[Illustration: _Flint Arrow-heads and Knives._] Flint is not a common stone in the Orkney Islands. It is found in occasional lumps and pebbles among the clay which has been carried from other places by the glaciers and icebergs of the Ice Age. Flint is common in the southern parts of Great Britain, however, and the arrows and knives found in our islands may have been brought from the south, or the art of making them may have been learned from tribes among whom flint was a more common material. This kind of stone, the fine steel of the Stone Age, was used for small implements over a wide area of the world. [Illustration: _Stone Hammers and Axes._] Orkney must have had a large population in those early days. The number of ancient graves which have been found seems to indicate this, especially if we suppose that most of those graves with their heaped-up mounds are the resting-places of chiefs and great men rather than of the common people. The graves which remain are of varied types, from the simple cist of upright stones roofed with horizontal slabs and covered with earth, to the large mound with its carefully built chambers. The variety of the objects found in those graves, from the rudest flint and bone implements to those which are carefully finished, and finally to objects made of metal, shows that the burials belong to different periods. They tell us of long ages of increasing though now forgotten civilization. Some of the mounds, indeed, show by their contents that they cover the remains, not of the original and unknown inhabitants, but of the Norse conquerors, and thus really belong to the period whose history has come down to us in writing. But in the very mound where the Norse warrior was laid to rest, there are sometimes also found the relics of burials of a much ruder age. Such mingling of the materials of our unwritten history makes the story which they tell a very difficult one to read. There are few remains in our islands more striking than the chambered mounds, or Picts’ houses, as they are called. The most complete and probably the most recent of them is that known as Maeshowe. They consist of a mound of earth heaped over a rude building, sometimes of one apartment, but frequently of several, the entrance being a long, low, narrow passage, through which it is necessary to stoop or crawl in order to gain an entrance. Possibly those Picts’ houses were built at first as houses to dwell in, though later used as tombs. It is not uncommon to-day to find buildings used for burial which were designed for other purposes. If ever our race and all its records were to vanish as completely as the primitive inhabitants of the Orkney Islands have done, we can imagine some future explorer of the ruins of St. Magnus Cathedral writing a learned treatise to prove that the largest building in our islands was erected as a burial-place for our dead.