CELESTIAL BODIES, appear-
ances of the, as feen by the
naked eye, 71-91. as feen
through telescopes, 92—137.

ted, 273.

described, 682. machinery,
666-681. quadrants, 686--
695. Sector, 696. Tables, how
to conftruct, 563. writings, 70.
ASTRONOMY, etymology of, de-
finition of, fublimity and ufe-
fulncfs, 3. antiquity of, 4-20.
hiftory of, 4-69. various fyf-
tems of, 248-256. the true
fyftem of, 257, 272.
ATHENIANS erect a ftatue to

Berofus the aftronomer, 28.
ATLANTIC ocean, tides in the,
lefs than in the Pacific, 477.
ATMOSPHERE, a lunar, argu-
ments against the existence of,
161. anfwered, 162-169.
ATMOSPHERE, fuppofed to have
aerial tides, 481. light refract-
ed by it, 497-501.
ATMOSPHERES, Venus and
Mars have, 107, 108.
ATTRACTION of the great moun-
tains, affects the plumb-line,
61. Dr Herfchel's ideas of the
effects of attraction upon the
heavenly bodies, 220--226. a
queftion refpecting attraction,
243. it power fuppofed to be
balanced by projectile forces,
245. effects of attraction on the
motions of the planets, 282--
344.

AURORA BOREALIS, affinity be-
tween the, and the tails of
comets, 192, 193.
Axis of the earth defcribed, 390,

421.

AZIMUTH CIRCLE, utility of the,
694. how to adjust it, 708.

B.
BALTIC Ocean has no fenfible
tides, 480.
BEARDEDCOMET, explained, 133.
BELTS. See JUPITER.
BENARES, a celebrated obferva-
tory at, 12.
BLACK SEA has no fenfible tides,
480.

BODIES of the fun and planets

deferibed, 332-336.
BULL'S EYE, more foutherly
than the ancients placed it,

.245.

C,

CALIPPIC PERIOD corrected by
Hipparchus, 31.
CARTESIAN System, 256.

CHALDEA, a country proper for
aftronomical obfervation, 19.
CHALDEANS, early aftronomers,
13, 19, 20.
CHINESE, faid to have been
taught aftronomy by Noah, 8.
their fuperftition, 660.
CHRONOLOGY, eclipfes ufeful
in, 661.

CIRCLES defcribed by the plan-
ets, 347-355.
COLD, caufe of, in winter, 424
-426.

COMETS, written on by Mullar,
40. obferved by Werner, 42.
and Hevelius, 46. their paths
difcovered by Kepler, 49.
their places obferved, and ele-
ments computed by Dr Brad-
ley, 62. their number and ap-
pearances to the eye, 81. ap-
parent magnitudes, 82. ap-
pearances through telescopes,
130-134. of their tails, 132-
134. conjectures refpecting
comets, 171-178. conclufions
drawn from obfervation, 180.
-202. numbers noticed, 260.
their nature and motions, 327
-331. fais to occafion eclipfes
of the fun, 665.
CONJUNCTION of Jupiter and
Saturn, obferved by Tycho
Brahe, 48.

CONJUNCTIONS of planets de-
fined, 359. mark of, 360.
CONSTELLATIONS, number of
the Chinese, 8. how marked, 9.
when first used by the Greeks,
23, 24. names of the ancient,
548. and modern, 549, 550.
number of ftars in each, 548-
550.
COPERNICAN SYSTEM publish-
ed, 43. improved, 44. ac-
count of it, 257-272. much
cppofed at firft, 258. confirm-
ed by Newton, 259.
CRABTREE, Mr, fee the first
tranfit of Venus ever obierved,
52, 537-

CRYSTALLINE HEAVENS, an
erroneous notion in the Ptole-
maic System, 251.
D.

DARKNESSES, extraordinary,
fuppofed to be caufed by co-
mets, 187, 665.
DELUGE, fuppofed to have been
caused by a comet, 195.

DICHOTOMY of the moon, ufed
by Ariftarchus to determine
the fun's distance, 29.
DIFFRACTION of rays, defized,

168.

DIRECT MOTION of a planet
defined, 378.

DIURNAL rotations of the fua
and planets, 271. of the earth
illuftrated, 411-414.
DRUIDS early aftronomers, 28.
E.

