HERSCHEL

SIR WILLIAM HERSCHEL was born in Hanover, Germany, November 15, 1738. He was the son of a bandmaster and was specially educated in music. At fourteen he was forced to earn his own living and joined the band of the Hanoverian Guards. This took him to England in 1759. He later became organist at Bath. All this time he studied the languages and mathematics by himself. He grew to be much interested in the science of music and was led from this to take interest in the fabled "music of the spheres."

Even an ordinary telescope was beyond his means, and he at length, after some 200 failures, succeeded in constructing specula for a telescope that he considered satisfactory. In 1781 with one of his own telescopes he discovered the planet Uranus, thought at first to be a comet. Honors now fell fast upon him. He discovered two of the satellites of Uranus, two more of Saturn, and that the moon is without atmosphere; noted many of the binary stars; made the great inference from the movements of the stars that the whole solar system is rushing toward the constellation of Hercules; and pointed out many nebulous stars, which led directly to the nebular theory of the universe.

He died in 1822. His one son, Sir John Herschel, became also a famous astronomer.

THE DISCOVERY OF URANUS

ACCOUNT OF A COMET

On Tuesday, the 13th of March, 1781, between 10 and 11 in the evening, while examining the small stars in the neighborhood of H Geminorum, I perceived one that appeared visibly larger than the rest: being struck with its uncommon magnitude, I compared it to H Geminorum and the small star in the quartile between Auriga and Gemini, and finding it so much larger than either of them, suspected it to be a comet. I was then engaged in a series of observations on the parallax

of the fixed stars, which I hope soon to have the honour of laying before the R. S.; and those observations requiring very high powers, I had ready at hand several magnifiers of 227, 460, 932, 1536, 2010, &c., all of which I have successfully used on that occasion. The power I had on when I first saw the comet was 227. From experience I knew that the diameters of the fixed stars are not proportionally magnified with higher powers, as the planets are; I therefore now put on the powers of 460 and 932, and found the diameter of the comet increased in proportion to the power, as it ought to be, on a supposition of its not being a fixed star, while the diameters of the stars to which I compared it, were not increased in the same ratio. Also, that the comet being magnified much beyond what its light would admit of, appeared hazy and illdefined with these great powers, while the stars preserved that lustre and distinctness which from many thousand observations I knew they would retain. The sequel has shown that my surmises were well founded, this proving to be the comet we have lately observed.

Mr. H. reduced all his observations on this comet to three tables. The first contains the measures of the gradual increase of the comet's diameter. The micrometers he used, when every circumstance is favourable will measure extremely small angles, such as do not exceed a few seconds, true to 6, 8, or 10 thirds at most; and in the worst situations true to 20 or 30 thirds; he therefore gave the measures of the comet's diameter in seconds and thirds. The first table, containing the measures of the comet's diameter, shows that, from March 17 to April 18, the apparent diameter had increased from 2" 53" to 5' 20".

The second table contains the comet's distances from several telescopic fixed stars from March 13 till April 19, and those distances expressed in minutes, seconds and thirds. And the third table contains the comet's angle of position with regard to the parallel of declination of the same stars measured by a micrometer; by which means its places and apparent path might be determined.-Trans. Roy. Phil. Soc.

ON THE NAME OF THE NEW PLANET

By the observations of the most eminent astronomers in Europe it appears that the new star, which I had the honour of pointing out to them in March, 1781, is a primary planet of our solar system.* A body

The observations of this new planet, at first suspected to be a comet, are abridged at p. 154. of this volume. Dr. Herschel, the discoverer, here calls it the Georgium Sidus, or Georgian planet, in honour of his Majesty; by which name it is commonly distinguished in this country.

so nearly related to us by its similar condition and situation, in the unbounded expanse of the starry heavens, must often be the subject of conversation, not only of astronomers, but of every lover of science in general. This consideration, then, makes it necessary to give it a name, by which it may be distinguished from the rest of the planets and fixed stars. In the fabulous ages of ancient times the appellations of Mercury, Venus, Mars, Jupiter, and Saturn, were given to the planets, as being the names of their principal heroes and divinities. In the present more philosophical era, it would hardly be allowable to have recourse to the same method, and call on Juno, Apollo, Pallas or Minerva, for a name to our new heavenly body. The first consideration in any particular event, or remarkable incident, seems to be its chronology; if in any future age it should be asked, when this last-found planet was discovered it would be a very satisfactory answer to say, "In the reign of King George the Third." As a philosopher, then, the name of Georgium Sidus presents itself to me, as an appellation which will conveniently convey the information of the time and country where and when it was brought to view.

ON NEBULOUS STARS, PROPERLY SO CALLED

In one of his late examinations of a space in the heavens, which he had not reviewed before, Dr. H. discovered a star of about the eighth magnitude, surrounded with a faintly luminous atmosphere, of a considerable extent. The phenomenon was so striking that he could not help reflecting on the circumstance that attended it, which appeared to be of a very instructive nature, and such as might lead to inferences which will throw a considerable light on some points relating to the construction of the heavens.

