The measuring instruments
The quadrant was the principal instrument used in measuring angles.
The expedition was equipped with two quadrants. Both instruments were
made by Langlois in Paris. The bigger quadrant was two feet (24 inches)
of size. Today it is housed in the observatory of Potsdam - Bablberg
in Germany. The quadrant has the following inscription that in rough
translation reads: '' Mr Maupertuis has in 1745 donated this instrument
with which measurements were made at the arctic circle on a commission
of a scientific academy to define the flattening of the earth''.
The first aiming device that was used to measure the angles from other
points was made of debarked wood. The later devices are described as
Instead of a single tree to serve as a signal, as I had done at Kukuma,
M. de Maupertuis constructed a pyramid of trees, stripped of their branches,
and placed one against the other. These trees, fastened together at
the top, and spreading towards the bottom, made at the same time a signal,
the point of which could be distinguished with nicety, an observatory,
in the middle of which was placed the instrument for observing the angles,
without any reduction at the centre. (Outhier, Journal of a voyage to
the north 1736-1737, p. 278)
To secure the site of the aiming device in case of eventual destruction
a direction to the nearest trees and stones was defined and a pole was
erected to mark the site.
Six measuring poles of exactly 30 feet each were cut of long spruce
logs. For this purpose an iron fathom measure (1,949 metres) and a model
measure where the fathom measure could be fitted in had been brought
from Paris. The measures had been checked in Paris at a temperature
of + 14 degrees. With the help of these instruments the expedition members
had measuring poles of 30 feet (9,745 meters) made to be used in the
measurement of the central line at Aavasaksa.
The Graham sector was used for astronomic measurements (in defining
the localisation of the end points in relationship to the same star).
The sector has the signature of Sisson (London) and it has a radius
of 12 feet (23,6 meters).