‘Rising from the middle of the Irish Sea, within sight of each of the three Kingdoms, with a history and associations so distinct, yet so intimately linked with those of the rest of Britain, this interesting Island presents in its geological structure features which connect it alike with England, Scotland, and Ireland, while at the same time it retains a marked individuality in regard to some of the rocks that form its framework.’—Sir Archibald Geikie.
The prehistory no less than the geology of the Isle of Man is of absorbing interest from its geographical position in relation to the larger units of the British Isles. The island is placed (fig. 1) at an equal distance (31 miles) between the coasts of Ireland and of Cumberland; its northern tip, the Point of Ayre, reaches to within 16 miles of Wigtonshire, and Anglesey lies 45 miles to the south of Langness Point. An observer on Snaefell (2034 feet) can view England, Scotland, Ireland and Wales in one sweep. Since the first settlement of the island, cultural and ethnic influences have approached from all directions, but its size (227 sq. miles) and the distance of sea which isolates it from the coasts of the mainlands have been sufficient to ensure vigorous local developments. The interaction of British and Irish influences and the occasional insular developments are the chief features of the prehistory of the island.
Apart from a triangle of flat ground to the north, broken only by the Bride Hills (200–300 feet), and so far as its drift deposits are concerned, relatively recent in origin, the island consists almost entirely of slate diversified by local intrusions of igneous rocks (granite and diabase), by the sandstone of the Peel area, and by the carboniferous limestone of the Castletown district in the south. Most of the area of older rocks lies above the 400 foot contour and quite large areas are more than 1000 feet above sea level. The mountainous mass of the island, divided by the valley between Douglas and Peel, remained almost uninhabited throughout prehistoric and historic times.