flecting body, it is constantly bent at angles of deviation different from those of all other colours; the purples most; the blues less than the purples; the yellows, greens, and reds, successively less and less, according to the order of their specification. Such a state and condition, and such changes of light, are absolutely necessary for the existence and regular formation, under different circumstances, of the fringes; they are conformable to the general nature and principles of things, and, being required, are established by the phænomena; and being established by, explain them. That a beam of white light is composed of rays of different sorts, originally and always distinct, and of various colours, which are only separated from one another, is an hypothesis inconsistent with all the phænomena of inflections. • Indeed the very circumstance of the distribution of white light into colours, which admit of degrees and not of divisions, and the difficulty of conceiving in what manner, whether of particular arrangement, or undistinguished mixture, they must be re-united to form white, without conceiving or suspecting that differences might and, it would seem, ought to arise of colours from various orders or modes of combination, would lead us to infer the action of a principle which changes and modifies at the same time that it separates every portion of the white light, and requires an actual restoration of all things to the same original, or exactly similar circumstances of condition for its re-production.' P. 114. This opinion we shall not be expected to controvert, as we have, partly from similar views, and partly from other considerations, adopted no very different sentiments, which we have often mentioned in this journal. Indeed we have advanced farther, and thought that light was coloured only in consequence of its attenuation. Could we have gone more at length into our author's experiments, we might have pointed out additional circumstances which support this doctrine, while some which seem to militate against it may probably admit of an explanation different from that which the author appears to have favoured. While he rejects the Newtonian theory, he is not however very clearly intelligible in that which should supply its place. If the rays be supposed to be confusedly mixed in the white light, no regular formation of the fringes can be expected to be produced from amidst such disorder; nor will these difficulties be removed by conceiving every beam of white light to be again divisible into smaller portions or beams of white light composed of all the various colours; since even in these again a peculiar arrangement is required, which yet shall, as different occasions demand, differ from itself; and without a given appropriate arrangement there can be no regular formation, according to the before established principles of existence of the fringes. The fringes require that complete sets of the different coloured rays should issue at the same time from each interstice or point of passage of the medium, each of which rays should be equally related as to distance from the inflecting body on one side, and the particles of the medium on the other, at the time of distribution or separation, and equally related each afterwards as to distance and attraction to all the particles of the medium on all sides, and capable of being returned again, and of being united at the same time in the same place, under the same relations-circumstances altogether inconsistent with the nature of, and impossible with originally and perpetually different, distinct, and separate rays. The portions of light which pass through the intervals between the particles of bodies are truly and properly the rays of light. Thus it is firmly established, that in the inflections of light, each white ray of passing light is separated into many distinct rays; that of these rays, at the time of separation, each sustains a change; that this change constitutes a difference of each ray from every other, and from the original white ray; that this change or modification is permanent in each ray throughout all its future course of separate propagation; that this change or modification in each distinct ray operates, during all the future propagation of the ray, its different and appropriate effects; that this change or modification produces in each ray, under the same circumstances, unequal, and, under different circumstances, equal, changes of direction of course.' P. 119. The consequences of all these discoveries we shall not pretend to anticipate. The author promises largely, and we trust he will keep his word. We shall notice in the two subsequent articles a continuation of these inquiries. ART. XV.-New Observations concerning the Colours of thin transparent Bodies, showing those Phanomena to be Inflections of Light; and that the Newtonian Fits of easy Transmission and Reflection derived from them have no Existence, but fail equally in their Establishment and in their Application by Newton to account for the Colours of natural Bodies. 8vo. 4s. Boards. and Davies. Cadell ART. XVI.—Ân Account of the Irides or Corona which appear around, and contiguous to, the Bodies of the Sun, Moon, and other luminous Objects. 