The task of providing the instruments for the new establishment was confided to M. Struve, the director of the Observatory of Dorpat, so celebrated for his labours on various subjects relating to astronomical science, and more especially for his observations of double stars. The imperial instructions relative to this object were characterised by unbounded liberality. The principal instruments of the establishment have been constructed by German artists. For meridional observations there are four instruments, two of which have been supplied by Ertel of Munich, and two by Repsold of Hamburgh. The instruments by Ertel are a vertical circle 43 inches in diameter, and a transit instrument of 5.85 inches aperture, and 8 feet 6 inches focal length: those by Repsold are a meridian circle 48 inches in diameter, and a prime vertical telescope of 6.25 inches aperture and 91 inches focal length. For extra-meridional observations, the observatory is furnished with a magnificent equatorial telescope by Merz and Mahler of Munich, the object glass of which has a free aperture of 14.93 inches, and a focal length of 22.55 feet. Moreover, it contains several clocks constructed by the most esteemed artists of Germany and England, as well as an ample collection of other instruments, both astronomical and physical, destined for various purposes connected with the practice of observation. In short, the Observatory of Pulkowa may be regarded as one of the most complete in existence, of those institutions that have been founded for promoting the advancement of astronomical science. The expense attending the erection of the building, and its subsequent equipment, amounted in round numbers to 600,000 roubles of silver.

The illustrious Struve has been appointed first director of the Observatory of Pulkowa. An ample staff of assistants, several of whom enjoy a European reputation, is allowed him for carrying on effectually the labours of the establishment. The sum allotted from the imperial treasury for its annual maintenance is no less than 62,200 roubles †.

M. Struve commenced his labours at the Observatory of Pulkowa in the month of September, 1839. The main object to which he has proposed to devote the resources of the establishment, is the advancement of sidereal astronomy. Results of great importance relative to precession, aberration, and other kindred subjects, have already been deduced from the observations ↑.

In the United States of America, practical astronomy has recently been making rapid progress. A central observatory has been established at Washington, which is placed under the direction of Lieut. Maury. The expedition to Chili, undertaken with a view to determine the solar parallax by means of simultaneous observations of Venus and Mars, bears honourable testimony to the enlightened views and liberality of the American Government. Besides the national observatory above alluded to, there are similar institutions, upon a smaller scale, established in several of the states of the Union. Of these, the most celebrated is the observatory of Harvard University, Cambridge, Massachusetts, which boasts of one of the largest and most perfect refracting telescopes in the world. The discovery of the eighth satellite of Saturn, and the establishment of various facts of a highly interesting nature, relative to the physical constitution +£10,366 13s. 4d.

• £100,000.

M. Struve has given a complete description of the Observatory of Pulkowa in a magnificent work entitled, " Description de l'Observatoire Astronomique Central de Pulkowa, par F. G. W. Struve," 2 vols. fol., St. Petersburg, 1845.

of the celestial bodies, have resulted from the labours of Mr. Bond, the director of the observatory, achieved by the use of this powerful instrument.

One of the inventions which do most honour to the Americans, consists in the application of electro-magnetism to geographical and astronomical purposes. As early as the year 1844, the instantaneous transmission of time by the electric telegraph, was employed in determining the difference of the longitudes of Washington and Baltimore. The same method has since been practised for ascertaining the relative longitudes of various other transatlantic cities. Recently, attempts have been made, with complete success, to record transit observations of the celestial bodies, by means of the electro-magnetic principle. As soon as the star is seen bisected by the wire of the telescope, a slight pressure of the finger completes or breaks the galvanic circuit, and the effect is instantaneously transmitted, by the intervention of a magnet, upon a recording surface, to which a uniform motion is given by a peculiar mechanism. This ingenious contrivance for fixing the precise instant of a phenomenon, by calling into exercise the sense of touch to aid that of vision, promises, at no distant period, to supplant the usual mode of recording by the combined application of the eye and the ear*. We may remark, in concluding this chapter, that it ought to be borne in mind also, as an earnest of what may be expected from the future exertions of our transatlantic brethren, that to an American philosopher Practical Astronomy is indebted for the beautiful invention of the collimating telescope.

CHAPTER XIX.

Catalogues of the Fixed Stars.-Their importance as forming the Groundwork of Astro. nomical Science. Earlier Catalogues. Ptolemy.-Ulugh Beigh.-Tycho Brahé.— Halley. Hevelius.--Flamsteed. -Modern Catalogues.-Bradley.-Lacaille.-Mayer. -Maskelyne.-Publication of the Histoire Céleste of Lalande.-Piazzi.-Groom. bridge. Zone Catalogues of Stars.-Bessel.-Argelander Santini.-Catalogue of the Astronomical Society.-Catalogues of Southern Stars.-Fallows.-Brisbane.Johnson. Henderson.-Standard Catalogues of Stars.-Catalogue of the British Association. Recent Standard Catalogues.

