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 the 
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 destrojung 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 Eeclamation 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 
