PUR 



563 



PHY 



t)ie strength of the light), the picture is 

 made, and to fix it, it is only necessary to 

 immerse the paper in a solution of sul- 

 phate of potash. A simpler picture may 

 be made (as of a leaf, feather, or the like), 

 by simply placing the object between the 

 prepared paper and the pane of a window 

 exposed to the sun. Chromate of potash, 

 also, may be used in the preparation of 

 the paper, instead of nitrate of silver, and 

 for botanical drawings it is preferable. 



PHOTOM'ETER, from QU;, light, and 

 t*.ir$itu, to measure. An instrument or 

 apparatus for measuring the intensity of 

 light. Instruments for this purpose have 

 been invented by Count Rumford, M. de 

 Saussure, Mr. Leslie, and others, but they 

 are all very defective. A very convenient 

 photometer, for solar light, may be made 

 by means of paper prepared as for pho- 

 togenic drawings, as by exposure to the 

 light for given times, slips of this paper 

 will readily afford a comparative measure 

 of the photic intensity of the rays which 

 fall upon it ; and as mechanism may be 

 easily adapted to the constant shifting of 

 ihe paper, so that only a very small but 

 definite portion of it shall be exposed for 

 a known length of time, the shades upon 

 it may be reduced to a scale, and numeri- 

 cally estimated. The instrument will thus 

 be rendered self- registering, and attended 

 with few sources of error. 



PHOTOM'ETHU, sp^s, and p.tr$ov, mea- 

 sure. The science which treats of the 

 measurement of light. 



PHOTOPH'OBY, ) from Qcos, light, and 



PHOTOPHOJJ'IA, ) tpeGttu, to dread. In- 

 tolerance of light, arising from too great 

 sensibility of the retina of the eye. 



PHO'TOPBY , } from tfus , light, and o^is , 



PHOTOP'SEA, ) vision; lucid vision. An 

 affection of the eye in which the patient 

 perceives luminous rays, ignited lines, 

 coruscations, &c. 



PHRASE, <pg(ns expression. In music, 

 a short melody, in which a complete 

 musical idea is not expressed. 



PHRA'TRY. A subdivision of Athenian 

 citiiens. 



PHREN'IC. $f(M0< Belonging to the 

 mind, or to the diaphragm. The term is 

 now only used in the latter sense. 



PHRENI'TIS. *E<T/S. Phrensy. In- 

 flammation of the brain (regarded as the 

 beat of the mind, ;*, the mind). 



PHRENOL'OOY, from feyy, mind, and 

 lo'/osi discourse; the doctrine of the 

 mind. The term is now restricted to that 

 particular viw of the constitution first 

 promulgated by Drs. Gall and Spurzheim ; 

 in which it is believed certain portions of 

 the brain called organs minister to dif- 

 ferent faculties, propensities, and senti- 



ments of the individual. The intellec- 

 tual powers are assumed to reside in the 

 anterior parts of the brain, the senti- 

 ments in the middle, and the animal pro- 

 pensities in the posterior parts. That 

 the general principles and scope of phren- 

 ology are true, seems to be generally ad- 

 mitted ; but much doubt still exists with 

 regard to the details. 



PHRTGA'NEA. A genus of neuropterous 

 insects belonging to the family Plicipennes, 

 and called papilionaceous flies by Reau- 

 mur. They frequent ponds, and their 

 nymphs are aquatic. 



PHRY'GIANS. An early sect of heretics, 

 who abounded in Phrygia. 



VHTHIS'IS. $8uri<;, from <$0ti, to con- 

 sume. Pulmonary consumption. 



PHYLAC'TERY. <t/Aa*r>;g/av, from 

 tyvXitfffflu, to preserve. An amulet worn 

 about the person, to prevent disease. 



PHY'L*, <pj*Aj, tribe. The tribes into 

 which Attica was anciently divided. A 

 superintending officer, named a.phylarch, 

 was appointed to each tribe. 



PHY L'LADE. The name given by the 

 French geologists to clay-slate, from 

 <^AAo?, leafy. 



PHYI/LITE, from <poAXov, a leaf, and 

 A<0?, stone, a petrified leaf. 



PHY'MA, from $uiu, to produce. 1. A 

 tubercle. 2. A genus of cuticular dis- 

 eases, of which anthrax is a species. 



PHYLLo'DiA,ipwXX*,leaf. The petioles 

 of certain leafless plants, which perform 

 all the functions of leaves. 



PHY LLO'DOCE. A sub - genus of Nereides , 

 distinguished by their broad leaf-like 

 branchiae, from which they are named 

 (fyAXflv, a leaf, and Soxis, trabicula. 



PHYLLOSO'MA. A genus of Crustacea 

 belonging to the family Bipeltata (q. v.). 

 The species inhabit the Atlantic Ocean 

 and Oriental Seas. 



PHYSA'LIA. A genus of hydrostatic 

 Acalepha resembling an extremely large 

 oblong bladder, whence the name from 

 Suiraica, to inflate. The animal swims on 

 the surface of the sea in calm weather ; 

 and its touch is said to sting and burn 

 like the sea-nettle. 



PHYS'ALITE. Pyrophysalite. A sub- 

 species of prismatic topaz, so named from 

 VVO-OKU, to inflate, because it intumescc* 

 with heat. 



PHYS'CONY, from Qvffxtuv, a big-bellied 

 fellow. Enlargement of the abdomen, of 

 which there are several species, denomi- 

 nated from the viscus in which the en- 

 largement takes place. 



PHYSK'TER. A genus of whale-fish, the 

 Cachalots, known by a very voluminous 

 head, the superior portion of which con- 

 sists almost entirely of large cavities 



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