Part 160

The time of oscillation of a pendulum is independent of the arc of vibration, provided this arc be small.

Ballistic pendulum. See under Ballistic. -- Compensation pendulum, a clock pendulum in which the effect of changes of temperature of the length of the rod is so counteracted, usually by the opposite expansion of differene metals, that the distance of the center of oscillation from the center of suspension remains invariable; as, the mercurial compensation pendulum, in which the expansion of the rod is compensated by the opposite expansion of mercury in a jar constituting the bob; the gridiron pendulum, in which compensation is effected by the opposite expansion of sets of rodsof different metals. -- Compound pendulum, an ordinary pendulum; -- so called, as being made up of different parts, and contrasted with simple pendulum. -- Conical or Revolving, pendulum, a weight connected by a rod with a fixed point; and revolving in a horizontal cyrcle about the vertical from that point. -- Pendulum bob, the weight at the lower end of a pendulum. -- Pendulum level, a plumb level. See under Level. -- Pendulum wheel, the balance of a watch. -- Simple or Theoretical, pendulum, an imaginary pendulum having no dimensions except length, and no weight except at the center of oscillation; in other words, a material point suspended by an ideal line.

||Pe*nel"o*pe (p*nl"*p), n. [From. L. Penelope, the wife of Ulysses, ||the hero of the Odyssey, Gr. Phnelo`ph.] (Zoˆl.) A genus of ||curassows, including the guans.

Pen`e*tra*bil"i*ty (?), n. [Cf. F. pÈnÈtrabilitÈ.] The quality of being penetrable; susceptibility of being penetrated, entered, or pierced. Cheyne.

Pen"e*tra*ble (?), a. [L. penetrabilus: cf. F. pÈnÈtrable.] Capable of being penetrated, entered, or pierced. Used also figuratively.

And pierce his only penetrable part.

Dryden.

I am not made of stones, But penetrable to your kind entreats.

Shak.

-- Pen"e*tra*ble*ness, n. -- Pen"e*tra*bly, adv.

Pen"e*trail (?), n. Penetralia. [Obs.] Harvey.

||Pen`e*tra"li*a (?), n. pl. [L., fr. penetralis penetrating, internal. ||See Penetrate.] 1. The recesses, or innermost parts, of any thing or ||place, especially of a temple or palace.

2. Hidden things or secrets; privacy; sanctuary; as, the sacred penetralia of the home.

{ Pen"e*trance (?), Pen"e*tran*cy (?), } n. The quality or state of being penetrant; power of entering or piercing; penetrating power of quality; as, the penetrancy of subtile effluvia.

Pen"e*trant (?), a. [L. penetrans, p. pr. of penetrare: cf. F. pÈnÈtrant.] Having power to enter or pierce; penetrating; sharp; subtile; as, penetrant cold. "Penetrant and powerful arguments." Boyle.

Pen"e*trate (?), v. t. [imp. & p. p. Penetrated (?); p. pr. & vb. n. Penetrating.] [L. penetratus, p. p. of penetrare to penetrate; akin to penitus inward, inwardly, and perh. to pens with, in the power of, penus store of food, innermost part of a temple.] 1. To enter into; to make way into the interior of; to effect an entrance into; to pierce; as, light penetrates darkness.

2. To affect profoundly through the senses or feelings; to touch with feeling; to make sensible; to move deeply; as, to penetrate one's heart with pity. Shak.

The translator of Homer should penetrate himself with a sense of the plainness and directness of Homer's style.

M. Arnold.

3. To pierce into by the mind; to arrive at the inner contents or meaning of, as of a mysterious or difficult subject; to comprehend; to understand.

Things which here were too subtile for us to penetrate.

Ray.

Pen"e*trate, v. i. To pass; to make way; to pierce. Also used figuratively.

Preparing to penetrate to the north and west.

J. R. Green.

Born where Heaven's influence scarce can penetrate.

Pope.

The sweet of life that penetrates so near.