16 Co-tidal lines of the Atlantic Coast of the United States. 
on the Atlantic coast from Cape Florida to Portland, Maine. I 
have been able, through the kindness of Captain Shortland, RONG . 
in charge of the Admirality a of aohbe Scotia, to "extend | 
the results to the entrance of the Bay of 
Table No. 1 gives the names of the ths “of observation with 
the time duriug which the observations of high and low water 
were made, and page ate in relation to them. The stations marked 
(*) in Table No. 2, een made use of in determining the 
co-tidal lines for this paper. A few stations have been embraced 
in the results where the number of observations is not compara- 
ble to those at the other sapere chiefly to introduce eg ee 
ae in position, and to the observations already made a 
Old Point Comfort, New York, and Boston faker hae 
ra permanent stations for some years ; Charleston, Tybee en- 
trance, Portsmouth, and Portland, have been more recently added. 
to them. 
To the short series of observations, especially there should be 
e tide gauges, more than made up for any irregularities from 
he source, and determined in hen preliminary inquiry to omit — 
these correcta which amount only to a few minutes even in 
extreme cases 
A much more important, correction is that for the position of 
the gauge ina harbor or river entrance, in many cases within a 
bar. Where our charts are completed, we have the elements for 
computing this correction by the law of depth, supposing the 
wave to move in the channel with a velocity proportional to the 
square root of the depth. This law, when applied to two very 
different cases, Savannah river and Boston harbor, where we had 
the means of testing it by measured distances and known depths, 
was so completely verified, that I have not hesitated to apply it in 
the other cases. 
The following Table No. 2 contains in the first column a num- 
ber for reference ; second the names of the stations; third, the 
mean luni-tidal intervals or establishments; fourth, the longitude 
from Greenwich; fifth, the approximate co-tidal hour obtain 
by adding to the establishment the difference of longitude ; sixth, 
a correction of one minute for every half hour of the establish- 
ment, to correct for the different transits of the moon used in re- 
ducing the observations, (see Mr. Whewell’s paper, Phil. Trans. 
1836, p. 293 ;) seventh, the co-tidal hour thus corrected ; eighth, 
the co-tidal hour corrected for depth, where data were at ‘hand for 
the purpose ; ninth, the latitude of the station. 
In order to obtain the best results from the observations, a8 ; 
have been divided into groups, in the way and from coasters = 
which will be hereafter explained 
ites 