EARTH, the figure of the, difpute
concerning, 61. mean deality
of matter in it, 68. the motion
of, maintained by Pythagoras
and Nicetas, 257. its revolu.
tion, diurnal rotation, prepor
tional denfity, &c. 250-272
diftance from the fun, 386. da
meter and motion, ib. form,
387, 388, 389.angle of its axis,
39c. its motion round the fun,
ib.proved, 391-401.objectice.
402. moves on its axis, 433-
410, its motions illuftrated, 411
-431. appears as a moon to
the Lunarians, 435. and the
biggest body in the univerte, b
ECLIPSES, the theory of, koura
to the Chinese, 10. accounts of,
collected by Hipparchus, 51.
preliminary obfervations re
fpecting, 570-382, ruks
and examples for calculating,
583, 584-649. for a gra
folar eclipfe, 650-657-cclip-
fes of Jupiter's fatellites, 644-
cometary eclipfes, 665. cza
fes of, explained, 676.
ECLIPTIC, obliquity of the, is
Ptolemy's time, 29. fxd Ir
Albategnius, 34. obferved b
Arzachel, 35. corrected by
Werner, 42. derivation of ur
name, 349. how to frd the
ecliptic, 350 352, and its co-
liquity, 553. it is lefs then in
Ptolemy's time, 554. the b
cliptic, is comprehended in
zodiac, 546.
EGYPT, a country proper år
aftronomical obfervations. I »
ELECTRIC FLUID, fuppoff
Hamilton, to be brought h
to the planets by conats, an
ELLIPTICAL ORBITS of
nets, difcovered by Ko
49. of Saturn's fatellites
ar comets, very excentra,
ELONGATION

ELONGATION, greateft, of infe-
rior planets, 272. defined, 361.
EPHEMERIDES made by Pur-
bach, 40.

phænomena, ib.-118. other,
phænomena, 264, 267, 2703
271, 272. attractive power of
Jupiter, 301, 301. motion
of light from Jupiter to the
earth, 396, his fatellites often
eclipfed, 664.

HARVEST MOON rifes fooner
than any other, 482. reafons
of this, 483-488. goes through
a courfe of more and lefs be-
neficial ftates, 489.
HEAT of comets, Newton's efti-
mate of the, 194.
HEAVENS, general appearance of
the, 74. divifions of the ftarry,

EPICYCLE, a term in the Ptole-

maic, System, 252.
EQUINOCTIAL, obliquity of the,
421. caufe of the feafons, ib.
EQUINOXES, preceffion of the,
calculated, 34, 42.
EVENING STAR, 77.
EXCENTRICITIES of the planets,
270. how to determine, 561.
EXCENTRICITY of the earth's
orbit, rule to determine, 560.
EXCENTRICS, a term in the
Ptolemaic System, 252.
F.

FACULE of the fun explained, 97.
FALLING BODIES, velocity of,
303, 304.

FIELDS OF STARS defined, 212.
Fо-нI, emperor of China, taught
the Chinese aftronomy, 80.
FORCES, CENTRAL, explained

273-

G.

GALAXY. See MILKY WAY.
GEOCENTRIC LATITUDE defi-
ned, 353.

GEOCENTRIC MOTION explain-

ed, 361, 362, 370.
GEOMETRY introduced into af-
tronomy, 27.
GEORGIAN PLANET, difco-
GEORGIUM SIDUS,vered by
Dr Herschel, 96. has two fa-
tellites, ib. 128. its diftance
from the fun, 69. its apparent
magnitude, 128. fuppofed fize
of the fatellites, ib. periods of
revolutions and distances, 129.
GLOBE, the improved celeftial,
defcribed, 677-678.
GNOMON, the ufe of a, known
to the Chinese, 10. ufed by
Pythoas, 28., one erected at
Bologna, 59.
GRAVITATION

defined, 289.
its, effects on the planets, 290
-298. and fatellites, 300-
308. on the moon in particu-
lar, 306-319. illuftrated, 320
-326. is diffused through the
whole fubftance of the celef-
tial bodies, 332-344.
GRAVITY, various effects of, 275,
306. illuftrated, 276-281.
GREEKS, probable origin of
their aftronomy, 23, 24, 25,
Vitruvius's account of it, 23.
H.

