Having recently again examined the Niagara falls and gorge with especial reference to the Older channel of Saint Davids, I believe that a most important element in the history of the gorge erosion has been overlooked by some observers, and that by others its evidences have been misunderstood. This paper shows that the small preglacial stream which eroded the Saint Davids and Whirlpool channel, having a great depth beneath the river in the Whirlpool, must have flowed for a considerable distance, before reaching that depth, in a gradually widening and deepening ravine, coinciding with the present gorge along the Whirlpool rapids. Because the Niagara river found there a drift-filled narrow ravine, which it cut to the present size of the gorge, its erosion took place in that part by rapids and cascades. Southward from the head of the old ravine the river has eroded its gorge by a great . . .