his mind, led him to expatiate in a field which was vast and unbounded, as well as unexplored.

kind was, that of all the stars which are singly visible, about one in thirty is undergoing observable change.

The powerful instruments at Slough fully "The catalogue of Messier, communicated to the academy in 1771, and inserted, with some confirmed the opinion that the stars are additions, in the Connaissance des Temps' of not, in the ordinary sense of the word, 1783, contained 68 nebula, which, together with magnified; on the contrary, the more pow 28 added by Lacaille, made up a total of 96. erful the telescope, the less the apparent This branch of science took a rapid flight, how- diameter of the star. The efficacy of the ever, as soon as Herschel applied to it his pow- telescope in stripping the star of its crown erful instruments, his rare penetration and unconquerable perseverance. In 1786 he publish- of splendor to which it owes it apparent ed, in the Philosophical Transactions,' a cata- magnitude, more than counterbalancing logue of a thousand nebulæ or clusters of stars. the increase of the real disk. The stars in Three years later, there appeared, to the aston- the heavens thus resemble many of our ishment of practical astronomers, a second cata-stars on earth, from which, if we take away logue from him, quite as extensive as the first; the flash and glitter, it will be found hard and that again was followed, in 1802, by a third

mers.

catalogue of 500 nebula. Two thousand five to raise their solid merits by any magnifyhundred nebula! such was the contingent sup- ing power to an appreciable quantity. But plied by Herschel to a branch of astronomy to speak more precisely: Herschel ascer which had been hardly touched before him. At tained that the apparent diameters of the the same time, the extensiveness of this work stars are really increased by telescopes, was its least merit." though not in the same proportion as the magnifying powers; a double power showing a star with less than double its previous apparent diameter. But the perfection of his instruments, and his scrupulous accuracy, reduced these apparent diameters far below the measures previously assigned to them. Kepler believed the diameter of Sirius to be four minutes; Tycho Brahe supposed that stars of the first magnitude have, in general, a diameter of two minutes. With the improvement of instruments these measures, or rather estimates, were continually reduced, till at length Cassini assigned to Sirius a diameter of five seconds. Herschel, however, employing the highest magnifying powers, found that the apparent diameter of the chief star in the Lyre is about the third of a second; and that of Arcturus, two-tenths of a second, which he The value of these observations may be supposes to be double of the true diameter. collected from the following remarks of M. Arago:

In surveying the astronomical labors of Herschel, our object is not so much to insist on their number, variety, and combined value, as to show that from the boldness of his genius, his assiduity, and the accuracy of his observations, he took his station at once among the most eminent astronoHe turned his attention to the changes taking place in the sidereal beavens, and the result was, a catalogue of stars, classed according to their intensities, so numerous and exact as to suffice for the basis of all future labors in that department. As to his observations of changing stars, it does not comport with our plan or limits to enter far into such details. The seventh pleiad is not the best authenticated instance of an extinguished star. The journals of the astronomer of Slough could furnish several other examples, but the following will suffice.

"The star numbered the 55th of Hercules, placed in the neck of the figure, has been insert- "It is of the greatest importance to ascertain ed in Flamsteed's catalogue as a star of the fifth the share which illusions of vision have in the magnitude. The 10th of October, 1781, Her- magnitude of the diameter under which we see schel saw it distinctly, and noted that it was the stars, whether with the naked eye or with red; the 11th of April, 1782, he perceived it telescopes. Suppose the disks, seen with the again and marked it in his journal as an ordina-naked eye to be the real disks, then it will follow ry star. Nine years later it was not to be found, though repeatedly looked for. So the 55th of Hercules has disappeared."

If old stars perish, it is equally certain that new stars occasionally appear. Herschel watched closely, also, the periodical stars, which undergo a change of brightness at regular intervals of time, and he furnished lists of the colored stars. The general result of his observations of this

that some stars will be 9000 million of leagues in diameter. In fact, it is proved, by observations of parallax, that, at the distance of the nearest stars, a diameter of one second would answer to at least 38 millions of leagues; consequently the diameter of Sirius, according to Kepler's measure of that star, would be at least Gassendi and Cassini, though much reduced, 9000 millions of leagues. The determination of would still leave to some of the stars diameters of 380 millions of leagues. The observations of Herschel give us, for the diameter of Arcturus,

four millions of leagues, which is still eleven the British Association at its last meeting,

