Most writers in the past have attributed the stone forts of the west of Ireland to the Firbolgs of the first century of our era, basing their conclusions on a bardic legend recited a thousand years after their invasion. But the forts are too numerous, and many of too vast proportions, for the stricken remnants of a race to have raised in their defence when driven to their last extremity on the wild shores of the Atlantic. The far-fetched theory, too, like many other such, that they were erected by sea-rovers to hold their spoils, is equally untenable for the same and other very apparent reasons. The absence of water-supplies within the forts, which has puzzled some, is paralleled in the British and other European forts, and was no doubt a precautionary measure to prevent the pollution of springs and wells. It is an indication, also, that the forts were not intended to stand a prolonged siege, a practice in warfare of a later time, but were raised as a protection against raiding and sudden assault. Their height above the sea was to give greater security, and their commanding sites, with due precaution in watching, prevented the dwellers being taken unawares. When life and property were unsafe, the desire for security, as well as social habit, gave rise to these works. The dwellers fortified their camps for themselves and their cattle, moving about freely in times of peace, and withdrawing to these strongholds in times of danger. They were as much a necessity in early days as the walls and bastions defending the towns in the Middle Ages. Their extraordinary number, out of all proportion compared to Scotland with its 1300, testify to the fact that the land was not a peaceful land long before the coming of the Dane. It is difficult in the present state of our knowledge even to approximate the date of their first introduction, as it is difficult, if not impossible, to assign a definite date to any archæological period in Ireland. The Irish forts are among the finest of a type of primitive defences extending across the continent of Europe from the Atlantic to the Black Sea and the Mediterranean shores of Greece. The construction of the walls in sections, and the passages and chambers, link the western forts through similar, though more perfect, features with the cyclopean walls of Tiryns, Mycenæ, and the Punic cities of North Africa. The cashels, the mounds, and the hill forts with their encircling ramparts have their counterpart in the middle latitudes of Europe, in the lands once dominated by the Celt, and which cover a period from the Bronze Age, at least, to the days of the Roman occupation. In Ireland their use ranges from prehistoric times down to the Middle Ages; and some were occupied for ordinary dwelling purposes down to modern times. CHAPTER VII. THE STONE AGE. FLINT ARROW-HEADS--STONE CELTS--AXE-HAMMERS.