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[Sect. IV, 



SEOTfO^- IV. 



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TIDES 



BY THE JREV. Dll. WHEWELL 



Directions f)r Tide Observations. 



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1. In making tide observations, the main object is, in 

 the first place, to refer the tides to the motions of the 

 moon, by which they are, in most places, mainly go- 



verned. 



F- 



v/ 



r 



this purpose, the time and height of high water 



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this time will have to be compared with the time of the 

 moon's passage across the meridian of the place. 



of the moon's transit) may be 

 the common table given in the Nautical 



known 



Almanac, or in other books of the same kind. 



2. The time of high water (and low water) may some- 

 times (when the sea is calm) be observed with sufficient 

 accuracy by observing the surftice of the sea, where it 



washes a vertical scale fixed 

 divided into 



and inches. 



in the open water, and 

 The moment when the 

 water is highest (and lowest) must be observed by a 

 watch or clock, well regulated, or corrected for its error. 

 3. In general, the waves will make it difficult to ob- 

 serve the moment of the highest (and lowest) open water 

 with much aecura(5v. The following methods may be 



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Seci 



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used 



watei 

 wate 



be a 

 carr] 



strin 



by 



a 



IS 01 



on a 



nal 



SI 



affec' 

 ma) 

 4. 

 lowe; 



high' 



eithc 

 larl\ 



If 



neitl 

 ceas 



and 

 hi el 



V.J 



5 



ter\ 



ev(^ 



of 

 ho 



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