PHYSICS. 377 



estimate the degree of success, except to state that at least a partial 

 success is certain. No attempt has thus far been made to study 

 stream flow, as that portion of the investigation is intended to be 

 based on more information in regard to evaporation than is now 

 available. 



Howe, Henry M., Columbia University, New York, N. Y, Investigation in- 

 to the heat treatment of steel. (For previous reports see Year Books 6-12.) 



While most of the year has been spent in collating and digesting the 

 existing information on the subjects in hand, with a view to publication 

 in a treatise of which the first volume is now nearly ready, a consider- 

 able amount of direct experimental work has been done. This is 

 recapitulated as follows: 



1. Overstrain. 



Steel is a conglomerate of different structural constituents. The 

 relative movements of these constituents and their general behavior 

 during plastic deformation have been studied, by means of the changes 

 which this deformation brings about in their arrangement and the 

 simultaneous changes in hardness and density. The deformation has 

 been brought about in some cases by tensile rupture, and in others 

 by punching. In addition to many other inferences of detail, it is 

 found that the polish which the upper part of a vertically punched hole 

 shows is due to the radial pressure of this part of the metal against 

 the entering punch, after its end has passed beyond this part. The 

 metal combines with a degree of viscosity which results in the retention 

 of very great internal pressure in the region near where the punch is 

 forcing its way, a degree of mobility which enables this pressure to 

 act in every direction. Among these directions is one radially and 

 towards the punch. This component of the pressure acts like the pres- 

 sure in a hydraulic cylinder which tightens the packing about the 

 plunger, and thus forces the metal in the already punched upper part 

 of the hole against the still descending punch so firmly that the move- 

 ment of the punch now causes the high polish observed. 



Further, though the lamellae of pearlitic cementite are extremely 

 brittle, they may be crumpled into W and V shapes by the deformation 

 and still retain continuity. This may be referred to their thinness, as 

 thin enough glass hairs can be bent far without breaking. 



Pearlite masses consist of alternate lamellae of the very ductile plastic 

 ferrite with very brittle cementite. When they are elongated parallel 

 to the stratification the cementite lamellae simplj^ break up into shorter 

 fragments; when they are shortened parallel to the stratification their 

 arrangement changes, militarily speaking, from close order in line to 

 open order en echelon. 



From the fact that the effects of repetitive overstrain are extremely 

 anisotropic, it has been currently inferred that those of single applica- 

 tions of overstrain also are; but my experiments show that the increase 



