on the brick, 

 another resting in the socket of the sewer- 

 pipe. The construction of the silt basin 

 is shown clearly in Fig. G. The original 

 object of a silt basin was to afford a place 

 for deposit of silt gathered in the drains 

 above it; this cannot be effectually done 

 unless the silt basin is deeper than the 

 outlet drain ; and a break in the current 

 Silt Basin. Fig. 6. is produced by having the outlet drains on 



