Page:Early Man in Britain and His Place in the Tertiary Period.djvu/158

130 of the temperature after the forest-bed ceased to flourish. In No. 3 of the accompanying section, Mr. Nathorst, an eminent Swedish botanist, remarked in 1872 not only that the plants of the forest-bed became very much dwarfed in size, but that two new forms appear, now only found in severe climates; the polar willow (Salix polaris), now living within the Arctic circle, and a moss (Hypnum turgescens) common to the Arctic regions and

the summits of lofty mountains. The fluvio-marine sands and clays imply also a change of level, by which the trees of the forest were brought within the reach of the waves of the sea. Above them is the boulder clay, No. 4, containing large blocks of granite and other igneous rocks, which have been transported by ice possibly from Scandinavia. This stratum corresponds with the older boulder clay of Messrs. Harmer and Searles Wood.