I now fulfil a part of the promise I lately made you, of a communication upon the subject of natural history & philosophy.

Arthur’s seat you know to be a considerable hill in the neighborhood of Edinburgh. While I was in that city, my excellent friend Professor Dugald Stewart7 informed me, that Dr. Hutton (one of the philosophical society of that place) had written a paper concerning certain appearances on parts of the turf upon this hill;8 and we agreed to request Dr. Hutton to acompany us in order to point them out. Dr. Hutton, with all that enthusiasm for inquiry which is so natural & so peculiar to him, most kindly and obligingly consented. We accordingly ascended the hill; the season I think being very early in May, and that in the present year.

The first circumstance which Dr: Hutton made us observe was a variety of circular marks or stripes in the grass, often known by the name of fairy rings; and such as, I presume, in their simpler state, you have yourself frequently noticed. He then proceeded to analyze some of them more particularly. He told us that sometimes they were only segments of circles, and that these larger segments and the circles, were again always composed of smaller segments; the bandings of the segments, whether compound or simple, being regularly directed inwards. In the middle of these striped marks there was usually a line of decayed turf, bordered both without & within with deep green. These lines he particularly said were not gradually but suddenly produced, and that too in the spring season; the operation also he found was an annual one, except that in one or two seasons he had remarked it failing; and the appearance of the new line was always on the outside of the old one, (being perhaps a foot or two in breadth in the whole). This decayed turf, he told us, was after a time renewed; though sometimes very slowly, insomuch that the traces belonging to ten or twelve seasons (as he afterwards shewed us) might be discovered remaining at once.— Dr. Hutton now carried us to a different part of the hill, and directed our eyes to an appearance which seemed particularly striking; it was no less than a tract of decayed grass with green bordering, curving itself away within our sight to a very considerable distance; and running over to a swelling of the hill perhaps a quarter of a mile off, where it looked like a thin brown path, having if I mistake not, like such a path (and partly perhaps for the same reasons) its double bordering of green. In one part of this track & near the spot where we stood, Dr. Hutton enabled us accurately to distinguish the instances of the operations of successive seasons just alluded to.— Dr. Hutton having given us this entertainment, next told us how these circumstances first became the subject of his attention. Dr. Adam Ferguson (the celebrated author) in his walks upon this hill, had for some years observed changes taking place in particular appearances in the turf; and the whole seemed so singular, that he engaged his friend Dr. Black (the chemistry professor, with whose fame & person you are so well acquainted) to take a view upon the spot.9 Dr. Hutton being in turn informed of them, made them matter of observation during a course of twelve or fifteen years; and the result of his curious discovery, as far as my recollection serves me, is sufficiently given in this relation.— There is indeed one remaing particular which he added; namely that in his own paper upon the subject (which unfortunately I have not seen,) he has given reasons for concluding that this phaenomenon can neither be attributed to lightning nor to insects, to one or other of which causes others had been willing to ascribe it.

Dr. Hutton was himself wise enough to give us no conjectures upon the subject; but your unfortunate friend found it impossible for his imagination to be quiet, and as he wanted evidence for a theory, he endeavored at least to think of an hypothesis that should methodize his ideas of the appearance.— I thought then, that if some destructive (though to me unknown) cause, should operate upon a particular spot of turf, that this spot might prove a nucleus or center to all that was to follow; and that when the grass in it had decayed and the earth underneath it became fallow, an increase of nutriment might arise to the grass immediately round that fallow; which grass would in consequence become greener & perhaps more vigorous. The next step in the hypothesis required to be a handy one, and was as follows: These appearances seeming to be most frequent upon bare commons, where there is little manure, I guessed that rich grass might be unfavorable to their production; and thence I supposed, when the soil was prepared to extend itself in the following year, that it was obliged to omit the circle of (vigorous) green grass just spoken of, and to penetrate beyond it to other turf less advantageously circumstanced, and there begin its progress afresh; and if the c [?] every where nearly at equal distances from its first [?], the second portion of fallow of course would become a circular one; attended with fresh green without; and a heightened green within, where the fallow from both sides had aided it. Other circles of fallow and of green might now easily be supposed succeeding, and if necessary ad infinitum.

