ON SOME FOSSIL TREES RECENTLY DISCOVERED AT BURNLEY. By T. T. Wilkinson, F.R.A.S., &c., &c. (READ 18TH DECEMBER, 1856.) Discoveries of fossil trees are always interesting to Geologists. They speak to them of a state of things respecting which history is silent; and of myriads of years gone by which set calculation at defiance. The luxuriant Flora which such remains indicate afford a constant theme for their speculations; and although there may be much of reverie in the results of such musings, the importance of the subject can scarcely be overlooked by the more practical portion of mankind, since it has laid the foundation of all the sources of wealth consequent upon the existence and magnitude of the Carboniferous strata of our globe. In the earlier stages of the science of Geology, for such I presume it must now be considered, such discoveries as those to which allusion has been made, may have been regarded with more attention than they are at present. Their true positions in the classification of the Flora of the period have been in a great degree fully ascertained; most of the charateristic features of such vegetation may be considered as settled; and the nature of the climate in which it grew and flourished so abundantly is no longer matter of conjecture. The arrangement of the fruit and leaves which have adorned the massive branches may still be subject to some slight modifications; but since the connexion between the trunks and their roots has been fully determined the value of fossil trees has been much diminished; yet notwithstanding this diminution they still possess sufficient attractions to warrant a description whenever found, since they furnish us with indications of the extent of those dense old-world forests, which have played so important a part in the enterprise of the present generation. It is now well known that fossil trees exist in most of the coal measures of Lancashire and elsewhere. They have been found standing erect at Dixon Fold, near Manchester; in the Victoria Mine at Dukinfield, where their roots have been traced some 18 or 20 feet amongst the shale; and at Wolverhampton they are so numerous as to present the appearance of a fir wood cut down to the stumps. In the Newcastle coal field erect stems are found 150 feet below the present surface. They are also met with at Claycross, near Chesterfield; at Craigleith, near Edinburgh; at St. Etienne, near Lyons; and occasionally other forests, more ancient still, are indicated by the existence of tiers of stems each several yards beneath the upper trunks. A petrified forest occurs at Portland where the roots of the trees still remain in the vegetable soil, whilst their trunks pierce the limestone above. Other trees have been found erect on the coast of Northumberland. In the Derwent mines they are very abundant; and in all the coal measures of any extent they may always be met with upon due examination. Sir Charles Lyell notices their occurrence in Nova Scotia. He says, "The trunks are hollow cylinders, filled with sand and clay, and Calamites abound both here and at Pictou, affording proof that the trees have not been drifted from other localities, as was supposed by some of our earlier geologists." The determination of the real nature of such remains appears to be due to the late Mr. Bowman, of Manchester; for after a lengthened discussion on the fossil trees found at Dixon Fold, he concludes: 1. "That they were solid, hard-wooded trees." :- 2. "That they originally grew and died on the identical spots where they are now found interred." 3. "That they have become hollow from the decay of their wood by natural causes still in operation in tropical climates, and have been subsequently filled with foreign inorganic matter, precipitated as a sediment from water."-Trans. Manch. Geol. Society, Vol. I. pp. 112–140. Mr. Bowman's views were shared by E. W. Binney, Esq., F.R.S., also of Manchester, and by geologists generally, who further hold that the vegetation of the coal measures was aquatic, and that the water was probably salt. Mr. Binney also agrees with M. Adolphe Brogniart, and others, who have been led to conclude that Stigmariæ are in reality only the roots of Sigillaria, and he figures a specimen in the Memoirs of the Manchester Philosophical Society, Vol. VIII. p. 179, from the Dukinfield mine, which proves the point almost beyond dispute. More recently, however, all possibility of doubt has been removed" by the discovery at St. Helens, near Liverpool, in coal strata, of an upright trunk of a Sigillariæ, nine feet high, with its roots eight or nine feet in length, still attached in their natural position. These roots are undoubted Stigmaria ficoides, and the radicles, formerly considered as leaves, spread out in all directions to the extent of several feet."-(Mantell's Medals of Creation, Vol. I. pp. 143-4.) Sigillariæ, Stigmaris, Lepidodendra, Calamites, and Ferns, abound in the coal measures at Burnley. Large masses of black shale are often found, which when examined are wholly composed of leaves, fruit, &c., together with other remains of a former surface. In the mines near Dunoakshaw, a species of charcoal is plentifully mixed with the coal strata which still bears the impress of the woody vegetation from which it has evidently been formed. But by far the most interesting discovery in this locality was made in 1853, when a considerable number of fossil trees were found when excavating for the lower floors of Mr. Dixon's cotton mill, near the Hall Inn, Burnley. They were situated at a depth of about twenty-five feet from the surface of the present street, in the front of the cliff which overhangs the river Brun at this place. About fifteen fine trunks were met with by the workmen, in a space measuring 70 feet by 30, and lay in a direction from east to west in the excavation. The surrounding depositions of strata appear to have taken place uniformly, and most probably in still water, as the superincumbent shale bears every mark of having been undisturbed