PIS 



PIT 



Dioecia Pentandr'a class and order. Na- 

 tural order of Amentacese. Terebintacese, 

 Jussieu. Essential character : male an 

 ament ; calyx five-cleft ; corolla none ; 

 female distinct; calyx trifid ; corolla none : 

 styles two ; drupe one-seeded. There are 

 six species, among which we shall notice 

 the P. lentiscus, mastick tree : it is about 

 eighteen or tventy feet in height, the 

 trunk is covered with a greyish bark, the 

 branches are numerous, the leaves have 

 three or four pairs of small leaflets, of a 

 lucid green on their upper, bui pale on 

 their under side ; the male flowers come 

 out in loose clusters from the sides of the 

 branches, of an herbaceous colour, ap- 

 pearing in May, and soon falling off; they 

 are generally on different plants from the 

 fruits, which also grow in clusters, and 

 are small berries of a black colour when 

 ripe. 



PISTAZ1TE, in mineralogy, is of pista- 

 chio green, passing sometimes into olive 

 green, and blackish green. It occurs mas- 

 sive and crystallized. Internally it is shin- 

 ing ; fracture sometimes foliated, some- 

 times narrow, parallel and stellular, diverg. 

 ing radiated. It is hard, easily frangible, 

 and not very heavy It occurs in beds in 

 primitive mountains in Norway, Germany, 

 and France. 



PISTIA, in botany, a genus of the Mo- 

 nadelphia Octandria class and order. Na- 

 tural order of Miscellanex. Hydrochari- 

 des, Jussieu. Essential character : calyx 

 none; corolla one-petalled, tongue-shaped, 

 entire ; anthers six or eight, placed on the 

 filament ; style one ; capsule one-celled 

 at the bottom of the corolla. There is but 

 one species, viz. P. stratiotes, a native of 

 Asia, Africa, and South America, in stag- 

 nant waters. 



PISTILLA, in botany. See BOTANY. 



PISTOLE, a gold coin struck in Spain, 

 and in several parts of Italy, Switzerland, 

 &c. equal to about ten shillings and six- 

 pence of our money. 



PISTON, in pump-work, is a short cy- 

 linder of metai, or other solid substance, 

 fitted exactly to the cavity of the barrel or 

 body of the pump. There are two kinds of 

 pistons used in pumps, the one with a 

 valve, and the other without a valve, call- 

 ed a forcer. 



PISUM, in botany, pea, a genus of the 

 Diadelphia Decandria class and order. 

 Natural order of Papilionacex, or Legumi- 

 nosse. Essential character : style triangu- 

 lar, above keeled, pubescent ; calyx has 

 the two upper segments shorter. There 

 are three species, of which we shall men. 

 tion P. sativum, the common pea. Many 



varieties of this are cultivated in England ; 

 the Hot spurs and Hastings have their 

 names from their coming to bear early in 

 the season ; new varieties of these are 

 raised almost every year, which, because 

 they differ in some slight particular, are 

 sold at an advanced price, having fre- 

 quently the names of the persons who 

 raised them, or the place where they first 

 grew. These varieties are not permanent, 

 and, without the greatest care, will soon 

 degenerate. 



PITCAIRXIA, in botany, a genus of the 

 Hexandria Monogynia class and order. 

 Natural order of Coronarise. Bromelis, 

 Jussieu. Essential character: calyx three- 

 leaved or three-parted, half superior ; co- 

 rolla three-petalled, with a scale at the 

 base of each petal ; stigmas three, con- 

 torted ; capsule three, opening inwards ; 

 seeds winged. There are three species, 

 natives of the West Indies. 



PITCH, a tenaceous oily substance, 

 drawn chiefly from pines and furs, and 

 used in shipping, medicine, and various 

 other arts : or it is more properly tar, in- 

 spissated by boiling it over a slow fire. 

 The method of procuring the tar is, by 

 cleaving the trees into small billets, which 

 are laid in a furnace that has two aper- 

 tures, through one of which the fire is 

 put, and through the other the pitch is 

 gathered, which, oozing from the wood, 

 runs along the bottom of the furnace into 

 places made 10 receive it ; when the 

 smoke, which is here very thick, gives 

 it its blackness ,- this is called tar, which, 

 on being boiled, to consume more of its 

 moisture, becomes pitch. There is an- 

 other method of drawing pitch, used in 

 the Levant : a pit is dug in the ground, 

 two ells in diameter at the top, but con- 

 tracting as it grows deeper ; this is filled 

 with branches of pine, cloven into shivers ; 

 the wood at the top of the pit is then set 

 on fire, and burning downwards, the tar 

 runs from it, out of a hole made in the 

 bottom ; and this is boiled, as above, to 

 give it the consistence of pitch. See TUR- 

 PENTINE. 



PITCH, in music, the acuteness or 

 gravity ot any particular sound, or of the 

 tuning of any instrument. A sound less 

 acute than some other sound with which 

 it is compared, is said to be of a lower 

 pitch than that other sound; and vice 

 versa. 



PITCHING, in naval affairs, is the ver- 

 tical vibration which the length of a ship 

 makes about her centre of gravity, or the 

 motion by which she plunges her head 

 and after part alternately into the hollow 



