Sun apparent diameter 31 minutes 5
seconds. For apparent altitude 4 degrees 24 minutes 57 seconds the mean
refraction is 10 minutes 58 seconds (Mackay's Tables) and the true, found
as detailed above, is 14 minutes 39 seconds which, increasing in the same
ratio as that of the atmosphere at a mean state of temperature, is 43
minutes 57 seconds at the horizon. But the difference of refraction
between the upper and lower limbs increasing also in that ratio gives 48
minutes 30 seconds for the horizontal refraction.
Temperature of the air minus 35 degrees, a light air from the westward,
very clear.
The extreme coldness of the weather rendered these operations difficult
and dangerous; yet I think the observations may be depended upon within
30 seconds, as will appear by their approximate results in calculating
the horizontal refraction, for it must be considered that an error of 30
seconds in the refraction in altitude would make a difference of several
minutes in the horizontal refraction. Mr. Hood's Journal.)
The Aurora Borealis appeared with more or less brilliancy on twenty-eight
nights of this month and we were also gratified by the resplendent beauty
of the moon which for many days together performed its circle round the
heavens, shining with undiminished lustre and scarcely disappearing below
the horizon during the twenty-four hours.
