a volcano of Iceland, and one of the most furious in the world, situated in the southern part of the island. See ICELAND.

It was visited in the year 1772 by Dr Van Troil, a Swedish gentleman, along with Mr (now Sir Joseph) Banks, Dr Solander, and Dr James Lind of Edinburgh. On their first landing they found a tract of land 60 or 70 miles in extent entirely ruined by lava, which appeared to have been in the highest state of liquefaction. Having undertaken a journey to the top of the mountain, they travelled 300 or 360 English miles over an uninterrupted tract of lava; and had at length the pleasure of being the first who had arrived at the summit of the mountain.

Hecla, according to the accounts of these gentlemen, is situated in the southern part of the island, about four miles from the sea-coast, and is divided into three parts at the top, the middle point being the highest; and, according to an exact observation with Ramdén's barometer, is 5000 feet above the level of the sea. They were obliged to quit their horses at the first opening from which the fire had burnt. They describe this as a place with lofty glazed walls and high glazed cliffs, unlike any thing which they had ever seen before.

A little higher up they found a large quantity of grit and stones; and still farther on another opening, which, though not deep, descended lower than that of the highest point. Here they imagined they plainly discerned the effects of boiling water; and not far from thence the mountain began to be covered with snow, excepting some spots which were bare. The reason of this difference they soon perceived to be the hot vapour ascending from the mountain. As they ascended higher they found these spots become larger; and about 200 yards below the summit, a hole about a yard and a half in diameter was observed, from whence issued so hot a stream, that they could not measure the degree of heat with the thermometer. The cold now began to be very intense; Fahrenheit's thermometer, which, at the foot of the mountain was at 54, now fell to 24; the wind also became so violent, that they were sometimes obliged to lie down for fear of being blown down the most dreadful precipices. On the very summit they experienced at the same time a high degree of heat and cold; for, in the air, Fahrenheit's thermometer stood constantly at 24, but when set on the ground, rose to 153: the barometer stood at 22.247. Though they were very much inclined to remain here for some time, it could by no means be done with safety; for which reason they were obliged to descend very quickly.

The mountain seems to be made up, not of lava, but of sand, grit, and ashes; which are thrown up with the stones partly discoloured, and partly melted by the fire. Several sorts of pumice stones were found on it, among which was one with some sulphur. Sometimes the pumice was so much burnt, that it was as light as tow. Its form and colour was sometimes very fine, but at the same time so soft, that it was difficult to remove it from one place to another. The common lava was found both in large pieces and small bits; as likewise a quantity of black jasper burned at the extremities, and resembling trees and branches. Some flate of a strong red colour was observed among the stones thrown out by the volcano. In one place the lava had taken the form of chimney-stacks half broken down.—As they descended the mountain they observed three openings. In one, every thing looked as red as brick; from another, the lava had flowed in a stream about 50 yards broad, and after proceeding for some way, had divided into three large branches. Further on they perceived an opening, at the bottom of which was a mount in form of a fugar-loaf, in throwing up of which the fire appeared to have exhausted itself.

We have already observed, that our travellers were the first who ascended to the top of this mountain. The reason that no one before them had ever done so was partly founded in superstition, and partly the steepness and difficulty of the ascent, which was greatly facilitated by an eruption in 1766. Most kinds of lava found in other volcanic countries are to be met with about Hecla, or other Iceland volcanoes; as the gray, dark perforated kind, similar to the Derbyshire loadstone; the Iceland agate, pumex vitreus, both the niger and viridis. Some have conjectured this to be the lapis obsidianus of the ancients, which they formed into statues.

The lava is seldom found near the openings whence the eruptions proceed, but rather loofe grit and ashes; and indeed the greater part of the Icelandic mountains consist of this matter; which, when it is grown cold, generally takes an arched form. The upper crust frequently grows hard and solid, whilst the melted matter beneath it continues liquid. This forms great cavities, whose walls, bed, and roof, are of lava, and where great quantities of talcactite lava are found. There are a vast number of these caves in the island, some of which are very large, and are made use of by the inhabitants for sheltering their cattle. The largest in the island is 5934 feet long, and from 50 to 54 in breadth, and between 34 and 36 in height.—There are some prodigious clefts left by the eruptions, the largest of which is called Almeneggaa, near the water of Thingalla, in the south-western part of the island. It is 105 feet broad and very long. The direction of the chasm itself is from north to south. Its western wall, from which the other has been perpendicularly divided, is 107 feet fix inches in height, and consists of many strata, of about 10 inches each in height, of lava grown cold at different times. The eastern wall is only 45 feet 4 inches in height, and that part of it which is directly opposite to the highest part of the other side is no more than 36 feet 5 inches high.