only alter endless zigzag wanderings, at places where they have become filled with snow and thereby passable. In summer again, when the snow has melted, the surface of the ice-wilderness has quite a different appearance. The snow has disappeared and the ground is now formed of a blue ice, which however is not clean, but everywhere rendered dirty by a grey argillaceous dust, carried to the surface of the glacier by wind and rain, probably from distant mountain heights. Among this clay, and even directly on the ice itself, there is a scanty covering of low vegetable organisms. The ice-deserts of the Polar lands are thus the habitat of a peculiar flora, which, insignificant as it appears to be, forms however
an important condition for the issue of the conflict which goes on here, year after year, century after century, between the sun and the ice. For the dark clay and the dark parts of plants absorb the warm rays of the sun better than the ice, and therefore powerfully promote its melting. They eat themselves down in perpendicular cylindrical holes thirty to sixty centimetres in depth, and from a few millimetres to a whole metre in diameter. The surface of the ice is thus destroyed and broken up.