THE IBBIOATION AGE. 



277 



No. 3 

 six parts of 



No. 4. 

 square yard. 



No. 5. 



No. 6. 



No. 7. 



No. 8. 

 square yard. 



No. 9. 



No. 10. 



No. 11. 



No. 12. 



Heavy oil and gravel, one part of oil to 

 gravel (2y 2 inches thick). 

 Heavy oil sprinkled, 3 2-3 gallons per 



Earth (no lining). 



Thin oil, 2% gallons per square yard. 



Puddled clay, 3% inches thick. 



Heavy oil sprinkled, 3 1-3 gallons per 



Cement mortar, 1 inch thick. 

 Cement concrete, 2i/ inches thick. 

 Earth (no lining). 

 Cement lime concrete, 2i/ 2 inches thick. 



The table accompanying this report (see page 

 414) refers to the ditches after they had been changed. 



The water was again turned into the ditches on 

 August 6th, but because of a serious break in the main 

 canal of the irrigation system, the water could not be 

 obtained again until August 28th. Observations were 



from the lined ditches with the seepage from the earth 

 ditches, the relation is obtained by making the com- 

 parison with the nearest earth ditch. 



The efficiency of a ditch is the ratio between the 

 rate of percolation for the earth ditch and the rate 

 of percolation for the adjacent lined ditch; or, effi- 

 ciency = rate of percolation for earth ditch over the 

 rate of percolation for lined ditch. The larger this 

 ratio the more efficient or water-tight is the lining. 



From the mean sinkage or mean percolation of 

 the several ditches is computed the percentage of saving 

 due to the lining in each case. This saving indicates 

 the probable percentage of water saved from the loss 

 which would take place if the ditch was not lined. 

 The experimental cost per square foot of the lining is 

 the actual cost at which the work was done. It does 

 not include the cost of finishing and preparing the 

 ditch for the lining. This cost was about 1 cent per 

 square foot 



1. Thole showing Rate of Percolation. 



again begun and were taken until September 10th, a 

 period of fourteen days. 



For the first four days the results were not very 

 uniform; probably because some of the ditches had held 

 water much better than the others during the interval 

 when no water was available for filling them. The 

 rates of percolation per hour given in the table are 

 the rates of percolation for the last ten days. This 

 rate of percolation is computed from the readings 

 taken each day. The seepage and evaporation for each 

 ditch, from the time the ditch is filled to the time 

 when the level of the water is measured next morning 

 just before filling, give the total seepage and evapora- 

 tion for that time. Subtracting from this the loss in 

 level due to evaporation gives the loss due to seepage. 

 This quantity divided by the number of hours in which 

 this loss occurred gives the rate of percolation or seep- 

 age in feet per hour. 



Consulting the table, it will be noticed that the 

 rates of percolation for the three earth ditches were 

 very nearly equal. However, in comparing the seepage 



The actual cost per square foot for wort on a larger 

 scale would naturally be somewhat smaller. The cost 

 given in the table is estimated from similar work in 

 existence and agrees with the cost in the examples 

 mentioned in the first part of this paper. For oil 

 lining the cost would depend largely on the price of oil. 

 The price assumed in preparing the table was 2 cents 

 a gallon for the oil and 1 cent a gallon to apply it. 

 For cement concrete or cement mortar it is customary 

 to prepare the ditch and finish it carefully. The bot- 

 tom and side slopes are made even and regular. The 

 cost of finishing on a large scale for first-class work 

 would probably be less than the actual cost on the ex- 

 perimental ditches and would probably not exceed % 

 of a cent per square foot. 



For oil and puddle linings, it would not be neces- 

 sary to finish the ditch so carefully. The removal 

 of weeds may be the only preparation necessary. 



MATEHIALS AND COST. 



Cement. California Portland cement (Standard 

 Brand) , at $3.00 a barrel in Modesto. 



