TREATMENT OF MANUFACTURED IRON AND STEEL. OFT 
became to be considered the correct length for a specimen of that 
material to be put under tensile stress. 
Some people do not understand that the length of the specimen 
is of the greatest importance in recording the extension, and omit 
to state the length in which the elongations have been taken. 
To obtain some idea of the difference in the percentages of 
elongation with specimens of various lengths, the author had 
samples cut from two bars of steel. From each of these bars, 
pieces were cut of suitable lengths to enable specimens to be turned 
from them, having lengths under tension of ten, eight, six, five 
and two inches, and the results are attached hereto. ach of 
the specimens were marked off in inches, and the percentage of 
elongation was taken in the total length and also in the two 
inches at the point of fracture, as per sketch. 
These results have been of use upon many occasions, but they 
can only be considered to give general information. To obtain 
very accurate and more reliable data, a series of such tests should 
be carried out; but, as indicated, they have proved of service 
where an elongation in a lengthof, say five inches, has been recorded, 
and it has been desired to obtain some idea of the elongation of 
similar metal in a length of eight inches. 
The author would suggest for the consideration of Professor 
Warren, who has such admirable testing plant at the University, 
the advisability of carrying out a number of experiments in this 
‘direction. 
It has been proved that when specimens of the same material 
are being tested, the percentage of elongation is exactly the same 
until the maximum load the sample will carry has been reached, 
no matter what the length may be. They then begin to fail and 
generally elongate at one point. It is due to this local elongation 
_ that the recorded results vary so much in the different lengths 
under stress. 
It will be noted that. the breaking strength of the specimens 
_ two inches long, was greater in both cases than in the other samples 
