A mechanism was devised at the POFI 

 laboratory for blocking the flowmeter blade 

 when the net was closed (fig. 3). Repeated 

 tests giving zero readings on the flowmeter 

 when the net remained closed gave us confi- 

 dence that the device was effective and reliable. 



The releasing mechanism, system of 

 bridle lines, and method of opening and closing 

 the nets, were essentially as described by 

 Leavitt (1935) , with some modification by O. E. 

 Sette. J. C. Marr, and E. H. Ahlstrom. In 

 figure 4 we have attempted to illustrate the 

 method of rigging the 2 lower nets and the 



may be adjusted to suit the method of launching 

 the nets, height of deck above water, etc. A 

 150 -pound streamlined weight was attached to 

 the end of the towing cable. 



As the field party had not had previous 

 experience with this type of multiple -net gear, 

 some difficulties were experienced which re- 

 sulted in the loss of a snnall percentage of the 

 samples, and a few were judged of qualitative 

 value only. The majority of the hauls, however, 

 were accomplished satisfactorily. All samples 

 of doubtful quantitative value have been omitted 

 from table 3. 



(A) 



_j^i_ 



_^e; 



(C) 



10 FEET 



10 FEET 



1 1 '/; FEET 



'^L 



^mr 



3 '/J FEET 



FLOW METER 



Figure 4. --Operation of the 1 -meter closing nets showing the arrangement and dimensions 

 of the bridle lines. A - net closed for lowering; B - net open for towing; C - net closed 

 for raising; mi - first messenger; m2 - second naessenger; rj - primary release; r2 - 

 secondary release. 



opening and closing operation. Part A shows 

 the arrangement of bridle lines leading to the 

 release mechanism with the net closed while 

 being lowered. In figure 4B the net is shown 

 in open position after the first messenger (m|) 

 has triggered the primary release (r^). In 

 figure 4C the net has been closed following the 

 action of the second messenger (1112) on the 

 secondary release (r2). The bridle lines as 

 shown in the figure were of convenient length 

 for use on the Hugh M. Smith . The dimensions 



200-300 m. Hauls 



In these "deep" hauls a single closing 

 net was lowered closed to an estimated 200 

 meters' depth, opened, then lowered at a slow, 

 uniform rate to an estimated 300 meters. It 

 was then returned to about 200 meters, closed, 

 and brought rapidly to the surface. As in the 

 other methods of hauling, the wire angle and 

 amount of wire -out were recorded at 2-minute 

 intervals. By means of the depth gauge 



