THE FLOW OF WATER IN" WOOD-STAVE PIPE. 83 



Lowell Hydraulic Experiments, and Clemens Herschel on Venturi Water Meter, pub- 

 lished in Trans. Amer. Soc. Civ. Engin., vol. 26, p. 452). This form of entrance and 

 exit also has the advantage of furnishing an accurate and convenient means of meas- 

 uring the quantity of flow and of keeping track of the gauge height which will not be 

 affected by the condition of the ditch. 



Page 5, line 15. In small pipe, from 4 to 12 inches, used for irrigation and water- 

 works purposes, valves are always used at least in one place, and often a large number 

 of fittings and valves whose effect on the flow is similar to the ordinary gate valve . 



In such tests as the writer has made he has found no appreciable loss in any single 

 valve or fitting, but where there are many, as in waterworks systems, the loss on this 

 account is a matter for serious consideration. There does not seem to be much infor- 

 mation published that would throw light on this subject. 



Page 3, Hne 5, and page 48, line 35. Attention is directed to the fact that the 

 writer in 1909 first devised this type of formula from suggestions of Messrs. Saph and 

 Schoder. This formula is as follows [Formula 16, p. 48]: 

 Q=1.28D2-58H.o-585 



Since that date he has been using this in all his calculations as to the flow in wood 

 pipe. It is in the same form as the one devised by Mr. Moritz and the author. This 

 formula gives results from to 15 per cent less than the author's formula, being about 

 the same for smaller sizes of pipe and 15 per cent less discharge for the larger sizes of 

 pipe. It was the writer's intention in devising this formula to so select the coefii- 

 cients of D and H that the calculated flow would more nearly approach the quantities 

 of flow determined from tests that were lowest instead of those that were the average. 



Page 15, line 27. It is not at all impossible that in a number of the tests on which 

 the formula is based the real average diameter is different from the nominal diameter 

 assmned, due to the following causes: 

 (a) SwelUng of the wood by saturation. 



(6) Distortion due to imperfect backfilling or settlement where the pipe may have 

 been laid on more or less of a fill, or where there has been more or less leakage, 

 (c) Inaccuracy of manufacture. The writer in his examination of a 54-inch pipe 

 found an average of one-half inch larger than the nominal diameter, making 

 a difference of 1.8 per cent increase in the area. This pipe was measured every 

 100 feet throughout its entire length, from one manometer to the other. In 

 making these measurements considerable distortion was found to exist, and the 

 writer is not certain that these measurements revealed the exact diameter. 



Page 46, Line 42. It is the experience of most engineers who have had much to do 

 with current-meter measurements that they can not be depended upon to give 

 satisfactory results where the water is at all turbulent or where the cross section of any 

 stretch of the channel is uneven, thus causing considerable turbulence. The greatest 

 care in rating a meter will not help this very large soiuce of error. The error due to 

 turbulence is greater with the Price meter than with the Haskell meter, which latter 

 was used in the writer's experiments on the 54-inch and 44-inch pipe-hne tests. The 

 measurements were taken by inserting the meter into the exit end of the 54-inch 

 pipe, being held in exact position by a templet and a pin fastened through the upper 

 end of the meter rod. 



Page 47, Line 37. The line of maximxmi velocity within the pipe would be shifted 

 from the center of the pipe to a Line close to that portion of the outside of the pipe on 

 which the convex side of the curve occurs. This Line of maximimi velocity would 

 retain its position for a long distance from the curve and would occur within the 

 length of the pipe tested. 



The writer doubts if this abnormal condition would affect the results, particularly 

 if the manometers were attached in the neutral zone of velocity, as the author states 

 was done. 



