together, closer and higher, until there is a diminution of the pressure from below and they surge back, shattering themselves in the commotion and yet binding themselves into a single unit strong enough to resist the next onslaught of the tidal energy. Along the shores, where the solid compactness of beetling cliffs holds back the sweep of the tide, the ice piles itself in mountainous ridges and chains. Those of greater bulk, taking the ground, offer a resistance against which the lesser masses can only strain and grind; but away out in the unfathomable depths of the Polar Sea there is no chance of the ice ever grounding. It is always floating, and so always susceptible to the force of wind, tide, and current. Consequently it is always moving and feeling the pressure of the water below, of the grinding strain of the drift, and of the surface disturbances brought about by the constant displacement. Any one who has seen a pond in winter, when the ice round the edge is rotten and when a breeze blows across it, is aware how the loose sheet which covers the centre creaks and groans as it is driven against the bank. The edge is shivered into small flakes before the resistance can stop the forward movement, and then the sheet moves back against the breeze until once more the power of the wind controls it, and there is a renewed straining along the bank, the previously broken flakes either being forced up on to the bank, or else under, or over, the edge of the sheet. Pieces a yard square slowly rise up on end before the pressure and, falling back, shiver into fragments which scurry across the smooth surface of the sheet until they are arrested and become frozen to the main surface. Everywhere when the forward movement is on there is noise of creaking, groaning, and cracking, and everywhere on the ice sheet there is evidence of the force exerted.