[Fig. 2] is a diagram showing the principle of a solar eclipse. The dark or central part of the moon’s shadow, where the sun’s rays are wholly intercepted, is here the umbra, and the light part, where only a part of them are intercepted, is the penumbra; and it is evident that if a spectator be situated on that part of the earth where the umbra falls there will be a total eclipse of the sun at that place; in the penumbra there will be a partial eclipse, and beyond the penumbra there will be no eclipse.
As the earth is not always at the same distance from the moon, and as the moon is a comparatively small body, if an eclipse should happen when the earth is so far from the moon that the moon’s shadow falls short of the earth, a spectator situated on the earth in a direct line between the centers of the sun and moon would see a ring of light around the dark body of the moon; such an eclipse is called annular, as shown in [Fig. 3]; when this happens there can be no total eclipse anywhere, because the moon’s umbra does not reach the earth.
An eclipse can never be annular longer than twelve minutes twenty-four seconds, nor total longer than seven minutes fifty-eight seconds; nor can the entire duration of an eclipse of the sun ever exceed two hours.
An eclipse of the sun begins on the western side of his disc and ends on the eastern; and an eclipse of the moon begins on the eastern side of her disc and ends on the western.
The average number of eclipses in a year is four, two of the sun and two of the moon; and as the sun and moon are as long below the horizon of any particular place as they are above it, the average number of visible eclipses in a year is two, one of the sun and one of the moon.
What are Dreams?
The dictionary tells us that a dream is a train of vagrant ideas which present themselves to the mind while we are asleep.
We know that the principal feature, when we are dreaming, is the absence of our control over the current of thought, so that the principal of suggestion has an unlimited sway. There is usually a complete want of coherency in the images that appear in dreams, but when we are dreaming this does not seem to cause any surprise.
Occasionally, however, intellectual efforts are made during sleep which would be difficult to surpass when awake.
It is said that Condillac often brought to a conclusion in his dreams, reasonings on which he had been employed during the day; and that Franklin believed that he had been often instructed in his dreams concerning the issue of events which at that time occupied his mind. Coleridge composed from two to three hundred lines during a dream; the beautiful fragment of “Kubla Khan,” which was all he had committed to paper when he awoke, remaining as a specimen of that dream poem.