_The Tariffville cut._ Before attempting to answer the second question, “why the river flows north at Farmington?” let us consider for a moment the history of the Tariffville cut. The river occupies a gorge whose sides are steep and talus covered, but which is not at all clogged with drift. There is naturally no room at or near the water level, even for the wagon road, place for which has been blasted near the top of the gorge. The profile of the gap shows a gentle ascent from the top of the gorge, up to the nearly level crest line of the ridge. That is to say, the recent gorge has been cut in the bottom of a sag in the ridge. We have already given our reasons for believing that the gorge here is much younger than the Westfield river gap; that it is a part of the work of the next cycle; that it is post-Tertiary. The sag, however, in the bottom of which the gorge is cut, is clearly of the earlier cycle. The bottom of the sag is much above the level to which the rivers had cut their valleys in the late Tertiary, and, therefore, it is certain that a river could not have occupied it at the close of that cycle. It was probably an abandoned water-gap whose stream had been captured in the same way and in the same cycle as the river, which formerly occupied Cook’s Gap. The fact that the sag and gorge, although located very near a fault line, do not correspond to it, but are transverse and independent of it, is instructive and needs a moment’s attention. It seems probable that the stream consequent upon the faulted blocks would have flowed down the slope of the tilted block and then along the fault line at the foot of the fault cliff and would have held this course during the baseleveling of the country. When the area was baseleveled the stream must have swung from side to side in its broad flood plain, and thus departed from the fault line. When it was revived by the post-Cretaceous uplift, it was confined to the course it had unwittingly taken on the sandstones just above the hard ridge, and it was forced to cut down through the trap. Subsequently a rival, which did not have to work against this obstacle, abstracted its head waters and the gap was abandoned. The accompanying diagrams may make this easier to understand. Figure 3 is a cross-section of the faulted monocline, R showing the position of the river along the foot of the fault cliff. The line B L represents the surface of the country after baseleveling, the trap outcrops forming _low_ hills (much exaggerated in the diagram). Figure 4 shows the dislocated trap sheets, the fault line and the winding course of the river, which has abandoned the fault line except where it passes between the low trap hills. Here the country is at baselevel. Figure 5 represents the region after the elevation and resulting erosion. The trap ridges have become more pronounced, and have migrated eastward in the direction of the dip. The river has been slowly let down upon the northern one from the sandstone