Where have the stones come from? One school of writers ventures to suggest Kildare in Ireland. Others suggest Wales, Cornwall, Dartmoor, Shropshire, or Cumberland, where similar rocks are to be found, though perhaps not absolutely identical in character. Yet another theory advanced is that the Foreign Stones were transported to the plain as boulders of the "glacial drift." It has even been stated that the gravels of the district contain small pebbles composed of rock similar to these mysterious Foreign Stones. The statement has indeed been made, but as yet no Wiltshire geologist has produced one of these pebbles of which so much is written, and so little seen. These Glacial Drift theorists, further account for the absence of these foreign stones elsewhere than at Stonehenge, by yet another theory, that they, like most of the Sarsens, have all been used up for millstones, gateposts, and road metal. There are many millstones and gateposts in Wiltshire, but where is there one which corresponds in any way to the upright Foreign Stones at Stonehenge? The production of pebbles from the gravels of Wilts, or of a specimen gatepost or millstone would at once settle this question. Unhappily this tangible evidence is wanting, so, alluring as the Glacial Drift theory may appear, it must reluctantly be set aside for want of convincing evidence. Finally, there seems every reason to believe that the small upright stones are "naturalised aliens" from abroad, and that is why they have been described at the commencement of this section as "Foreign Stones." It must not be taken for granted that the small upright stones at present standing represent all the foreign rocks employed. Probably they are merely the hardest and most durable of those used in the original structure, the softer and more friable examples having disappeared entirely, owing to the action of the weather, and possibly also to the assaults of the unchecked relic-monger, who until recent years could with his hammer collect _souvenirs_ with impunity. In this connection, there is a story afoot that a hammer was kept upon the mantelpiece of a well-known hotel in Salisbury, which was reserved for the use of those intending to see Stonehenge, who might be wishful to bring back some convincing evidence of their visit. In all probability these foreign stones originally numbered forty-five. To-day there are but thirty. A complete lithology of the stones made by the late Professor J.W. Judd, in 1901, reveals the following rocks as comprising those used in the construction of Stonehenge. 1. _Sarsens._--Coarse and fine-grained Sandstone similar to the Woolwich, Reading, or Bagshot beds. This stone is used for the Trilithons, Hele Stone, a recumbent stone known as the "Slaughtering Stone," and two small stones set north-west and south-east of the circle. It is of local origin. 2. _Ophitic Diabase._--(Some porphyritic.)