In 1972, when modern explorers discovered a connection between the Flint Ridge Cave system to the northeast and Mammoth Cave, they were astonished to discover that the Mammoth Cave end of the connection was actually indicated as a passage lead on Bishop's map. (It is seen as a long thin line branching off from the eastern end of the Echo River complex.) The construction in 1905 of a dam on the Green River in the interim caused the passage to be flooded (and therefore inaccessibly hidden by murky water) most of the time after the dam's completion, and the passage was rediscovered backwards, from its remote end, by cavers entering the Flint Ridge Cave System. Although he never knew its significance, Bishop had unwittingly shown the key to connecting two major components of the longest cave in the world, 130 years before the connection was made.