in the artificial channel fluctuates through an imposed tidal cycle. 
Further contemplated use for the meter by the Bureau is the making of 
net flow measurements over a number of tidal cycles in other channels 
of the Delta, thereby obviating large survey crews working for pro- 
longed periods with conventional current meters. Principal require- 
ments governing the development work were to produce a meter which 
would measure flow in either direction without physical rotation of 
the entire meter, and one which would produce a recording so that it 
could operate unattended. The predetermined velocity range was from 
0 to 5 feet per second, the aim being to measure as close to zero 
velocity as possible. Calculations from tidal cycle measurements showed 
that should the meter not indicate velocities under 0.25 of a foot per 
second, less than 1 percent of the net total transferred volume would be 
unrecorded. 
Figure 1 shows the first meter built in the Bureau's shops. This 
meter was installed in the cross channel in the fall of 1952 and func-= 
tioned satisfactorily for a continuous period of five weeks. Figure 2 
shows a further modified design which was used in the summer season of 
1953. The frame as shown by Figure 2 is 11 1/h inches in diameter and 
has been strengthened by adding a circular plate immediately below the 
coupling of the supporting pipe. This plate is of such a diameter as to 
allow anchoring to the stainless steel electrode holders. It serves to 
reduce the moment at the coupling itself by distributing the load to the 
rings at a distance away from it. A stud was incorporated into the coup- 
ling to allow use of l-inch double-strength pipe instead of 1/2-inch pipe. 
In order to prevent loss of the rotor assembly in case floating debris 
breaks a pivot, there is attached to each pivot housing a circular ring of 
stainless steel. Each ring has a slide fastener to position the ring half 
way up and around the hub end of the rotor assembly, but does not, of 
course, have contact with the hub end. 
In an attempt to reduce bearing friction, a synthetic sapphire jewel 
bearing was substituted in the bearing housing for the pivot ball bearing 
of the original Bureau design. Outside dimensions of the bearing housing 
remained the same, but the inside aperture was made to fit the mounted 
jewel as received from the manufacturer. When the jewel is used the pivot 
point must be correctly ground to fit the cup of the jewel. However, 
jewel bearings are no lenger being used in the modified meter, The jewels 
should have an advantage over ball bearings since they would tend to be 
self-flushing and better resist the corrosive action of salt wear. How- 
ever, although wearing qualities under laboratory conditions seemed good, 
in field operation floating debris strikes the meter frame causing a mo- 
mentary distortion which allows the pivots te fall free of the jewel cups. 
Upon springing back into normal position the pivot point is apt to crack 
the jewel. 
In the modified meter shown in Figure 2, the vanes were enlarged, 
new inner end dimensions being 1 inch instead of 7/8 inch, and outer ends 
being 2 inches instead of 1-1/4 inches. The length remained the same. 
Spacing between the insulator and the electrede was set at 0.03 of an inch. 
