Penjal traps, 135.
Pepys and skating, 273.
Perry, coefficient of friction of greased surfaces, 265.
Phobos, dimensions of, 177; orbit of, 177.
Photoelectric activity and absorption, 207; persists at low
temperatures, 208, 209; not affected by solution, 213.
Photo-electric experiment, 205; sensitiveness of the hands, 207;
theory of latent image, 204, 209 _et seq._
Photographic reversal, experiments on, by Wood, 211; theory of,
210.
Piazzi, discovery of first Asteroid, 175.
Pickering, W. H., observations on Mars, 167.
Planet, slowing of axial rotation of, 189.
Plant, expectant attitude of, 109.
Pleochroic haloes, measurements of, 224; theory of, 224 _et
seq._; true form of, 226; radius of, and the additive law, 225;
absence of actinium haloes, 225; see _also_ Haloes; mode of
occurrence of, 223 _et seq._
Poole, J. H. J., proportionality of thorium and uranium, 26.
Poulton, uniformity of past climate, 17.
Pratt, Archdeacon, and isostasy, 53.
Préalpes, exotic nature of, 150, 151.
Prematerial universe, nature of a, 297, 300.
Prestwich and thickness of rigid crust, 128; history of the
Pyrenees, 140.
Primitive organisms, interference of, 89; life-curves of, 88.
Proctor and orbits of Asteroids, 176.
Protoplasm, encystment of, 68.
Purana Era of India, 134.
Pyrenees, history of, 140.