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.
During many nights there was a halo round the moon although the stars
shone brightly and the atmosphere appeared otherwise clear. The same
phenomenon was observed round the candles even in our bedrooms, the
diameter of the halo increasing as the observer receded from the light.
These halos, both round the moon and candles, occasionally exhibited
faintly some of the prismatic colours.
As it may be interesting to the reader to know how we passed our time at
this season of the year I shall mention briefly that a considerable
portion of it was occupied in writing up our journals. Some newspapers
and magazines that we had received from England with our letters were
read again and again and commented upon at our meals; and we often
exercised ourselves with conjecturing the changes that might take place
in the world before we could hear from it again. The probability of our
receiving letters and the period of their arrival were calculated to a
nicety. We occasionally paid the woodmen a visit or took a walk for a
mile or two on the river.
In the evenings we joined the men in the hall and took part in their
games which generally continued to a late hour; in short we never found
the time to hang heavy upon our hands; and the peculiar occupations of
each of the officers afforded them more employment than might at first be
supposed. I recalculated the observations made on our route; Mr. Hood
protracted the charts, and made those drawings of birds, plants and
fishes, which cannot appear in this work but which have been the
admiration of everyone who has seen them.
