as indicated in the drawing. This permitted 

 convenient disassembly when necessary. The 

 upper end of the shaft was drilled lengthwise to 

 accommodate the shaft of the synchronous clock 

 motor, and a setscrew affixed to complete the 

 connection. These details are not shown be- 

 cause they vary according to the type of driving 

 unit supplied. The journal boxes were designed 

 to provide a bearing assembly which would mini- 

 mize friction resulting from both rolling and 

 pitching motions of the vessel. 



Preservative Dispenser (Figure 6). 



A pump and microswitch system was in- 

 tegrated with a synchronous motor which was 

 set in phase with the filtering cycle of the samp- 

 ler. Thus after each hour of filtering a given 

 compartment of the filtering pan was flooded 

 and rinsed with preservative, which also covered 

 the silk disk and sample until removal. This 

 dispensing system is simple in principle and of 

 course is subject to many variations according 

 to the need and facilities of the individual 

 investigator. 



The Flow Diagram (Figure 3> 



This diagram indicates the flow of water 

 from intake to waste. The intake was at an 

 average level of 10 feet below sea surface. A 

 stainless -steel pump powered by a 1/3-horse- 

 power motor discharged a total of approximately 

 450 gallons an hour through the system, about 

 one -fourth of which passed through the sampler. 

 The flow could be distributed either to the waste 

 or the sampler as desired by adjusting the 2 

 valves. The total discharge went through the 

 first water meter, and the portion drawn through 

 the sampling apparatus passed through the 

 second water meter. This system permitted the 

 pump to pull water from the sea at a maximum 

 rate, thus increasing the ability of the system to 

 entrain plankters at the intake. The 2 meters 

 permitted a comparison of the amount of water 

 filtered by the sampler with the total water 

 pumped through the system . 



rate of 20 gallons a minute. The manufacturer's 

 stated error at the flow which we used was less 

 than 1 percent. The meters were calibrated 

 while in operation aboard ship by catching the 

 flow in containers of known volume and no error 

 could be detected. It is likely that a small error 

 might have been found if facilities had permitted 

 calibration for great quantities. The synchron- 

 our motor driving the apparatus was a small 

 timing motor with a shaft rotation of 1 revolution 

 in 8 hours. A mercury manometer was con- 

 nected to the water supply near the discharge of 

 the sampling stream . This provided a guide for 

 adjusting the pressure from one run to the next. 



Notes on Operation 



When the vessel cleared the dock and 

 there was no sign of harbor sediments and 

 detritus the pump was started. While the system 

 was allowed to clear itself by discharging through 

 the first water meter only, the silk disks were 

 placed in the filter assemblies, with the excep- 

 tion of one. When this was done the compartment 

 for this last filter was held under the sampling 

 stream and the water was allowed to run through 

 to clear the line and second meter of possible 

 contaminants. Following this the last silk was 

 placed in the filter assembly and the apparatus 

 was started by setting the forward partition 

 (in the direction of rotation) for the first com- 

 partment to just clear the sample stream . At 

 this point the setscrew connecting the filtering 

 pan shaft to the shaft of the synchronous motor 

 was tightened, thus setting the filtering pan in 

 motion . The water meter readings, the time of 

 starting, and the manometer readings were 

 recorded. 



In my experience dense masses of phyto- 

 plankton occasionally caused the silK to clog and 

 a compartment to overflow . The operator should 

 be on the alert for this and other difficulties so 

 that proper entries can be made in the notes. 

 There were times when clogging could be avoid- 

 ed by reducing the rate of flow of water through 

 the apparatus, but this was avoided if possible. 



Miscellaneous 



The water meters were tropic -type disk 

 meters, 5/8 x 3/4 inch, with a safe maximum 



After the apparatus ran 8 hours (1 hour 

 for each compartment) it was stopped for re- 

 placing the silk filter disKS. The plugs in the 

 U -tubes were removed to permit the fluid to be 



