dried in which the natural angle of repose might be 60°, and in which
the percentage of water or aqueous matter when submerged might be 60%,
there would be an increase of pressure toward the bottom.

The writer does not know the exact nature of the experiments made at St.
George's Ferry by Mr. Goodrich, but he supposes they were measurements
of pressures on pistons through holes in the sheeting. He desires to
state again that he cannot regard such experiments as conclusive, and
believes that they are of comparative value only, as such experiments do
not measure in any large degree the pressure of the solid material but
only all or a portion of the so-called aqueous matter, that is, the
liquid and very fine material which flows with it. Thus it is well known
that, during the construction of the recent Hudson and North River
Tunnels, pressures were tested in the silt, some of which showed that
the silt exerted full hydrostatic pressure. At the same time, W.I. Aims,
M. Am. Soc. C. E., stated in a public lecture, and recently also to the
writer, that in 1890 he made some tests of the pressure of this silt in
normal air for the late W.R. Hutton, M. Am. Soc. C. E. A hole, 12 in.
square, was cut through the brickwork and the iron lining, just back of
the lock in the north tube (in normal air), and about 1000 ft. from the
New Jersey shore. It was found that the silt had become so firm that it
did not flow into the opening. Later, a 4-in. collar and piston were
built into the opening, and, during a period covering at least 3 months,
constant observations showed that no pressure came upon it; in fact, it
was stated that the piston was frequently worked back and forth to
induce pressure, but no response was obtained during all this period.
The conclusion must then be drawn that when construction, with its
attendant disturbance, has stopped, the solid material surrounding
structures tends to compact itself more or less, and solidify, according
as it is more or less porous, forming in many instances what may be