has handled this subject, his paper should be labeled "Dangerous for
Beginners," especially as he is an engineer of great practical
experience; if he were not, comparatively little attention would be paid
to his statements. The paper is dangerous because many will read only
portions of it, or will not read it thoroughly. For instance, at the
beginning, the author cites several experiments in which considerable
force is required to start the lifting of a weight or plunger in sand
and water and much less after the start. This reminds the speaker of the
time when, as a schoolboy, he tried to pick up stones from the bottom of
the river and was told that the "suction" was caused by atmospheric
pressure.

The inference is that tunnels, etc., in sand, etc., are not in any
danger of rising, even though they are lighter than water. Toward the
end of the paper, however, the author states that tunnels should be
weighted, but he rather spoils this by stating that they should be
weighted only enough to overcome the actual water pressure, that is,
between the voids of the sand. It seems to the speaker that the only
really safe way is to make the tunnel at least as heavy as the water
displaced in order to prevent it from coming up, and to take other
measures to prevent it from going down. The City of Toronto, Canada,
formerly pumped its water supply through a 6-ft. iron pipe, buried in
the sand under Toronto Bay and then under Toronto Island, with an intake
in the deep water of the lake. During a storm a mass of seaweed, etc.,
was washed against the intake, completely blocking it, and although the
man at the pumping station knew that something was wrong, he continued
to pump until the water was drawn out of the pipe, with the result that
about half a mile of the conduit started to rise and then broke at
several places, thus allowing it to fill with water. Eventually, the
city went down to bed-rock under the Bay for its water tunnel.