DESCRIPTIONS OF THE FORMATIONS. 21 



bedded, dark bluish-gray, fine grained limestone, two to six inches thick, with 

 shaly partings between the layers. In Northern Illinois it is bituminous, and consists 

 of sandy shales with thin bands of limestone. Ill Iowa it .is the Maqueketa shales, 

 which are bluish and brownish shales forming a stiff clay soil. In Missouri the 

 upper shale bed only is found, with an occasional flag-like limestone layer. 



On the west bank of the River Hudson this formation continues uninterruptedly 

 from Kingston to Saratoga Lake, and on the east side of the river also, it is clearly 

 denned along the valley, with a width of from one to several miles, varying 

 and irregular in outline from Rhinebeck to Lake (Jhamplain, its eastern limit 

 approaching the river at the former place. J. Hall, A. A. A. Sci. 1877. 



The N.Y. C. & H. R. R. R. runs on it for 65 miles, from below Rhinebeck to 

 Troy, and the formation continues along the river many miles further northward. 

 The name Hudson River is, therefore, highly appropriate for the formation. The 

 shales and impure sandstones are upturned, and thereby modified in character along 

 the river, but they are no older than the horizontal rocks in the Mohawk valley, a 

 few miles west of the River Hudson, and at Frankfort, Loraine and Pulaski. They 

 have the same fossil contents, and their direct continuity can be traced. There is, it 

 is true, a great mass of metamorphic shale and sandstones to the eastward of those 

 on the river above described, and between them and the state-line, which contains 

 different fossils, and belongs to an older formation, called the Quebec group. But 

 the Hudson River formation is the same which extends through Canada and the 

 Northwestern States, and southward through Ohio, Kentucky and Tennesee, where 

 it is called the Cincinnati and Nashville formation. It is very much to be regretted 

 that the original name of Hudson River has not been everywhere retained. 



There is more confusion and uncertainty about the Cambrian or Lower Silurian 

 formations in many localities than about any other portion of the whole series. 

 The difficulties arise from the scarcity of fossils, the disturbed and altered state of 

 the greater part of its rocks, from the absence of those which should immediately 

 precede and follow them, and which if present would show their position in the 

 series, and also from the difficulty of distinguishing them from those of greater 

 age adjoining them, and with which they are really or apparently blended.* 



*Overlying the various crystalline terranes described on pages 10-13, along the western border 

 of the Appalachian mountain belt from the Gulf of St. Lawrence to Alabama, are found extensive 

 formations, differing, it is said, from those, and from the fossiliferous rocks above them, which 

 have been the subject of much discussion. To these rocks, as displayed in the Taconic hills of 

 New England, Prof. Emmons gave the name of the Taconic system, which he divided into a lower 

 and an upper series. The views of Emmons are still held by Dr. T. Sterry Hunt, and others, and 

 there is agrowing belief in favor of the existence of such a series of rocks; but they are opposed by 

 Mather, Hall, Logan, Rogers, Dana, and the great majority of American geologists, who hold that 

 Emmons's Lower Taconic series is the stratigraphical equivalent of the Potsdam, Calcif erous,Quebec, 

 Chazy, Trenton, Utica and Hudson River, and his Upper Taconic, of the succeeding Oneida and 



Medina formations; their lithological differences from the same formations further west, being due 

 to some agency which has changed them, inducing crystallization, and obliterating their organic 

 remains. The purposes of this work will be best subserved by describing the formations in accord- 

 ance with the received opinions, of geologists, generally, without entering on controverted ground, 

 and merely stating briefly, that what is designated as the Upper Taconic, extends from Orange 

 County, New York, above Newburg, across the River Hudson, and through Dutchess and other 

 counties of Eastern New York ; thence through Western Vermont and Canada, as far as the city of 

 Quebec and beyond. The Lower Taconic, including a granular quartz-rock, and the Stockbridge 

 limestone, with roofing-slates, and soft, so-called talcose slates, extends from Vermont along the 

 western base of the South Mountain and the Blue Ridge, underlying the great Appalachian valley, 

 as far as Alabama, and having a thickness of 5000 feet. There is also a range, more or less contin- 

 uous, of this formation, from Delaware into North Carolina, where it is found at the eastern base 

 of the Blue Ridge, resting on the Montalban. 



According to Dr. Hunt, the Lower Taconic constitutes a fifth crystalline series, younger than 

 the Montalban, and by him distinguished by the name of TACONIAN, which includes the Auroral 

 limestones and the Primal slates of the Appalachian valley, with their limonites and crystalline iron- 

 ores, and also the itacolumites and the pyrophyllite slates of North Carolina. The Upper Taconic, 

 which comprehends the Quebec group of Logan, consists, in hia view, of uncrystalline strata of 

 Cambrian age, below the horizon of the Trenton limestone, 



