schists. As elsewhere explained, a fault undoubtedly exists between k and 1; and the upheaval of the mountain may have been the reason why the schists are more elevated and disturbed than the underlying members. This may be styled a classic section for the Taconic rocks on Penobscot bay, since it is the best one for showing the natural order that can be found in this region, and it will be prized as such. One end of the Camden belt of Eolian limestone now appears to terminate in the bay. We have no doubt it continues for considerable distance under water; and suspect that it is directly connected beneath the schists with the Thomaston limestones; per haps very much in the same way that we thought a connection existed between the limestones exposed at Holmes' and Ingraham's quarries. Trap Dikes. In the principal quarries of limestone in Rockland and Thomaston interesting dikes of trap occur. To the workmen they are a nuisance, but to the geologist are full of interest, as indications of ancient molten masses like lava, in this vicinity. When the rocks about here were being tilted up at various angles, folds were formed and many large masses were broken apart. Molten matter from beneath then crowded up and filled many of the crevices. When this lava had cooled, probably quite slowly, these dikes were found to be the result. These dikes we have seen in the Beechwoods, several of the Meadows, near Rockport, and in the Blackington Corners quarries. They are seen now as walls upon the sides, in the middle or crossing the quarries, being composed of a dark, tough, very fine grained rock. Occasionally a row of trap nodules seems to take the place of a dike. Trap Dike in the Beechwoods Quarry. An interesting example of a trap dike at the Beechwoods quarry is represented in Fig. 42. It is in the sketch seen to form a wall, which curves, and at the right hand side passes round a pillar of limestone facing the observer. It then crosses to the other side of the quarry, and continues on in a course parallel to its first appearance. That part seen in the sketch resting against the framework of limestone, is composed of numerous small columns, piled up with great regularity, as if done by hand, just as many sticks of wood are laid up with the sawed ends in front. At another quarry the limestone has been excavated from both sides of the trap, leaving the dike as a high wall in the centre of the excavation. A few other dikes were noticed in this region in other rocks. Near Owl's Head Light House we saw a dike of quartz eight feet wide, not perpendicular like those in the Eolian limestone, but inclined 70° S. 20° E. Pieces of the wall rock are found in it, as if torn off and mixed in the fluid mass at the time of its injection. Several quite large dikes of trap traverse the gneiss at Herring Gut Light House in St. George. They run N. 70° E., the same as the strike of the quartz dike. running N. W. and S. E., cuts Negro Island in Camden harbor. Several dikes (or almost beds) of trap occur in the Taconic schists and quartz rock in Belfast harbor. A small dike of white quartz, across the Taconic schists on 6. Taconic Schists. We now come to the consideration of the last solid formation of this region west of the Penobscot bay, the schists belonging to the Taconic system. In Emmons' scheme these were called "Magnesian slate," an inappropriate term, since both the term slate is improper, and they contain no magnesia. In Vermont we styled them Talcoid schists. But in Maine the Talcoid character is very obscure, and in its stead we find the mineral mica abundant. We do not suppose that it is essential to theory, that these schists should every where be talcose in their appearance, because they are so in Massachusetts and Vermont. At all events in Maine so much mica is present frequently that they cannot be distinguished from the older mica schists, and on account of this difficulty it will not be strange if we have improperly distinguished between them in our geological maps, particularly in South Thomaston. Three general deposits of these schists occur on the west side of Penobscot bay; first, those associated with the Eolian limestones of Thomaston and Rockland; second, a deposit in Camden; and third, a still larger deposit of interstratified schists and quartz rock running south-westerly from Belfast. To expedite the description of these deposits we will give a table of all the observal dips : 90° N. 40° W., 70° N. 40° W., 60° N. 30° W., 65° N. 50° W., 40° S. E., 70° N. 20° W. Camden Deposit. do. at last house in Camden, Rockport, south of Goose river, Rockport, on north shore of harbor, Indian Island lighthouse, At junction with Eolian Limestone on Beaucamp's Point, do. 20 rods south-easterly, Deadman's Point, do. further east, Above Deadman's Point, Lily Pond, east side, Lily Pond, north of, High dip to N. 30° W. 50° S. 80° E. 40° S. 70° E. 35°-70° N. 60° W. 40° S. 60° E., 55° S. 60° E. 50° N. 80° E. 50° N. 40° W., REMARKS. Quartz rock. At west end. East end of village. East side. A local curve. Half mile south. North of last observation. Near quarries. On east road to Rockport. · Figs. 37, 38, 39 and 40, show the relations of the Taconic schists to the adjacent formations. If these sections illustrate the natural order of the formations, then we must say at once, that a part of these schists are older, and a part more recent, than the Eolian limestone. We rely upon such cases as the exhibition of the strata in Holmes' and Ingraham's quarries, (Figs. 39 and 40,) to prove the schists in some cases the more recent of the two. And by the supposition of inverted folds, we may regard all the schists as the newest. For example; in Fig. 37, suppose the dolomite at the Marsh quarry to be the equivalent of the other belt of limestone at the Fulling Mill and Beechwoods quarries. Then the intervening schist is newer than both kinds of limestone, and the western mass of limestone contains two or three inverted folds. Similar suppositions can reduce the other sections to the same order. It will be interesting, in this connection, to compare the theoretical order of these formations with the actual existing order in Camden, as shown in Fig. 41. There the schists are all above the limestone, except a few that have been disturbed by a fault. A little study of the preceding table of dips will show us a few axes besides those figured. An interesting one is situated west of Marsh's mountain, both in Rockland and Thomaston. It extends for a considerable distance-a mile or so we have followed it; and the crest of the ridge has been worn away while the sides |