Z

Fig. 11.

In Devonshire he establishes two lines of vertical cleavage, sixty miles apart, one at Stoke Fleming the other at Bickington; and they bound a broad area over which the cleavage planes undulate in low flat waves, the axes of which bear between E. and E.N.E. The annexed cut represents the relation of the planes of bedding and cleavage in these undulations near Launcestown and on the coast near Tintagel. The continuous lines represent the bedding and the dotted lines the cleavage. After stating other similar facts from different districts in England, Mr. Sharpe remarks as follows, with regard to the relation of the cleavage planes to the bedding in Devonshire :

"Throughout the central area where the cleavage is nearly horizontal, the beds undulate in a succession of waves already described without offering any marked features. These undulations are sharper towards Bideford, where we may expect to find the cleavage highly inclined. At the Bickington limestone quarry, where the vertical line of cleavage passes, the beds are most violently contorted. Beyond this line is low ground at Barnstaple, in the band between the two lines of vertical cleavage. From Pilton to Ilfracombe, with cleavage highly inclined, the strata are elevated in high hills, and at Linton, where the inclination of the cleavage is only 35, the beds seldom dip more than 5. So again on the S. coast of Devonshire, disturbed and elevated strata occur in company with highly inclined cleavage. These observations are less complete than those relating to Carnarvonshire, but the theoretical conclusions to be derived from them are the same.

"The regularity of the direction of the cleavage is not at all broken in the neighborhood of the granite of these counties, from which it is to be inferred that the granitic eruptions had taken place and become solid before the cleavage was produced: indeed some remarks of Sir H. T. De la Beche lead me to suppose that the cleavage is continued through the granite."

Mr. Sharpe having deduced from the distorted shells that "the slaty rocks had undergone compression in a direction perpendicular to the planes of cleavage," and "that this compression was compensated by an expansion in the direction of the dip of the cleavage," enters upon an explanation of the non-conformity of the bedding to the cleavage planes. Assuming that the elevation was produced by an elevating force beneath the area, he argues that there will result from such elevating action, besides a grand central arch or anticlinal axis, other subordinate fractures and dislocations either side; and that thus the various anticlinal axes in figure 9 were produced, while only the main or central one influenced the direction of the cleavage planes. With regard to the manner in which the cleavage structure has been occasioned, or the cause of this peculiar feature, Mr. Sharpe simply enumerates some of the views which have been presented, expressing at the same time the hope that the observations he has made may hasten its discovery: an end which must surely be promoted by observations of so great interest followed out with the care and discrimination exhibited in the important memoir, of which a brief abstract has been here presented. 4. Geological Society of London, April 14th, 1847.-A paper was read, entitled, "On the Structure and probable Age of the Coal Field of the James river, near Richmond, Virginia;" by CHARLES LYELL, F.R.S., V.P.G.S.

SECOND SERIES, Vol. IV, No. 10.-July, 1847.

15

This coal field, which is about twenty miles long from north to south and from four to twelve in breadth from east to west, is situated twelve miles west of Richmond in Virginia, in the midst of a granitic region. The rocks consisting of quartzose grits, sandstones, and shales, precisely agree in character with the ordinary coal measures of Europe. Several rich seams of bituminous coal (the principal one being occasionally from thirty to forty feet thick) occur in the lower division of the strata, which are arranged in a trough and are much disturbed and dislocated on the margin of the basin, where they have a steep dip, while they are horizontal towards the centre.

The fossil plants which have been determined by Mr. Charles Bunbury, differ specifically, and most of them generically, from those found fossil in the older or palæozoic coal formation of Europe and North America, and resemble, as Prof. W. B. Rogers first truly remarked in 1840, the plants of the oolite of Whitby in Yorkshire, some few however being allied to fossils of the European trias.

From the upright position of the Calamites and Equisetæ Mr. Lyell infers that the vegetables which produced the coal grew on the spots where the coal is now found, and that the strata were formed during the continued subsidence and repeated submergence of this part of Virginia. The shells consist of countless individuals of a species of Possidonomya, much resembling P. minuta of the English trias. The fossil fish are homocercal and differ from those previously found in the new red sandstone (trias?) of the United States. Two of them belong to a new genus and one to a Tetragonolepis, and they are considered by Prof. Agassiz and Sir P. Egerton to indicate the liassic period.

