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P I 



alescent. Recent pinna? are found 

 in the ocean at depths varying to 

 seventeen fathoms; they are moored 

 by a long silky byssus, which has 

 been manufactured into stockings 

 and gloves. Pinnse have been found 

 fossil in the limestone of Gloucester- 

 shire, "Wiltshire, and Somersetshire. 



PI'NNTGRADA. A division of the order 

 Oarnivora, of which the Seal and 

 Morse are examples. 



PI'NITE. A silicate having one equi- 

 valent of silicate of potash, or pro- 

 toxide of iron, to one of bisilicate 

 of alumina, and also containing 

 water. Sp. gr. 2'8. Slightly 

 translucent ; colourless before the 

 blowpipe, and fuses at the edges to 

 blistered glass. 



PI'NNITE. A fossil pinna. 



PI'NNATE. \fpinnatus, Lat. winged.) 



PI'NNATED. ) In botany, applied to 

 compound leaves, composed of many 

 leaflets, placed on each side of the 

 petiole ; these are placed in pairs 

 opposite to each other, and in some 

 cases, an odd leaflet at the termina- 

 tion, or, in others, a tendril: of 

 the former the rose furnishes an 

 example ; of the latter, the vetch. 



PINNA'TIFID. In botany, applied to 

 leaves cut transversely into several 

 deep, oblong, parallel segments, 

 the incisions reaching nearly to the 

 midrib, and dividing the leaf into 

 irregular forms, termed lobes. The 

 groundsel affords a familiar illus- 

 tration. 



PIPE-CLAY. The Pfeifenthon of Wer- 

 ner. This is the purest kind of 

 potter's clay, and is called pipe- 

 clay, from its being manufactured 

 into tobacco pipes. It is of a grey 

 or greyish white colour ; is infusi- 

 ble ; and on exposure to a strong 

 heat becomes white. It is abun- 

 dant in Devonshire and Stafford- 

 shire; a stratum, in a horizontal 

 position above the chalk, extends 

 from Headfast Point to beyond 

 Corfe Castle in Dorsetshire. It 



forms the basis of the Queen's 

 ware pottery. 



PISCI'VOROTJS. (from piscis, a fish, 

 and voro, to devour, Lat.) Feeding 

 on fishes ; devouring fishes ; sub- 

 sisting on fishes. 



PI'SIFORM. (frompisum, a pea, and 

 forma, form, Lat.) Of the form of 

 a pea ; having a structure resem- 

 bling peas. 



PI'SIFORM IRON ORE. j The pea ore 



PISIFORM IRON STONE. ) of Jame- 



son ; pisiform iron stone of Kirwan. 

 A variety of argillaceous oxide of 

 iron, occurring in small masses or 

 grains, nearly or quite spherical, 

 and often equal in size to a pea, or 

 even larger. These globules are 

 composed of thin, concentric layers, 

 which decrease in density as they 

 approach the centre. The exterior 

 layers are compact, and present an 

 even, glistening fracture with a 

 resinous lustre, whereas the centre 

 of the grain is almost always 

 friable, and has a dull earthy 

 fracture. They are easily broken, 

 and may be cut by a knife. Spe- 

 cific gravity 3.40. These grains, 

 sometimes solitary, are generally 

 united by a ferruginous cement, 

 either calcareous or argillaceous, 

 which adheres to their surface. 

 This variety is composed of oxide 

 of iron 71'5, water 14-5, silex 7'5, 

 alumine 3*5, oxide of manganese 

 0*5. It is abundant in France, 

 Switzerland, and Germany : oc- 

 curring in secondary rocks. 

 PI'SOLITE. (from TTIOOV, a pea, and 

 X/009, a stone.) So called from its 

 resembling an agglutination of 

 pease. The pisolithe of Brongniart ; 

 the peastone of Jameson. Pisolite 

 is nearly or quite opaque, and 

 consists of small rounded masses, 

 composed of concentric layers, each 

 concretion having a grain of sand 

 for its nucleus, or centre. These 

 concretions, agglutinated by a cal- 

 careous cement, form masses of 



