Cheshire side. In other cases the coal appears to thin out as it approaches the grit hills. Denudation as well as elevation seems to have taken place, and the latter in some cases after the deposit of the red sandstone. In this Pottery coalfield the numerous faults run, more or less, at right angles with the lines of elevation, and from southerly falls it has fortunately happened that the seams are more widely attainable than they would have been without their occurrence. Some of the (geologically speaking) highest beds of coal are worked about 700 feet below the sea-level; others, upon Axedge, exist 1000 feet above it, and these appear to have been the first deposits. In this last narrow trough the coal strata seem bare and dissected to the naked eye, being imperfectly covered with herbage and reposing upon equally bare and jutting rocks of grit. The fossil Aviculo-pecten only appears to occur in the lowest strata to the east, whilst the Microconchus carbonarius is common in the upper. The coal-yielding beds may be said to consist of an upper and lower series in the principal coal-field; no known band of clay ironstone exists in the latter; though, in the present mineral-seeking times, an important bed of earthy hæmatite has been found very low in the series. The ichthyolites, to be mentioned, occur principally in the upper measures, as they are commonly found in ironstone or its shales. Some layers seem to consist almost entirely of these fish-remains with coprolites, but the former extremely fragmentary. The ironstone, No. 4 from the surface, called the bassy mine, is a remarkable bed, and may be identified through the whole area of the upper measures, being raised in enormous blocks, marked on their surface by great impressions of Stigmaria, and by flattened Uniones.

One or two dykes of greenstone occur in the bunter sandstone, to the south of the Pottery coal-field, and metamorphosed grits at Mow Cop (Sax. or as well Brit.) in the westerly ridge, and at Fenton Park; the second greenish in colour and enclosing round nodules of hæmatite. The drifts or gravels of North Staffordshire appear to be of, at least, four or five kinds: the northern drift with fragments of Venerupis and other shells; a second gravel with fragments of whitish chalkflints and sometimes Ananchytes; both these gravels occurring in the southern lower lands, but the first rather to the east and the second to the west; next the gravels of the bunter sandstone, often forming hills of a good elevation and composed mostly of characteristic red quartz pebbles, marked by cloudy white spots, greenstone, curious decaying agates, mountain limestone, and lower Silurian pieces, as well as white quartz and black jasper, also grit and coal. On the area of the coal-fields a coarse gravel of less rounded pieces occurs, mountain limestone, grit, and greenstone being the constituents; also, in the surface clays, blocks or boulders of greenstone or porphyry, red and white granite, and grit, more or less rounded, and sometimes weighing several tons. From the sides of some of these valleys, of the bunter sandstone formation, the rocks often jut out in a horizontal direction, giving the idea that such valleys must have been formed by the action of water. The millstone grit often presents smooth or polished surfaces (slickensides ?), but this even in the quarry.

Coal-plants, as Calamites, are frequent in the Permian. In the coal strata the authors lately measured the but or trunk of a Sigillaria more than a yard across, its roots being given off exactly in the cruciform way, and bifurcating at equal distances of about a foot. When broken, these root-trunks presented an impression very like the leaf of a Blechnum, but which they suppose is due to the compressed processes given off from a central fibrous rod. They also appear to be compound. It is also curious how many of the trunks of these trees contain other vegetable remains in the clayey sandstone of their interior, such as large Calamites. Certain heart-shaped bodies abound in the ironstone, with the mark of the insertion of a hollow stem above: these the authors think may be the roots of Calamites or similar plants, the cylindrical stems which seem to belong to them ending rather obtusely, smooth, unjointed, and often containing pyrites of zinc. Then again are found convex, hemispherical bodies, with a tubercular surface, and cellular within; smaller ones occurring gregariously. Circular or reniform markings occur in the shale of the bassy mine, above alluded to, presenting somewhat the appearance of a peltate or cordate aquatic leaf; but they go through several laminae of shale. There are also large grass-like leaves (Poacites ?), a large and a small Ulodendron, two Haloniæ, fine Asterophyllites and Sphenophylla, with other commoner fossils.

The large-leaved Neuropteris cordata, a Sphenopteris with a fucus-like leaf of large size, and another quite filiform, have also been found by the authors. The following are the more interesting ichthyic remains, as far as they can identify them by Agassiz:

Dipterus. Part of the head, and plates.

Palæoniscus. Scales, and a portion of the fish (ornatissimus, Duvernoyü).
Gyrolepis. The hinder half of the fish.

Calacanthus. Scales and fins.

Platysomus. Fragments of the fish, and numerous scales.