CATALOGUES of the fixed stars, considered as contributions to Astronomical Science, possess an importance arising from two distinct causes. In the first place, an accurate catalogue of such objects furnishes a series of points of reference by means of which the positions of the various bodies composing the planetary system may be determined from observation, and the laws of their motions investigated. Secondly, it constitutes the groundwork of stellar astronomy. A comparison of catalogues constructed at different dates, enables the astronomer to ascertain the proper motions of the stars, and to arrive at conclusions respecting the changes which may be taking place in the physical constitution of the sidereal heavens. More

It would appear that several individuals in the United States are entitled to share in the merit of this ingenious invention, among whom may be more especially mentioned Mr. Bond, Mr. Sears Walker, Prof. Mitchell, and Dr. Locke. It has been stated in the text, that the instant of transit may be noted, either by completing the galvanic circuit, supposing that in the ordinary state of the apparatus the current of electricity is interrupted, or by making the electricity to flow in a continual current, and then suddenly breaking the circuit. Both of these methods have been practised in America. At the meeting of the Astronomical Society held on the 9th of May, 1851, there was exhibited

over, it is by such a comparison alone, that he can discover whether there exist any real grounds for believing that the whole solar system is affected with a motion of translation in space.

The first individual who constructed a catalogue of the stars was Hipparchus, who may be considered as the true founder of Astronomical Science. It is said by Pliny, that he was induced to enter upon this undertaking, by the sudden apparition of a new star in his time. Be this as it may, it is certain that he actually determined by observation, the longitudes and latitudes of upwards of a thousand stars, and arranged the results in a catalogue. The earliest production of this kind now extant, is the catalogue inserted by Ptolemy in the Syntaxis. It contains the longitudes and latitudes of 1028 stars, arranged in 48 constellations. The epoch is the first year of the reign of the emperor Antoninus, which corresponds to the year 138 A.D. It has been suspected, on very probable grounds, that this catalogue is nothing more nor less than the catalogue of Hipparchus, transported to the time of its reputed author, by applying to the longitudes of all the stars a common additive quantity for the supposed effect of precession during the intermediate period.

The next catalogue of stars, in the order of time, is that of the Tartar prince, Ulugh Beigh. This individual, who was a grandson of the renowned Tamerlane, established an observatory at Samarcand, the capital of his father's dominions, and devoted himself with great ardour to astronomical pursuits. Having found that the positions of the stars, as assigned by Ptolemy in his catalogue, were in many instances considerably erroneous, he formed the resolution of constructing a new catalogue, founded exclusively upon his own observations. This design was actually realised by him. The number of stars in the catalogue of this prince is 1019, being only nine less than the number contained in Ptolemy's catalogue. The epoch is the year 1437 A.D. The mode of arrangement

is the same as that employed by Ptolemy. Ulugh Beigh was treacherously slain by his son in the year 1449, shortly after his accession to the throne of his father.

The next catalogue recorded in the annals of astronomy, is that of the illustrious Tycho Brahé. It originally appeared in the work of that astronomer, entitled Astronomia Instaurata Progymnasmata, which was first published in the year 1602. The number of stars is 777. The epoch is 1600 A.D. From the labour and skill employed by Tycho Brahé in its construction, this catalogue was vastly more accurate than any other that had been hitherto executed. Kepler subsequently enlarged it from Tycho Brahe's observations to 1005 stars, and published it in the year 1627, at the end of the Rudolphine Tables.

Halley's Catalogue of Southern Stars was the next in succession after a contrivance for recording transits by electro-magnetism, which had been used for some time at the Cambridge Observatory, U. S. In this apparatus, the signal was made by interrupting the galvanic circuit, the recording paper upon which the magnet acted being applied closely upon a cylinder, to which a uniform motion was given by a mechanism devised at Cambridge, termed the spring governor. Mr. Airy proposes to introduce the mode of recording transits by electro-magnetism at the Royal Observatory, where the necessity of transmitting time from the meridian transit clock to the altitude and azimuth instrument (the observations with which are made by noting the transit of the object over a system of horizontal and vertical wires) renders such a method peculiarly desirable. It would seem that the Astronomer Royal contemplates applying the principle so that the instant of transit shall be indicated by completing the galvanic circuit, and that he purposes giving a uniform motion to the recording cylindrical surface by means of a centrifugal pendulum.

Tycho Brahe's. The observations which form the basis of this catalogue were made at St. Helena, during the years 1676-7-8. The number of stars is 341. The epoch is 1677. Besides the circumstance of its relating exclusively to stars in the southern hemisphere, this catalogue is further remarkable for being the first that was constructed from observations made by the use of telescopic sights. Although not so accurate as was desirable, even for the astronomy of his time, Halley did not on any subsequent occasion attempt its improvement. It was submitted, however, to a careful revisal by Abraham Sharp, and was inserted in its amended form in the third volume of the Historia Celestis of Flamsteed.

