Schmidt, C., original depth of Alpine layer, 131-148; structure
of the Alps, 152.
Schmidt, G. C., on photo-electricity, 207, 208; effect of
solution on photo-electric activity, 213.
Schuchert, C., average area of N. America during geological time,
16.
Sedimentary rocks, average composition of, 43; mass of,
determined by sodium index, 47.
Sedimentation a convection of energy, 133.
Sediments, average river supply of, 11; on ocean floor, mass of,
48; average thickness of, 49; precipitation of, by dissolved
salts, 56-58; radioactivity of 130; radioactive heat of,
influential in mountain building, 130, 131; rate of collecting,
7; determination of mass of, 8; river supply of, 10; total
thickness of, 6.
Semper, energy absorption of vegetable and animal systems, 78.
Sensitisers, effects of low temperature on, 210.
Simplon, radioactive temperature in rocks of, before denudation,
132.
Skates, early forms of, 273; principles of construction of, 273
_et seq._; action of, on ice, 276; bite of, 278-280.