Could the waters of the sea be removed and North America viewed from a distance, in the manner we are enabled to examine the surface features of the moon through a powerful telescope, an observer would behold a great plateau, having the present well-known triangular shape of the continent, rising boldly between the Atlantic and the Pacific basins. The surface of the plateau would be rough, in comparison with the generally smooth contours of the adjacent troughs, but even the highest mountains would be less in elevation above its general surface than the crests of its bordering escarpments above the adjacent depressions. The mountain-peaks when illuminated by the sun would appear as points of light with long, tapering morning and evening shadows, and the east and west plateau-borders would be strongly drawn bands of light or shadow, according to the time of day, 6,000 or 8,000 miles in length. The Bermuda, Hawaiian, and other islands now rising above the surface of the deep sea would stand on its desiccated floor as isolated, gigantic mountains--"Bermuda mountain" with an elevation of 15,000 feet, and the Hawaiian group of peaks with a culminating point of light 30,000 feet above the surrounding plain. The bordering slopes of the "North American plateau" and its slightly bevelled margin forming the present continental shelf would be lacking in details, and appear as a vast, smooth, curving belt of light or shadow, in striking contrast to the roughened surface now above water. The North American continent is not exceptional in being partially submerged at the present time. Similar conditions occur about the margins of other continents which, as is well known, are fringed with broad submarine terraces built in part of their own _debris_. In fact, every large land mass on the earth under existing climatic conditions and present distribution of life, if it remained moderately stable for a sufficient length of time, would have a submarine shelf built about its borders. _Of what is the Continental Shelf Composed?_--The rocks forming the present land surface of North America extend seaward from the existing shores and constitute the basal portions of the continental shelf, thus suggesting that the submerged platform is due, in part at least, to shore erosion--the waves having eaten into the land so as to make a terrace. That this is not the true explanation, however, may be shown in several ways.