HALLEY, Dr, examines Heveli-
us's inftruments, 54. and
makes obfervations along with
him, ib. makes a catalogue of
the fixed stars, 60. makes ta-
bles of the comets, 197, 198.
VOL. II. PART II,

542-550.
HELIOCENTRIC CIRCLES defi-
ned and defcribed 347, 349.
HELIOCENTRIC LATITUDE, de-
fined, 353.
HERSCHEL, Dr, improves the
reflecting telescope, 59. con-
ftructs very powerful ones,
69. difcovers a new planet
with fatellites, ib. his obfer-
vations on Venus, 107. and
Mars, 108. he difcovers two
rings round Saturn, 122-124.
a fixth and feventh fatellite,
125. and vaft numbers of ne-
bulæ, 137. he obferves erup-
tions of the lunar volcanoes,
158. forms a new theory of
the universe, 210, 211. his
theory of the heavens, 221-
of nebulous ftrata, 233-
242. He propofes to afcertain
the parallax of the flars, 539.
HERSCHEL, the new planet fo
named by foreign aftrono-
mers, 69. See GEORGIUM
SIDUS.

229.

HORIZONTAL PARALLAX, defi-
ned, 522. how to find it, 523.
HORIZONTAL SUN and MOON,
apparent magnitude of the,
490. accounted for by Alha-
zen, 491. Des Cartes and
Wallis, 492, 493. Dr Defa-
guliers, 494, and Dr Smith,
495. probable cause, 496.
HUENNA, Tycho Brahe builds
an obfervatory on, 48.
I. J.

INCLINATIONS of the planets to
the ecliptic, 271.
INDIANS, early aftronomers, 14.
INFERIOR PLANETS defined, 354.
INSTRUMENTS defcribed, 682

K.

KPELER'S LAWS, 283-285. il
luftrated, 286-289.

L.
LATITUDE of a planet defined

353. of a place, direction for
finding the, 552.

LIGHT, progreffive motion of
difcovered, 59, 395 propor
tions of, in the planets, 272.
velocity and aberration of, 396
-402. afford evidence of the
motion of the earth, 395, 409
-411. illuftrated, 412-414
quantity of, afforded by the
earth to the moon, 435. re-
fraction of, by the atmosphere,
197 501.

LOCAL ZODIAC, defcribed, 355.
LONDON BRIDGE, time of the
tides arriving at, 478.
LONGITUDE, method of finding
the, propofed by Wernet, 42.
by Dr Halley, 60. executed, ib.
Longitude of a celestial phæ.
nomenon defined, 357. of pla-
ces, easily found in the moon,
438. eclipfes ufeful in deter.
mining it, 661, 664.
LOOPED CURVES of the planets

defcribed, 375-377, 493
LUNAR ECLIPSES, two happen
annually, 602. one vifible, the
other not, 603. Rules for cal-
culating, 610-628. exempli-
fied, 676.
LUNAR TABLES completed, 63.

fhow the moon's place trueit
in the syzygies, 627, 628.
LUNARIANS, appearances of the

earth to the, 435, 436, 442.
have always equal day and
night, 437-439.
LUNATIONS, no complete num-
ber of, finished without a frac
tion, 580. See Moon.

.

MATTER, univerfal attraction of,
proved, 68, 291, 332-344.
denfity of, in the earth, 68,
291, and planets, 346. quantity
ot, in the fuperior planets, 345.
MEAN DISTANCES of the pla-

nets, 270.

MEDITERRANEAN SEA has no
tides, 480.

MERCURY, appearance of, to the
eye, 76. and through a tele-
fcope, 106. has phases fimilar
to thofe of the moon, ib. 264.
feen in conjunction with the
fun, 364. and pafling over his
difk, 365. when he will be thus
feen again, ib. his motion une-
qual, 366.

MERIDIAN, Fules for finding the,
708, 713.

MERIDIAN LINE, rules for draw-

ing a, 502, 507.
MICROMETER improved, 58. ne-
ceifary for meafuring angular
diftances, 685.

