INDEX.

m

545; researches on the proper motions ofthe stars, 554.

Cassini, IY.—Remark respecting the Obser­ vatory of Paris , 480.

Cassegrain—devises a new form of the re-flecting telescope, 529.

Catalogues of Stars—Catalogues of variousastronomers, 507-15.

Challis—institutes a search for the planetindicated by the theoretical researches ofAdams, 185; secures two positions of theplanet 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 lunarapogee, 45; revises his solution and obtainsthe true result, 46; researches on the figureof the earth, 67; theorem on the variationof gravity at the earth’s surface, 68; cal-culates the perturbations of Halley’s comet,104.

Comets—Tycho Brah4 demonstrates thatcomets are situate beyond the moon’s or-bit, 102; opinions respecting their orbits,ib. ; Lagrange’s method for calculatingtheir perturbations, 105; methods devisedfor the determination of their orbits, 133;comets of 1807, 134; comet of 1680,289; supposed to move in an ellipticorbit, ib. ; various determinations of itsperiodic time, ib.; comet of 1264, 290;comet of 1811, ib.; comet of Brorsen, ib.;comet of 1843,^6.; various determinationsof the orbit of this comet, 291; generalaspect of comets, 293; comets withouteither nucleus or tail, ib. ; translucencyof cometic matter, ib. ; envelope surround-ing the heads of comets, 294; proved to behollow, ib.; dimension of the envelope,295; nucleus of comets, ib. ; supposed insome instances to be solid, 296; attemptsto determine its magnitude, ib.; structureof the tail, ib. ; its direction generallyopposite to that of the sun, ib.; lateraldeviation of the extremity of the tail, 297;direction of the tail first remarked inEurope by Apian, ib.; the same factpreviously noticed by the Chinese , ib.;comets with several tails, ib. ; comets withtails of great length, ib.; the absolutedimensions of the tail are in many in-stances immense, 298; phenomena usuallyexhibited by comets during their passageof the perihelion, ib.; variation of volumedepending on their position relative tothe sun, 301; great heat to which somecomets are subjected on their passage ofthe perihelion, ib. ; dissolution of comets,302; development of the tail, ib.; varia-tions in the length of the tails of somecomets, 303; examples of very conspi-cuous comets, 304; various opinionswith respect to the durability of comets,306; variation of volume, 307; differentexplanations of this fact, ib. ; hypotheses

respecting the tails of comets, 308; lightof comets, 312; by some enquirers sup-posed to be self-luminous, ib.; by othersthey are held to shine only by reflectedlight, ib. ; experiments of M. Arago, 313;hypothesis of Laplace with respect to theheat suffered by comets, 314; their massmust be very inconsiderable, ib.; ultimateend for which comets are destined, 315.

Comet of Biela—demonstrated by Gambartand Clausen to revolve in an ellipticorbit, 135; its perturbations calculatedby Damoiseau, ib.; apparition in 1846,136; divides into two parts, ib.

Comet of Encke—demonstrated to revolvein an elliptic orbit, 134; tends to confirmthe hypothesis of a resisting medium, 135.

Comet of Faye—discovered by Faye in1843, 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 predictedby Halley, 103; first seen in 1759 byPalitzch, 104; passage of the perihelionin 1835, 136; various determinations ofits elements for 1759, ib.; its perturba-tions calculated by various geometers,137; ancient observation of, by theChinese , 288; physical observations ofSir John Herschel , 301.

Comet of Lexell—First shown by Lexell torevolve in an elliptic orbit, 105; thrownout of its orbit by the disturbing action ofJupiter , ib. ; suspected by Yalz to beidentical with Faye’s comet, 139; thisopinion shewn by Le Yerrier to beerroneous, 140.

Copernicus —his ideas on the attraction ofmatter, 15.

Crabtree—observes the transit of Venus in1639, 421.

D’Alembert —solves the problem of threebodies, 44; computes the lunar perturba-tions, ib. ; researches on the attraction ofellipsoids, 69.

Damoiseau—Researches on the lunar theory,119; calculates the perturbations ofBiela’s comet, 136; researches on Hal-ley’s comet, 137; his evaluation of thelunar 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 byancient eclipses, ib.

De Dominis—Notions of the telescope, 518.

De Gasparis—discovers the planet HygeiaP 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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