But when the coast changes its direction, this coincidence ceases, and the façade (that is the vertical section of the coast) losing its east and west course, its strata must appear to ascend towards the point it turns to; therefore the strata at Portmoon, and along the north-east side of the promontory, should ascend obliquely along the façades, as they actually do.

First Stratum.

The stratum I commence with forms the whole façade, from its first appearance until it reaches the promontory; it consists of massive pillars rather rude, and about sixty feet long, its course for half a mile (as I have stated) seems horizontal; but on the face of the promontory it ascends, and continues to rise uniformly until it reaches the summit, which it lines as far as Portmoon, on the south side of which it loses some of its thickness, then suddenly disappears and vanishes from that façade, receding westward in the form of a stony ridge, aud is seen no more.

Second Stratum.

The stratum upon which the preceding rests, is red as brick, and about nine feet thick; it appears in spots, and patches just above high water mark, so long as the incumbent stratum continues horizontal; but when that rises obliquely, the second ascends with it; it is now completely displayed, and having supported the preceding in its course to the summit, vanishes with it and is seen no

more

These ochreous matters, so common in all basaltic countries, according to Mr. F. St. Fond's opinion, were once pure basalt, but have undergone some chemical process of nature we are unacquainted with, by which their colour has been changed.

Third Stratum.

The next stratum is the last of those composing the promontory which appears beyond it; for so long as the first and second continue their horizontal course towards Bengore, this third accompanies them, shewing its upper surface between high and low water mark; but when it ascends along with the others across the façades, it displays its whole thickness, above fifty feet.

This stratum is of that variety of basalt, I have on different occa

sions distinguished by the name irregular prismatic: it resembles the columnar basalt in grain, but differs from it totally in principle of interual construction; for its prisms are small, not articulated, and indifferent as to the position of their axes, which is perpetually changing.

The irregular prismatic basalt accompanies the columnar in most countries, as at Pont du Baume, at Trezza, at Bolsena in the Sound of Mull, and at Staffa. In Antrim, it is very common; and here is a striking resemblance between the rock crowning the celebrated columns at Staffa, and a stratum covering a very neat colonnade at Craigahullur, near Portrush.

This stratum is scolloped off irregularly from the point where it becomes superficial, until it completely disappears; a thin stripe of its lower edge alone is ever resumed again.

Fourth Stratum.

The next three strata will require only very short descriptions. The fourth is about seven feet thick, entirely columnar, the pillars small, but not neat; they appear very white from a thick covering of Byssus saxatilis, which shews a great predilection for this

stratum.

Fifth Stratum.

This stratum is ochreous, and more of a slate colour than any of the other red strata; as it is friable, it soon acquires a grassy coat, through which it is only in spots that it shews its proper colour; it is about eight feet thick.

Sixth Stratum.

This stratum is composed of rude massive pillars so coarsely formed, that on the least abatement of perpendicularity the columnar form can scarcely be traced. This stratum is about ten feet thick: it forms the vertex of the beautiful conical island Beanyn Daana.

These last strata, though they have nothing very remarkable in themselves, nor contribute much to the beauty of the façade, yet exhibit one of the most important facts I am acquainted with in natural history, and which, when attentively considered, throws

much light on the nature of the operations performed upon our globe since its consolidation, and leads us irresistibly to conclusions extraordinary and unexpected.

The fourth, fifth, and sixth strata reach the top of the precipice, and vanish together at the waterfall in the north-west corner of Portmoon. When they come to the surface, they turn inland to the westward in long stony ridges; these obstruct the course of the waters in their descent along the inclined plane, formed by the surface of the promontory, and throw them over the precipice, in a cascade highly beautiful after rain.

On the façades to the north-west not a trace of them appears, these being entirely formed by the lower strata, which I have not yet noticed; but at the distance of a mile, at the great depression (already mentioned), the fourth, fifth, and sixth strata, with a narrow stripe of the third, suddenly appear, in their regular posts, their proper order, and with all the characteristic marks peculiar to each separate stratum,

In the interval between the depression at Pleskin, and the Giant's Causeway (about a mile), these three strata often appear in a desultory way on the summit of the precipice, wherever it is of sufficient height to receive them, always preserving their usual thickness, their characters, and their order; so that a person master of the order I am detailing, as he approaches a rising point of the precipice, can tell its strata, and their order, before he is near enough to distinguish them.

