Geography demonstrates the matchless position of San Francisco, as metropolis of the Pacific coast, and assures her supremacy perhaps forever. The Golden Gate, a strait six miles long by one wide, with an average depth of twenty-four fathoms--seven fathoms at the shallowest point--is her pathway to the Pacific. At her feet stretches her sheltered and peerless bay, fifty miles long by five wide, with Oakland as her Brooklyn just across it. Beyond, the Sacramento and the San Joaquin empty their floods, the drainage of the Sierra Nevadas, and afford channels for trade with much of the interior. Her system of bays--San Pablo, Suisun, and San Francisco proper--contain a superficial area of four hundred square miles, of which it is estimated, eight feet in depth pour in and out of the Golden Gate every twenty-four hours. On all that coast, for thousands of miles, she seems to be the only really great harbor; and then, besides, all enterprise and commerce have so centred here, that hereafter it will be difficult, if not impossible, to wrest supremacy from her. Until we reached Salt-Lake, New York everywhere ruled the country, and all business ideas turned that way; but from there on, the influence of Gotham ceased, and everything tended to "'Frisco," as many lovingly called her. This was her general name, indeed, for short, all over the Pacific coast; though the Nevadans spoke of her, as "the Bay" still. The city itself stands on a peninsula of shifting dunes or sand-hills, at the mouth of the harbor, much the same as if New York were built at Sandy Hook. It was a great mistake, that its founders did not locate it at Benicia, or Vallejo, or somewhere up that way, where it would have been out of the draft of the Golden Gate, had better wharfage, and been more easily defended. But, it seems, when the gold fever first broke out, in 1849, the early vessels all came consigned to Yerba Buena, as the little hamlet was then called; and as their charter-parties would not allow them to ascend the Bay farther, their cargoes were deposited on the nearest shore, and hence came San Francisco. It took a year or more then to hear from New York or London, and before further advices were received, so great was the rush of immigrants, the town was born and the city named. Benicia tried to change things afterwards; but 'Frisco had got the start, and kept it, in spite of her false location. Her military defences are Fort Point at the mouth of the Golden Gate, Fort San Josè farther up the harbor, and Alcatraz on an island square in the entrance, which with other works yet to be constructed would cross-fire and command all the approaches by water, thus rendering the city fairly impregnable.