lain from place to place, wherever the crystalline rocks sank below the present level, by equally compressed synclinals of limestone. (4) There is a break at the trap dyke of West Conshohocken, disturbing the measures, to an extent not entirely known. Finally there follows a series of tightly folded plications, in which the hydro-mica-schist seems, as a mass, to be always below the limestone: and finally the unconformable contact with the clays of the Buck Ridge. The conclusion that the writer draws from this small area is also strictly conformable to the conclusions he has drawn from his study of the contact line of limestone and schist from Tredyffrin townships to Quarryville, and in fact along the entire border line. of schist and limestone in Chester, Lancaster, York, Cumberland and Franklin Counties, Pennsylvania. So far as the Chester Valley is concerned it adds additional ground for believing the theory established by the writer in his Thesis presented to the University of France in 1882; i. e., that the Chester Valley represents the northern half of a synclinal of which the southern half has been cut off and thrown up on the south, bringing the pre-Cambrian schists in contact with the lime stone. IDENTIFICATION OF THE GREEN MOUNTAIN GNEISSES IN EASTERN NEW ENGLAND. By Prof. C. H. HITCHCOCK, Dartmouth College, Hanover, N. H. [ABSTRACT.] THE subject was illustrated by a large diagram not reproduced in this volume, which delineates in detail the positions of the various crystalline groups upon thirteen parallel lines between Massachusetts and Canada, extending usually from Maine to New York across the two states of Vermont and New Hampshire. 1. The typical area of the Green Mountain gneiss is that of the main range of the elevated district. The rock is visible upon every one of the sections, and appears to exhibit an anticlinal structure. The first suggestion of this structure was provisionally made by C. B. Adams in 1846, substantiated in the final report of Vermont 1861, and finally admitted by J. D. Dana in 1882 for the southern part of the state. 2. This gneiss is identified in southern Vermont, New Hampshire and Massachusetts by its repetition in anticlinal folds. As it reappears it possesses essentially the same lithological characters; but a similarity is not regarded as identification unless indicated by exact mineralogical features. We oppose the doctrine that a gneiss may be replaced by a synchronous mica schist, syenite, hornblende schist, or any other unlike rock. 3. The following are the areas supposed to be identical with the Green Mountain gneiss: (1) between Halifax and Hartland, Vt., (2) between Winchester and Milan, N. H., running nearly the whole length of the state, (3) in the Contocook valley and to the north in Warner, (4) between Jaffrey and Weare, N. H., (5) between Temple and Hopkinton, N. H., (6) the very important area occupying the basin of Lake Winnipiseogee, which may be a repetition of (3) to (5), (7) a highly crystalline range from the Massachusetts line at Mason to Barrington. This is the northward continuation of part of the Worcester Co. gneiss in Massachusetts. (8) from Nashua to Fremont, N. H. This is the Chelmsford and Bolton range of Massachusetts. 4. It is supposed that this gneiss is of Laurentian age. Our division of that system is threefold: first, at the base, the various areas of porphyritic gneiss, supposed to be allied to the Ottawa, Laurentian of Logan; second, our Green Mountain gneisses as detailed above; third, the Montalban or Upper Laurentian. As shown in my New Hampshire Report the Montalban underlies the Huronian. THE HORIZONS OF PETROLEUM AND INFLAMMABLE GAS IN OHIO. By Prof. EDWARD ORTON, Columbus, Ohio. [ABSTRACT.] PETROLEUM and carburetted hydrogen gas are widely distributed in stratified rocks. All rocks of the Ohio scale are likely to show the presence of one or both, when penetrated under deep cover. The supplies of economic value have thus far been found in Devonian, Sub-Carboniferous and Carboniferous series of the state. The Devonian rocks yield a small amount of low-pressure gas. The coal measures yield small quantities, at several horizons, of both gas and oil, but the main supplies in Ohio are derived from the SubCarboniferous series. The boundaries of this series are still in dispute, but the general order of its elements is well settled. Two of these elements, and two only, have interest as repositories of petroleum and gas, viz., the Logan Group and the Berea Grit, the former having a thickness of 150 to 200 feet and the latter ranging from 5 to 50 feet. In situation and general geological relations, both of these strata conform to the requirements of "oil sands" as now understood. An "oil sand" is a sandstone or conglomerate immersed in shale. The Berea Grit has beneath it the great series of shales, viz., the Bedford-Cleveland-Erie-Huron Shales which stretch below in inseparable beds for 1800 feet, at least in the centre of the coal basin. It is covered by the Berea Shale 20-50 feet thick and the Cuyahoga Shale, 250 to 500 feet thick. This same stratum, the Cuyahoga Shale, makes the floor of the Logan Group. The Logan Group is largely conglomeritic, and what is thus designated often overpasses the sub-carboniferous boundary, no doubt, taking in the Sharon conglomerate as well. The roof shales are accordingly of different series in different instances. The upper group is the main salt horizon of