and pointed out the advantages which such a method of analy sis would possess. Professor Wheatstone, Mr. Swan, Sir David Brewster, and Professor W. Allen Miller in our own country, and Ångström, Plücker, Masson and others on the Continent, have likewise contributed to our knowledge of this subject; but whatever may have been done by others for the establishment of the new method, it must be admitted that the names of Bunsen and Kirchhoff will justly go down to posterity as the founders of the Science of Spectrum Analysis; for they established it on a firm scientific basis, by applying to it the modern methods of exact research.

For the purpose of obtaining the peculiar spectra of iron, platinum, copper, and most of the other metals, these metals must be exposed to a much higher temperature than that of the gas flame, to which they impart no color. This high temperature is best attained by the use of the electric spark. So great, indeed, is the heat developed by this agent, that a single electric discharge passed through a gold wire dissipates the metal at once in vapor. Our illustrious Faraday-the founder of so many branches of electrical science-first showed that the electric spark was produced by the intense ignition of the particles composing the poles; and Professor Wheatstone proved that if we look at the spark proceeding from two metallic poles, through a prism, we see spectra containing bright lines which differ according to the kind of metal employed. "These differences," said Wheatstone, writing in 1834, "are so obvious, that any one metal may instantly be distinguished from others by the appearance of its spark; and we have here a mode of discriminating metallic bodies more ready than a chemical examination, and which may hereafter be employed for useful purposes. This has, indeed, turned out to be a true prediction.

The large number of bright lines which are seen in the spark spectrum are not all caused by the glowing vapor of the metal forming the poles; a portion of them proceed, as Ångström first pointed out, from the particles of gas or air, through which the spark passes, becoming luminous also, and emitting their own peculiar light. Thus, if we examine the spectrum of an electric spark passing from two iron poles in the air, we see at least three superimposed spectra, one of the

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SPECTRUM ANALYSIS.

iron, one of the oxygen, and a third of the nitrogen of the air. By help of a little mechanical device, it is easy to distinguish between the air lines and the true metallic lines, and in this way to detect the various metals. So certain and accurate is this method that Professor Kirchhoff has, without difficulty, been able to detect and distinguish the presence of minute traces of the rare metals Erbium and Terbium, as well as Cerium, Lanthanum, and Didymium, when they are mixed together; a feat which the most experienced analyst would find it almost impossible, even after the most lengthened and careful investigation, to accomplish with the older methods.

In endeavouring to form an idea of the present and future bearings of the science of spectrum analysis as applied to the investigation of terrestrial matter, we must remember that the whole subject is as yet in its earliest infancy; that the methods of research are scarcely known; and that speculations, as to the results which further experiments will bring forth, are therefore, for the most part, idle and premature.

So long ago as 1815, Fraunhofer made the important observation, that the two bright yellow lines, which we now know to be the sodium lines, were coincident with, or possessed the same degree of refrangibility as, two dark lines in the solar spectrum, called by Fraunhofer the lines D. A similar coincidence was observed by Sir David Brewster, in 1842, by the bright red line of potassium and a dark line in the solar spectrun called Fraunhofer's A. The fact of the coincidence of these lines is easily rendered visible if the solar spectrum is allowed to fall into the upper half of the field of our telescope whilst the sodium or potassium spectrum occupies the lower half. The bright lines produced by the metal, as fine as the finest spider's web, are then seen to be exact prolongations, as it were, of the corresponding dark solar lines."

We do not think we can give our readers a more clear and succinct account of the development of this great discovery than by quoting from Kirchhoff's admirable memoir the following passage:

"As soon as the presence of one terrestrial element in the solar atmosphere was thus determined, and thereby the existence of a large number of Fraunhofer's lines explained, it seemed reasonable to suppose that other terrestrial bodies occur there, and that, by exerting their absorptive power, they

For it

may cause the production of other Fraunhofer's lines. is very probable that elementary bodies which occur in large. quantities on the earth, and are likewise distinguished by special bright lines in their spectra, will, like iron, be visible in the solar atmosphere. This is found to be the case with calcium, magnesium, and sodium. The number of bright lines in the spectrum of each of these metals is indeed small, but those lines, as well as the dark lines in the solar spectrum with which they coincide, are so uncommonly distinct that the coincidence can be observed with great accuracy. In addition to this, the circumstance that these lines occur in groups renders the observation of the coincidence of these spectra more exact than is the case with those composed of single lines. The lines produced by chromium, also form a very characteristic group, which likewise coincides with a remarkable group of Fraunhofer's lines hence, I believe that I am justified in affirming the presence of chromium in the solar atmosphere. It appeared of great interest to determine whether the solar atmosphere contains nickel and cobalt, elements which invariably accompany iron in meteoric masses. The spectra of these metals, like that of iron, are distinguished by the large number of their lines, but the lines of nickel, and still more those of cobalt, are much less bright than the iron lines, and I was therefore unable to observe their position with the same degree of accuracy with which I determined the position of the iron lines. All the brighter lines of nickel appear to coincide with dark solar lines; the same was observed with respect to some of the cobalt lines, but was not seen to be the case with other equally bright lines of this metal. From my observations I consider that I am entitled to conclude that nickel is visible in the solar atmosphere; I do not, however, yet express an opinion as to the presence of cobalt. Carium, copper and zinc appear to be present in the solar atmosphere, but only in small quantities; the brightest of the lines of these metals correspond to distinct lines in the solar spectrum, but the weaker lines are not noticeable. The remaining metals which I have examined— viz., gold, silver, mercury, aluminium, cadmium, tin, lead, antimony, arsenic, strontium, and lithium-are, according to my observations, not visible in the solar atmosphere." -Edinburgh Review.

