It was such a tremendous explosion that it shook the solid buildings of the city. It also brought Jerry upon his feet, all standing, where he had been asleep for the night in a vacant niche against a stone warehouse. A great many of the people slept this night in the open air, just where they chanced to be, so that they might miss no excitement. The explosion awakened them all. There was a rush for good viewpoints; perhaps the battle had begun. Right speedily Jerry had scrambled atop the wall at a place between batteries, from which he could see the harbor and the Americans’ beach eastward. Nobody objected to him, here. “Boom――_Boom!_” A double explosion well-nigh knocked him backward. A cloud of black smoke had spurted from the walls of San Juan de Ulloa castle, a quarter of a mile before; but yonder amidst the sand hills the louder “_Boom!_” had raised a much greater, blacker smoke, where the shell had burst. The people upon the wall cheered. “Viva, viva!” “Now we shall see. San Juan is speaking with his giants.” “Yes, the Paixhans,” said a Volunteer. “It is the Paixhans that he is turning loose, to blow the Yankees up. Viva!” The Paixhan guns were large pieces that threw shells in a line, instead of solid shot or high-sailing bombs like the mortars. “Boom!” from the castle; and in a moment, “_Boom!_” from the thickets of the dunes. The smoke jetted angrily; the people imagined that they could see brush and trees and bodies flying through the air; but just how much damage was being done no one might say, because most of the American army was out of sight, concealed in the wilderness of the jungle. General Morales, commanding the city and castle, had issued a proclamation calling upon the soldiers and citizens to rally for the defense. All this day the American boats, large and small, plied back and forth between the fleet and the shore, out of range, bringing in horses and mules and cannon and supplies; when the cannon had been landed, soldiers and sailors fell to like ants and helped the long teams drag them across the beach, into the sand hills. The larger part of the army had been swallowed by the chaparral; but now and again a column of blue-uniformed men could be sighted, winding through a cleared spot, as if gradually encircling the city on the land side. All day the city forts and outworks and the castle pitched round-shot and shell into the dunes. There were several little battles when the Mexican lancers and infantry outposts met the American advance. A number of wounded Mexican soldiers were carried in; but the American flags kept coming on, bobbing here and there, bound inland. “To-morrow it will blow,” the weather prophets asserted, noting the yellow sunset. “A norther! Then those gringos will wish they were somewhere else.” “Yes, that is so.” Sure enough, about noon the next day (which had dawned calm), far out at sea a sharp, vivid line of white appeared, approaching rapidly.