impressively great for it, are so just and unassailable as they appear to be. We cannot escape the belief, that the greatness of mere vastness and long duration may be represented in the realm of chemistry and atomics by a not less wondrous greatness; that vastness may be there compensated by energy, and long endurance by swift intensity of change. Nay, to a certain extent it is known that it is so,-known that, while the slow evolving of the star's revolution has failed to make itself sensible to our keenest search, the flower has been born, has lived, died, and been born again; and that these its changes are the aggregate representation of a thousand thousand included and constituent changes.

We have been led to these remarks, which have extended beyond what we at first designed, by observing the very general interest which has been excited by the discoveries of the great Parsonstown telescope. Our whole era has been, beyond most which have preceded it, one in which the physical vastness of the universe has been extended before us. While, above us, the discovery of the double stars, and the long cycles of revolution which pertain to some of them; of the orbitual motion of our sun, and the far longer that must pertain to him; of the parallax of several fixed stars, and the approximative estimate thus afforded us of the distances of his brother suns; and, finally, of the resolvability of the true nebulæ, which has led one cautious observer to estimate rudely that, for the distances of some of these, we cannot assume smaller spaces than such as light would consume millions of years in traversing :-while thus in the heaven above us the indefinite of space and time has been expanding more and more before us, in the earth beneath geology has been detecting the traces of a duration in whose extent the lifetime of man the race dwindles to insignificance, and reading the records of convulsions, to which Lisbon earthquakes and Etna eruptions are but as the overthrow of an ant-hill or the sputter of a rocket. It is with enlarged conceptions of what indefinitude is, that man now gazes up from his spot of earth into the opening and still opening vistas of the heavens, or back from his point of time into the dim abysses of the past of his earth: and he should so gaze with deeper gratitude to Him who has so endowed his spirit; has given to it a life more nearly mirroring, according as the created can mirror, His own infinitude and eternity, than can all physical greatness or physical continuance; and has therein given to it capacity to sustain unburdened all expansion of indefinitude before it, and to dilate in adequate correspondence with all its dilatation. And the era of the Parsonstown telescope will, apart from all its future achievements-and we hope largely from these-long be a memorable one in the history of the observation of the physical

heavens. Its successful construction has solved more than one most important problem with regard to the fabrication of instruments of such power; has enlisted on their behalf mechanical genius of the highest order; and, above all, by removing the most delicate of all the operations connected with them-the polishing of their specula-from the risks and imperfections of manual labour, and entrusting it to the charge of machinery which acts with unerring certainty, it has got rid of the principal difficulty attendant on the construction of instruments of the largest size, and given good ground for hope yet to see even the monster telescope' far surpassed. The first achievement of this noble instrument, has been the removing out of the heavens an assumed form of matter, upon whose existence had been built up some of the most daring physical speculations that ever occupied the human intellect, and which had been called in to lend the powerful aid of its presumed existence to a system of cosmogony, or rather of planetary organisation, in many respects most truth-like, and which to many had become as the assured truth. It resolved the nebulæ, strictly so called. It transformed for us those dim and doubtful specks, which no eye but that of the practised star

*We were a little surprised and somewhat alarmed, to find a preliminary section of Mr. Nichol's work devoted to showing that in Lord Rosse's instrument we have attained the probable limits of telescopic power. As we read on, however, to the reasons upon which he grounds this belief, our alarm rapidly oozed away, though our surprise, with a changed direction, correspondingly increased. These reasons are two. The first has reference to the mechanical difficulties at present attendant on the suspension, &c., of bodies so ponderous as these very large instruments are. Such an objection would scarcely have been advanced as insuperable by the author, if he had considered how the mechanical wonders of one generation are the playthings of the next. The second is a scientific one. We confess we are at a loss to understand it; not because of any obscurity in the apparent statement of it, but because that statement is founded on a misapprehension into which we can scarcely suppose a Professor of Astronomy can have fallen. The objection, as it seems to be stated by Mr. Nichol, is: there is a limit beyond which the magnifying power of the eye-glass in the telescope; or, as he calls it, of the microscope by which the image' presented by the object-glass, or the speculum, is beat out over a larger surface, cannot be increased, without impairing distinctness of vision:' this limit, according to his apparent view, is the limit also of the size and space-penetrating power of the instrument: and he regards it as probable that it has now been attained. We cannot well understand from what law in optics, or what foundation in practice, such a belief should have been inferred. Every telescope, from the child's toy up to the sixty-feet reflector, has for itself such a limit of power and search. The fact has been known almost since the telescope itself came to be known, and the remedy has been constantly applying: that remedy being the very thing which is here announced, on the assumed ground of such a limit, to be impracticable or useless, increasing the diameter and, in conformity with a well known principle in optics, the focal length of the object-glass or the speculum, when, with a lower magnifying power in the eye-glass than the highest which was applicable to the lower instrument, a greater space-penetrating power and larger image of the object is obtained. It must be on other grounds than those which Professor Nichol advances that we accept his conclusion; or believe that, in any direction of the sphere of knowledge, the impassable boundary has been attained.

gazer would ever note, into clusters of suns; and in the process led us forth through spaces to which all heretofore known were near and of little worth. It broke up, too, with a noble recklessness of our amazement, the defined simplicity of form in which more subservient instruments had represented before us these clustering systems, and left us to search out other laws, to which we might conceive their fantastic and capricious arrangements subject. No sphere-like firmaments of suns now remain, wherein it is conceivable that the orbs may sweep on in defined and planetary paths around their centre; no annular masses of worlds, whose orbitual curves, though very complex and strange-seeming, were still to a certain extent definable; and that far firmament which heretofore had appeared as the exact shadow of our own, has now put on an aspect of such magnificent fantasy, that it baffles alike description and representation; and still it, too, has its shadow and likeness among the fantasies which have been revealed.

