THE present work lays no claim to originality. It
is, essentially, the able and finished treatise, written
by Sir John Herschel for the Encyclopedia Metropoli-
tana, adapted to the purposes of instruction, with
such changes as are demanded by some later inves-
tigations. Thus the analysis of the Vibrations of
Plates, in Part II., Chapter V., is taken from
Wheatstone's Memoir in the London Philosophical
Transactions for 1833; the whole of Part III., Chap-
ter III., is from Faraday's Memoir in the Trans-
actions for 1831; and Chapters IV. and V. of Part III.
are almost entirely rewritten from other sources, such
as Milne-Edwards's Elements of Zoology; Breschet's
Anatomy and Physiology of the Ear, in the Annales
des Sciences Naturelles of Paris for 1833; Sir Charles
Bell on the Organs of the Human Voice, in the Lon-
don Philosophical Transactions for 1832; Willis
on the Mechanism of the Larynx, in the Cambridge
Philosophical Transactions for 1833; Bennati's Mech-
anism of the Human Voice; and Rush's Treatise
on the Human Voice; combined with some original
remarks.