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The Cliffs of the Virgin Islands It is true that the cliffs of some of the small satellite islands, appear somewhat formidable when seen from a small boat near their base; and it is true also that in the abrasion of such cliffs a considerable fraction of the small islands has been consumed; hence, if the small islands alone were considered, abrasion might be assigned a considerable value in the production of the existing forms. Its relative insignificance will be better understood when the cliffs on one of the larger islands, like St. Thomas, where the cliffs are practically of the same height as on the small satellites, are viewed from a fair distance offshore, so that their relation to the whole island mass may be apprehended. The small time value and the recent date of their abrasion compared to the early beginning and long duration of valley erosion thus becomes manifest; hence St. Thomas reënforces the conclusion reached on other islands already described, that the headland cliffs were produced during relatively recent and short-lived efforts of abrasion, such as the Glacial epochs would have afforded. It also supports a conclusion which has already been implied in the accounts of other islands and which may be here more explicitly expressed: namely, that the fluctuations of ocean level during the Glacial period were much more rapid than the subsidence by which the maturely dissected island has been given its embayed shore line and during which the former protecting reefs were built up; for it was upon the headlands of the already dissected and partly submerged, reef-encircled island that the cliffs were cut when the time for abrasion arrived. Good opportunity for inspecting a number of the headland cliffs on St. Thomas by passing close along their shore in a small launch was given me by the courtesy of Captain Siems of the U. S. Coast and Geodetic Survey. Their height above sea level is of moderate measure, such as 20, 40, or 60 feet; hence they have not involved much spur-end shortening. They are not fronted by shallow rock platforms, as they should be if they had been abraded at present sea level. Instead, they plunge directly into blue water, and depths of 4, 5, and 6 fathoms were sounded within a boat's length of the face; yet even this depth is presumably less than that of the true cliff-base rock platform, which must now be more or less aggraded with waste fallen from the exposed part of the cliff face. I hesitate, however, to infer that the true platform depth is as much as 20 or 30 fathoms, as it should be according to the estimated depth of ocean lowering and platform abrasion adopted in Daly's exposition of the Glacial-control theory of coral reefs. If the platform really has any such depth around the islands, it must have been 40 or 50 fathoms deeper at its outer margin; and the much less depth of the existing bank would therefore demand a larger measure of Postglacial aggradation than seems reasonable. Home