. The interpretation of radium and the structure of the atom . di-tion allows of a practically unlimited number of spin-thariscopes to be made out of an almost invisiblequantity of radium bromide. The amount of radium ineach instrument is absolutely unweighable and needle, A, is made to touch a tiny phial which oncecontained radium, and is then mounted (Figs. 10, and 11facing p. 35) centrally in a little brass tube, the sizeof a small reel of cotton, at the bottom of which is a THE SPINTHARISCOPE 43 phosphorescent screen, B, coated with zinc the other end of the tube is
. The interpretation of radium and the structure of the atom . di-tion allows of a practically unlimited number of spin-thariscopes to be made out of an almost invisiblequantity of radium bromide. The amount of radium ineach instrument is absolutely unweighable and needle, A, is made to touch a tiny phial which oncecontained radium, and is then mounted (Figs. 10, and 11facing p. 35) centrally in a little brass tube, the sizeof a small reel of cotton, at the bottom of which is a THE SPINTHARISCOPE 43 phosphorescent screen, B, coated with zinc the other end of the tube is a lens, C, for magnifjdngthe screen and, by means of a little screw, D, outside,the needle point may be moved nearer to or away fromthe screen. If now in a dark room the screen is through the lens, it will be seen to be luminous,and this luminosity can be concentrated or spread outby screwing the needle point nearer to or farther fromthe screen. After the eye has become used to the dark-ness it will be seen that the luminosity is not just a quiet. Fig. 10. continuous glow. The hght, like that of the planetarynebulae, has been resolved and shows resembles most nearly a shower of shooting momentary flashes of light or scintillations, toonumerous at any instant to count, are appearing and dis-appearing in the field of vision. These flashes are causedby the a-particles of radium. This minute insignifi-cant trace of radium is positively belching forth a-particles. It seems incredible that the incessant bom-bardment of the screen can be caused by such an in-finitesimal amount of radium. Yet so it is, and in amonths time, if the instrument is re-examined, it will 44 RAYS OF RADIOACTIVE SUBSTANCES be found that the scintillations are as numerous and asbrilliant as formerly. After a time, perhaps a year, thephosphorescent screen itself will be worn out by theincessant bombardment, will become insensitive andneed renewal. But replace it by a new
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectradioac, bookyear1922
