PHYSICS. 401 



because of the dis-registry between the sUp planes in adjoining grains, 

 the propagation of sHp across each of these boundaries de-crystaUizes 

 some of the metal there, and thus strengthens the boundary metal 

 progressively, so that though before deformation the boundaries are 

 paths of relatively low resistance, as deformation proceeds their resis- 

 tance increases progressively, till it soon exceeds that of the grain 

 bodies, with the result that rupture is trans-granular. 



5. The pro-eutectoid ferrite and cementite which form in gamma 

 iron in cooling through the transformation range are ejected to the 

 exterior of the grains. The process is such as to indicate that the 

 motive power for this ejection resides in the gamma iron itself and not 

 in the nature of the boundaries between the various grains. Under 

 proper conditions the whole surface of the mass becomes coated dur- 

 ing the cooling down through the transformation range with the pro- 

 eutectoid element. As such surfaces consist of random sections cut 

 across these crystallographic grains, it is evidently not the surface that 

 has attracted the pro-eutectoid element, but the gamma iron that has 

 expelled it. 



6. Experiments have been conducted on the formation of so-called 

 ghosts or bands abnormally rich in ferrite, which are injurious to steel, 

 and some of the conditions which bring about this ghost formation 

 have been shown. 



7. The hardening effect caused by cold deformation is very sUght 

 immediately after the deformation has occurred, but it increases both 

 with time and with gentle heating to about 300°, showing that the 

 effect of rest and heating, which had previously been known to apply 

 to the elastic limit, applies also to the hardness. 



8. In addition to confirming the results of previous observers, show- 

 ing that the Neumann lamellse or mechanical twins of alpha iron follow 

 the 211 trapezohedron, I find evidence that they also follow cubic 

 planes. 



9. The slip planes in alpha iron, instead of being octahedral, as has 

 hitherto been reported by various observers, follow these same planes 

 of the 211 trapezohedron. 



Lewis, E. P., University of California, Berkeley, California. Photographic 

 investigations of vacuum-tube spectra of gases and vapors. (For previous 

 reports see Year Books Nos. 3-7.) 



The last report from me was made in 1908 (concerning the observ^a- 

 tions with the quartz spectrograph taken in the Crocker echpse expedi- 

 tion in 1908). No call for a report has reached me in recent years, and 

 until two years ago there has been nothing to report. Four years of 

 close application to my duties as a member of the local board of educa- 

 tion, followed by a year of sabbatical leave, made these years barren, 

 for I had no trained assistant qualified to carry on the work under my 



