Co-tidal lines of the Pacific Coast of the United States. 27 
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long to the same group. ‘The computations required in these 
discussions were generally made by Mr. Heaton of the Tidal 
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Division under my immediate direction or that of Assistant 
‘Pourtales, 
Chart of Co-tidal lines. 
__, From this discussion I have drawn a chart of approximate co- 
tidal lines for the coast of Oregon and California (see plate). The 
Chart on a scale of -, 553, same which was used in pre- 
senting the cotidal lines of the Atlantic coast of the United 
States, shows the general configuration of the coast. 
_ The cotidal hours are marked near the several tidal stations. 
The straight lines resulting from the discussion of the north- 
ern and middle groups are delineated for the northern group the 
cotidal lines of x1x and xx hours, and for the middle group of 
XVII, XVIII, x1x and ‘xx hours. 
“he curves representing the approximate cotidal lines of 17, 
18, 19 and 20 hours are drawn in dotted lines, the character of 
the dots differing for the several lines. 
The line of 174 hours would follow the coast nearly from San 
Diego to Point Conception, then the line of 18 hours nearly to 
Point Pinos, North of this point the lines of eighteen and nine- 
teen hours meet the coast obliquely at an angle of about ten 
degrees, the line of 20 hours appearing near Point Arena and 
following the coast generally to Cape Disappointment, the re- 
ceding parts having a little later and the projecting parts a little 
earlier hour 
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