III, everywhere else filling up the Havise valley [1] to within 4 miles of the Union county line, into which county it is prolonged in the White mountain anticlinal. It is scarcely traceable beyond Penns creek at the base of White mountain in Union county.
3. The Milroy synclinal is a distinct and well-marked basin in Mifflin county, though scarcely discernable in Union county, along Weikert run back of the White mountain. Passing west from there it holds the red and white Medina sandstone in its trough for about 6 miles, the mountain finally terminating in a high spur of the Oneida sandstone No. IVa, known as Strong’s Knob[2] just northeast of Siglerville in Armagh township. At Moore’s grist mill, just west of the end of the spur, the synclinal is seen in the Hudson River slates No. III, with converging dips along the axis of only 10°, which however stiffen rapidly within short distances on either side of the axial line.
The trough keeps about the same elevation for the next 5 miles, holding only the slates, and passing about a mile north of Milroy with north and south dips of 10° and 20°, until west of Laurel creek it begins to deepen again to admit Straley’s Knob,[3] a high spur of Oneida sandstone, and the counterpart of Strong’s knob to the east.
On the road passing north through Cooper's Gap to Greenwood Furnace, north and south dips of 35° and 60° are exposed in the red Medina sandstone No. IVb, indicating the compressed character of the fold, and about 1½ miles west the white Medina sandstone of Millikin’s Knob marks the basin line, which passes thence west into Huntingdon county as the Greenwood basin.
4. The Jack’s mountain anticlinal of Union county succeeds this basin on the south, though represented in Mifflin county by the valley rocks Nos. III and II. This is the central one of the three anticlinals of the Kishacoquillas valley, passing through the Triester Valley[4] to Sig-
