appear from most of the observations that it is not a distinct appendage of the planet, but simply a continuation of the inner bright ring.
On the 24th of October, 1851, Mr. Lassell discovered two new satellites revolving round Uranus. He has subsequently succeeded in seeing them with his powerful reflector, on every occasion on which he looked for them. He finds that the observations may be pretty well satisfied by supposing the period of the inner satellite to be 2.506 days, and that of the outer satellite to be 4.150 days. It appears, therefore, that they are interior to the two bright satellites discovered by Sir William Herschel in 1787. From the diagram of their positions inserted in the Monthly Proceedings of the Astronomical Society for November, 1851, they appear, like the other satellites, to revolve in orbits nearly perpendicular to the plane of the ecliptic.
It has been mentioned (p. 139) that a comet discovered by M. Faye, in the year 1843, was found to revolve in an elliptic orbit, and that its perturbations for the ensuing revolution were calculated by Le Verrier, who arrived at the conclusion that its passage through the perihelion would take place on the 2nd of April, 1851. It is a gratifying fact that the comet has actually returned at the appointed time. It was first seen by Prof. Challis, with the Northumberland refractor, on the 28th of November, 1850. The observations of its apparent position have been found to present a remarkable agreement with the corresponding results derivable from the calculations of M. Le Verrier.
Allusion has been made at page 243 to the discovery of a small ultrazodiacal planet (Metis) at the observatory of E. Cooper, Esq., of Markree, in the north of Ireland. An achievement of vastly greater importance has since emanated from that observatory in the shape of a catalogue of 14,888 stars near the ecliptic, the places of which, in general, are not to be found in any catalogues hitherto published. This catalogue was constructed from observations made in the years 1848, 1849, and 1850, and was published in 1851, the expense of printing' having been defrayed by the Government, upon the recommendation of the Royal Society. A second catalogue, destined to contain the places of about 12,000 additional stars, observed in the year 1851, is in the course of preparation at the same observatory. Mr. Cooper and his active assistant, Mr. Graham, are also engaged in executing a series of celestial maps upon a magnificent scale. Each map has a range of 8° both in right ascension and in declination. The scale is four times larger than that of the Berlin maps. It is contemplated to insert in these maps all the stars within their range which have either been observed at Markree, or have been already published in other catalogues. The epoch of reduction is 1850.0. The advantages which cannot fail to accrue to astronomical science from the construction of these maps is incalculable. It must be acknowledged that the labours at Markree Observatory exhibit a loftiness of aim as well as a unity of design, and a spirit of skilful perseverance, which not only serves effectually to remove that establishment from the category of mere amateur observatories, but entitles it to an honourable place in the highest class of those institutions that have been founded for the promotion of astronomical science.
In concluding this note it may be stated, that the Astronomer Royal has now (February, 1852) completed the arrangements at the Royal Observatory for recording transits of stars by means of an electro-magnetic apparatus. The accuracy of this method may be relied on to the twentieth
of a second of time. It is contemplated, in connexion with this improvement, to transmit Greenwich time, by means of the electric telegraph, to all the most important places in the kingdom. The realisation of this project will constitute a boon of inestimable value to the outports, by affording on all occasions a reliable standard for the regulation of chronometers. The successful construction of the submarine telegraph between Dover and Calais will also enable the Royal Observatory to record transits simultaneously with the Royal Observatory of Paris and other similar establishments on the Continent, by which means their respective longitudes relatively to each other may be more accurately ascertained. The immense importance of this object must be obvious to any person who possesses an ordinary acquaintance with astronomical
COPY OF THE NOTE OF THE OBSERVATION OF
DRACONIS, made by Bradley, at Kew, with the zenith sector of Molyneux, on the 21st of December, 1725; the discordance of which with the results of previous observations, revealed to him the first glimpse of his immortal discovery of the Aberration of Light.
It has been mentioned at page 337 that the original note of the observation, of which the subjoined words are an exact copy, was found a few years since by Prof. Rigaud, among the manuscripts of Bradley, written upon a loose piece of paper.
Dec 21st Tuesday 5h 40' sider time Adjusted ye mark to ye Plumb line & then ye Index stood at 8 5h 48′ 22′′ ye star entred 49 521 Star at ye Cross 51 24 Star went out could
As soon as I let go ye course
screw I perceived ye star too much to ye right hand & so it continued till it passed ye Cross thread and within a quarter
of a minute after it had passed
I turned ye fine screw till I saw
ye light of ye star perfectly bissected and after ye obser vation I found ye index at 11, so that by this observation ye mark is about 3" too much south
but adjusting
ye mark and plumb line I found ye index at 8.
