GLOSSARY. 
77 
in which the reproductive organs are apparent. Eiy'm. (payepog, 
phaneros, evident, and yap.og, gamos, marriage. 
Physics. The department of science, which treats of the properties 
of natural bodies, laws of motion, &c, sometimes called Natural 
philosophy and mechanical philosophy. Etym. (pvgig, physis, 
nature. 
Phytology, Phytological. The department of science which relates 
to plants — synonymous with botany and botanical. Etym. 
(j)vrov, phyton, plant, and Xoyog, logos, discourse. 
Phytophagous. Plant eating. Etym. fvroy, phyton, plant, and 
(paysiv, phagei/i, to eat. 
PisLiAii, a misprint for Pistia, in vol. ii. p. 98, 1st ed., p. 102, 2d 
ed. The plant mentioned by Malte-Brun is probably the Pistia 
slratiotes, a floating plant, related to English duck-weed, but 
very much larger. 
Pisolite. A stone possessing a structure like an agglutination of 
pease. Etym. mcrov, pison, pea, and \idog, lithos, stone. 
Pit Coal. Ordinary coal ; called so because it is obtained by sink- 
ing pits in the ground. 
Pitch Stone. A rock of an uniform texture, belonging to the un- 
stratilied and volcanic classes, which has an unctuous appear- 
ance, like indurated pitch. 
Plastic Clay. One of the beds of the Eocene tertiary period (see 
Table II. E, p. 390.) It is so called because it is used for 
making pottery. Etym. 7r\acr<rw, £>£asso, to form or fashion. 
Plesiosaurus. A fossil extinct amphibious animal, resembling the 
saurian, or lizard and crocodile tribe. Etym. TcXrjcrtov, plesion, 
near to, and aavpa, saura, a lizard. 
Pliocene. See explanation of this term, vol. iii. p. 58. 
Plutonic Rocks. For an explanation of this term, see vol. iii. 
p. 353. 
Polyp aria. Corals. A numerous class of invertebrated animals, be- 
longing to the great division called Radiata. 
Porphyry. An unstratified or igneous rock. The term is as old 
as Pliny, and was applied to a red rock with small angular 
white bodies diffused through it, which are crystallized felspar, 
brought from Egypt. The term is hence applied to every spe- 
cies of unstratified rock, in which detached crystals of felspar 
are diffused through a base of other mineral composition. 
Etym. 7rop(j>vpa, porphyra, purple. 
Portland Limestone, Portland Beds. A series of limestone strata, 
belonging to the upper part of the Oolite group (see Table II. 
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