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Of the Precession of the Equinoxes .

.: 319

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

wards, or in antecedentia, upon the Celestial Globe.. 320

2. To rectify the Celestial Globe

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...,

327

6.

the Length of the Day in Latitudes under 661
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 length 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

Il. 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

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

the Sun's Amplitude.....

ibid.

21.

the Sun's Altitude at a given Hour

22.

when the Sun is due east in a given Latitude.. 349

23.

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

24.

the liour of the Day, the Altitude and Azimuth

of a Star being given....

351

25.

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

26.

the Azimutb, &c. at any Hour of the Night.... 353

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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 354

29.

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

ibid.

30.
the Hour by Data from two Stars....

355

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 stars

357

34.
when a Star rises or sets cosmically

353

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.

363

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..

368

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....

376

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.

48. To find the Latitude, &c. of a Comet....

385

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

ibid.

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

386

51. 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,

and Lunarium...

391

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ASTRONOMICAL

ESSAYS.

ESSAY I,

PART 1.

MANKIND have in all ages been desirous of forme ing 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 mụst 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 ús 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.

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 pupik 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 hinn 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 attained, 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 universals of this science, the knowledge of particulars will be fendered facile and clear.

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