Geol.— Vol. I.] DAVIDSOS'—SUB MERGED VALLEYS. 85 



beach, is a salt pond, from which salt has been extracted for 

 many years. The surface of this pond is ten feet below the 

 surface of the bay. 



The geographical position of the head of the valley is : 

 Latitude 34° 50I' N., longitude 118° 23 1^' W. 



6. The Santa Monica Submerged Valley. 



This valley is markedly different from that of Vincente 

 or Redondo, 10 miles distant to the southeastward, with the 

 50-fathom plateau very pronounced between them. It lies 

 nearly parallel with the former and heads towards the 

 middle of the beach bounding the plains of Los Angeles. 

 Unlike the Redondo, it drops from the plateau of 50 fathoms 

 at 5^ miles from the beach, with a general direction west, 

 and a slight curve of the axis to the north. It is very much 

 larger than the Redondo. It reaches 260 fathoms in 11^ 

 miles from the beach, with the 50-fathom curve 2^ miles 

 to the E. SE. and 4^ miles to the north. 



The floor of the plateau is fine gray sand to 25 or 30 

 fathoms. In 40 fathoms, near the outermost part of the 

 50-fathom plateau, gravel and broken shells in one place, 

 but green mud thence to the greatest depths. 



The geographical position of the head of the 50-fathom 

 curve is: 



Latitude 34° 54^' N., longitude 118° 32^' W. 



7. The Point Dumb' Submerged Valley. 



Point Dume at the western boundary of Santa Monica Bay 

 is a small dome-like termination of a lower projecting plateau 

 from the southern base of the Santa Monica Mountains, 

 which rise to 1826 feet in 2^ miles, and to twice that height 

 at their culmination. It is 202 feet above the sea, and one 

 mile to the northwest from it, along the shore, opens a short, 

 moderately broad, treeless valley, called the Canada Zuma. 

 East of Point Dume the normal 25-fathom curve is i>^ miles 

 off the shore; to the westward it is about one mile distant; 



