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Art. Í. Letters concerning the Northern Coast of the County of
Antrim, containing a Natural History of its Bafaltes, by the Rev. Mr. Hamilton. 8vo. 45. Robinsons, London,
, and in particular the fingular combination of basaltic pillars, commonly called the Giant's Causeway, have long attracted the attention of travellers, and been the subject of research and investigation to philosophers. The native inha. bitants of the coast, who were the first observers of this phenomenon, .accounted for its production, by a theory rude and fimple, and to men ignorant of natural history not very abfürd. They observed, that the causeway was a regular mole, .projecting into the sea ; they discovered, on closer inspection, that it was built with an appearance of art and regularity, re sembling the works of men, though on a larger scale than had ever been seen ; and they concluded, that human ingenuity and perseverance, if supported by sufficient power, were abun. dantly adequate to its production. Their own traditions, fimilar to those of other nations, concerning the extraordinary ftature and strength of their ancestors, suggested the cause of this prodigy of art ; and the celebrated Fingal, the hero of ancient Ireland, as well as of Scotland, became the giant under whose forming-haná this curious structure was erected.
It was afterwards discovered, that a pile of similar pillars was placed somewhere on the opposite coaft of Scotland, and as the business of latitụdes and longitudes was not at that time
ENG. Rev. Vol. VI. March 1786. L
accurately ascertained, a general confused notion prevailed that this mole was once continued across the sea, and connected the Irish and Scottish coasts,
Towards the close of the last century, the Royal Society of London began to inquire and to speculate concerning this singular phenomenon. But, as the information which they received was imperfect, the conclusions which they drew were erroneous. Dr. Molleneux took considerable pains to illustrate the subject, but the necessary attendance of his profession prevented him from making his observations in person, for which he seems to have been well qualified. By his influence, the Dublin Society employed a painter, of some eminence, to make a general sketch of the coast, near the causeway; but he, indulging his imagination, drew a picturesque view of the scene, rather than a philosophical landscape.
From that period, this curious work of nature passed almost unnoticed for half a century; and men of fcience turned their eyes from an object, which had hitherto baffled the attempts of every theorist.
In the year 1740, Mrs. Susanna Drury made two very beautiful and correct paintings of the Giant's Causeway, which having obtained the premium appointed for the encouragement of arts in Ireland, and being engraved by an eminent artist, directed the attention of the world again to this celebrated subject. Soon after, Dr. Pocock made a tour through the county of Antrim, and took a general view of the coast. But, as generally happens in the infancy of science, he was more zealous to align causes, than to investigate facts; and started a new but crude theory, imputing the regular figures of the basaltic columns to accidental fits of precipitation, in a watery medium ; which is not only hypothetical, but inadequate to the production of the effects.
It is to be observed, that the species of stone of which the causeway is formed, is to be found throughout the whole extent of the contiguous country : And, within these few years, it has been discovered, that the basaltes is a very common foffil, through every part of the world. Hence, the observations of men of science, in diftant places, have been united on this subject; different theories have been compared together, and more general analogies suggested on which to build some rational conjectures concerning the cause which produced these wonderful columns.
The ingenious author of these letters gives us the natural history of these columnar basaltes, previous to the investigation of the cause to which they owe their origin.
« The causeway itself is generally described as a mole or quay, pro. jetting from the base of a Iteep promontory, some hundred leet, into
the sea, and is formed of perpendicular pillars of basaltes, which stand in contact with each other, exhibiting an appearance not much unlike a solid honeycomb. The pillars are irregular prisms, of various denominations, from four to eight fides * ; but the hexagonal columns are as numerous as all the others together.
On a minute inspection, each pillar is found to be separable into several joints, whose articulation is neat and compact beyond expresfion; the convex termination of one joint always meeting a concave socket in the next ; besides which, the angles of one frequently shoot over those of the other, so that they are completely locked together, and can rarely be separated without a fracture of some of their parts.
· The sides of each column are unequal among themselves, but the contiguous sides of adjoining columns are always of equal dimensions, so as to touch in all their parts.
• Though the angles be of various magnitudes, yet the sum of the contiguous angles of adjoining pillars always makes up four right ones. -Hence there are no void spaces among the basaltes, the su face of the causeway exhibiting to view a regular and compact pavement of polygon ftones.
• The outside covering is soft and of a brown colour, being the earthy parts of the stone nearly deprived of its metallic principle by the action of the air, and of the marme acid which it receives from the sea t.
· These are the obvious external characters of this extraordinary pile of basaltes, observed and described with wonder by every one who has seen it. But it is not here that our admiration should cease ;
whatever the process was, by which natuie produced that beautia ful and curious arrangement of pillars to conspicuous about the Giant's Causeway ; the cause, far from being limited to that spot alone, appears to have extended through a large tract of country, in every direction, insomuch that many of the common quarries, for several miles around; seem to be only abortive attempts towards the production of a Giant's Causeway.
• From want of attention to this circumstance, a vast deal of time and labour has been idly spent in minute examinations of the causeway itself ;--in tracing its course under the ocean - pursuing its columns into the ground-determining its length and breadth, and the numbers of its pillars with numerous wild conjectures concerning its original ; all of which cease to be of any importance, when this spot is consi.
