13,200 47,500 ------- + ------- = 13,800 2.56_x_ _x_ _x_ = 3.805 and 2.56_x_ = 9.740 The discharge is: For the 16-in. pipe, 1.396 x 3.805 = 5.31 cu. ft. per sec.; and, for the 10-in. pipe, 0.5454 x 9.74 = 5.31 cu. ft. per sec. The question arose as to whether or not the particles of bran in the water traveled as fast as the water flowed. It was also desired to check by observation the relative velocities in the two pipes, as above deduced. _Test No. 2_.--To determine these points, a second test was made, on March 31st, 1908, twenty days after the first one. In this test, green aniline, red potassium permanganate, and bran were used. An observer was placed at the end of the 10-in. line at _B_ (Fig. 2), and, by letting a small quantity of water run from a relief-valve there, he was able to note the time of the appearance of the colors and the bran. The green was started in the upper end of the 10-in. pipe, at _A_ (Fig. 2), at 8.30 A.M. It appeared at _B_ in 22 min., and at _E_ in 3 hours and 52 min. The red was started at 8.45 A.M. It reached _B_ in 21-1/2 min., but it was so faded that the time of its appearance at _E_ could not be noted exactly. The bran was started at 9.00 A.M. It reached _B_ in 22 min., and appeared at _E_ in 3 hours and 51 min. From the average of these figures, the velocities were: In the 16-in. pipe, 3.792 ft. per sec. " " 10 " " 9.695 " " " and the discharges were: In the 10-in. pipe, 5.287 cu. ft. per sec. " " 16 " " 5.293 " " " " The application of the equation for equalized relative velocities, as in the first test, gives: Velocity in 16-in. pipe = 9.705 " " 10 " " = 3.791 Discharge of 16 " " = 5.292 " " 10 " " = 5.293 These last figures would check exactly, except for dropping figures in the fourth decimal place. The results of these two tests, considering that 20 days elapsed between them, are in very close agreement, and establish the fact that bran is an accurate medium of measurement. _Test No 3_.--The 500 ft. of 10-in. pipe in the 16-in. line near the reservoir (Fig. 2) were replaced by 16-in. pipe in the summer of 1908. On May 12th, 1909, green aniline was started through the pipe at _A_ at 11.00 A.M., 11.30 A.M., and 12.00 P.M. In each case it appeared at _E_ in 3 hours and 31 min. This time is 20 min. less than that observed in the tests of the previous year, and is due to the removal of the 10-in. pipe from the 16-in. line and to the increasing smoothness of the interior surface of the pipe. The relative velocities and discharges under the third test, using the nomenclature of the first and correcting the lengths of pipe on account of the removal of the 10-in. pipe near the reservoir, are: 48,000 + 12,700 ----- --------- = 12,660 _x_ 2.56_x_ _x_ = 4.183 and 2.56_x_ = 10.708 and the discharges are: