73. (Pg. 106) How is this accounted for? 74. (Pg. 106) What is meant by the solar and the sidereal day? 75. (Pg. 106) What is the difference in time between them? 76. (Pg. 106) What is the length of the tropical year? 77. (Pg. 107) The solar year is completed before the earth has made a complete revolution in its orbit, by what is this caused? 78. (Pg. 107) What is this called, and what is represented respecting it by fig. 1, plate 11? 79. (Pg. 107) By what means can we ascertain the period of a complete revolution of the earth in its orbit, as illustrated by the fixed star E, in fig. 1? 80. (Pg. 107) What difference is there in the length of the solar and sidereal year? 81. (Pg. 107) Why can we not always ascertain the true time by the apparent place of the sun? 82. (Pg. 108) What would be the greatest difference between solar, and true time, as indicated by a perfect clock? CONVERSATION IX. ON THE MOON. OF THE MOON'S MOTION. PHASES OF THE MOON. ECLIPSES OF THE MOON. ECLIPSES OF JUPITER'S MOONS. OF LATITUDE AND LONGITUDE. OF THE TRANSITS OF THE INFERIOR PLANETS. OF THE TIDES. MRS. B. We shall, to-day, confine our attention to the moon, which offers many interesting phenomena. The moon revolves round the earth in the space of about twenty-nine days and a half; in an orbit, the plane of which is inclined upwards of five degrees to that of the earth; she accompanies us in our revolution round the sun. _Emily._ Her motion then must be of a complicated nature; for as the earth is not stationary, but advances in her orbit, whilst the moon goes round her, the moon, in passing round the sun, must proceed in a sort of scolloped circle. _Mrs. B._ That is true; and there are also other circumstances which interfere with the simplicity, and regularity of the moon's motion, but which are too intricate for you to understand at present. The moon always presents the same face to us, by which it is evident that she turns but once upon her axis, while she performs a revolution round the earth; so that the inhabitants of the moon have but one day, and one night, in the course of a lunar month. _Caroline._ We afford them, however, the advantage of a magnificent moon to enlighten their long nights. _Mrs. B._ That advantage is put partial; for since we always see the same hemisphere of the moon, the inhabitants of that hemisphere alone, can perceive us. _Caroline._ One half of the moon then enjoys our light, while the other half has constantly nights of darkness. If there are any astronomers in those regions, they would doubtless be tempted to visit the other hemisphere, in order to behold so grand a luminary as we must appear to them. But, pray, do they see the earth under all the changes, which the moon exhibits to us?