look north, and all places even with the wes tern or left hand horizon, the sun is rising to:" To all places even with the eastern horizon the sun is setting: To all places under the upper half of the meridian, it is noon and to all places under the lower half, it is midnight, &c.

Example.-To what countries is the sun ri sing and setting at ten o'Clock on Midsum mer day?

Where is it noon when the sun rises on the 4th May ?

What time does the sun rise at Constanti nople on the 30th April?

When it is eight in the morning with us, on the 17th February, to what countries is the sun then rising and setting?

PROBLEM X.

To find the Length of any Day or Night throughout the Year, at any Place, except the Frigid Zones.

Rule. That half of the globe above the horizon being day, and that beneath night, the circles that northerly or southerly countries describe, by the earth's diurual motion, are

much more unevenly cut by the horizon, than the equatorial countries. Hence there is no difference of day and night at the equator, but great difference towards the poles: This arises from the obliquity of the earth's axis to the plane of the ecliptic; and this difference may be easily found, by first rectifying the globe, then bringing the place to the morning horizon, and either counting the, meridians of the globe from the place to the fixed meridian, (supposing they are 15° from one another) or turning the globe as it does in nature, und counting the hours from the horizon to the meridian: either of these methods will give the length of the forenoon; and (as the afternoon is of the same length) doubling these, gives the length of the day.

Example. What length is the 10th April

at London?

What time does the sun rise at York on the 16th November?

What time does the sun set at Paris January 30th ?

What is the length of July 12th at Rome?

What o'clock does the sun rise on the 6th October at the Cape of Good Hope?

What is the difference, in length, the 5th of May, at Moscow and Pekin?

How much longer is the 5th of November at York, than the same day is at Archangel?

How long is the 1st of June at Cape Horn?

PROBLEM XI.

To find the Length of the longest Day or Night of any Part of the Globe, within Latitude 66°.

Rule. The longest day to all places in the northern hemisphere is the 21st June, and to all places in the southern hemisphere the 21st December. These times are called the solstices, the sun-shining vertically on the Tropic of Cancer, on the 21st June, and on the Tropic of Capricorn, on the 21st December. Hence the northern longest night is the 21st December, and the southern longest night the 21st June; these tropics being 23° from the equator, (the sun's declination being 23) the rectification requires the corresponding pole to be elevated 23°: then any place treated as in the last problem, will shew the length of its day or night.

Example.-What is the length of the longest day at Petersburg?

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What is the first and last days when the sun forsakes, and arrives again to, the people of the North Cape?

PROBLEM XIII.

Any Place being given in the Torrid Zone, to find the two Days of the Year when the Sun will be vertical there.

Rule.-Mark where the place cuts the meridian: chalk it; then move the globe round, and the two parts of the ecliptic which pass under the chalk, direct to the table on the hori zon, which points out the two days.

On what days, and in what months, does the sun pass vertically over St. Helena ?

When will the sun pass vertically over Håvannah ? VIX wɛa conT

When will the Nile begin to swell and overflow?

areere ever the sun is vertical, the rains

near

are almost continual. The waters of the Nile are weeks in flowing from their source to Egypt: and rise not there till the beginning of June, when the Dog star rises with the sun.

What time of the year does the Amazon óverflow?

When does the rainy season commence at Cape Comorin?

When shall a person have no shadow at St. Kitt's?

On what days and hours, at London, will the people of Barbadoes suffer the sun's vertical rays!..

When may we condole with our friends of Madras, for their suffering vertical heat?qlt

PROBLEM XIV.

To find all those Places to which the Sun will be vertical on any given Day.

Rule.-Find the sun's place in the ecliptic, bring it to the meridian, and mark the place with pencil; then turn the globe, and those places which have the sun vertical at their me ridian, will successively pass under the mark. What places does the sun pass vertically over on the 10th May?

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