As stated above, little is known of the process by which the Appalachian valley and the western portion of the province was added to the Paleozoic continentwhether the folding and emergence took place at the same or at different periods. If the corrugation was extremely slow the larger streams may have been and probably were able to cut their channels through the rising folds and for a long time hold their original or antecedent courses toward the northwest. On the other hand, if the folds rose rapidly the streams must have been ponded and most of them diverted to entirely new courses in the synclines ; but by the process of river adjustment the final result would be the same in either case. The difference would be that if the folding were very slow the drainage would be first antecedent and then subsequent, while if it were rapid it would be first consequent and then subsequent. Since there is no evidence in this region, so far as known, that lakes formed by corrugation ever existed, only the first hypothesisthat of slow and long-continued foldingneed be considered. Local diversion of small streams may very likely have taken place by folding, but the drainage at the close of the Cretaceous cycle was essentially the result of spontaneous adjustment of the streams to the structure surface revealed by erosion. The chief difficulty in deciphering the record of this drainage development is to determine how much of the adjust-ment took place within this cycle and how much before its beginning. Drainage of northern Virginia.In the northern portion of the province the main streams held their westward courses across the rising folds and found an outlet in the shrinking mediterranean sea. At some time during the early part of the cycle a depression occurred in the present piedmont plain, in which the Newark sediments were subsequently deposited.