Along the Coastal plain reduction to baselevel was followed by depression and deposition of Lafayette gravels; elevation followed and erosion of minor baselevels; second depression followed and deposition of Columbia gravels; again comes elevation and excavation of narrow valleys; then depression and deposition of low-level Columbia; last, elevation and channeling, which is proceeding at present. Along the Catoctin Belt denudation to baselevel was followed by depression and deposition of gravels; elevation followed and erosion of minor baselevels among the softer rocks; second depression followed, with possible gravel deposits; elevation came next with excavation of broad bottoms; last, elevation and channeling, at present in progress. The general structure of the Catoctin Belt is anticlinal. On its core appear the oldest rocks; on its borders, those of medium age; and in adjacent provinces the younger rocks. In the location of its system of faulting, also, it faithfully follows the Appalachian law that faults lie upon the steep side of anticlines. After the initial location of the folds along these lines, compression and deformation continued. Yielding took place in the different rocks according to their constitution. Into this system of folds the drainage lines carved their way. On the anticlines were developed the chief streams, and the synclines were left till the last. The initial tendency to synclinal ridges was obviated in places by the weakness of the rocks situated in the synclines, but even then the tendency to retain elevation is apt to cause low ridges. The drainage of the belt as a whole is anticlinal to a marked degree, for the three main synclinal lines are lines of great elevation, and the anticlines are invariably valleys. In order of solubility the rocks of the Catoctin Belt, within the limits of Loudoun County, to which section all subsequent geologic data will be confined, stand as follows: 1. Newark limestone conglomerate; calcareous. 2. Newark sandstone and shale; calcareous and feldspathic. 3. Newark diabase; feldspathic. 4. Granite; feldspathic. 5. Loudoun formation; feldspathic. 6. Granite and schist; feldspathic. 7. Catoctin schist; epidotic and feldspathic. 8. Weverton sandstone; siliceous. All of these formations are in places reduced to baselevel. The first three invariably are, unless protected by a harder rock; the next three usually are; the Catoctin schist only in small parts of its area; the Weverton only along a small part of Catoctin Mountain.