PEN 



552 



PEN 



row banner displayed from the mast-head 

 of a ship of war, :md usually terminated 

 in two points, called the swallow's tail 

 written also pennant, and Fr. pennon. 



PEN'DENT BRIDOB. A wooden bridge 

 with abutments only at the ends, and 

 supported by posts and pillars. 



PENDEN'TE LX'TE. During the dispute 

 while the suit is undetermined. 



PENDEK'TIVE. In architecture, the 

 whole body of a vault suspended out of 

 the perpendicular of the walls. Penden- 

 tii-e bracketing, or core bracketing, 

 springing from the rectangular walls of 

 an apartment upwards to the ceiling, and 

 forming the horizontal part of the ceil- 

 ing into a circle or ellipse. Pendentive 

 cradling is the timber- work for sustain 

 ing the lath and plaster in vaulted 

 ceilings. 



PEN'DULUM. In mechanics, any heavy 

 body so suspended that it may vibrate 

 about some fixed point by the action of 

 gravity. The vibrations of a pendulum 

 are called its oscillations; the time of each 

 being counted from the time of its descent 

 from the highest point on one side till it 

 attains the highest point on the opposite 

 side. The point A, about which the pen- 

 dulum moves, is called the point of suspen- 

 sion or centre of motion, and the line PQ, 



B 



PENDULUM. 



parallel to the horizon, is the axis of oscil- 

 lation. Pendulums receive different de- 

 nominations, according to the materials 

 of which they are composed, or the pur- 

 poses they are intended to answer. A 

 single weight attached by a string, &c., is 

 called a simple pendulum ; but, in order to 

 counteract the effects of variations of 

 Temperature upon the suspending me- 

 dium, several contrivances have been 

 adopted, under the name of compensation 

 pendulums ; these again take particular 

 names, according to their form and ma- 

 terials, as the gridiron pendulum, the mer- 

 curial pendulum, the lever pendulum, &c. 

 The gridiron pendulum is eomposed of 

 any odd number of rods, so connected that 

 the expansion or contraction of the one 

 set of them is counteracted by that of the 

 other. The mercurial pendulum consist* 



of one rod with a vessel containing mer- 

 cury at the lower end, so adjusted in 

 quantity that whatever alterations tak 







GHIDIROH MERCURIAL 



PENDULUM. PENDULUM. 



place in the length of the pendulum, the 

 centre of oscillation remains the same, 

 the mercury ascending when the rod de- 

 scends, and vice versa. Our clocks are 

 nothing more than pendulums, with 

 wheel work attached, to register the 

 number of vibrations, and with a weight 

 or spring having force enough to coun- 

 teract the retarding effects of friction and 

 the resistance of the air; and when the 

 pendulum is so adjusted as to beat or 

 ribrate 60 X 60 = 3600 in an hour, 

 t is called a seconds pendulum, and 

 its length at London is thirty-nine and 

 one-eighth inches. This length varies with 

 the latitude, in consequence of the varia- 

 tion of the force of gravity. 



PEN'ETRALE. The most sacred part of 

 in ancient temple, which usually con- 

 fined an altar, dedicated to Jupiter Her- 

 cceus,the supposed protector of its sanctity. 



PEN'ETHALIA. Small chapels in the in- 

 nermost part of Roman houses, dedicated 

 :o the Penates, &c. , in which was deposited 

 ivhatever was deemed most valuable. 



PEN'GUIN. In ornithology, a name first 

 given by the Dutch to the Aptenodytes 

 f the south, to indicate the oily nature 

 )f their fat. See APTENODYTES. 



PENICIL'LATE, Lat. penciliium. a pencil, 

 n zoology, when a part supports bundles 

 )f diverging hair. 



PENITENTIARY. 1. A presbyter in the 

 ancient Christian church, whose business 



as to hear confessions, and avrard pri- 

 vate penance, in cases where it was un- 



advisable to censure publicly. 2. An 



jfflce at the Court of Rome, in which are 

 mined and delivered out the secret 

 bulls, graces, and dispensations, relating 

 to cases of conscience. 3. An officer in 



