244 
INDEX. 
Tuning-forks vibrating, 142 
Turin, moraines near, 130 
Twinkling of stars, 71 
Tympanum of the ear, 137 
Tyndall, Dr., cited, 75, 87, 91, 
128, 144 
UNDERCLAYS of coal, 176 
Undercliff, Isle of Wight, 103 
Undulatory theory of light, 33-35 
VIBRATION OP TUNING-FORKS, 142 
Violet, structure of the, 227 
WALES, rain in, 8 1 
Water, cutting power of, 105-112 
"hard," 95 
heat required to vaporize, 92 
how it rises in a plant, 157 
in U tube kept up by pressure, 
64 
solid matter dissolved in, 105 
Water-dust, 75 
Waterfalls, how formed, 108 
Water-flowers in ice, 91 
Water-pipes, cause of bursting of, 
9 
Water-vapour invisible, 75, 77 
screening the sun's heat, 82 
Waves, noise of the, 143, 144 
of light measured, 37 
of sound crossing each other, 
'35 
Wave-theory of light, 33-35 
Wax, plate of in hive, 198 
formation of, 199 
Weight and pressure of air, 58, 60 
barometer measuring, 64-66 
Wheel revolving to make musical 
note, 141 
Williams, Mr. J., cited, 176 
Wind, cause of, 67 
noise of the, 144-146 
fertilizing plants, 216 
Winds, land and sea, 69 
, trade-, 69 
Woodstock Park, echoes in, 134 
Work of the sunbeams, 42 
YOUNG, Dr., cited, 189 
