hands of a tower clock. The min- ute-hand shaft is not used, and this clock steadily is enveloped in the comparative gloom of the hall. series of divisions is marked off, each corresponding Thus the recurrence of day and night is made plain turns only the shaft usually employed to drive the to a… … THE GREAT PLANETARIUM OF THE AMERICAN MUSEUM OF NATURAL HISTORY. once in 24 hours, a pair of gear wheels is interposed into twenty-four spaces with fractional divisions for The top .of the handrail is divided into 360 spaces so that the hour-hand shaft moves as it would for a half and quarter…
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