Dr. Fothergill’s account of ice islands. 71 
of the sea decreases from its surface downwards so far as has yet been 
determined by the deepest soundings, where its coldness reaches the 
freezing point even of salt water, is it not probable that, at greater 
depths out of soundings it may be many degrees below the freezing 
point, and that where congelation is constantly going on, these enor- 
mous masses of ice may be gradually formed stratum super stratum, 
‘attaching themselves to the bottom till, loosened by currents or tides, 
they are detached, and being specifically lighter than water, like air 
balloons increasing in buoyancy in proportion to the increase of their 
surface, they will gradually rise, and at length rear their heads far 
above the surface ? That here, floating in a warmer medium, with 
their summits exposed to sun and rain, the parts above water, ac- 
Gording to the degree of latitude and temperature of the season, 
will gradually melt down to the water’s edge, while the mass below, 
acquiring an increased specific gravity from the act of liquefaction 
above, and from stones or gravel brought up from fete will sink to 
the bottom ? 
Ice islands are not seen any where within the vicinity of the gulph 
stream for an obvious reason, viz. the superior warmth of its current. 
Shallows, as Dr. Franklin first demonstrated, are of a colder tempera- 
ture than deep water. Is not this owing to their vicinity to rocky or 
earthy bottoms, which, being conductors, deprive the water of part of 
its heat 2 May not similar conducting bodies at the bottom of the 
deepest seas, which, for want of proper experiments, are wont to be 
pronounced unfathomable, produce similar effects ? Thus the water 
over the banks of Newfoundland at 46 fathoms is generally found at 
47°, yet a thermometer immersed in the belly of a cod fish just 
srought up marked 37°. This fact I had an opportunity of seeing 
verified i in October 1803. But fishes being warmer than the medium 
in which they live, this fish being 10° colder than the water at the 