ABERRATION of Light-discovered by Brad-
ley, 338; various determinations of its maximum value, 340. Adams-Researches on the theory of Uranus, 168; transmits his results to the Astro- nomer Royal, 173; they furnish the earliest indication of the Trans-Uranian planet, ib.; second series of results obtained by him, 185; announcement of his researches by Sir John Herschel, 194.
Airy-Researches on the lunar theory, 120; discovers the long inequality in the Earth and Venus, 127; determines the mass of Mars, 129; researches on the mass of Ju- piter, 130; determines the ellipticity of the Earth, 145; measures an arc of longitude in the British Isles, 150; demonstrates the existence of errors in the tabular radius vector of Uranus, 167; receives from Adams the results of his researches on the existence of an exterior planet, 173; his reply to Adams, 174; correspondence with Le Verrier on the theory of Uranus, 184; reply of the latter, ib.; proposes a search for the planet, ib.; announces to Le Ver- rier the results arrived at by Adams, 194; communicates an historical statement re- specting the discovery of the Trans-Ura- nian planet, 196; detects two new ine- qualities in the motion of the moon, 206; determination of the lunar parallax, 229; modification of Bessel's method for facilitat- ing the reduction of observations, 345; suc- ceeds Pond at the Observatory of Green- wich, 493; reduction of the Lunar and Planetary Observations, 495; introduces the use of an altitude and azimuth instru- ment at the Greenwich Observatory, ib.; transit circle, 497; reflex zenith telescope, 499; Cambridge Catalogue of Stars, 513; first Greenwich Catalogue, ib.; second Greenwich Catalogue, 514; physical ex- planation of the disks and rings of stars, 546. Al Batani-discovers the motion of the aphe- lion of the terrestrial orbit, 97. Altitude and Azimuth Instrument-first used by Roemer, 465. Apian-first suggests the use of coloured glasses in observations of the sun, 227; re- marks that the tails of comets are turned opposite to the sun, 297.
Arago-Remarks respecting the discovery of the planet beyond Uranus, 196; observes occultations of small stars by the moon, 230; phenomeon witnessed by him on those occasions, 231; experiments on the light of comets, 313; account of the solar eclipse of 1842, 368.
Arcs of the Meridian-Measurement of the arc between Gottingen and Altona, 144; arc of India, 145; arc measured by La- caille at the Cape of Good Hope, 147; la- bours of Maclear, 148; arc measured in the British Isles, 149.
Argelander-Zone observations of stars, 511; executes a catalogue of stars, 513; re- searches on stars having a variable bright- ness, 541; researches on the motion of the solar system in space, 556. Atmosphere, terrestrial-Researches on the oscillations of the, 163. Attraction-Ideas of Copernicus on the sub- ject of, 15; Gilbert, 16; Kepler, 17; Galileo, 19; Borelli, 20; researches of Newton, 20-40; experiments of Bouguer, 158; Schehallien experiment, ib. Auzout his remark respecting a twilight in the moon, 232; invents the micrometer, 450.
Bacon, Roger-Ideas of the telescope, 517. Baily Researches on the influence of the air in pendulum experiments, 156; determines the mean density of the earth, 159; phe- nomena observed during the annular eclipse of 1836, 409; labours connected with star catalogues, 508-13. Bailly-explains the origin of the libratory motion of the nodes of the second satellite of Jupiter, 86; researches on the physi- cal theory of the satellites, 88; determines the magnitude of Jupiter's satellites, 250. Ball-discovers the duplicity of Saturn's ring before the same phenomenon was re- marked by Cassini, 526.
Battista Porta-Ideas of the telescope, 518. Bernouilli-his researches on the tides, 71. Bessel-his researches on the mass of Saturn, 131; experiments on the attrac- tion of different bodies, 133; researches on the satellites of Saturn, 142; investigates the ellipticity of the earth, 145; method
for determining the length of the seconds' pendulum, 155; investigates the influence of the resistance of the air on the rate of oscillation, ib.; directs his attention to the irregularities of Uranus, 167; re- searches on the elements of Saturn's ring, 259; determines the period of the comet of 1811, 289; observations on the nucleus of Halley's comet, 294; opinion respect- ing the tails of comets, 311; researches on the quantity and laws of precession, 320; researches on refraction, 335; method for facilitating the reduction of observations, 334; zone observations of stars, 511; determines the parallax of 61 Cygni, 551; researches on the motion of the solar system in space, 556. Bianchini-Researches on the rotation of Venus, 234.
