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CHAPTER V.

Divisions of the Strata of the Modern Epoch-Taragmite series-Akumite series-Phanerite series-Basement Bed-Boulder Clay-Boulder Gravel-Sand-Proofs of Motion-Organisms.

IN the last chapter I referred to several attempts to group the modern strata, which, apparently, have arisen as deductions from adopted opinions, rather than expressions of results from observed phenomena. In the classifications and terminology I am to adopt at present, a considerable reluctance has been experienced in abandoning the use of employed terms, particularly those of my respected friend Sir Charles Lyell. But these did not enable me to represent with sufficient distinctness the conclusions at which I had arrived, without a great risk of confounding them with others of a very different character, deduced from observations in more distant localities.

In the Edinburgh basin the modern strata seem capable of classification into three groups. The first or TARAGMITE SERIES, have been formed subsequently to the dressings, and, where present, repose upon them. They seem to have been formed when violent aqueous movements were taking place, and probably at a period when the state of our island was widely different from the present.* Although extensively distributed in Scotland, they have peculiar characters in different districts. Thus they are dark coloured on the coal-measures, red on the

* Mr Bald of Alloa, whose intelligence, as a Mining Engineer, is so generally recognised, has stated:-"I have had very frequent opportunities of seeing this kind of cover laid open from the surface to the rock on which it rests, and have found it in thickness from a few inches to 160 feet, and have always remarked, that though it contained boulder-stones, and gravel of almost every kind of rock, and detached angular fragments of the adjoining rock stratifica tion, I never had observed a single instance of an organic remain of any kind in it."-Wern. Mem. iv. p. 59.

old red sandstone, and grey in some of the primary districts. The contents are derived from the neighbouring rocks, with occasionally masses transported from a considerable distance, but usually belonging to the river basin. The second or AKUMITE SERIES is chiefly characterised by its laminated clays and sands, and indicates the assorting power of water under circumstances of comparative tranquillity. It contains organic remains, many of which still live in the neighbourhood. It may be looked for wherever brick kilns have been erected. The PHANERITE SERIES* consists of deposits produced by causes in ordinary operation, and respecting the circumstances under which they have been produced little obscurity prevails.

The question, what has become of the detrital matter generated during those excavations and abrasions which have already been considered in detail, is one of great importance. That the period was one of disturbance will not admit of a doubt, and in passing to a state of tranquillity it may now be asked were the loose materials distributed according to any order? To answer this question satisfactorily, will require us to determine what were the abraded materials which first rested on the dressed surface, and served as a fundamental or supporting stratum to the subsequent deposits.

1. BASEMENT BED.-For several examples of dressed surfaces which have been noticed, the material termed boulder-clay has been stated as the cover. This, however, is not the oldest member of the Taragmite series, as several instances have occurred which indicate the existence and distribution of loose materials previous to the rocks being overlaid by this their more ordinary covering. Thus, at the sandstone quarry of Redhall, a large deposit of stratified sand and gravel was observed a few years ago resting on the bituminous shale which covered the sand

* Those who consider it necessary to trace the origin of these terms, which we have devised in order to avoid the employment of hypothetical ones, or such as have been used with different meanings, may be directed for Taragmite to Tagayua disturbance, for Akumite to axvuos tranquil, and for Phanerite to pavegos evident. At the same time it is freely admitted, that "when once the thing is known, inquiries into the etymology of the word expressing it, are rather curious than useful."-(Hailes.)

stone, and extending throughout a considerable space near to the place where the engine-house has since been erected. The relations of this mass of sand and gravel could not be determined on the north and west, although evidently resting in a hollow; but on the south it was observed reposing on the sandstone for several yards, and covered by the boulder-clay which rested on the rock in the other parts of the quarry. The clay seemed to have flowed over it quietly, or to have been deposited on it without occasioning any particular contortions in the sand. In Hailes Quarry, to the westward, a deposit of sand occurred under the clay and in a trough of the rock, commingled, however, with some slips of the clay and of peat, which rendered the phenomena somewhat obscure.

