2. The second case differs from the first in that the sediment washed down from the land is deposited about its borders. This results in the building up of a marginal platform, as shown in Figs. 39–41. As erosion goes on more sediment is washed down and deposited, partly on the narrow marginal shelf which has already been developed, and partly on its outer slope, as shown in the figures. The marginal flat is thus extended beyond the original shores of the island on the one hand, and toward its center on the other. As it develops, its inner portion, and indeed all except its outer edge (_ab_, Figs. 40 and 41), will be gradually built up above the level of the water. This marginal lowland is developed at a level as low as running water, _under the conditions then and there present_, can reduce the land. Such a surface may be said to be at _grade_, since running water neither wears it down nor builds it up. Its angle of slope is a function of (1) the volume of the water running over it, and (2) of the load which the water carries. [Illustration: +Figs.+ 39–41.—Diagrams to illustrate the effect of rain erosion on an island when all the eroded material is deposited about the shore. The black portions represent deposition. The dotted lines represent the original surface. The several diagrams represent successive stages in the process.] Since the marginal plain of the above illustration extends beyond the original shore of the island, the area of land is increased, though both its average elevation and its mass (above water) are reduced. In case destructive processes did not operate on the marginal graded plain the spreading and lowering suggested by Figs. 39 and 40 would go on until the central mass of the island was brought down to a gradient in harmony with that of the gently sloping border, as shown in Fig. 41. When this had been accomplished there would be a relatively large land area with low slopes (Fig. 41) in place of the smaller area with steeper ones (compare Figs. 39 and 40). The basal part of the larger island from the center to the original margin would be made up of the original material in its original position (unshaded part of Fig. 41). Its surface would be covered, least deeply near its center and most deeply near the original margin, with débris gradually shifted from higher levels, as shown in Fig. 41.