(From a Cambridge Prize Pocm, 1819.)
The hour is come. E'en now the sulph'rous cloud
Involves the City in its fun'ral shroud,
And far along Campania's azure sky
Expands its dark and boundless canopy.

The Sun, tho' throng'd on heaven's meridian height,
Burns red and rayless thro' that sickly night.
Each bosom felt at once the shudd'ring thrill—
At once the music stopp'd-the song was still.
None in that cloud's portentous shade might trace
The fearful changes of another's face :

But thro' that horrid stillness each could hear
His neighbor's throbbing heart beat high with fear.
A moment's pause succeeds. Then wildly rise
Grief's sobbing plaints and terror's frantic cries.
The gates recoil; and tow'rds the narrow pass
In wild confusion rolls the living mass.

Death, when thy shadowy sceptre waves away
From his sad couch the pris'ner of decay
Tho' friendship view the close with glist'ning eye,
And love's fond lips imbibe the parting sigh,
By torture rack'd, by kindness soothed in vain,
The soul still clings to being and to pain:
But when have wilder terrors clothed thy brow,
Or keener torments edged thy dart than now,
When with thy regal horrors vainly strove
The laws of Nature and the power of Love?
On mothers, babes in vain for mercy call,
Beneath the feet of brothers, brothers fall.
Behold the dying wretch in vain upraise
Tow'rds yonder well-known face the accusing gaze;
See, trampled to the earth, the expiring maid
Clings round her lover's feet, and shrieks for aid.
Vain is the imploring glance, the frenzied cry;
All, all is fear;-To succor is to die-
Say ye how wild, how red, how broad a light
Burst on the darkness of that mid-day night,
As fierce Vesuvius scatter'd o'er the vale
His drifted flames and sheets of burning hail,
Shook hell's wan light'nings from his blazing cone,
And gilded heaven with meteors not its own?

The morn all blushing rose; but sought in vain
The snowy villas and the flow'ry plain,
The purple hills with marshall'd vineyards gay,
The domes that sparkled in the sunny ray.
Where art or nature late had deck'd the scene

With blazing marble or with spangled green,
There, streak'd by many a fiery torrent's bed,
A boundless waste of hoary ashes spread.

-

Along that dreary waste where lately rung
The festal lay which smiling virgins sung,
Where rapture echoed from the warbling lute,
And the gay dance resounded, all is mute.-
Mute-Is it Fancy shapes that wailing sound
Which faintly murmurs from the blasted ground?
Or live there still, who, breathing in the tomb,
Curse the dark refuge which delays their doom,
In massive vaults, on which th' incumbent plain
And ruin'd City heap their weight in vain?
Oh! who may sing that hour of mortal strife,
When Nature calls on Death, yet clings to life?
Who paint the wretch that draws sepulchral breath,
A living pris'ner in the house of Death?

Pale as the corpse which loads the fun'ral pile,
With face convulsed that writhes a ghastly smile,
Behold him speechless move with hurried pace,
Incessant, round his dungeon's cavern'd space,
Now shriek in terror, and now groan in pain,
Gnaw his white lips, and strike his burning brain,
Till Fear o'erstrain'd in stupor dies away,
And Madness wrests her victim from dismay.
His arms sink down; his wild and stony eye
Glares without sight on blackest vacancy.

He feels not, sees not; wrapp'd in senseless trance
His soul is still and listless as his glance.
One cheerless blank, one rayless mist is there,
Thoughts, senses, passions, live not with despair.
Haste, Famine, haste, to urge the destined close,
And lull the horrid scene to stern repose.
Yet ere, dire Fiend, thy ling'ring tortures cease,
And all be hush'd in still sepulchral peace,
Those caves shall wilder, darker deeds behold
Than e'er the voice of song or fable told,
Whate'er dismay may prompt, or madness dare,
Feasts of the grave, and banquets of despair.-
Hide, hide the scene! and o'er the blasting sight
Fling the dark veil of ages and of night.

Go, seek Pompeii now-with pensive tread
Roam thro' the silent city of the dead.
Explore each spot, where still, in ruin grand,
Her shapeless piles and tott'ring columns stand;
Where the pale ivy's clasping wreaths o'ershade
The ruin'd temple's moss-clad colonnade,
Or violets on the hearth's cold marble wave,
And muse in silence on a people's grave.