Seventh Stratum.

The rude and massive pillars of the sixth stratum pass into the neater, and much longer columns of the seventh, without interrupting the solidity or continuity of the material; exactly as a downheld hand appears to separate into fingers. The thickness of this stratum, that is the length of the pillars of which it is formed, is fifty-four feet; and in its passage across the face of the precipice, displays more beautiful colonnades than any of the others.

This seventh stratum emerges from the beach immediately behind the south-east point of Portmoon, and where it first shews itself in that bay, has its lower edge raised only a few feet above the water; it forms the upper frustum of the larger of the two conical islands,

ascends obliquely along the face of Portmoon, and continues to rise until it composes the upper range in the beautiful façade, properly called Bengore Head. This is probably the most magnificent of all, its convexity towards the sea producing a fine effect. The lower edge of this stratum, that is the line forming the base of its pillars, has here, as at Pleskin, attained the height of three hundred feet above the water.

This seventh stratum, like those above it, also suffers an interruption; for after having exhibited itself to such great advantage at Bengore, the extreme northern point of the promontory lowers, and this stratum disappears for about one-third of a mile; as the promontory rises, it is resumed again in great beauty at Pleskin, and is interrupted no more; we scarcely ever lose sight of it until we reach Port Noffer (the next bay to the Causeway); here, for want of perpendicularity it is little seen, and is finally lost over the Causeway, we know not well how.

Eighth Stratum.

The next stratum is of the same variety of basalt with the third, that is, irregular prismatic; it is fifty-four feet thick. Where it emerges at the south-east corner of Portmoon, it is quite accessible by land, and affords the best opportunity I know for examining this species of basalt, as it is there very neat.

There is little more of this stratum seen in the façade of Portmoon for want of perpendicularity, but it forms the lower frustum of the great conical island Beanyn Daana, and the whole of the smaller, except the base; it is well displayed over the remainder of the precipice, it forms the intermediate stratum between the magnificent colonnades at both Bengore and Pleskin, and finally is lost just over the Giant's Causeway. Large globular fragments have fallen from it, and are scattered about the Causeway.

Ninth Stratum.

This stratum is forty-four feet thick, that being the exact length of the neat pillars composing it; at its emersion it forms the bases of the two conical islands in Portmoon, and is no more seen in that bay; but immediately to the northward it begins to shew itself in colonnades and groups, some of them resembling castles and

towers,

It ascends along the precipice obliquely, like those above it, forms the lower range at Bengore and Pleskin, from which last it dips to the westward regularly, composes the group at Port Noffer, called the Organs; seen from the Causeway, and finally at its immersion, or ins tersection with the plane of the sea, it forms the beautiful assemblage of neat pillars, so long distinguished by the name of the Giant's Causeway.

At these two intersections, each of them accessible by fand and water, the prisms exactly resemble each other in grain, size, and neatness; the interval between them is full two miles, through great part of which this stratum is displayed at different heights; it culminates between Pleskin and Bengore, with its lower edge more than two hundred feet above the water.

We see now what a diminutive portion of our vast basaltic mass has, until lately, monopolized the attention of the curious; and even after it was discovered that we had many other, and much finer collections of pillars on the same promontory, it never occurred, to those who were preparing to give accounts of them to the public, to examine whether these were mere desultory groups, or detached parts of a grand and regular whole, which a more comprehensive view of the subject would soon have laid open to them.

Tenth Stratum.

The stratum upon which the pillars of the preceding rest, is ochreous, red as minium, and about twenty feet thick; it is scarcely seen at Portmoon, a patch alone of its surface being distinguishable under water at low tide; but immediately to the northward it shews itself, and from its bright colour makes a conspicuous figure across the face of the precipice in a course of more than a mile and half; its last appearance to the westward is at Rovinvalley, the opposite point of the bay from the Giant's Causeway, from which we have a good view of it. The final dip and immersion of this tenth stratum, as well as its emersion, are lost for want of perpendicularity.

The six remaining strata are all similar in material, but differing much from each other in thickness; they are all of that description called tabular basalt, sometimes shewing a faint disposition to assume a columnar form at their edges, and always separated from each other by ochreous layers.

These six strata are not so perfectly distinct as those above them,