charge--Cathode rays give rise to X-rays--The canal
rays--Villard's researches and magneto-cathode rays--
Ionoplasty--Thomson's measurements of speed of rays--
All atoms can be dissociated.

§ 2. Radioactive Substances: Uranic rays of Niepce
de St Victor and Becquerel--General radioactivity of
matter--Le Bon's and Rutherford's comparison of uranic
with X rays--Pierre and Mme. Curie's discovery of
polonium and radium--Their characteristics--Debierne
discovers actinium.

§ 3. Radiations and Emanations of Radioactive
Bodies: Giesel's, Becquerel's, and Rutherford's
Researches--Alpha, beta, and gamma rays--Sagnac's
secondary rays--Crookes' spinthariscope--The emanation
--Ramsay and Soddy's researches upon it--Transformations
of radioactive bodies--Their order.

§ 4. Disaggregation of Matter and Atomic Energy:
Actual transformations of matter in radioactive bodies
--Helium or lead final product--Ultimate disappearance
of radium from earth--Energy liberated by radium:
its amount and source--Suggested models of radioactive
atoms--Generalization from radioactive phenomena
-Le Bon's theories--Ballistic hypothesis generally
admitted--Does energy come from without--Sagnac's
experiments--Elster and Geitel's _contra_.