County, North Carolina. He finds that the gneisses of Roan Mountain, and the similar rocks at its western base, which include considerable masses of very pure magnetic iron ores, are Laurentian, but that there are indications of a belt of Huronian schists along the western border. These Laurentian gneisses to the eastward are succeeded by a great breadth of thin-bedded gneisses, with highly micaceous and hornblendic schists, which he refers to the Montalban series, to which belongs the narrow belt of dunite or olivine rock found on the line of section near Bakersville. These Montalban strata are intersected by numerous endogenous granitic veins, which are extensively worked for mica, and yield, moreover, finely cleavable orthoclase and albite, together with beryl, apatite, and the rarer minerals autunite and sarmarskite. The rocks of this series, often decomposed to considerable depths, were found to occupy the greater part of the country as far east as Salisbury, interrupted near Statesville, however, by granitoid gneisses of Laurentian aspect. The belt of granular quartzite associated with limestone, which is met with at the eastern base of the Blue Ridge on the Catawba River, near Marion, is referred to the Lower Taconic, of which it has the characters. Portions of this quartzite are granular and flexible, and constitute the rock known as flexible sandstone, or itacolumite. This granular quartzite is regarded by Hunt as identical with the Primal white sandstone of Pennsylvania. The gneisses of Bellisle, near Richmond, Virginia, are, according to this observer, to be referred to the Laurentian period.

GEOLOGY OF THE CINCINNATI ANTICLINAL.

Safford has pointed out the evidences that this anticlinal, which in Kentucky and Tennessee brings up between the Appalachian and Illinois coal-basins the limestones of the Trenton, was represented by an island during the Silurian

age. There were two marked elevations along the line of this axis, of one of which Cincinnati is near the centre, while another is near Murfreesborough, Tennessee; a depression in Southern Kentucky separating the two.

The summit of the Cambro-Silurian series, represented by the Cincinnati shales, the equivalent of the Utica and Loraine of New York, is in the southern area directly overlaid by the

black shales of the Devonian. The Medina, the Clinton formation, with its dyestone or fossiliferous iron ores, and the Niagara and Lower Helderberg groups, were not deposited over this island-area, and in approaching it thin out, as might be expected. During the Medina and Clinton periods the land extended far to the west, while during the Niagara and Lower Helderberg times the extension was more or less easterly.

THE CARBONIFEROUS ROCKS IN KENTUCKY.

Shaler has considered the question whether the Appalachian and Illinois coal-fields were at one time connected. Both of these, as is well known, extend into Kentucky, of which they occupy respectively the eastern and western portions, and are separated by an interval of about seventy miles in the centre of that state. He has found, in the progress of the geological survey of Kentucky, that there are everywhere across the area evidences that the coal-bearing strata were at one time continuous. In numerous localities, at altitudes of from 250 to 300 feet above the nearest streams, are found débris, evidently derived from the coal-formation. These include numerous masses of cannel-coal, with fragments of the characteristic sandstones and conglomerates, and in some cases organic remains, which leave no doubt that these were derived from rocks of the coal-period; while farther to the southward were found evidences of the underlying millstonegrit. He points out that the conditions in which these occur are such as to exclude the notion that they are of the nature of drift, and maintains that they have been left by the waste of these formations by atmospheric agencies.

Newberry, in a recent report of his observations made in 1859, describes a similar remarkable example of erosion on a grand scale in the upper part of the Colorado plateau. Here, resting conformably upon the Carboniferous limestone, are the variegated sandstones and shales of the Lower Mesozoic, which pass upwards into the massive sandstones of the Lower Cretaceous. Above these were once spread not less than 2000 feet of soft shales belonging to the Middle and Upper Cretaceous, of which there now remain over great areas only occasional mounds of the strata, and vast numbers of organic remains scattered over the surface, the great mass of strata having been worn away by subaerial agencies.

THE ONTARIO SALT REGION.

