WITHOUT THE GLOBE.

Reduce the number of hours between the given time and noon into degrees, and it will be the difference of longitude between the places.

When the given hour is in the morning, the place where it is noon will ie so many degrees to the eastward: hence the difference of longitude must be added to the longitude of the given place, if it be E.; but subtracted from it, if it be W.

When the hour is in the evening, the places where it is noon will lie to the westward of the given place: hence the difference of longitude must be added, if the longitude of the given place be W.; but subtracted, if it be E.;-and the sum, or difference, will be the longitude of the places required.

1. If, in subtracting, the difference of longitude be greater than the longitude of the given place, subtract the later from the former,-and the remainder, of a contrary name, will be the longitude of the places required.

2. If, in adding, the sum exceeds 180°, subtract it from 360°, and the remainder will be the required longitude, but of a contrary name.

3. By this problem, it may also be found where it is any other given hour; only, instead of turning the globe till the index points to 12, turn it till it points to the given hour.

EXAMPLES.

1. Where is it noon, when it is 5 o'clock p. m. at Paris?

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Calculation.

5 hours 70° the difference of longitude. As the given hour is in the evening, the places where it is noon will lie to the west. The longitude of Paris is 2° 20′ E.: from this, according to the rule, 75° ought to be subtracted; but as that cannot be done, subtract 2° 20' from 75°, (by note 1), and the remainder, 72° 40′, will be the longitude of the places required, and will be W. being of a contrary name.

The places answering to this are,

Labrador, New England, and Pennsylvania, in North

America; Hispaniola; Terra Firma, Peru, &c. in South America.

312. Where is it noon, when it is 9 a. m. at Newcastle?

Answ. Nisney Novogorod, a town on the Wolga, in Russia; Armenia and Georgia, west of the Caspian Sea; Bagdad, a town on the river Tigris, in Irak Arabia; the middle parts of Arabia; Mocha, a sea-port of Arabia, on the Red Sea; the Strait of Babelmandel; the north-east part of Africa; and the western coast of Madagascar..

3. When it is 7 a. m. at Port Royal, in Jamaica, where is it noon?

Answ. At London, and all other places which are situated under the meridian of London.

4. When it is 40 min, past 2 p. m. at Ispahan, where is it noon?

5. Where is it noon, when it is 1 a. m. at New Zealand? 6. Where is it noon, when it is midnight at London, 7. When it is 7 a. m. at Jerusalem, where is it noon? 8. When it is midnight at Mexico, where is it 8 45 a. m.? 9. Where is it noon, when it is 4 a. m. at Botany Bay? 10. Where is it midnight, when it past 10 a. m. at Bencoolen, in Sumatra ?

11. When it is past 4 in the afternoon at Paris, where is it noon.'

12. When it is past 7 in the morning at Shiraz, where is it noon?

13. When it is noon at London, at what place is it past 8 in the morning?

14. When it is 2 o'clock in the afternoon at London, at what place is it + past 5 in the afternoon?

15. When it is noon at Bombay, where is it past 6 in the morning?

16. When it is midnight at Bursa, where is it 3 o'clock in the afternoon?

17. When it is past 6 in the morning at Quebec, where is it 11 in the forenoon?

QUESTIONS FOR EXAMINATION IN
SECTION III.

What are the horary circles? How does the earth turn on its axis? What is it that produces noon at any place? Whether do the meridians that lie to the east, or those that lie to the west, come soonest opposite to the sun?

How long is the earth in turning on its axis? At what rate does it turn per hour? How is that found? How many degrees of longitude make an hour difference of time? Places that lie in 30° E. L. have they the hours of the day more or less advanced than they are at London?

Having the hour given at any place, how is it found what hour it is at any other place? How is this found on Adams's globe? How is this found by maps? Having the hour given at any place, how is it found where it is noon? How is this found by Adams's globe, and by maps?

QUESTIONS FOR EXERCISE IN SECTION III.

1. When it is ten in the morning at London, what is the time at Calcutta and Canton ?

2. When it is eight in the morning at Dublin, what o'clock is it at the Pelew Islands, Barbadoes, and Lima?

3. When it is midnight at Rome, what o'clock is it at Owhyhee and Easter Island?

4. When it is midnight at Lisbon, what o'clock is it at York, Moscow, Genoa, Syracuse, and Leghorn?

5. How much are the clocks of Barbadoes behind ours?

6. When it is ten in the morning at Port Jackson, what is the hour at Paris and Dublin?

7. When it is nine in the morning at London, what is the hour at Botany Bay?

8. When it is six in the morning at Kingston, in Jamaica, what is the hour in Bombay?

9. When it is one in the afternoon at Dublin, what is the hour at Boston, in New England?

10. Where is it noon, when it is three in the morning at Newcastle?

11. Where is it noon, when it is seven in the evening at Pekin?

12. When it is midnight at Mexico, where is it noon? 13. When it is eleven in the evening at Jamaica, where is it noon?

14. When it is three in the morning at Paris, where is it noon?

15. My watch was well regulated at London, and when I arrived at Madras, which was after a five months' voyage, it was 4 hours 50 min. slower than the clocks there. Had it gained or lost during the voyage, and how much?

16. When it is 7 p. m. at Edinburgh, what is the hour at Washington?

17. When it is 5 p. m. at Philadelphia, where is it mid'night?

18. Are the clocks at Calcutta faster or slower than the clocks at London, and how much?

SECTION IV.

DEFINITIONS.

1. The ecliptic is a great circle in the heavens, described by the earth in its annual motion round the sun; or it is a great circle in the heavens, in which the sun always ap pears to move.

The ecliptic is proper only to the celestial globe; but, on account of its great use in performing many geographical problems, it is always drawn on the terrestrial: it crosses the equator obliquely, and extends 23o 28' to the north of it on one side, and 23° 28′ to the south of it on the other side. The angle which it makes with the equator is called the obliquity of the ecliptic.

It is called the ecliptic, because eclipses generally happen when the moon is in or near this circle: it is divided into 12 equal parts, called signs, each containing 30 degrees; they are thus marked and named:

The winter and spring signs are termed ascending, and the summer and autumnal descending.

2. The tropics are two less circles, parallel to the equator, and distant from it 23° 28': that which lies on the north side is called the tropic of cancer; and that which lies on the south side is called the tropic of capricorn.

The obliquity of the ecliptic determines the distance of the tropics from the equator; as they are drawn parallel to the equator, through those two points of the ecliptic, which are at the greatest distance from it. The northern tropic is called the tropic of cancer, because it passes