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RELATIVE   STRENGTH   OF   TEST   BARS.              477
being incorrect, insisting that a reform should be enacted in this field of mathematics. In his letter he expressed the opinion, as stated by the American Machinist, that the terms "modulus of elasticity," 'Ł elastic limit,'' etc:, were entirely out of place as applied to cast iron, and should not be used at all in connection with that material, and that the usually accepted formulae for strength of beams would not hold good for cast iron beams, as had been shown by tests made by himself for the committee.
The author trusts that the good work started at St. Louis will result, before many years, in our having some standard for computing the strength of cast iron that can be recognized as more practical or more correct than our present formulas for figuring different lengths and sizes of bars or loaded beams. It is as essential to have correctness in formulas for figuring the strength of cast iron as it is to have correct systems for casting and testing such grades of metal. (See
PaŁe 530-)
To any desiring to use larger bars than the one and one-eighth inch diameter shown in Table 99, and wishing to keep even figures as with a two-inch or three-inch area section,-as some may desire to do, the only difference would be to have the figures 1.596 or 1.955, as the case may be, replace the 1.128, which is the diameter of a bar equal to the area of a one-inch square bar. It may be well to mention at this point that the Riehle Bros, of Philadelphia and others now use the method for computing the strength of test bars shown in Table 99, page 476.    1.006      —      3,686 Ibs. strength per sq. in.