* Monsieur Faujas de St. Fond took much pains to search for pillars of nine sides among the basaltes of Viverais, in consequence of the account which Mr. Molleneux and Monsieur de Lifle gave that such were to be found ; but there is little doubt that both those gentlemen were mistaken, as none of that denomination are to be discovered at the Giant's Causeway, or its neighbourhood. Indeed očiagonal pillars are very rarely to be met with.
't This coating contains iron which has lost its phlogiston, and is nearly reduced to a state of calx ; for with a very moderare heat ic becomes of a bright red ochre colour, the attendant of an iron earth.
dered only as a small corner of an immense basalt quarry, extending widely over all the neighbouring land.
• The leading features of this whole coast are the two great promon. tories of Bengore and Fairhead, which stand at the distance of eight miles from each other : Both formed on a great and extensive scale, both abrupt towards the sea, and abundanty exposed to observation, and each in its kind exhibiting noble arrangements of the different species of columnar basaltes.
• The former of these lies about seven miles west of Ballycastle, and is generally described by seamen, who see it at a distance and in pro. file, as an extensive headla d, running out from the coast a considerable length into the sea ; but, ftrictly speaking, it is made up of a number of leffer
and bays, each with its own proper name, the tout ensemble of which forms what the feamen denominate the headland of Bengoie.
• These capes are composed of variety of different ranges of pillars, and a great number of ftiata ; which, from the abruptness of the coast, are extremely conspicaous, and form an unrivalled pile of natural architecture, in which all the neat regularity and elegance of art is united to the wild magnificence of nature.
• 'The most perfect of these capes is called Pleaskin, of which I shall attempt a description, and along with it hope to send a drawing which my draftsman has taken from the beach below, at the risque of his. neck; for the approach from these promontories down to the sea is. frightful beyond description, and requires not only a strong head, but very considerable bodily activity, to accomplish it.
• The summit of Pleaskin is covered with a thin grassy sod, under which lies the natural rock, having generally an uniform hard surface, fomewhat cracked and shivered. At the depth of ten or twelve feet from the summit, this rock begins to assume a columnar tendency, and forms a range of maliy pillars of basaltes, which itand perpendicular to the horizon, presenting, in the sharp face of the promontory, the appearance of a magnificent gallery or colonade, upwards of fixty feet in height.
• This colonade is fupported on a folid base of coarse, black, irregular rock, near fixty feet thick, abounding in blebs and air-holes--but, though comparatively irregular, it may be evidently obferved to affect a peculiar figure, tending in many places to run into regular forms; re. sembling the thooting of salts and many other dubliances during w. balty crystallization.
• Under this great bed of stone stands a second range of pillars, between torty and fifty feet in height, less grofs, and more sharply defined than thole of the upper story; many of them, on a close view, emulating even the neatness of the columns in the Giant's Causeway. This lower range is borne on a layer of sed ochre itone, which serves as a relief to thew it iu srcat advantage *.
* The only inttances of different ranges of bafaltes, that have hitherto been discovered, occur in the valuable work of Monf. Faujas de St. Fond on the volcanoes of Viverais, &c. but the arrangement which appears there, even with the neatness that always attends an engraving, is 'y inferior to that of Pleakin.
* These two admirable natural galleries, together with the interjacent mass of irregular rock, form a perpendicular height of one hundred and seventy feet ; from the base of which, the promontory, covered over with rock and grass, slopes down to the sea for the space of two hundred feet more, making in all a mass of near four hundred feet in height, which in beauty and variety of its colouring, in elegance and novelty of arrangement, and in the extraordinary magnitude of its objects, cannot readily be rivalled by any thing of the kind at present known
Besides the basalt pillars of these two magnificent promontories, there are many other fimilar arrangements through the country. In the mountain of Dunmull, two different ranges of columns may be discovered. They are found also at Dunluce-hill; in the bed of the river buth ; on the summit of the mountain of Croaghmore ; in the highland over Ballintoy; in the island of Rbagery; and various other places, through an extent of coast, about fifteen miles in length and two in breadth. Beyond this tract, which abounds in perfect pillars, an attentive observer will trace the same species of foflils in very distant parts of the country, so far as the northern shore of Loughneagh, and the mountains of Derry ; in many places of which imperfect columnar forms may be observed : So that the great cause which generated this species of stone has been exerted through a space of more than forty miles in length, and twenty in breadth ; that is, through above eight hundred square miles.
In the gth letter Mr. Hamilton gives an analysis of the ba. saltes, and an explanation of its most remarkable properties, from the known elements of which it is composed. Its principal component parts are iron in a metallic ftate, combined chiefly with filicious and argillaceous earths. From a know, ledge of these elementary parts of the basaltes, we are furnished with an analogy tending to throw light on the regularity of its form. Silicious earth, which is one of its component parts, frequently affects a regular figure. Thus rock chrystal, which is a pure finty earth, is commonly disposed in the form of hexagonal prisms, the denomination of fides which chiefly prevails among the basaltic pillars.--Thus various crystallizations are found to take place in the metal of
• * Mr. Pennant is much mistaken in his opinion that the little island of Staffa, whose greatest height is but one hundred and twenty.eight feet, contains any object equal to the bold promontories of Bengore. - Neither are the beft specimens of pillars at Staffa at all comparable to those of the Giant's Causeway in neatness of form, or fingularity of articulation.' L 3