1887.] on Genesis of the Elements. 43 



residual glow is so short that, with the highest speed of which the 

 instrument is capable, you see no light whatever. In contrast I now 

 put in a compound of the earth strontia. This also glows with a rich 

 blue colour, showing in the spectroscope a continuous spectrum with 

 a great concentration of light in the blue and violet. In the phos- 

 phoroscope the colour of the glow is bright green, showing in the 

 spectroscope a continuous spectrum, with the red and blue ends cut off. 

 Alumina in the radiant matter tube glows with a rich crimson 

 light. I will put some rubies — a crystalline form of alumina — in the 

 phosphoroscope. Here the persistence of luminosity is so great that 

 the red light is visible with the slowest speed, and with a high 

 velocity the residual glow is nearly as strong as when the rubies are 

 out of the instrument. Shakespeare, who is supposed to have 

 mastered all knowledge, had he seen these rubies could hardly 

 have described them more precisely than in the lines from ' Julius 

 Caesar ' : — 



"... with unnumbered sparks 

 They are all fire, and every one doth shine." 



Another distinctive phenomenon is that the earths of one group, 

 yttrium and samarium, when submitted to the induction discharge in 

 vacuo, yield discontinuous spectra. 



These spectra are extremely complicated and change in their 

 details in a puzzling manner. For many years I have persistently 

 groped on in almost hopeless endeavour to get a clue to the meaning 

 which I felt convinced was locked up in these systems of bands and 

 lines. It was impossible to divest myself of the conviction that I was 

 ].ooking at a series of autograph inscriptions from the molecular world, 

 evidently of intense interest, but written in a strange and baffling 

 tongue. For a long time all attempts to decipher these mysterious 

 signs were fruitless. 



The meaning of the strongly-marked symbolic lines had first to 

 be ascertained. After continued efforts I had to be content with 

 roughly translating one group of coloured symbols as " yttrium " and 

 another group as " samarium," disregarding the fainter lines, shadows, 

 and wings frequently common to both. Constant practice in the 

 decipherment has now given me fuller insight into what I may call 

 the grammar of these hieroglyphic inscriptions. Every line and 

 shadow of a line, each faint wing attached to a strong band, and every 

 variation in intensity of the shadows and wings among themselves, 

 has now a definite meaning which can be translated into the common 

 symbolism of chemistry. 



This leads us to what I may call the history of yttrium. Twelve 

 months ago the name yttrium conveyed to all chemists a perfectly 

 definite meaning. It was supposed to be an elementary or simple 

 body, having a fixed atomic weight, 88 • 9, and its principal properties 

 had been duly determined. Its phosphorescent spectrum gave a 

 definite system of coloured bands, such as you see in the drawing 



