To satisfy a curiosity that is naturally excited by any thing new, great or uncommon, I tried to obtain all the information I could, connected with the Telescopes I endeavour to describe. To gratify a similar feeling in others, more remote from my opportunities of looking on, I venture to publish an account of what I have seen.

As I am hardy enough to do so without any assistance from, or even the cognizance of the noble projector of those instruments, whose liberality in diffusing his knowledge and wish for its promotion, leave me no uneasiness on this point, so I do not expect to give that information which men of deep research or mathematically close enquiry would desire. There are some particulars which might, perhaps, be more enlarged upon with advantage, but it has been my aim to place before the general reader such an account as will make the manufacture of the Specula, and the mechanism of the Telescopes, as plainly understood as could be expected, without entering with too much tediousness into minute details. I have been as explicit as possible in the history of the compound three foot Speculum, knowing that individuals whose inclination would lead them to construct Specula on a large scale, without possessing the pecuniary advantages of Lord Rosse, will be naturally led to adopt a course the most manageable and economical, and one which does not appear to be the less certain of success.

The rapid sale of the First Edition, together with the many very favorable opinions expressed in reference to it by the Newspaper Press, leads the Author to hope that this work has been presented in an acceptable form. In the present edition he has therefore merely supplied a few trifling omissions which an unavoidable hurry in bringing out the former, occasioned.

In the account of the three-foot Speculum which Lord Rosse published in the Philosophical Transactions for 1840, he speaks of the possibility of one six feet in diameter being cast. It might at that time have been considered as little less than a chimera by those who were not sufficiently acquainted with the experiments that had been made in his Lordship's laboratory, and there were not wanting some who denied altogether the practicability of the design. Various reasons were given why the attempt should be a failure, and many calculations entered into to prove the little benefit to be derived even supposing a perfect casting were obtained—But fortunately others thought differently; the idea had no sooner occurred to Lord Rosse than he determined to put it to the test, and we may say, without flattery, that no absurdity was likely to occupy a mind like his. The attempt has been made, and the result is perfect success.

As yet we cannot say how far it may advance our knowledge of the celestial spheres, or help us to understand more fully the mechanism of the universe; but this at all events is certain, that be the advantage great or small, it is the last step that can be taken to enlarge our acquaintance with those distant bodies, and all that is ever likely to be brought before us will now be seen.

Lord Rosse having satisfied himself by experiments with lenses that the Refracting Telescope could not be much improved, turned his attention to Reflectors; and as the first object of experimenters had always been to increase the magnifying power and light by the construction of as large a mirror as possible, so was it to this point that his Lordship's attention was also directed.

Previous to his experiments, there had not been any instrument constructed, with the exception of Sir W. Herschell's, which had given an opportunity of sufficiently well enjoying the advantage of the Reflecting Telescope; and even of this it has been lately stated, that it possessed but little, if any, practical superiority over others of smaller size.

Since Newton manufactured his Specula until the present day, there have been several opinions both as to the metals to be employed in their construction, and the quantities in which they should be mixed—some have recommended various proportions of tin and copper; some have added arsenic; some silver; some antimony; and others, the three together—the general aim of all the operators being to increase the whiteness, and to diminish the porosity and brittleness of the compound; for the last named property has destroyed a much greater number of Specula than it has allowed to be completed—it is the “asses' bridge” over which few have been fortunate enough to travel.

Returning homewards, through those profound abysses, to whose extremities we have adventured, and leisurely surveying the objects whose number and varieties struck us at first with an absorbing and most natural astonishment, we soon start the enquiry, What are these clusters doing?—What is their internal condition?—What their mechanisms?—And what the nature and affections of the bodies which compose them? It is manifest, that such investigations, in so far as we would rest them on observation, must be confined within our own cluster—the telescope, which has revealed the dim lustre of others, still failing to discriminate the peculiarities of their individual orbs; but if we analyze the system of which we form a part, and become familiar with the mode of its existence, a cautious use of the argument from analogy, will at least darkly illumine the obscurer objects which surround it.

I. In the first place, it is of importance to ascertain whether the stars are individually characterised by the same leading features, or—taking our Sun, which we know best, as a pattern object—whether and how far the distinct orbs of remote space may be accounted to resemble him? The old notion that these luminaries are of no significancy, except as ornaments to the earth, has lost hold, I believe, of all classes of minds, so that, assuming that the stars are also suns, shining like our luminary, of their own perennial virtue, we may step at once to consideration of the second or next higher point of probable resemblance,—are these myriads of suns encircled, like ours, by schemes of subservient planetary worlds?

The disclosures of the telescope are now before us5—the entire perspective of Modern Astromomy. Can we comprehend its wonders? Are its arrangements a fixed thing—a mere passing show—or are they results of a pre-existing state, and germinant of something future? These questions warn me, that again we break new ground, and enter on speculations, perhaps the most adventurous which have yet engaged the reason of Man.

Astronomy has recently been obliged to recognise a Matter—or rather a modification of Matter, wholly distinct from stars—a thin and filmy substance diffused through the stellar intervals, and spreading over regions so immense, that its magnitude or the space it fills, is absolutely inconceivable. It unquestionably becomes us not to admit an element so remarkable, and which, if real, must perform important functions, and materially affect our general views of things—until its claims have undergone the severest scrutiny ; and as I am desirous to convey to you full power of judging for yourself, I will here minutely follow the process of thought, by which Sir, William Herschel—only, however, at a comparatively late period in the course of his researches—was, slowly and almost reluctantly, led to the conviction of its reality.

In his earlier inquiries, Herschel was inclined to consider all the faintly illuminated spots in the heavens, as clusters so remote, that only their general illumination, and no individual object could be seen; and the inference, so far from being constrained, seemed to result from his whole previous experience.

Let us note the exact amount of evidence constituted by the speculations of the foregoing letter, on behalf of the Hypothesis that all existing stellar bodies sprung by virtue of the law of attraction, from the bosom of a chaos similar to the vague masses I have described. In so far as this Hypothesis undertakes to explain the nebulæ, I do not conceive that much of accessible knowledge is now wanting to confirm it; for, the agreement of the forms of the nebular substance with the natural results of the persevering action of gravity, seems almost demonstrated. But it must not be forgotten that there is another correlative and very extensive inquiry which this truth has not touched; The Hypothesis must alsoexplain the stars. If it is the true Cosmogony, and we have at length approached a right theory of the Formation of Things, we should indeed obtain from it a satisfactory idea of the meaning of that curious progression of structure, which so strikingly characterises the Nebulous masses; but it is no less imperative that it exhibit with proper distinctness, how the mass of stars around us, along with their peculiar features and arrangements, might have been evolved, in obedience to known mechanical laws, by the condensation of Nebulæ.