TERRESTRIAL GLOBE.

To find the Longitude of a given place, and its time as compared with that of London or Greenwich.

Repeat the following :

First Meridian, (def. 24); Solar day, (def. 84); True, or Mean Noon, (def. 86). Learn the Tables just preceding.

RULE. Bring the given place to coincide with the graduated surface of the brass meridian, and it will show, as in the last Problem, the plane of its meridian :-The number of degrees of longitude is shown where this plane cuts the Equator. Turn those degrees into minutes of time by multiplying by 4, or into hours, by dividing by 15. If the place be to the east of London, add that time; if to the west subtract it.

If the Pupil stand, as he ought, S. E. of the Globe-surface, he will reckon towards him for east, and from him for west, longitude. The Equator of a twelve-inch Globe is generally subdivided only to half-degrees that of a larger Globe to quarter-degrees, or minutes of time.

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and how much will clocks, correctly set by the sun at these places, differ from the clocks of Greenwich; and whether will they be, behind or in advance of Greenwich clocks?

2. If, after sailing down our coast to Lowestoff, its most eastern town, I cross the country to Land's End, its most western point, how do I find my London watch,

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if performing correctly, when comparing it with the clocks at both of these places?

3. Are the clocks of the following places faster or slower than those of London, and how much:-Petersburg-Cape Town - Philadelphia-Barbadoes-St. Helena-Madras-Batavia-Otaheite ?

4. Each day of the year differs from the day which precedes it with respect to the period at which any fixed star appears on the meridian. On the night of 28th January, Sirius (the Dog Star) comes to the meridians of the following places when their clocks are striking ten: what hours will the clocks of London be showing at these several instants ?-Vienna-New York-Calcutta-Lisbon-Dublin-Port Royal, (Jamaica).

PROBLEM XIII.

CELESTIAL GLOBE.

To find the Latitude in which a certain Star rises or sets at the instant that another certain Star is culminating.

Repeat the following:

Sidereal Day, (def. 83); Astronomical and Civil Reckoning, (def. 82); Right Ascension, (def. 52); Sidereal Clock. (def. 53).

RULE.-Bring the star given as culminating to the brass meridian, and elevate or depress the pole until the other star coincides with the eastern or western part of the horizon. Then the number of degrees on the brass meridian from the elevated pole to the horizon, will show the latitude. N.B. It is important to take the point in the centre of the star's rays for the star's place.

1. In what latitude did I observe Arcturus on the meri dian, when Antares (a of Scorpio) was rising?

Here, by bringing Arcturus to the brass meridian, and arranging the poles until Antares is coinciding with the eastern part of the horizon, I find that declination 60° N. is in the zenith; and that, consequently, the North Pole is elevated 60°.

2. When a of Lyra (Vega) is on the meridian, Algol (of Perseus) is rising, what is the latitude?

3.

Altair (a of Aquila) on the meridian, 8 of Leo Major setting, what is the latitude?

4.

Fomalhaut (of Piscis Australis) on the meri

dian, Rigel rising, what is the latitude ?

5.

a of Crux on the meridian, ɑ of Columba set

ting, what is the latitude?

6.

Sirius (a of Canis Major) culminating, a of Virgo (Spica) rising, what is the latitude.

7. On the 18th of September, the sun appears at a point in the heavens which is scarcely one degree south of B of Virgo in what latitude will Aldebaran set at noon on that day?

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8. On the 28th May, Aldebaran comes to the meridian with the sun. It happened to be full moon exactly at noon of this day at Bath: what was the latitude in which Regulus (in the Lion's heart) was rising at that instant, and how was the moon situated where Regulus was setting instead of rising? (See question 9 of Prob. XI.)

PROBLEM XIV.

TERRESTRIAL GLOBE.

To find a place having its Latitude and Longitude given. Conversely.-Having a place given to find its Latitude and

Longitude.

Repeat the following:

Right Sphere, (def. 49); Parallel Sphere, (def. 50); Oblique Sphere, (def. 51); Oblique Ascension, (def. 54); Oblique Descension, (def. 55).

RULE.-Follow the directions respecting the arrangements of the Globe, and the proper use of the right or left hand, in Problem II. Place the thumb nail

upon the

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given latitude, and bring the given longitude to the brass meridian; then under the given latitude will be the place required.

Conversely. If a given place be brought (with the right or left hand according to its north or south position) to coincide with the brass meridian, the latitude will be found over the place; and the longitude, or inclination of the plane of its meridian to the east or west of that of London, will be cut by the brass meridian on the Equator.

Find the places answering to the following latitudes and longitudes :

Having a given Star, to find what other Stars lie in the same plane with that Star and the two poles of the Equinoctial, and consequently with the whole axis of our earth.

Repeat the following:

Equinoctial, (def. 14); Examine, by the Globe, the List of Constellations, (pages 55-58). Repeat again, Greek Alphabet, (p. 24.)

RULE.-Make the poles of the Equinoctial coincide with the wooden circle of the globe, and bring the given star to the graduated surface of the brass meridian; then all stars coinciding with the brass meridian will be the stars required.

Note. The stars coinciding with the under semi-circle of the brass meridian are also in the same plane; but may, in this instance, be left unnoticed.

1. What remarkable star in Ursa Minor; what stars in Cassiopeia, Pegasus, the Phoenix, and Hydrus, are nearly in the same plane with a of Andromeda and the Polar points; and, consequently, in the same plane with our whole axis ?

By bringing a of Andromeda, which I find to be in the head of that Constellation, to coincide with the graduated edge of the brass meridian, I see that the Pole Star, (which is not at the Pole), is then just 110 above it; and that ẞ in the chair of Cassiopeia, y (Algenib) in the wing of Pegasus, e in the wing of the Phoenix, and 8 in Hydrus, are likewise on the meridian.

2. What stars in Andromeda, Triangulum, Pisces, Cetus,* Eridanus, and Hydrus, are in the same meridional plane at any instant, with a in the Head of Aries?

3. What stars in Perseus, Sceptrum, Eridanus, and Dorados, are in the same plane with Aldebaran; and how is that plane numbered where it cuts the Equinoctial?

4. What stars in Auriga, Lepus, and Columba, are brought to any meridian at the same time with Betelgeux, (a of Orion): and how is their common plane numbered on the Equinoctial?

5. What small stars in the Lynx, Gemini, Monoceros, and Argo Navis culminate at the same instant, (or within two minutes of time, or a half degree), with a of Canis Major, (Sirius)?

6. What stars in Ursa Major, Leo Minor, Leo Major, and

* If the globe should not have the smaller stars marked with sufficient clearness, the exact part of the Constellation may be named.