lar observation are given at the
bottom of the page[3].

[3] "The observed meridian altitude of [.0] upper limb was 2 deg. 52' 51".
Temperature of the air -45 deg. 5'{2}. By comparing this altitude,
corrected by the mean refraction and parallax, with that deduced
from the latitude which was observed in autumn, the increase of
refraction is found to be 6' 50", the whole refraction, therefore,
for the altitude 2 deg. 52' 51" is 21' 49". Admitting that the
refraction increases in the same ratio as that of the atmosphere
at a mean state of temperature, the horizontal refraction will be
47' 22". But the diameter of the sun measured immediately after
the observation, was only 27' 7", which shews an increase of
refraction at the lower limb of 3' 29". The horizontal refraction
calculated with this difference, and the above-mentioned ratio, is
56' 3", at the temperature -45 deg. 5'. So that in the parallel 68 deg.
42', where if there was no refraction, the sun would be invisible
for thirty-four days, his upper limb, with the refraction 56' 3",
is, in fact, above the horizon at every noon.

The wind was from the westward a moderate breeze, and the air
perfectly clear. January 1st, 1821. Observed meridian altitude of
[.0] lower limb 2 deg. 35' 20". [.0] apparent diameter 29 deg. 20'. For
apparent altitude 2 deg. 35' 20", the mean refraction is 16' 5"
(Mackay's Tables), and the true, found as detailed above, is 20'
8": which increasing in the same ratio as that of the atmosphere,
at a mean state of temperature, is 41' 19" at the horizon. But the
difference of refraction at the upper and lower limbs, increasing
also in that ratio, gives 55' 16" for the horizontal refraction.
Temperature of the air -41 deg.. Wind north, a light breeze, a large
halo visible about the sun. January 15th, 1821.--Observed an
apparent meridian altitude [.0] lower limb 4 deg. 24' 57". [.0]
apparent diameter 31' 5". For apparent altitude 4 deg. 24' 57", the
mean refraction is 10' 58" (Mackay's Tables), and the true, found
as detailed above, is 14' 39", which, increasing in the same ratio
as that of the atmosphere at a mean state of temperature, is 43'
57" at the horizon. But the difference of refraction between the
upper and lower limbs increasing also in that r