ause of dreams is the
stimulation of the brain by the internal regions of the organism through
the sympathetic nervous system. These impressions the mind afterwards
works up into quasi-realities by means of its forms of space, time,
causality, &c.

BIBLIOGRAPHY.--For full lists of books and articles see J. M. Baldwin's
_Dictionary of Philosophy_, bibliography volume (1906), and S. de
Sanctis, _I Sogni_, also translated in German with additions as _Die
Traume_. Important works are--Binz, _Uber den Traum_, Giessler _Aus den
Tiefen des Traumlebens_, Maury, _Le Sommeil et les reves_, Radestock,
_Schlaf und Traum_, Tessie, _Les Reves_, Spitta, _Schlaf und
Traumzustande_. For super-normal dreams see F. W. H. Myers, _Human
Personality_, vol i, and _Proc S P R_ viii 362. For voluntary dreams see
_Proc. S P R_ iv 241, xvii. 112. On prophetic dreams see _Monist_, xi
161, _Bull. Soc. Anth._ (Paris, 1901), 196, (1902), 228, _Rev. de
synthese historique_ (1901), 151, &c. On incubation see Deubner, _De
incubatione_, Maury, La Magie. On the dreams of American Indians see
_Handbook of American Indians_ (Washington, 1907), s v "Dreams" and
"Manito." On the interpretation of dreams see Freud, _Die Traumdeutung_.
Other works are F. Greenwood, _Imagination in Dreams_, Hutchinson,
_Dreams and their Meanings_. (N. W. T.)

DREDGE AND DREDGING. The word "dredge" is used in two senses. (1) From
Mid. Eng. _dragie_, through Fr. _dragee_, from Gr. [Greek: tragemata],
sweetmeats, it means a confection of sugar formed with seeds, bits of
spice or medicinal agents. The word in this sense is obsolete, but
survives in "dredger," a box with a perforated top used for sprinkling
such a sugar-mixture, flour or other powdered substance. "Dredge" is
also a local term for a mixed crop of oats and barley sown together
("maslin" or "meslin," cf. Fr. _dragee_), and in mining is applied to
ore of a mixed value. (2) Connected with "drag," or at least derived
from the same root, dredge or dredger is a mechanical appliance for
collecting together and drawing to the surface ("dredging") objects and
material from the beds of rivers or the bottom of the sea. In the
following account the operations of dredging in this sense are discussed
(1) as involved in hydraulic engineering, (2) in connexion with the work
of the naturalist in marine biology.

1. HYDRAULIC ENGINEERING

Dredging is the name given by engineers to the process of excavating
materials und