duration of the post-emergence or post-submergence stationary period, the estimation of which may now be considered in some detail. Time since Emergence.—The shore-line of an emerged and thence-forward stationary coastal plain may be locally built forward, or “prograded,” by deltas if its rivers are of large volume and well charged with detritus from an elevated backland; and sand reefs enclosing shallow or marshy lagoons may be cast up by the waves between the deltas, and may advance seaward as the delta-fronts advance. Conditions of this sort appear to prevail along the Madras border of India, and around the south-west side of Borneo, thus proving that these coasts have been somewhat changed from their simpler initial form; but the littoral conditions are still manifestly unfavourable to coral-reef formation. It is conceivable, however, that after a temporary supply of gravel and cobbles has been washed out by a flooded river to a certain part of the front of a delta that is for the most part composed of finer sediments the river may change its course, as rivers on deltas are prone to do. Then corals, attaching themselves to the larger cobbles, may spread sufficiently to form a small fringing reef, until a return of the river buries the corals. A buried reef of this kind will slant forward with the delta-front, and will lie conformably between the earlier and later foreest delta-beds. Such seems to have been the origin of a small elevated reef near Suva, Fiji: it lies on a local deposit of gravel, and both the gravel and the reef lie conformably in the slanting beds of volcanic mud, there known as “soapstone.” The extent of the littoral lowland that is prograded along the border of a coastal plain will give some idea of the time that has elapsed since the plain emerged. But such lowlands are not always developed; for, if large rivers are wanting, the shore-line of a coastal plain may be cut back or retrograded farther and farther by the sea, as long as no change of level takes place. The farther it is cut back, the higher will be the resulting bluffs along the coastal-plain margin. The height of the bluffs along the shore of a retrograded coastal plain will therefore give an indication of the time during which it has been attacked by the sea. A more important point is that, however far such a stationary coast may be retrograded, a beach of loose detritus, continued off shore by a sheet of finer sediments, will, according to accepted physiographic theory, always cloak the abraded platform along the base of the retreating bluffs. No reefs are therefore to be expected on such a coast. The Reef-free Coast of Madras.—It is important that the coasts of the coral seas should be examined with these principles in mind in order to test their correctness. As far as I have read, there is no published account of a strongly retrograded coast in the torrid seas that is still suffering abrasion in its original stand with respect to sea-level. It is interesting to note, however, that the high, hard-rock cliffs which, as described by Cushing, rise a short distance inland on the coast of Madras appear to have been cut back by the sea before the emergence of the present Madras coastal plain; hence the cliffs must, before the sub-recent movement of emergence by which a negative shift of the shore-line was caused, have exemplified a maturely retrograded, reef-free coast; and at the beginning of their abrasion the hard-rock land-mass must in all probability have been covered, near its shore-line at least, with the sediments of an ancient coastal plain of emergence, just as the emerged platform of marine abrasion which fronts the high cliffs is covered by a