Entered according to Act of Congress, in the year 1834, In the Clerk's Office of the District Court of Massachusetts. SCIENTIFIC TRACTS AND FAMILY LYCEUM. JANUARY 1, 1834. [Furnished for the Scientific Tracts and Family Lyceum.] ASTRONOMY. THE MOON. AFTER the sun, the moon is the most prominent and interesting object visible in the heavens. The theory of the moon's motions, as well as its place in the heavens at particular times, is of great importance in navigation; for by means of these, seamen ascertain the longitude of their vessels, and thus find how far east or west they are of their port of destination. The great improvements which have been made in Nautical Astronomy in modern times, have been mainly produced by the assiduous exertions of learned men to discover the true theory of the moon's motions; added to this, if we consider the vast influence which the old notions respecting the heavenly bodies, particularly that of the moon, have had upon the happiness of mankind, we cannot but acknowledge the importance of correct notions in relation to this subject among the great mass of the people. If to all this, we add the vast influence exercised by old prejudices and superstitions in relation to the influence of the moon on the local affairs of our planet and its inhabitants, even at the present time, we cannot but think some good may be done by devoting a few tracts to an explanation of some of the most obvious and important facts in relation to this subject. We propose to explain in a brief and practical manner, the cause of some of the most obvious appearances of the moon, together with the general laws which govern her motions. We shall be careful that our facts, when assumed, are drawn from authentic sources, and that our reasoning is such as may be understood and followed by common people. APPEARANCE AND CONSTITUTION OF THE MOON. When the moon is viewed with the naked eye, several dark spots are observed, which are occasioned by the moon's surface being broken into irregular portions. When we look at the surface of the moon with a good telescope, we find its surface wonderfully broken and diversified. Besides the dark spots which are visible to the naked eye, extensive valleys and long ridges of mountains are readily distinguished, projecting their shadows on the plains below. Single mountains are here and there seen, which rise to a considerable height. We may know that we truly behold mountains and valleys in the moon, by the simple consideration, that we behold and may trace the outlines of the shadows cast by the hills and mountains; and these are found to be in exact proportion to the lengths which they should have, knowing the inclination with which the sun's rays strike that part of the moon's surface. From the most accurate measurements of the heights of the lunar mountains, none of them are found to exceed two miles. There are also observed upon the moon's surface deep and accurately defined cavities or valleys. The mountains and hollows are all of one similar shape, being nearly all circular; the hollows having flat bottoms, and in most cases a small steep conical hill or mountain is seen directly in the middle of these valleys; thus presenting an exact resemblance of volcanoes, such as are found upon our planet; in point of fact, Dr. Herschel in 1787, saw three volcanoes in different parts of the new moon, two of them in an active state of eruption, sending forth flames. The next night after he first saw them, he observed them again still in flames. When the moon is full, or in opposition, the elevations and depressions on her surface nearly disappear, because then the sun shines directly upon her surface, and, of |