82 BULLETIN 376, U. S. DEPARTMENT OF AGEICULTURE. 



The reference of the author (p. 25) to the watches being exactly set together leads 

 one to infer that a comparison was made at the conclusion of the experiment to deter- 

 mine how closely they had continued to run together. If this was not done there is 

 a possibility of a small error in time due to the varying rate of the watches. It is not 

 an uncommon thing to find two watches to run several seconds apart in the course 

 an hour, although in the course of a day the difference may be inappreciable. 



It would add materially to the value of the paper as a record of experimentation if 

 the author would give some details as to the general measurement of the water and 

 also a sketch of the weir used, showing the method of attachment and location of the 

 stilling box. The measurement of the quantity of water is fully as important as the 

 measurement of the loss of head, and it depends upon the precision of the measure- 

 ment of the head, and upon the accuracy with which the weir is constructed in con- 

 formity with previously used experimental examples. 



With the information as it stands in the paper it is impossible for one to determine 

 whether the weir measurements are to be relied upon within 2 per cent or within 10 

 per cent. 



The rating of the submerged weir by means of a current meter in a tailrace is per- 

 haps the least accurate experimentation recorded in the paper. The use of a current 

 meter in a tailrace is very unsatisfactory and its indications are liable to be in error 

 anywhere from 10 to 20 per cent. If the wheels in question were reaction turbines it 

 would be possible to get a considerably more accurate determination of the flow by 

 reference to the gate openings and head on the wheels during the test in question. 

 If this were compared with Holyoke tests on similar wheels a determination of the 

 water could probably be arrived at within 3 or 4 per cent. 



The investigation of inlet losses described by the author (p. 63) may be subject to 

 error because the distance from the inlet to the place of measuring the head is prob' 

 ably too short. Had the measiirement of head been taken 4 or 5 diameters down the 

 pipe it is quite probable that the apparent loss would have been less than that shown 

 at the point where the author observed, by reason of the fact that a contraction of the 

 stream is formed at the entrance which causes an eddy to lie along the wall and this 

 in experiments by the writer was found to extend for some 12 to 15 diameters down- 

 stream. The distance to which this might extend, in a large pipe is probably less 

 than that in a smaller one, but it seems questionable if the length of 3 diameters was 

 sufficient to eliminate it even in the large pipes considered. 



A statement is made (p. 65) that low discharges entrain more air. This statement 

 is apparently in error. The lower discharges release more air from the water which is 

 flowing through the pipe and hence more air is apparent along the top of the stream 

 and at places where it may accumulate, but rapidly flowing water will absorb and carry 

 with it more air than the more slowly flowing, and this is the reason that the air does 

 not appear at high discharges. 



As to the author's comparisons of carrying capacity of wooden-stave and cast-iron 

 pipe it is to be said that the values of the coefficient recommended for different ages 

 in the Williams and Hazen formula are believed by its authors to be very conservative. 

 With the modem coated cast-iron pipe, if well laid, it is doubtful if a coefficient less 

 than 115 will be found at any age unless the coating has been damaged. 



In closing it gives the writer pleasure to express his appreciation for the very work- 

 manlike manner in which the observations reported by the author have been 

 conducted. 



Mr. Noble: Page 58, line 16, and page 60, line 17. The velocity head and the 

 entry head at the entrance may or may not be lost head, depending upon the shape of 

 the approach to and the exit from the pipe Line. This loss may be entirely eliminated 

 by making the first section and the last section of the pipe funnel-shaped, the small 

 end being joined to the pipe in each case. The large end must be sufficiently large 

 that the velocity at the entrance will produce a negligible velocity head (see Francis', 



