The Wiltshire of Scotland, in so far as the mere number of sepulchral mounds, along with monolithic groups and other aboriginal structures, can constitute this distinction, is the mainland of Orkney, with one or two of the neighbouring isles. Few of their contents, however, have proved of the same valuable character as those which have been discovered not only in Aberdeenshire, Fifeshire, and some of the southern Lowland counties, but also in the Western Isles. We are therefore led to infer that the population of Orkney has been little more distinguished for wealth, or great advancement in the arts, during its earlier history than in more recent times. Abundant evidence, however, testifies to the occupation of these islands by a human population at a very remote era, and no Scottish locality ever furnished a greater variety of interesting relics of the primeval period. In the single parish of Sandwick, near Stromness, upwards of an hundred tumuli of different sizes have been observed, many of which have been recently opened, and their contents described. In the parish of Orphir, in like manner, considerable research has been made into the character and contents of these ancient memorials; while throughout nearly the whole of the neighbouring islands, the mosses and moors which have escaped the obliterating inroads of the ploughshare, are covered with similar monumental heaps. It is not to be doubted that such relics of ancient population were once no less common throughout the whole mainland of Scotland, and especially in the fertile districts of the low country, where the earliest traces of a numerous population may reasonably be sought for. A sufficient number still remain in Fife and the Lothians, as well as in the southern counties, to afford means of comparison with other localities; while numerous discoveries of cists, urns, and ancient implements, leave no room to doubt that the same race once occupied the whole island, and practised similar arts and rites in the long cultivated districts of the low country, as in the remotest of the northern or western isles. It is not improbable that extended observation may justify a more minute classification of the primitive sepulchral monuments of Scotland than has been attempted above, and may establish a relative chronological arrangement of them on a satisfactory basis. With our present imperfect knowledge, any theoretic system would only embarrass future inquiry. But meanwhile it may assist in forming a basis for further operations, to note the following attempts at systematic arrangement from such data as are available.