PIL 



PIN 



of the tissues of plants by means of dis- 

 section. 



PHYTOZO'A (^vToi/, aplant, ^Zov, an 

 animal). Animal plants, or polyps ; a 

 class of Radiate animals, named from 

 their plant-like forms ; the Zoophytes of 

 old authors. 



PHYTOZOA'RIA (^.;t6v, a plant, 

 ^wov, an animal). A term applied by 

 Ehrenberg to those minute aquatic ani- 

 mals which are more commonly termed 

 infusoria and microzoaria. They are 

 distinguished into the polygastrica and 

 the rotifera. 



PI'CAMAR {in pice amarum). The 

 bitter principle of tar, and of all empy- 

 reumatic products. 



PI'CIDiE {picus, a woodpecker). Picine 

 birds, or woodpeckers; a family of the 

 Scansores, or Climbing birds, character- 

 ized by their long, straight, angular 

 beak, the end of which is compressed 

 into a wedge, adapted to perforate the 

 bark of trees. 



PICRO'LITE. A green or yellow 

 mineral consisting chiefly of magnesia ; 

 found traversing beds of magnetic iron 

 ore. 



PICRO'SMINE {niKpo^, bitter, htr/jiij, 

 odour). A mineral species, consisting of 

 silicate of magnesia; found in the iron 

 mine of Englesburg, in Bohemia. 



PICROTO'XIN. The deleterious prin- 

 ciple of the cocculus indicus. It is ex- 

 tracted by means of water and alcohol, 

 and eventually crystallizes. 



PIERRE DE TRIPES. The name 

 given to a sub species of prismatic gyp- 

 sum, or anhydrite, from its convoluted 

 concretions. 



PIEZO'METER (ira^cj, to press, 

 fxerpov, a measure). An instrument for 

 ascertaining the compressibility of 

 liquids. 



PILE. An apparatus for exhibiting 

 the phenomena of Galvanism, and con- 

 sisting, literally, of a pile or column of 

 metallic plates of zinc and copper and 

 discs of wet card, placed in succession 

 to one another in a regular order 

 throughout the series. 



I. Dry Pile. This apparatus, also 

 called ZambonVs pile, after its inventor, 

 differs from the hydro electric batteries 

 principally in this, that the presence of 

 the electromotive liquid is dispensed 

 with, its place being occupied by some 

 moist substance of low conducting power, 

 generally paper. It agrees, therefore, 

 mainly with the description given above, 

 and the term " dry " is inappropriate. 

 260 



2. Pile of two elements only. This 

 apparatus, also an invention of Zamboni, 

 consists of one metal and one interme- 

 diate conductor, either dry or moist. 

 These piles acquire at their poles a feeble 

 electrical tension, the metallic pole ex- 

 hibiting positive electricity in the dry 

 pile, and the pointed end of the metal 

 being positively electrified in the moist 

 pile. 



3. Secondary piles. These, sometimes 

 called Ritter's piles, consist of alternate 

 layers of homogeneous metallic plates, 

 between which some moist conducting 

 substance is interposed. When they 

 stand alone, no electromotive tension is 

 excited ; but they are capable of receiv- 

 ing a charge by being placed in the cir- 

 cuit of a powerful Voltaic battery, and of 

 thus acquiring, though in an inferior de- 

 gree, the properties of the battery itself. 



4. Pile of De Luc. An electrical 

 column, constructed of pieces of paper, 

 silvered on one side, and alternating 

 with thin leaves of zinc; the silvered 

 surfaces of the paper discs being always 

 in the same direction. 



PILEUS. The cap ; the botanical 

 term for the uppermost part of an agaric, 

 resembling an umbrella in form. 



PILI'DIUM. The orbicular hemisphe- 

 rical shield of lichens, the outside of 

 which changes to powder, as in calycium. 



PILOSITY {pilosus, hairy). A term 

 applied to that kind of hairiness in 

 plants, in which the hairs are long, soft, 

 and erect, as in the carrot. 



PI'MELITE. A green silicious earthy 

 substance, which accompanies chryso- 

 prase, and, like it, owes its colour to 

 oxide of nickel. It is a variety of stea- 

 tite, found at Kosemutz in Silesia. 



PINCHBECK. An alloy of copper, or 

 brass, and zinc, made in imitation of 

 gold. It is sometimes called tombac, 

 similor, and petit-or. 



PINIC ACID {pinus, the pine). An 

 acid obtained from rosin ; it may be re* 

 garded as an oxide of oil of turpentine. 



PINION. A wheel consisting of fewer 

 teeth than that which it drives. The 

 teeth of a pinion are called leaves. 



PI'NITE. A talcose substance, con- 

 sisting of silica, alumina, and oxide of 

 iron ; found in granite and in porphyry. 

 By Kirwan it is called micarelle. 



PINNATE LEAF {pinna, a feather, 

 a fish's fin). That form of leaf in which 

 simple leaflets are placed on each side of 

 a common petiole. The same modifica- 

 tions occur as in the palmate leaf, with 



