4 BUHLETIX 854, U. S. DEPAETMEXT OF AGEICTJLTUKE. 
For comparison, 69 tests were made on 10 and 12 inch tile, so laid 
as closely to approximate poorly laid drains as found in the field, 
to show the results of using unskilled workmen in laying drains 
without proper supervision. Nine experiments were made upon the 
loss of head in catch-basins, using 8-inch clay tile. Grades of 0.20? 
0.75, and 1.50 per cent were tested, with drops in the catch-basin of 
0.10, 0.20, and 0.30 foot for each grade. 
The investigations were made at Arlington, Va., in 1916 and 1917. 
The experimental plant was designed and constructed by S. W. 
Frescoln, drainage engineer, and the tests were made by D. L. 
Yarnell, senior drainage engineer, under the direction of S. H. 
McCrory, chief of drainage investigations. S. M. Woodward acted 
as consulting engineer for the investigation, making suggestions in 
the conduct of the experiments and collaborating in the preparation 
of the data and report. 
This report upon the investigation of flow in drain tile includes a 
detailed description of the equipment and methods used and the 
tabulated data from the experimental work. The results deduced 
from the data are shown graphically, the method of developing the 
curves being explained. The formulae now in general use for com- 
puting velocity in tile are discussed and comparison is made with the 
new formula presented. A diagram is given showing discharge capaci- 
ties based upon this formula, covering sizes from 4 to 48 inch tile, 
and grades from 0.04 to 3.00 per cent. 
So far as the writers have been able to learn, only one other similar 
investigation of this subject has ever been made. This was by 
Messrs. J. F. Rightmire and M. E. Chappel and was quite limited in 
extent (see Vol. IV, No. 4, Bulletin of the Iowa State College Engineer- 
ing Experimental Station). 
CONCLUSIONS. 
The foilo^^'ing general conclusions have been drawn after a detailed 
study of aU of the experimental data: 
(1) That the value of the coefficient of roughness, n, in the Kutter 
formula, as obtained by experiments in a drain or pipe at any depth 
of flow less than full, does not necessarily apply to that drain or pipe 
when flowing full. 
(2) That the exponent of the slope, s, is practically 0.5. In other 
words, the loss of head is in proportion to the 2.0 power of the velocity 
and not the 1.8 power, as given by many authorities. 
(3) That the exponent of the mean hydraulic radius, R, is 2/3. 
(4) The Chezy formula gives the same velocity of flow in a pipe 
flowing one-half fuH as in one flowing full, ^yith. the grade constant. 
The experimental data obtained seem to disprove this commonly 
accepted theory. 
