尼亚加拉的厄运预言。
今年湖水平一直很高,布鲁里溃疡t, in spite of that fact, Professor G. K. Kinder, of the United States Geological survey, still insists that eventually the water from the great lakes will reach the ocean by the Illinois river and the Mississippi rather than through Niagara. “The slow changes of mean water level (says Prof. Gilbert) are concealed from ordinary observation by the more rapid and impressive changes due to variations of volume, but they are worthy of consideration in the planning of engineering works of a permanent character, and there is at least one place where their influence is of moment to a large community. The city of Chicago is built on a smooth plain, little above the high-water level of lake Michigan. Every decade the mean level of the water is an inch higher, and the margin of safety is so narrow that inches are valuable. Already the older part of the city has lifted itself several feet to secure better drainage, and the time will surely come when other measures of protection are imperatively demanded. Looking to the more distant future, we may estimate the date at which the geographic revolution prophesied by Spencer will occur. Near Chicago is an old channel made by the outlet of a glacial lake. The bed of the channel at the summit of the pass is about eight feet above the mean level of lake Michigan and five feet above the highest level. In 500 or 600 years (assuming the estimated rate of tilting) high stages of the lake will reach the pass, and the artificial discharge by the canal will be supplemented by an intermittent natural discharge. In 1.000 years the discharge will occur at ordinary lake stages, and after 1,500 years it will be continuous. In about 2,oco years the discharge from lakes Michigan, Hu ron and Erie, which will then have substantially the same level, will be equally divided between the western outlet at Chicago and the eastern at Buffalo. In 2,500 years the Niagara river will have become an intermittent stream, and in 3,000 years all its waters will have been diverted to the Chicago outlet—the Illinois river, the Mississippi river and the Gulf of Mexico.”
今年湖水平一直很高,布鲁里溃疡t, in spite of that fact, Professor G. K. Kinder, of the United States Geological survey, still insists that eventually the water from the great lakes will reach the ocean by the Illinois river and the Mississippi rather than through Niagara. “The slow changes of mean water level (says Prof. Gilbert) are concealed from ordinary observation by the more rapid and impressive changes due to variations of volume, but they are worthy of consideration in the planning of engineering works of a permanent character, and there is at least one place where their influence is of moment to a large community. The city of Chicago is built on a smooth plain, little above the high-water level of lake Michigan. Every decade the mean level of the water is an inch higher, and the margin of safety is so narrow that inches are valuable. Already the older part of the city has lifted itself several feet to secure better drainage, and the time will surely come when other measures of protection are imperatively demanded. Looking to the more distant future, we may estimate the date at which the geographic revolution prophesied by Spencer will occur. Near Chicago is an old channel made by the outlet of a glacial lake. The bed of the channel at the summit of the pass is about eight feet above the mean level of lake Michigan and five feet above the highest level. In 500 or 600 years (assuming the estimated rate of tilting) high stages of the lake will reach the pass, and the artificial discharge by the canal will be supplemented by an intermittent natural discharge. In 1.000 years the discharge will occur at ordinary lake stages, and after 1,500 years it will be continuous. In about 2,oco years the discharge from lakes Michigan, Hu ron and Erie, which will then have substantially the same level, will be equally divided between the western outlet at Chicago and the eastern at Buffalo. In 2,500 years the Niagara river will have become an intermittent stream, and in 3,000 years all its waters will have been diverted to the Chicago outlet—the Illinois river, the Mississippi river and the Gulf of Mexico.”
