2i8 SCOTT'S LAST EXPEDITION [June 



ful silk fabrics, meshes running 180 to the inch and materials 

 costing 2 guineas the yard to the German tow-nets for quanti- 

 tative measurements, the object of the latter and its doubtful 

 accuracy, young fish trawls. 



From this to the chemical composition of sea water, the 

 total salt about 3-5 per cent, but variable: the proportions of 

 the various salts do not appear to differ, thus the chlorine test 

 detects the salinity quantitatively. Physically plankton life must 

 depend on this salinity and also on temperature, pressure, light, 

 and movement. 



(If plankton only inhabits surface waters, then density, tem- 

 peratures, &c, of surface waters must be the important factors. 

 Why should biologists strive for deeper layers? Why should 

 not deep sea life be maintained by dead vegetable matter?) 



Here again the lecturer branched off into descriptions of 

 water bottles, deep sea thermometers, and current-meters, the 

 which I think have already received some notice in this diary. 

 To what depth light may extend is the difficult problem and 

 we had some speculation, especially in the debate on this question. 

 Simpson suggested that laboratory experiment should easily de- 

 termine. Atkinson suggested growth of bacteria on a scratched 

 plate. The idea seems to be that vegetable life cannot exist 

 without red rays, which probably do not extend beyond 7 feet 

 or so. Against this is an extraordinary recovery of Holosphera 

 Viridis by German expedition from 2000 fathoms; this seems 

 to have been confirmed. Bowers caused much amusement by 

 demanding to know ' If the pycnogs (pycnogonids) were more 

 nearly related to the arachnids (spiders) or crustaceans.' As 

 a matter of fact a very sensible question, but it caused amuse- 

 ment because of its sudden display of long names. Nelson is an 

 exceedingly capable lecturer; he makes his subject very clear and 

 is never too technical. 



Thursday, June 15. Keen cold wind overcast sky till 5.30 

 P.M. Spent an idle day. 



Jimmy Pigg had an attack of colic in the stable this after- 

 noon. He was taken out and doctored on the floe, which seemed 

 to improve matters, but on return to the stable he was off his 

 feed. 



This evening the Soldier tells me he has eaten his food, so 

 I hope all be well again. 



