construction, and became a memorable occasion in the annals of mechanical science, and immortalized the name of Stephenson. We find great national significance in the history of bridges in different countries. Their costly and substantial grandeur in Britain accords with the solid qualities of the race, and their elegance on the Continent with the pervasive influence of Art in Europe. It is a curious illustration of the inferior economical and high intellectual development of Greece, that the "Athenians waded, when their temples were the most perfect models of architecture"; and equally an evidence of the practical energy of the old Romans, that their stone bridges often remain to this hour intact. Our own incomplete civilization is manifest in the marvellous number of bridges that annually break down, from negligent or unscientific construction; while the indomitable enterprise of the people is no less apparent in some of the longest, loftiest, most wonderfully constructed and sustained bridges in the world. We have only to cross the Suspension Bridge at Niagara, or gaze up to its aerial tracery from the river, or look forth upon wooded ravines and down precipitous and umbrageous glens from the Erie Railway, to feel that in this, as in all other branches of mechanical enterprise, our nation is as boldly dexterous as culpably reckless. As an instance of ingenuity in this sphere, the bridge which crosses the Potomac Creek, near Washington, deserves notice. The hollow iron arches which support this bridge also serve as conduits to the aqueduct which supplies the city with water.