says, appears to have existed in the north and north-west, comprising Scandinavia, Finland, and the northwest of the British area, and to have extended thence through boreal and arctic latitudes into North America. Of the height and mass of this primeval land some idea may be formed by considering the enormous bulk of the material derived from its disintegration. In the Silurian formations of the British Islands alone there is a mass of rock, worn from the land, which would form a mountain-chain extending from Marseilles to the North Cape (1800 miles), with a mean breadth of over thirty-three miles, and an average height of 16,000 feet.