7 feet diameter, and at its extremities, 6 feet. The telescope lies between two stone walls, about 71 feet from north to south, about 50 feet high, and about 23 feet asunder. These walls are as nearly as possible parallel with the meridian.

"In the interior face of the eastern wall, a very strong iron arc, of about 43 feet radius, is firmly fixed, provided, however, with adjustments, whereby its surface facing the telescope may be set very accurately in the plane of the meridian—a matter of the greatest importance, seeing that by the contact with it of rollers attached to one extremity of a quadrangular bar, which slides through a metal box fixed to the under part of the telescope tube, a few feet from the object end of the latter, whilst its other extremity remains free, the position of the telescope in the meridian is secured, or any deviation from it easily determined, for on this bar lines are drawn, the interval between any adjoining two of which corresponds to one minute of time at the equator. The tube and speculum, including the bed on which the latter rests, weigh about 15 tons.

"The telescope rests on a universal joint, placed on masonry, about 6 feet below the ground, and is elevated or depressed by a chain and windlass; and, although it weighs about 15 tons, the instrument is raised by two men with great facility. Of course, it is counterpoised in every direction.

"The observer, when at work, stands in one of four galleries, the three highest of which are drawn out from the western wall, whilst the fourth, or lowest, has for its base an elevating platform, along the horizontal surface of which a gallery slides from wall to wall, by machinery within the observer's reach, but which a child may work.

"When the telescope is about half an hour east of the meridian, the galleries hanging over the gap between the walls, present to a spectator below an appearance somewhat dangerous; yet the observer, with common prudence, is as safe as on the ground, and each of the galleries can be drawn from the wall to the telescope's side so readily, that the observer needs no one else to move it for him.

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The telescope lying at its least altitude can be raised to the zenith by the two men at the windlass in six minutes; and so manageable is the enormous mass, that, give me the right ascension and declination of any celestial object between these points, and I will have the object in the field of the telescope within eight minutes from the first attempt to raise it.

"When the observer has found the object, he must at present follow it by rack-work within his reach. As yet, it has no equatorial motion, but it very shortly will, and at no very distant day clock-work will be connected with it, when the observer, if I mistake not, will, whilst observing, be almost as comfortable as if he were reading at a desk by his fireside.”

It commands an immense field of vision, and it is said that objects as small as one hundred yards cube can be observed at a distance of 240,000 miles by it in the moon, so that it may be expected that our satellite will speedily become well known to us

By the aid of this mighty instrument, what astronomers have before called nebula, on account of their cloud-like appearance, have been discovered to be stars or suns, with planets moving round them, like those which revolve round our own sun. In the constellations Andromeda and the sword-hilt of Orion, both of which are visible to the naked eye, these cloud-like patches have been seen as clusters of stars. Professor Nichol, in speaking of these discoveries, says, "What mean those dim spots which, unknown before, loom in greater and greater numbers on the horizon of every new instrument, unless they are gleams it is obtaining, on its own frontier, of a mighty infinitude beyond, also studded with glories, and unfolding what is seen as a minute and subservient part? Yes-even the six-feet mirror, after its powers of distinct vision are exhausted, becomes, in its turn, simply as the child gazing on these mysterious lights with awful and hopeless wonder. I shrink below the conception which here-even at this threshold of the attainable-bursts forth on my mind. Look at a cloudy speck in Orion, visible, without aid, to the welltrained eye; that is a stellar universe of majesty altogether transcendent, lying at the verge of what is known. And if any of these lights from afar, on which the six-feet mirror is now casting its longing eye, resemble in character that spot. the systems from which they come are situated so deep in space that no ray from them could reach our earth until after travelling through the intervening abysses, during centuries whose number stuns the imagination. There must be some regarding which that faint illumination informs us, not of their present existence, but only that assuredly they were, and sent forth into the infinite the rays at present reaching us, at an epoch further back into the past than this momentary lifetime of man, by at least thirty millions of years!"

"When we consider the successive steps of Lord Rosse's progress," says a writer in the Review we have before named,

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we can scarcely doubt that with his hands so skilful, and his head so stored with the chemistry of fusion, and the physics of annealing, lenses of flint and crown glass may yet be executed of gigantic magnitude. In cherishing these high expectations we have not forgotten that the state of our atmosphere must put some limit to the magnifying power of our telescopes. In our variable climate, indeed, the vapours, and local changes of temperature, and consequent inequalities of refraction, offer various obstructions to the extension of astronomical discovery. But we must meet the difficulty in the only way in which it can be met. The astronomer cannot command a thunder-storm to cleanse the atmosphere, and he must, therefore, undertake a pilgrimage to better climates, to Egypt or to India, in search of a purer medium; or even to the flanks of the Himalaya and the Andes, that he may erect his watch-tower above the grosser regions of the atmosphere. In some of these brief but lucid intervals which precede or follow rain, when the remotest objects present themselves in sharp outline and minute detail, discoveries of the highest value might be grasped by the astronomer. The revolution of a nebula, the direction of a double star, the details of a planet's ring, the evanescent marking on its disc, or perhaps the display of some of the dark worlds of Bessel, might be the revelations of a moment, and would amply repay the transportation of a huge telescope to the shoulder or to the summit of a lofty mountain.

"In looking back upon what the telescope has accomplished; in reckoning the thousands of celestial bodies which have been detected and surveyed; in reflecting on the vast depths of ether which have been sounded, and on the extensive fields of sideral matter out of which worlds and systems of worlds are forming, and to be formed-can we doubt it to be the Divine plan that man shall yet discover the whole scheme of the visible universe, and that it is his individual duty, as well as

the high prerogative of his order, to expound its mysteries and develop its laws. Over the invisible world he has received no commission to reign, and into its secrets he has no authority to look. It is over the material and the visible that he has to sway the intellectual sceptre; it is among the structures of organic and inorganic life that his functions of combination and analysis are to be chiefly exercised. Nor is this task unworthy of his genius, or unconnected with his destiny. Placed upon a globe already formed, and constituting part of a system already complete, he can scarcely trace, either in the solid masses around him, or in the forms and movements of the planets, any of those secondary causes by which these bodies have been shaped and launched on their journey. But in the distant heavens, where creation seems to be ever active, where vast distance gives us the vision of huge magnitudes, and where extended operations are actually going on, we may study the cosmogony of our system, and mark, even during the brief span of human life, the formation of a planet in the consolidation of the nebulous mass which surrounds it."