214 Prof. E. L. Hancock : Effect of Combined 
For some of the glower current may be supposed to pass 
around through the particle, and there would then be, on 
account of the electrolytic character of the glower conduction, 
oxygen given off where the current enters, and absorbed 
where it leaves, the metal, and thus the forces of cohesion 
on the two sides be rendered unequal. The result would be 
a couple tending to turn the particle or globule over in one 
direction. Somewhat similar conditions would exist in the 
case of a particle of oxide placed on the glower, as all oxides 
conduct more or less at these temperatures. It is not evident 
what determines the direction in which a particle will move, 
nor is there any apparent reason for the curious grouping 
with respect to atomic weights, of the metals moving with, 
and moving against the current, which grouping may indeed 
have little or nothing to do with the fundamental cause of 
the motion . A possible explanation of this grouping, however, 
might be based on the fact that the metals of higher atomic 
weights which can be tested in this way, are the less readily 
oxidizable ones which will form globules when molten, while 
those of lower atomic weights are more readily oxidized and 
flux with the glower wdien melted. That different metals 
should, under similar conditions, move oppositely is, from 
the view just given, not surprising. There are, however, 
several exceptions (for example, tantalum and barium, which 
are readily oxidizable) which are against this latter way of 
looking at the matter. 
Physical Laboratory, University of Wisconsin, 
June 1907. 
XVIII. Effect of Combined Stresses on the Elastic Properties 
of Steel. By E. L. Hancock, Assistant Prof essor of Applied 
Mechanics, Purdue University, La Fayette, Ind.* 
[Plates X. & XL] 
DURING the past year tests have been continued under 
the direction of the writer to determine the effect of 
combined stresses on the elastic properties of steel. These 
tests form a part of the general plan for such tests carried 
on in the laboratory for testing materials of Purdue University 
(see Proceedings Amer. Soc. Testing Materials, vol. v. p. 179, 
and vol. vi. p. 295). The tests already made and reported to 
this Society have included tests in tension and compression 
while the material was under torsion. The tests reported in 
this paper were made by first subjecting the material to 
tension or compression, and then while under such stress 
applying certain increments of torsion. In the tension-torsion 
* Communicated by the Author, having been read at the meeting of 
the American Society for Testing Materials on June 20, 1907. 
