path of the stranger lies as far beyond what had been deemed its extreme confine, as that limit is removed from the sun. The first moment of his "attack" upon Saturn, upon completing the forty-feet reflector, he saw a sixth satellite, and a seventh a month later. But Herschel realised his most surprising results, and derives his greatest glory, from the observation of the sidereal heavens. The resolution of nebula and the Milky Way into an infinite number of stars -the discovery of new nebula of various forms, from the light luminous cloud to the nebulous star—of double and multiple stars of the smaller revolving round the greater in the binary systems;—these were some of his revelations to the world, as night after night, from dewy eve till break of dawn, he gauged the firmament. Caroline Herschel was the constant partner of her brother in his laborious undertakings-submitting to the fatigues of night attendance-braving with him the inclemency of the weather-noting down his observations as they issued from his lips and taking, as the best of all authorities reports, the rough manuscript to the cottage at the dawn of day, and producing a fair copy of the night's work on the ensuing morning. He died in 1822; but she has survived to see the heir of his name recognised by the world as the heir also of his talents and fame. It was one of the conceptions of this remarkable man as bold an idea as ever entered the human mind. that the whole solar system has a motion in space, and is advancing towards a point in the heavens near the star A Herculis. General opinion is now in favour of the idea, that not only the solar but the entire stellar universe revolves around some mighty centre.

The nineteenth century commenced with a fresh ingathering of members into the planetary family. It had been deemed a matter of surprise that the immense interval of about 350 millions of miles between Mars and Jupiter should be void, when only spaces varying from 25 to 50 millions divide Mars, the Earth, and the inferior planets. Keppler had therefore started the conjecture that a planet would be discovered in the vast region between the two former bodies; and thus bring it into something like proportion with the spaces between the latter. This idea was confirmed by a curious relation discovered by Professor Bode of Berlin, that the intervals between the orbits of any two planets is about twice as great as the inferior interval, and only half the superior one. Thus, the distance between Venus and the Earth is double that between Mercury and Venus, and the half of that between the Earth and Mars. Uranus had not been discovered when Bode arrived at this remarkable analogy, but the distance of that planet being found to correspond with the law, furnished a striking confirmation of its truth. The respective distances of the planets may be expressed by the following series of numbers, whose law of progression is evident.

The void in the series between Mars and Jupiter, so convinced the German astronomers of the existence of a planet to occupy it, which had hitherto escaped observation, that a systematic search for the concealed body was commenced. At Lilienthal, the residence of Schroeter, an association of twenty-four observers was formed in the year 1800, for the purpose of examining all the telescopic stars of the zodiac. The opening years of the century witnessed the anticipation substantially realised by the discovery of

four planets-Ceres, Pallas, Juno, and Vesta, revolving round the sun at a mean distance of one hundred millions of miles from Mars, so small as only to be telescopic objects. This discovery we owe to Piazzi, Olbers, and Harding. Some singular features, without parallel in the planetary system, such as their close contiguity, the intersection of their orbits, with their diminutive size, Vesta not being much larger than the Spanish peninsula, led to the surmise that these bodies are fragments of a planet which once revolved in their mean path with a magnitude proportionate to that of its neighbours. The possibility of such a disruption cannot be denied the revolution of the fragments round the sun would follow in obedience to the mechanical laws by which the system is governed; but the point is obviously one of those questions which must remain entirely hypothetical. Next to this addition to the system, the most remarkable astronomical occurrences of the present age, previous to the year 1838, are the November meteors,— the renewed return of Halley's comet, and the determination of the annual parallax of the star 61 Cygni by Bessel. These will come under consideration in future pages, with the important contributions made to science by the great names of the day, Sir John Herschel, Sir James South, Struve, Airy, and Arago.

The progress of Astronomical discovery which has now been hastily traced, reminds us of the obligations we owe to those who have gone before us. While supplied with facts respecting the constitution of the solar universe -the number, forms, magnitudes, distances, and movements of its members upon the general accuracy of which the mind may repose with full satisfaction; the mode of its formation was also grappled with, and a theory presented, derived from the study of the sidereal heavens, which, though now deprived of its basis, was invested with a high degree of probability. The firmament exhibits dimly-luminous appearances, like patches of white cloud, displaying various forms and peculiarities of structure, which are not resolvable into clusters of stars when seen through common instruments, and whose phases seem at variance with the idea of stellar groups indistinct and blended from their remoteness. This nebulous substance, as it has been called in one of its states, resembles a sheet of fog. Under another aspect, it is seen winding, and there seems a tendency towards structure, the material congregating in different places, as if under the influence of a law of attraction. Definite structure appears in other cases generally assuming the spherical form, with great condensation at the centre, like regular stars in the midst of a thick haze. The question was raised, What do such appearances indicate? What do the differences in their character portend? Are the nebulæ tracts of self-luminous matter? Are they void and unmeaning substances in a universe of organisation and order, or are they advancing by a principle of progressive formation to share themselves in that order and organisation? The idea was started, that in these phenomena we have an exhibition of the first state of the now organised bodies of our system, and of their progress to the ultimate conditions of their being, passing from one stage of construction to another under control of the law of gravitation. This is substantially the nebular hypothesis of Laplace and Herschel. It supposed a diffused nebulosity, rotating with the solar nucleus, and, extending beyond the bounds of the farthest planet, to have gradually condensed at the surface of the nucleus, accelerating thereby the solar rotation, and increasing the centrifugal force, by the action of which successive zones were detached, assuming spheroidal masses by the mutual attraction of their particles. The theory enlisted a variety of evidence in its behalf. The fact of the projectile motions of all the planets and satellites taking place from west to east in nearly the same plane of their axical rotation likewise being all in the same direction, and corresponding with that of the solar body — was viewed as an instance of extraordinary coincidence strongly supporting the theory of their common origin in obedience to a common law. The reflection naturally arose, that in the physical and mental constitution

