138 PROF. W. E. DALBY: ON ELASTIC PROPERTIES AND EXTENSION OF METALS. 
The agreement between the limit of proportionality shown on the diagram, namely, 
11‘45 tons per sq. inch, and the fatigue limit found by quite a different test, is 
remarkably close. 
Again, if this result could be generalized, it could be asserted that every load 
elastic extension diagram shows the positive value of the fatigue limit. The long 
and tedious experiments with alternating loads would be unnecessary. Such a 
conclusion requires comparison to be made over a wide range of material. This, 
therefore, is a promising field of research. 
These brief notes of results and inferences show what a wide range of information 
lies before the engineer and metallurgist if he has before him a pair of diagrams, the 
one showing the complete load extension curve from zero to fracture, the other a load 
elastic extension looped diagram on a large extension scale. 
The matter incorporated in this paper has been selected from experiments extending 
over several years. I desire to express my acknowledgments and thanks to 
Prof. Witchell for his help, and in particular for the assistance he gave me in 
reducing the looped diagram to the curves of Sheet 1. 
I also desire to acknowledge the assistance of Mr. Orr for the skill and care with 
which he has drawn the curves on Sheet 1 and figures 19-23 from the photographic 
plates. 
PRESENTED 
40CJ. !j20 
