Having never met with any rational account of certain stoney concretions, thrown up by the tides on a certain part of the shore at this place, and thinking them very extraordinary, I have attempted a description of them, which I request you to insert, with the drawings which accompany them (Pl. III. fig. 7, 8, 9, 10), in hopes it may excite the attention of the inquisitive and curious; and that some satisfactory account of their nature and origin may be obtained.
These stoney concretions are known here by the name of St. Cuthbert’s beads; but how they came by that appellation I have not met with any intelligent account. St. Cuthbert was the eighth bishop of Lindisferne about the latter end of the seventh century, and is highly famed in legendary records for his piety and austerity when living, and for miracles performed by his body when dead. I think it not improbable, though I have never received any hint of the kind, that St. Cuthbert may have recommended his hearers to count, and keep a register, as it were, of their repetitions of certain devout formularies, each day or week, with these stones ; and that thence they have obtained the name of St. Cuthbert’s beads. There is a vulgar, superstitious tradition, that they are made by that holy personage.
The form of these concretions is generally that of a complete cylinder; the height of which commonly exceeds the diameter, though not always. They are of various sizes ; few of them, however, exceeding three-fourths of an inch in length, and five lines in diameter; but many of them are very minute. In general they are of a dark clay colour; their surface is polished and shining, but surrounded at equal distances by circular furrows, seemingly dividing the concretion into so many smaller beads ; but, so far as my trials have gone, are not separable at these divisions.
Both ends of the cylinder are very beautiful ; the centre is indented, and of a pentagonal form, from which proceed radii to the circumference of the circle, and the margin is often somewhat elevated.
Each stone consists of two distinct parts, an exterior and central ; the former hard and brittle; the latter softer, more friable, and commonly of a darker colour. The pentagonal portion penetrates the centre of each stone. This may be scooped entirely out with a pin, or probe. Some very short ones are to be met with where this is wanting, a beautiful pentagonal hole being alone observed. This, how-ever, is rare, and appears rather to be accidental than natural.
Though these stones appear quite smooth, and of a dark clay colour, yet, when smartly struck with the blow of a common hammer, they shiver into many angular pieces, having a whitish crystalline appearance, exactly resembling the coarser calcareous spars. They are hard and brittle, but not so hard as to scratch glass, like the siliceous earths. While the exterior part of the bead thus shivers into pieces, the central portion either remains unaltered, or is, by the violence of the blow, bruised into a very dark clay-coloured powder. When the exterior part is pulverized, it is whitish.
Such is the appearance of the more regular formed of these concretions. They are not, however, all equally regular; the central part in all does not assume a pentagonal form. In many the radiated structure is scarcely discernible. On the sides of some are small protuberances, with concave smooth surfaces, having much the appearances of branches, or ramifications, as if the larger concretion shooted out smaller ones from its sides. But these varieties are perhaps the effect of some accident.
Besides these concretions, that are known by the name of St. Cuthbert’s heads, several others are to be met with on the same channel, not a little remarkable ; some resembling the knob of a horn, or cornucopia. The point of this concretion is smooth, and rounded, but the base is rough and irregular, evidently fractured. From the apex of the horn, as from a centre, proceed at regular distances small furrows, which extend length-ways towards the base, and thus give the concretion a striped appearance. It is also irregularly surrounded by annular divisions, like the St. Cuthbert’s beads, and, when broken, has a crystalline appearance, but it has no distinct central portion. The size of any of this kind that I have met with never exceeded the length of the first joint of the little finger. Others resemble stalactites, and probably are such ; these are cylindrical and laminated. There are also slender-branched stones, the surface of which is in-dented with numerous small-pointed impressions. These resemble corals so much, that I have no doubt they are of that class.
All these concretions are found on the beach to the west of this island, but on no other part of the beach. Here they are loosely scattered amongst the shells, pebbles, stones, etc., that are thrown up by the surf. I have examined the rocks and larger stones in the places adjacent, but have never met with any resemblances of them. On the north-east side of the island, however, there is a large track of limestone, which abounds with these concretions. They lie length-ways, and in clusters ; are deeply immersed, forming a part, as it were, of the substance of the limestone. Some are more superficial, and may be detached entire. They are evidently the same concretions with those I have just described, only they are not so regular, being compressed, or flattened, in many places, and their surfaces are coarser and unpolished. In none could I find the beautiful radiated end ; and the greater part had no distinct central portion. The horned-like concretions, when separated from the rock, still more exactly resembled those I have described as found on the western beach, only in general the latter are much larger.
The earth of all these I have found to be purely calcareous. When powdered, it effervesced violently with the vitriolic and acetous acid, and entirely dissolved in the muriatic, from which last it could again be precipitated by the vegetable alkalies.
To prove that the effervescence is occasioned by the discharge of fixed air, I have impregnated water with it by means of Dr. Nooth’s apparatus.
Struck with the difference in the appearance of the central and cortical part of the St. Cuthbert’s beads, I subjected them separately to trials with the acids. In doing of which, I as carefully as possible separated the two parts, and reduced them to powder ; and pouring the vitriolic acid upon each, I thought the central part effervesced much less violently than the exterior. Not satisfied, however, from this, of the truth, I reduced a whole bead to powder, without separating the two parts, and poured upon it some muriatic acid : it effervesced with great violence ; but on examination I found a small quantity of dark clay-coloured powder undissolved, evidently the central part. I varied the experiment, and poured upon a bead, in its perfect state, the muriatic acid, which acted violently upon it, soon dissolving all the exterior part, and leaving the interior portion quite detached, and upon which it seemed to have had no effect. This interior part retained its pentagonal form, and was besides beautifully ribbed.
From these experiments, I trust, it appears that the exterior and major part of the concretion is a pure calcareous earth ; and that the interior part is different. But, to what class of earths it is referable, I have not tried ; however, I have little doubt of finding it argillaceous.
Such are the natural appearances of the concretions called St. Cuthbert’s beads, so little known; and of whose origin I can form no determinate opinion. I think, however, it is plain, and will be generally allowed, that they must have had some other mode of existence (if I may so speak) than what we find them on the beach, or incased in the limestone.
How are we to suppose them originally produced ? Do they grow after the manner of corals? Are they petrifactions? Are they produced by a sort of crystallization? Do they increase in size, like minerals, by an opposition of new matter? Are they formed in the limestone rock ? Or did they not rather exist previous to their fixation there?
If any of your correspondents will favour me, through the channel of your useful and scientific publication, with an answer to these queries, or with a few pertinent remarks on the subject of the above-mentioned concretions, he will in a particular manner oblige.