16 
Colorado Experiment Station 
supports on the wells at the same distances from the floor of the 
flume in all cases, or otherwise each flume will require a correction 
for the upper head reading. 
Another practical way of determining the readings is by means 
of a tape and plumb bob, or special weight with a hook attached to 
the side, as shown at (a) Plate II. The steel tape should be re- 
versed in direction ; that is, the zero end attached to the case. A 
small sliding clamp is attached to the tape and when the point of 
the plumb bob, or hook of the special weight, just touches the water 
PLATE II. — Field Installation of V-Notch Venturi Flume and Automatic 
Gage Height Recorder. 
surface, this clamp is then moved downward against a stop, which 
should be located at a point above the floor of the flume equal to 
the distance between the point of the plumb bob or hook, and the 
zero of the tape. The reading indicated on the tape by the clamp 
will be the value of the upper head. To- determine the difference 
in head, it is necessary to provide a fixed scale for the throat gage 
well, reading downward, with the zero at the same elevation as the 
stop for the upi>er gage well. By means of the tape, with the clamp 
reading the upper head, adjust the point of the plumb bob, or hook, 
