ALGOL  , the Arabic name (signifying " the Demon ") of 6 Persei, a See also:

• STAR

star of the second magnitude, noticed by G . Montanan in 1669 to fluctuate in brightness . See also:

• JOHN
• JOHN (1167–1216)
• JOHN (1290-c. 1320)
• JOHN (1296-1346)
• JOHN (1371–1419)
• JOHN (1468-1532)
• JOHN (1801-1873)
• JOHN (Heb. llni')
• JOHN (ZAPOLYA) (1487-1540)
• JOHN, 4TH MARQUESS OF TWEEDDALE (c. 1695-1762)
• JOHN, DON (1545-1578)
• JOHN, DON (1629–1679)
• JOHN, GOSPEL OF ST
• JOHN, or HAYS (1513–1571)
• JOHN, THE APOSTLE
• JOHN, THE EPISTLES OF

John Goodricke established in 1782 the periodicity of its See also:

• CHANGE (derived through the Fr. from the Late Lat. cambium, cambiare, to barter; the ultimate derivation is probably from the root which appears in the Gr. «a urmu', to bend)

change in about 2d 21h, and suggested their cause in recurring eclipses by a large dark See also:

• SATELLITE (from the Lat. satelles, an attendant)

satellite . Their intermittent See also:

• CHARACTER (Gr. xapareri7p, from xap&crew, to scratch)

character prompted the supposition . The See also:

• LIGHT

light of Algol remains See also:

• CONSTANT, BENJAMIN (1845-1902)

constant during See also:

• CLOSE
• CLOSE (from Lat. clausum, shut)
• CLOSE, MAXWELL HENRY (1822-1903)

close upon 56 See also:

• HOURS, CANONICAL

hours; then declines in 62 hours (approximately) to nearly one-See also:

• FOURTH

fourth its normal amount, and is restored by sensibly the same gradations . The See also:

• AMPLITUDE (from Lat. amplus, large)

amplitude of the phase is 1.1 magnitude; and the See also:

• ABSENCE (Lat. absentia)

absence of any stationary See also:

• INTERVAL

interval at minimum proves the See also:

• ECLIPSE (Gr. €uheo,tis, falling out of place, failing)

eclipse to be partial, not See also:

• ANNULAR, ANNULATE

annular . Its conditions were investigated from photometric data, by See also:

• PROFESSOR (the Latin noun formed from the verb profiteri, to declare publicly, to acknowledge, profess)

Professor E . C . See also:

• PICKERING
• PICKERING, EDWARD CHARLES (1846- )
• PICKERING, TIMOTHY (174 1829)

Pickering in 188o;' and their realization was finally demonstrated by Dr H . C . See also:

• VOGEL, EDUARD (1829-1856)
• VOGEL, SIR JULIUS (1835-1899)

Vogel's spectroscopic See also:

• MEASURES

measures in 1889.2 Previously to each obscuration, the star was found to be moving rapidly away from the See also:

• EARTH
• EARTH (a word common to Teutonic languages, cf. Ger. Erde, Dutch aarde, Swed. and Dan. jord; outside Teutonic it appears only in the Gr. 'pq'e, on the ground; it has been connected by some etymologists with the Aryan root ar-, to plough, which is seen in
• EARTH, FIGURE OF
• EARTH, FIGURE OF THE

earth; its velocity then diminished to zero pari passu the loss of light, and reversed its.direction during the See also:

• PROCESS

process of recovery . Algol, in fact, travels at the See also:

• RATE

rate of 26.3 See also:

• MILES, NELSON APPLETON (1839— )

miles a second See also:

• ROUND (O. Fr. rond, Lat. rotundus, the Fr. is the source also of Du. rond; Ger., Swed., Dan. and Nor. rond)

round the centre of gravity of the See also:

• SYSTEM

system which it forms with an invisible See also:

• COMPANION (through the O. Fr. compaignon or compagnon, from the Late Lat. companio,—cum, with, and panis, bread,—one who shares meals with another; the word has been wrongly derived from the Late Lat. compagnus, one of the same pages or district)

companion, while the two together approach the See also:

• SUN
• SUN (0. Eng. sonne, Ger. sonne. Fr. soleil, Lat. sol, Gr. ijXior, from which comes helio- in various English compounds)

sun with an unvarying See also:

• SPEED, JOHN (1552–1629)

speed of 2.3 miles per second .

