Greinar (Vísindafélag Íslendinga) - 01.01.1951, Side 43

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bæjarklaustur, a distance of about 170 km. At four points
the measurements were extended right down to the coast.
The aim of this trip was especially to study gravity condi-
tions near the coast.
On the way back, we measured along the road from
Grímsnes across Þingvellir to Reykjavik.
The measurements were, as before, carried out by M.
Munck.
On this trip we used yellow paint to mark the points,
but because of constant rain, many of the numbers were
badly damaged or quite destroyed. In spite of this the
points should on the whole be recognizeable.
In this connection also, it should be remarked that our
plan was not to depend on a special nivellement. As the
points were mostly at a low altitude, below 100 m,, and
as we did not lay any stress on obtaining the Bouguer
anomalies with an accuracy of more than 0.5 mgals., we
decided that the accuracy of the heights on the topogra-
phial map (1 m.) was quite sufficient for our purpose.
Accordingly, we nearly always selected the stations at
such points where the elevation could be read safely from
the map, at rivers ,lakes, etc.
For the points between Reykjavik and Selfoss, the re-
duction is given in tenths of milligals, but for the other
points it is given in milligals only.
At the end of the week, M. Munck left for Paris, but
he left the gravimeter in Reykjavik in the charge of
M. Joset, who intended to stay here for another week.
We had now obtained a general picture of gravity in
southern Iceland, and this indicated that it must be im-
portant to proceed toward the center of the country. Conse-
quently, two journeys were made, one to Hveravellir
(between Hofsjökull and Langjökull), and the other
through the regions Holt and Land to the river Tungnaá.
These measurements were carried out by M. Joset.
Each trip began at the station Skólavarda in Reykjavik
and was closed there, and the differences in readings were
0.2 mgal. or less. Beyond this, a number of intermediate