10 BULLETIN 376, U. S. DEPARTMENT OP AGEICULTURE. 



In 1899 tlie same experimenters made additional tests (No. 48) 

 upon the same pipe with improved apparatus.^ Their experiments 

 were centered on a longer reach of pipe and a consistent set of values 

 of n was obtained, ranging from 0.0130 to 0.0133. 



The trend of the discussion of the second Ogden tests shows that 

 a general beUef existed to the effect that the difference in the values of 

 n, when compared with n for smaller pipes, was due to defects in the 

 Kutter formula. 



A graphic presentation of the data then available was made on 

 ordinary squared cross-section paper. In the discussion a method 

 was offered for testing the correctness of experimental data by the 

 use of this paper, "if the loss of head varies as the square of the 

 velocity." 2 Although as long ago as 1808, Dr. Thomas Young ^ 

 suggested that the loss of head was in proportion to the 1.8 power 

 of the velocity, rather than the second power, many still insisted 

 that loss of head must vary as the square of the velocity. It is inter- 

 esting to note that 1.8 is the exact exponent found by both Moritz 

 and the writer, while WiUiams and Hazen use an exponent of 1.85 

 in their general formula for flow in many kinds of pipes. 



In 1901 T. A. Noble * contributed greatly to the available knowledge 

 by making tests on 44^-inch and 54-inch pipes (Nos. 41 and 44), 

 thus bridging the gap between 30-inch and 72-inch pipes. For both 

 these pipes the values of n ranged from 0.0120 to 0.0136, with the 

 higher values in the smaller pipe, although the same water flowed 

 through both pipes and they were constructed at the same time. 

 Also, strange to say, the pipe with the lower value of n contained more 

 curvature and growths of Spongilla which were not present in the 

 smaUer pipe. Noble says: ^ 



The writer can offer no suggestion as to why the value of C should be less and n 

 greater in the 44-inch than in the 54-inch pipe, when, to conform to the results of 

 other experiments, it should be the reverse. 



In discussing the available data on this, subject,® E. W. Schoder 

 of Cornell University suggests the possibihties of an exponential 

 formula derived from a study of the straight-line curves resultiag 

 when the losses of head are platted on logarithmic paper as ordinates 

 and the velocities as abscissas. This was the method used later by 

 Moritz in deriving his formula, and also by the writer as being the 

 best known form by which to study the now extensive number of 

 tests upon wood pipe. 



I Trans. Amer. Soc. Civ. Engin., 44 (1900), p. 34. 

 2Id., p. 73. 



3 Philosophical Trans., Royal Society of London (1808). 



4 Trans. Amer. Soc. Civ. Engin., 49 (1902), p. 112. 



5 Id., p. 143. 

 6Id.,p. 145. 



