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of higher refractive power than the medium under examination. Since the surfaces of a stratum so interposed are parallel, it will not effect the total deviation of a ray passing through it, and may therefore be employed without risk of any error in consequence.

Thus, resin, or oil of sassafras, interposed between plate glass and any other prism, will not alter the result.

If, on the same prism, a piece of selenite and another of plateglass be cemented ncar each other, their powers may be compared with the same accuracy as if they were both in absolute contact with it.


For such a mere comparison of any two bodies, a common triangular prism is best adapted; but, for the purpose of actual measurement of refractive powers, I have preferred the use of a square prism. because, with a very simple apparatus, it shows the sine of refractive power sought, without the need of any calculation.' p. 365.

This mode of measuring the refractive power is often useful in determining the genuineness of substances, since those of the same kind possess this property, with little variation. The first table contains a series of substances, arranged according to their refractive powers.

The second section of this paper relates to the dispersion of light, which is regulated by very different laws from refraction, since, at a given incidence, bodies may refract unequally and disperse equally. When different media, in contact, differ greatly in dispersive power, the usual order of prismatic colours may be reversed. They are found to be so, by the application of oil of sassafras to a prismn of flint glass. Numerous similar instances are mentioned; and the second table contains a series of substances, in the order of their dispersive powers, both in water and alcohol. The solutions of the more perfect metals possess the greatest power of this kind, particularly the nitrates; yet sulphuret of potash rises above the muriate of iron, the nitrate of silver and copper oil of sassafras disperses light very powerfully; but the effect of some other essential oils, in this respect, is much more inconsiderable. The least dispersive metal is zinc. A third table contains a series of substances with their refractive and dispersive powers, ascertained by means of edges, in the manner of Mr. Dollond and Dr. Blair. These, however, are less distinct; and the results, in some measure, differ. With respect to the colours of the spectrum, our author is not inclined to reduce them to three: yet, by employing a very narrow pencil of light, he sees four only; viz. red, yellowish-green, blue, and violet; but in this there is apparently a deception. He points out also the existence of invisible rays beyond the violet, such as Herschel supposes to exist on this side the red. Our author's test is blackening

the muriate of silver. With these two kinds of invisible rays, be thinks the whole number to be six.

• XIII. On the oblique Refraction of Iceland Crystal. By William Hyde Wollaston, M. D. F. R.S.'

Our author's theory on this subject cannot be very intelligibly abridged. It is connected with Euler's doctrine of light, which he supposes to be propagated by the vibrations of a highly elastic medium.

In ordinary cases, the incipient undulations are of a spherical form; but, in the Iceland crystal, light appeared to Huygens to pro-, ceed as if the undulations were portions of an oblate spheroid, of which the axis is parallel to the short diagonal of an equilateral piece of the crystal, and its centre the point of incidence of the ray.

From this spheroidical form of the undulations, he deduces the obliquity of refraction; and lays down a law, observable in all refractions, at any surface of the spar, whether natural or artificial, which bears the closest analogy to that which obtains universally at other refracting surfaces; for as, in other cases, the ratio is given between the sine of incidence and sine of refraction, (or ordinate of the spherical undulation propagated,) so, in the Iceland crystal, the ratio betweer the sine of incidence and ordinate of refraction (in any one section of the spheroidical undulation) is a given ratio."

As this system is wholly inconsistent with light as a chemical principle, and, we think, with its other phænomena, we shall not enlarge on it. Better arguments than have been hitherto offered in favour of Euler's hypothesis must be adduced, before we can attend minutely to the applica


'XIV. An Account of some Cases of the Production of Colours, not hitherto described. By Thomas Young, M. D. F.R.S. F.L.S. Professor of Natural Philosophy in the Royal Institution.'

We find it impossible to analyse the present article with any tolerable success. It depends also on Euler's theory. The cases of colours before us arise from those of fibres, and of mixed plates; but many of the facts appear to us to be explicable on the principles of other systems.

We cannot conclude this volume without exceeding the space to which we must confine ourselves, as M. Prevost's paper alone would detain us too long. We shall return to it very soon.

(To be continued.)

ART. III. The Works of Virgil, translated into English Verse by Mr. Dryden. A new Edition, revised and corrected by John Carey, LL. D. 3 Vols. δύο. 11.78. Boards. Vernor and Hood.


IT is an ample proof of the intrinsic excellence of Dryden's translation, that, notwithstanding the variety of versions of the Roman bard, which either in whole or in part have since been offered to the public, and the advantages which the different translators have enjoyed, as well from his defects as his merits-he has hitherto never been supplanted. If he have not always maintained a pre-eminence, he has, at least, never sunk below the level of his antago nists: he has never ceased to be treated with venerationoccasionally, indeed, with idolatry. Yet the translation of Dryden was ushered into the world under circumstances the most discouraging and unpropitious. The veteran poet had exceeded his grand climacteric when he first published his proposals to finish it in three years: he became extremely indolent for the first twelvemonth of the period to which he had confined himself, and can scarcely be said to have made even a beginning; and the natural consequence was, that he was compelled to outvie even Lucilius himself, in rapidity of composition-stans pede in uno-and to trust to the printer to correct the errors both of the copy and the press. Hence few publications have been more disfigured with inaccuracies of every description, than the first edition of this version, which bears the date of 1697; and, although a new edition was demanded, and made its appearance about a twelvemonth afterwards, the critical hoe was applied with a most lazy hand, and but few of the weeds were removed from the heavily encumbered soil. The translator had already found the work to answer his purpose, and was satisfied with the fame and the profit it had procured him.

