n form without
content (e.g. formal logic, the laws of thought). The simple fact at the
bottom of the controversy is that in all empirical knowledge there is an
intellectual element, without which there is no correlation of empirical
data, and every judgment, however simple, postulates a correlation of
some sort if only that between the predicate and its contradictory.

APRON (a corruption arising from a wrong division of "a napron" into "an
apron," from the Fr. _naperon, napperon_, a diminutive of _nappe_, Lat.
_mappa_, a napkin), an article of costume used to protect the front of
the clothes. It forms part of the ceremonial dress of Freemasons. The
"apron" worn by church dignitaries is a shortened cassock (q.v.). The
word has many technical uses, as for the protecting slope in front of
the sill of dock-gates, or at the foot of weirs.

APSARAS, in Hindu mythology, a female spirit of the clouds and waters.
In the Rig-Veda there is one Apsaras, wife of Gandharva; in the later
scriptures there are many Apsaras who act as the handmaidens of Indra
and dance before his throne. They are able to change their form, and
specially rule over the fortunes of gaming. One of their duties is to
guide to paradise the heroes who fall in battle, whose wives they then
become. They are distinguished as _daivika_ ("divine") or _laukika_
("worldly").

APSE (Gr. [Greek: apsis], a fastening, especially the felloe of a wheel;
Lat. _absis_), in architecture, a semicircular recess covered with a
hemispherical vault. The term is applied also to the termination to the
choir, transept or aisle of any church which is either semicircular or
polygonal in plan, whether vaulted or covered with a timber roof; a
church is said to be "apsidal" when it terminates in an apse.

The earliest example of an apse is found in the temple of Mars Ultor at
Rome (2 B.C.), and it formed afterwards the favourite feature
terminating the rear of any temple, and one which gave importance to the
statue of the deity to whom the temple was dedicated. Its use by the
Romans was not confined to the temples, as it is found in the palaces on
the Palatine Hill, the great Thermae (Baths) and other monuments. In the
civil basilicas the apse was screened off by columns, and constituted
the court of justice. In the Ulpian (Trajan's) Basilica the apses at
each end were of such great dimensions as to come better under the
definition of hemicycles (q.v.). In these apse