226 



PL A NUDES 



PLATINUM 



primitive human sacrifice, and identifies the Golden Bongh 

 with the mistletoe growing on the oak the only thing 

 in nature which could l>ring Balder to his doom. He hu 

 with unequalled learning and ingenuity traced many 

 cognate customs in classical antiquity, as well as parallels 

 in our modern rustic sprint; '"' midsummer customs, and 

 finds the same significance of the death and resurrection 

 i>f vegetation under the various form- of the Greek myth 

 of Itemeter and Persephone, the Syrian Astarte and 

 Adonis, the Phrygian Cybele and Attis, the Egyptian 

 Isis and Osiris. 



Planudes, MAXIMUS. See ANTHOLOGY. 



Planula. See HYDROZOA. 



I'lasciicia. a decayed town of Spain, in Estre- 

 madura, 130 miles NV.'hy S. ,,f Madrid and 43 NE. 

 of Caceres, is surroundeil with double walls ( 1 197 ), 

 has a fine Gothic cathedral (1498), and a pop. of 

 7090. The monastery of San Yuste, to which 

 Charles V". retired after his abdication, lies 24 miles 

 to the east of 1'lasencia. 



I'lasma. a rare siliceous mineral, a variety of 

 quartz or chalcedony, of a dark-green colour, black 

 when uii|Kilished and seen by reflected light, but 

 very translucent when held between the eye and 

 the light. It is very nearly allied to heliotrope or 

 bloodstone, but has no red spote, is more translu- 

 cent, and is not susceptible of so brilliant a polish. 

 The name is also used in biology for the simplest 

 form of organised matter in vegetable and animal 

 bodies, out of which tlie tissues are formed, especi- 

 ally of the blood-plasma. See BLOOD. 



Plasmodia. SeeCKLL, MYXUMYCKTES. 



Plassey (Paldsi), a battlefield on the lih.-igirathi 

 River, 96 miles N. of Calcutta. The river has now 

 eaten away the scene of the struggle. Plassey is 

 celebrated in the history of India for the great 

 victory gained by dive over Suraj ud Dowlah, 

 Mil mln lar of Bengal, 23d June 1757, a victory which 

 really laid the foundation of British supremacy in 

 India. See CLIVE. 



Plaster. See CAST, GYPSUM, BUILDING. 



Plastering, the art of covering the internal 

 faces of walls, the partitions, anil the ceilings of a 

 house or other building with plaster. It is dilli- 

 cult to get plaster to keep completely dry on the 

 inside faces of external walls unless they are lirst 

 covered with lathing (narrow strips of wood, nee 

 LATH). Ceilings and wooden partitions arc always 

 lathed so as to hold or key the plaster. Plastering 

 is sometimes done in two, 'but most usuallv in three 

 coats. The first or foundation coat is formed of 

 lime and sand (mortar) mixed with hair. This is 

 called prickiiirj if done upon lath, and rendering 

 if it is spread on a bare brick or stone wall, h is 

 crossed with deep inei-ed lines to key the second 

 coat, which consists of fine lime mixed with some 

 coarse plaster of I'ati- (see GYTSI-M ) Jt,uifnl on. 

 The first coat should ! completely dry liefore the 

 second is added, but the latter is 'generally still a 

 little damp when tin; third eo.it or art is put on. 

 This last coat is usually composed of a mixture 

 of fine lime, plaster of Paris, and a little si/e. anil 

 is worked so as to produce a very smooth surfnee. 

 The implements used by the plasterer are chiefly 

 trowels and floating tools, with running moulds for 

 mouldings. Ceiling ornaments and other enrich- 

 ments are formed of plaster of Paris cast in 

 moulds. Mouldings are run in the same material. 

 Plaster of Paris. SIT GYPSUM. 



