NAUTICAL REMARKS. 42/ 



and eddies, and odier irregularities of the stream, sometimes 

 dangerous to boats. The anchorage at Yerba Buena Cove is 

 free from these annoyances, and the passage up to it is nearly 

 so after passing the Presidio. The ebb begins to make first 

 from the Santa Clara arm, and runs down the south shore a 

 full hour before the flood has done about Yerba Buena and 

 Angel Island ; and the flood, in its return, makes also first 

 along the same shore, forcing the ebb over the Yerba Buena 

 side, where it unites with the ebb from the north arm. 



The flood first strikes over from the Lime Rock*, and pass- 

 ing tlie Island of Alcatrasses, where it diverges, one part goes 

 quietly to Santa Clara : the other sweeping over the sunken 

 rock, and round the east end of Angel Island, unites with a 

 rapid stream through the narrow channel formed by Angel 

 Island and the main, and both rush to the northward through 

 the Estreciio de San Pablo to restore the equilibrium of the 

 basin beyond, the small rocks of Pedro Blanco and the Alca- 

 trasses Island lying in the strength of the stream. 



The mean of eighty observa- 

 tions gave the time of high 



water (full and change) at 



Yerba Buena anchorage lOh. 52m. 

 The tide at the springs rises 7ft. lOin. sometimes 8ft. Sin. 



Neap ... 1 10 

 Average rate of ebb at spring 



tide 2k. Of. at neap . Ik. Of. 



Flood ..10 . 6 



Duration of flood . . . 5h. 25m, 

 At Sausalito the mean ofseven- 



teen observations gave the 



time of high water (full and 



change) 9 51 



Rise (full and change) . . 6ft. Oin. 



Neap 2 6 



Duration of flood , . . 4h. 43m. 



* See the Chart, 



