Old Farmers’ Almanac, 184. Old Moon in the new Moon’s arms, 93. Opera glasses, 140. Optic nerve, 126. Orion, of the Arabians, 22. belt of stars of, 21. constellation of, 20. finding the North with, 23. the Great Hunter, 20. Great Nebula of, 119. sword of stars of, 22. Pacific time, 160. Parabola, 113. Partial eclipse of the Sun, 112. Pegasus, the Flying Horse, 19. Pendulum illustrating Sun’s attraction, 59. Penumbra, 135. Perpendicular line defined, 194. Phases, of Mercury, 48. of Venus, 50. Photograph, how made, 185. Photographing the Moon, 188 the stars, 185. Photographing the Sun, 187. Photosphere of the Sun, 32. Pinhole sunshade, 30. Pinhole telescope, 30, 138. Pisces, the Fishes, constellation of, 63, 174. Plane, defined, 55. Planet, how to plot position of a, 61. Planetesimal hypothesis, 119, 120. Planets, eggshell experiment to show motions of, 57. first aid to remembering, 57. how held in space, 57. how to know the, 47. names and sizes of, 47. path of, 170. plane of, 55. round the Sun, position of, 54. the Sun’s kiddies, 46. through a telescope, 148. use of almanac for finding, 61. why they spin, 60. Pleiades, in Taurus, 26. through a glass, 150. Plotting the position of a planet, 61. Plough, the, 5. Pointer stars of the Big Dipper, 10. Polar nights, 71. Polaris, the Pole Star, 4. Pole Star, the, 4, 8. Precession of the Earth, 173. Prime meridian, 156. Prism, 132. forming a spectrum, 134. how to use, 188. Produce, defined, 8. Prominences of the Sun, 31. Protractor, showing degrees, 81. showing degrees latitude, 82. Radius defined, 194. Railroad time, 156. Reflection of light, 131. Regulus in Leo, the Lion, 177. Rigel in Orion, 28. Right angle defined, 194. Ring defined, 194.