Water, why does it roll in agitated globules when dropped upon hot iron, 796 Water, why does oil float upon it, 797 Water, why is spring fresh and invigorating, 803 Water, why is boiled flat and insipid, 804 Weather, why does a yellow sunset foretell wet, 534 Weather, why does a red sunset foretell fine, 535 Weather, why does a red sunrise foretell wet, 536 Weather, why does a grey sunrise foretell dry, 537 Weather, barometrical indications of, 708 Whales, why have they a large development of oily matter about their heads, 1068 Whale, why has it feathery bones extending from its jaws, 1095 Whales, why are, their eyes provided with very thick coats, 1131 Wheat, why do the ears stand up by day and turn down by night, 1175 Wheat, what is it, 1199 LESSON LXXVII. Wheat, what is the northern limit of, 1235 Wheat, why is silica diffused over its stem, 1261 Wheat-crops, why do they greatly exhaust the soil, 1263 Whirlwinds, what are they, 678 Why do we see, 963 Why do we wink, 975 Why do we weep, 977 Why do we hear, 983 Why do we taste, 986 Why do we smell, 992 Why do we feel, 1004 Why do we sleep, 1019 Why do we dream, 1020 Why do suppers produce dreaming, 1021 Why do we yawn, 1022 Why do we cough, 1023 Why do we sneeze, 1024 Why do we sigh, 1025 Why do we laugh, 1026 Why do we hiccough, 1027 Why do we snore, 1028 Why do we feel hungry, 1337 Why do we feel thirsty, 1338 Wick of a candle, why does it turn black as it burns, 225 Wick of a candle, why is there a spark generally at the end of it, 256 Will-o'-the-wisp, what is it, 318 Winds, what is the cause of, 234 Winds, why are east usually dry, 384 Winds, why are west usually wet, 385 Winds, why are north usually cold and dry, 386 LESSON LXXVIII. Winds, why are south warm and rainy, 387 Wind, what is it, 666 Winds, what are the velocities of, 667 Winds, what are trade, 668 Winds, what is the cause of trade, 669 Winds, why do trade winds blow from east to west, 670 Winds, what determines the character of, 674 Wind-mills, why do their wings turn round, 690 Windows, why do they reflect the sun's rays in the evening, 523 Windows, why do they not reflect the sun's rays at noon, 524 Wood, why does decayed look luminous, 95 Wood, burning at one end, why does it not feel hot at the other, 118 Wood, why is it a bad conductor of heat, 119 Wood that is green, why does it hiss and steam when burning, 285 Wood, why does it ignite less readily than paper, 297 Woodcocks and snipes, why have they nerves running down to the tip of their bills, 1043 Woodpeckers, why do they "tap" at old trees, 1066 Woollens, why are they worn in winter, 166 Wool, what is it, 1201 Yawn, why do we, 1026 Zoological geography, 1326