Part 104

Pendulum, 98.

Perihelion, 75.

Perpendicular lines, 25.

Phases, 109.

Piston, 143, 145.

Plane, 92, 93.

Planets, 76, 81, 83.

Poles, 92, 99, 100.

Polar star, 100, 112.

Porosity, 42, 126.

Powers, mechanical, 54.

Projection, 49, 50, 71.

Precession of equinoxes, 107.

Pulley, 54, 63.

Pump, 31. sucking and lifting, 143. forcing, 144, 145. air, 31, 145.

Pupil of the eye, 164.

Rain, 17, 129.

Rainbow, 188.

Rarity, 16.

Ray of light, 158, 179. reflected, 160, 161. incident, 161.

Rays, intersecting, 165.

Reaction, 39.

Receiver, 31.

Reflection of light, 160, 163. angle of, 45, 161, 173. of mirrors, 173. of plane mirrors, 174. of concave do. 174. of convex do. 174.

Reflected motion, 43.

Refraction, 179, 186. of the atmosphere, 182. of glass, 183. of a lens, 184. of a prism, 185.

Resistance, 54.

Retina, 165. image on, 166.