82 BULLETIN 126, U. S. DEPARTMENT OF AGEICULTUEE. 
The lining has a 3^-inch base overlaid with a ^-inch top coating of 
cement mortar hand-troweled to a very smooth and even surface. 
The canal has a bottom width of 10 feet, 1^ to 1 side slopes, and a 
vertical depth of 6^ feet. At the top of the lining a 1-foot berm 
extends back into the bank. When carrying a 6-foot depth of water 
the canal has a capacity of 615 second-feet. 
The lined portion of this canal offers an example of unusual care in 
construction to obtain a smooth interior. Its curves have been spi- 
raled throughout. The lining is made up of 16-foot sections on tan- 
gents and 12-foot sections on curves. The exact shape of the finished 
section was secured by the use of a template having the same area as 
the cross section of the finished canal. TJhe methods employed in 
construction and various details of the work are shown in Plates XV 
to XVII, inclusive. The concrete was laid continuously. Adjoin- 
ing slabs were separated by one thickness of tar paper and connected 
by short lengths of ^-inch steel rods used as dowel pins. The entire 
surface of the lining was plastered and smoothed with a steel trowel 
as soon as the concrete had set sufficiently to permit it, and which 
doubtless accounts for the absence of surface scaling. 
No displacements due to pressure, settlement, or buckling are to be 
found in this lining. The only cracks which have appeared are those 
at the expansion joints. It has been noticed that in the summer 
these, found to be about 0.025 to 0.030 inch wide in the morning, 
are tightly closed by 1 or 2 o'clock in the afternoon. 
A brief summary of data on various canal linings is given in Table 
IV for the purpose of supplementing that contained in the text 