The catalogue of Hevelius appeared in a posthumous work published in 1690*. It contained 1564 stars. The epoch is 1660. In consequence of the pertinacity with which its author adhered to the use of simple pinnules in making observations of the celestial bodies, this catalogue has not been attended with so much advantage to astronomical science as might have been expected from the labour bestowed upon its construction. All the above-mentioned catalogues, after being subjected to a careful revisal by the late Mr. Baily, were then reprinted; and, in their improved state, they now form the thirteenth volume of the "Memoirs of the Astronomical Society."

It has been already mentioned that Flamsteed's "British Catalogue" was published in 1725, in the third volume of the "Historia Celestis." Mr. Baily executed a scrupulous revisal of this catalogue also, adding to it several hundred stars, which he extracted from Flamsteed's original observations. In this form it was republished by him in 1835, at the end of his "Account of the Life and Correspondence of Flamsteed," a work to which we have repeatedly had occasion to allude.

No catalogue of stars was constructed from Bradley's observations during the lifetime of that great astronomer. In the Nautical Almanac for 1773, there finally appeared a catalogue of 389 principal stars, extracted by Mason from the records of the observations made by him at Greenwich. This catalogue was subsequently inserted by Dr. Hornsby in the first volume of Bradley's Observations, which was published at Oxford in 1798. Allusion has been made to Bessel's Fundamenta Astronomiæ, which he published in 1818, containing a catalogue of stars constructed from the totality of the observations made by Bradley between the years 1750 and 1762. The number of stars in this catalogue is 3112. The epoch is January 1, 1750.

The illustrious Lacaille is the author of three catalogues of stars. The first of these was published in 1757, in his Fundamenta Astronomiæ. It contains the places of 398 stars. The epoch is January 1, 1750. The place of the equinox was determined by Flamsteed's method, from observations of a Lyra and Sirius, in connexion with corresponding observations of the sun. This may be considered as the first catalogue which, in point of accuracy, can bear a comparison with those of modern construction. In consequence of its having become exceedingly rare, the late Francis Baily undertook a careful revisal of it, and procured its insertion in the fifth volume of the "Memoirs of the Astronomical Society."

The second catalogue of Lacaille's is founded on observations of southern stars made by him during his residence at the Cape of Good Hope. Of these observations, comprehending the places of nearly ten

• Prodromus Astronomiæ, Gedan, 1690.

thousand stars, a partial catalogue only was formed by the author, containing the reduced places of 1942 stars*. The remaining mass continued in their original condition, until at length, in 1838, the British Association, at the suggestion of Mr. Baily, undertook the reduction of the whole of the observations according to a uniform system. The computations were executed under the superintendence of the late Professor Henderson, of Edinburgh. The number of stars is 9766. The epoch is January 1, 1750. The catalogue was printed in 1845, at the expense of the Government.

Lacaille's third catalogue is one of 515 zodiacal stars, which was published in 1763 as a posthumous work. He contemplated that this catalogue should contain the places of 800 stars; but he was prevented by death from realising his design. The observations upon which it is based were reduced, shortly after his death, by his personal friend Baily; who does not seem, however, to have executed his task with the scrupulous regard to accuracy which a work of so much importance demanded. The epoch of this catalogue is the year 1765.

Mayer is the author of a catalogue of 998 zodiacal stars, which appeared in a volume of posthumous works, published at Gottingen, in 1775. Through the influence of Francis Baily, the original observations were brought from Gottingen to this country, and were published in 1826 at the expense of the Board of Longitude. The same individual having carefully revised the catalogue, by collating it with the original observations, procured its insertion in the fourth volume of the Memoirs of the Astronomical Society."

Maskelyne's fundamental catalogue of 36 stars, published by him, originally in the Greenwich Observations, was by far the most accurate production of the kind that had been hitherto given to the world. This small collection long continued to be an indispensable guide to the practical astronomer.

Observations of circumpolar stars present a peculiar interest, on account of their utility in researches on refraction and various other subjects of astronomical science. In 1800 the Rev. Francis Wollaston published a small catalogue of such stars in a work entitled "Fasciculus Astronomicus." Towards the close of the last century, a vast number of observations of stars were made at the Ecole Militaire of Paris, by D'Agelet and Michael Lefrançais Lalande, nephew of the celebrated astronomer of that name. The observations were made in zones. It was contemplated in this manner to determine the positions of all the stars in the northern hemisphere down to the ninth magnitude. They were published in 1801, in a volume entitled "Histoire Céleste Française," but they were unreduced, and therefore they were, in point of fact, inaccessible to the astronomer. Partial reductions of these observations were shortly afterwards made; but the great mass remained for many years in their original condition. In 1825, Schumacher published tables for facilitating the reduction of the stars contained in the Histoire Céleste, computed according to a plan suggested by Bessel. In 1837, the British Association agreed to defray the expense of the reduction of all the observations, at the suggestion of Francis Baily, who undertook the superintendence of the whole operation. The Government, as in the case of Lacaille's observations of southern stars, agreed to defray the expense of printing.

All the observations, including the partial catalogue, were published after Lacaille's death, in a work entitled Calum Australe Stelliferum 4to., Paris, 1763.