In executing the improvements on the Queensferry Road to the westward of Craigleith Quarry, several examples occurred of the clay resting on sand, and to some extent also stratified therewith. A similar case occurred in the tirring at the southeast corner of the quarry. In the excavations for the foundation of the houses on the north side of Charlotte Place, to the west of St George's Church, from two to three feet of angular fragments, or shivers of bituminous shale, rested immediately on the fixed strata of the same material. The boulder-clay rested on the shivers, and seemed to have been in motion from west to east, and at one place had squeezed a process of the shivers into its substance, so as to be above, below, and in front of the projection. In some places the shivers were slightly covered with sand interposed between them and the clay.

When the foundation for the gasometer on the south side of the Water of Leith, at Tanfield, was being dug, a similar display of the junction of the shivers with boulder-clay presented itself. In this case and the former, the shivers sometimes reached the length of three or four inches. Here they consisted of a light-coloured somewhat indurated slate-clay, occasionally arenaceous. This mass of fragments, forming a bed from two to three feet in thickness, rested on the edges or strata of apparently similar materials, and were covered by the boulderclay. There was no transition between the one and the other,

the line of junction being abrupt. At one place a tongue or spit of shivers ascended into the till, of nearly six feet in length, rising at about 20° and pointing eastward. See Fig. 1.

d Trap dyke, levelled by abrasion along with the shale on each side.

These observed examples, and perhaps others may soon occur in the neighbourhood, seem to intimate that some time elapsed between the dressings of the rocks and their being covered by the boulder-clay, and that immediately subsequent to the dressings, disintegration of the rocks took place, furnishing the sand and gravel of Redhall and Hailes, and the shivers at the two last-mentioned places. We have not as yet the means of determining to what extent Scotland has been overspread by this earliest member of the Taragmite series. We first observed it many years ago at the Bay of Nigg near Aberdeen, where we have had the pleasure of pointing it out to Agassiz and Buckland, Lyell, and Home. It there consists of sand and gravel resting on gneiss and covered by boulder-clay of a greyish colour. This in its turn is covered by gravel, in which we have found boulders of a boulder-clay, of a red colour, similar to the more southern Kincardine beds.

Mr Milne Home, in the Memoir already referred to, subsequently adduced several examples, the relation of which we shall here quote:

"This deposit has been observed in several parts of the district, covering the edges of the stratified rocks. It prevails ex

tensively in that part of the district situated between Dalkeith and Cowpits. Some years ago, coal was worked at the latter place; and in sinking various pits through the superficial clay and gravel, a bed of sand lying immediately on the rocks, was invariably passed through, which, being full of water, occasioned great practical difficulties, and even risks, to the work-people. A few months ago, a similar bed of sand was met with on the Duke of Buccleuch's estate, near Dalkeith, in sinking an enginepit to work the coal. The pit had been formed through the boulder-clay, on reaching the bottom of which a bed of sand was encountered, which suddenly gave way, and laid the building in ruins. It was found necessary to form a new pit at a different place,-about the level to which this particular deposit reaches, which appears to be about two hundred feet above the sea. At the place where the first pit was put down, the sand was nine feet thick, and between it and the rocks there was a mixture of sand and fine gravel, seven feet thick. "At Joppa likewise (at the east end of the village, near the shore), the clay is separated from the subjacent coal-measures, by a bed of sand five or six feet thick. This sand-bed was found in the borings made for a particular coal-seam there, called the splint coal. The sand-bed covered this seam ;-fragments of the coal were found in the sand, to the distance of ten yards from the crop or outburst of the seam. It is not unimportant to observe that, in the sand-bed, these fragments were all situated to the west of the coal-seam. Some fragments were also found at the bottom of the superjacent boulder-clay ;these were situated mostly to the east of the coal-seam.

"At Leith, and in the manufactory lately occupied by Mr Burstall, a well was sunk through the boulder-clay forty-five feet. A bed of sand and fine gravel was then reached, from which water immediately gushed up,-shewing that the bed was probably of considerable extent."

There is reason to suspect the want of continuity of this oldest stratum, which consists, at places not very remote, of very dissimilar materials. In the Joppa example above referred to by Mr Home, we see at present on the beach, as for