540
ASTRONOMY.
The ormts of several comets calculated In Dr. llalley, 193,194. |
Sir Isaac Newton ’s remark upon the very eccentric orbits of thecomets, 193.
Sect. XV. Of the Bodies of the Sun and Planets , theQuantity of Matter they contain, and their Densi-ties, (19b-201.)
All bodies made to descend to the surface of our globe with thesame degree of swiftness, 196.
How to lind the quantity of attractive power in a celestial body,197.
Table of the revolutions, magnitudes, distances, eccentricities,densities, &c. Ac. of the Moon and primary planets, 198.
Table of the revolutions, magnitudes, &c. &c. of the Satellites ofJupiter, 199.
Table of the periods, distances, See. of the satellites of Saturn, 200.
Table ot the revolution, distances, &c. of the satellites of Her-schel, 201.
Sect. XVI. Of the Fixed Stars , (202-211.)
The fixed stars how distinguished from the planets, 202.
'1 he distance of the lived stars proved to be immensely great, ibid.
Of the apparent magnitudes of the fixed stars, and their distributioninto constellations, 202, 203.
Table of the ancient constellations, 204.
'l'able of the new Southern constellations, 205.
Table of Ilevelius’s constellations made out of the unformed stars,206.
The number of the fixed stars probably infinite, 207.
A detailed account of the strange variations in many of the fixedstars, ibid.
Supposition of M. De La Place respecting the changes in the fixedstars, ibid.
All the stars seem to have a common and general motion aboutthe pole of the ecliptic, arising from the precession of the equi-noxes, 20S.
Some of the stars observed to have motions peculiar to themselves,ibid.
Of the appearances in the heavens termed nebula:, 209-
Of the galaxy or milky way, ibid.
Dr. HerschtTs discovery that the galaxy is occasioned by theunited light of myriads of myriads of fixed stars, ibid.
The fixed stars are not situated in one plane, but are at immensedistances from one another, 210.
Very probable conjecture that the fixed stars are Suns , each en-lightening its own system of planets, satellites, and comets, ibid.
That tfie Solar System , itself as well as the systems of the stars, arein rapid motion, far from being improbable, ibid.
The immense distance of the lived stars proved from the Earth ’saxis pointing to the same part of the heavens in every part of herorbit, 211.
The aberration of light in the fixed stars discovered by Dr. Brad-ley, ibid.
Light demonstrated to travel through equal spaces in equal times,ibid.
PART II.
Astronomical Operations and Calcuiations, (212-249,)
Sect. I. Of drawing a Meridian Line , (212 - 216.)
Method of drawing a meridian-line by means of a plain board setparallel to the horizon, 212.
Method of drawing a meridian-line by means of two threads andplummets, 213, .214.
Method of drawing a meridian-line by means of a clock or watchwith minutes ami seconds, 215.
Easy method of drawing a meridian-line by means of the solarshadow on an equinoctial day, 216.
Sect. II. Of finding Time and the Equation of I ime,(217-221.)
To find exactly when the Sun ’s centre passes the meridian, 217.
Of solar and sidereal days, 218.
The reason of the difference between mean and true time ex-plained, 218.
Table for the equation of mean anil apparent time, and its me illus-trated by several examples, 220, 221.
Sect. III. Of calculating the Distances, Magnitudes*Sc c. of the Celestial Bodies , (222, 223.)
Horizontal parallax defined and explained, 222.
Different methods of finding the parallax of the celestial bodies, ibid.
The rare phienomenon of a transit of Venus the best method offinding the solar parallax, and from it the true dimensions of theSolar System , ibid.
How to measure the apparent diameter of the Sun or a planet, andfrom it to obtain its circumference, surface, or hulk, 223.
Sect. IV. Of calculating the periodical Times, Places,&c. of the Celestial Bodies ; constructing Astronomi-cal'Fables, AND DELINEATING THE PlIASES OF THE MoON ,(224-235.)
An easy method of finding the altitude of the pole of the heavensat any particular plat e, 224.
How to lind the obliquity of the ecliptic, 225.
Of the constant diminution of the obliquity ot the ecliptic, ibid.
How to find the declination ot the Sun , 226.
A 11 easy method of finding the right ascension of the stars, 227.
How to find the longitude and latitude of a star when its rightascension and decimation are given, 228.
llow to find the periodical times of the planets, 229.
How to lind the inclination ol a planet’s orbit, ibid.
liow to determine the eccentricities, and aphelia of the planets230. ’
Of the construction of Astronomical Tables, 231.
'Fhe great inequalities of the lunar motions render it difficult toconstruct exact 'Fables of the Moon , 232.
How to find the quantity ot a periodical month by means of eclip-ses, ibid.
The Moon ’s diurnal and horary motion easily obtained from thequantity of her periodical months, 233.
Flow to Delineate the phases of the Moon when her distance fromthe Sun is given, 234.
How to lind Hie nodes and apogee of the Moon , 235.
Sect. V. Preliminary Observations respecting Eclipses,(236-238.)
Of the nature of an eclipse, 236. /
Of the cause ol Solar Eclipses , ibid.
Of the cat.se of Lunar Eclipses , ibid.
Oi the limits of Solar and Lunar Eclipses, ibid.
Why eclipses of the Sun and Moon happen so seldom, 236, 237.
Of the periodic return of eclipses, 238.
Sect. VI. Of the Calculation of Eclipses , (239,240.)
Different particulars necessary to be known in the calculating ofSolar and Lunar Eclipses, 239.
Preliminary calculations necessary for the construction of theLunar Eclipse of Sept. 2, 1830, 240.
Sect. VII. Of the Construction of Lunar Eclipses , (241.)
’Flie construction of the greatLunar Eclipse of Sept 2,1830, givenat full length, 241.
Sect. VIII. Of calculating Solar Eclipses , (242-247.)
How to obtain by geometrical constructions the essential requi-sites in calculating Solar Eclipses , 242, 243.
Rules for calculating the eclipse, exemplified in the case of theSun’s Eclipse of June 4, 1769, 244.
Rules for calculating a general eclipse of the Sun , 245.
Preliminary calculations made in order to determine the differentphenomena of the great Solar Eclipse of Sept. 7, 1820, 246.
Geometrical construction of the great Solar Eclipse of 1820, 247.
Sect. IX. Remarks on Eclipses in general, (248.)
Of the reddish appearance of the Moon when eclipsed, 248.
Of the faint light observable on the Moon 's disk in most SolarEclipses, ibid.
Eclipses formerly imagined to be the forerunners of national ca-lamities, ibid.
Eclipses of the Sun and Moon, ’especially those of Jupiter ’s satel-lites, of great use in finding the longitude of places, ibid.
The principal instruments ot me in making astronomical obser-vations, 249,
ASTROSCOPE,