Cloudy or nebulous stars have been mentioned by several astronomers; but this name ought not to be applied to the objects which they have pointed out as such; for, on examination, they proved to be either mere clusters of stars, plainly to be distinguished with his large instru

But, in other countries it is often called by other names; as Ouranus, Uranius, Herschel, &c. Its Astronomical mark, or character is H. By later observations and calculations it has been determined that the diameter of this planet is about 35,109 miles, or 4 4-10 times that of the earth; its distance from the sun 1800 millions of miles, or above 19 times the earth's distance; that the period of its revolution in its orbit round the sun, is 83 years, 140 days, 17 hours, Dr. Herschel has also discovered 6 satellites or moons belonging to this planet, whose orbits are nearly perpendicular to the plane of the ecliptic; and they all perform their revolutions in their orbits contrary to the order of the signs, that is, their real motion is retrograde.-Original note.

ments, or such nebulous appearances as might be reasonably supposed to be occasioned by a multitude of stars at a vast distance. The milky way itself consists entirely of stars, and by imperceptible degrees he was led on from most evident congeries of stars to other groups in which the lucid points were smaller, but still very plainly to be seen; and from them to such wherein they could but barely be suspected, till he arrived at last to spots in which no trace of a star was to be discerned. But then the gradations to these later were by such well-connected steps as left no room for doubt but that all these phenomena were equally occasioned by stars, variously dispersed in the immense expanse of the universe.

When Dr. H. pursued these researches, he was in the situation of a natural philosopher who follows the various species of animals and insects from the height of their perfection down to the lowest ebb of life; when, arriving at the vegetable kingdom, he can scarcely point out to us the precise boundary where the animal ceases and the plant begins; and may even go so far as to suspect them not to be essentially different. But recollecting himself, he compares, for instance, one of the human species to a tree, and all doubt of the subject vanishes before him. In the same manner we pass through gentle steps from a coarse cluster of stars, such as the Pleiades, the Præserpe, the milky way, the cluster in the Crab, the nebula in Hercules, that near the preceding hip of Bootis, the 17th, 38th, 41st of the 7th class of his catalogues, the 10th, 20th, 35th of the 6th class, the 33d, 48th, 213th of the 1st, the 12th, 150th, 756th of the 2d, and the 18th, 140th, 725th of the 3d, without any hesitation, till we find ourselves brought to an object such as the nebula in Orion, where we are still inclined to remain in the once adopted idea, of stars exceedingly remote, and inconceivably crowded, as being the occasion of that remarkable appearance. It seems, therefore, to require a more dissimilar object to set us right again. A glance like that of the naturalist, who casts his eye from the perfect animal to the perfect vegetable, is wanting to remove the veil from the mind of the astronomer. The object mentioned above is the phenomenon that was wanting for this purpose. View, for instance, the 19th cluster of the 6th class, and afterwards cast your eye on this cloudy star, and the result will be no less decisive than that of the naturalist alluded to. Our judgment will be, that the nebulosity about the star is not of a starry nature.

But that we may not be too precipitate in these new decisions, let us enter more at large into the various grounds which induced us

formerly to surmise, that every visible object, in the extended and distant heavens, was of the starry kind, and collate them with those which now offer themselves for the contrary opinion. It has been observed, on a former occasion, that all the smaller parts of other great systems, such as the planets, their rings and satellites, the comets, and such other bodies of the like nature as may belong to them, can never be perceived by us, on account of the faintness of light reflected from small opaque objects: in the present remarks, therefore, all these are to be entirely set aside.

A well connected series of objects, such as mentioned above, has led us to infer that all nebulæ consist of stars. This being admitted, we were authorized to extend our analogical way of reasoning a little further. Many of the nebulæ had no other appearance than that whitish cloudiness, on the blue ground on which they seemed to be projected; and why the same cause should not be assigned to explain the most extensive nebulosities, as well as those that amounted only to a few minutes of a degree in size, did not appear. It could not be inconsistent to call up a telescopic milky way, at an immense distance, to account for such a phenomenon; and if any part of the nebulosity seemed detached from the rest, or contained a visible star or two, the probability of seeing a few near stars, apparently scattered over the far distant regions of myriads of sidereal collections, rendered nebulous by their distance, would also clear up these singularities.

In order to be more easily understood in his remarks on the comparative disposition of the heavenly bodies, Dr. H. mentions some of the particulars which introduced the ideas of connection and disjunction: for these, being properly founded on an examination of objects that may be reviewed at any time, will be of considerable importance to the validity of what we may advance with regard to the lately discovered nebulous stars. On June 27, 1786, he saw a beautiful cluster of very small stars of various sizes, about 15' in diameter, and very rich of stars. On viewing this object, it is impossible to withhold our assent to the idea which occurs, that these stars are connected so far with one another as to be gathered together, within a certain space, of little extent when compared to the vast expanse of the heavens. As this phenomenon has been repeatedly seen in a thousand cases, Dr. H. thinks he may justly lay great stress on the idea of such stars being connected. On September 9, 1779, he discovered a very small star near e Bootis. The question here occurring, whether it had any connection with e or not, was deter