phenomenon pretty frequent in the fields, &c., supposed by the vulgar to be traced by the fairies in their dances. There are two kinds of it; one of about seven yards in diameter, containing a round bare path, a foot broad, with green grass in the middle of it. The other is of different largeness, encompassed with a circumference of grass. Messrs. Jessop and Walker, in the Philosophical Transactions, ascribe them to lightning; which is thought to be confirmed by their being most frequently produced after storms of that kind, as well as by the colour and brittleness of the grass roots when first observed. Lightning, like all other fires, moves round, and burns more in the extremity than in the middle; the second circle arises from the first, the grass burnt up growing very plentifully afterwards. Others maintain that these circles are made by ants, which are frequently found in great numbers therein.—Mr. Cavallo, in his treatise on electricity, does not think that lightning is at all concerned in the formation of them: "They are not (says he) always of a circular figure; and, as I am informed, they seem to be rather beds of mushrooms than the effects of lightning.

We have frequently observed beds of mushrooms arranged in a circular form like what are called fairy rings; but it will be difficult to account for the mushroom seed being disposed in this manner. It is probable that the seed is dispersed over the whole field, and remains dormant till it is acted on by some stimulus to excite its vegetating powers. Perhaps this stimulus is atmospheric electricity, which acting on particular spots only, produces on them an abundant crop of mushrooms, while none appear in other places.