{X. 
ON THE ORIGIN AND FORMATION OF ICE ISLANDS AND THEIR 
DANGEROUS EFFECTS IN NAVIGATION, 
— out a certain and easy method of timely forewarning seamen 
of their approach, even in the darkest nights. 
By A. FOTHERGILL, m. pb. F.r.s. a. P.s. &e, 
——DIES DOCEAT<—— 
INTERIM “ CAUTELA NON NOGET.” 
sate 
AS” no pitlosophical Pere Prurtsaly written on the origin and 
formation of ice islands has yet appeared, the subject may be consid- 
ered in a great measure as untouched. The present attempt, with so 
few materials, will doubtless be deemed as bold as it is novel. _It is 
therefore not without diflfidence, that I venture to lay it before this 
tearned society, whose candour, however, will plead for its imperfec- 
tions. = 
These enormous bodies are distinguished by mariners according 
to their apparent magnitude into continents, islands, and fields of ice, 
extending often to a vast distance, as far as the eye can reach from the 
mast head ; some of which have been computed to be above a mile long 
and 200 feet high above the surface of the water, which is considered 
as only one fourteenth of their extent under water. How amazingly 
great then must be the real bulk of such islands, or rather continents of 
ice! They have been found within 36° or 37° south of the 
equator, and 39° or 40° north. In the year 1805 from April to June 
they occurred more frequently in the Atlantic Ocean, and particularly 
near the banks of Newfoundland, than had ever beenremembered be- 
