84 BULLETIN 852, U. S. DEPAKTMENT OF AGRICULTURE. 



small fluctuations were damped, so that close readings were made possible by means 

 of an attached mercury gauge. The difference in level of the water at these two 

 points, which was corrected, in the case of the surge-tank readings, to allow for the 

 velocity head of the water which passed the surge-tank connection, included, of 

 course, the loss at entry to the pipe line. The engineers who made the tests found 

 it impossible on account of the disturbance to measure the pressure of the water in 

 the conduit immediately behind the gatehouse, where the only manhole for a con- 

 siderable distance is located. 



Great care was exercised to obviate errors in observation or calculation. 



To obtain the coefficient of the conduit and plot a curve of losses for different veloci- 

 ties of water involved a long series of observations and a large amount of computation. 

 The coloring material used was potassium permanganate in the form of small crystals. 

 It was advisable to use as little of the color as possible and still enough to enable the 

 observer to distinguish it easily at the power-house weir. When the water was clear 

 it required about two-thirds of a pint of crystals. Roily water required considerably 

 more. 



The apparent loss of head measured in the conduit is the elevation of water in the 

 forebay minus the elevation of water in the surge tank. There are three corrections 

 to be applied to this resultant figure. It is assumed that the elevation of water in 

 the surge tank is lower than a pitot-tube reading in the conduit opposite the surge 

 tank branch by an amount equal to the velocity head of the water passing the surge- 

 tank branch. Hence this velocity head is added to the level of the water at the 

 gatehouse to give the correct figure for entry loss plus conduit loss, plus distributor 

 loss from gatehouse to surge-tank branch. The entry loss based on the judgment of 

 the engineers and on data impossible to give herein was taken as one-quarter of the 



/l V 2 \ 

 velocity head or ( J^2~a)' The distributor loss from unit No. 7 to the surge-tank 



branch was obtained by experiment and checked by computation. These two 

 quantities, namely, entry loss and distributor loss, were deducted from the total loss 

 and the net loss in the conduit, due to friction and curves, obtained. By this method 

 about 34 runs were made and computed during the summer of 1913 and 8 more during 

 the summer of 1914. The total range of velocity was from 7 feet per second to 21 

 feet per second. 



The items under No. 41a, in Table 3, are not computed from the 

 42 runs mentioned in the last paragraph above, but are developed 

 from a velocity-friction loss curve which is itself based on those 42 

 runs. From this curve the velocities and corresponding friction 

 losses were chosen and the remaining hydraulic elements and the 

 retardation factors in the various formulas computed. 



A study of these retardation factors indicates that this conduit is 

 exceptionally smooth. Only in cases where conservation of head is 

 of great value in dollars and cents would the expense of hand treat- 

 ment, such as is described here, be warranted. If we take the 

 coefficients of retardation at their face value, then this pipe will carry 

 from 10 to 15 per cent more than an average pipe of the type that 

 the writer has classified as of the highest commercial construction. 

 However, it is to be borne in mind that the experiments on this 

 conduit determined gross losses of head from which loss by friction 

 alone must be developed under certain assumptions. While no 

 criticism of the assumptions is made, still the fact remains that, had 

 it been feasible to determine friction losses alone, it is quite possible 

 that the seeming variation of 10 to 15 per cent mentioned above 

 might have been much reduced. 



FLOW-LINE PIPES AND CONDUITS. 



No. 50, Experiment FF-1.— 22-inch jointed concrete pipe of South- 

 ern California Edison Co., Mill Creek power plant, No. 2, California. — 

 The description of the experiment upon this line, as taken from 

 correspondence with Mr. Finkle reads: 



The pipe was made in 2-foot sections in the ordinary plain cement-pipe forms as 

 used for that purpose, and consisted of 1 part Portland cement and 3 parts sand mixed 



