252 THORODDSEN 



calcium sulphate (gypsum) is very common in the soil. The 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 the large rivers, 

 it must, in some places, be very considerable. In the districts where 

 liparite is the main rock, the soil has not yet been investigated, 

 but it must vary somewhat, on account of the varying composition 

 of the rock, which contains much larger amounts of silica (65- 

 78 %>), potash (24 %), and soda (36 /o) than the 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 fine soil 

 from dry grasslands the main mass consisted of silica (37 48 /o), 

 alumina and peroxide of iron (38 50/o), while lime, magnesia, 

 alkalies, present as silicates and other compounds, were found in 

 quantities of from 7 to 14 /o. The amount of carbonate of lime 

 Avas but small, and varied from 0.5 to 1.7 /o; in home-fields most 

 frequently 1.5 1.7 %. On the other hand, the amount of phosphoric 

 acid was larger (0.3 0.4 /o) 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 /o 

 to as much as 24 /o. 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 from 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; 



L Analyses of Icelandic soil are found in P. Feilherg: Bemaerkninger oni 

 Jordbund og Klima paa Island (Tidsskrift for Landekonomi. 1881) and by A. Tor- 

 fason in Bunadarrit, Reykjavik, XX (1906), pp. 173184; XXIII (1909), pp. ,">2 54. 

 Also, in tbe recently published work by M. Gruner: Die Bodenkultur Islands, 

 Berlin, 1912. 



