The Botany of Iceland - 01.12.1914, Qupperneq 88

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THORODDSKN
The drií't-ice also earries to the coast oí’ Iceland fragments of rock
which are not found in Iceland (gneiss, granite, talc-slate, mica-
slate, etc.), and also gravel, clay and earth from other Arctic coun-
tries. Moreover, the warrn water of the Gulf Stream sometimes carries
drift-material with it from southern parts, e. g. mahogany, sugar-
cane, “nuts” of Entada Gigalobinm, Mncnna nrens, Guilandina Bon-
dncella, etc.
The weather of the North Atlantic Ocean depends upon the
winds, which also exercise a great iníluence upon the currents
around Iceland. The mean atmospheric pressure in the North At-
Fig. 20. Seeds of Enlada Gigalobium (1), Mitcuna urens (2), and Guilandina lionducella (3).
lantic is generally lowest to the south-west of Iceland but there is,
in addition, another centre of low barometric pressure north-east
of Iceland; on the whole, the direction of the winds over Iceland
is determined by this. In West and North Iceland the majority of
the winds blow from SE., E. and NE., while on the east coast
winds from the NE. and NW. are nearly equally numerous (20 %
and 17 % relatively) because here both the above-mentioned centres
of low atmospheric pressure try to prevail. This is true of the
average condition only, because in reality the wind-conditions from
day to day are very variable, as the ocean here is constantly visited
hy moving centres of depression. The barometer in Iceland is subject to
very great changes. In Reykjavík the barometer, during a period of
28 years, has oscillated between 789 mm. and 697 mm.; at Stykkis-
holm, during one of 33 years, between 789 mm. and 700.3 mm.; in
tlie Vestmannaeyjar during a period of 29 years, from 789 mm. to