PL A 



570 



PL A 



stances spread over with it appear as if 

 gilded. From this circumstance, it lias 

 been named : wrrat, pitch, and xotMo;, 

 beautiful ; hence pittacall, beautiful pitch. 

 Pittacall would be highly useful as a pig- 

 ment, could it be procured sufficiently 

 cheap. 



PITYRI'ASIS, from trirvftv, bran. Dr. 

 "Willan's name for a genus of cutaneous dis- 

 eases, characterised by irregular patches 

 of small thin scales, which repeatedly 

 form and separate, but never collect into 

 crusts, nor are attended by redness or in- 

 flammation. 



Pi'c. In music, an Italian word for " a 

 little more." It is prefixed to other terms, 

 as phi allegro, a little brisker ; piu forte, a 

 little bolder, &c. 



PIV'OT (French). 1. The pin, or short 

 shaft, on which a body (as a wheel) turns 



or revolves. 2. In military language, 



that soldier upon whom the different 

 wheelings are made in the evolutions of 

 the drill. 



Fix. 1. A Latin word for Pitch. 2. 



For Latin pixis A little box in which 

 the consecrated Host is kept in Roman 

 Catholic churches. 



PIZZICA'TO. In music, an Italian word, 

 signifying that the strings of the violin 

 must be pinched with the fingers. 



PLA'CARD (Fr. and Eng.). 1. A written 

 or printed paper, posted in a public place. 

 It seems to have been formerly the name 

 of an edict, proclamation, or manifesto, 

 issued by autnority. 2. In architec- 

 ture, the decorations of a chamber-door. 



PLACEX'TA, a cake. 1. In anatomy, a 

 spongy body, which forms the medium by 

 which" the mother and child in the womb 

 are connected. 2. In botany, the recep- 

 tacle of the fructification of plants. 3. 



Infossilology, the name given by Klein to 

 a section of Catocysti, because the shells 

 are flat. 



PLACOI'DIANS. One of the orders into 

 which fishes are divided by M. Agassiz. 

 The order comprises all the cartilaginous 

 fishes of Cuvier, except the sturgeons. 

 The distinguishing character is the irre- 

 srular covering of enamel plates upon the 

 skin : whence the name, <rAa|, a plate, 

 and iito; , form. Epithet, Placoidian. 



PLA'OAI, MEI.'ODIES, from -rXefyios , ob- 

 lique. In music, such as have their notes 

 between the fifth of the key and its octave 

 or twelfth. 



PLAGIO'STOMA. Agenusofsub-equivalve, 

 inequilateral, oblique shells, found only in 

 a fossil state, and chiefly in the chalk. 

 Name (romrr^cfyio;, oblique, and ^TOIACC, 

 mouth. Several species are known. 



PLAIN CHANT. In music, an ancient term 

 signifying the chief melody. 



PLAIN CHART. A chart wherein the 



meridians and parallels of latitude are 

 straight lines. 



PLAIN'-SAILINO. The workin? of a 

 ship's course on a plain chart, as if t/u. 

 earth were an extended plain. This kind 

 of reckoning should never be attempted, 

 except within the tropics. 



PLAN. A draught or form: properly, 

 the representation of anything drawn on 

 SL plane. In a geometrical plan, the parts 

 are represented in their natural propor- 

 tions ; a perspective plan is exhibited with 

 diminution according to the rules of that 

 science. The raised plan of a building is 

 the elevation. The plan of a ship, ma- 

 chine, &c., is a section thereof, unless 

 ground-plan is the term used. The plan of 

 a bastion answers to the face of the same. 



PLANA'RIA. The name of a genus of 

 intestinal worms. 



PLAN'CHEI, Fr. planchette. A flat piece 

 of metaj, as theplanchets prepared for the 

 coining-press. 



PLANE, Lat. planus. I. In geometry, a 

 surface which coincides everywhere with 

 a right line, answering to a plain in 

 popular language. In perspective, geo- 

 metrical plane is a plane surface, parallel 

 to the horizon, placed lower than the eye, 

 wherein the visible objects are imagined 

 without any alteration, except as to size. 

 A horizontal plane is a plane parallel to the 

 horizon, which passes through the eye, 

 or has the eye supposed to be placed in it. 

 A vertical plane is a plane surface, which 

 passes through the principal ray, and con- 

 sequently through the eye, and is per- 

 pendicular to the geometrical plane. 



2. In astronomy, an imaginary surface, 

 supposed to pass through any of the curves 

 described on the celestial sphere. Thus, 

 we speak of the plane of the ecliptic, the 



plane of a planet's orbit. &c. 3. In 



joinery, an edged tool, of which there are 

 great variety for different uses, and known 

 by different names. The same principle 

 is, however, common to all the sorts : a 

 broad chisel or steel cutter, called the 

 plane iron, is fixed into a hole cut obliquely 

 through a piece of wood (perfectly plane 



on one side), called the plane stock, beyond 

 which the iron slightly projects, leaving 

 an aperture before it called the mouth of 

 the plane. The common use is to shave 

 wood smooth, and those adapted for this 

 purpose are planet properly so called. 

 Their varieties are the jack plane, about 

 17 inches long ; the long plane, about 26 

 inches ; the shooting plane or jointer, 



