GLOSSARY. 255 



plants, such as starch, gum, &c., which are composed of the 



immediate elements, viz : the gases and mineral matters. 

 Protoxide, a compound containing one proportion of oxygen. 

 Photographic, pertaining to light; photographic pictures are 



taken by light. 

 Phosphorescence, a peculiar luminous matter without fire or 



combustion, as the light given out by phosphorus, decayed 



wood, putrifying flesh, <fec. 

 Parabola, a conic section arising from cutting a cone by a 



plane parallel to one of its sides. 

 Prism, in optics, a triangular glass instrument for separating 



the rays of light. 

 Polarity, that property which causes one end of a body to 



repel and the other to attract, as in bodies magnetized or 



electrified; pointing towards the poles. 

 Putrefaction, decomposition or decay of organic bodies. 

 Pungent, biting, hot, sharp. 

 Ponderable, possessing weight. 

 Precipitate, to throw down or separate. 

 Phosphates, compounds containing phosphorus. 

 Parallelism,, the state or quality of being parallel. 

 Petrify, to become stone. 

 Pebble, a small stone. 

 Plutonic, pertaining to subterranean heat 

 Porphyry, an unstratified igneous rock. 

 Pegmatite, primitive granite rock, 

 Pumice stone, a species of lava. 

 Plumbago, black lead, graphite. 

 Pulverulent, consisting of fine dust or powder. 

 Phenomena, an appearance. 

 Phase, an appearance, exhibited by the illumination of the 



moon or other planets. 

 Polar elevation, height of latitude, or approach towards the 



poles. 



