Geoscience Reference
In-Depth Information
When making a catalogue of the position of the stars prior to the discovery of the planet
Uranus, he observed the planet 12 times, without recognizing its nature. In 1776 he added
a new constellation to the sky, Turdus Solitarius, the “Solitary Thrush,” but it fell from
favor and was rationalized away, its stars absorbed into adjacent constellations.
The expedition members began their visit to Sweden in Stockholm where they
were presented to the King of Sweden and gathered local knowledge from the
Swedish office of mapping. In June 1736 the party split into two, one group of those
more liable to sea-sickness traveling by land and the other by sea, to the estuary of
the River Tornea (or Torne or Tornio or Tornionjoki), 1135 km from Stockholm. At
the present day the River Tornea forms the natural boundary between Norway and
Russia in the north and Sweden and Finland in the south (Regional Library of
Lapland and the Pello Municipal Library 2006) and at the time of the expedition
the area was all part of Sweden. They arrived in the summer, “time enough to see
the Sun perform his course for several days together without setting, a sight that
strikes with wonder an inhabitant of the Temperate Zone” (Maupertuis 1738).
The astronomers measured a meridian arc between the church bell-tower in the
town of Tornio on a peninsula near the mouth of the river and the mountains north
of Kittis. These places were linked by the river, which flows due south along a
meridian arc. They traveled upstream, mounting the cataracts in the rough water
in Lapp boats of shallow draft and made of thin, deal planks flexible enough not
to be damaged by frequent collisions with submerged rocks but as a consequence
very unstable.
They had planned before setting out from France to make measurements from
islands along the river, but the islands proved to be very low lying and they could not
establish lines of sight between them over large enough distances. Therefore they
had to make forays, or “most painful marches,” inshore from the river and climb
mountains, “clambering up steep rocks” to get line of sight connections between the
surveying sites. At each mountain top site they built a “target” which also served as
a shelter for the surveying instrument. Each target was a hollow cone of pine trees
tilted together to touch at the tops and from a distance tapering to a point. The trees
were stripped of their bark to make them more visible, and the sighting telescope
was mounted inside the cone on its axis to make the measurement outwards from the
site. They used quadrants and sectors to measure the angles of the triangulation
network that had been made by the instrument maker Claude Langlois (
Fig. 22
).
The geodetic survey took two months in the summer of 1736. Even then, the
weather in the mountains was bitterly cold, much more so than in the valleys. In
one instance they had to camp on a mountain for ten days and wait for the atmos-
phere to clear; the fog lifted only when the wind was from the north. They were
also impeded by a forest fire that filled the air with a smoke haze and had to send
someone to distant targets to cover them with a white sheet to see them better. One
target was burnt down and they had to re-erect it. Fortunately they had had the
foresight to mark the positions of the targets with stones and stakes. Maupertuis
remarked on the “beautiful lakes” in the mountains that gave the countryside the
“air of an enchanted island in a romance.” He sourly added, “…anywhere but in
Lapland it would be a most delightful place.”