Biot-Experiments with the pendulum, 153; value of the terrestrial ellipticity hence deduced by him, 153; researches on the motion of the solar system in space, 556. Bode-Explanation of the solar spots, 222. Bond-Physical observations of Saturn's ring, 265; discovers the eighth satellite of Saturn, 271.
Borel Account of the invention of the telescope, 517.
Borelli-his ideas of circular motion, 20; surmise respecting the orbits of comets, 102. Bouguer Researches on atmospheric refrac- tion, 328.
Bouillaud-determines the period of the variable star Mira Ceti, 540; opinion re- specting the cause of its variable bright- ness, 541. Bouvard-his determination of the mass of Jupiter, 130; publishes tables of Jupiter and Saturn, 131; determines the mass of Uranus, 132; calculates tables of Uranus, 165; finds it impossible to reconcile the ancient with the modern observations, ib.; suspects the existence of an exterior planet, ib. Bouvard, E.-calculates tables of Uranus,
174; finds it impossible to reconcile them with all the observations of the planet, 175. Bradley-Researches on the satellites of Ju-
piter, 81; first introduces the equation of light into the tables of these bodies, ib. ; discovers the great inequality of the three interior satellites, and suggests its physical cause, 82; discovers that the orbit of the fourth satellite is eccentric, ib.; researches on refraction, 329; discovers the aberra- tion of light, 338; discovers the nutation of the earth's axis, 341; accounts of his labours at the Observatory of Greenwich, 483; remark respecting the parallax of the fixed stars, 549; remark relative to the motion of the solar system in space, 554.
Brahé, Tycho-overthrows the theory of solid orbs, 15; demonstrates that comets
are situate beyond the moon's orbit, 102; supposes them to move in circular orbits, ib.; views respecting the tails of comets, 308; first employs refraction in correct- ing astronomical observations, 321; in- vents the mural quadrant, 445; observes the new star which appeared in the year 1572, 539; opinion respecting its origin, ib.; estimate of the apparent diameters of the stars, 547.
Brewster his opinion respecting the solar spots, 227. Brinkley-Researches on refraction, 332; researches on the parallax of the fixed stars, 550. Burchardt-calculates the terms of the long inequality of Jupiter and Saturn, depend- ing on the fifth powers of the eccentricities and inclinations, 129; calculates the ele- ments of Halley's comet for 1759, 137; calculates the lunar parallax by means of the formulæ of Laplace, 228. Bürg-calculates tables of the moon, 118; discovers irregularities in the moon's epoch, ib.; attempts to represent them by an empiric equation, 119.
Campani-attains great excellence in the construction of refracting telescopes, 526. Capocci-Researches on the comet of 1843,
Carlini-Researches on the lunar theory, 119; experiments with the pendulum for the purpose of determining the mean den- sity of the earth, 160.
Cassini, J. D.-Discovers the coincidence of the nodes of the moon's orbit with those of the moon's equator, 73; publishes tables of Jupiter's satellites at Bologna, 80; re- jects the equation of light, ib.; method for determining the solar parallax, 211; value of that element assigned by him, 212; remarks respecting the solar spots, 219; executes a chart of the moon's sur face, 230; observes an occultation of Jupiter by the moon, 231; researches on the physical constitution of Venus, 234; discovers that she has a rotatory motion, ib.; determines the period of rotation, ib.; observations on the physical constitu- tion of Mars, 236; discovers that it revolves on an axis, ib.; determines the time of rota- tion, b.; researches on the rotation of Jupiter, 244; theory of the belts of Ju- piter, 248; discovers the duplicity of Saturn's ring, 260; physical observations of the ring, 263; discovers four satellites of Saturn, 268; variable brightness of the fifth satellite, 271; hypothesis of atmo- spheric refraction, 322; appointed Director of the Royal Observatory of Paris, 457. Cassini, J.-his remarks on the rotation of Venus, 234; views respecting the visi- bility of the stars, 543; attempts to de- termine the apparent diameter of Sirius,
545; researches on the proper motions of the stars, 554. Cassini, IV.-Remark respecting the Obser- vatory of Paris, 480.
Cassegrain-devises a new form of the re- flecting telescope, 529.
Catalogues of Stars-Catalogues of various astronomers, 507-15.
