47$ METALLURGY OF1 CAST IRON.
difference in the relative strength of test bars was obtained for the tables, we give two examples seen on this page, as one method is necessary for a square bar and another for a round bar : The author could never perceive wherein the formulae used for figuring the strength per square inch, as advanced by our text books, etc. , had any bearing on the actual area of a test bar and the load at which it broke; in fact, if in 1901 a founder should send the area and tests of round and square test bars to recognized authorities on mathematics to have their strength per square inch computed, the chances are they would present such figures that he would be liable to wonder if present formulae for cast iron were not invented rather for the purpose of distorting facts or making figures lie than for furnishing true data. The author has referred to this subject on several occasions since he published the methods for computation shown in table
TABLE 99. — SQUARE BAR. TEST NO. 6. PAGE 460.
Area of bar.
1.002 in. x 1.002 in. — 1.004 square inches. Breaking" load. Area.
3,500 Ibs. -i- 1.004= 3>486 lbs. strength per sq. in.
ROUND BAR. TEST NO. 12. PAGE 460. Diameter. Diameter. Square of diameter.
1. 132 in. x i 132 in. = 1.281424 square inches. Square of diam. Decimal. Area.
1.281424 x .7854 — i. 006 square inches.
Breaking load. Area.
3,708 -f- 1.006 — 3,686 Ibs. strength per sq. in.
99, and was pleased to note that at the meeting of the American Society of Mechanical Engineers, St. Louis, May, 1896, Prof. C. H. Benjamin came out openly in a letter discussing the testing of cast iron and attacked the usual formulae for loaded beams asound burs..........................*fi$7 "