A still more remarkable class of monumental stones remain to be described, including the singular sculptured pillars, peculiar, it is believed, to Scotland. But we have already trespassed on the relics of later eras, and these necessarily belong to a period long posterior to that when the rude aboriginal Caledonian possessed no other tools than the stone hammer and the flint chisel or arrow-head, with which to grave the memorial of his fame and the annals of his race. In the investigations of the archæologist, even though devoted, as this inquiry is, to the examination of ancient memorials within an extremely circumscribed area, he frequently finds that he is dealing with the evidences of certain phases of progressive civilisation in the history of the race, rather than with mere national peculiarities. The farther research is pursued this becomes the more apparent, and we learn, without much surprise, from the recent invaluable researches in the valley of the Mississippi,[129] that the ancient tumuli of the American continent are found to contain, amid many relics peculiar to the new world, stone celts and hammers, flint and bone arrow and lance heads, and other primitive weapons and implements so precisely resembling those disinterred from the early British barrows, that the most experienced eye could hardly tell the one from the other. To conclude from this that we have found evidence of an affinity of race, or of mutual intercourse between the rude aborigines of Britain and America in that mysterious period of the long forgotten past, however plausible it might seem at first sight, would be to adopt a theory which the investigation of the arts of modern races, such as the natives of Polynesia, must at once dispel. The same correspondence of primitive weapons is found in the north of Europe, in the steppes of Asia, in the ancient tumuli near the Black Sea, and even mingling with the evidences of earliest civilisation on the banks of the Tigris and the Nile. We must look, therefore, for the means of accounting for such remarkable correspondence of primitive tools, to some cause operating naturally at a certain stage of development in the human mind. It is the first manifestation of man's intelligent instincts as a tool-using animal, and furnishes a singular evidence of the instinctive faculties which belong to him as well as to the lower animals, though few and uncertain traces of these remain distinguishable where civilisation has fostered the nobler faculty of reason, and brought it into healthy and vigorous play.