The Botany of Iceland - 01.12.1914, Side 68

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252 THORODDSEN
calciurn sulphate (gypsum) is very common in the soil. Tlie Icelandic
basalts have not been investigated with regard to the amount of
apatite contained in them, but judging from the abundance of phos-
phoric acid which often occurs in the waters of tlie large rivers,
it must, in some places, be very considerable. In the districts where
liparite is the main rock, the soil has not jret been investigated,
but it must vary somewhat, on account of the varying composition
of the rock, which contains much Iarger amounts of silica (65—
78 %), potasli (2—4 %), and soda (3—6 %) than tlie basalts. For
the rest, the Icelandic liparites show evidence of their connection
with the basalt-area in which they occur, by the fact that almost
all of them are soda-liparites.
From Iceland there are as yet only a few soil-analyses to hand,
and from a few districts only.1 In calcined samples of fme soil
from dry grasslands the main mass consisted of silica (37—48 %),
alumina and peroxide of iron (38—50 %), while lime, magnesia,
alkalies, present as silicates and other compounds, were found in
quantities of from 7 to 14 %. The amount of carbonate of lime
was but small, and varied from 0.5 to 1.7 %; in home-fields most
frequently 1.5—1.7 %. On tlie other hand, the amount of phosphoric
acid was larger (0.3—0.4 %) than in ordinary Danish soil. The soil
samples were rich in humus and contained an unusually large
amount of nitrogen considering the amount of humus — from 7 %
to as much as 24 %. The amount of humus and also of iron com-
pounds is larger than in ordinary Danish soil. Under unfavourable
conditions of humidity the abundance of the organic substance found
in the soil constitutes a danger, on account of the formation of pro-
toxide of iron; and climatic conditions make the chemical changes in
the materials of the Icelandic soil difficult and slow in wet tracts.
The amount of the inorganic substances in the sand-samples gives a
correct idea of the chemical composition of the solid basaltic rock.
Some analyses have been made of Icelandic plants. Firstly, of
Icelandic hay, both hay í'rom home-fields (tun; see Fig. 17) and
hay from dry and from wet meadows. The analyses show that
the Icelandic hay resembles mountain hay from the Alps. It con-
tains a larger amount of fat than does the Danish hay; less cellulose;
1 Analyses of Icelandic soil are found in P. Feilberg: Bemærkninger om
Jordbund og Klima paa Island (Tidsskrift for Landokonomi, 1881) and bjT A. Tor-
fason in Búnaðarrit, Reykjavík, XX (1906), pp. 173—184; XXIII (1909), pp. 52—54.
Also, in the recently published work by M. Gruner: Die Bodenkultur Islands,
Berlin, 1912.
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