MILKY WAY, appearance of the
90. Dr Herichel difcovers in-
numerable multitudes of ftars
in it, 212. he views it by fields
ib. and supposes the fun to be
in it, 216. he gauges it, 220.
MONTH, fynodical and periodi-
cal, defined, 565.
Mean, acceleration of the, de-
termined by Ebn Younis's ob-
fervations, 35. difcovered by
Dr Halley, 60. her appearan
ces to the eye, 72. and thro'
a telescope, 104, 105. number
and names of her principal
ipots, 105. great inequalities
on her furface, 156.fuppofed to
be mountainous, ib. attempts
made to measure their height,
157. Dr Herfchel's eftim te,

fimilarity between them
and terreftrial mountains, 158.
volcanoes among them, ib.
conjectures refpe&ting the
meon's fubftance, 159. and
her fpots, 16c. controverfy a-
bout her having an atmof
phere, 161-169. arguments
for the negative, 161. and for
the affirmative, 162–165. a
luminous ring around her, in
total eclipfcs, 166. experi-
10en's refpeéting it, 167. re-
inark, 168, 169, inquiry whe,
ther the moon is inhabited,
170. her fuifice rough and
uneven, 203. her orbit and
motion, 201. 02. illuftrated,
303-326. hur conjunctions,
&c. 359, 30. and peculiar
pbanctaena, 433-447, the in,
fecrees the tides, 448-480.
proportion of her icke to

O.
OBSERVATORIES, the towers of
Babel and Belus fuppofed to
be, 19. the pyramids of Egypt
probably used as fuch, ib.
OBSERVATORY defcribed, 68:
the portable, defcription c

704-714.

that of the fun in moving the NORTH POLE STAR, appearance
fea, 457. her appearance at
of the, 73, 74.
the full in harvest, 482. caufes
of it, 483-489. appearance
near the horizon, 490. vari-
ous reafons affigned for it, ib.
-496. inequalities of her
motions, 564. how to find her
diurnal and horary motions,
&c. 567-569. caufes of her
eclipfes, 570-582. rules for
calculating them, 584-628.
to find her way from the fun,
629-634. her colour, &c.
during an eclipfe, 658, 659.
her diftance from the earth
lefs than formerly, 662. her
various phafes exemplified,
672-6745 676.
MORNING STAR, 77.
MOTION, planetary, laws of,
285-285.363-325. of light,

395-402.

Morions of comets, 327-331.
of planets in antecedence and
confequence, defined, 355. di-
re&, 363, 378. and retrograde,
363, 379. progre five of light,
409, 410. annual and diurnal
of the earth, 411-414, 5II.

N.
NAUTICAL ALMANACK annual-
ly published, 67.
NAUTICAL EPHEMERIS publifh-
ed, 63.

NEAP TIDES, caufe of the, 453,

470, 474.

NEBULA explained, 137. vaft
numbers of, difcovered by Dr
Herfchel, ib. his account of
them, 214-233-
NEW STARS, account of feveral,
84-89.

NEWTON, Sir Ifaac, conftructs
reflectors with fpherical fpe-
culums, 6. brings fpeculative
aftronomy to perfection, 57.
determines the figure of the
earth, 61. difcovers the true
motion of comets, 180. is of
opinion that they are opaque
bodies, 183, and that their
tails are a thin vapour, expell-
ed by the heat, 189. his efti-
mate of the heat of comets
194. he confirms the Coper
nican fyftem, 259. lays down
the laws of motion, ib. and
gravity, 25. 281. his argu-
ment against the ctunity of
the world, 299.
NODES defined, 260. how to

find the motion of the meon's
323, 224. line of the nodes,
defined, 354.
NONAGISIMAL degree defned
443.

.mark

OCCULTATION of Jupiter, by
the moon, obferved, 54.
OCTANTS of the moon defcri-
bed, 448.
OPPOSITION defined, 359.1
of, 360.
ORBITS, of the planets, inclina.
tions of the, to the ecliptic,.1
defcribed, 282-298, of the
fecondary planets, 320-13f,
their excentricities, 360-pl
ORION, number of stars in, 1.
ORRERY erected by Archimethy
30 defcription of the greed,
made for king George I. 1.
of Mr Ferguton's, 665-674
OSYMANDYAS, an aftronomic
circle in the monument of ly
P.
PARABOLA of a comet, method
of finding the, 319.
PENDULUM, a tent of velocity,
304. caufe of its vibratkan,
333. vibrates quickeft near the
poles, 405.
PENDULUM
683.
PENUMBRA, rule to find the
place touched by the, 6:
PERIGEE defined, 372, 381.
PERIOD of eclipics, &c. f
ECLIPSES.

