Some rivers suddenly disappear, by flowing into a chasm, and are lost in the earth. Some of these again issue from the earth at a great distance from where they disappeared.
Rivers present obstacles to the route of roads, and many expedients have been invented by the ingenuity of man to obviate them. In many places bridges are built of wood, stone or iron; and where the current is too swift, or the channel too deep to permit a bridge to be built, the passage is made in boats. But the most astonishing project that has been undertaken for this purpose is the Tunnel under the river Thames, at London, England. A road is here dug out under the river, and is nearly completed. A view of the work is given in the cut.
THAMES TUNNEL.
The tunnel consists of two brick archways for carriages, and two foot paths. The passages are divided by a line of arches, between the pillars of which are placed gas lights. This undertaking was commenced in the year 1825. The whole length is thirteen hundred feet, and each archway is about fourteen feet in width. The thickness of the earth between the bed of the river and the tunnel is about fifteen feet.
A country, possessed of large and navigable rivers, enjoys a great blessing. They form a means of internal communication, by which the productions of the inland country are brought to the city and seaport. Their currents are made use of, by the aid of machinery, to manufacture many of the necessaries and luxuries of life.
Many rivers whose waters are pure, afford water for the use of the inhabitants of neighboring cities.
London and Westminster, England, are supplied from the New river; the water is here brought thirty-eight miles through a canal. The Schuylkill river in Pennsylvania, United States, supplies the city Philadelphia with good and wholesome water, for the use of the inhabitants.
VIEW OF THE PHILADELPHIA WATERWORKS.