, an officer was
detailed to trace a line of levels from the base of the monument marking
the source of the river St. Croix to tide water at Calais, in Maine, by
which means the elevation of the base of the monument above the planes
of mean low and mean high water, and also the elevations of several
intermediate points of the river St. Croix on its expanded lake surface,
have been accurately ascertained.

Another officer was at the same time charged with tracing a line of
levels from the base of the same monument along the due north line
as marked by the commissioner, by which it is intended that every
undulation with the absolute heights above the plane of mean low water
at Calais shall be shown along the whole extent of that line.

At Parks Hill, distant only 12 miles from the monument, a second station
for astronomical observations was established, and a camp suitable for
that purpose was formed. On the 26th day of October, whilst occupied in
completing the prolongation of the meridian line to that point and in
establishing a camp there, the party was visited by a snowstorm, which
covered the ground to a depth of 4 inches in the course of six hours.
This was succeeded by six days of dark, stormy weather, which entirely
interrupted all progress, and terminated by a rain, with a change to a
milder temperature, which cleared away the snow. During this untoward
event the parties made themselves as comfortable as practicable in their
tents, and were occupied in computing many of the astronomical and other
observations previously made.

On the 2d of November the weather became clear, and the necessary
astronomical observations were immediately commenced at Parks Hill.
From this elevated point the first station could be distinctly seen by
means of small heliotropes during the day and bright lights erected upon
it at night. Its direction, with that of several intermediate stations
due south of Parks Hill, was verified by a new series of transit
observations upon high and low stars, both north and south of the
zenith. By the same means the line was prolonged to the north.

In one week after commencing the observations at Parks Hill the weather
became again unfavorable. The sky was so constantly overcast as to
preclude all astronomical observations, and the atmosphere so thick as
to prevent a view to the north which would permit new stations to be
established with sufficient accuracy in that direction. Unwilling to
quit th