METHODS OF OCEANOGRAPHICAL RESEARCH 267 



are obtained by means of a pump and rubber hose let down 

 to the desired depth, or, better, in the water bottle 

 mentioned above for the collection of water for chemical 

 examination. The water is then placed in small glass 

 tubes, which taper to a blunt point at the bottom end, 

 and centrifuged for two or three minutes. The surface 

 water is then poured out of the tubes and the little drop 

 that remains at the bottom contains the minute plankton 

 organisms. This drop of water is sucked oft with a glass 

 pipette and spread evenly over a glass slide with squares 

 ruled on it which can then be examined under a microscope 

 and the organisms present in a given number of squares 

 counted. 



Much interesting work on the geographical distribution 

 of plankton can also be done on ocean liners. If small 

 silk filters be hung under the salt-water tap in the bathroom 

 many of the surface-living animals and plants can be 

 obtained. 



One of the most important items in the equipment for 

 oceanographical research is naturally a research ship. On 

 big expeditions a vessel of large size is necessary if the 

 object is to study the physical and biological conditions 

 over extensive areas and at all depths. There must be 

 plenty of space to stow the many and varied instruments 

 and nets. A steam-driven winch capable of holding 

 several thousand fathoms of strong wire cable has to be 

 used for working the nets at great depths, and probably 

 one or two smaller ones for working small plankton nets, 

 sounding, and collecting water samples. Space should be 

 available on board for a working laboratory in which the 

 collections can be sorted and preserved, and accommodation 

 should be provided for a small library of the most necessary 

 works of reference for the identification of animals and 

 plants. 



