j8& of the length of days and nights,

ons of the earth in her annual motion roundthe fun. Then, since it is known from obser-vation, that the axis of the earth is always di-rected to nearly the fame fixed point in theheavens, it will constantly preserve the sameposition, and be always in a situation nearlyparallel to itself, in whatever part of her orbitthe earth may be in the course of her journeyround the sun.

Suppose now, the earth to be in the situationwhich is represented by the month March;then, because a right line joining the centers ofthe fun and earth, will cut the surface of theearth in the equator, the terminator will passthrough the two poles, and the days and nightswill consequently be equal all over the globe.But when the earth, by its annual motion, iscarried farther in its orbit towards A, the northpole N, of the axis, still continuing to observethe same parallel situation, will advance into theenlightened hemisphere, and, in the month ofJune, will be about twenty-three degrees anda half distant from the terminator, the southpole being at the same distance in the dark he-misphere. In the month of June, therefore,the northern parts of the earth will enjoy longdays and summer, whilst the southern parts willhave short days and winter.

During the interval between the time of equaldays and nights in March, which is called the

Vernal

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