18 TRANSACTIONS OF THE [OOT. 19, 



now that the broad facts are proven or indicated the geologist 

 ma}- devote his time more to details, and thus much confirmatory- 

 evidence ma}^ be expected in the future. 



Maps, Charts and Specimens Exhibited. 



1. Rhode Island. Block Island Sheet. U. S. Geol. Surve}-. 



2 Chart of Long Island and eastward, showing submarine 

 contours, prepared from the U. S. Coast Survey maps of the 

 region. 



8. Geological Map of New Jersey. Geol. Survey, N. J., 1881. 



4. Specimens of plants and molluscs in hardened clay and 

 marl, from Montauk Point and Block Island. 



The following paper was then read with illustrations by 

 means of the lantern and maps. 



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 occa- 

 sion 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 ad- 

 mitted, with altogether satisfactory results, to explain the pres- 

 ent 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 w-estern ex- 

 tremity of Long Island Sound. For much the greater part of 

 its course, it occupies a valley, excavated in a belt of crjstal 

 line dolomite that is almost continuous to the salt water. The 

 valley is similar to the usual type of valley in Westchester 

 county, and doubtless owes its depressed character to the easy 

 erosion of the dolomite. The depression is used by the Har- 

 lem Railroad from a point just below Morrisani, northward 

 until it crosses into the drainage basin of the Croton River. The 

 Bronx, however, at a point, a half a mile or so below Williams 

 Bridge, 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 



