EVOLUTION OF QUARTZ CRYSTAL CLOCK 583 



vanishingly small. In any case, one would not expect to experience a pro- 

 gressive change in rate as in the case of the rotation of the earth which now 

 is the measure and definition of astronomical time. On the average the 

 earth is said to be slowing down at the rate of a thousandth of a second per 

 day per century^'*^ and, according to the astronomers^^, the day will continue 

 to lengthen until finally, at some time in the distant future, the earth will 

 always face one side toward the moon and the length of the day will become 

 about 47 times as long as it is at the present time. 



Meanwhile, if an absolute standard could be established, such as now 

 appears feasible through atomic- or molecular-resonance phenomena, it 

 would be possible to record these changes through the centuries and to 

 estabhsh a relatively stable "second" that could be used for all time in 

 physical measurements in place of the elastic second of the cgs system which, 

 as now defined, must stretch with the inevitable variations in the mean 

 solar day. 



Whether or not such an "absolute" clock becomes a reality at some time 

 in the future, the quartz crystal clock, because of its accuracy, compactness, 

 great convenience and versatility is likely to continue to be a most useful 

 instrument in all precision measurements of time. 



References 



1. The Beginnings of Time-Measurement and the Origins of Our Calendar. James 



Arthur Foundation Lecture), James Henry Breasted. Published in Book, Time 

 And Its Mysteries, 1936. New York University Press. 



2. Encyclopedia Britannica — 14th Ed. — "Christian Huygens". 



3. Horologium Oscillatorium, Christian Huygens, 1673. 



4. Electrical Timekeeping, F. Hope- Jones, N. A. G. Press, London, 1940. 



5. Improvements in the Application of Moving Power to Clocks and Timepieces, John 



Barwise and Alexander Bain, British Patent No. 8783, Filed Jan. 11, 1841, Issued 

 July 10, 1841. 



6. The first electric clock, W. A. Marrison, Proceedings of the Engineering Society, 



Queens University, Kingston, Canada, v. 29, pp. 15-20, 1940. 



7. Electric Clocks, F. Hope- Jones— Book, N. A. G. Press, London, 1931. 



8. Memoire sur I'etude optique des mouvements vibratoires, Jules Lissajous, Comptes 



Rendus, v. 44, p. 727, April 6, 1857. 



9. On the use of the dynamic multiplier with a new accompanying apparatus, C. G. 



Page, American Journal of Science. 1st Series, 32, 1837, p. 354, dated at Salem, 

 Mass. April 24, 1837. 



10. Observations on induced electric currents with a description of a magnetic contact 



breaker, Golding Bird, London, Edinburgh and Dublin, Phil. Mag. Series 3, No. 

 12, 1838, p. 18. Addressed from Wilmington Square, Nov. 2, 1837. 



11. On a new magnetic electric machine. Annals of Electricity, Magnetism and Chemistry 



and Guardian of Experimental Science, vol. Ill, pp. 66-70, 1839. Translation 

 from German. Describes apparatus of Dr. Neeff of Frankfurt exhibited at 

 Friburg meeting of Philosophers, September, 1838. 



12. Science of Musical Sounds, Dayton Clarence Miller. Book, Macmillan, N. Y. 



1916. p. 29. 



13. Quelques Experiences d' Acoustique, Rudolph Konig, Paris, 1882. p. 172. 



14. On the characteristics of electrically operated tuning forks, H. M. Dadourian, 



Physical Review, v. 13, pp. 337-359, May, 1919. 



15. Isochronous and Synchronous Movements for Telegraph and Other Lines. Patent 



No. 203423, Poul la Cour. Filed April 9, 1878. 



