ILLUSTRATIONS. 



FIG. PAGE 



1. RADIOMETER 4 



2. PERIODICITY OF ATOMIC VOLUMES 24 



3. PERIODICITY OF MELTING-POINTS 25 



4. FIRST PART OF MENDELEEFF'S TABLE 26 



5. THE LATEST TABLE OF THE PERIODIC LAW 28 



6. RELATIONSHIP IN GROUP II 31 



7. RELATIONSHIP IN GROUP VII 32 



8. AN ELECTROSCOPE 47 



9. APPARATUS FOR PROVING THE CONDUCTIVITY OF THE AIR 49 



10. SHOWING THE DIVISION OF A FLAME BETWEEN OPPOSITELY 



CHARGED PLATES 50 



11. APPARATUS FOR STUDYING IONS FROM A HOT WIRE 51 



12. EXPERIMENT FOR DETERMINING THE VELOCITY OF A 



CORPUSCLE 56 



13. SHOWING RAYS DEFLECTED BY HORSE-SHOE MAGNET. ... 57 



14. SHOWING PHENOMENA IN VACUUM TUBE 68 



15. SHOWING THAT THE PHOSPHORESCENCE ARISES FROM 



THE CATHODE 68 



16. PHOTOGRAPHIC REPRESENTATION OF A VACUUM TUBE 



IN ACTION 69 



17. CATHODE RAYS OF CORPUSCLES BROUGHT TO A Focus.. 71 



18. SHOWING THAT CORPUSCLES WILL MOVE A BODY WHICH 



THEY STRIKE 71 



19. NlEWENGLOWSKl's EXPERIMENT 83 



20. THE RESULT OF NIEWENGLOSKI'S EXPERIMENT 84 



21. BECQUEREL'S FIRST EXPERIMENT 87 



22. URANIUM RADIOGRAPH 88 



23. PHOTOGRAPH OF A SECTION OF PITCHBLENDE 91 



24. RADIOGRAPH OF A SECTION OF PITCHBLENDE 91 



25. COMPARATIVE SPECTRA OF RADIUM AND CALCIUM 93 



26. RADIOGRAPH SHOWING THE PENETRATIVE POWER OF 



RAYS FROM RADIUM 96 



27. RADIOGRAPH BY THE CURIES 97 



28 (a). RADIUM CHLORIDE, PHOTOGRAPHED BY DAYLIGHT 98 



(xiii) 



