Dr. Fothergill’s account of ice islands. 79 
ér than the adjacent deep water out of soundings. But the degree of 
depression in the vicinity of ice islands, though a matter of importance, 
which demands particular attention, seems to have been hitherto over- 
looked. The sea water in general, in point of temperature, near the 
surface, corresponds nearly with the temperature of the superin- 
cumbent atmosphere, varying a few degrees higher or lower accord- 
ing to climate and local circumstances,. in summer the air being 
warmer than the sea, in winter the reverse ; but the condensation of the 
atmosphere over mountains of ice, and its rarefaction over the gulph 
stream cannot but sagen affect the eerie as we know the sud- 
den change of temperats the water the tl ymeter. There- 
fore in a matter of such Pikiskquence, mid where the five and prop- 
erty of so many persons are so deeply concerned; we cannot too. ear- 
nestly recommend to all navigators, particularly. in long and hazard- 
ous voyages, the joint use of both imstruments, as a necessary part of 
‘their nautical apparatus. That the temperature of the atmosphere and 
of the ocean at the surface and at different. depths should be daily eXx- 
amined by accurate experiments, and regularly noted in their journals. 
Thus might these two simple instruments-be rendered subservi- 
ent to the: re A oly of metcorology.and the theory of the 
out rocks oer ae ice at a eeacratas hati fail, and where 
neither lunar tables nor even the magnetic needle itself can convey 
the smallest information. 
Recapitulation and Leachate 
From what has been advanced it would appear, that | ice islands 
present a new and ample field of i ipquiry, which i is only a begi vinning 
to be « Bak 
2. That the origin, gees ales ite ae hith- 
erto unknown, may now perhaps admit of a probable explanation, that 
may excite others to complete the discovery- 