Rhizodus. Most of the fish, and the sharp- and curve-pointed striated teeth. Holoptychius. Very large plates and parts of the fish, the upper jaw with double rows of large and small striated teeth.

Ctenodus. Two or three pieces.

Megalichthys. The plates are very common as well as the teeth, a cranial plate 6 inches wide, vertebræ 2 inches; also the jaw with teeth, and the tail found by Mr. Ward.

Saurichthys. Teeth swollen at the bottom, striated, and more curved than the commoner teeth of the last genus.

Ctenacanthus. The armature is not rare, a fine and perfect one found by Mr.
Ward.

Hybodus. The teeth with crumpled base, one large middle cusp, and two or three side ones on each side.

Diplodus. The supposed teeth are very common, with three or more fangs. A tooth straight, compressed, lanceolato-conical, 14 inch in length: if it belongs to Diplodus, the size must be unusual.

Ctenoptychius. The beautiful teeth are not very rare; there appears to be numerous species (apicalis, pectinatus, and denticulatus). A tooth of, apparently, a new genus, very small, with truncate base and eight or more clustering slender-pointed cusps at irregular altitudes.

Petalodus. Remains of several species.

Helodus simplex. Base of teeth excavated, the summit simple and blunt. Pleuracanthus. These curious armatures are rare, but we have found one very perfect in cannel; some imperfect specimens have the central part compressed, and the processes less marked.

Onchus (?). These sword-shaped rays or spines, moulded on the concave edge, are extremely common.

Orthacanthus. These formidable weapons are frequent, and very long, a foot or more; they are difficult to get out unbroken. A smaller and more conical armature without term.

Leptacanthus.

Gyracanthus. Common, and of two or more species.

Besides the above, numerous fragments have been collected, of more or less interest, some considered to be novelties by Sir P. Egerton: also nine or ten species of the bivalve Anthracosia. The authors are rather reluctant to give names, but the following epithets may almost suffice to distinguish them:-A. triangularis, dactylus, unio, anodon, retrocompressa, alata, nucula, oblonga. costata.

The hillocks raised by annelides, ripple-marks, and very large impressions of bivalves of two or three forms occur in the flagstone of the millstone grit; also transverse sections of plants, either round or obliquely indicated, as if blown down.

From the mountain limestone, occupying about 40 square miles, more than 200 species of Mollusca have been collected, but this principally by a friend, Mr. Carrington, a village schoolmaster. Amongst the more interesting species are Conularia, species of Pteronites, Pleurorhynchus; rare Pleurotomariæ, Goniatites, and Nautili; the Orth. paradoxus, or one similar to that from Ireland figured by Sowerby; abundance of corals; many pelvic plates of Crinoida, and about ten species of Trilobites, all small, and rarely entire. The latter most abound with the fry of Terebratulæ. Mr. Carrington has also found traces of fish. The limestone shale has some obscure impressions of bivalves. With respect to vegetable remains, little has been discovered: certain supposed stems or twigs, of an enamelled appearance, are siliceous when chemically examined; and the received opinion

seems to be that other curious algæform markings of the limestone are mere infiltrations.

On the Chronology of the Trap Rocks of Scotland. By A. GEIKIE, F.G.S. The points to be proved were-first, that there is sufficient abundance of felspathic matter in the grits of the Silurian region of the Lammermoors to warrant the inference that felspathic matter was either ejected during the formation of these grits, or already existed in considerable abundance on the surface. Second, that the Silurians of the Lammermoors are traversed by numerous dykes of felstone, some of which may have been ejected during a contortion of the Lower Silurian previous to the deposition of the Upper, Third, that the Old Red Sandstone period was marked by powerful and long-continued volcanic activity, in several centres, as the Sidlaws, the Ochils, the Pentlands, and part of the hills of Lanark. Fourth, that the Carboniferous period was characterized by the especial abundance and activity of its volcanic centres-so much so that there is not a well-defined zone of carboniferous beds which does not, at some part of the Lothians, display its intercalated sheets of ash or greenstone; but that these eruptions were markedly local alike in their extent and in the character of the erupted material. Fifth, that after the carboniferous series, there is a great gap in the chronology of the Scottish traprocks, the next traces of subterranean movement being discernible in the lias of Skye; but that contemporaneous igneous rocks are not found until towards the top of the middle oolite, where among estuarine limestones and shales, there occur in Skye and adjacent islands enormous sheets of greenstone and basalt. Sixth, that, as upper secondary rocks have still to be determined in the Hebrides, we have, at present, to pass from the oolitic traps of Skye to the basalts and ashes of Mull, which, as shown by their associated fossils, are tertiary, and probably miocene. Lastly, that the later basalts and ashes of Arthur's Seat ought probably to be referred to the later secondary, or older tertiary period.

