Blagden proceeds to explain these meteors on the bypothesis, that they are electrical phenomena. His arguments are, 1st, from the great rapidity of their motion, which seems to exceed any other we are acquainted with, besides electricity; 2dly, from certain electrical phenomena, which sometimes accompany these meteors; and, 3dly, from the connection which they have with the aurora borealis. Dr. Blagden concludes, that there are three regions of the atmosphere, distinguished by electrical phenomena peculiar to each; 1st, the lowest region, in which the thunder and lightning occur; 2dly, the middle region, where the fireballs and shooting stars are observed; and, 3dly, the highest region, where the aurora borealis displays a peculiar kind of electrical agency." It is worthy of remark, that many accounts mention flashes of lightning during the late display of meteors. It is very probable, that the great meteor which passed over England, on the 18th of August, 1783, was an electrical phenomenon. It went with immense rapidity, more than 1000 miles in about half a minute.

Is it a fact, that stones have fallen from the visible heavens to the Earth? How was the event of their falling first received? Where do we find the earliest account of these falling stones? Have there been many accounts of these stones handed down to us from antiquity? Can you name some instances of these stones falling in modern times? Has New England afforded any wellauthenticated account of these wonderful phenomena? Can you give some account of the meteor which appeared in Connecticut in 1807, and of the stones which fell on that occasion? What are some of the opinions respecting the origin of falling stones? What appears to be the most plausible opinion? Are there Juminous meteors different in their origin from aerolithes or falling stones? Can you give an account of the meteors witnessed by Humboldt and Bonpland at Cumana in South America? What other remarkable displays of luminous meteors can you mention? What noted exhibition of meteors will the citizens of these United States long remember? What is worthy of notice and philosophical inquiry in the several instances of these meteors in modern times? How have different authors accounted for these meteors? What seems to be the most probable conjecture respect. ing them? What is Dr. Blagden's hypothesis?

CHAPTER XVII.

Artificial Globes.

ARTIFICIAL globes are spheres intended to represent the Earth and the visible heavens. They are of two kinds, terrestrial and celestial. On the terrestrial is

represented the Earth's surface, diversified with the principal divisions of land and water, forming a spherical map of the whole; on the celestial, the visible heavens distinguished into constellations. For convenient use, a globe of either kind is placed upon a frame. On each, the great imaginary circles of the sphere, the tropics, and the polar circles, are represented.

The equator on a terrestrial globe is about one eighth of an inch broad, graduated for longitude 180° each way from the first meridian.

The ecliptic, about the same breadth, inclined to the equator in an angle of 23° 28', is divided into signs, and subdivided into degrees, commencing at the first of Aries.

The brazen meridian is a circle of brass encompassing the globe from north to south, crossing the equator at right angles. The upper semicircle of this is graduated, beginning at the equator, and ending with 90° at the poles. The graduation of the lower semicircle begins at the poles, and ends with 90° at the equator. Besides this, there are other meridians drawn on the globe with dark lines, meeting at the poles. 12 of these, 24 semicircles, form the hour lines. The meridian passing through the equinoctial points is the equinoctial colure. Another, passing through the solstitial points, is the solstitial colure. The horizon is represented by a broad circle of wood, divided into four points, east, west, north, south, called the cardinal points. Next to the globe, on this, are the amplitudes,

graduated into four nineties, commencing at the east and west points. Without these are the azimuths, graduated into four nineties, beginning at the poles. Next to these are the 32 points of the compass, containing 11° 15' each. Beyond these are the 12 signs, each having its appropriate name, figure, and character; and each graduated as in the ecliptic.

On the exterior circle of the horizon are represented the days of the months, adjusted to the signs, so that each day of a month is placed at the degree of the sign in which the Sun is at that time. Small figures between the divisions of days show how much the Sun is fast or slow of clock, marked (+) when the Sun is slow of clock, and (-) when it is fast.

The two tropics are represented on a terrestrial globe by dark or colored lines, 23° 28' from the equator; the two polar circles in the same manner 23° 28' from the poles.

Parallels of latitude, drawn to each 10°, are peculiar to this globe.

An hour circle, about two inches diameter at the north pole, is divided into 24 parts, and numbered into two twelves, with a movable index attached to the brazen meridian pointing to the time. A similar circle at the south pole is divided and numbered in the same manner, but without an index,-time being computed from the brazen meridian.

Some diversity is to be found in globes. The description here given answers to Gardener's globe.

Attached to some globes is a quadrant of altitude, a thin strip of brass, graduated into 90 parts, equal to 90° of a great circle.

The circles of an artificial globe are best learned by inspection with the globe at hand.

To use a globe, stand facing the graduated side of the brazen meridian.

To rectify a globe for the latitude of a place, elevate the nearest pole equal to the latitude of that place. When thus rectified, such place, brought to the brazen meridian, is at the top or highest point of the globe.

Suppose you would rectify for the latitude of Washington; raise the north pole till 38° 53′ on the lower semicircle of the brazen meridian comes to the upper side of the wooden horizon; then Washington, brought to the meridian, will be at the highest point of the globe.

The celestial globe has a representation of the zodiac. It has, also, besides the circles common to this and the terrestrial globe, secondaries, drawn perpendicular to the ecliptic at every ten degrees, meeting at the poles. The great circles are here graduated, as on the terrestrial globe. Except on the equator, the degrees are numbered in the same manner. This, beginning at the first of Aries, is numbered for right ascension eastward round the globe.

In the solution of problems on artificial globes, great accuracy is not to be expected. Important general knowledge, however, may be obtained.

Problems to be solved on the Terrestrial Globe.

PROBLEM I.

To find the latitude and longitude of a place. Bring the place to the brazen meridian. On the meridian above it is the latitude. The longitude is found on the equator at its intersection with the meridian. What are the latitude and longitude of Jerusalem ? Answer, about 32° N. 35° E.* Find the latitude and longitude of Canton in China. 230 N. 113° E.

PROBLEM II.

When the latitude and longitude of a place are given, to find the place.

Find the longitude on the equator. Bring this to the

*Longitude, in these problems, is reckoned from Greenwich, it being so placed on the globes.

brazen meridian. Directly under the latitude given is the place sought.

What place is in 42° 23′ N. 71° 4′ W.

What place is in 34° 26' S. 18° 23′ E.

PROBLEM III.

Boston.

Cape of Good Hope.

To find the difference of latitude between two places. Bring each to the brazen meridian, and find the latitude. If both be of the same name, north or south, the less subtracted from the greater leaves the difference of latitude. If the latitudes be of different names, one north and the other south, their sum is the distance sought.

Give the difference of latitude between Washington and New York. 1° 49'.

What is the difference of latitude between Philadelphia and Buenos Ayres? 74° 34'.

PROBLEM IV.

To find the difference of longitude between two places.

Find the longitude of each, according to the direction before given. If the longitudes be of the same name, east or west, their difference is the answer. When they are of different names, their sum, if less than 1800, is the result sought. If the sum be more than 180°, subtract it from 360°; the remainder is the difference of longitude required.

Give the difference of longitude between Portsmouth, N. H., and Cadiz ? 64° 30'.

What is the difference of longitude between St. Lewis and Paris? 920.

Find the difference of longitude between Cincinnati and Batavia.

168°.