Under Stockton's directions, there was built at Philadelphia a vessel of war, which he named the "Princeton," and which was constructed according to his plans. On her deck were two great guns of wrought iron, which were also devised by him; and each of these carried a two hundred and twenty-five pound shot,--much heavier than those then used in naval warfare. Great public interest was excited in the "Princeton," the first steamship of our navy, and on her trial trip she was found to be an excellent seagoing vessel. She went to Washington, and there started out on an excursion, during which her great guns were to be tried. There was a very distinguished company on board,--officers of the army and navy, and several members of the Cabinet, and other guests. It was found, however, that the ship was much superior to her great guns; for when one of them, named the "Peacemaker," was fired, it exploded, killing several people, among whom were the secretary of war, the secretary of the navy, and the father-in-law of the President; while others, including Captain Stockton, were wounded. This terrible event shocked the whole nation; but although there were no more wrought-iron cannon made, the building of naval steamships, which began with Stockton's "Princeton," went steadily on, growing and improving, until it reached the high point shown by the swift and powerful ironclad men-of-war which now fly the stars and stripes. In 1846 Stockton found himself on the coast of California, with the rank of commodore, and in command of a squadron. Since he had started from the United States, war had been declared with Mexico; and when he arrived, the towns of Monterey and San Francisco had been taken by Commodore Sloat, who had preceded him. A state of war exactly suited Stockton's disposition; and as there was no more immediate need of fighting on the seacoast, he organized a little army of marines and sailors from his ships, which was afterwards joined by a body of adventurers and hunters of the United States, and also by Lieutenant-Colonel Fremont, an officer of the United States Army, who had been sent into that region to explore the country, and who had already done some fighting with the little band under his command. Los Angeles, the Mexican capital of California, was attacked and taken. Commodore Stockton now declared himself the conqueror of California, and organized a provisional government for the captured territory, appointing John C. Fremont as governor.