THE ARCADIAN COAL-FIELDS.
These coal-fields are located in the extreme northeastern limits of the ancient Appalachian Sea, and, by their singular and peculiar structure, offer conclusive evidence in favor of the propositions we have set forth and the theory which we regard as established by the facts developed in regard to the volcanic origin of the Paleozoic strata in the great basin.
It also proves conclusively the subsidence and consequent submergence of the eastern granite shores of the ancient sea. We find the coal-beds existing under the sea, and the deep basins or measures in which these beds exist 10,000 feet or more below the common bottom of the Atlantic Ocean.
In this remote corner of the great Appalachian basin there seems to have been originally a series of deep basins, as in the region of Pennsyl vania anthracite. But instead of these deep basins becoming filled up with the coarse sedimentary material of eruptive volcanoes, which existed in the vicinity of the anthracite basins of Pennsylvania, and, consequently, filled them, the former or Arcadian basins were slowly and gradually filled with the fine floating particles of dust or sand which the waves or the winds carried to a great distance, or became filled with the limestones which always accumulated in the regions of deep and quiet waters.
Active volcanoes did not exist to any great extent in the vicinity of the Arcadian fields. Those which may have existed were local, and effected no material change in the features of this portion of the earth's surface. But while volcanic vents did not exist to fill with decomposed or water-crushed lava the deep Arcadian basins, the eruptions of the long line of vents to the south not only produced part of the material to fill them, but produced the result which depressed them below the level of the Atlantic.
We have no doubt but'that this depression was slow, and the process of accumulating the vast pile of measures which now fill these basins gradual and continuous. While the coal formed in the anthracite basins and quiet
reigned over the face of the vast inland seas, the limestones grew in Ar cadia as they grew in the West, but perhaps faster.
The probable depth of these basins is not far from 20,000 feet, and the thickness of the coal measures in the deepest not much short of 15,000 feet. It is not probable that they were originally of this great depth, but that they have increased their original depth by the gradual subsidence which took down all the Eastern mountains from Newfoundland to Cuba, and, consequently, the accompanying and nearest basins. But that they were originally deep there can be no doubt, since the first 2314 feet of measures contain no coal, and the next succeeding 3240 feet only nine small seams of coal, aggregating 10 inches in all, and corresponding to our false coal measures. Above this there are 2082 feet containing no coal. Thus we find that over 7000 feet of measures were precipitated into the deep waters of the Arcadian basins before workable coal-seams did or could com mence to form. Even then the depth in which they formed must be great, since the seams are extremely thin and unproductive : only 7 out of 47 seams are of workable size, and these contain only 20 feet of workable coal ; while the other 40 seams are only from 2 an inch to 14 inches in thickness respectively.
These 47 seams exist in 2819 feet of measures. AboNe these are 2134 feet of measures, containing 22 unproductive or thin seams, aggregating 5 feet of coal. The upper series, and perhaps the only truly productive portion of this immense thickness of measures, is 2267 feet thick, and contains 12 coal-seams, the thickest of which is 36 feet, the whole aggre gating 72 feet of workable coal in 6 seams.
The following data, from a reliable and interesting report by Capt. Thos. Petherick, may be depended on as representing the workable coal in the Pictou district of Nova Scotia.