CLOCK deferbed,

PERIODICAL revolutions,

ત

and times of the plants,
PISCES and Aries, appete
of the moon in, 433–485.
PLANETARIUM, erected by a
chimedes, 30. Mr June
fcribed, 675.
PLANETS, a theory of the, with
by Muller, 40. their appe
ces to the eye, 75-8a ruD
her, 75. apparent magata
8o. and motions, ib. Sept
fed by Kepler to be huge
mals, who fwim read t
fun by means of fits! 1-
Planets ditturb the motions vā
comets, 202. Their Ins
and order, 260. are all epage
bodies, 263. and fphorical, s
their periods, diftances, a csa
centricities, 270.
planets, scc-126, them a
cles defined and dec
347-2529 355. their th
353–356. and long tree,
conjunctions, opp titles

afpects, 359-368. ftationary
appearances, 369-373. appa-
rent paths, 374, 375. motions,
376, 377. direct. 378. and retro-
grade, 379. in apogee and pe-
rigee, 372, 381. periods of re-
turn, 382-385. rules for find.
ing the parallax of planets, 522
-533 their diftances, 534-

536. and periodical times, 559,
PLEIADES, number of stars in,
136.

POLE of the heavens, how to find

the altitude of the, 552, 654.
POLES defined, as ufed by Herf-
chel, 237.

POLES of the earth, bodies hea-

vieft, when near the, 405.
PROGRESSIVE MOTION of light
proves the motions of the
earth, 395-414.
PROJECTILE FORCES, fuppofed
by Dr Herfchel, to counter-act
the power of attraction, 245.
rendered probable by changes
of the politions of ftars, 246.
PROPORTIONAL DISTANCES of
the planets from the fun, 270.
PROPORTIONS of light, heat,
bulk, and density of the pla-

nets, 272.

PYTHAGOREAN fyftem of aftro-
nomy, taught by Philolaus,
26. and Ariftarchus, 29. car-
ried into Italy, Gaul, and E-
gypt, 27, 28. restored, 43.250.
PYTHAGOREANS held comets to
be of the nature of planets, 172.
Q.
QUADRANT, MURAL, described,
687-693.

QUADRANT, PORTABLE, defcri-

bed, 694, 695.
QUADRANT, REFLECTING, in-
vented, 57.
QUADRATURE defined, 359,360.
R.

REFRACTION of light by the at-

mosphere, 497. illuftrated, 498
-501.
REFRACTIONS, the ufe of, in af-

tronomy, fhown by Alhazen,
35. and Vitello, 38.
RETROGRADE MOTION of a pla-
net, defined, 363.
REVOLUTION of the heavens,
not a real motion, 411.
RIGHT ASCENSION of the ftars,
rule for finding the, 556, 557.
RING. See SATURN.
S.
SAMARCAND, the latitude of, de-
termined by Ulug Beg, 36.
SATELLITES, four revolve round
Jupiter, 111. feven around Sa-
turn, 126. and two around
Herfchel, 128.

SATURN, his ring difcovered, 51.
119. and five of his fatellites,
55 his appearance to the na-
ked eye, 79. and through a
telescope, 119. his ring defcri-
bed, 120, 121. found by Dr
Herfchel to be double, 122.
not changeable, 123. period of
his revolution, 124. and feven
fatellites in all, 125. their pe-
riodical revolutions and diftan-
ces, 126. the revolution of Sa-
turn retarded 13 days, by the
approach of Jupiter, 199. phæ-
nomena of Saturn's ring, 266.
mutual attraction between Ju-
piter and Saturn, 296, 297.

their power, 302.
SEA, the ebbing and flowing of
the, caufes of, 449—467.
SEASONS, caufes of the, 415-

429. had fallen back, 430. rec-
tified by the new ftyle, ib. 41.
SECTOR, EQUATORIAL, deferi-
bed, 696-699.

SEMITA LUMINOSA, explained

STARS, FIXED, catalogues of the,
made by Hipparchus, 31. U-
lug Beg, 36. William IV. of
Heile, 47. Tycho Brahe, 48.
Dr Flamstead, 59. Dr Halley,
60, and Dr Herfchel, 69. their
aberration discovered, 57. ap-
pearances to the eye, 73-75.
moft numerous in the northern
part of the heavens, 73-75.
moft numerous in the northern
part of the heavens, 73. liable
to changes, 83. their appear-
ances through telescopes, 135
-137, fuppofed to be funs,
203209. Dr Herfchel's theo-
ry, 210, 211, and obfervations
of innumerable multitudes of
fars, 212-242. his inferences,
Zzzzz

243. apparent changes of itars,
246. are fituated at an im-
menfe distance, 261. fhine by
their own light, ib. no method
found to afcertain their dif-
tance, 538. conjecture as to it,
539. Dr Herfchel's method,
540. ftill infufficient, 541. di-
vifions of the stars, 542-350.
number of in the conftellations,
548-550. how to find their
right afcenfion, 556, 557. lon-
gitude and latitude, 558.
STYLE, reason for the change of,

430, 431.

