PHONOPHORE                                          147!

Phonophore (jō'n-fōr), is a device of Langdon Davies of London, England, for transmitting electric signals through circuits which are not closed. Messages have been sent over wires open at both ends, in circumstances which would render ordinary telegraphing impossible. The same wire has been used at once for ordinary telegraphing and for the transmission of phonophore signals. When, the resistance having been greatly increased, the ordinary signals ceased, those of the phonophore continued as distinct as before. The transmitter is fitted with a vibrating reed at one end and the receiver with a stretched steel band at the other, which can be tuned to the same note.

Phos'phates, salts formed from the phosphoric acids, are of great importance in plant and animal life. Phosphate of soda, in any of its three forms, may be dissolved in water, and is found in all the soft and fluid portions of the bodies of animals. Phosphates abound especially in the blood and tissues of carnivorous animals. They are necessary to the process by which cellular tissue is built up from the blood. Phosphate of lime is not only needed in the bodies of animals, but when properly prepared it is a valuable manure for plants. In animals it forms four fifths of the enamel of the teeth and more than half the substance of the bones. Normal phosphate of lime or normal calcium phosphate is indeed insoluble; but in the fluids of the animal body it is held in solution as a loose compound with albumen etc. As calcium phosphate is necessary to a fertile soil, bone-dust and mineral phosphates of calcium are sold commercially as fertilizers. Bones have for many years been an important form of phosphate manure. They generally are first boiled or steamed. Bone-phosphates, being slow-acting fertilizers, should be used finely ground and as a permanent benefit to the soil rather than as direct plant-food. Phosphates associated with organic matter decompose more quickly than purely mineral phosphates do. They therefore are more readily available fertilizers. Great deposits of lime-phosphates are found in Alabama (q. v.), Florida, South Carolina and Tennessee. See Fertilizers and Phosphorus.

Phosphorescence (Jos'fŏr-ĕs'sens). When a body emits light because it has been raised to a high temperature, we describe the phenomenon by the name incandescence; but when a body emits light without being raised to a correspondingly high temperature, the process is called luminescence. A piece of sugar cut in the dark will emit a faint light; this is an example of luminescence. A solution of sulphate of quinine held in ultraviolet light will emit a faint blue light ; this is another example of luminescence, which is generally known as -fluorescence. The Germans call it photplumines-

5                                                    PHOTIUS

cence, because it is an effect produced by light. Red ink, when made of eosin, behaves in the same way as quinine. But as soon as the illumination ceases, these bodies cease to give off their fluorescent light. There are other bodies, however, as sulphides of barium, calcium and strontium, which continue to exhibit fluorescence even after illumination has ceased. This phenomenon of persistent fluorescence is called phosphorescence. Becquerel has proved that most bodies exhibit phosphorescence, but only for a very short time after illumination. The student should carefully note that the glow exhibited by phosphorus in the dark is due to slow oxidation, and is not a case of phosphorescence at all. Properly classified, it is a case of chemical luminescence.

Phos'phorus, one of the nonmetallic elements. At ordinary temperatures it is an almost colorless or faintly yellow, solid substance, having the glistening appearance and consistency of wax. If it be heated to i4o°F. in the air, it catches fire and burns with a brilliant white flame. It is so inflammable as to burn by mere friction at ordinary temperatures. Even the warmth of the hand may set it to burning. In experiments care must be taken lest the hands be severely burned. It is kept in water lest it may spontaneously get on fire. It shines in the dark, from the slow combustion it undergoes. Taken internally, it is a powerful irritant poison. Persons engaged in the manufacture of matches are frequently seriously affected by its fumes. Scientists have overcome this danger to some extent by the discovery of red phosphorus, which is prepared from ordinary phosphorus by heating it in a closed iron vessel. Phosphorus is not found in an uncombined state in nature. It was first discovered by Brandt in 1669. Bones at present furnish a large part of the phosphorus of commerce. Bones are burned to whiteness and powdered, then mixed with sulphuric acid to decompose the phosphate of lime in the ash ; the solution of the superphosphate is evaporated to a syrup, mixed with charcoal and distilled; then the phosphorus rises in vapor and is condensed. The mineral apatite is also used instead of bones. See Phosphates.

Photius (}ō'sh-ŭs), (A. D. 820-91), a patriarch at Constantinople, whose chief distinction is his influence in bringing about the separation between the Latin and the Greek church. The separation did not completely take place during his time, but its beginning did. Steps were taken under his leadership which could not be retraced. A council in 867 raised a controversy of doctrine and discipline between the churches of the east and west. The east withdrew from the west. Another council condemned the western church. Some time after this the separation was completed.