The extremities of the valleys, where they approach the ocean, are the principal theatres of volcanic activity. At the northern end the best-known volcano is that of Hekla, which has attained a sinister repute from the terrific character of its eruptions. Of these six-and-twenty are recorded, the last having occurred in 1845–46. One lasted for six years, spreading devastation over a country which had formerly been the seat of a prosperous colony, burying the fields beneath a flood of lava, scoriæ, and ashes. During the eruption of September 2, 1845, to April 1846, three new craters were formed, from which columns of fire sprang to the height of 14,000 feet. The lava accumulated in formidable hills, and fragments of scoriæ and pumice-stone, weighing two hundredweight, were thrown to a distance of a league and a half; while the ice and snow which had lain on the mountain for centuries were liquefied, and poured down into the plains in devastating torrents. But the eruption of another of these terrible volcanoes, the Skaptá Jokul, which broke out on the 8th of May 1783, and lasted until August, was of a still more awful character. At that time the volcanic fire under Europe must have raged most violently, for a tremendous earthquake shattered a wide extent of Calabria in the same year, and a submarine volcano had flamed fiercely for many weeks in the ocean, thirty miles from the south-west cape of Iceland. Its fires ceased suddenly; a series of earthquakes shook the island; and then Skaptá broke forth into sudden and destructive activity. For months the sun was hidden by dense clouds of vapour, and clouds of volcanic dust were carried many hundreds of miles to sea, extending even to England and Holland. Sand and ashes, raised to an enormous height in the atmosphere, spread in all directions, and overwhelmed thousands of acres of fertile pasturage. The sulphurous exhalations blighted the grass of the field, and tainted the waters of river, lake, and sea, so that not only the herds and flocks perished, but the fish died in their poisoned element.