orbital velocity of,251periodic time of,251Vibration, atomic,75Vibrations, transverse,130longitudinal,130of sound,123Vibratory motion,91Vogel, Prof.,308,312Vogt, Prof.,332Volume of sun,27Von Asten,234,296Vortex theory,92,337motion,221-4atom,93,126,337rings,125,337Vortices, molecular,103Water waves,124currents, power of,95composition of,141power,88Wave front,128motion,124,160Wave lengths,120envelope,112Waves, chemical,141sound,104,120,124light,126heat,141electric,159spherical,112electro-magnetic,165Weight,29,69,84variation of,29pound,30Whewell,3,221Winds,81,90energy of,90trade,225Work,96and energy,84from heat,116Young, Thomas,54,64,67,123on aether,58fourth hypothesis,70Prof., of America, on electric space,166Zinc,88Zodiacal light,277-9