during its formation. The trunks are Sigillariæ of the usual species, and when found were in an upright position. The roots branched out from the bottom of several of the number, thus furnishing additional evidence that Stigmariæ are only the roots of Sigillaria, agreeably to the opinion of the eminent geologists previously quoted. The outside of each trunk was covered with a crust of fine coal, which has evidently been formed from the bark of the trees, and the interior is filled with a species of yellow sandstone. At the joints this is of a softer nature than the rest of the deposit, and stains the fingers like yellow ochre. Small portions of charcoal were also found mixed up with this yellow substance in some of the speciOne of the trunks measures fifteen inches in diameter; it divides into sections of about a foot in length, and the bark as usual is converted into pure coal. Another is twenty-four inches in diameter, and measures nearly eight feet in length. It had perforated hard gray shale for more mens. than six feet in thickness, and the remaining length was imbedded in soft sandstone. Several of the trunks had been destroyed by the workmen, and the fragments thrown into the river; the cavity of one of these measured eighteen inches in diameter, and was beautifully grooved throughout its whole length. A good sample of the trunks has been preserved in the Mechanics' Institution. It measures about twenty-one inches in diameter, and presents most of the peculiar features of this class of fossils. The finest specimen, however, was met with on the 5th of September. It consists of two portions, an upper and a lower, which were situated about a foot apart, and had evidently been broken and displaced by some violent motion of the surrounding strata. The upper portion is two feet three inches long, and the top and bottom diameters fourteen and seventeen inches respectively; the lower portion was not followed to its termination, but it commenced with a diameter of seventeen inches, and the grooves of both portions answered to each other in every particular. The top of the lower part was precisely of the same level as the bottom of the upper; thus proving that the dislocation must have taken place horizontally. This specimen is completely coated with a layer of fine bright coal, and has an indentation on one side which appears to have been produced by enormous pressure from without. This cavity is filled with hard gray shale, which leaves the surface of the tree when struck with an iron implement. On the western portion of the excavation other trunks were visible in the hard sandstone shale just above the coal measures, and numerous specimens of Calamites perforated the rock and shale in all directions. Many of these were coated over with a layer of fine coal, and bore a strong resemblance to the stalks of full grown sugar canes; others were even of still larger dimensions, indicating a period of most luxurious vegetation. One of the Stigmariæ exhibits a well defined pith of about three quarters of an inch in diameter, extending through its whole length; and another specimen branches off in two directions, very similar to those figured by Mr. Binney in the communication previously noticed. The swelling where this portion has been joined to the trunk is well defined, and from the fact of the roots being nearly horizontal and the trunks vertical, we are enabled to infer that the depression of the crust of the earth by which these remains were transferred from the surface to their present position was produced by forces comparatively uniform and without much violence. The bed upon which the roots rest is covered with the remains of vegetation. Seed-cones and Ferns occur in abundance, and several specimens of the latter have been procured, which exhibit not merely the usual symmetrically disposed fronds, but also the solid stems, from which the foliage branches off in all directions. One of the finest of these measures about twenty inches in length, by twelve in breadth, and appears to be the middle portion of a much larger plant. It is in the possession of Mr. Joseph Whitaker, who has preserved a considerable number of these impressions. The strata in which these remains have been found lie immediately above the Lancashire coal formation, and the Calamites correspond in character with those found perforating the white sandstone rock at Pickup Quarry, in Habergham Eaves, at a short distance from Burnley. Reckoning from the present surface of the street to where the fossil trees were situated we have a succession of common debris, fine sand, clay mixed with rounded pebbles, gray shale, soft sandstone, hard gray shalein which the fossils occur; and these are followed successively by shale of a still harder kind, bastard iron ore, and coal seams. Had the excavations proceeded farther many other trunks would no doubt have been disinterred, and hence "it is impossible to resist the conviction that the earth may contain innumerable forests entombed on the spots where they grew, many of which will ultimately be brought to light by the progress of discovery. So much information has been derived from these and similar discoveries relative to the formation of coal, that an opinion now generally prevails that the vegetation which produced the coal grew in broad and shallow lagoons or sheets of water, receiving at intervals deposits of silt and mud, the detritus of neighouring land. These streams were speedily filled up by the growth of a profusion of Stigmariæ, until, by the accumulation of mud, silt, sand, and the admixture of decayed vegetable matter, the lagoon was converted into a morass. A fresh vegetable growth now ensued of a somewhat different character, consisting of seedlike plants, Equiseta and Calamites, with here and there a larger tree. The spoils of these plants may have furnished materials for beds of peat and coal, resting on a base composed of the remains of Stigmariæ. The lagoon, or the morass, by the repeated subsidences, may have sunk |