It is rumored again that a survey is soon to be made through the heaviest portion of the Black Canon of the Gunnison. For a long distance the walls of syenite rise to the stupendous height of 3,000 feet, and for 1,800 feet the walls of the cañon are arched not many feet from the bed of the river. If the survey is successful, and the Denver and Rio Grande is built through the cañon, it will undoubtedly be the grandest piece of engineering on the American continent. The river is very swift, and it is proposed to build a boat at the western end, and provision it for a length of time, allowing it to float with the stream, but controlled by ropes. If the boat goes, the chances are that the baby road goes, too.--Gunnison (Colo.) Review.