HELIGOLAND, or HELGOLAND, is a small group of islands belonging to Great Britain, and situated opposite the mouths of the Elbe and the Weser, and at the dis tance of nine German miles from each. The islands of Heligoland consist, 1st, of the island of Heligoland ; 2d, the Sandy Island, called the Downs; and 3d, of several reefs and rocks, of which that called the Monk is the most remarkable. The island of Heligoland is divided into the High Land or the Cliff, and the Low Land. It is said to be in a state of rapid destruction from the en croachments of the sea ; and it is reported among the in habitants, that during the last century, it has been redu ced from 11 miles in length to its present dimensions of 1 mile. The high land or cliff, according to the measures taken by Dr Heinemeyer, is 166 feet at its greatest, and 88 feet at its least height, and has a circumference of 4200 paces. It is ascended by a flight of 203 steps. The low land, which increases sensibly every year, is connected with the eastern part of the cliff by a rock about 500 paces long. The circumference of the low ground was 1400 paces in 1800. The circumference of the whole island, including the high and low ground, is 4600 paces. The Downs, or Sandy Island, is about two-fifths of the size of Heligo land; but its extent is constantly According to Dr Macculloch, IIeligoland consists of strata of indurated clay alternating with beds of gray limestone, forming an angle of 30° with the horizon, and dipping to the north-east. The clay is of a strong red colour, and contains much oxide of iron, and some car bonate of lime. The limestone is in some parts formed of various marine remains, and in others it is uniformly granular. Through both these are dispersed in various places deposits of copper ore in small quantities. These consist of carbonate of copper diffused through the earthy matter, and of crystallized masses of the same substance; and more rarely there are found lumps of red oxide, mixed with particles of gray ore and native copper. The beach is covered lyith various siliceous pebbles, contain ing grains of the same substance imbedded in them, to gether with variously coloured porphyries and hornstones.
On the shore are found belemnites, and other calcareous and flinty fossil remains ; and considerable quantities of pyrites, and carbonized and pyritaceous wood, are con tained in the clay strata.
. This island is said to have suffered great physical re volutions in the years 800, 1300, and 1500. The Downs, or the Sandy Island, was not only connected with the low ground of Heligoland, but even a part of the reefs was covered with earth. Other revolutions took place in 1649 and 1720. Before the first of these epochs, the low land of Heligoland contained the isle called the Downs; and even before 1720, there existed between the two islands a narrow isthmus, which was seldom covered with water, except during very extraordinary tides. Since 1720, the two islands have been separated by a strait called Waal, which is from 18 to 20 feet deep.
The soil which covers the rock is from 31 to 4 feet deep, and is rather fat than sandy. It produces annually about 300 tons of harley, and a little oats. The uplands afford good pasture for about 60 cows, and 400 or 500 sheep. in the northwest part of the island there are three ponds of rain water, called 8a/18k:den by the inhabitants. The water of the two springs in the low'ground is fit only for cattle, and is scarcely of use for washing. The prin cipal revenue of the island is derived from the fish which are caught. About 120,000 Lubeck mare of fish, amount ing to about 230,000 francs, are exported annually.
There are two good harbours in the island, which could be improved at a trifling expence. The northern harbour, the larger vessels of the islanders lie, varies in depth from 7 to 42 feet at half tide, and the southern har bour, which receives the chaloupes, has a depth of from 10 to 24 feet. To the east of the Downs is a road, which has 48 feet of water. The tides ordinarily rise 9 feet, but with a north-west wind they rise to a great height.