To choose the proper star for observations of parallax, is, in a great measure, a matter of good fortune. Herschel did not make the discovery, though he showed the path to it; but his method has recently had "There is no branch of astronomy which complete success in the hands of M. Bessel Herschel might more justly have called his of Königsberg, to whom belongs the glory own, than that which treats of clustered of first demonstrating the exact value of an stars and luminous nebulæ. Besides the element which goes far to determine the wide latitude which he found in that remote dimensions of the universe. As the details field of speculation for the exercise of a of M. Bessel's discovery were laid before | daring sagacity, he enjoyed, in the possesVOL. II. No. IV.

sion of the most powerful instruments, ad- | this science owes more to his practical vantages for the study of the smaller stars skill than to his happy conjectures. He which had never been enjoyed before was the first who really gauged (to use his This superiority may be best estimated own expression) the heavens. The stars from the fact, that in a small luminous visible in the heavens on a clear night are spot or nebula, in which before him no eye about 5000 in number. Now Herschel, by had ever discerned a star, he was able to reckoning the stars in given spaces where count 14,000 stars! We have seen that he the stellar light is equally diffused, ascer rapidly raised the number of observed nebu- tained that within the space of five degrees lous stars from 96 to 2500. The general in the Milky-way there are at least 331,000 result of his speculations on these pheno- stars. He also clearly established by thoumena is thus explained by his biographer: sands of observations, that the whiteness "On the grounds of probability no reasonable of the Milky way, is due not to these mulperson will refuse to adopt the views of Herschel, titudes of discernible stars, but to gatherand he will remain convinced, that there really ings of stars too small to be distinguished. exist brilliant stars surrounded by atmospheres, The crude luminous matter or raw material luminous of themselves; and the supposition here plays a subordinate part among hosts that these atmospheres, becoming condensed of stars. unite with or are absorbed in the central stars so careless observer it may appear uniformly The Milky-way, though to a as to increase their splendor, will then appear very plausible. The recollection of the Zodiacal luminous, will yet be found by an experilight-that immense luminous zone surrounding enced eye to be divided into separate the equator of our sun, and extending even as far groups, and this grouping of the light was as the orbit of Venus-will then strike the mind, considered by Herschel as progressive. M. as a new feature of resemblance between our sun Arago shares his belief, and exclaims, and certain stars: and the nebula which have "Every thing justifies the opinion of the in their centre condensations of light more or illustrious astronomer. In the course of less decided, will present themselves to the imagination as the first outlines of stars, or as a ages, the clustering power (this is Herstate of luminous matter intermediate between schel's expression) will inevitably bring the uniformly diffused nebula and the nebulous about the disruption, subdivision, and sepstars properly so called. These speculations of aration of the Milky-way. Herschel conduct to nothing less than the supposition that the formation of new stars is continually going on, and that we witness the slow,

progressive creation of new suns."

For many years Herschel held that all the nebulæ are composed of stars. He subsequently modified this opinion, how. ever, and admitted that there are some nebulæ which are not of a starry nature. This recognition of luminous matter existing in the universe in a rude, or, as it may be called, elemental state, was of great importance towards the formation of a theory. The small circular or rather globular nebulæ may be looked upon as luminaries in a more advanced state of growth, and in some of these, which have an extent equal to about a tenth of the moon's surface, Herschel calculated that there are at least 20,000 stars. To him also belong the important remarks that the nebula lie for the most part in strata, and that the heavens in their immediate vicinity are generally quite free from stars.

The favorite object of Herschel's study and contemplation was the Milky-way. That also he considered to be a stratum of stars, in the middle of which nearly is our

sun.

But this was not the speculation of a mere theorist. Though his bold genius has enlarged the bounds of Astronomy, yet

The sun also shared the vigilant attention of the Astronomer of Slough: and here again his opinions have made such an impression on the learned world as can only be effected by those issuing from a master spirit. According to him, the light of the sun does not proceed from the solid nucleus of that body, but from a cloud-like substance which floats in its atmosphere. This doctrine is now generally received, and we need not discuss its advantages in accounting for the spots on the sun, or the phenomena attending the revolution of that luminary on its axis. Herschel believed that the sun is inhabited; but his arguments to this effect only go to prove, that we may conceive the atmosphere of the sun to be so constituted, that the solar nucleus suffers no inconvenience from the proximity of that circumambient heat and light which enliven the solar system. Other and better arguments, as M. Arago intimates, may still be urged in favor of that opinion.

