Figure 0-2. The half -meter qualitative plankton net. 



0-7 Assembling and Operating the Clarke- 

 Bumpus Sampler. — The Clarke-Bumpus sam- 

 pler consists essentially of a frame that attaches 

 to the lowering wire, a brass main tube (5 

 inches in diameter and 6 inches long) that con- 

 tains a shutter and impeller, a plankton net 

 about 3 feet long, and a sample bucket (fig. 

 O^). A screwdriver and a small adjustable 

 wrench are the only tools required to assemble 

 and operate the sampler. 



Stej) 1. Attach the net to the sampler, and 

 fasten the sample bucket to the cod end of the 

 net with the screw clamps. Then, install the net 

 rod to keep the net open and to prevent it from 

 becoming fouled on the instrument or lowering 

 wire durmg towing. 



Step 2. Set the shutter (A) in the closed 

 position; then rotate it 90° counterclockwise, 

 looking down on the sampler. At the same time, 

 rotate rod (B), clockwise until the edge of the 

 shutter engages the first of the two finger lugs 

 (C). At this point, the tripping mechanism 

 should engage finger lugs (D) locking the 

 shutter open. 



Step 3. Next rotate the shutter (A) through 

 a second 90° arc, and also rotate the shutter rod 

 (B) clockwise as before until a second finger 

 lug (C) engages the semicircular frame on the 

 shutter, which now is closed, and a second finger 

 lug (D) engages the tripping mechanism. 



Figure 0-3. Clarke-Bumpus quantitative plankton 

 sampler. 



Step 4. Shackle a 100-pound lead weight to 

 the %2- or %6-ii^ch lowering wire and lower the 

 weight over the side into the water. 



Step 5. Connect a safety line to the sampler 

 to prevent the accidental loss of the instrument 

 while attaching it to wire. Secure the wire 

 clamp (F) to the lowering wire, and attach the 

 sampler to the wire by means of the spring pin 

 (G) at the top and gate lock (H) at the bottom. 

 The frame should swivel freely around the 

 wire. 



Step 6. Record the reading of the digital 

 counter, remove the safety line, lower the sam- 

 pler to the desired depth, and commence tow- 

 ing. Drop a messenger to open the shutter and 



0-3 



