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of rays on substances--for instance, to compare either their various powers of heating, or of separating oxygen, or of discharging colour, or (which equally merits notice) of affecting odour and taste, we must evidently operate upon the genuine kinds of simple homogeneous rays contained in the sun's light decomposed by the prism. This is the only fair, unequivocal mode of making experiments on different forts of homogeneous light; and so excellent an optician as Professor Venturi, must have at once resorted to it, had he not entertained an unfortunate, but not unnatural, predilection for the form of process which he had himself invented, and whose merits, in other cases, we do not at all deny.

But whatever may be our opinion as to the eligibility of this method of inquiry, we can entertain no doubt of the ingenuity with which it is made fubfervient to the author's deductions, and still less can we withhold our applause from the fingular modesty of the style in which he concludes this branch of his researches.

• It is perhaps reserved (says he) for the industry of the age which is now opening, to determine with certainty the true reason of the des ļention of light in those coloured bodies, which owe their tints to the transmission of light alone, We must reft contented with having barely proved the fact ; happy if we have only succeeded in separating from each other, the four great operations by which colour is produced, so that the students of this science may not hereafter be induced to push farther than experience justifics, those laws, whose existence experience has disclosed.' p. 74.

IV. We now come to the last part of this valuable work, and it is inferior to none of the others, either in the ingenious originality of its combinations of facts (our author's characteristic quality), or in the clear and lucid manner of its detail. The fubjeét is the colours known by the names of accidental colours, imaginary colours, and ocular spectra. These appearances have formerly excited much attention, Profeffor Venturi difcuffed their nature in a paper which gained the prize in the Society of Modena ; and he now gives the outlines of the doctrines then advanced, with the confirmations added by his subsequent experiments. If he has given no new information relative to the causes of that phenomenon, we must admit, that he has at least added much to our knowledge of its circumstances, and has, by seasoning upon those circumstances, brought to light several interesting particulars regarding the law of their combinations. We present our readers with the propositions, in which his theory is condensed : !. The imaginary colour left in the retina, is always the same from the same real colour, whether that real colour be simple or mixed.

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2. The imaginary colours are produced in the retina in utter darkness, after it has been impressed with the real colours; and the real colours produce the imaginary ones in the following order : Red produces a tint between green and blue ; orange an indigo ; a colour between green and yellow gives a violet ;. 2 colour between green and blue gives a red; indigo gives an orange; and violet gives a tint between green and yellow. Thus, we see that the imaginary and real colours are always opposite to each other; and that if any imaginary colour B is produced by any real colour A, then the real colour B produces the imaginary colour A.

3. The nature of the fentient fibre of the eye is fuch, that when once excited, it continues of itself certain conceived motions or sensations, only changing and modifying them accorda ing to peculiar and regular laws.

4. The union or succession of different colours is agreeable and harmonious, provided the combined or consecutive colours are so related to each other, that the one is the imaginary colour produced by the other, when real. Thus, red and green are often observed to produce, when mixed, or following each other, an agreeable effect. Leonardo Da Vinci promised to represent, in a general enumeration, the colours which harmonize in a picture. Unfortunately, he has not executed the plan. But others have given detached remarks on this subject. Thus, Newton observes, that orange and indigo agree well together. And Virgil (an authority of a very different description) says, Mollia luteola pingit vaccinia caltha.' Now, it may be observ. ed, that orange is the imaginary colour produced by a real indigo, and conversely. Raphael Mengs, too, says that yellow and violet harmonize admirably together. Now, the tint of violet corresponds to a tint between green and yellow. The same painter adds, that red, yellow, and blue do not harmonize together ; but that each of these harmonizes with the intermediate colour of the other two; by which he means, that red harmonizes with green, yellow with violet, and blue with orange. A similar conclusion, very nearly, might have been drawn, a priori, from the above proposition, by inspecting the list of relations formerly given (prop. 2.), between the real and imaginary colours. Farther, it has been found in the theory of music, that a sound leaves in the ear the sensation of its twelfth, or the octave of its fifth ; and from thence are derived the leís perfect concords. Now, it is very remarkable, that if we divide the spectrum of simple colours according to the Newtonian rule, the tints which harmonize according to the proposition under confderation are exactly fifths to each other. Thus, it may be inferred, that the rules of harmony in sounds and in colours are exactly Gimilar ; and we trace, in this manner, a beautiful analogy between the senses of hearing and Gght-an analogy which future discoveries may perhaps extend to the senses of smell and tafte. Our author, however, adds an ingenious fpeculation, of a more general nature, upon the barntony of ideas. He observes, that universal experience in oratory, painting, architecture, poetry, as well as in the logic of scientific classifications, proves two diftinct points, first, that the union of fimilar objects gives a certain pleasure to the mind, viz. the pleasure derived from ora det, regularity, uniformity ; fecondly, that a certain pleafure is also derived from the apposition of extremes, viz. the pleasure of contrast. Hence, he infers that a law regulates all our mene tal pleasures in this particular, fimilar to the special law of calorific harmony above demonstrated, viz.' that those ideas or fensations are harmonious together, which, by the constitution of our minds, are mutually exchangeable.'

