INDEX.

Coo

fourth satellite, ib.; first rejects and sub-sequently admits the equation of light, ib.;remarks that the nodes of the fourth sa-tellite have a direct motion on the planeof Jupiter ’s orbit, 85; discovers the libra-tory motion of the nodes of the secondsatellite, 86; investigates the inclinationof the third satellite, ib .; determines themagnitudes of Jupiter ’s satellites, 250.

Mars —various determinations of his mass,129; spots on his surface, 235; their firstdiscovery, ib.; they indicate a rotatorymotion of the planet, 236; period of rota-tion determined, ib.; appearance of brightspots at the poles, 237; physical explana-tion of these phenomena, ib.

Maskelyne—Experiment of, to determinethe attraction of Schehallien, 158; phe-nomena observed by him during the tran-sit of Venus in 1769, 429; appointed di-rector of Greenwich Observatory, 488.

Maupertius—Explanation of the origin ofSaturn ’s ring, 267; hypothesis respectingthe variability of the light of stars, 541.

Mayer—calculates lunar tables,4 6; researcheson thelibrationof themoon,73; researcheson refraction, 330; account of his laboursin practical astronomy, 487; suggests theuse of the repeating circle, 488; researcheson the proper motions of the stars, 555.

Mecanique Celeste—publication of the, 108.

Mercury —Researches of Le Verrier on thetheory of, 125; various determinations ofits mass, ib.; difficulty experienced inmaking researches on its physical constitu-tion, 233; mountains upon its surface, ib.;is surrounded by an atmosphere of con-siderable extent, ib.; is slightly spheroidal,ib.; its ellipticity determined by Dawes, ib.

Mercury , transits of—Transit predicted byKepler , 415; observed by Gassendi ; ac-counts of various transits, 417; pheno-menon observed during the transit of 1753;physical appearances noticed during seve-ral other transits, 418.

Meridian Circle—invented by Roemer, 461.

Mersenne —suggests the principle of the re-flecting telescope, 527.

Messier—Observations of Saturn ’s ring, 264;remark on the discovery of Uranus , 277;observations of nebulae.

Metius —proved to be one of the inventorsof the telescope, 519.

Michell—first points out the principle uponwhich the visibility of the stars mainlydepends, 543; applies it to the determina-tion of the relative brightness of the stars,ib.; estimate of the apparent diameter ofSirius, ib.; adopts the hypothesis of acentral sun, 558; views on the physicaltheory of double stars, 559.

Micrometer—first invented by Gascoigne,450; contrivance devised by Huyghens ,ib.; Malvasia, ib.; Auzout, ib. ; Hooke,451; Wren, ib.

Milky Way—Early notions of the, 572;theory of Wright, 573; researches of Sir W. Herschel , 575; method of gauging theheavens devised by him, ib.; speculationson the breaking up of the, 576; researchesof Struve on the physical structure of the,577; gauges of Sir J. Herschel in thesouthern hemisphere, ib.

Moll—Communication relative to the inven-tion of the telescope, 518.

Montanari—first discovers that the star <8Persei is variable, 540.

Moon—Newton’s researches on the theory ofthe, 36; motion of the apogee erroneouslycomputed by him, 37; researches ofEuler,44 ; Clairaut,45 ; D’Alembert, ^.;motion of the apogee reconciled with thetheory of gravitation, 46; secular inequa-lity in the mean motion, discovered byHalley, 60; researches of Dunthorn on thesubject, ib.; fruitless attempts of geometersto account for it by the theory of gravita-tion, 61; finally traced to its origin byLaplace, 62; secular inequalities of theperigee and nodes, 64; perturbations de-pending on the spheroidal figure of theearth, 65; inequality in longitude involv-ing the solar parallax, 65 ; irregularitiesin the epoch discovered, 118; suspectedto arise from some long inequality, 119;represented by an empiric equation, ib.;researches on the lunar theory by Damoi-seau, 119; researches of Plana and Carlinion the same subject, ib.; Lubbock , 120;Poisson , 120; irregularities in the epochaccounted for by Hansen, 121; mass de-termined by Newton , 122; determinationof the same element by Laplace, ib.; twonew inequalities detected by Airy, 206;accounted for by Hansen, ib.; charts ofher surface constructed by different per-sons, 229; existence of a lunar atmo-sphere, 230; controversy on the subject, ib.

Moon , Libration of—^Diurnal libration dis-covered by Galileo , 72; libration in longi-tude discovered,^.; researches of Cassini,73; Mayer, id.;. Lalande, ib. ; physicallibration pointed out by Newton , 74; re-searches of Lagrange, ib.; Poisson , 142;Nicollet, 143.

Motion of the Solar System in space—Re-searches on the, 555-557.

Mural Circle—first used at the Observatoryof Greenwich, 491.

Mural Quadrant—invented by Tycho Brahe ,445.

Nebulse—Early observations of, 563; obser-vations of Sir W. Herschel , 564; nebularhypothesis, 567; observations of Dunlop,568; Sir John Herschel , ib. ; Lord Rosse ,569.

Neptune—discovered by Dr. Gallo, 192;discordance between the observed andtheoretical elements, 202; explanation of