Moreover, if we suppose that after a time the water again penetrates, and again comes into contact with rocks that have again become heated up, there will be another explosion, and yet others. Each of these explosions will push along the ejected streams of lava, step by step, till they reach the land, and even till they reach the mountains bordering the sea. The forces thus arising would cause upheavals, even if they did not cause earthquakes. Such forces might bend strata, contort the rocks, and cause "faults." But why, the reader may ask, do you suppose that all these explosions of lava are directed to the land? We do not suppose that they are. The lava may be forced away from the land. Then if that occurs a ridge may be upheaved, or possibly a submarine volcano. "At the Hawaii Islands on 25th February, 1877," writes Sir Archibald Geikie, "masses of pumice during a submarine volcanic explosion were ejected to the surface, one of which struck the bottom of the boat with considerable violence and then floated. At the same time, when we reflect to what a considerable extent the bottom of the great ocean basin is dotted over with volcanic cones, rising often solitary from profound depths, we can understand how large a proportion of the actual eruptions may take place under the sea. The foundations of these volcanic islands doubtless consist of submarine lavas and fragmentary materials, which in each case continue to accumulate to a height of two or three miles, till the pile reaches the surface of the water and appears above it. The immense abundance and wide diffusion of volcanic ash, pumice, etc., over the bottom of the Pacific and Atlantic oceans, even at distances remote from land, as has been made known by the voyage of the _Challenger_, may indicate the prevalence and persistence of submarine volcanic action." It is fairly clear, therefore, that the sea bottom is leaky, and that volcanoes which are a consequence of it are scattered freely over the deep ocean floor. In some places, of course, very few eruptions occur, either because the underlying rocks are less leaky or the sea is too shallow for pressure.