directions, still there are particular quarters from which they proceed in the greatest number, and especially, that more have been observed to "enter our system by the sign of Libra and about Spica Virginis, than by all the other parts of the heavens."1 In connection with this fact, it is necessary also to direct the reader's attention to one of Sir Wm. Herschel's papers, where it will be seen that this point is in the immediate neighbourhood of those very places, where the greatest abundance of nebula has been found, "beginning, as may be seen in Mr. Bode's excellent Atlas Cælestis, over the tail of Hydra, and proceeding to the southern wing, the body, and northern wing of Virgo."2 I shall refrain from all comment upon these facts, as I proceed; and reserve my inferences from them till I have taken a general view of the whole. 2. The different degrees of consolidation observable in comets are prominent subjects for consideration. These are evinced not only by the variety of the forms in which they appear to us, but also by the changes which those forms continually undergo. In this respect they may be reduced to three classes-viz. telescopic comets3-those with tails-and those without tails. Those of the first class are generally so remote, that few of them are susceptible of accurate observation, and little can be said respecting them with any degree of certainty. The appearance which they most commonly present, resembles "a collection of vapors condensed about their centre," without any visible nucleus, and encircled by a luminous haze or coma, of from 5′ to 8′ in diameter, and of an irregular round form. The facts supplied by them are so scanty and unimportant that the only material 1 See M. Azout's remarks on the Phil. Trans. abridged to 1700, p. 437. 3 Sir. Wm. Herschel. Phil. Trans for 1795, p. 60. "A great number of telescopic comets have been observed, and a far greater number still are probably much too small for being noticed by the most diligent searchers after them. Those six, for instance, which my sister has discovered, I can from observation affirm had not the least appearance of any solid nucleus, and seemed to be a mere collection of vapors, condensed about a centre. Five more that I have also observed, were nearly of the same nature." Lalande in his history of Astronomy for 1806, (Mag. Ency. Fev. 1807, p. 354.) gives the following description of the comet discovered by M. Pons. "Cette cométe etoit très petite, informe, sans noyau sensible, presque aussi loin du soleil que la terre." Sir. Wm. Herschel. again (Phil. Trans. for 1807, p. 266) says, "Out of 16 telescopic comets which I have examined, 14 have been without any visible solid body in their centre, and the other two had a very ill-defined small central light, which might perhaps be called a nucleus, but did not deserve the name of a disk." circumstance elicited is, that they exhibit a separate stage of consolidation, the nature of which can only be inferred from the relation which its phenomena bear to those of the other two classes. Indeed they might have been ranked with those comets which are without tails, but that a marked distinction exists between them from the circumstance of their shewing no solid nucleus or disk. It is therefore to the other two classes that we must look for those more minute particulars by which alone we can hope to form any correct views of the nature and construction of these bodies; and while pursuing this inquiry, we shall derive much useful information and important assistance from the observations of Sir. Wm. Herschel on the three comets of 1807, 1811, and 1812.4 In no other instances have any of these bodies been surveyed with such powerful instruments, nor have such precise and accurate details been collected on any former occasions. The comet of 1811 was particularly favourable to these observations. So brilliant an object had never before been investigated by the heightened powers of modern telescopes, or analysed by the more discriminating tests of modern science; and the facts which it has furnished are calculated to establish clearer and more rational ideas, than any previous view of the subject had ever suggested. From these observations it appears, that what is generally termed the head of a comet, consists of a comparatively small nucleus, solid and intensely bright, surrounded by an extensive luminous coma; that this is encircled by a transparent atmostphere; and the whole enveloped in the materials of which the tail is composed. But the respective proportions of these separate parts varied exceedingly, not only in each of these comets, but even in different situations of the same comet. In all of them the tail expanded considerably as they approached the sun, and gradually vanished as they retired from him, so that, in opposite stages of their passage, the same bodies exhibited the appearances peculiar to two distinct classes. The general connexion between them which this circumstance indicates is so close, that the classification, here adopted, cannot be applied to the bodies themselves, designating the effects of any inherent and permanent qualities, but is merely descriptive of the variety of appearance which they occasionally present. For it is evident from this circumstance, 4 Phil. Trans. for 1808, p. 153, and for 1812, pp,119 and 229. that those comets which are without tails, have most probably been attended by them in earlier stages of their progress, or possibly might still exhibit them in other situations. But the influence of the solar beams in producing or enlarging the tails of comets is far from being uniform in the change effected at equal distances; "the comet of 1807 came within 61 millions of miles of the sun, and its tail covered an extent of 9 millions; that of 1811 was 97 millions of miles distant, but its tail was 100 millions long." In that of 1812, "the tail was formed by an extremely faint