Sometimes I could not trace out any fallow line completely; and sometimes I even thought that the whole of the grass affected became even uniformly greener. The green in some cases was very bright; in other cases it was dark and deep. When I took notice of this exception, it was late in autumn and upon Salisbury plains; but as I had been allowed the period only of five months to observe in, (which does not amount to a single season,) I cannot conclude any thing upon the subject. If the appearances of this description belong to the same class with the rest, I should be a little inclined to suspect that the cause which before operated as a destroying one, produced this effect only from its excessive tendency to create fertility; and as the best manure when immoderately used burns up the grass beneath it (though it increases the green around it,) so both here and with the manure, a more moderate application of the power might have produced only a just fertility. But if this conclusion should prove against facts, I then should guess that this uniform greenness might be occasioned by the operation of a former year being followed by a very speedy return to vegetation, and consequently to greenness.— As to the general tendency which all these figures have to partake of a circular form, I have already spoken of such effects as may originate out of a central spot; and how naturally circular forms seem to admit of being propagated from such spots. Appearances in the form of the arithmetical figures 3 & 8, and so on, not unfrequently occur, especially the first of them; but these seem to come under the general principle, and to arise partly from natural interruptions, and partly from two or more circles interfering, their progress ceasing, (or at least ceasing to be conspicuous,) whenever they are forced to repeat it where a former process has been before them.— In saying these things, I pretend to discover no specific cause; I have only indulged myself in a temporary supposition, that serves (as I said before) to methodize one’s ideas of these appearances, and to make it more convenient for true theory to be afterwards applied to them.

I shall now put down a few more facts, which have occurred particularly to myself.— These appearances then I observe, are not confined only to Arthur’s Seat. I have travelled about a good deal during the late summer, and as I passed along in haste, I got slight views of a number of them. They are sufficiently frequent upon certain downs: Thus upon leaving Romney marshes in sussex and travelling Westward, I saw a few, at Brighthelmstone upon the Steene, I saw them rather abounding, some of them being strongly marked, and exhibiting small but very complete circles; I saw them again without the Devil’s Dyke, and I saw more of them near the termination of the downs in travelling westward towards Chichester. I met with them again upon various parts of Salisbury plains, particularly near Stone-henge, where one of them incircled a fixed stone, close to that noted heap of stones; and I must farther observe that some of those upon Salisbury plain were of a very vivid green; and some too were tolerably large, both there, and upon the Western Sussex downs. I also found them upon the York road, about 119 or 120 miles from London; and again on a lawn near Dancomb Hall in Yorkshire; also on the lawn near the house at Mount Edgecumb opposite to Plymouth; and lastly here within my view in my father in law’s grounds at Totteridge[.]— In this latter place & in a spot to the West of Romney marsh, I was struck with the sight of a species of fungi, coming up in the midst of the stripes.—1 Respecting the general size of these stripes, they are usually I think from about five to twenty feet in diameter; some of them are considerably larger, but none that I have yet seen are comparable in point of size to the great one upon Arthur’s Seat. For I cannot but conjecture that even this large one began from a nucleus, though perhaps it may have taken a century or two to extend itself. And if this guess be true, the extent in other cases may serve as a symptom by which to judge of the age.— The succession of stripes also I have no where seen so strongly marked as upon the same hill, thought other places afford the traces of some few successions.— Where the decayed grass appeared in the middle of the large track before mentioned (upon Arthurs seat,) I approached nearer, and found it exactly resembling grass parched by the summer droughts, and it was also equally slippery to the feet. And where the grass affected during the former season had rotted away, the dissolution was so complete, that the mould & soil appeared in its room; sunk indeed somewhat, like a shallow trench, the turf on each side serving to form its banks.— There are several imitations of these stripes often seen upon grass; & some of them may with great appearance of probability be supposed to arise from the dung which horned cattle frequently let fall in curved lines, or even from the staling of various sorts of cattle which may happen to light in the same directions. But I conceive that with a little experience and examination, these deceptions may often be detected, particularly as the size of them cannot usually be considerable.— I must not however omit one remark referable to this head, which is that though the stripes are not always confined to Downs, yet I think in almost every instance that I have seen, they have been confined to places on which sheep have been generally or at least occasionally fed; and even in the doubtful cases, it is very possible that this observation about sheep is not wholly to be excluded.

In no place that I know of, have these appearances been so well watched as upon Arthur’s Seat; and perhaps in no place have they been so signal, and at the same time, so near the residence of curious persons. Since my being made acquainted with these particular ones, I have desired a very diligent and careful inquirer in that neighborhood to continue those observations which we owe to the accuracy of Dr. Hutton; and I have taken the liberty of suggesting to him the hints of a few experiments on the subject; As for instance, to try whether the cause can be transplanted by means of a piece of the green or of the withered turf; also whether its progress can be checked by cutting trenches, or placing solid obstacles in its way; and likewise whether the appearances of the roots, or of the soil under it, will help to any discovery &c.

I have nothing to add to so long a letter founded on so short a period of inquiry, except my wishes that you would communicate the subject of it to the curious of your acquaintance in France, that we may learn what France produces of the same kind. And I am induced to adopt this request, partly because I believe Dr. Hutton has not been able to procure the sight of any Memoirs whatever on the subject; and partly because I am myself willing to hear of the subject being pursued, as some new fact or principle may arise from it, that is useful and curious, and which may at least in one instance more tend to strengthen our disinclination to favor the idea of præternatural or unintelligible operations.

I am, my dearest sir, your ever devoted, most affectionate, & obliged,