18 



BULLETIN 194, U. S. DEPARTMENT OF AGEICULTURE. 



Column 10 shows the method of securing all depth determinations from which areas 

 and perimeters were secured. 



ON refers to office not^s. Taken in connection with elevations secured at time 

 of test. 



SG refers to a special gauge of some form. Those noted were quite accurate. 



LR refers to a difference between level readings on a rod. This obviates all defects 

 of water climbing up the rod, and is the best method, in the opinion of the writer. 



S refers to soundings with a graduated stick or rod and although quite accurate in 

 low velocities is uncertain where water climbs up the rod. 



T refers to measurements by 



Water Surface 



tape on the outside of a flume. 



Column 14 shows the method 

 of securing the discharge meas- 

 urement. 



M refers to a current meter. 

 I signifies the integration 

 method was used. Extensive 

 tests showed that full weight may- 

 be accorded this method. 



VC signifies that the mean ve- 

 locity was secured by means of 

 the multiple-point method in- 

 terpreted through vertical ve- 

 locity curves. 



— 2-f-8 signifies the mean of the 

 velocities obtained at 0.2 and 0.8 

 depths in each vertical was ac- 

 cepted as the mean of the vertical. 

 Extensive experiments showed 

 this method may be given full 

 weight. 



—6 signifies the velocity ob- 

 tained at 0.6 of the depth below 

 the surface was accepted as the mean for the vertical. Extensive experiments show 

 that the results of this method as a rule are too high and for this reason tests made in 

 this manner are not given full weight. 



RC signifies the discharge was taken from a rating cmve. 

 W refers to a weir measurement, under standard conditions. 

 C after the W signifies that a trapezoidal or Cipolletti weir was used. 

 Column 15 shows the typical shape of the vertical velocity curves, referred to in 

 figvtre 3. 



Column 23 shows the various wind conditions : C signifies calm; U signifies upstream; 

 D signifies downstream; and A signifies across. 



Where of sufficient importance to seriously affect results, additional 

 information is given in the text. 



The other columns are considered self-explanatory. 



Fig. 



3. — Typical vertical velocity curves and depths at 

 which meter was held. See column 15, Table 1. 



