But the impetus given to this branch of archæological exploration throughout Europe was more directly due to the discovery of dwellings similar in character in the lakes of Switzerland. In 1829, piles were discovered at Ober Meilen, on Lake Zurich; but it was not until the very dry and cold winter of 1853–4, that the inhabitants, in raising silt from the shallows of the lake to reclaim the higher portions of the shore, laid bare the piles of ancient lacustrine dwellings, and discovered a large quantity of stone and flint weapons, utensils, broken pottery, dug-out canoes, bones of wild animals, one human skull, and portions of several skeletons. On a careful examination, Dr. Keller was of opinion that the piles formed the foundation of a platform raised above the surface of the water upon which the huts were built, and that the place had been destroyed by fire after it had existed for a long period as the site of human habitation. Many similar discoveries in other lakes rapidly followed; and over 200 of these sites are now known in Switzerland. Their area of distribution has been found to extend throughout France, Germany, Austria, South Europe, and Asia Minor. The plan of the pile-buildings (_Pfhalbauten_), it will be seen, differed from the fascine method of construction generally practised in the erection of the British lake-dwellings. In Ireland, however, clusters of crannogs sometimes occur--as in Lough Eyes, County Fermanagh--and were, as is evident from existing remains, connected together by submerged causeways, or by approaches raised high and dry on piles. ‘A third method,’ says Dr. Munro, ‘was to construct, in close proximity to each other, a series of rectangular basements of wood, each basement having its sides formed by horizontal beams lying one above the other, and overlapping at the four corners, like the logs in a Swiss châlet. These compartments measured only a few yards in diameter. Their lowest beams rested on the bed of the lake; and when the requisite height above the water was attained, the usual platform was laid across, and the cellular spaces underneath became covered over.... This plan appears to have been adopted chiefly by the founders of the sporadic dwellings of the Iron Age.’[114] The population inhabiting the Swiss lake-villages must have been at one time very great. The settlements were on an extensive scale; and it has been estimated that from 40,000 to 50,000 piles were used in a station of the Stone Age period at Wangen, in Lake Constance, while some still larger required little short of 100,000. These lacustrine settlements were especially exposed to the danger of fire; but, as Dr. Munro points out, this ‘was the most fortunate event from an archæological point of view that could have happened.’ In the hurry of escape, little would be carried away; and perishable articles slightly charred were better able to resist the destructive agency of water.