The analysis of the coal made by Dr. Percy and Mr. Henry, shows that it contains the same elements, carbon, oxygen, hydrogen and nitrogen, in the same proportions as the older bituminous coal of Europe and North America. Alternating layers of crystalline coal, and others like charcoal, are observed in many places, and in the charcoal, Dr. Hooker has detected vegetable structure not of Ferns or Zamites or any conifer, but perhaps of Calamites. The coal yields abundance of gas used for lighting the streets of New York and Philadelphia, and some fatal explosions have taken place in the mines, some of which are nine hundred feet deep.

Volcanic rocks (dikes and beds of intrusive greenstone) intersect the coal measures in several places, hardening the shale and altering the associated coal, the latter being in some places turned into a coke used largely for furnaces.

The author concludes by expressing his opinion that the evidence of the fossils, although some of them belong to forms usually found in the trias, preponderates upon the whole in favor of regarding the coal field of the James river as being of the age of the inferior oolite and lias.* A paper was next read, entitled, " Descriptions of Fossil Plants from the Coal Field near Richmond, Virginia;" by CHARLES J. F. BUNBURY, F.L.S., F.G.S.

For the memoir of Prof. Wm. B. Rogers, in which this conclusion was sus tained by the same arguments in 1842, see Report Assoc. Amer. Geol. and Nat., 1840-1842, p. 298.

The author describes fifteen different forms of vegetable remains, of which, however, only nine or ten are sufficiently well preserved to be determined with any precision. Six are Ferns, of which three belong to Pecopteris, one to Taniopteris, one to Neuropteris, and the sixth appears not to be referable to any genus hitherto described. The Neuropteris, and one of the species of Pecopteris, are new. One of the ferns is believed to be identical with Pecopteris whitbiensis, a species characteristic of the oolites of the Yorkshire coast. There is one species of Equisetum,—E. columnare-likewise characteristic of the Yorkshire oolites; one, or perhaps two of Calamites; two (which may possibly be mere varieties) of Zamites; the remainder are obscure impressions of an equivocal nature, but of which one has a certain degree of resemblance to a Stigmaria, and another to a Lepidodendron. Five of these fossil plants had previously been determined and described by Prof. W. B. Rogers, namely, Taniopteris magnifolia, Pecopteris whitbiensis, Equisetum columnare, Calamites arenaceus, and Zamites obtusifolius. Prof. Rogers described also a few other species, which do not occur in the collection made by Mr. Lyell.

From a comparison of these vegetable remains with those found in European strata, of which the geological position is well known, it may be concluded with tolerable certainty, that the Richmond coalfield is of later date than the great carboniferous system, and that it must be referred either to the lower part of the Jurassic, or the upper part of the Triassic series,-more probably to the former.

5. Remarks on a Boulder Mass of Native Copper from the southern shore of Lake Superior; by FORREST SHEPHERD, (communicated by request, to Prof. Silliman, for this Journal.)-The mass of native cop. per in my possession, was discovered on the southern shore of Lake Superior in July, 1845, by Tousant Piquette (an Indian of the Ojibwa tribe) in or near latitude 47° 5' north, and longitude 88° 5' west. It is composed almost entirely of pure native copper with spots of pure metallic silver upon its surface, together with a few water-worn pebbles of syenite, sandstone, &c., strongly imbedded and fastened in its cavities and sinuosities. Its length is about three feet and a half, its breadth two feet and a half, thickness from seven to eight inches, and its weight sixteen hundred and twenty-five pounds. As a specimen, its form and proportions could not well be better. One end is broader by a few inches than its opposite. One side discovers a slight natural rotundity and also a deep furrow cut obliquely into the solid metal, while the other side, nearly flat, appears much worn and polished in some places, whilst in other places it exhibits numerous grooves, scratches and broad longitudinal furrows, showing evidently that the mass has at some period been subject to great external violence. When found it was situated immediately upon the shore about three miles northeast of Elm river, not more than two or three feet above the water, and only about six feet from the broad side of the lake. It was standing on its smaller end, nearly in a perpendicular position, leaning slightly against a much larger boulder of sienite. The lower end was buried in the gravel of the shore about ten inches, and immediately underneath it were found pebbles and small boulders of porphyritic greenstone, syenite, sandstone, &c., and also an undecayed log of white cedar (arbor vitæ) on which it rested. Around it, both in the lake, and upon

