in fome parts of the hill, for eight or nine years. Here, therefore, is a piece of natural history worth recording, and for which a theory is wanted.

THE appearances which have been here defcribed are, fo far as I know, fingular and unconnected with all others refulting from known causes. I know that fimilar circles have been observed by naturalists, and by them afcribed to thunder; as we should certainly have done in this cafe, were it not for the regular annual progreffion, which, if the effect of thunder, must follow rules not yet investigated, either in electricity, vegetation or the mineral system; for,

How comes.it, that the electrical operation takes place regularly in the fpring only, and that without any appearance of thunder?

2dly, How comes it, that the stripe of grafs destroyed by one operation, is always regularly progreffive in one particular direction, in relation to the first electrical operation?

3dly, Ir this progreffive appearance fhall be confidered as an electrical operation, and every fucceffive repetition as directed by the one immediately preceding it; then, how was the first produced; when was it; and when will be the last?

THE next conjectural cause that suggests itself as an explanation of those appearances, is the operation of infects. But there seems to be no lefs difficulty in reconciling any known animal-œconomy with the appearances under confideration, as the only cause of those appearances; for,

How fhould thofe animals have been diftributed in those feparated tribes upon the hill, and difpofed in the continuous tracks, fo as to exhibit lines of long extent, traversing ground and foil of various quality, as well as in tracks of very little extent; but, whether great or fmall, formed upon the fame principle, every part having a fimilar relation to a whole?

ARE these large tracks to be confidered as the extension of colonies which once had been fmall? or, Are thefe colonies dropped

dropped from the atmosphere upon the different parts of the hill, in the shape and extent in which we find thofe ftripes of withered grafs? This laft hypothefis is not fupported by any appearance that I know of in this country; and the other is not confiftent with the natural appearances to which it must belong; for the folitary or insulated spots, which often form part of a stripe, seem to be reproduced, in nearly equal quantity, each fucceeding year, without any gradual extenfion in the stripe, which also seems to preserve its former extent, as well as breadth and form.

THEREFORE, when we confider the various fituations and extent of those narrow ftripes of withered grafs, the regularity to be observed in their shape and progreffion, and the conftan-, cy which feems to take place with regard to their fucceffion, we muft, at the same time, be perfuaded, that there is a natural cause which may be investigated for the explanation of those appearances, and reject the mere fuppofition of caufes which do not seem, of themselves, adequate to the effect perceived.

GREAT attention would be required in making obfervations with a view to difcover the cause of thofe appearances; and the difficulty of this task is much increased by an ambiguity which occurs on certain occafions, where the breeding of infects in confequence of the death of plants, may be mistaken for the death of plants in confequence of infects; but, on the other hand, in the prefent cafe, great advantage, for an enquiry of this fort, may be derived from the opportunity that there is of examining, not only what had been killed the preceding, but also that part which is, perhaps, to be killed the enfuing feafon; and where experiment may be made by cutting off the communication betwixt those two parts as deep as the foil may admit.

THE apparent production, or rather the multiplication of some species of animals, in consequence of a certain destruction VOL. II.

b

of

of the vegetable turf, is a thing eafily to be conceived, like what happens in those stripes the second year, when I have seen an abundant crop of a certain fpecies of mushrooms in the track. Had animals of a particular species been found there, in the examination of the foil in those withered tracks, a rafh conclufion might have been formed, in erroneously attributing as a caufe for the appearance, what was truly an effect or consequence of the thing in question.

It is always making a step towards the difcovering the cause of a phenomenon, when causes which, with fome degree of probability, have been afcribed to an event, are found to be uncon-nected with, or to have no affinity to it; for this is the natural method of investigation, by examining the affinities or relations of things, and rejecting those as properly related, where there is found a discrepancy. Thus, as there is no effect without its proper caufe; fo, in proportion as a greater number of events are found to be unconnected with an appearance, fome kind of approach is made towards that by which the natural appearance is to be explained; but in cafes where events are multiplied or numberless, every approach of this kind is only negative; and fuch a method of investigation, while it may be the means of discovering the thing in queftion, only fhows that what we want is not attained. This, however, if made. with full conviction, is no contemptible step in natural philosophy, where, next to the investigation of the proper order in events, it is of the highest importance to avoid, or to correct, the improper connection of them.

THE explanation of the phenomena, in the prefent piece of natural history, either by thunder or the operation of infects, without having observed the actual connection of thofe different events, is merely conjectural, as would be equally the refufing to admit for explanation a known cause, which, though not actually observed as connected with the event in queftion,

had,

had, in other respects, the requifites for producing a fimilar effect.

BUT all that is known at prefent of electricity, or the operation of infects, is far from being fufficient to be confidered as the explanation of the appearances in question; for,

THOUGH the growing plants, or the vegetation of a portion of the living turf, may be killed either by means of electricity or infects, these are not the only means by which that effect may be brought about; at the same time that this is the only circumstance, in the natural appearance, explainable by the fuppofed caufe: Therefore, as every circumstance in an appearance must be properly related to a cause, by which it is to be explained, so the many circumstances here found, without any affinity to, if not inconfiftent with the conjectured caufe, will leave no room for admitting fuch an explanation, according to the present view which has been given of the subject.

II. An ACCOUNT of the Method of making the OTTER of ROSES, as it is prepared in the Eaft Indies. Communicated in a Letter from DONALD MONRO, M. D. of London, to Mr JOHN ROBISON, Profeffor of Natural Philofophy in the University of EDINBURGH

I

SIR,

London, Jermyn Street, July 10. 1783.

HAD the following receipt for making the Otter of Rofes, as

it is prepared in the Eaft Indies, from Major MACKENZIE of Coull, in the county of Rofs, who told me he got the account from an officer of his corps, who was up in the country where it is prepared, and affisted in making it himself.

TAKE a very large glazed earthen or stone jar, or a large clean wooden cafk; fill it with the leaves of the flowers of roses, very well picked, and freed from all feeds and ftalks; pour on them as much pure fpring water as will cover them, and set the veffel in the fun in the morning at funrife, and let it stand till the evening, when take it into the house for the night; expose it in this manner for fix or feven fucceffive days, and, at the end of the third or fourth day, a number of particles, of a fine yellow oily matter, will float on the furface, which, in two or three days more, will gather into a fcum, which is the Otter of Rofes. This is taken up by fome cotton, tied to the end of a piece of stick, and fqueezed with the finger and thumb into a small phial, which is immediately well stopped; and this is repeated

*Read in the Philofophical Society of Edinburgh in 1783; and published by order of the Committee for publication of the Transactions of the Royal Society of Edinburgh.