But a sketch of Marin, however cursory, would be incomplete without her southern isle, for besides the United States Barracks, situated on the western part of the Island, there is located in a northern cove the Federal quarantine station, that most necessary adjunct of San Francisco, which prevents contagion by quenching the pestilence often brought to our shores from the Orient and South American ports. Besides its present significance the Island has another and far older claim on our attention. In the summer of 1775, Juan de Ayala, a lieutenant of the Royal Spanish Navy, was given a commission from Junipero Serra and Bucareli, the Mexican Viceroy, to proceed to "the arm of the sea" lying north of Monterey, which had been twice viewed by the padres from the land, to ascertain if it were a canal or bay, and make a survey of it. Pursuant to these instructions Ayala cautiously crept up the Coast and on the ninth day sighted the narrow passage which is now known the world over as the Golden Gate. [Illustration: In the Canyon.] A crude launch was sent to explore the opening, which was found to be deep and without obstructions. By the time the launch returned it had grown dark, nevertheless Ayala headed for the Bay and on the night of August 5, 1775, the San Carlos sailed in through the Strait, the first ship that ever passed the pillared passage or entered what is now known as the Bay of San Francisco. Having entered safely, Ayala moored his vessel just inside the Bay, and the next morning, looking around him, selected an island not far from the entrance as a convenient spot to make his headquarters. [Illustration: Angel Island from the Mainland.] Upon examination, he found a suitable place for mooring his vessel, also wood and water in abundance. This Island was then named Nuestra Senora de Los Angeles, the appellation which it still bears, though shortened to Angel Island. On the mainland, directly across from the Island, lies Tiburon, the ferry and terminus of the California Northwestern Railroad. Besides the Company's shops, Tiburon consists mainly of stores--in short all that is included in the usual "Water Front." The most interesting object in Tiburon is on the road between that place and Belvedere. This is none other than the remains of a remarkable old hulk, now beached and converted into a habitation. Besides its unique appearance, there is an interesting tale connected with the Tropic Bird which is something like the following: "Early in the year 1850 the good ship, Tropic Bird, Captain Homans skipper, set sail from Gloucester, Mass., with a cargo of general produce bound for the Golden Gate. On board was a mixed crew, seafaring men and land lubbers, all having but one hope, one idea--the far-famed gold fields of California. A good true ship was the Tropic Bird and a good true man her skipper, who had with him his brother.