28 BULLETIN 194, U. S. DEPARTMENT OF -AGRICULTURE. 
DESCRIPTION OF CHANNELS. 
The descriptions in the following pages are to be considered as 
supplementary to the table beginning on page 19, which gives all 
the information necessary to a clear understanding of the hydraulic 
conditions holding at various tests with the exception of. a detailed 
description of the channel, which would have made the table too 
cumbersome. The descriptions of the channels follow the same 
order and are numbered like those in the table, with the exception 
that data obtained from other sources than the work of this division 
are abstracted in the Appendix commencing on page 62. 
CONCRETE LININGS. 
No. 1, Expt. S-26, New York Canal, Payette-Boise project, U. S. Reclamation 
Service, Idaho. A large canal, in concrete, rough as an orange, with plastered expan- 
sion joints. Experiment rated as class C, because water issues from an open check 
in canal about 600 feet above station and the canal passes into an earth section 
about 100 feet below station 6. (See PI. I, fig. 1.) Cross sections developed from 
office notes of United States Reclamation Service through courtesy of W. G. Steward. 
Impossible to determine condition of bottom with water in canal. There is a slight 
curve in the reach which disturbs the filaments of current. For additional data on 
this canal see Nos. 2 and 3, Table I. Coefficient n=0.0101. 
No. 11, Expt. B-4, Ridenbaugh Canal, Nampa-Meridian Irrigation District, Idaho. 
This test was made two years before and covered about the same reach as in test No. 
13 below. Mr. Bark found a slightly lower value for slope than later experimenters, 
which accounts for the lower value of n found. The preponderence of evidence 
would indicate that a value of about 0.0125 is right for this nearly perfect piece of 
concrete, to include both tangents and curves. Coefficient n=0.0110. 
No. 12, Expt. S-24. This lining in the same canal as No. 11 is a very smooth, 
hand-troweled, cement wash on a base of concrete 3^ inches thick. The reach is on 
tangent with about a 6° curve beginning at station 9. The lining was placed in slabs 
16 feet long with iron dowel pins and strips of tarred paper between slabs. After 
the forms were removed the joints were poured with a neat cement. As a rule the 
joints are as smooth to the hand as any other part of the lining (PL I, fig. 2), though slight 
cracks are opened during cold parts of the day. This is an exceptionally well-made 
lining, and this, coupled with the fact that the curves are spiraled into the tangents, 
accounts for the very low value of n as found by all experimenters. For additional 
experience on this canal see Nos. 11 to 15, Table I. Coefficient n=0.0121. 
No. 13, Expt. S-24a, was made on the same canal as S-24, but the reach included 
not only the 901 feet of tangent as above, but also the above-mentioned curve, which 
was about 600 feet long, and a short reach of tangent below the curve, making the 
total reach 1,819 feet long. As is to be expected, the value of n is a little higher 
than on tangent. The slabs on curves were but 12 feet long. Coefficient n=0.0129. 
No. 14, Expt. F-3. This experiment was made on approximately the same reach 
of canal as S-24, but was 1,020.6 feet long, with one slight curve in the reach. The 
slopes of the surface in this and experiments 26 and 28 were found by a line of levels 
run between the ends of reaches as usual, but the water surface was found by means of 
a gauge constructed on the piezometric principle. The hydraulic grade as given in 
the table is the mean of 23 tests. An instrument of this form should give the surface 
at the time of reading very closely, but the experimenter must be sure that this slope 
is the same as the one held at the time of the discharge measurement. Coefficient 
n=0.0124. 
