A liquid vein descending through a round hole in the bottom of a tin
vessel exhibits two distinct portions, the one steady and limpid, the
other unsteady and apparently turbid. The flash of an electric spark in
a dark room instantly resolves the turbid portion into isolated drops.
Experiments made in 1849 with such a jet directed my attention to the
origin of the sound of agitated water. When the smoke is projected
from the lips of a tobacco-smoker, a little explosion usually occurs,
which is chiefly due to the sudden bursting of the film of saliva
connecting both lips. An inflated bladder bursts with an explosion as
loud as a pistol-shot. Sound to some extent always accompanies the
sudden liberation of compressed air, and this fact is also exhibited in
the deportment of a water-jet. If the surface of water into which the
jet falls intersect its limpid portion, the jet enters _silently_, and
no bubbles are produced. If the surface cut the turbid portion of the
jet, bubbles make their appearance with an accompaniment of sound. The
very nature of the sound pronounces its origin to be the bursting of
the bubbles; and to the same cause the murmur of streams and the sound
of breakers appear to be almost exclusively due. The impact of water
against water is a comparatively subordinate cause of the sound, and
could never of itself occasion the ‘babble’ of a brook or the musical
roar of the ocean.--_Philosophical Magazine_, February 1857.