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northern hemisphere. It occupies the constellations Leo, Leo Minor, the body, tail, and hind legs of Ursa Major, the nose of Camelopard, the point of the tail of Draco, Canis Venatica, Coma Berenices, the preceding leg of Boötes, and the head, wings, and shoulder of Virgo, which is the richest part. There is a lesser nebulous region in this hemisphere, but entirely separated from the preceding, which occupies the chest and wing of Pegasus, the constellations Pisces and Andromeda. If we could imagine the ring or zone of the Milky Way to encircle or coincide with the horizon, the great nebulous mass would form a canopy over head, descending down to a considerable distance on all sides, chiefly towards the north pole; and the richest part, which is in Virgo, would then be directly over head in the north pole of the Milky Way, that is in 12h 47m right ascension, and 64° north polar distance.
With the exception of the Magellanic clouds, there is a much greater uniformity in the distribution of the nebula in the southern hemisphere than in the northern. They are separated by spaces of vacuity of greater or less dimensions. One of these barren regions extends for nearly fifteen degrees all around the south pole, and close on its border; the lesser of the Magellanic clouds occurs completely insulated; while the greater Magellanic cloud is in connexion with something approaching to a zone of connected nebulous patches which extends along the back of Doradus, through a portion of Horologium and Eridanus, part of Fornix, and over the paws of Cetus to the equator, where it unites with the nebulous regions of Pisces.
The Magellanic clouds form two of the most striking features in the southern hemisphere; both of these nebulæ are visible to the unassisted eye, being nearly of the same intensity as the brighter portions of the Milky Way; but the smaller is entirely effaced by moonlight, and the larger nearly so. They are altogether unconnected with the Milky Way and with one another. The Nubecula Major is far superior to the Nubecula Minor in every respect, though they are similar in internal structure. The former consists of large tracts and ill-defined patches of irresolvable nebulæ, and nebulosity in every stage of resolution, up to perfectly resolved stars like the Milky Way; and also of regular and irregular nebulæ, properly so called; of globular clusters in every stage of resolvability; and of clustering groups suffi
ciently insulated and condensed to come under the designation of clusters of stars. Of these the nebula known as Lacaille's 30 Doradus is too remarkable to be passed over. It is very large, situate within the Nubecula Major, and consists of an assemblage of nearly circular loops uniting in a centre, in or near which there is a circular black hole. In short, for the number and variety of the objects, there is nothing like this cloud. Within an area of only forty-two square degrees, Sir John Herschel has determined the places, and registered 278 nebulæ and clusters of stars, with fifty or sixty in outlying members immediately adjacent. Even the most crowded parts of the stratum of Virgo, in the wing of that constellation, or in Coma Berenices, offer nothing approaching to it. It is evident, from the intermixture of stars and unresolved nebulosity, which probably might be resolved with a higher optical power, that the nubeculæ are to be regarded as systems sui generis, to which there is nothing analogous in our hemisphere.
Next to the Magellanic clouds the great nebula round ʼn Argûs is one of the most wonderful objects of the southern sky. It is situate in that part of the Milky Way which lies between the Centaur and the body of Argus, in the midst of one of those rich and brilliant masses, a succession of which is so curiously contrasted with the profoundly dark adjacent spaces, and surrounded by one of the most beautiful parts of the southern heavens. Sir John Herschel says: "It would be impossible, by verbal description, to give any just idea of the capricious forms and irregular gradations of light affected by the different branches and appendages of this nebula. Nor is it easy for language to convey a full impression of the beauty and sublimity of the spectacle it offers when viewed in a sweep, ushered in as it is by so glorious and innumerable a procession of stars, to which it forms a sort of climax, justifying expressions which, though I find them written in my journal in the excitement of the moment, would be thought extravagant if transferred to these pages. In fact, it is impossible for any one, with the least spark of astronomical enthusiasm about him, to pass soberly in review with a powerful telescope, and on a fine night, that portion of the southern sky which is comprised between the 6th and 13th degrees of right ascension, and from 146° to 149° of north polar distance; such are the variety and interest of the objects he will encounter, and
such the dazzling richness of the starry ground on which they are represented to his gaze." In that portion of the sky there are many fine double stars-rich starry clusters; the elegant cluster of variously coloured stars round κ Crucis; a large planetary nebula with a satellite star; another of a bright blue colour, exquisitely beautiful and unique; and, lastly, ʼn Argûs η itself, the most extraordinary instance of a variable star in astronomical history.
