Paris, Dr., Faraday's letter to, 243.
Pascal takes a barometer up the Puy de Dome, 17.
Pennsylvania fireplace invented by Franklin, 63;
_Gazette_ published by Franklin, 53.
Perpetual motion, Rumford's contrivances for, 150;
impossibility of, 322.
Philadelphia, Franklin's first arrival in, 46;
Library, foundation of the, 55.
Photometer, Rumford's, 187.
Pigments, effects of mixing, 217.
Points _versus_ knobs, 95, 131.
Polarization, explained by transverse vibrations, 226;
of light discovered by Malus, 226.
"Poor Richard's Almanack," 60.
Pressure of the air the cause of suction, 29.