VIII CONTENTS. 



PAGE 



35. Nucleation 3 8 



36. Radium in sealed aluminum tube 39 



EXPERIMENTS WITH DUST-FREE AIR ENERGIZED BY THE X-RAYS. 



37. Persistence of nuclei due to X-rays in the lapse of time 41 



38. Fog limits for nuclei produced by X-rays 4 2 



39. Sudden exhaustion in the absence of condensation 43 



40. X-ray nuclei at different high pressure differences 45 



CHAPTER III. Critical Conditions in the Formation of Ions and of Nuclei. 



41. Apparatus. X-ray bulbs 47 



42. Fog chambers. Filters with saturator 48 



43. Notation 49 



EFFECT OF LARGE PRESSURE DIFFERENCES. 



44. Nuclei in dust-free air, not energized 49 



45. Dust-free air energized by the X-rays from a distance 51 



46. The same continued. Rays not cut off during condensation 53 



GENERATION AND DECAY OF NUCLEI. 



47. Fleeting nuclei 54 



48. Persistent nuclei 57 



49. Persistence of fleeting nuclei after solution 60 



50. Enlargement of nuclei in dust-free non-energized air 62 



51. Occurrence of water nuclei 63 



52. Cause of periodicity 64 



53. Rain 64 



54. Persistent nuclei in general 65 



55. Graduation of size of fleeting nuclei. Fog limits 66 



56. Secondary generation 69 



NUCLEATION DUE TO RAYS PENETRATING FROM A DISTANCE OR THROUGH DENSE MEDIA. 



57. Effect of distance of the X-ray bulb from the free wooden fog chamber. 71 



58. Generation and decay for radiation from D = 200 cm 73 



59. Electrical effect for different distances 75 



60. Apparent penetration of the X-rays coming from 600 cm 75 



61. Apparent penetration of the X-rays coming from 200 cm. and from 



6 to 7 cm 78 



62. Generation through lead plate and through iron 79 



FOG CHAMBERS INCLOSED IN CASKETS. 



63. Wood fog chamber in lead casket. Penetration 80 



64. The same continued. Radiation from a distance 81 



65. Glass fog chamber. Radiation from a distance 84 



66. Radiation from a distance. Glass fog chamber in lead case 84 



