GENERAL DESCRIPTION 469 



wheels. To have placed it centrally would have meant an increase in the width of the 

 machine and wasted space on the left ; the reduction in size and the resistance to the 

 water are considered of great importance in a machine which may be used from com- 

 mercial ships at speeds up to 15 knots. The movable frame holds all the mechanism 

 except the gear box, which is fitted in the roof of the box body. When the frame is slid 

 into position the worm from the gear box engages with cogs on a gear wheel on the right- 

 hand end of the forward driving roller (Figs. 8,11); this gear wheel engages with another 

 on the rear driving roller which in turn drives a series of gears incorporating a special 

 friction drive rotating the storage spool placed within a preservation (formalin) tank. In 

 addition to the section, plan and elevations shown in Figs. 8-13, perspective drawings 

 of the internal mechanism are provided in Figs. 14-16. The lettering is common to all 

 these figures which are placed for more ready reference in the section dealing with the 

 detailed description (pp. 472 to 488). 



The graduated gauze banding winds off a spool h placed below the tunnel, passes 

 back round a small roller / and up through a slit to traverse the water tunnel. In 

 crossing the tunnel it sieves out the plankton and is supported behind by vertical bars 

 and small horizontal rollers (Fig. 13). It leaves the tunnel by a slit and is immediately 

 joined by the second gauze banding which has wound off a spool g placed above the 

 water tunnel. The two spools, from which the bandings wind, rotate on spindles which 

 may be slid out from the right-hand side to allow the removal of the spools ; when loaded 

 these spindles are held in place by a spring clip i on the right-hand side (Figs. 8, 14). 

 The tension on the bandings may be adjusted by means of spring tongues k acting as 

 brakes on the ends of the spools. 



The two gauze bandings, having met, pass up together between the driving rollers m 

 and n which grip them tightly at their edges by means of the blunt teeth on roller n pressing 

 into the rubber ends of the other roller. These rollers only meet thus at their ends, 

 leaving a gap between for the rest of their length to allow the plankton imprisoned 

 between the gauze bandings to pass through without being unduly crushed. The 

 bandings pass on together on to the storage spool r which is placed inside the tank q 

 which is filled with a 20 per cent formalin solution. This spool may be removed by 

 sliding out a spindle on the left-hand side after the removal of a cap which holds it in 

 position. The storage spool is driven by the slipping friction drive (described in detail 

 on p. 481), so that it just takes up the slack on the gauze bandings as they issue from the 

 driving rollers (see general principles, p. 462). The bandings are lifted off the rear 

 driving roller by a series of comb-like teeth which project from the lip of the entrance 

 to the formalin tank, and fit into grooves in the roller (see Figs. 11,13,14). The lid of the 

 formalin tank is lined with rubber which when closed by the rod qo makes a watertight 

 joint at the sides and back ; there is a narrow gap in front between the lid and the lip 

 for the entry of the gauze bandings. The escape of formalin through this entry is 

 largely prevented by the soft rubber lining to the lid extending out beyond the lid to 

 press lightly on the incoming bandings. Nevertheless, some loss of formalin takes place 

 when the machine is immersed in water ; but this loss is made good by the slow diffusion 



