R.R.S. 'DISCOVERY II' 105 



tube, and the standardization of the storage of vertical plankton samples is a further 

 advantage. These jars are kept in wooden boxes containing two trays, each of sixty 

 bottles, and as explained on p. 93, a cupboard in which the trays can be stored is 

 provided in the biological laboratory. 



Neutralized formalin and 75 per cent, alcohol are the preservatives most generally 

 used. 



In an earlier volume (vol. I, p. 219) we noted that paraformaldehyde was liable to form 

 in the strong formalin used in the research ships, and that considerable quantities had 

 thus been rendered useless. This difficulty, possibly though not certainly due to the low 

 temperatures to which the formalin is exposed, has now been overcome with the as- 

 sistance of Mr Arthur Ashworth, the manufacturer. He has supplied formalin with an 

 increased alcohol content, and consequently with a reduced specific gravity, which has 

 shown no tendency to polymerization when stored on board. 



Distilled water for use in both laboratories and for photographic purposes is provided 

 by a small steam-heated still of Brown's make which is fitted at the top of the engine 

 room just inside the port door. The cooling of this still is by salt water, but the water 

 distilled is from the ordinary fresh water supply. 



Sund's slide rule is used for the direct determination of a, (density at the temperature 

 of observation). This is an essential operation and the method is quicker and more 

 accurate than the use of tables. 



