CURRENT METERS 



-I KMI Ul lie added to each reading on the rod when sounding. In 



i t<> prevent ili.- -.mi. hug rod Mtikm into the bed of the 

 ittream, t -l""iM in- j,i.,\ ,,1,-,1 with a fboe at least 3 inches in 

 ii.u \\h.-n using the rod care should always be taken 



tii.it the reading li, on ao-ount ..i tin- impinging 



i ninnm- up ih.- i...l. It >( -.miding rod -r lim- i* used, 

 ili- ni. -t ! not being attached, the soundings are made at all 

 iin-.i-.in mi; ; e observing the \e|<M-itiea. 



The soundings from bridges <n . .il.l.- .u* usually made* with 

 tli.- \\eiu-hi and line. .in<l in such cases, with swift water, a bead 

 lin. is used to hold id-- in- i. -i in a vertical position to prevent 

 . due to the weight being carried down the stream or to the 

 MI: "i ili- IIM.-. Sounding \Mih ih,- line are most readilv 

 t.tk.-n .t- I olio**: '1'ln- weight .ind HIM- are l.\s.-r.-d until th- 

 weight (OIK h<> tin- bed of the river directly under the measuring 

 point .in.l. \\ith the line tant. a point is marked on it by grasping 

 it \\ith ili.- fingers opposite a fixed point on the bridge or car; 

 the weight is then wised until it ju-t t.u. -hi - the surface of the 

 water and the length of the >oundm line th.it passes the fixed 

 point i- in. asured. This length is measured by placing the end 

 of a linen or metallic tape opposite the fixed starting point on 

 the sounding line, grasping hoth the line and the tape in the 

 li.tn.U. and drawing up the line and tape without permitting 

 them to slip on eaeh other until the weight reaches the surface 

 of the water. The length of line thus drawn up, representing 

 the depth ..I the \\ater. i- then read direrlK from the tape. This 

 PI.-. i -ii lenient can usually be made by one person with sufficient 

 accuracy, even \\li.n the water is from 10 to 12 feet deep. On 

 the U. S. Geological Survey standard cable car a scale is fixed 

 to the frame of the car f<>r measuring the depth. 



\ I.I <M IM MIIM.I;\ \TIONS 



In making a \eloeii\ measurement, the meter i> held at the 

 point in the stream at \\hieh it is desired to ascertain the \el 

 of the eurrent. The wheel i- allowed to re\ol\e for .1 

 seconds, in order that it may adjust it-elf to the eurn-nt. after 

 whieh the time for a given number of revolution- i- n..t.-d. ami 

 the velocity is obtained from the ratim: table for the n 

 The run should be from 40 to 70 sec.; the number of revolutions 



