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BELL SYSTEM TECHNICAL JOURNAL 



When the Crystal Clock was first described as such in April 1930, the idea 

 was discussed quite widely in Europe and America, and it was not long 

 before the work was duplicated and extended in other places. The first 

 outstanding application of the quartz clock to astronomy was made in 



Fig 31 — Display clock at 195 Broadway, New York. This clock, controlled by the 

 Bell System Frequency Standard, shows the same time as that of the New York Telephone 

 Time Service. 



Germany with the installation at the Physikalisch-Technische Reichsanstalt 

 This was described by Scheibe and Adelsberger in 1932^°^ and 1934^°^, and 

 reports of its splendid performance continued periodically. It was with 

 this installation that it was possible for the first time to observe and measure 

 variations in the earth's rate occurring over intervals as short as a few weeks. 

 Previous measurements of such variations, involving studies of motion of the 

 moon, the planets, and Jupiter's satellites, had required years to obtain 



