cessarily, and perhaps luckily, forced to contemplate a good deal on the different subjects, and to try such experiments as were within my reach. The result was, that several things occurred to me which were new, at least to myself, and which throw light on the different branches of natural philosophy, and of meteorology in particular. These I have thrown into the form of Essays, in which are also given, such useful discoveries and observations of others as seemed necessary to be known, in order to form a proper idea of the present state of the science, and of the improvements that are yet to be made in it. In the first part I have given not only the observations made at Kendal by myself, but also, with his leave, those made at Keswick by Mr. CROSTHWAITE, keeper of the museum at that place, together with observations on the barometer and rain, made at London, for three years, taken from the Philosophical Transactions. results of the several observations I have arranged and digested to the best of my judgment. The observations on the height of the clouds, and on the aurora borealis, particularly the supplemental ones, are new, and, I suppose, in The some respects, original, having never seen any other of a similar nature published. In the second part, the first essay, though it contains little or nothing new, will be found a proper introduction to the subsequent ones. The second essay, containing the theory of the trade-winds, was, as I conceived when it was printed off, original; but I find since, that they are explained on the very same principles, and in the same manner, in the Philosophical Transactions for 1735, by GEORGE HADLEY, Esq. F. R. S.-See Martyn's Abridgment, Vol. 8, part 2, page 500. The third essay, on on the variation of the barometer, I should suppose will be considered as having some merit; it is new to myself, but as I am not well read in the modern productions on the atmosphere, I cannot say it will be found entirely so to others. It may be proper to observe, that I had not adopted the theory of vapour which is maintained in the sixth essay, when the third was printed ; but I know of no material alteration I would have made in this essay, had it been otherwise. The fourth and fifth essays are chiefly selected from the publications of others, except that in the latter I have offered some new thoughts on the effect of the situation of countries upon their temperature. In the sixth essay, amongst other things I have advanced a theory of the state of vapour in the atmosphere, which, as far as I can discover, is entirely new, and will be found, I believe, to solve all the phenomena of vapour we are acquainted with; I have attempted to solve several, particularly in the appendix. In the seventh essay the relation betwixt the barometer and rain is investigated, from the observations in the first part some conclusions are thence obtained in support of theory, and from which several useful and practical observations may be deduced. The eighth essay is the large one on the aurora borealis, which I have divided into six sections this will no doubt attract the attenThe reader will perceive tion of philosophers. all along, that I have spoken of the discovery therein contained as an original one; when I wrote the note at page 149, I had not seen the Abridgment of the Philosophical Transactions of the Royal Society; but I find from it that the learned and ingenious Dr. HALLEY formed an hypothesis to account for the aurora borealis by magnetism; in the Abridgment by JONES, Vol. 4, part 2, we find, that the Doctor, after enumerating particulars of several appearances, conjectures that they are occasioned by the earth's magnetism; and he endeavours to illustrate the hypothesis by placing a terella, or spherical magnet, with one of its poles upon an horizontal plane strewed with steel filings, which being done, the filings form various straight lined and curvilinear figures, according as they are situate near to or distant from the magnetic pole; these he thinks are analogous to the beams of the aurora borealis. The light of the aurora he is pretty much at a loss to account for, as electricity was then but imperfectly known. If these hints of his had been pursued by others, the fact would undoubtedly before this have been established, that the beams of the aurora borealis are governed by the earth's magnetism; but instead of this, philosophers have amused themselves and others with forming various other theories to account for the phenomena, most of which are extravagant, not to say ridiculous; M. MAIRAN's zodiacal light not excepted. Notwithstanding what the learned Doctor has suggested, I presume it will be allowed, that the above mentioned fact has not hitherto been ascertained, unless it be done in the following work. Whilst I am blaming others for framing fanciful theories, perhaps the censure may be retorted upon myself. The fourth section of the essay in question, entitled the "theory of the aurora borealis," will perhaps be regarded by many as wild and chimerical; but the facts which I have endeavoured to ascertain, respecting the aurora, will excuse me for a momentary indulgence of the ideas of a visionary theorist, if they be considered as such. The appendix contains the result of barometrical and other observations to determine the height of Kendal and Keswick above the sea, more exactly than is stated in the preliminary remarks to the observations on the barometer; also, an account of the heights of some mountains in the neighbourhood of Keswick; it concludes with a further illustration of the doctrine of vapour, and an explanation of some facts relating thereto, particularly those observed in working the air-pump. It will be sufficiently evident that I have |