608 



SCIENCE. 



[N. S. Vol. VIII. No. 201. 



and internal motions of tlie molecules 

 locked up in quiescent air at ordinai-y pres- 

 sure and temperature is about 140,000 foot- 

 pounds in each cubic yard of air. Accord- 

 ingly the quiet air withia a room 12 feet 

 high, IS feet wide and 22 feet long contains 

 energy enough to propel a one-horse engine 

 for more than twelve hours. The store 

 drawn upon naturally by uranium and 

 other heavy atoms only awaits the touch of 

 the magic wand of Science to enable the 

 twentieth century to cast into the shade the 

 marvels of the nineteenth. 



Whilst placing before you the labors and 

 achievements of my comrades in science I 

 seize this chance of telling you of engrossing 

 work of my own on the fractionation of 

 yttria to which for the last eighteen years 

 I have given ceaseless attention. In 1883, 

 under the title of ' Radiant Matter Spectros- 

 copy,' I described a new series of spectra 

 produced by passing the phosphorescent 

 glow of yttria, under molecular bombard- 

 ment in vacuo, through a train of prisms. 

 The visible spectra in time gave up their 

 secrets, and were duly embalmed in the 

 Philosophical Iransadions. At the Birming- 

 ham meeting of the British Association in 

 1886 I brought the subject before the Chem- 

 ical Section, of which I had the honor to be 

 President. The results led to many specu- 

 lations on the probable origin of all the ele- 

 mentary bodies — speculations that for the 

 moment I must waive in favor of experi- 

 mental facts. 



There still remained for spectroscopic ex- 

 amination a long tempting stretch of un- 

 known ultra-violet light, of which the ex- 

 ploration gave me no rest. But I will not 

 now enter into details of the quest of un- 

 known lines. Large quartz prisms, lenses 

 and condensers, specially sensitized photo- 

 graphic films capable of dealing with the 

 necessary small amount of radiation given 

 by feebly phosphorescing substances,* and, 

 *In this connection I am glad to acknowledge my 



above all, tireless patience in collating and 

 interpreting results, have all played their 

 part. Although the research is incomplete, 

 I am able to announce that among the 

 groups of rare earths giving phosphorescent 

 spectra in the visible region there are others 

 giving well-defined groups of bands which 

 can only be recorded photographically. I 

 have detected and mapped no less than six 

 such groups extending to /. 3060. 



Without enlarging on diflBculties, I will 

 give a brief oiitline of the investigation. 

 Starting with a large quantity of a group 

 of the rare earths in a state of considerable 

 l^urity, a particular method of fractionation 

 is applied, splitting the earths into a series 

 of fractions differing but slightly from each 

 other. Each of these fractions, phosphor- 

 escing in vacuo, is arranged in the spectro- 

 graph; and a record of its spectrum photo- 

 graphed upon a specially prepared sensitive 

 film. 



In this way, with different groups of rare 

 earths, the several invisible bands were re- 

 corded—some moderately strong, others ex- 

 exceedingly faint. Selecting a portion giv- 

 ing a definite set of bands, new methods of 

 fractionation were applied, constantly pho- 

 tographing and measuring the spectrum of 

 each fraction. Sometimes many weeks of 

 hard experiment failed to produce any sep- 

 aration, and then a new method of splitting 

 up was devised and applied. By unremit- 

 ting work — the solvent of most difficulties — 

 eventually it was possible to split up the 

 series of bands into various groups. Then, 

 taking a group which seemed to offer possi- 

 bilities of reasonably quick result, one 

 method after another of chemical attack 

 was adopted, with the ultimate result of 

 freeing the group from its accompanying 



indebtedness to Dr. Schumann, of Leipzig, for valuable 

 suggestions and detail ot his own apparatus, by means 

 of which he has produced some unique records of me- 

 tallic and gaseous spectra of lines of short wave- 

 length. 



