8 On Cotidal lines of Diurnal and Semi-diurnal Tides 
posed. The same is true for group E, St. George’s, Pensacola, 
and Fort Morgan. The more general group F, including the 
stations from Cedar Keys to South West Pass agrees in its indi- 
cations with those given by the partial groups, as does also G, 
including the stations from St. George’s to South West Pass. In 
passing westward and southward the direction of the line changes 
rapidly and no satisfactory adjustment by groups could be 
made. From Sout est Pass to Brazos Santiago the smaller 
stations. The mean cotidal line for each group and the hour 
before and after the mean hour are marked on the map, showing 
the direction and velocity of the diurnal wave as given by the 
groups. From a consideration of these and of their necessary 
connection the cotidal lines are approximately drawn. The great 
cotidal line of the Gulf as traced upon the chart is that of twenty 
ve hours. ; 
The cotidal lines of 19 to 23 hours only appear on the coast 
of the Florida Keys. The line of 24 hours is well marked near 
Egmont Key (Tampa). The line of 26 hours is at the head of 
the bight between St. George’s and Cedar Keys, and in that 
near Cat Island. The line of 27 hours appears only at the head 
of the bay formed by the coasts of Texas and Louisiana. 
The table No. 5 of semi-diurnal tides is in the same form as 
No. 3 for diurnal tides. It contains a number for reference, the 
name of the station, its latitude, the longitude in arc and in time, 
the establishment, the same in Greenwich time, the correction for 
transit and for depth, and the corrected cotidal hour. 
n tracing the semi-diurnal wave as it enters the Straits of 
Florida we find after a slight contradiction between Cape Florida 
and Indian Key, a general increase of the cotidal hour in the 
Tight direction to the Tortugas. The semi-diurnal wave here 
gives a difference of time between Cape Florida and the Tortuga: 
of but 14, 24m, while the diurnal wave gave 44, 03", The la 
ging of the diurnal wave which at Cape Florida was 14, 44, at 
us Key is 3h, 22m, at Key West 4%, 31™, and at the Tortugas 
| é j 
The semi-diurnal wave passes across the Gulf to the South 
West Pass as did the diurnal. The time of crossing by the 
semi-diurnal wave is, however, 1», 18m, while by the diurnal 
wave it was 15, 50m, ae ae ae 
