628

INDEX.

Delisle—Hypothesis respecting the lumi-nous ring seen during solar eclipses, 386.

De Rheita—Account of the origin of thetelescope, 517.

De Vico—determines the time of rotation ofVenus , 234.

Descartes —opinion respecting the irradiationof light, 351; account of the origin of thetelescope, 517.

Diffraction of Light —discovered by Grimaldi,345; researches of Newton on the sub-ject, ib.

Dollond—Researches on the dispersion oflight, 531; controversy with Euler on thesubject, ib.) discovers the principle ofachromatism, 532; constructs achromatictelescopes, ib.

Dorfel—proves that the comet of 1680moved in a parabolic orbit, 102.

Dunthorne—Researches on the secular in-equality in themean motion of the moon, 60.

Du Sejour—his researches on the subject ofa lunar atmosphere, 232; explanation ofthe origin of Saturn ’s ring, 267.

Earth —Researches of Newton on the figureof the, 37; perturbations of the, computedbyClairaut, 50; figure of the, investigatedbyHuyghens, 66; researches of Maclaurin on the same subject, 67; researches of Clai-raut, ib.’, his theorem relative to the varia-tion of gravity at the surface of the, 68;motion of the aphelion of the, discovered,97; its perturbations investigated by La-place, 127; long inequality discovered byAiry, 128; determinations of the ellipticity,145, 146; determinations of the meandensity, 159.

Eclipses of the Sun , Total—rareness of theiroccurrence, 361; circumstances upon whichthey depend,362; ancient records of, 363-364;modern records, 365-7; accountof theeclipse of 1842, 367-71; change of colourexhibited by the sky during the obscura-tion, 372; darkness during the totality,374; sudden transition from day to night,375 ; luminous ring seen around the moon,376; recorded observations of this pheno-menon, ib.; appearance of the ring du-ring the eclipse of 1842,381-5; explana-tions of the nature and physical cause ofthe ring, 386—90; luminous protuberancesobserved during the totality, 390-393;reddish streak of light observed aroundthe moon’s limb immediately before andafterthetotal obscuration, 396; conclusionssuggested respecting the physical constitu-tion of the sun, 400; aspect presented bythe moon, 401; coruscations of light ob-served, 403; undulatory movements ob-served before and after the total obscuration,404; beads of light observed, 406-10 ;explanations of their physical cause, 411.

Eclipses of the Sun , Annular—earliest re-cords of, 371; modern records, 372; lu-

minous appearance observed around themoon’s limb, 397; aspect of the moonduring the eclipse of 1836,401; beads oflight seen at the exterior and interior con-tacts, 407; explanations of their physicalcause, 411.

Eclipses, Lunar—Phenomena observed d uringthe occurrence of, 412.

Ecliptic—various determinations of the obli-quity of the, 98; its diminution explainedby the theory of gravitation, 98; iniluenceof its displacement on the length of thetropical year, 99 ; its variation affected bythe secular displacement of the equator,100 .

Ellipsoids, Attraction of—Researches of Mac­ laurin , 67; D’Alembert , 69; theory ofthe attraction of spheroids of small eccen-tricity, ib.

Encke—determines the mass of Mercury,125; researches on the mass of Jupiter ,130; demonstrates that the comet whichbears his name revolves in an elliptic orbit,134; speculations oil a resisting medium,ib.

Equinox, place of the—Method of Flamsteedfor determining it, 471.

Eratosthenes —determines the obliquity ofthe ecliptic, 436.

Euler —solves the problem of three bodies,44; researches on the lunar theory, ib.,46; researches on the long inequality ofJupiter and Saturn , 48; invents the me-thod of the variation of elements, 49 ;investigates the secular inequalities of theplanets, 51; fruitless attempt to account,by the theory of gravitation, for the secu-lar inequality in the mean motion of themoon, 61; investigates the theory of thetides, 71; researches on the physicaltheory of Jupiter ’s satellites, 88; researcheson the dispersion of light, 531.

Everest—measures an arc of the meridian inIndia , 146; remarks respecting the arc ofthe meridian measured by Lacaille at theCape of Good Hope , 147.

Fabricius, David—observes the variable starMira Ceti, 540.

Fabricius, John—discovers the solar spots,213; his mode of observing them, 227.

Faye—discovers the comet which bears hisname, 139.

Ferrer—observes the solar eclipse of 1806,367; researcheson the existence of a lunaratmosphere, 386.

Flamsteed—appointed director of the RoyalObservatory, Greenwich, 460; account ofhis labours, 467-477; attempts to deter-mine the parallax of the polar star, 548.

Fontana—first observes spots on the surfaceof Mars , 235.

Foster—Experiments with the pendulumfor the purpose of determining the ellipti-j city of the earth, 156.