( 



r 



r 



i 



^b 



Ji 



u 



s 4 



^ 1 



Ut 



r 



t 



4 



V - 



k 



• » 



I 



1'^ 



r 



Sect. IV.l 



TIDES, 



111 



H*»5ghts of Water. 



Fig. 1. 



1 



I 



1 



I 



I 



Times of Obw? 







e Qivisions ra 



th 



inches. 



* ■ • 



the vertical line representing feet and 



8. It is well to beojin a series of tide obseryation^ 



at 



^^ 



any place by observing the height of the water during 

 the ivhole of the day and night every half-hour or every 

 quarter of an hour. For if the rise and fall be very 



irregular, or have any features which make it ditfer much 



this means, be seen 



from the common rule, it will, 



that the case is a peculiar one, and that peculiar methods 



mv.r.t 



be used : but if there is nothing peculiar in the 

 case, the common methods may be used. 



For instance, if, instead of there being two tides In 



every (lunar) day, there be one only, or four (both which 

 cases occur at several places), these peculiarities will be 

 discovered by observations continued during the day and 



night 



) 



m 



the 



way just 



recommended. If there be a 



periodical rise and fall of the sea's surface not depen^Sng 



^ 



