CHAPTER XII 

 SAN FRANCISCO BAY AND GOLDEN GATE 



A Great Natural Harbor 



One of the world's greatest natural harbors is at San Fran- 

 cisco. Ships from the Seven Seas enter and depart through the 

 Golden Gate. The sea-level waters of San Francisco Bay lie in 

 a basin athwart the Coast Range of mountains. Through a 

 notch in the mountain range the commerce of the world comes 

 and goes to and from the great port. The waters of the great 

 rivers that drain the large central valley of California, the San 

 Joaquin and Sacramento, and these include the vast number of 

 streams that flow down the western slope of the great Sierra 

 Nevada Range, reach the ocean through the narrow pass of the 

 Golden Gate. In turn the tides from the ocean surge in, min- 

 gling the salt waters of the sea with the fresh waters of the 

 streams. To and fro ebb the tides, and thus intermittently the 

 waters of the San Joaquin and Sacramento reach the sea. If a 

 dam were imagined to be constructed across the Golden Gate, 

 the narrow pass between the Presidio and the Marin Peninsula 

 promontory, or if the mountain range were imagined to be not 

 broken in two, a vast lake of fresh water would be impounded 

 over San Francisco and far north and south covering Sacra- 

 mento and Stockton, and perhaps finally discharging to the 

 ocean through Monterey Bay. 



Such a flight of the imagination is not entirely visionary. 

 The sea has been far over the land where San Francisco is now, 

 and over a vast region to the north and south. This is shown 

 by the formations that mantle the coast ranges to the north 

 and south, now partially eroded away. If on the other hand 

 the region about San Francisco Bay were depressed a few hun- 



