( 206 ) 
beautiful and picturesque natural feature, besides being of 
great geological significance. Its depth from the summits 
of the hills on both sides averages nearly 75 feet, and its 
sides below the foot-bridge at the mansion are nearly ver- 
tical rock faces. The hills on both sides are heavily wooded 
with hemlock spruce and other trees. In the upper part 
of the gorge the river flows slowly, being held back by the 
dam forming the waterfall at the mansion, and the ele- 
vation of its surface is only a few inches higher at the 
boulder bridge than it is at the fall; after plunging over the 
dam, however, the river runs in its unobstructed natural 
channel with all the appearance of a mountain stream, 
which at high water is exceedingly beautiful. 
22. North Meadows and River; Woods 
The Bronx River enters the northern end of the Garden 
from Williamsbridge and flows as a slow stream southward 
to the waterfall at the mansion, its surface being nearly 
level throughout this distance. It is spanned just inside 
the northern boundary of the Garden by a concrete-steel 
arched bridge with granite copings, which carries the main 
park driveway across it near the Bronx River Parkway 
entrance. The entire northern end of the Garden is formed 
of the flood plain of the Bronx River, consisting largely of 
grassy meadows and marshes which at average flow of the 
stream are several feet above its surface, but which at flood 
time are occasionally submerged for short periods, the whole 
valley being a very interesting illustration of the behavior 
of a small stream with a large watershed at and about its 
sources. Considerable areas of the marshy land have al- 
ready been reclaimed by filling, and by the lowering of the 
dam forming the waterfall at the mansion; the general 
plan contemplates a much further reduction in the amount 
of marshy ground, and a further lowering and deepening 
of the river by dredging, in order to take off freshets with 
greater rapidity. <A part of this flood-plain is occupied by 
the plantations of willows and poplars already described, 
