Regelation, 284; affecting glacier motion, 285.
Reversal, photographic, explanation of, 211.
Richards and Lembert, atomic weight of lead, 27.
Richter, Jean Paul, Dream of the Universe, 200.
Rock salt in the ocean, amount of, 13.
Rocks, average composition of, 43; radioactive heat from, 126;
rate of solution of, 36.
Russell, I. C., river supply of sediments, 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.