2-798-504 - The Print Collector/Heritage Images

The Time Ball, Royal Observatory, Greenwich, Fig. 3, 1846. 'The hour of one o'clock is announced by the descent of a large black ball, from the summit of a pole, which surmounts the northwestern turret of the Observatory; a position singularly favourable for its exhibition to mariners on their progress down the adjacent river Thames. The apparatus...may be said to consist of a hoist for raising the ball, a trigger and discharging gear for its liberation, and a clock, regulated by observation, for giving the required moment of time...Fig. 3. Apparatus in the Turret-house, a, the triangular supporting shaft; b, the pulley over which passes the chain for raising the ball'. From "Illustrated London News", 1844, Vol V.