full pressure, indicating an increase of capacity in the 10-in. pipe
greater than a corresponding increase in the 16-in. The alignment of the
10-in. line, vertically and horizontally, is more regular and uniform
than the 16-in. line. The latter has many abrupt curves and bends,
vertically and horizontally. It crosses nine sharp ridges and dips under
as many deep arroyos. This introduces a fixed element of frictional
resistance which does not decrease with the increasing smoothness of
the interior surface of wood pipe, and probably accounts for the higher
resistance of the 16-in. line.

From Fig. 2 it appears that, while the 10-in. line had an initial
coefficient of roughness slightly greater than 0.009 and now equal to
it, the 16-in. line had one equal at first but now slightly less than
0.01.

The line from Bonito Creek to Nogal Reservoir was to have a capacity of
5 sec-ft. Referring to the profile, it was determined that for the
hydraulic grade of 33-1/3 ft. per 1000 ft., a 10-in. pipe was necessary,
and that a 16-in. pipe was required for the grade of 3 ft. per 1000 ft.

_Test No. 1_.--On March 10th, 1908, a quantity of bran was poured into
the upper end of the 10-in. pipe at _A_ (Fig. 2), and the time of its
appearance at the lower end of the 16-in. pipe at _E_ was noted. The
time was 3 hours and 50 min.

This gave:

Area of 10-in. pipe = 0.5454 sq. ft.
" " 16 " " = 1.3960 " "
Length " 10 " " = 13,200 ft.