On Canadian Caverns. By GEORGE D. GIBB, M.D., M.A., F.G.S.,

Member of the Canadian Institute.

The prominent feature of a large portion of the Province of Canada is the presence of various limestone rocks belonging to the Silurian formations. Until lately, the éxistence of caverns in these rocks, as well as in those lying subjacent, namely, the Laurentian of Sir William Logan, was almost unknown; but owing to the labours of the Canadian Geological Survey, and of several private individuals, a number have been discovered, at distances remote from one another, which it is the object of the present memoir to notice.

For convenience of description, these caverns are divided into two classes; the first comprises those which are at the present time washed by the waters of lakes, seas, and rivers, including arched, perforated, flowerpot, and pillared rocks, which have at one time formed the boundaries or walls of caverns, and all of them unquestionably the result of aqueous action. The second comprises caverns and subterranean passages, which are situated on dry land, and, so far as we know, not attributable to the same cause in their origin as in the first, or at least not applied in the same manner.

In the first class are included

1. Caverns in the shores of the Magdalen Islands.

2. Caverns and arched rocks at Percé, Gaspe.

3. Gothic arched recesses, Gaspe Bay.

4. The "Old Woman," or Flowerpot Rock, at Cape Gaspe.

5. Little river caverns, Bay of Chaleur.

6. Arched and flowerpot rocks of the Mingan Islands.

7. Pillar sandstones, north coast of Gaspe.

8. Niagara Caverns.

9. Flowerpot Island, Lake Huron.

10. Perforations and caverns of Michilimacinac, Lake Huron.

11. The Pictured Rocks, Lake Superior.

12. St. Ignatius Caverns, Lake Superior.

13. Pilasters of Mammelles, Lake Superior.

14. Thunder Mountain and Paté Island pilasters, Lake Superior.

In the second class are

15. The Steinhauer Cavern, Labrador.

16. The basaltic caverns of Henley Island.

17. Empty basaltic dykes of Mecattina.

18. Bigsby's Cavern, Murray Bay.

19. Bouchette's Cavern, Kildare.

20. Gibb's Cavern, Montreal.

21. Probable caverns at Chatham, on the Ottawa.

22. Colquhoun's Cavern, Lanark.

23. Quartz Cavern, Leeds.

24. Probable caverns at Kingston, Lake Ontario. 25. Mono Cavern.

26. Eramosa Cavern.

27. Cavern in the Bass Islands, Lake Erie.

28. Subterranean passages in the Great Manitoulin Island, Lake Huron. 29. Murray's Cavern and Subterranean River, Ottawa.

30. Probable caverns in Iron Island, Lake Nipissing.

All these are particularly described in the author's memoir. The majority of those in the first class are on a level with the water, whilst the remainder are elevated above, varying from a few to upwards of 60 feet. In the second class the level varies, but nearly all are above that of the sea, and none penetrate the earth to a considerable depth; but this may be found to be otherwise as the explorations are continued. In none have animal remains been found excepting in one instance, and they were discovered loose and not imbedded in stalagmite; and, so far as I am aware, not a single object, such as a flint arrow-head or spear, used by the ancient inhabitants of the country, has been observed: this part of the inquiry has still to be worked out, as many of the caverns have been but very partially explored. Interesting discoveries are yet hoped for in the district of country in which exist the huge caverns of Mono and Eramosa, in the Niagara limestone rocks of the Upper Silurian formation. A correct account of the geological formation in which the caverns are found is given; and, taking the two classes of caverns together as representing thirty distinct series of cavernous objects, 1 is found in the New Red Sandstone; 2 in the Devonian or Old Red; 7 in the limestones of the Upper, 4 in those of the Middle, and 6 in those of the Lower Silurian formation; 3 in the Huronian rocks of Sir William Logan, and 7 in the Laurentian rocks of the same geologist. In the last of these they are present in the interstratified bands of crystalline limestone, characteristic of this formation in Canada.

With a few exceptions, nearly all occur in limestone rocks, and their origin has depended upon various causes. The first fourteen, which compose the first division, are the results of aqueous action, as their situation, present condition, and general description clearly prove. Perhaps an exception might be taken to the formation of pilasters and Gothic arched recesses, which are more properly attributable to atmospheric influences. Volcanic agency has given origin to the basaltic dykes of Mecattina, the basalt of Henley Island, Bouchette's and Gibb's caverns. The same cause has most likely influenced the subterranean passages of Manitoulin and Murray's cavern.

