s, 10.

Rutherford, Sir E., determination of age of minerals, 19, 20; age
of rocks by haloes, 22; derivation of actinium, 226; artificial
halo, 229; number of alpha rays from one gram of radium, 237.

S.

Salt range deposits of India, 134. 135.

Saltness of the ocean due to denudation, 41-46.

Salisbury (and Chamberlin), the Larimide range, 121.

Salmon, Rev. George, on creation, 301.

Satellite, velocity of, in its orbit, 191; method of finding path
of, over a rotating primary, 189 _et seq._; direct and
retrograde, 178; ultimate end of, 178; path of, when falling into
primary, 179; effect of Mars' atmosphere on infalling satellite,
179; stability of close to primary, 180; effects of, on crust of
primary, 180 _et seq._

Schiaparelli, observations on Mars, 165 166.

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.

Skating not dependent on smoothness of ice, 260; history of,
273.

Skating only possible on very few substances, 279.

Soddy, F., on isotopes, 24.

Sodium, deficiency of, in sediments, 44; discharge of rivers,
14.

Soils, formation of, 37-39; surface area exposed in, 39.

Sollas, W. J., age of Earth by sodium in ocean, 14; thickness of
sediments, 6.

Spencer, on division of protoplasm, 67.

Spores, number of molecules in, 97.

Stevenson, Dr. Walter C., and technique of radioactive treatment,
259.

Stoletow, photo-electric activity anal absorption, 207.

Stopping power of substances with reference to alpha rays, 219.

St