SUN, fpots on the, discovered,
51. his parallax and diftanse
computed, 65. his appearance
to the eye, 71. and through a
telefcope, 92-103. his fpots
obferved by Galileo, Scheiner,
and Harriot, about the fame
time, ib. 93. variety and di-
mentions of them, 94. fubjeét
to increafe and diminution, 95
-97. their velocity, 98. and.
uniform motion from E. to
W. ib. other phænomena re-
fpecting them, 99-103, Dr
Long's account of them, 144,
145. how to find the time of
their revolutions, 146, 147,
different opinions concerning
them, 148. Dr Willon's, 149
-154. an experiment propo-
fed, 155. the fun fuppofed to
be not in the centre of the u-
niverfe, 216. is at an immenfe
diftance, 262. mutual gravi-
tation between the fun and
primary planets, 289-297.
action of the fun upon the
fecondary planets, 300-326.
proportion of his action on
both, 335-344. his conjunc-
tions with the planets, 359-
385. is immenfely larger than
the earth, 391, 392. proofs.
that the earth moves round the
fun, 393-414. and that the
fun moves round his axis, 403.
404. he is higher in fummer
than in winter, 422. and more
diftant, 424. reafons of his fu-
perior heat, ib.-426. periods
of his completing a tropical
and fiderial year, 427. appears
to fall back with regard to
the flars, 418. reafons for his
magnitude near the horizon,
490-496. the motion of the
fun illuftrated, by supposing a
fetitious fun to move equa-
bly, 513-521. the fun's paral-
lax, the most important prob
lem in aftronomy, 536. how
to find the fun's declination,

555-

$55. and the moon's way from
the fun, 629-634. to calcu-
late eclipfes of the fun, 635-
637.

SYNOPSIS of the fun and pla-

nets, 269-272.
SYSTEMS of aftronomy, account
of the most famous, 248-
281. of the Pythagorean, 250.
Ptolomæan, 251-2:53. Ty-
chonic, 254. Semi-Tychonic,
255. Cartefian, 256. and Co.
pernican, 257-281.
T.

TABLES, aftronomical,, publish-
ed, 38, 49, 60, 63, 552. how
to conftruct, 563.
TAILS of comets, various thec

ries refpecting, 188-193. One
comet has fometimes feveral
tails, 192. They are probably
ftreams of electric matter, 193.
TELESCOPES, improvement of,
54-59. various kinds of, 684,
690, 700, 704 how to point,

TRAJECTORUM LUNARE, de-
fcribed, 679-681.
TRANSIT INSTRUMENT, defcri-
bed, 700-703.
TRINE ASPECT, definition and
mark of a, 360.

TROPIC of Cancer defcribed,
417. of Capricorn, 419.
TWILIGHT, caufe of the, 500,
501.

TYCHONIC SYSTEM, account of
the, 254.

U. V.

VELOCITY of the fpots on the
fun, 98. of comets greatest in
their perihelion, 182. of bo-
dies, phænomena of the, 274.
303, 304. of the earth, 386.
of light, 396.
VENUS, the firft tranfit of, ever
obferved, 52, the 2d and 3d
obferved in various places, 65.
inferences, ib. her appearance
to the eye, 77. and through a
telefcope, 107. her phases and
changes fimilar to thofe of the
moon, ib. were firft obferved
by Galileo, ib. Dr Herschel's
obfervations and inferences, ib.
fhe has an atmosphere and is
larger than the earth, ib. pe-
riods of her tranfits, 365. her
apparent paths, 374. and mo-
tions, 382, 383. rules for cal-
culating her parallax, 531,532.
535, 536. advantage of obfer-
ving her tranfits, 536. hiftory
of them, 537. Venus's path
traced, 558.

VERNIER defcribed, 691, 692.
VIBRATION of pendulums, caufe
of the, 333.

VISIBLE ECLIPSES, number of,
in the year, 603.
UMBRA on the fun defined, 100,