R.R.S. 'DISCOVERY IT loi 



ordinary position square to the towing warp. There is then a symmetrical resistance to 

 the water, and surging is avoided. 



An appliance first used in the ' Discovery II ' in 1933 is a phytoplankton net designed 

 by Mr F. W. Harvey of Plymouth, who has already published a detailed account of it.^ 

 The net is quantitative, the volume of water which passes through it being measured 

 by a vane and revolution indicator fixed near the mouth. Samples of phytoplankton 

 are treated with acetone, and the amount of pigment extracted is measured by corn- 



Fig. 5. Internal closing mechanism for large nets. A, open; B, closed, a, "fishing" part of net. 6, throttling 

 band, c, bridles, d, release gear, e, towing warp. /, stray line. 



parison with a series of colour standards. The net provides a swift and convenient 

 method of comparing the relative abundance of phytoplankton in diflFerent localities, 

 and is in daily use while the ship is at sea. 



In the ' Discovery 11 ' it has been found possible to take vertical hauls with the Young 

 Fish Trawl (TYF), a stramin net with the fore part of large meshed netting to facilitate 

 sinking. The net, mounted on a stream-lined frame 2 m. in diameter, was closed 

 by an inside throttling line (as described above), and was used over the stern of 

 the vessel, suspended from the long derrick boom attached to the samson post. A 

 weight of 180 lb. was employed with this net. The release gear is of a special type with 



1 Harvey, F. W., Journ. Mar. Biol. Ass., n.s., .\ix, p. 761 (1934); Journ. de Conseil, x, p. 179 (1935). 