We cannot refrain from turning aside for an instant from the grave review of these speculations and discoveries, to glance at the fate of an unconscious fellow-laborer of Herschel. Had this wonderful man been unpensioned he could never have dared to publish so many new and bold opinions.

Fortunate as he was, and the favorite of apply the common maxim "noscitur a soa king, he has yet been sneered at for what ciis." No definitions can safely decide has been deemed a constant hankering what is monomania and what is not; no after the prodigious; but there can be no act of parliament can mark the exact line doubt that much of what the world ac- which separates madness from philosophy, cepted as philosophy from him, would have poetry, or love. At the present day, when been thought madness in one less advan- there is such a call for a law on monotageously circumstanced. mania which shall settle to a nicety the degree of mental obliquity entitled to humane treatment, and which, by exact definitions, shall teach us "insanire ratione modoque;" it may not be amiss to call attention to the difficulties surrounding such an attempt.

It happened that in 1787 Miss Boydell, the niece of Alderman Boydell, was shot at in the street by a man who was arrested on the spot. Her clothes were set on fire, but she suffered no serious injury, and indeed it was never proved that the pistols were loaded with any thing destructive. By a natural transition, we pass from a The prisoner turned out to be a medical case of lunacy to the moon. An immense practitioner named Elliot. On his trial the height was formerly ascribed to the moundefence set up was insanity, in proof of tains in our satellite. Galileo estimated which Dr. Simmons, physician to St. their general elevation at nearly 30,000 Luke's, came forward among other wit- feet. Hevelius, more accurate, reduced nesses. The Doctor, in order to show the them to 17,000 feet. Herschel, however, disordered state of the unhappy man's lowered to 9,000 feet the highest of the mind, produced in court a paper which lunar mountains, and to the generality of Elliot had sent to him, for the purpose of them he allowed but a very moderate elevabeing presented to the Royal Society, but tion. In this particular he is at variance which the Doctor thought too visionary for that learned body. He called the attention of the court particularly to a passage, in which the author asserted "that the sun is not a body of fire as hath been hitherto supposed, but that its light proceeds from a dense and universal aurora, which may afford ample light to the inhabitants of that body's surface beneath, and yet be at such a distance aloft as not to annoy them. No objection," he proceeds to say, "ariseth to that luminary's being inhabited, and vegetation may obtain there as well as with us. There may be water and dry land, hills and dales, rain and fair weather; and as the light, so the season must be eternal; consequently it may be easily conceived to be by far the most blissful habitation of the whole system." Here then we find adduced as a proof of the madness of Mr. Elliot, the very doctrine which Herschel promulgated with much applause eight years later.

The Recorder, who tried Elliot, held that extravagant opinions are no proof of monomania. We are disposed to think that, in this particular case, the physician of St. Luke's was better qualified to decide than the judge.* To a man's opinions we may

Elliot was acquitted under the indictment for an attempt to murder, but was ordered to be tried for the assault. Chagrined at his detention in prison, he refused food, and died on the twelfth day after his acquittal. He was assuredly insane. See the "Gentleman's Magazine," for 1787, pp. 636

and 645.

with those who have followed him in the same line of inquiry. According to Beer and Maedler, who have bestowed so much care on the study of the moon, there are in that satellite six mountains exceeding Cotopaxi in height, and twenty-two which rise above the elevation of Mont Blanc. In reference to the disagreement existing between the conclusions of recent Selenographists and those of Herschel, the acute and impartial M. Arago makes an observation which deserves to be well weighed by those inimical to the reputation of the latter. "Allow me to remark," he says, "how incompatible the conclusion hazarded by Herschel is, with that affectation of the extraordinary and gigantic, which some have maintained on very slight grounds, to have been the characteristic of that illustrious astronomer."