Plasters are a da-s ,,f medicinal agent* con- 

 sibling of ' adhesive substances, spread upon leather 

 ur elotli, MI us to stick to the part of the body 

 1 | which they are applied.' The plasters of the 

 British Pharmacopoeia owe their adhesiveness 

 eiiln-r to a combination of oxide of lead with fatty 

 acids, or to the presence of a tenacious resin, or 

 to both. The most im|Kirtant arc lead plaster, or 



diachylon, which enters into the composition of 

 many of the others; resin and pitch |ilast> 

 belladonna and opium plasters ; mercury and 

 animoniacurn and mercury plasters; and cantha- 

 riilcs or blistering plaster. Some of the in..-t 

 tenaciously adhesive of plasters (not in the Phar- 

 macopieia) are made with preparations of india- 

 rubber. Court or sticking plaster, for dressing 

 slight wounds, consists of a thin laver of isinglass 

 spread upon silk, and differs from tlie others men 

 tioned in requiring to he softened with warm water 

 before it will adhere; Goldlicater's Skin (q.v.) is 

 also used for the same purpose. They are employ ed 

 with two distinct aims viz. to act aucjuaueauy, 

 as by afl'ording artificial support to weak muscular 

 structures, by preventing threatened or tedious 

 excoriations, by protecting parts already excoriated 

 from the action of the air, &c. ; and to act jiin/i 

 rinnlh/ as counter-irritant, stimulant, discutient, 

 alterative, anodyne, &c, 

 Plastilina. See CLAY. 

 Plata, LA. See AUOEXTINE REPUBLIC, LA 

 PLATA, LA PLATA (Rio DE). 



Plata'a (Gr. Plataiai), a city in the western 

 part of Bo3otia, on the borders of Attica, and at 

 the foot of Mount Citliirron, (i miles from Thebes. 

 In 480 B.C. it was destroyed by the Persians, lie 

 cause the inhabitants had" taken part with Athens 

 in the battle of Marathon; but in the following 

 year it was the scene of the glorious victory won 

 by the Lacedemonian Greeks, under Paiisanias 

 and Aristides, over the Persian hordes commanded 

 by Mardonius. In the third year of the Pelopon 

 nesian war (429) it was attacked by a Thchan- 

 Lacedemonian force, and heroically defended it-elf 

 for more than two years, until it was starved into 

 surrender ; the little garrison of about 200 men 

 were put to the .sword, and the city was razed to 

 the ground. Such of the I'laia-ans as escaped were 

 hospitably received at Athens. By the treaty of 

 Antalcidas (387) their children were allowed to go 

 back again, and rebuild their city, after an exile ',.1 

 forty years; but they were again driven out by 

 their implacable enemies the Thebani ; and half 

 a century elapsed liefore the victory of Philip of 

 Macedon at Chirronea enabled the Plata-aim to 

 finally return to their homes. After this the city 

 was inhabited till the 6tb century A.D. 

 Plateaus. See TABLKLAND& 

 Plate-marks. See HALL-MARKS. 

 Plate-powder, a comjiosition of Houge (q.v.) 

 and prepared chalk used for cleaning gold and silver 

 plate and plated articles. A gray plate powder is 

 also sometimes made by levigating quieksiUcr 

 with twelve times its weight of prepared chalk ; it 

 put* a remarkable brilliancy on silver-plate, but 

 is very injurious to it. 



Plating signifies the covering of an inferior 

 metal with one of the precious metals, the object 

 Ix-ing to give the appearance of silver or gold to 

 articles chiefly intended for table use. Previous in 

 the introduction of elect m plating (see ELECTRO- 

 MI-: I M.l.riaiY) the method generally pursued v 

 ShMtld-plating by means of a plating furnace 

 soldering on to one or Inith sides of an ingot of the. 

 Laser metal a thin plate of silver. See also TlN- 

 I'LATE, GAI.VAMSI n IHOV 



ri.-llilluf >|M-. See PlIOTOCKAPIIY. 

 Platinum (sym. Pt : atom. wt. 1!I7'4 : sp. gr. 

 21'4H to 21 '"id) is one of the 'noble metals.' It is 

 r onnd only in the native state, usuallv occurring in 

 small glistening granules of a steel-gray colour, 

 which always contain, along with some gold, copper, 

 iron, and sand, an admixture, in varying proportions, 

 if several metals indium, rhodium, palladium, 

 isiniiiiii. ruthenium- most of which are rarely found 



