466 



DISCOVERY REPORTS 



sheet metal within the cylindrical body of the machine. Where the machine opens for 

 the loading of the spools (at X above and hinged at Y below, see also photographs in 

 Plates I and II) the two faces of the castings of the fore and rear parts fit tightly together 

 below and at the sides of the water tunnel to prevent the escape of water, whilst above 

 there is a narrow slit 1 to allow the passage of the gauze to the driving and storage rollers. 

 The graduated gauze banding winds off the spool C placed below the water tunnel and 

 leading round the small roller D passes through a slit and up across the water stream 

 at E; here it is supported behind by a grid of fine rollers at F. The bottom of the 

 water tunnel is hinged at G, and may be lifted up at H for loading the roller C when 

 the machine is opened ; this movable piece of the water tunnel is held in position by the 



C D' ~Y 



Fig. i . Simplified diagram of the mechanism of the Type I Recorder, 

 clips at the side which may be seen in Plate I. The edges of the gauze banding pass up 

 in recesses in the face of the forward casting, which just give sufficient clearance for the 

 passage of a single thickness of gauze ; the recess on the right-hand side is clearly seen 

 in Plate I. The gauze banding after sieving out the plankton passes through a slit and 

 up between the driving rollers / and K; in passing through the slit it is immediately 

 joined by the second gauze banding which has wound off a spool L placed in a tank of 

 formalin. The driving rollers / and K grip the edges of the two gauze bandings but do 

 not press on the middle part imprisoning the plankton. The two bandings are now 

 wound up on the storage spool M, which is driven by a chain and friction drive from the 

 driving rollers (see general principles on p. 462). The driving rollers are turned slowly 

 by a worm gear through the gear box N from the propeller P. The driving rollers are so 

 situated that the gauze banding coming from the water tunnel presses against the back 

 of the slit through which it passes, the slit being just wide enough to admit the passage 



■ 



of the collected plankton. 



Principal Defects in the Original Machine 

 In spite of many failures in the mechanism, this original machine, with the modified 

 planes, successfully recorded some 2300 miles of plankton during the 1925-7 voyage 

 of the ' Discovery ' (Hardy, 1936). But the machine had many defects. It was too large 

 and heavy, and with the added buoyancy chamber offered too much resistance to the 

 water, necessitating the use of a very heavy towing cable. The spools had to be loaded 

 and adjusted on the deck of the ship ; this was a disadvantage in rough and cold weather, 



1 The flow of water through this slit is negligible, since it leads into a closed cavity when the machine 

 is locked for towing. 



