1896.] NEW YORK ACADEMY OF SCIENCES. 19 



this gorge and then reaching more open country, with a rocky 

 fall at Bronxclale and another at West Farms, it makes its way 

 to the sound. 



Just below Williams Bridge it (lows against the west side of 

 the valley, and immediately alongside of the railroad. It then 

 leaves this and passes diagonally to the south, being diverted 

 in part by a broad and flat terrace of coarse, rounded, cobble 

 stones, up to one foot or more in diameter and with compara- 

 tivel}' little sand intermingled. The cobbles have been exposed 

 for a thickness of at least 20 feet, b}- the excavations, for the 

 new Bronx River sewer. The river passes along the foot of 

 the ridge on the east side and divides the gravel terrace in two, 

 so as to leave a small remnant on the eastern gneisses. It then 

 runs against a westerly spur of the ridge and cuts through it, in 

 a pronounced gorge, diagonally across the foliation of the rock, 

 which is a hard micaceous gneiss. 



From the entrance to the gorge a swampy depression extends 

 Avestward to the railroad and has all the characteristics of an 

 fibandoned channel. The railroad has crossed it by an embank- 

 ment and culvert. Just east of the culvert there is gneiss but a 

 few feet below the soil, and at this point the old stream evidently 

 surmounted a reef. The depression continues southward just 

 west of the track, as far as Morrisania ; it is then crossed by the 

 track, which traversing a low divide into the next limestone 

 valley to the west, follows this to Mott Haven, and then passes 

 over the river to Manhattan Island. The depression runs south 

 from Morrisania and enters the East River opposite Randalls 

 Island. In all its extent there is no natural barrier, although 

 many streets have been filled in across it. At its highest point 

 near Bedford Park Station, it is not more than ten or twelve feet 

 iibove the present surface of the Bronx river at the gorge, prob- 

 abl}^ less. The river is about 5 feet deep at this point. All 

 these relations are shown on the accompanying map, which is 

 reproduced from the Harlem sheet of the United States Geolog- 

 ical Survey . The excess of streets and I'ailways on the original 

 map mask the contours which can only be traced on it with diffi- 

 cult3-. Accordingly everything but the contours, the river 

 and one or two railway- lines have been omitted in redrawing, 

 and for the same reason no attempt has been made to put in the 

 geology. The authorities of the Botanical Garden have a map 

 of its area on a very large scale and with 5-ft. contours. The 

 writer has used this also in the preparation of the paper, al- 

 though all the material points are well illustrated on the smaller 

 scale. 



By observing the map it will be seen that both the river and 