the neighboring shore, and occupying a space of several acres, were seen in promiscuous assemblage, a multitude of boulders both large and small, composed chiefly of granite, syenite, greenstone, conglomerate, and red sandstone, apparently the companions of this extraordinary specimen. There is no stream of any magnitude or importance nearer than Elm river (three miles), which although called a river, is not more than twelve or fifteen feet in breadth. All along this coast and for many miles southward is a dense forest of large trees, such as white cedar, spruce, hemlock, pine, poplar, birch and maple; the growth of which, must have occupied four or five centuries.

The stratum of rock underneath this assemblage of boulders is red sandstone nearly horizontal, dipping northward into the lake at an angle of two or three degrees. About eight or ten miles southward is a ridge of stratified greenstone, generally called trap by explorers in this region. This ridge runs northeast and southwest nearly, and attains a height of five or six hundred feet. In this greenstone are numerous veins containing native copper with occasional spots of silver. These veins or lodes of copper, cut the above ridge at right angles and extend into a formation of conglomerate which reclines immediately upon the greenstone. Native copper is found also in the conglomerate. The red sandstone above mentioned reposes upon the conglomerate, so that there is a gradual descent from the summit of the greenstone ridge to the shore of the lake (a distance of eight or ten miles) where the copper boulder was discovered. From the adhesion of pebbles to the depressed and cavernous portions of this copper boulder, there is strong probability that it was derived from a vein in the conglomerate. But it could not have well been removed from the neighboring ridge, since the existence of the present forest; and it has evidently been deposited in the place where it was discovered, since the growth of the medium sized arbor vitæ on which it rested. The shore of the lake at this place is of moderate elevation varying from six to ten or twelve feet. island of Isle Royal with its sandstone conglomerate, porphyry, and greenstone, is situated about fifty miles due north, and granite and syenite, similar to the boulders, accompanying the copper rock, exist in place on the northern shore of the lake, a distance of one hundred miles or upwards. No rocks of this description are known to exist nearer in situ.

The

6. On Fossil Trees found at Bristol, Conn., in the New Red Sandstone.-Two fossil trees have recently been discovered by the quarrymen who were excavating building stones in a sandstone quarry on the banks of the Pequabuck river in the town of Bristol, Connecticut. This town is on the western border of the greater secondary basin of Connecticut, and the locality where these fossil trees were found is not far from the junction of this deposit with the western primary ranges. The sandstone beds which crop out upon the banks of the Pequabuck, are fine grained, argillaceous and well adapted for many architectural purposes. No organic remains have before been observed in them, with the exception of a few ill characterized and obscure impressions of reed-like vegetation, upon the surface of a fissile stratum of argillaceous sandstone which is met with at a point about four feet above the bed containing the trees.

The writer's attention was called to these fossils by a letter from Mr. N. S. Manross of Bristol, (a member of the academical department of Yale College,) whose father owns the quarry where they were found. This gentleman had the consideration to preserve these interesting relics from destruction until they had been visited by the writer in company with R. Bakewell, Esq., to whom we are indebted for the accompanying sketch of the quarry with the two trees as they appeared, at the time of our visit.

It will be observed that the trunks are nearly parallel to each other in the plane of stratification of the beds, and nearly at right angles to the strike of the strata. Their buts point toward the river, while their heads are buried beneath the unopened sandstone. Several branches were to be traced from the principal trunk, one of which reached (in the dotted line) to the distance of eight or ten feet from the body and nearly at right angles with it. The bed in which these trunks were found is quite unlike the fine grained red deposits above and below them, being a rather coarse grained grey quartzose grit, sprinkled with mica and carbonaceous particles. It is very tender and friable when first exposed, and the trees which were imbedded in it were not properly petrified, but existed in the condition of soft lignite, in which the vegetable structure could be detected only on close observations. A rough exterior having the general appearance of the outer bark of the common yellow pine, was all the general character that could be observed. They were much flattened by the pressure of superincumbent rocks, not being over four inches thick in the thickest parts and thinning out to the edges. The