The bridge was built of stone, on arches, and was of the most massive and ponderous character. There was a roadway in the centre of it, on which two continued streams of vehicles were passing--one on the left, going into the city; and the other on the right, coming out. On each side were broad stone sidewalks, formed of massive blocks of granite, feeling solid and heavy under the tread as if they had been laid upon the firm ground. These sidewalks were crowded with passengers, who were going, some into, and some out of, the city, so as to form on each sidewalk two continuous streams. On each side of the bridge, towards the water, was a solid parapet, or wall. This parapet was about as high as Rollo's shoulders. Here and there, at different places along the bridge, were groups of people that had stopped to look over the parapet to the river. Each group formed a little row, arranged along the parapet, with their faces towards the water. "Let us stop and look over," said Rollo. "No," said Mr. George, "not now; we will wait till we get to the middle of the bridge." So they walked on. When they had proceeded a little way, they came to a place where there was a sort of niche, or recess, in the parapet, perhaps ten or fifteen feet long, and four or five deep, from the sidewalk. There were stone seats extending all around the sides of this recess; and these seats were full of boys and men, some with burdens and some without, who had stopped and sat down there to rest. Rollo wished to propose to Mr. George that they should stop and sit down there too; not because he was tired, but only to see how it would seem to be seated in such a place. He did not propose this plan, however, for he saw at a glance that the seats were all occupied, and that there was no room. A little distance beyond they came to another niche, and afterwards to another, and another. "These niches are over the piers of the bridge," said Mr. George, "I suppose. Let us look over and see." So they stopped a moment and looked over the parapet. They beheld a turbid and whirling stream pouring through the bridge, under the arches, with a very rapid current, and at the instant that they looked down, they saw the bows of a small steamboat come shooting through. The deck of the steamer was crowded with people--men, women, and children. Some were standing, and others were sitting on benches that were arranged round the side and along the middle of the deck; all, however, in the open air. "I wonder where that steamer is going," said Rollo. "Down the river somewhere," said Mr. George; "perhaps to Greenwich or Woolwich." "_Up_ the river, you mean," said Rollo. "Don't you see she is going against the current? See how swift the water runs under the arches of the bridge!"