by insecure foundations, those which settle, his assertion, assuming it to be true, has but little weight.  It is not always possible to found an arch on rock.  Some settlement may be anticipated in almost every foundation.  As commonly applied, the elastic theory is based on the absolute fixity of the abutments, and the arch ring is made more slender because of this fixity.  The ordinary “row-of-blocks” method gives a stiffer arch ring and, consequently, greater security against settlement of foundations.

In 1904, two arches failed in Germany.  They were three-hinged masonry arches with metal hinges.  They appear to have gone down under the weight of theory.  If they had been made of stone blocks in the old-fashioned way, and had been calculated in the old-fashioned row-of-blocks method, a large amount of money would have been saved.  There is no good reason why an arch cannot be calculated as hinged ended and built with the arch ring anchored into the abutments.  The method of the equilibrium polygon is a safe, sane, and sound way to calculate an arch.  The monolithic method is a safe, sane, and sound way to build one.  People who spend money for arches do not care whether or not the fancy and fancied stresses of the mathematician are realized; they want a safe and lasting structure.

Of course, calculations can be made for shrinkage 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.