It frequently occurred, during Sir John Herschel's survey of the southern heavens, that some parts of the sky were noted for deeper blackness than others, and no stars could be seen; it frequently happened that far from the Milky Way, or any large nebula or cluster of stars, there were some indications of very remote branches of the Milky Way, or of an independent sidereal system or systems, bearing a resemblance to such branches. These were indicated by an exceedingly delicate and uniform dotting or stippling of the sky by points of light too small to admit of any one of them being steadily and fixedly viewed, and too numerous to be counted even if possible to view them. The truth of this existence was felt at the moment of observation; but the conviction, though often renewed, was not permanent. The places where these appearances occurred are given, in order that those who wish to verify them may have it in their power. Such is a brief account of a very few of the discoveries contained in Sir John Herschel's great work on the Nebula and other Phenomena of the Southern Hemisphere, a work which will rise in estimation with the lapse of years. No doubt the form and internal structure of many of these nebula will be changed by telescopes of higher power; but as the places of the leading phenomena have been determined, the date of that great work may be regarded as the epoch of nebular time whence the relative changes that take place in the most distant regions of the universe will be estimated for ages to come; and in the inimitable writings of the highly gifted father and son the reader will find these subjects treated of in a style worthy of it and of them. Of late years the excellence of the instruments, and still more of the astronomers, in the foreign observatories, have aided the progress of sidereal astronomy immensely. Nor has it been cultivated with less success in our home and colonial establishments: certainly one of the most remarkable features of the times is the
number of private observatories, built and furnished with the best instruments by private gentlemen, whose zeal has been rewarded by eminent success in all departments of the science. (N. 236.)
So numerous are the objects which meet our view in the heavens, that we cannot imagine a point of space where some light would not strike the eye;-innumerable stars, thousands of double and multiple systems, clusters in one blaze with their tens of thousands of stars, and the nebulæ amazing us by the strangeness of their forms and the incomprehensibility of their nature, till at last, from the limit of our senses, even these thin and airy phantoms vanish in the distance. If such remote bodies shone by reflected light, we should be unconscious of their existence. Each star must then be a sun, and may be presumed to have its system of planets, satellites, and comets, like our own; and, for aught we know, myriads of bodies may be wandering in space unseen by us, of whose nature we can form no idea, and still less of the part they perform in the economy of the universe. Even in our own system, or at its farthest limits, minute bodies may be revolving like the telescopic planets, which are so small that their masses have hitherto been inappreciable, and there may be many still smaller. Nor is this an unwarranted presumption; many such do come within the sphere of the earth's attraction, are ignited by the velocity with which they pass through the atmosphere, but leave no residuum. These, which are known as falling stars and meteors, are periodical; but that is by no means the case with aërolites, which are also ignited by the sudden condensation of the air on entering our atmosphere, and are precipitated in solid masses with such violence on the earth's surface that they are often deeply buried in the ground.
The fall of meteoric stones is much more frequent than is generally believed. Hardly a year passes without some instances occurring; and, if it be considered that only a small part of the earth is inhabited, it may be presumed that numbers fall in the ocean, or on the uninhabited part of the land, unseen by man. They are sometimes of great magnitude; the volume of several has exceeded that of the planet Ceres, which is about 70 miles in diameter. One which passed within 25 miles of us was estimated to weigh about 600,000 tons, and to move with a velocity of about 20 miles in a second; a fragment of it alone reached the earth.
The obliquity of the descent of meteorites, the peculiar substances they are composed of, and the explosion accompanying their fall, show that they are foreign to our system; but whence derived is still a mystery.
Shooting stars and meteors burst from the clear azure sky, and, darting along the heavens, are extinguished without leaving any residuum except a vapour-like smoke, and generally without noise. Their parallax shows them to be very high in the atmosphere, sometimes even beyond its supposed limit, and the direction of their motion is for the most part diametrically opposite to the motion of the earth in its orbit. The astonishing multitudes of shooting stars and fire-balls that have appeared at stated periods over different parts of the globe, warrant the conclusion that there is either a nebula or that there are myriads of bodies revolving in groups round the sun which only become visible when inflamed by entering our atmosphere.
One of these nebulæ or groups seems to meet the earth in its annual revolution on the 12th and 13th of November.
On the morning of the 12th of November, 1799, thousands of shooting stars, mixed with large meteors, illuminated the heavens for many hours over the whole continent of America, from Brazil to Labrador: it extended to Greenland, and even Germany. Meteoric showers were seen off the coast of Spain, and in the Ohio country, on the morning of the 13th of November, 1831; and during many hours on the morning of the 13th November, 1832, prodigious multitudes of shooting stars and meteors fell at Mocha on the Red Sea, in the Atlantic, in Switzerland, and at many places in England. But by much the most splendid meteoric shower on record began at nine o'clock in the evening of the 12th of November, 1833, and lasted till sunrise next morning. It extended from Niagara and the northern lakes of America to the south of Jamaica, and from 61° of longitude in the Atlantic to 100° of longitude in central Mexico. Shooting stars and meteors, of the apparent size of Jupiter, Venus, and even the full moon, darted in myriads towards the horizon, as if every star in the heavens had started from their spheres. They are described as having been frequent as flakes of snow in a snowstorm, and to have been seen with equal brilliancy over the greater part of the continent of North America.
Those who witnessed this grand spectacle were surprised to