The existence of a salt-bearing horizon known as the Onondaga or Salina formation, in the Silurian series in New York, between the Niagara and Lower Helderberg limestones, has long been recognized. The brines of Syracuse and its vicinity are, however, obtained not directly from this formation, but from an ancient gravel which fills an old lake-basin excavated on the outcrop of this formation; and the existence of rock-salt at this horizon was not demonstrated. In 1866, however, Hunt described the occurrence of rock-salt, detected in a boring at Goderich, Ontario, on the east shore of Lake Huron, and expressed the opinion that the deposit occupied a position identical with that which supplies the brines of Syracuse. In 1876 a boring to explore this salt was made at Goderich with a diamond drill to the depth of 1517 feet in horizontal strata, and from the cores he has been enabled to study the geology of this deposit. The Oriskany sandstone and the Lower Helderberg limestone, which are found in Eastern New York above the Salina formation, are here wanting, and the superficial strata at and near Goderich have been regarded by the geological survey of Canada as the base of the Upper Helderberg or Corniferous limestone. The salt was reached at a depth of 997 feet, beneath which were found 520 feet of red and brown marls, alternating with beds of anhydrite and rock-salt, the boring having been discontinued without reaching the base of the formation. Six beds of salt were met with, the thickest two being about thirty-one and twenty-five feet-the latter exceedingly pure. Above the rock-salt are still 121 feet of variegated marls, making in all 641 feet, followed in ascending order by 243 feet of dolomites with gypsum, making 884 feet supposed to belong to the Salina formation. To this succeed 276 feet of limestone, with layers of chert and with fossil corals; and, finally, 278 feet of dolomites like those below the limestone, but without gypsum. The organic remains of the limestone, so far as can be ascertained from the cores got in boring, resemble those of the Upper Helderberg, from which, however, they are separated by nearly 300 feet of dolomites, resembling those of the underlying Salina series, and perhaps corresponding to the Water-lime beds of New York. It is sug

gested, in explanation of this, that there was a temporary depression of this western salt-area, permitting the deposition of the lower fossiliferous limestones from the outer ocean, upon the saliferous series; after which a second movement of the surface excluded the ocean for a considerable period while the upper dolomites were laid down, to be in their turn covered by the Corniferous limestone. A shaft now being carried down for the purpose of working these beds of rocksalt will permit the paleontological study of the question.

SUBTERRANEAN TEMPERATURE.

The observations on the temperature made in the deep boring at Sperenberg, near Berlin, in Prussia, have of late attracted considerable attention. The depth penetrated here is 4052 Rhenish feet (4172 feet English), the whole distance being in rock-salt, with the exception of the first 283 feet, which were in gypsum and anhydrite. The early observations were unsatisfactory, and, as since appears, incorrect. They showed a greatly diminished rate of increase in descending, from which Mohr reasoned to the absence of any subterranean heat. His conclusions are, however, rejected as fallacious by Dunker, to whom we owe the observations on the temperatures in this boring. The first determinations of the latter were found to be vitiated by the circulation of water in the bores, which, it was shown, was the cause of a considerable reduction of temperature. This source of error was subsequently obviated by the use of plugs at suitable distances; and, from the corrected observations thus obtained, it was found that although there were still considerable variations in the rate of increase, as determined for intervals of 200 feet down to 3390, the mean rate of increase in the temperature was one degree of Fahrenheit for 50 Rhenish or 51.4 English feet-a figure agreeing closely with those previously deduced from many observations in other localities. The rate of increase for the upper 700 feet, which were partly in gypsum and anhydrite, was found to be 3.24 degrees for each 100 feet, while for the distance from 2100 to 3390 feet it was only 1.49 degrees. From some recent experiments undertaken in connection with this problem, Herschel has found that the conductivity of rock-salt is exceedingly high, and, according to him, "theory shows that the rates of in

crease in superimposed strata should be inversely as their conductivities;" so that the more rapid increase of temperature in the upper 700 feet of the Sperenberg boring may be attributed to the relatively small conductivity of the gyp sum and anhydrite. It is not impossible that heat evolved during the hydratation of the latter may have contributed to this result.

Careful observations by Symons in a boring near London, at a depth of 1000 feet, extending over a period of eighteen months, show that the temperature at that depth, as might be expected, suffers no perceptible changes.

TERTIARY FORMATION OF THE ARCTIC REGIONS.

In connection with the discussion in the Record of last year (page cii), it may be noticed that Fr. Schmidt has summed up our knowledge of the Tertiary geology of the North. The Miocene there shows a great continental area characterized by coal-seams and by a rich fauna, and is traced from the Amoor basin into Kamtchatka, Alaska, Vancouver's Island, and eastward as far as Mackenzie River, Greenland, and Spitzbergen. The Pliocene was a marine deposit, and is not known in continental Siberia, but occurs in Sakhalin Island, in Kamtchatka, and the Aleutian Islands, and extends to Oregon and California. Of its fauna the greater number of species inhabit to-day the North Pacific, but some are found only in the Polar Sea and the North Atlantic. He concludes that the fauna of the two oceans was then more alike than at present, and that these were then more closely connected through the Polar Sea.

FOSSIL FLORAS.

Heer, from his studies of the fossil floras of Greenland and Spitzbergen, concludes that the facts are against a gradual transformation of plant-types, since, in the Upper Cretaceous, dicotyledons suddenly appear in great variety, while other forms at this period disappear as rapidly. He supports the view of an arctic origin and a southern migration of plants, and declares that his investigations of the northern fossil floras do not indicate any alterations of climate or former iceperiods in these regions. He thus confirms the conclusions of Nordenskjöld as stated in the Record for 1876 (page cii).