ge stresses and for
temperature stresses. They have about as much real meaning as
calculations for earth pressures behind a retaining wall. The danger
does not lie in making the calculations, but in the confidence which the
very making of them begets in their correctness. Based on such
confidence, factors of safety are sometimes worked out to the hundredth
of a unit.

Mr. Thacher is quite right in his assertion that stiff steel angles,
securely latticed together, and embedded in the concrete column, will
greatly increase its strength.

The theory of slabs supported on four sides is commonly accepted for
about the same reason as some other things. One author gives it, then
another copies it; then when several books have it, it becomes
authoritative. The theory found in most books and reports has no correct
basis. That worked out by Professor W.C. Unwin, to which the writer
referred, was shown by him to be wrong.[T] An important English report
gave publicity and much space to this erroneous solution. Messrs. Marsh
and Dunn, in their book on reinforced concrete, give several pages to
it.

In referring to the effect of initial stress, Mr. Myers cites the case
of blocks and says, "Whatever initial stress exists in the concrete due
to this process of setting exists also in these blocks when they are
tested." However, the presence of steel in beams and columns puts
internal stresses in reinforced concrete, which do not exist in an
isolated block of plain concrete.

Mr. Meem, while he states that he disagrees with the writer in one
essential point, says of that point, "In the ordinary way in which these
rods are used, they have no practical value." The paper is meant to be a
criticism of the ordinary way in which reinforced concrete is used.

While Mr. Meem's formula for a reinforced concrete beam is simple and
much like that which the writer would use, he errs in making the moment
of the stress in the steel about the neutral axis equal to the moment of
that in the concrete about the same axis. The actual amount of the
tension in the steel should equal the compression in the concrete, but
there is no principle of mechanics that requires equality of the moments
about the neutral axis. The moment in the beam is, therefore, the
product of the stress in steel or concrete and the effective depth of
the beam, the latter being the depth from the steel up to a point
one-sixth of the depth of the concrete beam from the top. This i