successful plan was as follows:

On the ground floor of the building, on a level with the street, was a
kitchen containing a fire-place, at a stove connected with which the
prisoners inhabiting the rooms above did their cooking. Beneath this
floor was a basement, one of the rooms which was used as a store-room.
This store-room was under the hospital and next to the street, and
though not directly under the kitchen, was so located that it was
possible to reach it by digging downward and rearward through the
masonry work of the chimney. From this basement room it was proposed to
construct a tunnel under the street to a point beneath a shed, connected
with a brick block upon the opposite side, and from this place to pass
into the street in the guise of citizens. A knowledge of this plan was
confided to about twenty-five, and nothing was known of the proceedings
by the others until two or three days before the escape. A table knife,
chisel, and spittoon were secured for working tools, when operations
commenced. Sufficient of the masonry was removed from the fire-place to
admit the passage of a man through a diagonal cut to the store-room
below; and an excavation was then made through the foundation wall
toward the street, and the construction of the tunnel proceeded night by
night. But two persons could work at the same time. One would enter the
hole with his tools and a small tallow candle, dragging the spittoon
after him attached to a string. The other would fan air into the passage
with his hat, and with another string would draw out the novel dirt car
when loaded, concealing its contents beneath the straw and rubbish of
the cellar. Each morning before daylight the working party returned to
their rooms, after carefully closing the mouth of the tunnel, and
skillfully replacing the bricks in the chimney.

An error occurred during the prosecution of this work that nearly proved
fatal to the enterprise. After a sufficient distance was supposed to
have been made, an excavation was commenced to reach the top of the
ground. The person working, carefully felt his way upward, when suddenly
a small amount of the top earth fell in, and through this he could
plainly see two sentinels apparently looking at him. One said to the
other, "I have been hearing a strange noise in the ground there!" After
listening a short time, the other replied that it was "nothing but
rats." The working party had not been seen. After consultation, this