In some parts of the world, there are rocks which are not stratified and arranged like those which I described to you some time ago, but are laid over the surfaces, and in the crevices of others in this manner:— In this cut, a, a, a, are intended to represent the stratified rocks, and b, b, b, the others, which from their position are sometimes called overlying rocks, and they mostly consist of a substance called basalt, which is nearly black and very hard, and occasionally with white and coloured minerals imbedded in it. There are two states in which it is found; in one, it occurs in masses without any particular form, and in the other state it constitutes pillars shaped with great accuracy and regularity. STAFFA. The island of Staffa, one of the western islands of Scotland, and the Giant's Causeway, on the north coast of Ireland, near Londonderry, are remarkable instances of the latter state; and as I have seen them both, I will tell you what sort of places they are. STAFFA. This wonderful island was not generally known to exist, even by the inhabitants of Scotland, till the last century, when Sir Joseph Bankes happened to see it, and published an account of it. Since then it has been visited by numbers, and lately a steam-boat has regularly plied to it twice a week, from the little town of Oban, in Argyleshire. It was in this way that I went, and a most The inhabitants of Tobermory, (the little capital of Mull,) anxiously look out for the arrival of the steam-boat, for they are very poor, and the little money which the passengers spend, is a great object to them. On these occasions the inns are seldom large enough to accommodate all the strangers, and then a strange scramble takes place to get lodgings for the night. Most of our party succeeded in doing so, and the rest remained on board the steam-boat. We went to see a beautiful little estate on one side of the harbour of Tobermory, which belongs to the son of the old Laird of Coll, whom Dr. Johnson visited. The grounds are nearly in the shape of a triangle, and the two sides that are away from the sea, are formed by We started early in the morning, and passed several small islands of curious forms, composed of basalt; one in particular, which is called the Dutchman's cap, shaped like this. As we approached Staffa, on the north side, we could see scarcely anything of the pillars. It appeared a mass of Basalt, of very irregular shape, rising abruptly out of the sea, scantily covered with grass on the upper surface. It is the south side of the island that is chiefly remarkable, of which I will show you a picture that I made on the spot. It has (as you may see) exactly the appearance of a great layer of earth swelling out at the edges, resting on a vast number of pillars stuck close together. The colour of the pillars is nearly black, and that of the stratum above, lightish green, yellow, and brown, from the grass and variously coloured lichens that grow upon it. The sea is very deep, quite close to the cliffs. The day I was there, was as fine as possible; not a cloud was to be seen, and the great ocean was as calm as a mill-pond, which is not very common in these parts, for there is mostly a considerable swell. The celebrated cave of Fingal, as it is called, (but why, nobody knows,) is close to one extremity of the south side. FINGAL'S CAVE It seems just as if it had been formed by cutting away the middle of some of the pillars, since you can see that many parts of the pillars now remaining on the roof, are placed as if they were continuations of the stumps on which you walk at the bottom. We went into it in a boat, and when we were at the farther end, we got out upon the broken pillars and surveyed everything at our leisure. The length of the cave is two hundred and fifty feet, the breadth about forty, and the height above one hundred feet at the entrance, and seventy at the inner end. Along the middle of the roof, is a deep cleft, or fissure, which makes it something like a pointed arch, resembling the roof of a cathedral. The sides of the fissure are variegated, yellow, red, brown, and white, in consequence of water containing various substances, soaking through from the surface above; and on each side of it, there are several rows of the top of the broken pillars, which look quite black. On the sides at the bottom, the stumps form a sort of pavement like this, which is an exact Between these pavements the water is very deep, and as it flows direct from the Atlantic Ocean without any dirty shore or shallows, it looks very beautiful,—of a clear emerald green, showing at the bottom the black basaltic pillars in ruins, and a very few long luxuriant sea-weeds gracefully waving with the undulations of the water. The exposed surfaces of the pillars, between high and low water-marks, are covered with the little shell-fish called balanus, or BARNACLE, of colours varying from pink, which is the hue of those that are placed deepest, to yellow and white, which are those that are least covered by the water. The walls of the cave above these shells, are of a deep slate colour. The pillars which compose Here is a view of the inside of the cave. It is supposed that these wonderful pillars are formed by the cooling of a melted mass, and that this and other basaltic spots, are the remains of streams of lava from a volcano long ago extinct. In some of the lava streams of Mount Vesuvius, there has been noticed an approach to this structure, though not quite so regular as what we have been describing. You may understand in some measure how it may come about, by examining starch, which always hardens into little columns or pillars; and if you look at the little sketch of a portion of the pavement of the cave which I have given you above, you will see that nearly all the pillars It is remarkable what pains the basalt seems to have taken to get into a six-sided form. I should think about two-thirds of the columns have six sides, though sometimes one side is little more than a sharp edge blunted, because it seems to have been prevented by its neighbour making a similar effort to get its six sides complete. None of the remaining third of the pillars, have more than nine, or, of course, less than three sides. You might look a long time before you would find two pillars exactly alike. All this you will find occurring just in the same manner in starch, except that the edges of the basalt pillars are quite even, while those of starch are more or less waved or twisted. Near the side of the cave there is a little rock formed by pillars into a pretty regular cone, which you may see in the plate. It has a very striking appearance as you approach the island. Close by the rock there is a little cave, the mouth of which is formed by bent pillars, in this manner. The water in this is not very deep, but it was deep enough to give one of my companions a good ducking as he was trying to reach a shell which one of the ladies of our party wanted to possess. You will also often see something like these bent pillars in starch. THE GIANT'S CAUSEWAY. On the north coast of Ireland, the Giant's Causeway is a collection of similar pillars of rather a smaller size. They stretch far into the sea, and at low water you may walk a long distance upon the tops of them. The pillars get higher as they approach the cliff, and in the cliff itself, just above them, is a remarkable layer of fossil wood in the state called lignite, which closely resembles charcoal. At some distance from the Causeway, some of the pillars stand up by themselves, looking just like tall chimneys. There are also some wonderful caves in the Basaltic cliffs behind it, but none of them consisting of pillars like the great cave of Staffa. It is called the Giant's Causeway, because some people have fancied that it resembled the commencement of a great pier or causeway, which some beings of superhuman power had left unfinished. This is only a fancy for poets to talk of; you and I are now engaged about facts. There are some similar formations in Iceland, of very great extent, and in several other parts of the world; but those I have told you about, are the most remarkable which are known to exist. |
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