266 CALIFORNIA ACADEMY OF SCIENCES. 



Submarine Valley 1. The latest developments of sub- 

 marine valleys are near the high, bold coast under Cape 

 Mendocino. A submarine ridge runs southward from 

 Point Delgada at Shelter Cove, in latitude 40° 01', for ten 

 miles or more. But the depth of the marginal plateau at 

 100 fathoms is about six or seven miles from the shore. 

 Just north of this bank, off Shelter Cove, there has been 

 developed a deep submarine valley where it breaks through 

 the marginal plateau and runs sharply into the immmediate 

 coast-line under the culminating point of the crest-line of 

 mountains. The head of this submarine valley is 100 fath- 

 oms deep at one and a quarter miles from the shore, and 

 the depth of 25 fathoms almost reaches to the rocks under 

 the clitfs. The mountain peak toward which it points is 

 4,236 feet above the sea and only two and a half miles in- 

 side the shore line. The 100 fathom line lies six miles off 

 Point Delgada, but where the valley breaks through the 

 marginal plateau the depth reaches 400 fathoms. The slopes 

 of the sides of this valley are verv steep. 



Submarine Valley II. Hence northwestward to Point 

 Gorda the 100 fathom line of soundings continues nearly 

 parallel with the coast line except about midway, where a 

 minor submarine valley 300 to 150 fathoms deep stretches 

 sharply toward the shore, and within two and a half miles 

 thereof. The head lies two and a half miles south by east 

 from Spanish Flat, under the mountains. But immediately 

 north of the point, there is a very deep submarine valley 

 which comes in from the westsouthwest, and heads close un- 

 der the shore three miles north of Point Gorda, and there- 

 fore less than a mile north of the mouth of the Mattole 

 Eiver. 



The head of this great submarine valley, at the 30 fathom 

 line, is only one-third of a mile from the shore in latitude 

 40^ 18i'. The depth of 100 fathoms in the valley is only 

 one and a half miles from shore, and the sides of the valley 