Ohio, the wells of the Muskingum, the Hocking and Ohio Valleys all being derived from this source. The Berea Grit is the main source of high pressure gas and of what oil, Ohio now yields. It also supplies brine to the Tuscarawas salt works. Recent records obtained from the very numerous drillings that are going down in many sections of the state show conclusively that the Berea Grit, often reduced to 5 or 10 ft. in thickness, is the source of these tremendous flows of gas that light up the country for miles, etc. THE CORRELATION OF THE LOWER COAL MEASURES OF OHIO AND EASTERN KENTUCKY. By Prof. EDWARD ORTON, Columbus, Ohio. [ABSTRACT.] A REMARKABLE symmetry has been seen to characterize the northern portion of the great Appalachian coal field by all who have studied it. The more full and accurate our knowledge becomes, the more clearly is it seen that the system grew in a very orderly manner. A number of the main coal seams, for example, can be traced by bodily continuations for scores and even hundreds of miles along the ancient margins of the seas by which they grew. The character of the coal may change and the seam may show by its expansions and contractions the varying changes of fortune it underwent, but the swamp holds on with unmistakable identity. The composition of the coal measures has been worked out much more fully and minutely in Western Pennsylvania than elsewhere and a general order has been established that must be considered final. The Lower Coal measures are found to contain a dozen seams all of which have minable thickness in some portion of their extent. These seams can be followed into Ohio and across Ohio. Three principal subdivisions in particular are conspicuous and easily traced, viz., the Mercer Group, the Kittanning Group and the Freeport Group of coals and associated elements. It is evident that the coal field of Eastern Kentucky is part and parcel of the same field that we follow from Pennsylvania across Ohio, and yet there has been as little recognized community of structure, aside from one or two elements, as if the fields had grown with separate histories. But the moment that the sections are followed across the valley, the identity comes to light. Prof. A. R. Crandall is our authority for Eastern Kentucky. Uniting with him in an examination of type sections in both fields, it becomes obvious that one set of names will suffice for all the elements. Some drop out temporarily but the sections are maintained. THE SALT WELL AT HUMBOLDT, MINNESOTA. By Prof. N. H. WINCHELL, Minneapolis, Minn. [ABSTRACT] THE author gave a description of the section of the rocks passed through by the drill, which penetrates to the depth of 592 feet. The salt water rises from the bottom of the drift sheet, as well as from below a limestone 291 feet thick. It was thought to be from a great basin of brine which underlies the drift sheet, which consists wholly or nearly so of impervious clay, and hence permeates any rock-horizon which happens to compose the immediate surface. throughout a wide extent of territory, reaching from the valley of the Saskatchewan southward into Dakota and Minnesota. The strength of the brine was stated to be about one-third that of the Syracuse wells. Although formerly the brines of the northwest have been referred to the Cretaceous and to the Devonian rocks, the author thinks there is evidence of the existence of Carboniferous rocks in the country southwest of the Saskatchewan, parallel to those that bear brine in the state of Michigan,, and that it is very probable that this brine may become as valuable to the northwest as the brines of the Carboniferous have to the state of Michigan. A REVIEW OF THE GEOLOGY OF DELAWARE. RESULTS OF A SURVEY NOW IN PROGRESS. By FREDERICK D. CHESTER, Prof. of Geology, Delaware State College, Newark, Delaware. [ABSTRACT] REFERENCE is made to the early report of Professor James C. Booth (1841) and its deficiencies briefly discussed. The formations represented within the state are Metamorphic and Eruptive rocks of doubtful age, Cretaceous, Tertiary and Quartenary. An eruptive mass, a continuation of the syenitic areas of southeastern Pennsylvania, covers a club-shaped area lying just north of the P. W. & B. R. R., and consists of syenitic gneisses with associated Gabbros and Hyperites. The dip of these rocks is to the northwest, upon the flanks of which rest a series of micaceous gneisses and schists with which are associated seams of hornblende schist, vitreous quartz and dikes of orthoclastic granite. The mica schists and gneisses overlie a coarse magnesian marble, which itself is underlaid by a quartzitic rock of possibly Potsdam age. The probable order of the crystalline rocks becomes then-Quartzite, Magnesian Marble, and Mica Schists. The question of the Palæozoic age of the mica schists is here briefly discussed. Lying upon the upturned edges of the eruptive rocks are a series of strata of Cretaceous age dipping at an angle of 26' to the southeast. The width of the Cretaceous belt is eighteen miles. The subdivisions very nearly correspond to those of New Jersey. They are Plastic Clays, Sand Marl, Lower Marl Bed, Indurated Marl Bed and Middle Marl Bed. At Noxontown Mill pond the uppermost layer of the Middle Marl Bed is seen to dip beneath a ten foot stratum of blue clay in which have been found fossils of Miocene (?) age; near the latitude of Murderkill Creek the Miocene is succeeded by three feet of clay |