470 



WHAT IS THE TIDE OF THE OPEN ATLAN1IC ? 



A comparison of Whewell's two maps of British cotidals, fig- 

 ures 3-4, with Dr Young's 1807 sketch, figure 2, shows the grow- 

 ing appreciation of the contouring tendencies of cotidals. With 



the abundance of fairly good 

 data at hand today, it is every- 

 where observed that cotidal 

 lines adjust themselves closely 

 to the shore line. With rea- 

 sonable depth, it is quite usual 

 for high water to appear far up 

 a bay as early as at its mouth. 

 High water reaches the head 

 of Placentia bay, Newfound- 

 land, about a half hour before 

 it reaches the headlands on 

 either side of the mouth, as 

 may be seen on the accompa- 

 nying sketch, figure 5, where 

 three stations are shown, at 

 the bay head and at either 

 side of the entrance. The up- 

 per figures at each place indicate the interval between high 

 water at St Johns and local high water. The lower figure indi- 

 cates the tidal range in feet. From the line of 100 fathoms it is 



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FlGUHE 3 



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