168 
GREENLAND VOYAGE. 
of the ice oil the horizon, similar to what occurred 
on the loth and 19th of June. But at other 
times, when repeated, well-defined and proportion¬ 
ate images of ships appear in the air, the vapour 
giving rise to the unequal density, obtains more of 
a stratified arrangement. In its distortive effect, 
it seems to act like clear glass, of unequal surface 
or thickness ; consequently it disfigures all objects 
seen through it. In its looming effect, or that 
property of it by which bodies on the horizon, or be¬ 
yond, appear to be greatly elevated, or suspended, 
as it were, in air, it seems to act by that kind of 
refraction common to other mediums, when the 
density about the object seen is greater than at 
the eye of the observer. The lesser density of 
the air about the observer, arises from the elevated 
position he occupies when at the mast-head, where 
the phenomena are always the most striking. 
Hence, while near objects, which are seen through 
a very rare portion of this vapour, are little or no¬ 
thing elevated: bodies at the distance of the ho¬ 
rizon, which are seen through a mass of it seve¬ 
ral miles in thickness, are elevated ten, fifteen, 
twenty, or even thirty minutes of altitude. And 
when ships or ice within a few furlongs distance 
are disfigured by the action of this vapour, so as 
to present a varying and tremulous outline; other 
similar objects, at the distance of several miles. 
