148 Proceedings of Royal Society of Edinburgh. [mar. 21, 
surfaces of the icebergs large enough to reach to the depth of 300 
fathoms would suffer any melting at all. The existence of the cold 
stratum was ascribed wholly to the cold brine, separated from the 
ice on the freezing of the sea-water, sinking downwards with an 
initial temperature of from 28 0, 5 to 29° F. This cause, though 
existing and in operation, is quite inadequate to produce the effect 
observed. The facts related in the preceding paper furnish a com- 
plete explanation of the cold wedge of water in the Antarctic Ocean 
and the dependence of its thickness and temperature on the range 
of icebergs. These enormous islands of ice, a very large proportion 
of which rise in tabular form to a height of 200 to 300 feet above 
the sea, float in many cases with their lower surfaces at a depth of 
from 250 to 300 fathoms. The warmer and denser water coming 
from lower latitudes (see Challenger Narr ., vol. i. p. 428) bathes 
these lower surfaces, the temperature of the mixture at the surface 
of contact falls, the heat abstracted from the sea-water melts a cor- 
responding amount of the ice of the iceberg, and a saline solution is 
produced, less salt, and therefore lighter than the water away from 
contact with the iceberg, and having a temperature which depends 
immediately on the strength of the resulting solution. Being lighter 
than the surrounding water, this resulting solution necessarily flows 
up along the sides of the berg to the surface, and its place is taken 
by fresh undiluted sea-water, which in its turn is cooled, diluted, and 
transferred to the surface. The result is the production of a means 
of circulating and of cooling and equalising the temperature of 
the water within the reach of icebergs. As there is continual 
renewal of the ocean water brought into contact with the ice, and 
as its composition is constant, the temperature produced is practi- 
cally constant, namely, 28°*8 to 29 o, 0 F., or - l°-7 to - 1°*8 C. 
The layer of lighter water from 50 to 80 fathoms thick at the 
surface is due principally to this melting of land-ice, though it is 
also due in small proportion to the melting of sea-ice. 
Table giving the Temperature at which Ice melts in Sea-Water 
containing different percentages of Chlorine. 
Temp. C., 
. i°-o 
1°T 
l°-2 
l°-3 
l°-4 
Per cent. Cl, 
. 1-040 
1-131 
1-222 
1-313 
1-404 
Temp. C,, 
. l°-5 
l°-6 
l°-7 
l°-8 
l°-9 
Per cent. Cl, 
. 1-495 
1-586 
1-678 
1-769 
1-880 
