Dictionary of Greek and Roman antiquities. Ed. by William Smith. Illustrated by numerous engravings on wood.

ASTRONOMIA. ASTRONOMIA.. 155
along withl the sun on the 16th of April, B. c. 44, cQalvotv, P. - Occasus.latutinus -Appalrens.
rose with the sun at Rome several days earlier in First visible setting of a star before sunrise.
the age of Meton, and do not now rise with the (5) A'vo:s a7rEptia (arvo/Usy, G.-'Eac7repa
sun at Rome until several days later. This is EsrsaTruavoLs,atvoimEye, P. —OccasZus Vesjpe/tius
caused by the precession of the equinoxes. Apparens s. Occasus Ieliacus. Heliacal setting,
2. The time of the risings ard settings of the i. e. Last visible setting of a star in the evening
fixed stars is different on the same day in places twilight.
whose latitude is different. Thus, in the year With regard to the above technicalities we must
when the Pleiades rose along with the sun at observe
Rome on the 16th of April, they did not rise along 1. That Geminus (I. c.) draws a distinction be*
with the sun at Athens until the 22d of April. tween the words YarvoAk1 and &,rMro7h. By
Too little attention was paid to these consider- id.varoX1 hle understands the rising of a star conations by the Roman writers; and consequently sidered simply with reference to its elevation above
we not unfrequently discover that they combined the horizon, which takes place once in twenty-four
the observations of astronomers who lived at times hours in consequence of the diurnal motion; by
and places remote from them and from each other e7rsroAi4, the rising of the star considered with rethat calculations made for the latitude of Athens, ference to its distance from the sun, which depends
or of Rhodes, or of Alexandria, 300 years before, upon the sun's place in the ecliptic. As to the
wvere adopted at once and transferred to their settings of the stars, he would make eIOLs the corcalendars without change or modification. relative of &veaoAX and Icp,4Is of E7rToX; but to
Another source of confusion is a want of pre- this last definition he does not himself adhere,
cision in specifying the different kinds of risings since he constantly employs ualots to denote the
and settings, which ought always to be most care- setting of a star, when considered with reference
fully distinguished from each other by appropriate to its distance from the sun. Ptolemy, while he
scientific terms. includes all the risings and settings under the
The risings and settings of the fixed stars, when general designation of lbdo'ets &rAxarsiv, endeavours
considered with reference to the sun's place in his to introduce an improved nomenclature, by vary —
orbit, may be arranged under eight heads: - ing the preposition according as the star rises or
(a) When a star rises at sunrise. sets along with (aTh), or before (7rp6) or after
(b) When a star rises at sunset. (s7r[) the sun, but pays no regard to the rule of
Wc) Then a star sets at sunrise. Geminus with respect to &va7oXA and E7r'oX15.
(d) When a star sets at sunset. 2. Two terms, in addition to those set down
(a) When a star rises shortly before the sun so above, are commonly employed by writers on
as to be just visible in the morning twilight as it these topics, the CosMICAaL rising and setting
ascends above the horizon before its rays are over- (Ortus Cos2icus, Occasits C.), and the AcRorNx —
powered by the light of the more brilliant lu- CHAL rising and setting (Ortus Acronychus, Ocminary. casus A.).
(/3) When a star rises shortly after sunset so as The epithet Cbssmices, as applied to this subject,
to be just visible in the evening twilight as it first occurs in a note of Servius on Virg. Geoyg. i.
ascends above the horizon. 218, "ortus et cecasuts duo sunt: unus'A.atds(y) When a star sets shortly before sunrise so id est, solaris; et alter teocuKrT6s, id est, mundanus:
as to be just visible in the morning twilight as it unde fit ut ea signa qnae cum sole oriuntur a nobis
sinks below the horizon. non possint videri; et ea, quae videmus, quantum
(8) When a star sets shortly after sunset so as ad solls rationem pertinet, videantur occidere."'
to be just visible in the evening twilight as it Modern astronomers have for the most part (see
sinks below the horizon. Petavius, Varr. Diss. p. 3, ed. 1630) adopted the
The names by which these, taken in order, are phrase Ortus Caosmmicus to indicate the rising marked
discriminated by the Greek astronomers Geininus (a), that is, the Ortus lieatutiznus Veus, and Oc(Isagog. cap. xi.) and Ptolemy (A/lcath. Synatax. viii. casus Cos7nicus to indicate the setting marked (c),
4) are the following:- that is, the Occasus Matutinus Verzts, but Ideler
(a)'ErlTroX4jl Ea ahA tOv17, G. -'E'Ca rUvvra- (Historische Unl-ersuchlunen, &c. p. 311), while he
roAj &arOLZvJ, P. - Ortzs Alatuetinzis Verus. True interprets Osetus Cosmiczs in the sense usually remorning rising. ceived, applies Occasts Cosmicus to the setting
(b)'Erroch7 Eo7repfa a&XrlJvOi, G. -'Eo-7repia marked (y), that is, to the Occasus JLiatutiZLus
arvvaaTroNXl a&,Oiv'i, P.-Ortus Vespertinuis TFest-s. Ajpal ens.
True evening rising. Again, the epithet dacpo'vvXos appears to be
(c) qAuois iEca da'xvm5, G. -'Eda orrvyaTda- first used by Theophrastus (De Signis Pluv. et Vent.
&uets daAhv1Op', P. — Occasus Mattztinus Vetus. cap. i. ~ 2) where dva'ToXal aticp6YvXo1 are alone
True morning setting. mentioned, and are distinctly explained to ilean
(d) AValrS Eaorepta daAX70zv, G. -'Eao'repla the rising of a star at sunset, that is, the Ortzes
auyIcaT Iva rr asOmvij, P. - Occasus Vespesrtinus Vespertinus Verus marked (b), and in this sense
1Verzs. True evening setting. the phrase Ortus Acronyclhus is found in the trea(a)'EwrrLoTX EY.a mavofci'vl, G.-'Eea irpoava-'tises of Petavius and others who employ also the
TroakJ oaLV0cEmq, P.-Orts8 ialatutius Apparens expression Occasus Acronychus to indicate the sets. Oitus Heliacus. Heliacal rising, i. e. First visible ting marked (d), that is, the Occasus Vispe/etinus
rising of a star in the morning twilight. Verus. Ideler concurs in the latter, but interprets
(/3)'E7rsroAXj ea-repfa ipaiVoEYu', G. —'Eorepta Ortus Acronychus to mean the rising marked (/3),
&rayvaroAM pa'!rotAErV, P. - Ortus Vesperinus that is, the Ortus Vespertinus Apparens. This view
Apparens. Last visible rising of a tar after is certainly at variance with the words of Theosunset. phrastus, which are quite explicit and are cor(y) AaRs Ealia (pawvoEt'lV, G.-'ESa?. rpd6vus roborated by Julius Firmicus (ii. 8); but on the