The most valuable natural bridge In the world is to be found at Arizona, lying across a deep chasm 40 feet in ■width. It is a petrifled tree about 4 feet in diameter, and about 100 feet in length. It is pure agate all through, and therefore is much more valuabla as regards material than any bridge of marble or granite would be. But the most expensive material of which a bridge has ever been built is probably telegraph wire. One was built over the Jhelum river at Kohala, in the Punjab, In the place of a bridge which wUs swept away by the floods in 1892. A similar bridge was constructed during the flrst Soudan campaign over th Kokora river for military purposes.