CONCRETE LINING FOR IRRIGATION CANALS. 47 
VII. n = 0.018 1 for concrete-lined canals coated as in Type VI and 
having the bottom more or less covered with sand and gravel, or else 
a clean bottom but poor alignment, irregular cross section, broken 
gradient, or the like. 
OTHER KINDS OF LINING. 
Experiments were made by this office in 1906 in cooperation with 
the University of California 2 to determine the cost and relative merits 
of different kinds of canal lining. A series of short experimental 
ditches were excavated in a field in Stanislaus County, Cal., about 4 
miles east of the town of Modesto. The channels used were 50 feet 
long, had a bottom width of 2 feet, a depth of 2 J feet, and a slope of 
li to 1 on both sides and ends. 
The experiments were continued under the direction of the writer 
the year following on the same site, and a similar set of experiments 
were also conducted on the university farm at Davis, Cal. The 
results obtained in 1907 at both sites did not agree with those pub- 
lished in the progress report and in consequence the final report was 
not published. The belief is quite general, however, that the report 
of the results obtained in 1906 2 tended to give erroneous impressions 
as to the relative merits of certain kinds of linings. This is especially 
true of oil lining. The Lemoore Canal & Irrigation Co. of Kings 
County, Cal., was cited as an example where heavy crude petroleum 
containing a high percentage of asphaltum had been successfully 
used in lining 1J miles of their main canal. It would appear that 
this experiment did not prove altogether satisfactory since the com- 
pany which tried it has discontinued the use of this kind of lining. 
Other investigations have shown that oil lining is not effective for a 
long period of time. Even in California where a heavy oil containing 
a large percentage of asphaltum can be purchased for about 2 cents 
per gallon, practically no canals have been lined, to the writer's 
knowledge, with this material in the past five years. 
When lumber was cheap and cement expensive it was common 
practice in the West to fine the weak and leaky portions of canals 
with lumber in the form of flumes. The short life of wood, particu- 
larly where it is in contact with moistened earth and exposed to the 
air, the high cost of maintenance, the high cost of lumber, and the 
somewhat lower cost of cement have all tended to lessen the use of 
wooden lining. 
Reference has already been made to the advantages of a natural 
lining of silt derived from the earthy impurities borne by the water 
in the canals. A clay puddle may likewise serve as an effective bar- 
1 The value of n for some concrete-lined canals exceeds 0.018. In such cases, however, the increased car- 
rying capacity due to lining is counterbalanced or nearly so by deposits of debris in the bottom, aquatic 
vegetation, or other causes. 
2 California Sta. Bui. 1S8 (1907). 
