UOMMERCE. 1T9 



land, which are covered by high and dense timber, and offer 

 an excellent protection against the strong winds of the coast. 

 The mouth of the bay, in latitude 40 44', is a mile across, but 

 has breakers on each side ; and between them is a channel, a 

 quarter of a mile wide, with about eighteen feet of water at 

 low tide. The greater part of the bay is shallow, but there is 

 an abundance of deep water, with good anchorage and perfect 

 safety for. shipping. The entrance is considered dangerous, 

 and a steam-tug escorts nearly all sailing-vessels in and out. 



The difference between Extreme high tide and extreme low 

 tide is about nine feet at- Crescent City, eight feet at San 

 Francisco, and seven feet at San Diego. The mean difference 

 between the highest tide and the lowest low tide in one day, 

 at San Francisco, is less than six feet. 



George Davidson, of the U. S. Coast Survey, in his Coast 

 Pilot, says : " As a general rule there are, upon the Pacific 

 Coast of the United States, one large and one small tide dur- 

 ing each day. * * * The corrected establishment, or mean 

 intervals between the moon's transit and the time of high 

 water at Fort Point, San Francisco Bay, is 12 hours, 6 min- 

 utes." 



131. Navigable Streams. The Sacramento River is nav- 

 igable for steamers dra wing three feet of water, to Sacramento 

 City, and to Red Bluff for boats drawing fifteen inches. The 

 Feather River is navigated by steamers drawing fifteen inches, 

 to Marysville, seventy-five miles from Sacramento ; and boats 

 have ascended to Oroville, twenty-five miles farther. Steam- 

 ers drawing five feet can run regularly to Stockton, on the San 

 Joaquin, a distance of one hundred and thirty miles from San 

 Francisco ; and in times of high water, a boat drawing about 

 fifteen inches ascends to Fresno City, one hundred and fifty 

 miles farther. A number of sloughs or tide- water creeks, 

 navigable for small vessels, open into the bays of San Fran- 

 cisco, San Pablo, and Suisun. The most notable of these are 

 the Alviso or Guadalupe slough, at the head of San Francisco 



