Page:Transactions of the Geological Society, 1st series, vol. 1.djvu/26
Dr. Mac Culloch's Account of Guernsey,
conducing much to its picturesque appearance, and contributing to its fertility: in which, on a comparison with Alderney, it very much excels. It is well watered, and produces trees of tolerable growth and vigour; a circumstance denied to the former.
Although there are five landing places about the island, there is no harbour where ships can lie, and but one beach where small boats can be wintered. Such is the nature of the cliffs, that except at the Creux, where a tunnel is cut through the rock, there is hardly any entrance to the land, but by climbing. It is a very strong natural fortification, and might at a small expence be rendered impregnable.
The rocks which compose the shores, being of various and generally line forms, afford a variety of singularly grand and picturesque scenery.
Havre Gosselin, which is formed between the land and l'Isle des Marchands, is the nearest landing place to Guernsey. This is bounded by cliffs of trap formation, near two hundred feet in height, in many places very hard and compact, as is particularly the case where it is in contact with granite. The rock of which they are formed seems to have a N and S direction, consisting of indistinct strata, and dipping to the east under an angle of about 40°. These cliffs are divided by many large and deep fissures, out of which the materials have been washed, thus leaving large cavern. Some of these veins which I was able to examine, are filled with stones, ironshot, and in a state of decomposition. In some parts I observed dark siliceous iron stone; and in some, were mixtures of black mica and quartz, resembling micaceous schistus. Smaller intersections are formed of green, and red jaspers, and many coarse agates are found among them, consisting of similar materials, and mind with hornstones and quartz of different colours. Many veins are inaccessible, but the substances found on the beach which seem to