"The active volcanoes which Herschel fancied that he could descry in the moon, were doubtless optical delusions, or else spots on the moon's surface, illuminated from the earth. We have already mentioned his discovery of the remote planet named by him the Georgium Sidus, but to which continental astronomers persisted in giving his name, and which is now, by general consent, called Uranus. Seven years elapsed before he could discover any satellites attached to the new planet; his perseverance, however, and the perfection of his telescopes, were at length rewarded with the discovery of six. Some of these satellites are so minute, and, owing to their

obscurity, so hard to be detected, that mena, than to engage in computation, or doubts have even been thrown on their ex- the more arduous and essential, though istence. It is therefore not unimportant less fascinating labors, through which the to observe that M. Lamont, of Munich, ob- science can be really benefited." It grievserved in 1837, one of those which had been ed us to read this shallow and ill-considered so long missing. On the whole, the dis- judginent in the "History of Astronomy covery of Uranus, and its satellites, may in the last edition of the "Encyclopædia be justly reckoned among the most re- Britannica." markable additions made to astronomy in modern times.

Herschel was not only a great man; he was also a most fortunate man. He was We have said nothing of the pains taken fortunate in having George III. for a patron. by Herschel to examine the rings of Saturn; Again he was fortunate in having M. Arago nor of his Memoirs on the optical pheno- for a biographer, who, while complete masmena called the Newtonian rings; nor of ter of his subject, is also a gentleman suhis discovery that heat and light have not perior to envy, and capable of sympathizing exactly the same refrangibility. Yet when with the truly great. Thrice fortunate he showed that in the solar spectrum form- was he in transmitting his name and fame ed by refraction with a prism, the thermo- to one who, with the amplest intellectual meter rises higher beyond the limit of the resources of an accomplished scholar and red rays than in any, even the brightest, philosopher, evidently cherishes the chapart of the spectrum, he led the way to in-racteristic boldness of his father's spirit, quiries which have since yielded the most and upholds that liberty of conjecture which important results. Regard to our limits, is indeed the mainspring of sagacity. Sir however obliges us to pass over in silence, as many of his ingenious disquisitions as would suffice to make the reputation of an ordinary man.

The degree of Doctor was conferred on Herschel by the University of Oxford in 1786, and thirty years later he was made a knight of the Hanoverian order of the Guelfs. He died in his eighty-third year, on the 23d of August, 1822.

"For some years before his death," says his biographer, "he enjoyed the purest delight from the distinguished success of his only son. In his last moments he closed his eyes in the grateful thought that that beloved son, the inheritor of a great name, would not allow it to sink, but would even clothe it with fresh lustre, and that great discoveries would also adorn his career. No prediction of the illustrious astronomer has ever been more fully realized."

John Herschel has observed about 2500 nebulæ, and perhaps 2000 double stars in the southern hemisphere. He has detected among them ample evidence of that change and revolution which had fixed his father's attention. When we consider that the Herschels, father and son, have carefully examined the whole starry firmament with 20 feet telescopes-instruments of which, in their present state of perfection, the elder of them may be said to have been the inventor-and that they have made known to us thousands of the most interesting sidereal phenomena, it appears to us hardly an exaggeration to say, that Astronomy, beyond our own system, rests chiefly on their labors.

It is generally understood that the one sole object of Sir John Herschel's labors is to complete those of his father, and to develop fully those views respecting the Construction of the Universe which, when demonstated, will immortalize its author. For such an undertaking, Sir John Herschel has inexhaustible materials in the journals of the observatory at Slough; he has collected all the evidence which the southern hemisphere can supply; and inspired, as he is, by a noble and pious purpose, we doubt not that his work, whenever it shall appear, will be reckoned one of the most remarkable monuments of modern science.

The sketch which we have given of Herschel's discoveries will be sufficient to show that his mind was at once the boldest and the most practical. Skilful, and unconquerably persevering as a contriver, constructor, and observer, he was bold even to temerity in his speculations, but his boldness was always guided by great natural penetration. Yet this great man has not escaped the censure of those modish philosophers who, measuring by the standard of their own minds, would restrain all speculations within narrow limits. One of this school, after mentioning Herschel's sixty-nine memoirs, adds, "A great part of these, however, is filled with speculations MILTON.-A large tablet to the memory of Milton was erected in Allhallows Church on Monday of no value to astronomy; and his taste last. It bears for an inscription Dryden's wellwas rather to observe astronomical pheno- | known sextain.-Court Journal.