THE CONQUEST OF TIME AND SPACE 



How to determine this, was a problem that long taxed 

 the ingenuity of the astronomer. The solution came 

 finally through the invention of the chronometer, 

 which is in effect an exceedingly accurate watch. 



Time measurers of various types have, of course, been 

 employed from the earliest times. The ancient Oriental 

 and Classical nations employed the so-called clepsydra, 

 which consisted essentially of receptacles from or into 

 which water dripped through a small aperture, the 

 lapse of time being measured by the quantity of water. 

 At an undetermined later date sand was substituted 

 for the water, and the hour glass with which, in some 

 of its forms, nearly everyone is familiar, came into use. 

 For a long time this remained a most accurate of time 

 measurers, though efforts were early made to find 

 substitutes of greater convenience. Then clocks 

 operated by weights and pulleys were introduced; and, 

 finally, after the time of the Dutchman Huygens, 

 the pendulum clock furnished a timepiece of great 

 reliability. But the mechanism operated by weight or 

 pendulum is obviously ill-adapted to use on shipboard. 

 Portable watches, in which coiled springs took the place 

 of the pendulum, had indeed been introduced, but the 

 mechanical ingenuity of the watchmaker could not 

 suffice to produce very dependable time-keepers. The 

 very idea of a watch that would keep time accurately 

 enough to be depended upon for astronomical observa- 

 tions intended to determine longitude was considered 

 chimerical. 



Nevertheless the desirability of producing a portable 

 time-keeper of great accuracy was obvious, and the 



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