The elements of this disparate pair, calculated by Dr Vogel on the somewhat See also:

• PRECARIOUS

precarious See also:

• ASSUMPTION, FEAST OF

assumption that its dark and See also:

• BRIGHT, JOHN (1811-188g)
• BRIGHT, SIR CHARLES TILSTON

bright members-are of equal mean See also:

• DENSITY (Lat. densus, thick)

density, are as follows: See also:

• DIAMETER (from the Cr. &a, through, µErpov, measure)

Diameter of Algol . . . . r,o6i,000 See also:

• ENGLISH

English miles . Satellite . . . 834,300 Distance from centre to centre . 3,230,000 „ „ See also:

• MASS (O.E. maesse; Fr. messe; Ger. Messe; Ital. messa; from eccl. Lat. missa)
• MASS, IN

Mass of Algol s See also:

• SOLAR, SOLLER (Lat. solarium, Fr.• galetas, Ital. solaio)

solar mass . Satellite . . 9 Mean density . about 1 solar . The See also:

• PLANE

plane of the See also:

• JOINT (through Fr. from Lat. junctum, jungere, to join)

joint See also:

• ORBIT (from Lat. orbita, a track, orbis, a wheel)

orbit, in which no deviation from circularity has yet been detected, nearly coincides with the See also:

• LINE

line of sight . The See also:

• PERIOD
• PERIOD (Gr. irepioSos, a going or way round, circuit, aepi, round, and &Sis, way, road)

period of Algol, as measured by its eclipses, is subject to complex irregularities . It shortened fitfully by eight seconds between 1790 and 1879; soon afterwards, restoration set in, and its exact length in 1903 was 2d 2oh 48'n 56°, being only two seconds See also:

• SHORT, FRANCIS JOB (1857– )

short of its See also:

• ORIGINAL

original value .

By an exhaustive discussion, Dr S . See also:

• CHANDLER, HENRY WILLIAM (1828-1889)
• CHANDLER, RICHARD (1738-1810)
• CHANDLER, SAMUEL (1693-1766)
• CHANDLER, ZACHARIAH (1813-1879)

Chandler ascertained in 1888 the compensatory nature of these disturbances;3 and he afterwards found the most important among several which probably conspire to produce the observed effects, to be comprised in a period of 15,000 light-cycles, See also:

• EQUIVALENT

equivalent to 118 years.¢ An explanatory See also:

• HYPOTHESIS (from Gr. inrorcOivat, to put under; cf. Lat. suppositio, from sub-ponere)

hypothesis, propounded by him in 1892,5 is still on its trial . The system of Algol, according to this view, is triple; it includes a large, obscure See also:

• PRIMARY

primary, round which the eclipsing pair revolves in an orbit somewhat smaller than that of See also:

• URANUS
• URANUS (Heaven)

Uranus, very slightly elliptical, and inclined 200 to the line of sight, the periodic See also:

• TIME (0. Eng. Lima, cf. Icel. timi, Swed. timme, hour, Dan. time; from the root also seen in " tide," properly the time of between the flow and ebb of the sea, cf. O. Eng. getidan, to happen, " even-tide," &c.; it is not directly related to Lat. tempus)
• TIME, MEASUREMENT OF
• TIME, STANDARD

time being 118 years . The alternate delay and See also:

• ACCELERATION (from Lat. accelerare, to hasten, celer, quick)

acceleration of the eclipses are then merely apparent; they represent the changes in the length of the light-See also:

• JOURNEY (through O. Fr. jornee or journee, mod. Fr. journee, from med. Lat. diurnata, Lat. diurnus, of or belonging to dies, day)

journey as the stars perform their wide See also:

• CIRCUIT (Lat. circuitus, from circum, round, and ire, to go)

circuit . If these suppositions have a basis of reality, the proper See also:

• MOTION (Lat. motio, from movere, to move)
• MOTION, LAWS OF

motion of Algol should be disturbed by a small, but measurable undulation, corresponding to the See also:

• PROJECTION

projection of its orbit upon the See also:

• SKY (M. Eng. skie, cloud; O. Eng. skua, shade; connected with an Indo-European root sku, cover, whence " scum," Lat. obscurus, dark, &c.)

sky; and although certainty on the point cannot be attained for some years to come, See also:

• LEWIS, HENRY CARVILL
• LEWIS, JOHN FREDERICK (180 1876)
• LEWIS, MATTHEW GREGORY (1775-1818)
• LEWIS, MERIWETHER (1774-1809)
• LEWIS, SIR GEORGE CORNEWALL, BART

Lewis See also:

• BOSS

Boss regarded the See also:

• EVIDENCE (Lat. evidentia, evideri, to appear clearly)

evidence available in 1895 as tending to confirm Dr Chandler's theory.° Proceedings Amer . Acad. vol. xvi. p . 27 . z Astr . Nach . No . 2947 . See also:

• ASIR

Asir .