light in opposition to the sun, which the light of the moon rendered invisible." This was the appearance which it presented just before and after its perihelion passage, as at other times it resembled " a planet seen through an atmosphere of haziness." It is remarkable also that in these three instances the extent of the tail was in an inverse ratio to the solidity of the nucleus. In the comet of 1811, which spread its blazing train over so large a portion of the heavens, the bright point which constituted the solid or planetary part of this body had a diameter of only 428 miles, while the head or unsubstantial coma, in which it was contained, extended over 127,000 miles. But that of 1812, in which no tail scarcely was visible, consisted almost entirely of a large solid nucleus, the diameter of which Sir Wm. Herschel computed to be not less than 2637 miles; and from the faintness of the chevelure by which it was encircled, he concluded that "its physical construction approached nearly to a planetary condition." From the phenomena observed in these two instances we may collect the important fact, that the growth of the nucleus seems to arise from the consolidation of the lighter substances in which it is enveloped; and that as it advances in maturity it absorbs the more rarified materials of which the tail is composed. The degree of expansion produced by the heat of the solar rays in this luminous train indicates therefore the extent of the solidity, to which the principal or central mass has attained. Estimating by this scale the actual condition of the numerous comets that pass before us, we find them to be so infinitely varied as to prove most incontrovertibly the different stages of their consolidation. Sir William Herschel's view of this progress is clearly stated in the following comparison of the three comets, the phenomena of which so fully justify these inferences. "The comet of 1812 was of such a construction, as to be little more affected by a perihelion passage than a planet would have been; this may be ascribed to its very advanced state of consolidation. That of 1807 was more affected, and, although considerably condensed, shewed clearly that it conveyed a great quantity of nebulosity to the perihelion passage. That of 1811, with little solidity, contained a most abundant portion of nebulous matter, on which, in its approach to the perihelion, the action of the sun produced those beautiful phenomena, which afforded such favourable opportunities for critical observation."5 SARAGOSSA. SARAGOSSA (properly Zaragoza) sustained two sieges in the early part of the Peninsular war. In the last, surrounded by a most powerful French army, the broken raw levies of Arragon, aided by the whole of the citizens, repelled many assaults, endured an unintermitted bombardment, and a war of mines which destroyed two thirds of the city, until fifty thousand corpses, (victims of famine, pestilence, and the sword,) encumbered the streets of the devoted town; the wretched remains of the garrison, reduced to 2,800 men, then marched out as prisoners, leaving 16,000 of their fellow-citizens sick and wounded in the shattered hospitals. Zaragoza!-thy fame shall for ages endure ! Of Spaniards the glory and tomb Though thy streets have been trodden by footsteps impure Yes!-thy name is immortal!—the despot's accurst! Spain in thee shall rejoice evermore, In vain were thy palaces levelled in dust, Their defenders laid low in their gore! Oh! who would not gladly have yielded this life, With all wealth or power ever gave, To have stood by thy sons, in their last glorious strife, And with them, died the death of the brave! 5 Phil. Trans. for 1812, pp. 236, 237. TALES OF MOUSEHOLD HEATH. EXTRACT I-CONTINUED. SUCH was the substance of the traditions that for many ages had been preserved in this family, successive generations of which had been the solitary tenants of this retired spot. The moon, which was just rising at the commencement of the narrative, was now brightly shining in the heavens, and gave warning of the silent and insensible flight of time; we proceeded homewards, having engaged the countryman to meet us soon after sun-rise the next morning, and assist us in the prosecution of our enquiry. As we crossed the heath the adventure of the evening furnished abundant materials for conversation; had our minds been less strongly fortified against the influence of superstition, the hour and the scene might have made converts of us both. Nature, in her veil of moonlight, always lovely, throws at that season over the lonely heath a charm, that makes its solitudes a real fairy-land-the birth-place of romance—the home of gentle elves, and airy spirits' haunt. The soft, mild radiance that invests all heaven and earth but half displays the objects on which it reposes, and peoples the dim horizon with indistinct and shadowy forms; excited fancy gifts them with substance, shape, and faculty; and in her wayward dreams converts the clouds that sail athwart the dark blue sky into floating cars, by which the genii of distant orbs descend to visit our sublunary world. Against such impressions we were armed by reason, reflection and experience; but we felt how pardonable was the facility with which the human mind yielded to them in the twilight dawn of knowledge; and from these considerations, as from all the occurrences of the evening, my companion drew fresh arguments in support of the theory to which I have already adverted. " I have never yet been able," said he, "to convince you, that the fables of superstition are not the mere gratuitous and unfounded inventions of dark and barbarous ages. Are you not aware that such an opinion attributes to the men of those rude, unlettered times a portion of talent at least equal to what we find among our more civilized and better educated contemporaries? Is there not in the earliest supernatural machinery more ingenuity, more |