AS OBSERVED IN THE WEDDELL SEA. 
823 
Spotted ice .has probably a lower specific gravity than fibrous ice, but the 
Endurance figures at any rate do not prove an invariable difference. They do 
prove, however, that Krummel’s statement that sea-ice has a specific gravity of 0'92 
in the Arctic and 0‘95 in the Antarctic is quite untrue. 
Chemical Changes. — The amount of chlorine present in the various ice-types was 
directly determined by titration with silver nitrate, Mr James being responsible for 
the actual measurement. Results are given not as total salinities but in grammes 
Cl per 1000 c.c. of melted ice. This is made necessary by the fact that the amount 
of salt present relative to chlorine cannot be deduced by formula, as it can in the 
case of sea-water, but must vary, to what extent being at present unknown. To 
have determined the total salinity was quite out of the question on a non-oceano- 
graphical expedition. 
The results showed that : — 
(1) The amount of chlorine initially enclosed (presumably in the form of brine) 
depended probably on the rate of growth — in other words, on the 
temperature at the time of formation. 
(2) Ice in the position of growth ( i.e . unhummocked) slowly became fresher by 
losing its chlorine. 
(3) The chlorine was removed downwards and was not, as previously imagined, 
mainly pressed out on the surface. Just how this took place was not 
quite clear. 
(4) The loss of chlorine in winter was probably slow compared with that which 
took place in summer. 
(5) For ice to become drinkable, it required to be hummocked and exposed to a 
summer’s high temperatures. 
The most important data were obtained from three vertical pits put down in ice 
whose history was known and had been recorded. Those of September 7 and 
October 13, 1915, were put down in ice which commenced freezing and had gone on 
doing so uninterruptedly since February 6 ; samples of ice were taken every 20 cm., 
and examined for structure, salinity, and specific gravity. Those on September 7 
showed invariably fibrous structure ; those on October 13 (in ice of exactly the same 
history, the pit being only a couple of yards away), showed fibrous structure only in 
the lower two-thirds, for in the upper third there was also a tendency towards being 
spotted, which became very pronounced in the topmost sample. These series have 
been plotted diagrammatically, chlorine content increasing towards the right, and 
depth in the water downwards from the top of the page (fig. 9). 
The third series, that of September 14, was collected from ice of a totally 
different history ; the upper layers, formed in the winter of 1914, were spotted in 
structure and discoloured by diatoms ; the middle portion was spotted, but vertical 
lines appeared on a sample being melted ; and the bottom layers were pronouncedly 
