318 



INDEX. 



Ice, fractures in regular Hues and aagles, Light, chief sources of, 241 



186 

 heat of, 180 

 what is, 179 



why floats upon water, 62 

 why melted by the sun, 196 

 Icebergs, height of, 106 



how formed, 106 

 Illusions, optical, 269 

 Images all appear inverted in water, 246 

 Impenetrability, 4 

 Incandescence, what is, 181 

 Incidence, line and angle of, 246 

 Induction in magnetism, 296 

 Inertia, illustrations of, 10 

 Inertia, what is, 9 



Insects, how occasion sounds, 123, 124 

 Instrument, stringed, use of the body ot, 



117 



Ionic order of architecture, 45 

 Iris of the eye, 263. 

 Iron, how made hot by striking, 139 

 meteoric, 96 

 where found, 96 

 why sinks in water, 62 

 why stronger than wood, 12 



Kettle, why heat is not applied at the top 

 of, 154 



why sometimes boils over, 156 

 Kyanizing, what is, 311 



Lakes, some never frozen, 183 



Lamps, closed, use of a hole in the top, 



233 



gas generated by, 208 

 smokes, occasion of, 223 

 solar and astral, how constructed, 



223 

 wicks, eottoa best adapted for, 



Land, configuration of, effect on tempe- 

 rature, 107 



Latent heat, what is, 189 

 Larynx, 122 

 Laundress, why boils starch, 802 



how propagated, 244 



intense, why causes pain to th 



eye, 266 



most splendid artificial, how pro- 

 duced, 293 



moves in straight lines, 244 

 of the sun, how much intercepted 



by the atmosphere, 261 

 possesses no weight, 241 

 ray of, when reflected, 244, 245 

 refraction of, 2-54 



the same quantity not reflected at 

 all angles, illustrations of thi 

 principle, 248 



velocity of, how estimated; illus- 

 trations of, 242, 243 

 what is, 241 



white, composition of, 255 

 why, when it is cloudy, 252 

 zodiacal, 97 

 Lightning clouds, height above the earth, 



280 

 conductors, best materials for, 



284 



different kinds of, 280 

 direction of a flash of, 281 

 does not follow a direct path, 



284 



heat, cause of, 281 

 how kills persons, 281 

 rod, what is a, 284 

 rods, how fastened to buildings, 



285 



how protect houses, 2S4 

 when productive of harnv, 



284 

 why terminate in points, 



284 



sheet, 280 

 what is, 280 

 why most common in summer, 



281 



Lights, Northern, 287, 288 

 Lime, chloride of, 307 

 quick, 38 



absorbs carhpnic acid, 212 

 slacked, 38 

 water poured on occasions heat, 



how, 137 

 Linen handkerchief, why preferred to A 



cotton one, 149 



Linen, how dried by exposure to the air, 

 198 



why touches 

 saliva, 195 

 Laughing, what is, 123 

 Lead, a poison, 310 



why called heavy, 6 

 Leather, how made, 805 



Leaves, of plants, how radiate heat, 165 

 of plants, why green, 271 

 why brown in autumn, 271 

 Lens, double convex, 260 



what is a, 260 



Lenses, different varieties of, 260 

 Liht, absorption of, 261 



trtmcialt vn what depends, 231 



flat-iron with! why cooler thnn cotton, 149 



Liquefaction, 192 

 Liquid, what is a, 8 

 Liquids, how to cool, 155 



impart no additional heat after 

 they boil, 157 



Liquors, frothing, cause of, 74 

 Loadstone, what is a, 295 



why so called, 295 



Loudness, of sound, on what depend?., US 

 Lunar caustic, 304 

 Lungs, description of, 234 