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5. If a real colour is impressed on the retina more strong than one formerly impressed, not one, but feveral different imaginary colours succeed it. This curious propofition our author demonftrates by very decisive experiments; and he shews that it is true of all fucceflions of the prismatic colours.

6. The sensations of different colours depend, not on different orders of fibres in the sensorium, but on different movements of the same fibres. Such language is much more theoretical, than the idea contained in the affertion. Our readers will easily perceive, that, without specifying the place or manner of sensation, and without any reference to the sensorium, as our author calls it, a true proposition is couched in the above terms.

7. If the rays of any kind whatever strike the eye with fuffscient force, a sensation of white is produced. This singular propofition, that the sensation of white depends not on the mixture, but on the intensity of the light which produces it, is proved in the following männer: If a spot of red light, separated in whatever way from the other rays, is looked at on a white paper, no colour but red is seen. But if those red rays fall on the eye, the image of the luminous body is white, except at its outer edges, which are tinged red. And our author attempts to show by fome calculations on the intensity of beams, that this effect ought not to be produced, by concentrating the same red rays on a chart, by means of a lens, but only when they fall directly on the

eye. We are inclined altogether to deny this propofition; to afcribe

the

the event of the experiment to fome deception produced in the eye, by the mixture perhaps of imaginary with real colours; and to maintain that if the mere increafed intensity of the red rays produced the sensation of white, that colour should certainly appear on the chart, provided the red rays, feparated by any means from a sufficiently large beam of lights were condensed by a lens, and the focus received on the chart. On the contrary, the more intense this focus of red rays is, the deeper is the red produced.

8. An imaginary and a real colour coinciding together mutually temper and mix with each other, exactly like two real colours. This proposition is proved by several very ingenious and original experiments.

We have now only to return our thanks to the author for the pleasure derived from the perusal of his very valuable work; to recommend it earnestly to the attention of our scientific readers ; and to express our hopes, that his new vocation * will not interfere with the farther prosecution of studies far more dignified and delightful to a rational creature, than the intrigues of courts, or the vulgar turmoil of republican factions.

A t. IIÍ. Poems from the Portuguese of Lais de Camoens, with Re

remarks on his life and IV ritings. Notes, &c. &c. By Lord

Viscount Strangford. Printed for J. Carpenter, London, 1803. THE Che minor poems of Camoens are held so low in the estimation

of the Portuguese themselves, that it cannot be considered as matter of much surprise, that their merits should be but little known among foreigners. Vain of having produced the first, we may fay the only epic poet that has adorned their peninsula, his countrymen are too apt to neglect his fmaller compositions, and to undervalue that originality of sentiment, and that strong and genuine expression of feeling in which they abound, and which claim for their author (as strongly perhaps as the boasted Lusiad itself) the character of a poet. Such being our opinion with regard to these pieces, we were much gratified at learning that a young person, distinguished by his ránk, and poffefsing a talte capable of discerning their neglected beauties, possessed at the same time fufficient industry to undertake to transplant thefe beauties into his native foil. Under the influence of these confiderations,

we

Profesor Venturi has lately been named ambaffador from the Ita. lian Republic to the Helvetic Body.

sve had been led, somewhat unreasonably perhaps, to form expectations of Lord Strangford's performance, which have not been completely realised; for, however we may have been gratified in the perusál of this little volume, by the easy versification, and the lively, though too often licentious imagination which it exhibits, we must own that we have not, upon the whole, derived from it that satisfaction which we were at one time inclined to anticipate. What part of our disappointment is to be attributed to the extravagance of our own ideas, and what to the insufficiency of Lord Strangford's translation, will best appear from a short congderation of the work itself, and a comparison of it with its original.

The poems, indeed, we must observe, in the first place, cannot honestly be termed translations from Camoens. The office of a translator requires, first, that he should express, in general, faithfully the ideas of his author; and, secondly, that his manner of expressing them should approach, as nearly as the difference of the Janguages will permit, to the style of the work which he translates. We will not fay that Lord Strangford has failed in both these points; he writes with too much facility to allow us to suppose that he could have been at a loss for language, had he made the attempt ; but, that he has totally neglected them, no one who compares any one of these pieces with the original, will hesitate to admit ; and though the diffidence with which his work is offered to the public, entities it, in other respects, to considerable indul. gence; the confident assertion contained in his prefatory remarks (p. 31.), that, ' for the most part, he has closely copied his author,'challenges, upon this ground at least, a feverer examination, more especially as the affectation of apologising now and then, by a note, for an insignificant deviation from his original, would seem to imply, that, where such apologies are omitted, no deviation has been made. The fourth sonnet in Lord Strangford's translation will serve to illustrate this remark; and we shall transcribe the whole piece, not as being a very accurate translation, but because, such as it is, it is less disfigured by those prettineffes with which Lord Strangford has thought it necessary to embellish his original, and is therefore better calculated to give some idea of the style of the Portuguese poet.

• Slowly and heavily the time has run

Which I have journey'd on this earthly stage ;

For, scarcely entering on my prime of age,
Grief mark'd me for her own ; ere yonder fun
Had the fifth lustrum of my days begun :

And fince, compul@ve, Fate and Fortune's rage

Have led my steps a long, long pilgrimage
In search of lost repose, but finding none !
For that fell star which o'er my cradle hung,

Forcod

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