UNIFICATION OF METHODS IN TESTING MATERIALS. xIX 
is proportional to the work done upon the test~ piece per unit of 
volume. The values of c enable us to classify the various kinds 
of ductile materials upon their capacity of work, and the factors 
8 and X are determined in the ordinary testing of materials. If 
we adopt the English ton, and the inch as units in the place of 
the kilogramme and the metre, we may express Tetmaier’s 
coefficient in the following manner. Let § denote the tensile 
strength in tons per square inch, and let A denote the percentage 
of elongation measured on a length of 8”, then— 
c= BA 
represents the coefficient as before in inch tons per unit of volume. 
For thirty-two ton steel giving 20% elongation, the coefficient 
becomes 6:4, or we may use the coefficient to determine the elon- 
gation, having decided the tensile strength of the material before- 
hand. The author proposes to introduce the coefficient in his 
reports of tests in order to enable engineers to judge of the quality 
of materials when the strengths and elongations vary. In specify- 
ing the quality of steel, however, the upper limit of strength 
should always be stated in order to prevent the use of too great a 
percentage of carbon in the manufacture, but the lower limit need 
not be stated if either a coefficient of quality or the elongation be 
given. 
Tetmaier’s coefficient of quality was first adopted, on his recom- 
mendation, by the Swiss Government, about twelve years ago, it 
was afterwards adopted by the Austrian Government, and last 
year, also by the Committee of the American Society of Civil 
Engineers. It applies to compression and transverse tests as 
well as tension. 
This Committee of the American Society of Civil Engineers 
recommend for all grades of structural steel from 56000 to 74000 
pounds per square inch, i.e., 25 to 32°6 tons per square inch, 
Shall have the following elongations and reduction of area at 
fracture— 
