pic of Cancer,.that south, is the tropic of Capricorn, because the Sun is in the signs Cancer and Capricorn, when over these circles. The circle which bounds the north frigid zone, is called the Arctic circle; because the star Arcturus is in the northern hemisphere; and the opposite polar circle is called Antarctic, because opposite to the Arctic. While the Earth is passing through the signs of Libra, Scorpio, and Sagittarius, the Sun appears to pass through Aries, Taurus, and Gemini, and then seems advancing north, from the Equator. These in Astronomy are the spring signs. From the 20th of March, at which time the sun is seen at the beginning of Aries, till the 20th of June, when its place is at the beginning of Cancer, its rays are becoming more and more direct in all places north of 23° 28'. Consequently the rays of the Sun have increasing power. While the Sun appears to pass through Cancer, Leo, and Virgo, it seems receding to the autumnal equinox, the 23d of September. The last three signs are called summer signs. The Earth has accumulated so much heat before the summer solstice at the 20th of June, that the radi ation of that heat with the Sun's continued influence usually gives the warmest weather in July and August. After the autumnal equinox, the Sun appears to be passing through Libra, Scorpio, and Sagittarius, called autumnal signs; and continues receding from the northern hemisphere: consequently its What are those circles called which are between the torrid and temperate zones?-between the temperate and frigid zones? What signs are called spring signs ?—summer signs ?—autum2 signs? rays are becoming more oblique with us, and have diminished power. Till the 20th of December the heat of summer continues to be radiated from the Earth in such measure, that the coldest weather is most commonly the last of January. The signs Capricornus, Aquarius, and Pisces, in which the Sun appears between the winter solstice, the 20th of December, and the vernal equinox, the 20th of March, are called winter signs. Warmth from the Sun is in proportion to the density of the atmosphere, to the directness of the Sun's rays, and to the time of its continuance above the horizon. Reference to Plate iii. Figure 2, will aid in this illustration. Central parts of the torrid zone, have only two seasons; the dry or summer, during the intense heat of which, the soil often becomes parched; and the wet or winter, when incessant torrents of rain descend. Near the polar circles the transitions from winter to summer, and summer to winter, are so sudden, that they can scarcely be said to have intermediate seasons. It is only in the lower latitudes of the temperate zones, that months of spring paint the landscape and perfume the air; or the brown fulness of protracted autumn, allows the husbandman at his leisure to fill his store houses with plenty. The summer is longest in the northern hemisphere, because the orbit of the Earth is elliptical; and the Sun is in one of the foci of that ellipse. Between the vernal and the autumnal equinox, What are winter signs? When is it common to have the warmest weather? Why? When the coldest? Why? On what does heat depend? How many seasons in the torrid zone ?--in the frigid? Where are the four seasons most regular? In which hemisphere is the summer longest? Why? there is included more than half the Earth's orbit; and in that half it revolves with less velocity, than in the other half; consequently, almost 8 days more time is consumed. We are about 3 millions of miles nearer to the Sun in January, than in July. It has already been shown, what occasions the heat of summer; and Plate v. Figure 3, will further illustrate the subject, by giving definite views of what are direct, and what are oblique rays. Calculations of some accuracy may here be useful : From the vernal equinox to the summer solstice, there are, 48 H. M 92 31 14 From the summer solstice to the autum "According to the chronology of the Hebrew Bible, the Earth was created 4004 years before the birth of our Saviour. Astronomy shows that the great axis, or longest diameter of the elliptic orbit, in which our planet revolves round the Sun, as placed in one of the foci, coincided at that epoch, with the line of the equinoxes." Professor URE's Geology, published in London, 1829. The periods would then have been of equal length between the rernal equinox and the autumnal; and the autumnal equinox and the vernal. Why is it not probable, that Adam, at the time of the autumnal equinox, first opened his eyes on the ma tured fruits of the northern hemisphere, in which he was located. Perhaps, on the demiurgic week, as it is sometimes called, the seasons might have commenced all over the globe, as they would be succeeding years at the autumnal equinox. How much nearer are we to the Sun, in January than in July? What accurate calculations are given, respecting the periods aetween the equinoxes and solstices 7 |