That's no sign they weren't near a sea border at some time. Let me just ask you. Suppose you found that most of the great mountain chains are on the borders of seas, and suppose you had figured out the reasons I have just been giving, then what would you do if you found a few mountains far back from the sea? You would probably try to find how they got moved back, wouldn't you? That's just what _other_ men of science did. A study of the rocks of the mountains themselves and other things bearing on the question goes to show that since the mountains were made the sea might have retired from regions where it had previously advanced, as it did in the case of the Mississippi Valley, or the land may have risen between these mountains and the sea. Moreover, the down wash from the mountains themselves sometimes builds wide lands, which, as they extend and shut back the sea, leave the mountains farther and farther away. Much of the land extending east from the base of the Rocky Mountains was made in this way. The Mississippi Valley was for ages, you know (page 10) the Mediterranean Sea of North America, lying in the downward fold of our continent between the Rocky Mountains and the Appalachians. [Illustration: _From the painting by David James_ THE WAVE] WHY SEA WAVES RISE TO GREET THE MOUNTAINS One of the strangest, most poetic phases of the relation between the great blue mountains and the great blue sea is that waves, as they approach the shores of continents bordered by mountain ranges, rise higher and higher; and the higher the mountains, the higher rise the waves. These waves are not driven by wind or tide but seem drawn forward by some strange power. This power, however, is no stranger than the one that makes us fall and bump our noses when we stub our toes--the power of gravitation, according to which all masses attract each other. It is the mass in the mountains that exerts a pull on the waves; and the greater the mountains the greater the pull, of course. In the Indian Ocean, for example, around the head of the Arabian Sea, the waves rise far above sea level, largely because there is beyond them, on the land, one of the greatest mountain masses in the world. Wouldn't it give you a queer feeling if you were, say, a sailor, and for the first time saw waves act like that? Uncanny, almost, isn't it? But do the mountains remember their old parent of the white flowing rocks and beard, Father Neptune? They act as if they did; particularly in the way in which they come to imitate, in time, the shape of the waves of the sea. Ruskin,[21] speaking to artists about drawing mountains, says: "Good and intelligent mountain drawing recognizes a great harmony among the summits and their tendency to throw themselves into waves, closely resembling those of the sea itself; sometimes in free tossing toward the sky, but more frequently in the form of breakers, concave and steep on one side, convex and less steep on the other."