OCR Text |
Show Vibrations Make Sound. H Anything strotched la likely to bo H thrown Into vibration, or nindo to H tremble, by tho forco nf tho'nlr blow- H lug against It If It vlbrntes so fast' H as to producu tho air waves that our H enr can hear, then that la what we H call .sound. This la what happens to H the, telegraph wires uhen they hum; H and If we put our hnml on tho tolc-. H 'grnph pole wo shall fed thnt the wires H vibrate strongly cmugi to set tlio H whole pole to irt'tiibllng, too. When H tlr. nlr Is quite still you will not hear H tht telegraph tines humming, M |