By some beautiful experiments, MM.

Violle and Vautier have clearly shown that any disturbance in the air melts somewhat quickly into a single wave of given form, which is propagated to a distance, while gradually becoming weaker and showing a constant speed which differs little in dry air at 0 deg.

C.from 331.36 metres per second.

In a narrow pipe the influence of the walls makes itself felt and produces various effects, in particular a kind of dispersion in space of the harmonics of the sound.

This phenomenon, according to M.Brillouin, is perfectly explicable by a theory similar to the theory of gratings..