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Perhaps the English language can boast few inftances of defcriptive poetry, enlivened with a happier variety of imagery, than the fanciful echo in the Poem infcribed to Joanna. The lady's laugh, to be fure, is loud, but it is not unpleafing.

When I had gazed perhaps two minutes' space,
Joanna, looking in my eyes, beheld

That ravifhment of mine, and laugh'd aloud.
The rock, like fomething ftarting from a fleep,
Took up the lady's voice, and laugh'd again:
That ancient woman*, feated on Helm-crag,
Was ready with her cavern; Hammar-Scar,
And the tall fteep of Silver-How fent forth
A noife of laughter; fouthern Loughrigg heard,
And Fairfield anfwered with a mountain tone :
Helvellyn far into the clear blue sky

Carried the lady's voice;-old Skiddaw blew
His fpeaking trumpet ;-back out of the clouds
Of Glaramara fouthward came the voice;

And Kirkftone tøfs'd it from his mifty head." P. 185.

1

But the most fingular specimens of unpretending, yet irrefiftible pathos, are the two Songs, p. 50 and 52. In artleffnefs, they ftrongly remind us of Burns; but perhaps go beyond him in delicacy. As they have a fecret connection, we fhall infert both.

"Strange fits of paffion I have known,
And I will dare to tell;

But in the lover's ear alone,

What once to me befel.

When the I loy'd was ftrong and gay,

And like a Rofe in June,

I to her cottage bent my way,
Beneath the evening moon.

Upon the moon I fix'd my eye,
All over the wide lea;

My horfe trudg'd on, and we drew nigh,
Thofe paths fo dear to me.

And now we reach'd the orchard plot,
And, as we climb'd the hill,
Towards the roof of Lucy's cot,
The moon defcended still.

9.

"On Helm Crag, that impreffive fingle mountain at the head of Grafmere, is a rock which, from moft points of view, bears a ftriking refemblance to an old woman cowering. Clofe by this rock is one of thofe fiffures or caverns, which, in the language of the country, are called Dungeons. The other mountains either immediately surround the vale of Grafmere, or belong to the fame clufter."

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When the art of poetry has been long cultivated among a polithed people, and brought to a state of great refinement, the natural operation of an ill-judged ambition, to excel even those who have moft fuccefsfully adorned the language, leads writers either to employ an affected and over-laboured style, or, at least, to keep always upon the high ftilts of elegance, to the exclufion of Nature and Simplicity. In fuch a state of the poetic art, that man may be confidered as a public benefactor, who, with talents equal to the task, which is arduous, recals attention to the more natural ftyle, and fhows what may be effected by fimple language, expreffive of human paffions, and genuine, not artificial feelings. In this character, Mr. Wordfworth appears; and appears with a fuccefs, to which we could by no means refufe our approbation. We will not deny that fometimes he goes fo far in his purfuit of fimplicity, as to become flat or weak; but, in general, he fets an example which the full-dreffed poet of affectation might with, but with in vain, to follow. He would correct Mr. W. as the dancingmafter of Hogarth would correct the attitude of Antinous.

*The title of the Poems is, in fome degree, objectionable; for what Ballads are not Lyrical? Befides, there are many compofitions in blank verfe, not at all Lyrical.

ART.

ART. VII. Philofophical Tranfuctions of the Royal Society of London, for the Year 1800. Part II. 4to. 298 pp. The Two Parts 11. 5s. 6d. Elmfly.

XII. On double Images caufed by Atmospherical Refraction. By, William Hyde Wollafton, M. D. F. R. S.

THE

HE refractive property of the atmosphere has often been obferved to deviate from its more ufual mode of acting, and several instances are mentioned in former volumes of the Phil. Tranf. and elfewhere, of its having reprefented objects in an inverted pofition, or having formed an inverted image beneath the object itself; but as the cause of such unusual refractive power had not been fatisfactorily explained, Dr. Wollafton endeavoured,

"Ift. To investigate theoretically the fucceffive variations of increafing or decreafing denfity, to which fluids in general are liable, and the laws of the refractions occafioned by them.

"2nd. To illuftrate and confirm the truth of this theory, by experiments with fluids of known denfity.

"And, laftly, to ascertain, by trial upon the air itself, the causes and extent of thofe variations of its refractive denfity, on which the inverfions of objects, and other phænomena obferved, appear to depend."

With this view, Dr. W. very properly expreffes the general laws, which may be applied to all cafes of varying density, in three propofitions, which are as follows.

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Prop. I. If the density of any medium varies by parallel indefinitely thin ftrata, any rays of light moving through it in the direction of the ftrata, will be made to deviate during their paffage, and their deviations will be in proportion to the increments of denfity where they pafs.

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Prop. II. When two fluids of unequal denfity are brought into contact, and unite by mutual penetration; if the denfities at different heights be expreffed by ordinates, the curve which terminates these ordinates, will have a point of contrary flexure.

