jects in space. Some are so remote as to be far be yond the reach of the most powerful instruments, and no telescopic aid can show them other than nebulous clouds of greater or less extent. It was while pursu ing these grand investigations that Herschel was led to the conclusion, that among the nebula which were visible in the heavens, there were some composed of chaotic matter, a hazy, luminous fluid, like that occasionally thrown out from comets on their approach to the sun.

Among these chaotic masses he discovered some in which the evidences of condensation appeared manifest, while in others he found a circular disc of light, with a bright nucleus in the centre. Proceeding yet farther, he found well formed stars surrounded by a misty halo, which presented all the characteristics of what he now conceived to be nebulous fluid. Some of the unformed nebulæ were of enormous extent and among those partially condensed, such as the nebula with planetary discs, many were found so vast that their magnitude would fill the space occupied by the sun and all its planets, forming a sphere with a diameter of more than 6000 millions of miles. Uniting these and many other facts, the great astronomer was finally brought to believe, that worlds and systems of worlds might yet be in the process of formation, by the gradual condensation of this nebulous fluid, and that from this chaotic matter originally came the sun and all the fixed stars which crowd the heavens. This theory, extended, but not modified, in the hands of Laplace, is made to account for nearly all the phenomena of the solar system, and has been already referred to in a former lecture.

For a long time, this bold and sublime speculation was looked upon, even by the wisest philosophers, with remarkable favor. The resolution of one or two nebulæ, (so classed by Herschel), with the fifty-two feet reflector of Lord Rosse, has induced some persons to abandon the theory, and to attempt to prove its utter impossibility. All that I have to say, is, that Herschel only adopted the theory after he had resolved many hundreds of nebulæ into stars; and if there ever existed a reason for accepting the truth of this remarkable speculation, that reason has been scarcely in any degree affected by recent discoveries.

I have examined a large number of these mysterious objects, floating on the deep ocean of space like the faintest filmy clouds of light. No power, how ever great, of the telescope, can accomplish the slightest change in their appearance. So distant that their light employs (in case they be clusters) hundreds of thousands of years in reaching the eye that gazes upon them, and so extensive, even when viewed from such a distance, as to fill the entire field of view of the telescope many times. Sirius, the brightest, and probably the largest of all the fixed stars, with a diameter of more than a million of miles, and a distance of only a single unit, compared with the tens of thousands which divide us from some of the nebulæ ; and yet this vast globe, at this comparatively short distance, is an inappreciable point in the field of the telescope. What, then, must be the dimensions of those objects, which, at so vast a distance, fill the entire field of view even many times repeated?

Herschel computes that the power of his great reflector would follow one of the large clusters if it

were plunged so deep in space that its light would require 350,000 years to reach us, and the great teles cope of Lord Rosse would pursue the same object probably to ten times this enormous distance.

Such examinations absolutely overwhelm the mind, and the wild dream of the German poet becomes a sort of dreadful sublime reality :

"God called up from dreams a man into the vestibule of heaven, saying, 'Come thou hither, and see the glory of my house.' And to the servants that stood around his throne he said, 'Take him, and undress him from his robes of flesh cleanse his vision, and put a new breath into his nostrils: only touch not with any change his human heart-the heart that weeps and trembles.' It was done: and, with a mighty angel for his guide, the man stood ready for his infinite voyage; and from the terraces of heaven, without sound or farewell, at once they wheeled away into endless space. Sometimes with the solemn flight of angel wing they fled through Zaarrahs of darkness, through wildernesses of death, that divided the worlds. of life; sometimes they swept over frontiers, that were quickening under prophetic motions from God Then, from a distance that is counted only in heaven light dawned for a time through a sleepy film; by unutterable pace the light swept to them, they by unutterable pace to the light. In a moment the rushing of planets was upon them in a moment the blazing of suns was around them.

"Then came eternities of twilight, that revealed, but were not revealed. On the right hand and on the left towered mighty constellations, that by self-repeti. tions and answers from afar, that by counter-positions

built up triumphai gates, whose architraves, wh so arch-ways-horizontal, upright-rested, rose-at altitude by spans that seemed ghostly from infinitude. Without measure were the architraves, past number were the archways, beyond memory the gates. Within were stairs that scaled the eternities below; above was below below was above, to the man stripped of gravitating body: depth was swallowed up in height insurmountable, height was swallowed up in depth unfathomable. Suddenly, as thus they rode from infinite to infinite, suddenly, as thus they tilted over abysmal worlds, a mighty cry arose—that systems more mysterious, that worlds more billowy,— other heights and other depths,-were coming, were nearing, were at hand.

"Then the man sighed, and stopped, shuddered, and wept. His overladened heart uttered itself in tears; and he said-'Angel, I will go no farther. For the spirit of man acheth with this infinity. Insufferable is the glory of God. Let me lie down in the grave and hide me from the persecution of the infinite; for end, I see, there is none.' And from all the listening stars that shone around issued a choral voice, 'The man speaks truly end there is none, that ever yet we heard of.' End is there none?' the angel solemnly demanded: Is there indeed no end?-and is this the sorrow that kills you?' But no voice anEwered, that he might answer himself. Then the angel threw up his glorious hands to the heaven of heavens, saying, 'End is there none to the universe of God. Lo! also there is no beginning.'"

6

LECTURE X.

THE MOTIONS AND REVOLUTIONS OF THE FIXED STARS.

HAVING reached, in the course of the preceding lec ture, to the outermost confines of the visible creation, let us now return home from this survey of the “island universes" which crowd the illimitable regions of space, to the stars which compose our own cluster, and learn how far the human mind has progressed in its examination of the millions of suns which constitute, in a more definite sense, our own Milky Way.

We have already seen that the parallax of 61 Cygni rewarded the laborious and extraordinary ef forts of Bessel. The example set by this great astronomer encouraged those who followed him, and while his results in this particular case have been confirmed in the most astonishing manner, the distances of many other stars have been obtained, until a sufficient amount of data has been accumulated to determine the approximate distances of the spheres of the fixed stars of different magnitudes. Struve es timates the mean distance of stars of the first magni tude to be 986,000 times the radius of the earth's orbit, or so remote that their light reaches us only after a journey of fifteen years and a half. Stars of the second magnitude send us their light in twentyeight years, those of the third magnitude in fortythree years; while the light from stars of the ninth