ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 615 



determiuations of the elastic limit of a series of pure metals were made, 

 while values for the surface tension of the amorphous material, based 

 upon measurements of the surface tension of the molten metal at its 

 melting-point, are deduced. Applying; these results in the above 

 equation, values are obtained for the thickness of the intercrystalline 

 films in the various pure metals examined. An apphcation of the 

 theory is illustrated by a study of a steel shaft which had been drasti- 

 cally over-annealed and showed very low elasticity. Samples of the 

 same steel when heat-treated by (1) normalizing at 850° C, (2) heating 

 to 850° C, quenching in oil and tempering at 350° C, showed similar 

 elastic limits, each much higher than that of the over-annealed sample. 

 Photomicrographs of the steel in the three states are given, showing a 

 large crystal size for the over-annealed and a much smaller and about 

 equal crystal size for the two other samples. The calculated thickness 

 of amorphous film is four times greater in the over-annealed sample 

 than in the two others, and its low elasticity is readily understood, 

 since the thicker the film the lower the magnitude of the surface 

 tension forces. The tensile strength of the three samples was of the 

 same order. The factors governing this property depend on the 

 crystals themselves, and not, as in the case of the elastic limit, on 

 the nature and extent of the intercrystalline junctions. 