8vo. 1s. 6d. Cadell and Davies. WE notice these tracts together because the subjects are so nearly connected; and, though last in the period of publication, we shall first consider the Observations,' as they tend to elucidate the Account of the Irides.' In our former article we have offered our author's doctrine, with the experiments in its support, and have shown that he considers light to be coloured in consequence of inflection only. Why inflection should produce colour, he has not yet shown; and we would offer to his consideration the hypothesis of its arising from attenuation. It is no more singular that attenuated light should be coloured, and condensed light brilliantly white, than that a thin lamina of coloured glass should show its peculiar hue, and a mass of the same glass appear black. But to return to our author. He repeated the experiment of Newton respecting the coloured circles which appear in the thin plate of air, when two polished plates of glass are pressed together; and notices many circumstances which sir Isaac had overlooked. He examines also the phænomena of the soap-bubbles which depend on a thin plate of water of varying thickness, and finds that they result, equally with the appearances specified in the former tract, from inflection only. We quote the following conclusion, lest we might misrepresent the author if we employed other words; for he alludes somewhat obscurely to opinions not yet sufficiently explained. According to our principles of explanation, indeed, the ordinary affections of light passing from one transparent substance to another are not considered in the passage of the light of our experiments into or out of the thin plate. The fact is, that these ordinary affections are in a great measure taken away or suspended in plates of this sort, until they arrive at a definite thickness. The relative conditions of the surrounding medium or plate, upon which alone, independent of all density, the powers of reflecting or transmitting light at the surfaces of transparent bodies depend, are so changed within these limits, that the light passes into and out of the thin plate uninterruptedly; and this change is conformable to the general principles of formation and union upon which the existence and constitution of natural bodies depend, and is derived therefrom independently of any considerations respecting light. A discovery this in itself most important, and directly leading to a true knowledge of some of the most important phænomena of light. Thin transparent bodies do not therefore, according to their several thicknesses, reflect from and transmit through their further surfaces the different sorts of the rays of light, but their colours are produced by the inflexions of light within them.' P. 49. The author next proceeds to examine the Newtonian doctrine of colours, on which various superstructures have been raised. As, however, the system of fits of easy transmission and reflection is properly rejected, even sir Isaac Newton's superstructure is effectually undermined. Indeed the preliminary proposition of the different densities of the media surrounding the air is not confirmed by experiment; and all these appearances are, in every respect, similar to those produced by the knives, whose edges meet at a rectilinear angle. Even the glasses, when pressed together, do not seem to be in actual contact. The observations on Newton's doctrine of colours show much acuteness, and, so far as they are connected with his principles, are just but much is here alleged in opposition, which does not entirely depend on these principles; and this is of unequal value. With an alteration of language only, many of Newton's remarks on this subject will be found to be philosophical and correct. The full explanation must be referred to our author's promised publication of new discoveries; in which, so far as we can judge, he will not consider the subject in a mechanical view but he affords very slight hints only of what we may expect. In the Account of the Irides, our author clearly shows that these appearances are not explicable on the principle of refraction, but that, from the colours, their order and occasional inversion, they depend very certainly on the same principle which produces the fringes at the angles of the knives. He confines his present inquiry, however, to the smaller haloes and circles. round the sun, and does not attend to the particular state of the atmosphere in which they are observed; viz. its being filled with vesicular vapour. Indeed we see, from attending to a sunbeam, that there are always extraneous particles enough in the atmosphere to inflect or break some of the light into colours. ART. XVII.-Selim and Zaida. With other Poems. 8vo. 6s. Boards. Longman and Rees. FROM the perusal of a very sensible critical dialogue prefixed to these poems, we were led to entertain an idea of the author's powers, which was by no means confirmed by the perusal of the poems themselves. The story of Selim and Zaida, which occupies more than two-thirds of the volume, opens with the amorous lamentation of the fair one, who is prevented by a tyrannic father from bestowing her hand upon the youth of her choice; and who, in the course of her poctic grief, informs her attendant Leila that her lover will come in the evening to resue her from confinement. The destined hour arrives-Zaida issues from the gate of the fortress, and is received by her faithful Selim. At this interesting crisis 'Tis bliss. Short bliss!-Lo, through the air And many a torch with fiery glare • Dreadful in wrath the caliph comes. Selim is surrounded, and almost overpowered by the caliph's guards. • A shout succeeds: and, quick as light, In Selim's grasp a sword of flame Hark, 'tis a peal to rend the globe, All nature is convuls'd. The main Lo! that vast surge, of mountain height, • One fear now yields to newer fears. It glows to heav'n. It seeks the land. The purple simoom, swiftly glide, Or sees the hosts of sand arise, Those giant shapes, whose course denies All hope of flight, whose grasp is death.' P. 32. This column contains an angel, who rescues Selim from his enemies. Then, on the 'lov'd of thee and heav'n, |