forelands, in the vale of the Roe, exhibit the white limestone, with the marly argillaceous grit below, and the basalt above, uniformly consenting in their several planes, and rising towards the south-west in an angle of from five to six degrees..

The plane of the limestone, which dips, at Downhill, under the sea and the Bann, bassets off near the summit of Benbradagh, and the ascent of it is in a regular plane. Examined on the north, at Magilligan, it seems rising to the west; examined on the west, in the vale of the Roe, it seems rising to the south; the true elevation is in the diagonal of this double elevation, and is so great, that in a line, from the dip at the shore, to the basset on Benbradagh, in a distance of not more than twelve miles, it has ascended not less than 1200 feet.

On the eastern side of the river Bann, the line which has dipped under the sea-level at Downhill, appears again along the coast beyond Portrush; but there seems to have been a second sinking of the plane; for, the lime is again depressed under the level of the ocean, and does not reappear till near Bushmills.

These apparent discontinuations of the lime-stone may be owing to a curving of the strata; in some places this curving is evidently demonstrated by the direction of the stratification of the basalt and its other accompaniments; it is also possible, that the bed of the limestone may have been originally discontinued; that is to say, that the bed of shells, which furnished the materials for the couches of limestone, had not been supplied over the whole of the sands, previous to their consolidation. Nor let any one be surprised at this conjecture : let us consider how vast an accumulation of shells the tides supply to coasts and shores at this day; how vast a portion of the earth's surface, even at stupendous heights, has been formed from the exuviæ of marine animals; and at how unfathomed depths the vermes of the ocean are hourly extending their momentary labours and perennial spoils.*

On the top of Sliabh-gallan barytes is found near to the white limestone.

Of Basalt and its accompaniment.

Hic confidit aquis, hic procreat omnia flammis. LUCRETIUS.

The volcanist, the plutonist, and the neptunist, have each peculiar and contested theories: if we do not guard against all theory, at least we will abstain from all controversy.

Nevertheless, for sake of truth, some facts must be stated; and first I must observe that even in rocks of the primitive shistose formation, the tendency to a columnar figure is to be found, in those varieties, which contain the greatest proportion of silicious earth; and this is so true, that I have been frequently deceived, at first sight, by the surprising arrangement of a promontory, terminating in lofty columns of silicious shist.

Secondly, I have to state that silicious earth, as we see exemplified in pure quartz crystals, has an uniform tendency to produce regular figures, of which the hexagon, surmounted by truncated convexities, is the most common; but of which also, there are other varieties, extending to those of prismatic forms.

Thirdly, it is very immaterial to insist on the comparative height of the basalt hills or mountains: this speculation is lost in confusion; besides, what use in ascertaining these heights, which may either have been caused, insomuch as they have received an accumulation of more or less matter, at the commencement; or else, may have lost more or less, according to the durability of their materials? To lay open the interior of these strata is of much greater interest, and for this purpose I have accurately noted whenever a quarry or natural escarpment displayed any thing worthy of remark.

At the Carrick-rocks, and thence to Port-stewart, all the strata are a confused mixture of rude and shapeless basalt, with veins of red ochre and steatites; and with crystals of zeolite, some of them in masses of several pounds weight, extremely beautiful. To the

interior, and almost at the boundary of the county, some of the high quarries exhibit columnar basalt, whose pillars or prisms, are as accurate as those of the causeway; some of these prisms, in the upper strata, divaricate finely, like the striæ of a scallop shell.

At a quarry near Ballysally, the strata appear in the following

succession:

1. Oxide of basalt, with fragments and clay,

2. Stiff ochre, inclined to clay,

3. Species of fuller's earth, snuff-coloured,

4. Hard basalt,

5, Steatites, speckled like grey toadstone,

6. Basalt of unknown depth, intermixed with veins of purple and greenish toadstone, with rock tallow.

The dip of this quarry is to the north-west.

Feet.

