78 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



except off the face of the Sierra Santa Lucia. This deep 

 plateau gradually shoals to the northward of Cape 

 Mendocino, and 196 miles off the coast, between Cape 

 Disappointment (46° 16') and Cape Flattery (48° 24'), a 

 depth of only 1,535 fathoms is reached. Generally there is 

 a marginal plateau of ten miles width out to the 100 fathoms 

 curve; and thence the descent is sharp to 500 and 1,000 

 fathoms. Only along a few parts of the coast does this 

 lOO-fathom plateau stretch out beyond ten miles, as follows: 



The Coronados and San Diego Plateau. — This com- 

 paratively broad plateau from the southward of Los Coro- 

 nados Islands to Point La Jolla reaches out as much as fifteen 

 miles, and the 30-fathom line marks the inner edge of 

 muddy bottom. 



The Gulf of the Farallones. — The off shore soundings 

 from Point Cypress (latitude 36° 35') to the Farallones (lati- 

 tude 37° 43), 82 miles, show that the lOO-fathom plateau 

 stretches off shore only five miles to the north of Point Pinos, 

 and seven miles off El Jarro, west of Santa Cruz. Thence it 

 increases to 14 miles in width off Ano Nuevo, latitude 37° 06', 

 and runs northwest to five miles off the Southeast Farallon, 

 where it is 32 miles from the Golden Gate. It continues 

 northwestward 22 miles to and beyond the Cordell Bank, in 

 latitude 38° 01', and again approaches the coast under Fort 

 Ross, latitude 38° 30', where it is only eight miles wide. 



The Humboldt Plateau. — There is a narrow plateau 

 of eight miles northward of Cape Mendocino, off the low 

 areas of the Humboldt Bay region. It continues thence to 

 Point St. George, latitude 41*^ 50', before reaching which it 

 is 15 miles wide in latitude 41° 30'. 



The Heceta Bank. — In the latitude of the Umpquah River, 

 43° 40', this plateau of 100 fathoms lies ten miles off shore; 

 thence it trends off shore quite rapidly until in latitude 44° 

 03' it is 32 miles from the comparatively low shores; thence 

 it uniformly moves shoreward until in latitude 44° 44'. It is 

 about 12 miles off Cascade Head, in latitude 45° 03', and 

 continues so for some distance northward. 



From the numerous streams and low-lying valleys that 



