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



that comes from the southeast and separates the valley of 

 the Mattole River from the ocean by a width of only six 

 miles. The Mattole runs northwestward through the moun- 

 tains and breaks through the high and apparently continuous 

 mass two and a half miles northeast from Point Gorda and 

 ten miles south of Cape Mendocino. The lOO-fathom 

 plateau reaches out six miles from the point, with indications 

 of a drop to 600 fathoms within the next mile. At six miles 

 from the shore a deep submerged valley of more than 520 

 fathoms breaks through the loo-fathom plateau. 



The 25-fathom head of this valley reaches within a 

 quarter of a mile of the shore, and about one and a quarter 

 miles northeast of the mouth of the Mattole. Its general 

 direction seaward is W. SW. Out to the 300-fathom 

 depth the direction is about SW. by W. for three and 

 one third miles, and then west to 731 fathoms. The depth 

 of 100 fathoms in the valley is only one and a half miles 

 from the shore, and the sides of the valley are remarkably 

 steep. The lOO-fathom curve of the valley comes close 

 between the general 30-fathom curves of the plateau north 

 and south, where they are only one third of a mile apart. 

 The bottom of the loo-fathom plateau out to 50 fathoms is 

 varied : fine gray sand, green mud, gravel, and broken shells. 

 In the submerged valley it is green mud only in spots, the 

 principal soundings being "gray sand" and "rocky" out 

 to 730 fathoms — features shown in no other submerged 

 valley. 



This valley heads into the high mountain mass, but the 

 mouth of the Mattole, one and a quarter miles to the SW., 

 opens upon the ocean through a valley about half a 

 mile in width, after a course of three miles from the east- 

 ward. It heads close behind the hills of Point Delgada. 

 This stream does not carry much water in the dry season 

 when the mouth is sometimes closed by the sand which is 

 moved northward by the Davidson inshore eddy current. 



The geographical position of the head of this submerged 

 valley is: 



Latitude 40° 18^' north, longitude 124^ 21' west. 