These' (observes the present editor) were the only editions printed in Dryden's life-time. The third, published in 1709, is merely a servile though not faithful copy of the second, and was committed to the press without the trouble of ever consulting the first, except once, for the purpose of doing mischief, in Æn. vii, 146, As to the subsequent publications, they plainly appear to have been each copied from the last preceding, as each preserves all the errors of its immediate predecessor, with the addition of a new crop of its own growth.

In speaking thus freely of the past editions, I am far from wishing to insinuate that the present is in all respects perfect: I am suffciently sensible that it is not, and that much yet remains to be done. All, therefore, that I venture to hope from my feeble efforts, is, that the work may, in its present state, be deemed somewhat less.

faulty and more intelligible than it has hitherto appeared. At the end of this advertisement, I quote some of the numerous passages where I have endeavoured to rescue Dryden's lines from the obscurity or nonsense in which they had before been enveloped by typographic inaccuracy. I leave to the reader, whose curiosity may prompt him to compare this with the preceding editions, to discover a much greater number, which, for brevity's sake, I omit to notice. Nor shall I— as policy might perhaps dictate, if I were inclined to magnify petty minutiæ, and claim great praise for small services-select first the grosser blunders, to stand prominent at the head of the phalanx, and more forcibly to arrest the reader's attention. I rather choose to consult his ease and accommodation, by placing them in regular order, as they successively occur in the course of the work, for the sake of facility in referring to them, if he should be so disposed, as he proceeds through the volumes. Neither do I intend (except in one or two instances, where indispensably necessary) to notice any of the much more copious crop of errors which have successively sprouted forth in subsequent editions, without being directly propagated from that of 1698: for, whoever will take the trouble of examination, may easily reap a plentiful harvest of them without my assistance; and it is sufficient for me to observe, in general, that every error of the second edition has been preserved uncorrected in the third, the fourth, &c. &c. to the end of the list.

To quiet the scruples of the English reader, who may perhaps be surprised to find some of the proper names spelled in a manner different from that to which he has hitherto been accustomed, be it observed that I have, throughout the work, adopted the orthography of the learned and accurate professor Heyne, wherever I found it practicable. In acting thus, I do not conceive that I have taken any liberty with Dryden, much less an improper liberty: and so far was I from venturing to alter or even transpose a single word of bis, that, rather than attempt it. I have suffered some names to pass which are materially wrong, as Erymanthus for Erymas (En. ix, 950), Iolas for Eõlus (xii, 769), Phyllis for Galatea (Past. iii, 97), Aunus for the anonymous son of Aunus (En. xi, 1034), Clymene for Clymene (Geo. iv, 488), Thermidon for Thermōdon (Æn. xi, 956).

In the Latin quotations with which Dryden has interspersed his prefaces and notes, I have occasionally been obliged to differ from him, because the text which he used was not every-where so correct as that of the present day; and, besides, quoting sometimes from memory, he gave words that are not to be found in any copies, ancient or modern; a striking instance of which I have noticed in my second remark on the dedication of the Eneïs.

Had the plan of this edition admitted notes at the bottom of the pages, I should have taken the liberty of offering conjectures and observations on many parts of the work which I have, for the present, been obliged to pass over in silence. I have, however, made memorandums of the most material, which I may perhaps take some future opportunity of communicating to the public, if what little I have here done should meet the approbation of the candid and discerning reader.” Advertisement.

No man is, perhaps, better qualified for the laborious task of correcting the text, either of Virgil or Dryden, than Dr. Carey, whose natural inclination, as well as habits of life, have peculiarly capacitated him for verbal criticism; and we rejoice to find that a poet of Dryden's pre-eminent merit has at length fallen into hands so competent to the friendly office of expurgation.

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To the advertisement, whence we have just selected the above extract, is added a Specimen of attempts to correct some of the errors of the first and second editions, which have been copied in all the others hitherto published:' from which, as it will give the reader a fair idea of the acies oculi and indefatigable pains of our industrious editor-and more especially as it will save ourselves the trouble of a very laborious investigation for the same purpose-we shall transcribe a few passages*.

Georgic iii, 45.

Next him, Niphates, with inverted urn, And dropping sedge, shall his Armenia mourn. Dryden unquestionably wrote "drooping."

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Georgic iv, 305.

And grandsires' grandsons the long list contains.

No very long list is requisite to furnish the grandsons of grandsires. The petty isle, which harboured no other human being than Robinson Crusoe and his man Friday, contained at that moment the grandsons of grandsires. But Virgil's expression includes at least six generations" avi numerantur avorum," i. e. as I have printed the line, and as, no doubt. Dryden wrote it

And grandsires' grandsires the long list contains.

Georgic iv, 352. (first edit.)

.... Lurking lizards often lodge by stealth Within the suburbs, and purloin their wealth. And worms, that shun the light, a dark retreat

Have found in combs, and undermin'd the seat.

Agreeably to a direction given in the errata to the first edition, that of 1698 exhibits the third line thus

And lizards shunning light, &c.

This alteration I have not adopted, being fully convinced that it is the offspring of an oversight on the part either of the author or the printer: for Dryden, after having translated" stellio" lizard in the first line, could never have thought of again introducing hazard in the third, as

Every quotation, not otherwise marked, is the same in both the first and secor d' editions.

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