"Prop. III. If parallel rays pafs through a medium, varying according to the preceding propofition, thofe above the point of contrary flexure will be made to diverge, and thofe below the fame point will converge, after their paffage through it."

Those propofitions are clearly demonftrated, and the demonftrations are illuftrated by means of diagrams; after which, Dr. W. relates a variety of well-contrived experiments, accompanying them with ufeful remarks, and allufions to the phænomena obferved by other perfons (the above-mentioned

diagrams

diagrams and preparations of the experiments are delineated in a plate which follows the paper). But it being not in our power to give a very concife, and at the fame time a fufficiently clear idea of thofe particulars, we shall conclude with an enumeration of the particulars that are explained by them; viz.

"ift. Why air heated by the moderate warmth of the fun's rays, occafions objects to appear doubled and inverted.

2ndly. Why refraction, by a higher degree of heat, gives an additional image, which is not inverted.

3dly. In what ftate of evaporation the increafe of the air's denfity brings diftant objects into view by unufual elevation.

"

4thly. Under what circumftances evaporation may also produce an inverted image lefs elevated.

And it is probable, that the fame reafoning will afford a ready explanation to other varieties of terrestrial refraction that may have been, or may hereafter be obferved."

XIII. Investigation of the Powers of the prifmatic Colours to heat, and illuminate Objects; with Remarks, that prove the dif ferent Refrangibility of radiant Heat. To which is added, an Inquiry into the Method of viewing the Sun advantageously, with Telefcopes of large Apertures, and high magnifying Powers. By William Herfchel, LL. D. F. R. S.

The various experiments which this indefatigable aftronomer has made, at different times, for the purpofe of obferving the fun through telescopes, in a manner that might be lefs hurtful to the eye, and the ufe of differently coloured darkening glaffes, had ftruck him at different times with a remarkable peculiarity of effects; for with fome of thofe darkening glaffes he felt a confiderable fenfation of heat, whilft they tranfmitted but little light; whereas others tranfmitted much light, and fcarce any fenfation of heat.

"Now," fays he, " as in thefe different combinations the fun's' image was alfo differently coloured, it occurred to me, that the prifmatic rays might have the power of hearing bodies very unequally dif tributed among them; and, as I judged it right in this refpect to entertain a doubt, it appeared equally proper to admit the fame with regard to light. If certain colours fhould be more apt to occafion heat, others might, on the contrary, be more fit for vision, by poffeffing a fuperior illuminating power."

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The well-imagined, and well-executed experiments, which Dr. H. made in confequence of this fuppofition, verified his hypothefis, and opened a vaft field of fpeculation and experimental enquiry to the eyes of philofophers. The account of

L

BRIT. CRIT. VOL. XVII, FEB. 1801.

the

the experiments and obfervations which forms this most interesting paper, is arranged under diftinct heads, of which we shall endeavour to give a concise idea.

Experiments on the heating Power of coloured Rays.

The general method of conducting fuch experiments is defcribed by this author in the following manner :

"I fixed," fays he, " a piece of páfteboard in a frame mounted upon a ftand, and moveable upon two centres. In the pasteboard I cut an opening, a little larger than the ball of a thermometer, and of a fufficient length to let the whole extent of one of the prifmatic colours pafs through. I then placed three thermometers upon fmall inclined planes: their balls were blackened with japan ink. Their balls being very fmall, made them of exquifite fenfibility. The scales of all were properly difengaged from the balls.

"I now placed the ftand, with the framed pasteboard and the ther mometers, upon a small plain board; that I might be at liberty to move the whole apparatus together, without deranging the relative fituation of the different parts.

"This being done, I fet a prifm, moveable on its axis, into the upper part of an open window, at right angles to the folar rays; and turned it about till its refracted coloured fpectrum became stationary, upon a table placed at a proper distance from the window.

"The board containing the apparatus was now put on the table, and fet in fuch a manner as to let the rays of one colour pass through the opening in the pafteboard. The moveable frame was then adjuffed to be perpendicular to the rays coming from the prifm; and the inclined planes carrying the three thermometers, with their balls arranged in a line, were fet fo near the opening, that any one of them might eafily be advanced far enough to receive the irradiation of the colour which paffed through the opening, while the reft remained close by, under the fhade of the pafteboard."

This description is accompanied with a delineation of the apparatus.

The conclufion drawn from the refult of the experiments which were performed with this apparatus, and which are particularly ftated in the paper, is, that the heating power of red rays is to the heating power of green rays, as 550 to 242; and that the heating power of red rays is to that of violet rays, as 35 to 10.

Experiments on the illuminating Power of coloured Rays.

The experiments which are related under this head, had two objects in view, namely, to afcertain the power of illuminating which belongs to each particular coloured ray, and their aptnefs for giving distinct vifion.

"I placed," fays Dr. H. " an object that had very minute parts, under a double microscope; and, having fet a prifm in the window,

fo

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