234 REPORTS ON INVESTIGATIONS AND PROJECTS. 



in the other the initial difiference of lo per cent in density was reduced to 

 one-fiftieth its original quantity. This tended strongly to confirm the strong 

 antecedent probability that the blowhole gases could be reabsorbed during the 

 rolling process, thanks to its long continued great pressure at a very high 

 temperature. 



The second line of inquiry disclosed what traces of blowholes remained in 

 the boiler-plate, by cutting very thin slices lengthwise and crosswise from 

 that plate, mirror-polishing them, and then bending them double in such a 

 way that any blowhole traces present ought to gape open like the cards of a 

 bent pack. Had there been no welding of blowholes, this bending should 

 have disclosed unwelded seams about 3.5 inches long and 1.3 inches wide. 

 In point of fact, the traces detected were so short as to indicate strongly that 

 a very great degree of welding had occurred, as seemed to the writer, though 

 not to all competent investigators, to be antecedently very probable. The 

 longest single trace was 0.07 inch long. Only one "string" of such traces 

 was found, and this was only 0.3 inch long. Further, the scantiness of these 

 relics of blowholes tends to show that the blowhole gases have been reab- 

 sorbed by the metal to a very great degree. Such relics of blowholes as 

 have persisted in most cases probably represent spots where the reabsorption 

 of the gas has become complete after the temperature has fallen too low to 

 permit welding, and the proper course to pursue may be found in prolonging 

 the exposure to a temperature above the welding-point, so as to complete the 

 reabsorption of gas while the metal is still weldable. 



Nichols, E. L., Cornell University, Ithaca, New York. Grant No. 631. Con- 

 tinuation of researches of phosphorescence and -fluorescence. (For pre- 

 vious reports see Year Books Nos. 4-8, inclusive.) $3,000 

 The following is a brief report of the progress of the work on fluores- 

 cence and phosphorescence by Prof. Ernest Merritt and the grantee, carried 

 on under grant No. 631 of the Carnegie Institution of Washington: 



( I ) Photographic Measurements: 



During the year 1909-10 much time has been spent in the development of 

 a strictly quantitative method for the photographic study of the spectra of 

 fluorescent and phosphorescent bodies. This will make it possible to extend 

 observations to bands in the violet and ultra-violet and also to study spectra 

 that are too weak for accurate spectrophotometric determination. For this 

 work a large quartz spectrograph and a wave-length spectrometer with 

 photographic accessories have been imported from Hilger. For the meas- 

 urement of negatives a special form of micro-comparator has been designed 

 and constructed. 



Throughout the year Dr. C. A. Pierce* has been engaged in the photo- 

 graphic study of phosphorescence spectra. Mr. H. E. Howe has tested the 

 proposed method of measurement as applied to the fluorescence spectrum of 



* Pierce, Physical Review, xxx, p. 663. 1910. 



