Proctor and orbits of Asteroids, 176.
Protoplasm, encystment of, 68.
Purana Era of India, 134.
Pyrenees, history of, 140.
R.
Radioactive elements concerned in mountain building, 125.
Radioactive layer, failure to account for deep-seated
temperatures, 127; assumed thickness of, 128; temperature at base
of, due to radioactivity, 129; in the upper crust of the Earth,
125; thickness of, 126-128.
Radioactive treatment, physical basis of, 251.
Radioactivity and heat emission from average igneous rock, 126;
rarity of, established by haloes, 241, 243.
Radium, chemical nature and transmutation of, 244-245; emanation
of, 245; rays from, 253, 254; table of family of, 253; period of,
253; small therapeutic value of, 254.