P H 



[352] 



PHY 



protrudes in each valve from beneath, 

 the umbones. Pholades are found 

 at depths varying to nine fathoms ; 

 they pierce wood, rocks, indurated 

 clay, &c. They are much sought 

 for in consequence of their delicious 

 flavour. 



PHO'LADITE. A fossil or petrified 

 pholas. 



PHO'NOLITE. (from 0oj^, sound, and 

 X/00S, a stone, Gr.) Another name 

 for clinkstone. A felspathic rock, 

 sonorous when struck with a ham- 

 mer, from which circumstance it 

 derives its name. 



PHO'SPHATE. A salt formed by the 

 union of phosphoric acid with a 

 salifiable base. 



PHO'SPHATE OF LIME. This is found 

 in the bones of animals, and consti- 

 tutes their base ; as well as in the 

 mineral kingdom. It consists of 

 lime 59*0, phosphoric acid 41'0. 

 It is destitute of taste, insoluble in 

 water, and not affected by exposure 

 to the atmosphere. Exposed to 

 a very high temperature it becomes 

 soft, and is converted into a white 

 semitransparent enamel, or rather 

 porcelain. Human bones, accord- 

 ing to Berzelius, contain 51*04 of 

 phosphate of lime, and the enamel 

 of teeth, according to Mr. Pepys, 

 is composed of 78 per cent, of it. 

 Sulphuric, nitric, muriatic, fluoric, 

 and several vegetable acids are 

 capable of more or less decomposing 

 phosphate of lime. 



PHOSPHORESCENCE or THE SEA. This 

 luminous appearance of sea-water 

 arises from the presence of immense 

 numbers of microscopic niedusaB 

 which people every region of the 

 ocean, and, being specifically lighter 

 than the sea-water, float in incal- 

 culable multitudes on its surface. 



PHOSPHORE' SCENT. Emitting light in 

 the dark without sensible heat. 



PHO'SPHORITE. Amorphous phospate 

 of lime. The chaux phosphate e 

 terreuse of Haiiy; phosphorit of 

 Werner ; phosphorite of Jame- 



son. A variety of apatite, 

 with commonly an earthy aspect : 

 it occurs in masses whose surface 

 often displays mammillary projec- 

 tions. Fracture dull and earthy. 

 Colour white or grey, often marked 

 with spots or zones of a brownish 

 tinge. Specific gravity from 2-8 

 to 3-2. Before the blow-pipe it is 

 infusible, but its powder thrown 

 upon live coals emits a yellowish- 

 green phosphorescent light. In 

 Spain it forms whole mountains; 

 it is also met with in Germany. 

 According to Pelletier, it contains 

 lime 59, phosphoric acid 34, and 

 the remainder consists of the car- 

 bonic, fluoric, and muriatic acids, 

 with a trifling portion of silex and 

 oxide of iron. 



PHO'SPHORTJS. (0wo-0o/9V9, Gr. phos- 

 phorus, Lat. phospkore, Fr.) One 

 of the simple or elementary sub- 

 stances, and belonging to that sub- 

 division termed non-metallic. Phos- 

 phorus is principally known as 

 entering into the chemical com- 

 position of animals. As a com- 

 ponent part of minerals, phosphorus 

 is rare; but there must be some 

 amount of it entombed in fossili- 

 ferous rocks. Phosphorus is never 

 found pure in nature, and is only 

 to be obtained from organic matter 

 by elaborate chemical processes. It 

 is yellow, and semi-transparent; 

 resembling wax in softness, but 

 more cohesive and ductile. Specific 

 gravity 1*77. Its affinity for oxy- 

 gen is so great that it burns spon- 

 taneously in the atmosphere. It 

 should always be kept in bottles 

 filled with water, and well corked. 



PHOTO'METER. (from 0>s, gen, 0u>ros, 

 and fierpov, measure, Gr.) An 

 instrument for measuring the in- 

 tensity of light. 



PHYLLA'DE. The name given by 

 D'Aubuisson, and the French geol- 

 ogists, to clay-slate. Under the 

 name of Phyllade, Dr. Boase in- 

 cludes a genus of rocks comprising 



