Master Timekeepers Watch Clock for Nation (Dec, 1938)

Master Timekeepers Watch Clock for Nation

Above, granddaddy of all clocks in U. S. shows time in this country and corresponding time in other parts of world

Top, tuning radio at naval observatory to receive time signal from naval radio station at Arlington.

Center, reading tape from chronograph which checks synchronization of clocks in thousands of a second

Left, astronomer at naval observatory operating “Zenith tune,” which checks master clocks. It photographs stars crossing the zenith. Chronograph records time of stars’ crossing.

Above, master clock at observatory at exact noon, eastern standard time, but its face shows seventeen o’clock, which is Greenwich time. P. H. Tobleman points to mechanism that flashes long dash over radio to give correct time

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