Hearth-rug, and hearth-stone, their relative states of heat, 142 Heat, which are the better conductors, fluids or solids, 146 Heat, why are dense substances the best conductors, 147 Heat, why are fluids bad conductors, 148 Heat, why are woollen fabrics bad conductors, 149 Heat, is air a good or bad conductor, 150 LESSON XXXVII. Heat, is water a good or a bad conductor, 151 Heat, how do we know that air is not a good conductor, 155 Heat, how do we know that water is not a good conductor, 156 Heat, why are bottles of hot water wrapped in flannel, 158 Heat, why are hot rolls wrapped in flannel, 159 Heat, what is the highest degree that man can bear, 176 Heat, why may man endure a high degree without injury, 178 Heat, why may we believe that the internal heat of the earth does not arise from terrestrious combustion, 224 Heat, what is the radiation of, 181 Heat, what becomes of that which is radiated, 186 Heat, when does a body radiate it, 184 Heat, does the movement of the air affect the radiation of, 188 Heat, why will not the motion of air disturb the rays of, 190 Heat, what bodies are good radiators of, 192 Heat, what bodies are bad radiators of, 193 Heat, why does water keep hot longer in a bright metal jug, 195 LESSON XXXVIII. Heat, may it be reflected, 210 Heat, are light or dark-coloured bodies the best reflectors, 211 Heat what bodies are the best reflectors of, 212 Heat, why is that which is reflected less intense than the primary, 214 Heat, can it be reflected in any great intensity, 215 Heat, are good reflectors also good absorbers, 216 Heat of the sun's rays, how is it diffused, 219 Heat, how do we know that it is absorbed by the earth, 222 Heat, do plants absorb it, 225 Heat, how is it diffused through the atmosphere, 232 Heat, how is it diffused through the ocean, 233 Heat, why is it developed during chemical changes, 312 Heat, what are the sources of, 323 Heat, what is the accepted theory of, 328 Heat, what is the point at which it becomes luminous, 545 Heat, what is the relative intensity of primary and reflected, 548 Heat to cold, why does a sudden change bring on illness, 1013 LESSON XXXIX. Heat of the earth, Humboldt's opinion upon the internal, 1335 Heat of the earth, Hunt's opinion upon the internal, 1336 Hear, why do we, 983 Hiccough, why do we, 1027 Hoar-frost, what is it, 362 Hoar-frost, why does it foretell rain, 363 Hoar-frosts, why are they so frequent, and black-frost so unfrequent, 412 Hogs, why have Indian large tusks turning back towards their eyes, 1068 Hog, why is the under-jaw of the, shorter than the upper-jaw, 1039 Hoop, why does it roll without falling to the ground, 861 Hoop, why does it when falling make several side revolutions, 862 Horses, why have they smaller stomachs proportionately than other animals, 1097