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of our own nature with reference also to the inferior animals, both the feeble and the powerful, the tractable and the untamed-in relation, too, to the vegetable productions of the earth, whether flourishing in green savannahs, or rooted in the clefts of the rock-we have a law of gradual formation now operating, which vindicated the idea from the charge of a vain conceit, that ananalogical law has operated with reference to the earth itself and the various worlds that compose our system. This theory is now merely referred to as a matter of history, its foundations having recently been removed by mightier telescopic power. From the view which has now been taken, it is evidently no doubtful point to us,

"Whether the sun, predominant in heaven,

Rise on the earth, or earth rise on the sun;
He from the east his flaming road begin,
Or she from the west her silent course advance
With inoffensive pace that spinning sleeps
On her soft axle."

How incumbent the duty upon us, then, as we have largely benefited by our predecessors, that, as faithful stewards of their gifts, we should hand them down to posterity with an increase of value! How grand, and yet how simple, those views of the universe, upon the evidence of which we are now invited to gaze! The Sun, a central orb, attended by a stately cortège of planets, forming a system under the empire of law, -a system not unique, but a general type of others as countless as the members of the stellar host, whose front ranks alone come within the range of telescopic vision;-systems, probably, not physically insulated, but bound together by fine relationships, the nature of which, judging from the progress of the past, it is not arrogant to presume, will yet be revealed to the understanding of man! These are not ingenious theories-splendid conjectures, but established facts, and sober anticipations based upon them. To live and learn is the high vocation of humanity, one of the appointed ends which the great Artificer of existence contemplates in its continued series; the generations that are to come improving upon the acquirements of that which now is. Nor can we fix any limit to the growth of knowledge in relation to the physical universe, clear and insurmountable in the present state as are its bounds with respect to the spiritual world. Who can descry a resting point in the wilderness of space? discern a barrier to the range of the creation? Vast as are the regions that have been entered, there are vaster amplitudes unapproached beyond them, towards which the mind may advance in endless progression; often indeed faltering in the pilgrimage beneath the burden of those conceptions of space and magnitude which immensity suggests, but still going onwards.

will infallibly keep the appointment. In countries favoured with a more transparent atmosphere than our own, the day-spring, the commencement of terrestrial nature's diurnal audience with the solar presence, is a scene of great combined beauty and magnificence. Faint rosy-coloured streamers are early indications of the point of sunrise; these rapidly become more distinct, and are followed by resplendent saffron hues, from that of burnished gold at the horizon, to the lighter shades gradually fading upwards into the pure cerulean of the illuminated sky. A recent pilgrim from the Western world to the sacred sites of the East, during his stay at Athens, went to witness the sunrise from the Acropolis, amid the solemn grandeur of its desolations. Seated within the ruins of the Parthenon, commanding a view of the horizon through the columns of the eastern portico, he awaited from the grey dawn the appearance of the orb of day. Gradually the sky became so resplendent in the direction of the advancing luminary, as to render it impossible to determine the precise point where his presence would be revealed. The tops of the northern mountains caught his beams, and some light fleecy clouds seemed changed into liquid gold, as, hovering over mount Hymettus, they met the rays of the sun. At length, the eye encountered the solar glory, lighting up the columns and marbles of the Parthenon with a silvery splendour. It was one of those moments in the life of man, says Robinson, the traveller in question, that can never be forgotten. In our own latitude, the sunrise is a spectacle of surpassing interest and beauty, as viewed from the summit of Snowdon, or from some eminence overlooking the sea, in a propitious state of the atmosphere. The progressive illumination — the variegated colours deepening and brightening that are pencilled on the sky - the growing distinctness of the superficies, whether field or flood-the retreat of mists and vapours glittering in the sunbeams while vanishing before their action;-combine to form a scene of visual beauty which has few parallels in the realms of nature.

This is occa

Light is sensibly transmitted to us while the sun is below the horizon. sioned by the refractive and reflective properties of the atmosphere. By the former, as previously explained, his place in the heavens is raised, and morning and evening, when his lower limb appears to rest upon the horizon, his entire body is actually below it, and would be invisible but for the refraction of his rays. This effect is only produced while his declination does not exceed 33', which is rather more than his greatest apparent diameter. At a further distance from the horizon, the power of refraction is not sufficient to elevate his rays so as to cause their direct transmission to the eye. They are then reflected to us from the upper regions of the atmosphere which receives them, causing the morning and evening twilight, the gradual transition from darkness to light, and from light to darkness. It is owing to the particles of air possessing the property of successively reflecting and re-reflecting the solar light, scattering it in every variety of direction, that all those objects are visible to us in the daytime, which are indirectly situated with reference to the luminary. Without it, the cloudless sky at noon, now so blue and brilliant, would present the blackness of darkness, with the exception of the places occupied by the sun and the stars. The latter would be as visible by day as at midnight, while no object would be perceptible, not receiving the direct sunbeams. It is not impossible but that at midnight, in the hour of the deepest gloom, some of the solar influence may be transmitted to us by an infinite number of reflections, so reduced, however, in its amount and power as to be imperceptible. The period of the sensible reflection of light from the sun, or the twilight, is generally supposed to be confined to his depression eighteen degrees below the horizon. The limit of depression, however, at which there is the greatest observed darkness, varies in different climates. In the torrid zone it has been found to be between sixteen and seventeen degrees; and in France between seventeen and twenty-one. The duration of the twilight is different at every different latitude on the earth, and it varies in the same