Bronze-Age Goidels or Gaels with the Celtae of Cæsar's Gallia Celtica, and his Iron-Age Brythons of England with the Belgae of Cæsar's Gallia Belgica. He goes still farther with this process of equation. Finding that the consonant Q, where it occurs in the most ancient forms of the Irish language, is replaced by P in the corresponding forms of the British or ancient Welsh language, he divides the Celts into two linguistic groups which he labels the Q-Celts and the P-Celts, and this division he makes to correspond to the other classification into Celtae and Belgae. In this way, he produces a most interesting and symmetrical set of equations showing the successive stages of population-change in Britain.

First, there are the people of the Early Stone Age, not named.

Secondly, the people of the Later Stone Age, Iberians.

Thirdly, the people of the Bronze Age, Goidels or Gaels, or Celtae, or Q-Celts.

Fourthly, the people of the Iron Age, Brythons or Britons, or Belgae, or P-Celts.

For the present, let us pass away from the Iberians, and consider the theory as it concerns the Celtic migrations to Britain and Ireland. The earliest known habitat of the Celts is the region to the north of the Alps. The earliest definitely known migration of the Celts is their southward movement into Northern Italy. For this migration no earlier date than 600 B.C. is assigned.

The chief authority on the Bronze Age in Ireland belongs to the late Mr. George Coffey. In his book on the subject, "The Bronze Age in Ireland," he hesitates to date the close of the Stone Age and the introduction of the Copper Period as far back as 2500 B.C., which is the approximate date estimated by Montelius. He puts the close of the Copper Period between 2000 and 1800 B.C. and the first period of the true Bronze Age between 1800 and 1500 B.C. Now, according to the theory prevalent in Britain, the first Celtic invaders introduced the Bronze Age, and these were the Gaels or Goidels. If we accept this view and combine it with the best archæological authority, we shall conclude that the Celts reached Ireland at least 1,200 years before they are known to have entered Italy—that they pushed out to a distant island in the ocean more than a millennium before they occupied the fertile and attractive plains which lay on their very borders.