252 
INDEX. 
Water-vapour invisible, 78, 80. 
screening the sun's heat, 85. 
Waves, noise of the, 147, 148. 
of light measured, 37. 
of sound crossing each other, 
139- 
Wave-theory of light, 33-35. 
Wax, plate of, in hive, 206. 
formation of, 206. 
Weight and pressure of air, 62, 
64. 
barometer measuring, 67-70. 
Wheel revolving to make musical 
note, 145. 
Williams, Mr. J., cited, 178. 
Wind, cause of, 71. 
noise of the, 149^151. 
fertilizing plants, 223. 
Winds, land and sea, 72. 
trade-, 73. 
Woodstock Park, echoes in, 139. 
Work of the sunbeams, 42. 
YOUNG, Dr., cited, 192. 
THE END. 
