FAIRY rings. The circles of dark green grass, frequently observed !in old pastures, have long been known under the name of fairy rings, and have gene rally been supposed to be occasioned, in some way or other, by electricity. Dr. Wollaston has, in a late volume of the " Transactions of the Royal Society," given a new and very ingenious theory, of which we shall present our readers with a brief account, premising that Mr. Davy, in the course of his lectures at the Royal Institution, had occasion to refer to the subject, and seemed to coincide in opinion with Dr. Wollaston. That which first attracted his notice was the position of certain fungi, which are always found growing upon these circles, if examined In a proper season. The position of these fungi led him to imagine, that the pro gressive increase from a central point was the probable mode of formation of the ring : hence he conjectured that the soil, which had once contributed to the support of the fungi, might be so exhaust ed of some peculiar pabulum necessary for their production, as to be rendered incapable of producing a second crop. The second year's crop would, if this the ory he just, appear in a small ring sur rounding the original centre of vegeta tion, and at every succeeding year the defect of nutriment on one side would necessarily cause the new roots to extend themselves solely in the opposite direc tion, and would occasion the circle of fungi continually to proceed, by an annual enlargement, from the centre outwards. An appearance of luxuriance of the grass would follow as a natural consequence, as the soil of an interior circle would always be enriched by the decayed roots of fungi of the year's growth. This theory is sup ported by some observations of Dr. With ering ; and Dr. Wollaston says, by way of confirmation, that whenever two ad jacent circles are found to interfere, they not only do not cross each other, but both circles are invariably obliterated between the points of contact ; the exhaustion oc casioned by each obstructs the progress of the other, and both are starved. Phil. Trans. 1807, Part. H.
Though it cannot be doubted that most fairy rings, if not all of them, have consi derable relation to the running of a fun gus, there, nevertheless, seems reason to conclude that electricity may likewise be concerned in their production. The electrical effect may relate to fairy rings of a different kind from those occasioned by the fungus, or it may have been ante cedent to the production of the vegetable. It is a familiar effect in our experiments, that the spark proceeding from a posi tive conductor breaks or radiates at about one-third of its course, and strikes the receiving conductor by a central spark surrounded by other smaller ones. The
concentric rings produced upon polished metallic surfaces by the strong explosion of a battery, as first observed by Priest. ley, appears to be a fact of the same kind ; and the forked radiations of light ning are well known. The editor of this work related in the Phil. Journal, Vol. I. 4to. some events which happened in Ken sington Gardens in June, 1781, when a very powerful thunder storm passed over the western extremity of London. The explosions were very marked and dis tinct, and in many instances forked at the lower end, but never at the top ; from which it seems proper to conclude, that the general mass of clouds, or, at least, that extremity which passed over London, was in the state called po sitive.
Five days afterwards, upon visiting Kensington Gardens, it was observed, that every part of that extensive piece of ground shewed marks of the agency of the lightning, chiefly by discolouration of the grass in zigzag streaks, some of which were fifty or sixty yards in length. In stances of this superficial course of the lightning along the ground, before it enters the earth, are sufficiently frequent. But the circumstances applicable to our present subject is, that five trees, out of a grove consisting of seven, had been struck by the lightning. Two of them, which stood on the outside to the, west. ward, had holes torn in the ground close to the trunk ; and round one of these trees was a space of six feet in diameter, in which the grass was very much scorch ed. Another tree on the west was sur rounded by a faint ring of burnt or faded grass, which seemed to be occasioned by some earlier stroke, as the vegetation had began .to shoot up again. Another tree, standing on the outside to the south, was surronnded by a ring of twelve feet diameter and eighteen inches broad. Within the ring the grass was fresh ; but on the surface of the ring, the grass and the ground were much burned. To the eastward of the tree, upon the ring itself, were two holes, in which the ground had the appearance of ashes. Another tree, on the east side of the grove, had the half of a faint ring to the westward. And, lastly, a tree which stood in the middle was surrounded by a faint ring of twelve feet diameter, within which the grass was unhurt ; and to the west ward., at the distance of about three feet from the inner ring, was part of another similar ring, of nearly the same appear ance; the verdure being unhurt in the interval between the rings.