Challis-institutes a search for the planet
indicated by the theoretical researches of Adams, 185; secures two positions of the planet anterior to its actual discovery, 193. Clairaut-solves the problem of three bodies, 44; researches on the lunar theory, ib.; fails to account for the motion of the lunar apogee, 45; revises his solution and obtains the true result, 46; researches on the figure of the earth, 67; theorem on the variation of gravity at the earth's surface, 68; cal- culates the perturbations of Halley's comet, 104.
Comets-Tycho Brahé demonstrates that comets are situate beyond the moon's or- bit, 102; opinions respecting their orbits, b.; Lagrange's method for calculating their perturbations, 105; methods devised for the determination of their orbits, 133; comets of 1807, 134; comet of 1680, 289; supposed to move in an elliptic orbit, ib.; various determinations of its periodic time, ib.; comet of 1264, 290; comet of 1811, ib.; comet of Brorsen, ib.; comet of 1843, ib.; various determinations of the orbit of this comet, 291; general aspect of comets, 293; comets without either nucleus or tail, ib.; translucency of cometic matter, ib.; envelope surround- ing the heads of comets, 294; proved to be hollow, ib.; dimension of the envelope, 295; nucleus of comets, ib.; supposed in some instances to be solid, 296; attempts to determine its magnitude, ib.; structure of the tail, ib.; its direction generally opposite to that of the sun, ib.; lateral deviation of the extremity of the tail, 297; direction of the tail first remarked in Europe by Apian, ib.; the same fact previously noticed by the Chinese, ib.; comets with several tails, ib.; comets with tails of great length, ib.; the absolute dimensions of the tail are in many in- stances immense, 298; phenomena usually exhibited by comets during their passage of the perihelion, ib.; variation of volume depending on their position relative to the sun, 301; great heat to which some comets are subjected on their passage of the perihelion, ib.; dissolution of comets, 302; development of the tail, ib.; varia- tions in the length of the tails of some comets, 303; examples of very conspi- cuous comets, 304; various opinions with respect to the durability of comets, 306; variation of volume, 307; different explanations of this fact, ib.; hypotheses
respecting the tails of comets, 308; light of comets, 312; by some enquirers sup- posed to be self-luminous, ib.; by others they are held to shine only by reflected light, b.; experiments of M. Arago, 313; hypothesis of Laplace with respect to the heat suffered by comets, 314; their mass must be very inconsiderable, ib.; ultimate end for which comets are destined, 315. Comet of Biela-demonstrated by Gambart and Clausen to revolve in an elliptic orbit, 135; its perturbations calculated by Damoiseau, ib.; apparition in 1846, 136; divides into two parts, ib.
Comet of Encke-demonstrated to revolve in an elliptic orbit, 134; tends to confirm the hypothesis of a resisting medium, 135. Comet of Faye-discovered by Faye in 1843, 139; its orbit shown to be elliptic, ib.; its perturbations calculated by Le Verrier, ib.
Comet of De Vico-Discovery of the, 141;
shown to revolve in an elliptic orbit, ib. Comet of Halley-its return first predicted by Halley, 103; first seen in 1759 by Palitzch, 104; passage of the perihelion in 1835, 136; various determinations of its elements for 1759, ib.; its perturba- tions calculated by various geometers, 137; ancient observation of, by the Chinese, 288; physical observations of Sir John Herschel, 301.
Comet of Lexell-First shown by Lexell to
revolve in an elliptic orbit, 105; thrown out of its orbit by the disturbing action of Jupiter, ib.; suspected by Valz to be identical with Faye's comet, 139; this opinion shewn by Le Verrier to be erroneous, 140.
Copernicus his ideas on the attraction of matter, 15.
Crabtree--observes the transit of Venus in 1639, 421.
D'Alembert-solves the problem of three bodies, 44; computes the lunar perturba- tions, ib.; researches on the attraction of ellipsoids, 69.
Damoiseau-Researches on the lunar theory, 119; calculates the perturbations of Biela's comet, 136; researches on Hal- ley's comet, 137; his evaluation of the lunar parallax, 228.
Dawes determines the ellipticity of Mer- cury, 233; observations on Saturn's ring, 265.
Day, Sidereal-Invariability of the, demon- strated by Poisson, 161; confirmed by ancient eclipses, ib.
De Dominis-Notions of the telescope, 518. De Gasparis-discovers the planet Hygeia P 243. (See Appendix.) Delambre-calculates tables of Jupiter's sa- tellites, 96; tables of Jupiter and Saturn, 142; calculates tables of Uranus, 165.
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