72. Cathode Rays Propagated, but Not LENARD Generated, in the Highest Possible Vacuum. Air Less Turbid when Rarefied. 72_a_. Cathode Rays, while Traversing the LENARD Exhausted Observing Tube, Deflected by a Magnet. No Turbidity in a Very High Vacuum. 72_b_. An Observing Tube for Receiving the LENARD Rays and Adapted to be Exhausted. 73. Phenomena of Cathode Rays in an LENARD Observing Tube Containing Successively Different Gases at Different Pressures. Phosphorescent Screen Employed for Making the Test. 74. Cause of the Glow Outside of the LENARD Aluminum Window. Glow Not Caused by External Cathode Rays. Sparks Drawn from the Aluminum Window. Transmission of External Cathode Rays Dependent Alone upon the Density of the Medium. 75. External Cathode Rays of Different LENARD Kinds Variably Diffused. Theoretical Observations. 76. Law of Propagation of External Cathode LENARD Rays. 77. Charged Bodies Discharged by External LENARD Cathode Rays. Discharge at Greater Distances than Phosphorescence. Not Certain as to the Discharge Being Directly Due to Intermediate Air. 78. Source, Propagation, and Direction of DE KOWALSKIE Cathode Rays. General Conclusions. CHAPTER VII. 79. X-rays Uninfluenced by a Magnet. Source ROENTGEN of X-rays Determined by Magnetic Transposition of Phosphorescent Spot. 80. Source of X-rays may be at Points ROENTGEN within the Vacuum Space. Different Materials Radiate Different Quantities of X-rays. 81. Reflection of X-rays. ROENTGEN 82. Examples of Penetrating Power of ROENTGEN X-rays. 83. Permeability of Solids to X-rays ROENTGEN Increases Much More Rapidly than the Thickness Decreases. 84. X-rays Characterized. Fluorescence and ROENTGEN Chemical Action. 85. Non-refraction of X-rays Determined by ROENTGEN Opaque and Other Prisms. Refraction, if Any, Exceedingly Slight. 86. Velocity of X-rays Inferred to be the ROENTGEN Same in All Bodies. 87. Non-double Refraction Proved by Iceland ROENTGEN and Spar and Other Materials. MAYER