286 W. H. WARREN AND 8S, H. BARRACLOUGH. 
In the above table No. 1 is not included, as the dimensions 
of the test piece differed altogether from those of the other tests. 
Nos. 41 — 36 were tested without any re-heating or re-stressing, 
Nos. 3 and 31 were tested in air; the mean value of the two 
tests is indicated on the diagram. The remaining four, Nos. 7 — 
4, were first stressed beyond the elastic limit, then their temper- 
ature was brought back to the normal, then they were re-heated 
{or cooled) and stressed to the breaking point. They are not 
shown in the diagram, but it will be found that they confirm 
fairly the position of the curve as shown. 
It is evident that, at least within the temperature range covered 
by the tests, the tenacity may satisfactorily be represented by @ 
straight line curve whose equation is approximately 
J = 32000 - 21¢ 
where f is the ultimate strength in Ibs. per square inch, at & 
temperature ¢? F. Prof. Unwin states' that he has found approxi- 
mately that 
f = 33,150 - -03136 (¢- 60)? 
but as the data upon which the equation is based are not supplied, 
no comparison is possible. The well known experiments made by 
a Committee of the Franklin Institute? between the years 1832 
and 1837 embfaced a range of temperature of from 100° to 1100°F., 
and the results obtained, although somewhat irregular, may be 
approximately represented by a straight line curve, a portion of 
which is shown in Fig. 3, for purposes of comparison. The 
rate of decrease of tenacity with increase of temperature does not 
differ greatly from that obtained in the present series of tests, 
although the absolute tenacity of the material was slightly greater. 
Evidently the straight line curve if continued, will cut the axis 
of temperature at a point some 500° below the melting point of 
“a Slate oe Machine ‘pak Part I a V7. “Te the equation given 
above, the stress is altered from tons per square inch, as used by Prof. 
Unwin, to lbs. per square inch, 
2 The original communication not being available, use has been made 
of the results as quoted by Prof. Thurston in Alloys, Brasses and Bronses, 
Pt. 111. 
