2l6 REPORTS OF INVESTIGATIONS AND PROJECTS. 



Professor Howe's investigations resulted in the following conclusions : 



Though very large ingots, 30 inches or more across, are subject to very 

 serious segregation, yet within the limits of 2.25 inches square and 16 inches 

 square the influence of ingot-size is not constant, so that the degree of segre- 

 gation was not greater in his large 16-inch square ingots than in his smaller 

 or even much smaller ones. Large size ought directly to increase segrega- 

 tion ; that which offsets this direct effect is, he explains, the greater quietness, 

 and especially the consequent greater opportunity for surfusion, to which 

 large size leads, essentially by lessening the convection currents. Quietness, 

 and especially surfusion, oppose segregation by diverting the course of solid- 

 ification from the concentric or onion-like type to the landlocking type, in 

 which far-outshooting pine-tree crystals form and landlock part of the molten 

 mother metal, thereby impeding that centripetal travel which is the essence 

 of segregation. A practical inference from this theory is that, in order to 

 lessen segregation, the ingots while solidifying should be kept as quiet and 

 cooled as slowly as practicable, so that quiet and surfusion may be favored. 



The net effect of the rate of cooling is not constant, even in sign, for like 

 reasons. 



The most enriched spot usually lies in the axis of the ingot, at a distance 

 from the top of between 6 and 28 per cent of the ingot's length. The most 

 impoverished part is probably rarely, if ever, axial. 



The enrichment in phosphorus and sulphur seems to be parallel with that 

 in carbon, so that the isophoses and isotheis (lines of equal phosphorus and 

 equal sulphur) are parallel with the isocarbs. 



On a general average of many cases, the maximum enrichment in phos- 

 phorus is about twice, and that in sulphur is about thrice, that in carbon, but 

 in individual cases the ratio of enrichment in any one of these three elements 

 to that in either of the others varies widely. Unusual freedom from sulphur 

 and phosphorus does not appear to restrain the segregation of carbon, but 

 rather to increase it, if anything. 



Professor Howe is not yet prepared to report on the degree of enrichment 

 and the degree of homogeneousness in the remainder of the ingot after 

 discarding certain definite percentages of its upper part, nor on how the 

 richness in carbon influences segregation of that element. 



Lewis, E. Percival, University of California, Berkeley, CaUfomia. Grant 

 No. 150. Photographic investigations of vacuum-tube spectra of gases 

 and vapors. (For previous reports see Year Book No. 3, p. 128; Year 

 Book No. 4, p. 253, and Year Book No. 5, p. 227.) $500. 



The available time of the writer was spent during the past year in securing 

 a number of photographs of the spectra of the haloid compounds of mercury 

 and of the nitrogen oxides, with a view to an extensive study of the ultra- 



