40 BULLETIN 831, U. S. DEPARTMENT OF AGRICULTURE. 



the siphon and its installation "was never intended for other than 

 regulatory purposes. It may be stated that any other nonautomatic 

 method of control would have presented the same objections found in 

 this case. 



Another case where the siphon was condemned as a failure proved 

 to be its attempted use as a series of " drops " on a canal system, and 

 the principal objection in this instance was its failure to deposit tfee 

 water from the upper to the lower channel in a vertical rather than 

 a horizontal direction, necessitating more protection to prevent scour 

 below the structure. 



It is agreed that the use of a siphon as a substitute for the ordi- 

 nary overpour drop would conserve area and in addition would de- 

 liver vastly more water to the lower level per unit of cross section, 

 but it would also produce a velocity at the outlet so much greater 

 than the velocity developed over an overpour drop that some method 

 of destroying the energy of the rapidly falling water must be pro- 

 vided. It is not evident, however, why the water should not emerge 

 from the siphon in vertical direction as it does in an ordinary drop. 

 It is the opinion of the writer that the use of the siphon as a drop 

 is another case of applying the principle to a foreign use without 

 taking the necessary precautions to provide for its primary factor — 

 accelerated velocity. 



It is hoped that in the near future the more complete study of the 

 structure as a standard design for different conditions, forms, and 

 efficiencies will develop data to permit of its extended use. 



ACKNOWLEDGMENTS. 



The writer wishes to acknowledge the value of information ob- 

 tained from the engineers of the United States Reclamation Service, 

 the officials of the irrigation and power companies referred to in 

 this paper, and to numerous articles published in Engineering News 

 and Engineering News-Record. He is also indebted to Mr. Louis C. 

 Hill, of Los Angeles, and to the gentlemen referred to in the tests of 

 the Throop College of Technology. 



o 



