Page:Prehistoric Britain.djvu/232

224 can now reveal their true history. No one has done more to clear up this point than the late General Pitt-Rivers by his excavations on Cranbourne Chase. This indefatigable explorer has shown that the Bronze Age camps were approximately rectangular—a feature which was formerly supposed to be peculiar to Roman camps. The relics collected in the stratified silt, which had, in the course of time, partially filled the surrounding ditches, furnished valuable data for establishing a chronological sequence in the occupancy of the camps. In this way he was able to classify and differentiate them according as they belonged to the Stone, Bronze, Late Celtic, Roman or post-Roman Ages.

The variety of forts known as "Vitrified Forts" has gathered around it an extraordinary amount of literature, chiefly of a controversial character. The real problem at issue is to account for the vitrifaction which to a greater or less extent is, or rather was, to be seen on the surrounding walls of some fifty stone-built forts scattered throughout the northern and south-western districts of Scotland, covering a broad band stretching from the shores of the Moray Firth to the counties of Argyll and Wigtown. I have satisfied myself, from a practical examination of the more important examples in Scotland, that the vitrifaction was effected by the external application of fire after the wall had been constructed, and that the sole object