On the other hand, Bigsby's cavern, Colquhoun's, the Mono and Eramosa, and Bass Islands caverns, were formed by some other agency, in which a slow disintegration of the rocks has occurred from chemical or other causes, and the soluble particles have been removed by the influence of water, entering by percolation from above, or between the neighbouring layers of rock. The origin of the quartz cavern was by the explosion of a pyritous vein.

The bones found in Colquhoun's cavern were supposed to be those of a species of deer, and occurred chiefly in a heap, although many others were scattered among the debris on the floor. They were transmitted to Dr. Buckland for examination and description some thirty years ago, but no account of them ever appeared,

On some Basaltic Formations in Northumberland.

By WILLIAM SYDNEY GIBSON, M.A., F.S.A., F.G.S.

The basaltic formations in Northumberland not only contribute to the picturesque outline and the wildness of much of its scenery, but present some remarkable features in their structure and in the manner of their association with other rocks.

A range of basalt traverses the county from south-west to north-east, in a ridge or belt of varying and often considerable height, but inconsiderable breadth, entering Northumberland near the Cumbrian border. This ridge first begins in the dale or "forest" of the Lune, and sweeps round the great western escarpment of the limestone ranges of Cross-Fell and Tynedale-Fell; then, cnrving towards Thirlwall on the border of Cumberland, it runs from thence north-eastward with bold escarpments towards the north, and crossing the North Tyne, extends to the sea-coast at Howick; it then rises at Bamburgh, and after a tortuous course to the north-west, ends in the low range of hills called the Kyloe Crags. The rocky group or "seventeen sister-satellites" of Farne are a seaward prolongation of the great basaltic range. Basaltic veins or dykes also run towards the coast of the county (as at Holy Island, Beadnell, andTynemouth), and seem to have a direction transverse to the great ridge.

In the western part of the county, the basaltic crags are associated with that wonderful monument of Roman occupation-the Great Wall, its builders having availed themselves of the precipitous ridges, and carried the wall above many a bold escarpment of basaltic rock. A crest of this formation near Wall-town, which was formerly crowned by a Roman Mile-Castle of the Wall, is 800 feet above the sea-level; and at a Roman camp to the westward, known as Sewingsheles, the summit attains the height of 960 feet. In this wild district, once adjacent to populous Roman Stations, but where now only the moor-fowl dwells among the heather of neighbouring wastes, are the lonely sheets of water known as the Northumberland Lakes, one of which, called Crag Lough, lies at the foot of the basaltic cliffs.

In the northern part of the county the basalt likewise forms rocky masses of considerable height, often precipitous on their western side, and culminating at one place at 570 feet above the level of the sea. Many of these eminences have been chosen for the site of Castles, as at Bamburgh, Holy Island and Dunstanburgh, where the caverned rocks of columnar basalt rise 100 feet above the surging waves. At Bamburgh (an important citadel from days of Saxon royalty) the draw-well of the fortress has been sunk through 75 feet of basaltic rock, and through a like thickness of the fine-grained reddish tinted sandstone on which it rests. On the rocky islets of Farne the basalt even exceeds this thickness.

The isolated, metamorphic and dislocated condition of the beds of sandstone, limestone, and shale on some of the Farne islands, seems to indicate that the basalt flowed in its igneous state over these lower groups of the limestone series. On the coast at Howick, a little to the south, the basalt appears in the form of dykes which intersect the cliffs of carboniferous limestone, shale and sandstone. A formation of basalt, which seems to have overflowed after the deposit of this group, overlies it. Elsewhere in Northumberland a stratiform basalt is found associated with the carboniferous rocks, and in some localities is interstratified with them; thus, a bold columnar cliff called Ratcheugh Crag, near Alnwick, one of the range of basaltic eminences which run inland from the coast at Dunstanburgh, is capped with the carboniferous limestone. Another basaltic eminence between Alnwick and the coast rests on beds of blue limestone and metamorphic shales, which in some localities Mr. George Tate of Alnwick, F.G.S., a diligent and able naturalist, found to have been converted into a porcelain jasper, and where in direct contact with the basalt, into a black mineral of conchoidal fracture. At Ratcheugh some of the limestones above the basalt have been changed into granular marble.

In some localities of this carboniferous limestone district, as at Howick and Bamburgh and on the Farne, the rocks have been disturbed by an eruption of basalt; and it occurs both as an injected dyke and an overflowing lava, and seems to indicate successive volcanic outbursts during as well as subsequent to the era of those formations.