1

2

2

4

3

I am now led to the examination of a line of coast, not only remarkable for interesting and magnificent points of view, but still more so for the abrupt and vertical presentation of the strata, composing the crust of the interior country.

In traversing the strand from the Bann westward, we find the stratifications of basalt submerged under the Bent-hills, and from the sandy beach farther inland, some eminences are discernible. There is one rock, which juts towards the sea, called the Castle; it is deserving of notice, because it appears to be a whin dyke, or gaw: according to the best of my observation, it penetrates through the whole mountain, re-appearing at the Largantea stream, which it crosses, and is there called Lady O'Kane's bridge.

I have not yet traced it farther. This rock consists of two walls, with a hollow between, and bears a great resemblance to that, described by Mr. St. Fond, on the coast of Scotland, which he took for the external walls of lava, which, after being cooled, served to conduct currents of liquid lava into the sea. This rock consists of very hard basalt, very black, and somewhat columnar, its prisms

being in their vertical position; veins, and even nodules of zeolite, both very minute, appear in some of its cavities.

The strata of ochre, trapp, steatites, and basalts, are alternated with regularity in many situations more to the south-west along this coast; yet in many also, they are intermixed in a more confused manner. In fact, these substances seem to have almost imperceptible degrees of approach and distinction. The ochre, with zeolite in spath, becomes coarse-grained, and approaches to trapp, whilst trapp, whose zeolite is not much concentrated, assumes a finer blend, and approaches to coarse basalt.

Again, another difference seems to consist in the state of the iron, which in the basalt is metallic, in the trapp oxidescent, and in the ochre oxide; steatite also, where the magnesia is in larger proportion, on account, perhaps, of imperfect blend, has not unfrequently its zeolite concentrated in spath, and thereby presents a resemblance to trapp. Its grain, however, is much softer, the silica being overpowered by the magnesia; it leaves a polish, when pared with the knife, whilst that of the trapp is gritty and granular.

It appears, therefore, that in places, where the steatite has not any crystals of zeolite, the relatives of this latter substance may be found, under the character of soap-rock, coarse and flinty veins of steatite, and calcareous ochre.

It appears also, that basalt, even when pure, through superabundance of silica, may sometimes contain conic and wedged-shaped casts of chalcedony, of which I have many specimens; but of all these substances respectively, it is perhaps affirmable, that the less the abstraction of their silica out of the mass, in other words, the less it is concentrated into crystalline matter, so much the finer is the grain of that mass, and so much the more smooth and consistent its blend. I shall only add one more remark at this place. It is the philosopher in the cabinet, who imagines boundary lines of distinction between one fossil and another. Nature, in her great elaboratory, passes, by imperceptible transition, from one defined production to its

next ally. This is particularly true of basalt. I subjoin an account of the succession of strata, under which the grotto at Down-hill is formed.

1. Two undistinguishable strata of very confused basalt, partly columnar, more generally shivered, resting on a base of ochre, graduating into trapp,

2. Red ochre, somewhat branching into veins,

3. Small tables of basalt, mixed and alternated with earthy trapp,

4. Ochre,

5. Trapp, with basalt veins of ochreous and zeolitic matter, with masses of hard table-basalt,

Feet.

60

1

70

1

14

6. Trapp, with veins and strata of zeolite, blending at bottom into soft, coarse, friable basalt,

6

7. Trapp, indistinctly blended with basalt, changing by shades, the midmost tabular,

4

10

8. Rude, coarse basalt, with blotches and blebs of zeolite, 9. Black basalt, involving masses of trapp,

178

The altitude of the rock, on which stands the temple, and which overjuts its base, is 168 feet.

In descending by the zig-zag path, the order of the strata is as follows:

1. Soil and rubble.

2. Amorphous basalt.

3. Indurated and coarse rock tallow or soap-stone.

4. Steatites.

5. Basalt.

6. Trapp.

7. Tabular basalt.

8. Confused basalt with trapp, abounding in crystals of zeolite,

and in soap-stone.

9. Trapp.

N