TIDAL CURRENT METER 
The following article is the compilation of correspondence 
between the Beach Erosion Board and the Bureau of Reclama- 
tion in Denver, Colorado. It is presented to bring the 
findings to the attention of research workers and others 
having an interest in measurement of water velocities. The 
development and testing of modified forms of the Pegram Meter 
was done under the direction of Walter H. Price, Chief, Engi- 
neering Laboratories Branch, Design and Construction Division, 
Bureau of Reclamation, Denver, Colorado. For a discussion of 
the Pegram Meter reference is made to the article "Somervell 
on Effect of Turbulence on Current Meters," Trans. ASCE, Vol. 
95, Pe. 800. 
The Beach Erosion Board and its predecessor in the Corps of Engi- 
neers, The Board on Sand Movement and Beach Erosion, have been interested 
since about 1930 in finding a current meter which would not only give 
reasonably satisfactory measurements with varied flow, but one which 
would also record reversals in flow and currents of very low velocity. 
A meter originally designed by Dean G. B. Pegram of Columbia University 
appears to more nearly approach these requirements. The original Pegram 
meter consisted basically of a very lightweight h-bladed propellor mounted 
in glass bearings on a horizontal shaft. The propellor was made to have 
as nearly neutral buoyancy in water as possible by making a sealed hollow 
hub. Revolutions of the propellor for this meter were counted and recorded 
electrically by fitting two poles on the frame of the meter, insulated 
therefrom, and connecting them to a recording galvanometer. Two opposing 
blades of the propellor were fitted with rubber tips, the passage of which 
past the poles caused a characteristic mark on the recorder. 
The Beach Zrosion Board has made limited use of the Pegram meter in 
its laboratory research studies, and due to the instruments relatively 
delicate and critical structural members, it has never been adapted to exten- 
sive use in the field. However, the Bureau of Reclamation has recently de- 
veloped and made certain modifications to the design of this meter and has 
successfully employed it for measuring flow in channels under tidal influ- 
ence. Facts concerning its development and use of the modified meter were 
recently furnished by the Bureau of Reclamation. 
The meter as modified by the Bureau of Reclamation is usable for more 
applications than the original design because of its more rugged construc- 
tion, but it still employs the basic principles of operation of the Pegram 
meter. The Bureau design was devised to measure the net flow in the Delta 
Cross Channel, which is an artificial channel connecting the Sacramento 
River with Georgiana Slough in the Central Valley of California. Both 
natural waterways are subject to tidal influence, and consequently the flow 
