Wave velocity measurement.— Wave velocity was measured by timing 

 the passage of a wave crest over a measured baseline. Float-operated 

 mercury switches in electrical circuits flashed neon bulbs on a panel to 

 trace the progress of wave crests. A two-way switch and a key 

 permitted selection of a wave crest for measurement. A solenoid in 

 the electrical system automatically started and stopped a stop-watch 

 and the wave crest closed the circuit at the beginning and endmg of 

 the course. 



Photographs. — A Retina II-f2 camera and a 16 mm. Eastman Cine 

 Special motion picture camera comprised the photographic equipment. 



Profiles against a 6- inch grid on the wall of the tank were photo- 

 graphed with both cameras. 



Particle motion shown by injecting drops of a fluid mixture having 

 the same specific gravity as water was photographed at the window 

 at the center of the tank. Still exposures and motion pictures were 

 made. 



The fluid used was a mixture of xjdol and butyl phthalate colored 

 with zinc oxide. Injection was made with a glass tube having a small 

 orifice at one end and a rubber bulb at the other. A scale on the 

 tank window served for the measurement of orbit dimensions. 



Wave period. — The wave period was computed from the average 

 period of several trains of waves. 



Measured wave length. — The movable point gage was adjusted to 

 obtain synchi'onous flashes for an even multiple of wave length. The 

 number of waves measured was noted by visual observation, and the 

 average length of wave thus measured was recorded as the wave length. 



Measured wave velocity. — The wave travel was timed over a 30-foot 

 course. The velocity in feet per second was obtained by dividing 

 the length in feet by the time of travel in seconds. 



Measured wave height. — Three combination hook and point gages 

 were set at 12, 24, and 37 feet from the wave generator. In general, 

 each point and hook was read to still water level before the beginning 

 and after the end of the run. During each run, five readings were 

 made. The average was taken for each gage, and the wave height 

 recorded was the average for the three positions. Readings are to 

 thousandths of a foot. 



Wave profile. — The wave profile against the measured grid on the 

 tank wall was scaled from the enlarged photograph of the wave. The 

 ordinates were measured at the tenth points of the wave length and at 

 additional points a twentieth and a fortieth of the length each side 

 of the wave crest. 



Orbit radius. — The measured value of the orbit radius was taken as 

 one-fourth the sum of the horizontal and vertical diameters of the 

 particle orbits obtained as described under "Photographs." The 

 diameters were measured between vertical and horizontal tangents 



