Page:Encyclopædia Britannica, Ninth Edition, v. 12.djvu/635

 the end of the bays into the interior, the farms farthest inland being about 50 miles from the sea.

As the snow-line is at an altitude of from 2500 to 3000 feet, all the highest mountain-tops are cones covered with perpetual snow. Besides the ice-mountains already mentioned, there are several on the western part of the central highlands, such as Hofsjökull, Langjökull, Eiríksjökull, &c.; Snæfellsjökull, at the point of the peninsula separating the Faxaflói and Breiðifjörður, reaches the height of 4713 feet. All these mountains are snow-capped. Most parts of the island are studded with hills ranging in height from 2000 to 3000 feet. The tops are usually bare and rocky, but the slopes are to some extent covered with grass and heather.

Most of the mountains of Iceland have been volcanoes, and at least twenty-five of them have been active within the historical period of the island, that is, the last 1000 years. It was observed by Mackenzie that there are two volcanic formations in the island, one consisting of flat sheets of basalt, the other of more irregular hilly accumulations of trachyte, obsidian, ashes, and other volcanic masses. The former of these, there can be little doubt, is of Tertiary age—a part of the great Miocene volcanic plateaus, which on the one hand extend southwards through the Faroe Islands and the west of Scotland to the north of Ireland, and on the other stretch northwards and westwards far into Greenland. The other volcanic masses are of recent date. Iceland has thus been the theatre of volcanic activity at two widely separated periods, though we do not yet know whether during the interval the activity was wholly dormant. Of the existing volcanic mountains the best known is Hecla, from which eighteen eruptions have been recorded; the last took place in 1845-46. The intervals between the eruptions have varied greatly; sometimes it has remained quiet for six years only, at other times for seventy-two years. As with most other volcanoes, the height of this mountain varies with the eruptions. Thus before the eruption of 1845 its height was given on Gunlaugsson's map as 4951 feet, while Kjerulf measured the mountain in 1850, and found it to be only 4532 feet. The earliest historical eruption, that of 1104, is celebrated as the “sand-rain winter,” the second, in 1158, as the “great darkness,” from the quantity of ashes ejected. One feature of the Icelandic eruptions, not from Hecla only, but from other orifices in the island, has been the prodigious quantity of fine dust discharged and the great distance to which this material has been carried. Thus in the year 1766 a column of ashes rose out of the crater of Hecla to a height of 16,000 feet into the air. Volcanic dust from the Icelandic vents has frequently been borne by upper air currents so as to fall upon the Faroe Islands, and has even been carried in considerable quantities as far as Norway on the one side and the north of Scotland on the other. Next to Hecla, the Katla, or Kötlugjá, in Mýrdalsjökull may be mentioned; its last eruption (the thirteenth known) took place in 1860. The most tremendous volcanic outbreak in Iceland was that which took place in 1783 in or near the Skaptárjökull, on the north-west border of the Vatnajökull. Two principal lava streams flowed from it: one of them was 50 miles in length, from 12 to 15 miles in breadth, and 100 feet deep, and the other was 40 miles in length. It has been calculated that these two streams cover an area of 420 square miles. This eruption destroyed directly or indirectly one-sixth of the inhabitants of the whole island, or one-half of all the live stock. From nearly all the outliers of the Vatnajökull eruptions now and then take place. To the north of Vatnajökull a range of volcanic centres extends as far as Myvatn. The last outbreak here took place in 1875, when fine volcanic dust was discharged in great quantity, some of it being carried as far as Norway. The sea around the coasts of Iceland has

been frequently disturbed by volcanic outbreaks, especially off Cape Reykjanes.

On account of the same volcanic activity, hot springs are frequently met with throughout the island. The common name for them in Icelandic is “hverr” (cauldron). The chief of these hot springs is Geysir (Gusher). See .

The only mineral worked to any extent in Iceland is sulphur; the principal mines are those of Krísuvík and Mývatn. Of the Iceland spar used for polarizing optical instruments, only one mine has been worked, that of Helgustaðir in the east of the island. Limestone is found near Reykjavík, and has been worked a few years. Iron-ore is found in many parts of the island, but not in paying quantities, as suitable fuel is wanting. Aluminium occurs near Cape Reykjanes, but no attempt has been made to work the mine. Coal has also been found in one place, but has not been worked. There are considerable quantities of lignite, called in Icelandic surtarbrandur, in the north-west peninsula; some successful attempts have been made to use it as fuel, but it has not been worked to any extent. Peat is found, and is used as fuel, in most parts of the island.

Iceland is rich in streams and rivers, some of them carrying a large volume of water; as, however, the fall is steep in every case, they are not navigable even by small boats. The longest are Þjórsá, running southwards from the central highlands, and Skjálfandafljót and Jökulsá á Fjöllum in the north-east, running northward. The last-named river is 113 miles in length, the other two 108 miles each. Of other rivers may be mentioned the Hvítá, part of which is called Ölfusá, running nearly parallel with Þjórsá, Hvítá in Borgarfjörður, Blanda running into Húnaflói, Héraðsvötn in Skagafjörður, and Lagarfljót in the east. There are several rivers named Hvítá (white river), so called from their milky waters, caused by the glacial mixtures carried down from the highlands. The principal waterfalls are—Skógafoss and Seljalandsfoss, south of Eyafjallajökull, Godafoss in Skjalfandáfljót, and Dettifoss in Jökulsá á Fjöllum. Of the lakes Þingvallavatn, about 25 miles north-east of Reykjavík, and Mývatn in the north-east of Iceland are the largest. The former is 25 miles in circumference, and the latter 36 miles; its waters are studded with thirty-four small islands, affording breeding-places to a large number of water-fowl.

The climate of Iceland is not nearly so severe as might be supposed from the latitude. At Reykjavík the mean temperature of the year is 39° Fahr., of the summer 53° and of the winter 29° 18′, The temperature of Akureyri is 32° for the year, that of the summer 45° 5′ and the winter 20° 7′. There is therefore great difference between the north and the south of the island. Another difference may also be noticed; while the climate of the south is wet and variable, that of the north is dry and regular. The mean temperature of different years sometimes varies as much as 10°, and the mean temperature of the same month has been known to vary as much as 27°. One feature in the climate has been noticed by all travellers, that is, the clearness and purity of the atmosphere, rivalling that of Italy, mountains being seen distinctly at a distance of 100 miles. The rainfall is considerable in the south and the east of the island, and snow-storms and gales are frequent in winter. Thunderstorms occur mostly in winter.

No cereal is grown in Iceland, but in some places there is found a kind of wild oats (Arena arenaria), called in Icelandic “melur.” Potatoes, carrots, turnips, and several kinds of cabbage have lately been cultivated with considerable success. The grasses, wild and cultivated, are of the greatest importance to the inhabitants. The only trees found are the dwarf birch, rarely higher than 12 feet, and XII. — 78