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ticular place is brought under the strong brass meridian, it will shew the precise time of sun-rising and sun-setting at that place, according as that place is brought to the eastern or western edge of the broad.: paper circle.

It will also shew how long any place is in moving from the east to the west side of the illuminated disc, and thence the length of day and night.

It will also point out the length of the twilight, by shewing the time in which the place is passing from the twilight circle to the edge of the broad paper circle on the western side; or, from the edge of this circle on the eastern side, to the twilight wire, and thus determine the length of the whole artificial day.

N. B. The twilight wire is placed at 18 degrees from the broad paper circle.

I shall now proceed to exemplify, upon the globes, these particulars, at three different seasons of the year, viz. the summer solstice, the winter solstice, and the time or times of the equinoxes.

PROBLEM XIII. To place the globe in the same situation, with respect to the sun, as our earth is in at the time of the summer solstice.

Rectify the globe to the extremity of the divisions for the month of June, or 23 degrees north declination; that is, bring these, divisions on the strong. brass meridian, to coincide with the plane of the broad paper circle.

Then, that part of the earth's surface, which is within the northern polar circle, will be above the broad paper circle, and will be in the light, and the inhabitants thereof will have no night.

But all that space, which is contained within the southern polar circle, will continue in the shade; that is, it will there be continual night.

In this position of the globe, the pupil will observe how much the diurnal arches of the parallels of latitude decrease, as they are more and more distant from the elevated pole.

If any place be brought under the strong brass meridian, and the horary index is set to that XII which is most elevated, and the place be afterwards brought to the western side of the broad paper circle, the hour index will shew the time of sun rising; and when the place is moved to the eastern edge, the index points to the time of sun-setting.

The length of the day is obtained by the time shewn by the horary index, while the place on the globe moves from the west to the east side of the broad paper circle.

Thus, it will be found, that at London the sun rises about 15 minutes before IV in the morning, and sets about 15 minutes after VIII at night.

At the following places, it will be nearly at the times expressed, in the table.

We also see, that at the same time the sun is rising at London, it is rising at the isles of Sicilly and Madagascar.

And, that at the same time when the sun sets at London, it is setting at the island of Madeira, and Cape Horn.

And, when the sun is setting at the island of Borneo, in the East Indies, it is rising at Florida, in America. And many other similar circumstances, relative to other places, are seen, as it were, by inspection.

PROBLEM XIV. To explain the situation of the earth, with respect to the sun, at the time of the winter solstice.

Rectify the globe to the extremity of the divisions for the month of December, or to 231 degrees south declination.

When it will be apparent that the whole space within the southern polar circle is in the sun's light, and enjoys continual day; whilst that of the northern polar circle is in the shade, and has continual

If the globe be turned round, as before, the horary index will shew that, at the several places before-mentioned, their days will be respectively equal to what their nights were at the time of the summer solstice.

It will appear, farther, that it is now sun-setting at the same time in those places in which it was sun-rising at the same time at the summer solstice; and, on the contrary, sun-rising at the time it then appeared to set.

PROBLEM XV. To place the globe in the situation of the earth, at the times of the equinox.

The sun has no declination at the times of the equinox; consequently, there must be no elevation of the pole.

Bring the day of the month when the sun enters the first point of Aries, or day of the month when the sun enters the first point of Libra, to the plane of the broad paper circle; then the two poles of the globe will be in that plane also, and the globe will be in that position, which is called a right sphere:

For it is a right sphere when the two poles are in the plane of the broad paper circle, because then all those circles, which are parallel to the equator, will be at right angles to that plane.

If the globe be now turned from west to east, it will plainly appear, that all places upon its surface. are twelve hours above the broad paper circle, and twelve hours below it; that is, the days are twelve

hours long all over the earth, and the nights are equal to the days; whence, these times are called the times of equinox.

Two of these occur in every year; the first is the autumnal, the second the vernal equinox.

At these seasons, the sun appears to rise at the same time, to all places that are on the same meridian. The sun sets, also, at the same time in all those places.

Thus, if London, and Mundford, on the Gold Coast, be brought to the strong brass meridian, the graduated side of which is, in this case, the horary index, and they be afterwards carried to the western edge of the broad paper circle, the index will shew that the sun rises at VI at both places; when they are carried to the eastern edge, the index points to VI for the time of sun-setting.

N.B. If London be not the given place, the hour index is to be set to the most elevated XII, while the place is under the graduated edge of the strong brass meridian.

The following circumstances, which usually attend the four cardinal divisions of the year, cannot be better introduced than at this place. At the time of the equinoxes, when the sun passes from one hemisphere into the other, there is almost constantly some disturbance in the weather; the winds are then generally higher: at the vernal equinox, they are, for the most part, easterly, cold, dry, and searching; The solstitial point of the summer is often distinguished by violent rains, and what we call a mid