Before entering into more special detail regarding the discoveries of this powerful instrument, it may be necessary, for the sake of some of our readers, that we should briefly state the views which had been previously entertained with regard to the true nebulæ, and the speculations to which they had given rise, or with which they had become associated.

In addition to the ordinary and clearly defined stars, observers had long been aware of a class of appearances in the heavens distinctly and broadly separated from these. They present themselves, when first reached by the eye or the telescope, as hazy specks or flakes of milky light, of almost every possible variety of form; a very few of them being visible to the unaided eye, but the great majority not coming into view until telescopes of moderate power are employed, and a considerable number requiring instruments of high capabilities. They are confined to no particular quarter of the heavens, but are found diffused irregularly and indiscriminately through them; and are at once distinguished from single stars, whose light is dimmed merely by far withdrawal into space, by the sensible superficial extent they reveal. Under the examination of Sir William Herschel, these milky spots appeared to resolve themselves into two great classes, characterised by peculiarities of aspect which seemed to him utterly irreconcilable with identity of nature. One of these

classes, on telescopic examination, was distinguished as follows. Before the instrument which first descried them, they presented themselves as faint and milky spots, their light resembling that of those delicate flakes of cloud dissolving in the moonlight, so common in our spring and early summer evenings, and seeming rather to melt away at the edges into the surrounding shade,

than abruptly to terminate. On an instrument of higher power being brought to bear upon them, their light, almost invariably with the first excess of power, began to undergo an entire and remarkable change. The milkiness or haziness disappeared, and was replaced by a curdled and less homogeneous light; frequently, though by no means invariably, exhibiting marked condensation towards the centre, thinning away toward the edges or circumference. And as the telescopic power was still further increased, this curdling and breaking up of the nebula became more and more defined, until, at last, distinct light-giving points came into view. The nebula was said to be resolved. Regarding the true nature and internal constitution of the class of appearances thus distinguished, no doubt whatever could be entertained. They were manifestly clusters of stars; not necessarily more crowded together in contiguity than the stars of our own heaven, but the entire and associated mass so far withdrawn into space, that their aggregated light, when the eye or the telescope first caught sight of them, presented only that milky haze which we have attempted to describe. They were firmaments or systems of suns; similar, as to their generic arrangements, to that of which our own sun is a member, and the principal mass of whose stars constitutes the milky way.

After the whole number of these nebulæ, however, had been sifted by this process, and not only those withdrawn which revealed sensible star-points, but likewise all which exhibited the slightest first trace of resolvability, there still remained a very large residuum, which exhibited characters the very opposite of those we have been describing. The milkiness and haze of their light remained to the last unchanged. We may, in the meantime, define the practical result accomplished for us by the telescope to be, the placing us at a point in the heavens so much the nearer the object being examined than without that instrument's aid we are, as its space-penetrating power is high. Now, while some of these nebula were found to yield and give up the secret of their stellar constitution, on the instrument approaching us to half our natural distance from them, or half the distance at which they first presented themselves to our search,-among this second class, not only did all withstand such approaches as this, but on some we could look from a hundredth or a two hundredth of the distance at which they were first descried, and they were found to remain wholly intractable still; to retain unchanged, and without the faintest promise of change, the soft and shadowy aspect with which they at first presented themselves. The outline of their forms became more distinct, and, in general, much extended; their light appeared clearer and brighter, but it ex

hibited no trace of that curdling up or resolution into separate star-points which was presented to us by the other class; it remained perfectly homogeneous under the highest telescopic power which, till within the last two years, was available to us. Two of these nebulæ, for example, are distinctly discernible by the unaided eye; yet to Sir William's four-feet reflector, approaching us to a two hundredth of our natural distance, and even to Lord Rosse's three-feet one-a still more efficient instrument-they exhibited simple extension of form and greater fulness of light, but not only no trace of separate constituent stars, but no beginning appearance, or promise of it,-no trace of that hardening of aspect which began to present itself in the resolvable nebulæ, under the slightest advance of telescopic power beyond that which first brought them into view.

Such were the undoubted facts upon which Sir William Herschel proceeded. Two explanations of the remarkable peculiarities characterising these unresolved nebulæ were admissible; and, so far as we can even yet see, two only. The one assumed that the bodies presenting themselves under these peculiarities of aspect were really identical with the resolvable nebulæ, and that the marked distinction of phenomenal appearance was simply a result of comparative distance: that these also were firmaments of suns, so far removed from us in space, that not only did their aggregated light only reach our earth as a faint and homogeneous haze, but that the abridgment of this distance to a hundredth or less of its original amount, left us still comparatively unbeginning to approach them; farther removed still from them than from the first we were from any known firmamental nebula. There was more than mere immensity of distance to be accounted for. There was visibility at this immensity of distance, which, as to its principal feature, had not become more visible when but a small fraction of the original distance continued to intervene. This first explanation would in the circumstances have been wholly unwarranted and unsupported by facts. It inferred the existence of systems entirely unlike those which were known: their orbs so massed and crowded together; the space occupied by the aggregate of these so vastly surpassing all we had any example of; and the forms assumed by some of these aggregations such entire departures from the prevalent simplicity of firmamental arrangement, as then recognised, and so apparently irreconcilable with subjection to known principles of force and of motion, that there had been direct violation of every principle of inductive science in assuming identity where every recognised feature told of contrariety. Another resource remained: and the alternative it presented,