120 FLORIDA GEOLOGICAL SjURVEY—THIRD ANNUAL REPORT. 
point of the dome of water above, in a strictly vertical direction 
—a to b in the diagram. Then these distances may be found in 
the table and the corresponding figure will give the number of 
gallons discharged per minute. The blowing of the wind need 
not interfere in this case as long as the measurements are taken 
vertically. 
- “The method for determining the discharge of horizontal pipes 
requires a little more care. First, measure the diameter of the pipe 
as before, then the vertical distance from the middle of the open¬ 
ing of the pipe,, or some convenient point corresponding to it on the 
side of the pipe, vertically downward six inches —a to b, then 
from this point strictly horizontally to the center of the stream— 
b to e. With these data, the flow in gallons per minute may be 
obtained from the table. It will be readily seen that a slight error 
may make much difference in the discharge. Care must be taken 
to measure horizontally and also to the middle of the stream. 
“Because of this difficulty, it is desirable to check the first deter¬ 
mination by a second. For this purpose, columns are given in the 
tables for corresponding measurements twelve inches below the 
centre of the pipe. Of course, the discharge from the same pipe 
must be the same in measurements of the same stream. In this 
: i. : ; 1 
case, the occurrence of wind, blowing, either with or against the 
water, may vitiate results to an indefinite amount, therefore mea¬ 
surements should be taken while the qir is still. 
7 The flow of pipes of diameters not given in the Table II., may 
be easily obtained for corresponding measurements, as follows: 
For inch, multiply discharge of T-inch pipe by .25 ; for J^-inch, 
by .56; for 1 % -inch, 'by 1.56'; for 1^-inch, by 2.25. For 3-inch, 
multiply 2dnch pipe by 2.25; for 4-inch, by 4 ; for 5-inch by 6.25; 
for 6-inch, by 9; for 8-inch by: 16. . < ■ ; ^ 
“In both the§e ; tables it has not been thought, necessary to make 
any allowance for the resistance, of the atmosphere. Doubtless 
when the velocity of . the stream is great, the resistance is con¬ 
siderable ; butas the. pressure checks (the flow, and our object - is 
simply to measure the amount of flow, it need not be taken into con¬ 
sideration. In case pipes are ! f ound of diameters not*- correspond- 
iflg toThe table, the 1 same rule may be applied as in the first case: 
1 fI Whehevefl 'ffactions Occur in the height of horizontal distance 
of the stream; the number of gallo'ns may be obtained by dividing 
the difference between the readings .in the jtable for,the. nearest 
whole ndm^m;a&ofdin^tojffie size 0^ the fraction. For example, 
ifThb'distaiirce^froiTT the’tdj) 6f the pibe’to the top Of the stream, in 
