692 EIGHTH PACIFIC SCIENCE CONGRESS 



Probing rate and depth of sampling may be adjusted as desired and 

 operation is automatic. Camera operation is manual at present but 

 may easily be adapted to automatic operation if desired. 



Current Meter 



Since the velocities and distances in the model are both very small 

 compared to those in the prototype, it has proven impossible to use 

 small-scale standard current measuring devices. The present method of 

 current measurement consists of introducing small vortex rings of dye 

 into the water at fixed time intervals and then to photograph their re- 

 lative positions. This method has proved satisfactory and has the addi- 

 tional advantage of measuring both components of horizontal velocity 

 simultaneously. The equipment consists of a glass capillary connected 

 to a dye reservoir through a T section. A rubber bulb, connected to the 

 other junction, is tapped at one second intervals by a hammer driven 

 by a synchronous motor to emit a vortex of dye from the capillary tip. 



Tide and Current Studies 



A comparison of the tidal action in the model with that of the 

 prototype was one of the first detailed studies undertaken as a part of 

 the validation. The phase and amplitude changes between Port Town- 

 send and key locations within the Sound were determined for each in- 

 dividual tidal constituent and compared with corresponding values for 

 the prototype. Within the main basin, the time lag error was of the 

 order of 6 minutes, or 0.3 second actual time greater than the Coast 

 Survey values. Amplitude ratios agreed within 10 per cent. Beyond 

 the constrictions of the Tacoma Narrows and those leading to Bremer- 

 ton, the deviations were approximately double these values. A mari- 

 gram of the six constituents for the first half of 1951 at Seattle was 

 drawn by means of the tide machine using the Coast Survey tidal con- 

 stants. The model tides at Seattle for the same period, generated by 

 the tide machine adjusted to produce the correct tides at Port Townsend, 

 were recorded. Portions of the recorded tides were compared with cor- 

 responding portions of the prepared marigram and with the tide table 

 predictions (Fig. 6). The average deviation of the recorded tidal 

 heights from the marigram was less than ±0.5 foot. Measurement of 

 the deviation in time lag was not obtained. 



Quantitative measurement of the tidal currents and patterns of 

 circulation have not been completed. Visual observations indicate that 

 the model is giving good representation of prototype circulation, current 

 patterns, and velocities, and the eddy patterns appear to follow quite 

 well. 



