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262 V Velocity, of Mercury in orbit, 63. of satellites about primary, Notes 245. of major planets, in orbit, Notes 245. Venus, 73-90. surface markings, 74, 77, 79, 80, 83, 220, 221. brilliancy due to cloudless atmosphere, 75. importance of rotation period, 75, 76. turns same face to the Sun, 77-80, 134, 220, 221. ice on the night side, causes ashen light, 82. Very, Professor, 16, 191, 192, 194. Vesta, 101. Vogel, 52. Volcanoes, avenues to earlier state, 160. Von Zach, 96.

W Walker, Mr., 123, 124. Water, becoming more scarce, 203, 204, 211. lacking on Moon, 204. Water-vapor, in atmosphere of Jupiter, 53. in atmosphere of Mars, 91, 161. smaller planet has less hold on, 207. Williams, Mr. Stanley, 103. Witt, de, 94. Wolf, Dr., 13. Wolf, Max, 94. Wolf-Rayet stars, 13, 48. Wright, 13, 43.

Y Year, of Uranus, 116. Yerkes Observatory, 232. Young, 46.