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THE GLACIAL OR POST-GLACIAL DIVERSION OF 
THE BRONX RIVER FROM ITS OLD CHANNEL. 
By J. F. Kemp. 
As one of the Scientific Directors of the recently organized 
New York Botanical Garden, the writer has had frequent oc- 
casion to visit Bronx Park in the last two years. In one of 
the earliest of these visits the anomalous relations of the Bronx 
River to what is its natural line of drainage were noted, and 
in subsequent ones attempts have been made, not, it must be 
admitted, with altogether satisfactory results, to explain the 
present channel. The facts are briefly as follows: 
The Bronx River takes its rise a few miles above White 
Plains and flows southward for thirty miles into the western 
extremity of Long Island Sound. For much the greater part 
of its course, it occupies a valley, excavated in a belt of 
crystalline dolomite that is almost continuous to the salt water. 
The valley is similar to the usual type of valley in West- 
chester County, and doubtless owes its depressed character to 
the easy erosion of the dolomite. The depression is used by 
the Harlem Railroad from a point just below Morrisania, north- 
ward until it crosses into the drainage basin of the Croton 
River. The Bronx, however, at a point a half a mile or so 
below Williamsbridge, and just above Bedford Park Station, 
and in the upper portion of the area assigned to the Botanical 
Garden, abruptly leaves its old valley and breaks across the 
enclosing ridge of gneiss, in a gorge 75 feet deep. For 
nearly a mile it occupies this gorge and then reaching more 
open country, with a rocky fall at Bronxdale and another at 
West Farms, it makes its way to the sound. 
Just below Williamsbridge it flows against the west side 
of the valley, and immediately alongside of the railroad. It 
then leaves this and passes diagonally to the south, being di- 
verted in part by a broad and flat terrace of coarse, rounded, 
cobble stones, up to one foot or more in diameter and with 
comparatively little sand intermingled. The cobbles have 
