The sale of 3000 copies Of this book in little more than a year, many of them to persons Of more educa~ tion than I originally contemplated, has induced me to enlarge it considerably, going rather deeper into the subject, and adding some explanations which I did not venture on before. The additions chie?y relate to meteors, nebulae, and stars, the moon's acceleration and other disturbances, the tides, and the calculations for Easter in all ages; and a fuller account Of the meth ods of weighing the sun, moon, and planets. The chap ter on telescopes also has been greatly enlarged; for astronomy lives by them, and I do not know where a popular explanation Of the theory Of telescopes is to be found.