t to
the exterior of the tower just below the tank, thus showing that
insurance against leakage is actually provided by the plastered interior
surfaces and not by the sheet-metal tank, and, for this reason, ordinary
deformed rod reinforcement, in the writer's opinion, would have proved
cheaper and better, and more in line with other parts of the
reinforcement.

Mr. Kempkey states:

"Before filling, the inside of the tank was given a plaster coat,
consisting of 1 part cement to 1-3/4 parts of fine sand. This
proved to be insufficient to prevent leakage, the water seeping
through the dome and appearing on the outside of the structure
along the line of the bottom of the rings. Three more coats were
then applied over the entire tank, and two additional ones over the
dome and about 8 ft. up on the sides, and, except for one or two
small spots which show just a sign of moisture, the tank is
perfectly tight."

This substantiates the writer's contention that water-tightness was
actually obtained by a liberal use of cement plaster, which would also
have been true had the reinforcement been rods.

As a further comment, it might be stated that a water-tight concrete for
the tank could have been obtained by adding from 8 to 10% of hydrated
lime to the 1:2:4 mixture. This seems advisable in all cases where a
water-tight concrete is necessary. The interior plastering could then
have been done as a further precaution.

A. KEMPKEY, JR., JUN. AM. SOC. C. E. (by letter).--Mr. Couchot's
statement, that the 3-in. inside and outside sheets forming the tank
casing do not act together, is quite true, and it was not expected that
they would, other than to protect the steel and form an ornamental
covering for it.

There is certainly adhesion between concrete and steel, even though the
steel be in the form of a thin shell, and in a structure of this kind
where the steel is designed, with a low unit stress, to take all the
strain, and where the load is at all times quiescent, it is difficult to
see how this bond can be destroyed; the writer feels no concern on this
score.

Mr. Markwart's statement, that the steel tank enclosed within the
concrete of the upper cylinder, presumably to provide a water-tight
tower, will not fulfill this latter requirement, is not true, as shown
by the statement in the paper that the only leakage which occurred was
that which passed under the tank, the entire re