H.
Haimanta period of India, 135.
Halley, Edmund, finding age by saltness of ocean, 13.
Hallwachs, photo-electric activity and absorption, 207.
Haloes, pleochroic, finding age of rocks by, 21; due to uranium
and thorium families, 227; radii of, 227; over-exposed and
underexposed, 228; intimate structure of, 229 _et seq._;
artificial, 229; tubular, in mica, 230; extreme age of, 231;
effect of nucleus on structure of, 232; inference from spherical
form of, in crystals, 233; structure of, unaffected by cleavage,
235; origin of the name "pleochroic,"235; colouration due to
iron, 235; colouration not due to helium, 236; age Of, 236; slow
formation of, 237, 238; number of rays required to build, 237;
and age of the Earth, 238-241.
Hayden, H.H., geology of the Himalaya, 134, 138, 139.
Heat-tendency of the universe, 62.
Heat emission from the Earth's surface, 126; from average igneous
rock due to radioactivity, 126.
Helium and the alpha ray, 214, 222; colouration of halo not due
to, 236.
Hering, E., and physiological or unconscious memory, 111.