The course of the Bronx immediately below the mill is said to have

been formerly changed by a large beaver dam, which those industrious

animals had erected near die foot of Mr. Underbill's garden. Beaver

Pond lies directly north of the mill. Beavers were once very common

on the Bronx and neighboring streams, and afford an excellent example

of animals not only sociable by dwelling near each other, but by joining

in a work which was for the benefit of the community. Water was as

needful for the Beaver as for the miller; and it is a very curious fact that

long before miller's ever invented dams, or before men ever learned to

grind corn, the beaver knew how to make a dam and to insure itself a

constant supply of water. The dam was by no means placed at random

in the stream, just where a few logs may have happened to lodge -- but

it was set exactly where it was wanted, and it was made so as to suit

the force of the current ; in those places where the stream runs slowly

the dam was carried straight across the river, but in those where the

water had much power the barrier was made in a convex shape so as to

resist the force of the rushing water. The power of the stream could,

therefore, always be inferred from the shape of the dam which the beavers had built across it. Some of these structures were of great size,

measuring two or three hundred yards in length and ten or twelve

feet in thickness, and their form exactly corresponded with the force

of the stream. They made their houses close to the water and

communicated with them by means of subterranean passages, one

entrance of which passed into the house, or lodge -- as it was technically named -- and the other into the water, so far below the surface that it could not be closed by ice.