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JROB. I

Of the Precession'of the Equinoxes ................... . 319

1. To represent the Motions of tite Equinoctial Points back-

wards, or in antecr dentiii, upon the Celestial Globe. . 320

2. To rectify the Celestial Globs .................... 324

3. To find the Declination and right Ascension of the Sun. . 326

4. To find the Sun's oblique Ascension, &c ............. ibid.

5. - the Sun's meridian Altitude ................ 32F

6. - the Length of the Day in Latitudes under 66J

Degrees ...................... . ............. ibid.

7. • - the Length of the longest and shortest day in

Latitudes under 66| Degrees ................. 328

8. •• the Latitude where the longest day may be of

any given lenglh between twelve and twenty-four
Hours ................ ibid.

9. - the Time of Sun-rising, &c ................. 329

10. * - how long, &c. the Sun shines in any Place within

the Polar Circle .. .......................... 330

11. To illustrate the Equation of Time, &c ............. 334

12. To find the right Ascension, &c. of a Star ........... . 336

13. — — — - the Latitude and Longitude of a Star ..... ... ibid.

14. • - the Place of a Star on the Globe by, &c ....... 337

15. - at what Hour a given Star transits the Meri.

dian ................ ibid.

16. On what Day a Star will come to the Meridian ...... 338

17. To represent the Face of the Heavens for any given day

and hour . — .... ...... . ................... ibid.

18. To trace the Circles of the Sphere in the Heavens .... 341

19. To find the Circle of perpetual Apparition .......... 346

20. - the Sun's Amplitude ................ . ..... ibid.

21. • - the Sun's Altitude fct a given Hour .....' ..... 347

22. - Then the Sun is due east in a given Latitude. . 349

23. - the Rising, Setting, Culminating, &c. of a Star» . 350

?4. - — ' - the Hour of the Day, the Altitude and Azimuth

of a Star being given ......................... . 351

25. -- - the Altitude and Azimuth of a Star, &c. ...... 352

$8. _ - the Azimuth, &c. at any Hour of the Night.... 353

Ft1OB.

27. To find the Sun's Altitude, and the Hour, from the Lati-

tude, the Sun's Place, and Azimuth .............. ibid.

28. - the Hour, the Latitude and Azimuth given .... 351

29. - -a Star, the Latitude, Sun's Place, Hour, &c.

given ........ . ......... . .............. ... ibid.

30. - the Hour by Data from two Stars ............ 35S

.31. - the Hour by Data from two Stars ............ 356

32. -- the Latitude by Data from two Stars ..... , . . . . ibid.

33. The Latitude by other Data from two star .......... 357

34. - when a Star rises or sets cosmicaUy .......... 358

35. -- when a Star rises or sets achronically ... ..... 369

36. . , — . when a Star will rise heliacally ...... . ..... 361

37. - when a Star will set heliacally .............. 362

Of the Correspondence between the Celestial and Terrestrial

Spheres ................ 368

38. To find the Place of a Planet, &c .................. 366

39. --- what Planets are above the Horizon. .... ...... 367

40. - the right Ascension, &c. of a Planet .......... 36$

41. — - the Moon's Place. ....................... 374

42.' the Moon's Declination .................... 375

43. - the Moon's greatest and least Meridian Alti-

tude ...... . ................... . ....... .... ibid.

44. To illustrate the Harvest Moon ............ „ . ...... 37S

45. To find the Azimuth of the Moon, and thence High

Water, &c ................ 381

Of Comets .................... ....... .......... ... 382

46. To rectify the Globe for the Place of Observation ____ 384

47. To determine the Place of a Comet .............. ibid.

43. To find the Latitude, &c. of a Comet ................ 38S

49. To find the Time of a Comet's Rising, &c . . ..»», ...... ibid.

50. To find the same at London ....... . .............. 386

iI. To determine the Place of a Comet from an Observation

made at London ............................ ibid.

52. From two given Places to assign the Comet's path.... 387

53. To estimate the Velocity of a Comet .............. 388

54. To represent the general Phenomena of a Comet ...... ibid.

A Description of the most improved Planetarium, Tellurian,

x and Luuarium. ............ . ................ 391

ASTRONOMICAL

E«O O A
O O A

ESSAY I.

PART L

*

Mankind have in all ages been desirous of forming rational conceptions of the nature and motion of those bodies that appear in the vast concave above their heads. Amidst the infinite variety of objects which surround them on every side, the heavenly bodies must have been amongst those which first attracted their attention. They are of all objects the most conspicuous, the most important, and the most beautiful.

Astronomy instructs us in the laws, or rules, that govern and direct the motions of the heavenly host. It weighs and considers the powers by which they circulate in their orbs. It enables us to discover their size, determine their distance, explain their various phenomena, and correct the fallacies of the senses by the light of truth.

A

~ Astronomy is not merely a speculative science; its use is as extensive as its researches are sublime. Navigation owns it for its guide; by it, commerce has been extended and geography improved. It is astronomical observations that form the basis of geography. Thus, it has co-operated with other causes* in the greatest of all works, the diffusion of knowledge and the civilization of man.

As, in order to attain an accurate idea of any piece of mechanism, it is best to begin our investigation by an examination of those parts which give motion to the rest, the primary causes of those effects for which the machine was made; so the young pupils will more easily gain a just idea of the motion of the heavenly bodies, by considering them as seen from the; sun, the centre of our system, and the, principal agent used by the Lord Of Nature for conducting and regulating the planetary system.

It will not be difficult, after this, to inform hifli how those appearances are to be accounted for, that arise from his particular situation; whence he views the heavens from a point which is not in the centre of the system, and is consequently the source of many apparent irregularities. This knowledge at., tained, it will be easy to prove to him, that the real and apparent motions of the heavenly bodies are frequently the reverse of each other. For, being by this means put into possession of the universak of this science, the knowledge of particulars will be tendered facile and clear

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