See also:

• JOURNAL
• JOURNAL (through Fr. from late Lat. diurnalis, daily)

Journal, No . 165 . a Ibid . No . 509 . 5 Ibid . Nos . 255-256 . 6 Ibid . No . 343 A See also:

• RIVAL

rival See also:

• INTERPRETATION (from Lat. interpretari, to expound, explain, inter pres, an agent, go-between, interpreter; inter, between, and the root pret-, possibly connected with that seen either in Greek 4 p4'ew, to speak, or irpa-rrecv, to do)

interpretation of the phenomena it dealt with was put forward by F . See also:

• TISSERAND, FRANCOIS FELIX (1845-1896)

Tisserand in 18951 It involved the See also:

• ACTION

action of no third mass, but depended solely upon the progression of the line of apsides in a moderately elliptical orbit due to the spheroidal shape of the globes traversing it .

Inequalities of the required sort in the returns of the eclipses would ensue; moreover, their duration should concomitantly vary with the varying distance from periastron at the times of their occurrence . It is a See also:

• MOOT

moot question whether changes of the latter See also:

• KIND (O. E. ge-cynde, from the same root as is seen in " kin," supra)

kind actually occur . When they are proved to do so, Tisserand's hypothesis will hold the See also:

• FIELD (a word common to many West German languages, cf. Ger. Feld, Dutch veld, possibly cognate with O.E. f olde, the earth, and ultimately with root of the Gr. irAaror, broad)
• FIELD, CYRUS WEST (1819-1892)
• FIELD, DAVID DUDLEY (18o5-1894)
• FIELD, EUGENE (1850-1895)
• FIELD, FREDERICK (18o1—1885)
• FIELD, HENRY MARTYN (1822-1907)
• FIELD, JOHN (1782—1837)
• FIELD, MARSHALL (183 1906)
• FIELD, NATHAN (1587—1633)
• FIELD, STEPHEN JOHNSON (1816-1899)
• FIELD, WILLIAM VENTRIS FIELD, BARON (1813-1907)

field . Algol gives a See also:

• HELIUM (from Gr. i)Xcor, the sun)

helium-spectrum which undergoes no alteration at minimum . Hence the light from the marginal and central portions of the disc is identical in quality, and the See also:

• LIMB

limb can be little, if at all, darkened by the " See also:

• SMOKE (from O. Eng. smeocan, to smoke, reek, cf. Dutch meek, Ger. Schmauch, probably allied to Gr. vol9caiv)

smoke-See also:

• VEIL (O.Fr. veile, mod. voile, from Lat. velum, cloth, awning, sail)

veil " absorption conspicuous in the sun . The rays of this star spend close upon a See also:

• CENTURY (from Lat. centuria, a division of a hundred men)

century in travelling hither . Dr See also:

• CHASE
• CHASE, SALMON PORTLAND (1808-1873)
• CHASE, SAMUEL (1741–1811)
• CHASE, WILLIAM MERRITT (1849– )

Chase's measures with the Yale See also:

• HELIOMETER (from Gr. iXtos, sun, and p.Erpov, a measure)

heliometer indicated for it, in 1894, a See also:

• PARALLAX (Gr. aapa?X6, alternately)

parallax of about 0" .035 ; 2 and it must, accordingly, be of nearly four times the See also:

• TOTAL

total brightness of Sirius, while its aerial lustre exceeds seventy-See also:

• FOLD

fold that of the solar photosphere . Variables of the Algol class are rendered difficult to discover by the incidental character of their fluctuations . At the end of 1905, however, about 37 had been certainly recognized, besides some outlying cases of in-determinate type, in which continuous occultations by two bright stars, revolving in virtual contact, are doubtfully supposed to be in progress . (A . M .