Eleventh Point.—­Calculations for chimneys are somewhat complex, but are better and safer than rule-of-thumb methods.

Twelfth Point.—­Deflection is not very important.

Thirteenth Point.—­The conclusion of the Austrian Society of Engineers and Architects, after numerous experiments, was that the elastic theory of the arch is the only true theory.  No arch designed by the elastic theory was ever known to fail, unless on account of insecure foundations, therefore engineers can continue to use it with confidence and safety.

Fourteenth Point.—­Calculations for temperature stresses, as per theory, are undoubtedly correct for the variations in temperature assumed.  Similar calculations can also be made for shrinkage stresses, if desired.  This will give a much better idea of the stresses to be provided for, than no calculations at all.

Fifteenth Point.—­Experiments show that slender longitudinal rods, poorly supported, and embedded in a concrete column, add little or nothing to its strength; but stiff steel angles, securely latticed together, and embedded in the concrete column, will greatly increase its strength, and this construction is considered the most desirable when the size of the column has to be reduced to a minimum.

Sixteenth Point.—­The commonly accepted theory of slabs supported on four sides can be correctly applied to reinforced concrete slabs, as it is only a question of providing for certain moments in the slab.  This theory shows that unless the slab is square, or nearly so, nothing is to be gained by such construction.

C.A.P.  TURNER, M. AM.  SOC.  C. E. (by letter).—­Mr. Godfrey has expressed his opinion on many questions in regard to concrete construction, but he has adduced no clean-cut statement of fact or tests, in support of his views, which will give them any weight whatever with the practical matter-of-fact builder.

The usual rules of criticism place the burden of proof on the critic.  Mr. Godfrey states that if his personal opinions are in error, it should be easy to prove them to be so, and seems to expect that the busy practical constructor will take sufficient interest in them to spend the time to write a treatise on the subject in order to place him right in the matter.

The writer will confine his discussion to only a few points of the many on which he disagrees with Mr. Godfrey.

First, regarding stirrups:  These may be placed in the beam so as to be of little practical value.  They were so placed in the majority of the tests made at the University of Illinois.  Such stirrups differ widely in value from those used by Hennebique and other first-class constructors.

Mr. Godfrey’s idea is that the entire pull of the main reinforcing rod should be taken up apparently at the end.  When one frequently sees slabs tested, in which the steel breaks at the center, with no end anchorage whatever for the rods, the soundness of Mr. Godfrey’s position may be questioned.