and haphazard guesses are made as to how much
of the floor slab may be considered in the compression flange. If a
fraction of this mental energy were directed toward a logical analysis
of the shear and gripping value of the stem of the T-beam, it would be
found that, when the stem is given its proper width, little, if any, of
the floor slab will have to be counted in the compression flange, for
the width of concrete which will grip the rods properly will take the
compression incident to their stress.

The tenth point concerns elaborate theories and formulas for beams and
slabs. Formulas are commonly given with 25 or 30 constants and variables
to be estimated and guessed at, and are based on assumptions which are
inaccurate and untrue. One of these assumptions is that the concrete is
initially unstressed. This is quite out of reason, for the shrinkage of
the concrete on hardening puts stress in both concrete and steel. One of
the coefficients of the formulas is that of the elasticity of the
concrete. No more variable property of concrete is known than its
coefficient of elasticity, which may vary from 1,000,000 to 5,000,000
or 6,000,000; it varies with the intensity of stress, with the kind of
aggregate used, with the amount of water used in mixing, and with the
atmospheric condition during setting. The unknown coefficient of
elasticity of concrete and the non-existent condition of no initial
stress, vitiate entirely formulas supported by these two props.

Here again destructive criticism would be vicious if these mathematical
gymnasts were giving the best or only solution which present knowledge
could produce, or if the critic did not point out a substitute. The
substitute is so simple of application, in such agreement with
experiments, and so logical in its derivation, that it is surprising
that it has not been generally adopted. The neutral axis of reinforced
concrete beams under safe loads is near the middle of the depth of the
beams. If, in all cases, it be taken at the middle of the depth of the
concrete beam, and if variation of intensity of stress in the concrete
be taken as uniform from this neutral axis up, the formula for the
resisting moment of a reinforced concrete beam becomes extremely simple
and no more complex than that for a rectangular wooden beam.

The eleventh point concerns complex formulas for chimneys. It is a
simple matter to find the tensile stress in that part of a plain
concrete chimney betw