108 
GREENLAND VOYAGE. 
the value of the extraordinary refraction, at the 
time the land was thus seen; or, calculating in the 
proportion of the distance, which is the most usual 
manner of estimating the refraction, it amounted 
to one-fourth of the arch of distance, instead of 
one-twelfth, the mean quantity. 
That land was seen under these circumstances 
there cannot be a doubt; for it was observed to 
be in the same position, and under a similar form, 
on the 18th, 23d, 24th, and 25th July 1821, 
when the ship was in longitude from 12° 30', to 
IT 50' W., and on the 23d it remained visible 
for twenty-four hours together; and though often 
changing its appearance, by the varying influence 
of the refraction, it constantly preserved a unifor¬ 
mity of position, and general similarity of cha¬ 
racter. In my journal of this day, I find I have 
observed, that my doubts about the reality of the 
land were now entirely removed, since, with a te¬ 
lescope, from the mast-head “ hills, dells, patches of 
snow, and masses of naked rock, could be satisfac¬ 
torily traced, during four-and-twenty hours suc¬ 
cessively.” This extraordinary effect of refraction, 
therefore, I conceive to be fully established * 
* I am not aware that this land was ever seen by any 
British navigator, (excepting Hudson, and two or three 
whale-fishers, who have, at different times, been forced to¬ 
wards it by the ice, when closely beset), until the year 1817 
