De Maupertuis The degree measurements by de Maupertuis in the Tornionlaakso Valley 1736-1737
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The measuring instruments
The measurements
The measurement sites


The measurements

A quadrant was used for the measurements. The erecting of the signals, changes of the measuring points and measurements and their readjustments as such caused that most hills were visited 3 - 4 times. The erection of the signals started on the sixth of July and the measurements were finished on the sixth of September. By measuring the distance between two triangular measurement points, the base line, could be established and after that by geometrical calculations the length of the other sides of the triangle could be counted. Aavasaksa was chosen as the site for the base line, because:

Mount Avasaxa is situated in the best peopled and finest part of the river : its bed, above all, towards the south, for the space of four or five leagues, is extremely wide, and offered the most proper spot we could desire for an excellent base, whose extremities would be visible from Cuitaperi and Avasaxa. This base could not be measured at any other time than in winter over the ice ; but it suited to fix upon it, and erect signals at its extremities, to join it to the triangles, and to make the necessary observations before winter came on.(Outhier, Journal of a voyage to the north 1736-1737p. 284)

At Kittisvaara and Tornio the direction of the meridian in relationship with the triangles was measured. As the Delta star of the constellation Dragon crossed the meridian close enough to the zenith as well in Pello as in Tornio, two zenith measurements that were carried out by a sector as quickly sequenced as possible revealed the length of the meridian arch in degrees. In addition to the actual measurements adjustments had to be made because neither Kittisvaara nor Tornio lie exactly on the same meridian. The triangles were not situated on quite the same level in relationship to the ground level either.

We had chosen d of the Dragon as the most proper star for the observation of the sextant : it passed the meridian near enough to the zenith, at the most suitable hour, to be again observed at Torneo.
(Outhier, Journal of a voyage to the north 1736-1737p. 299)

The periods of oscillation resulting from the measurements on the gravity pendulum were compared to those carried out on the seconds pendulum.

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