ther small tank, with a period of rest between each stroke;
the motive power is obtained through a simple bucket-and-siphon
arrangement worked by the overflow from other tanks. This apparatus
(first used at the Plymouth Laboratory of the Marine Biological
Association in 1897, and since introduced into similar institutions), by
causing slight eddies in the water, keeps the floating fauna in
suspension, and has proved very successful in rearing larvae and in
similar work. (G. H. Fo.)

AQUARIUS (the "Water-bearer" or "Cup-bearer"), in astronomy, the
eleventh sign of the zodiac (q.v.), situated between Capricornus and
Pisces. Its symbol is [symbol], representing part of a stream of water,
probably in allusion to the fact that when the sun is in this part of
the heavens (January, February) the weather is rainy. It is also a
constellation mentioned by Eudoxus (4th century B.C.) and Aratus (3rd
century B.C.); Ptolemy catalogued forty-five stars, Tycho Brahe
forty-one, Hevelius forty-seven. [Zeta] _Aquarii_ is a well-defined
binary, having both components of the fourth magnitude; it is probably
of long period.

AQUATINT (Lat. _aqua_, water, and _tincta_, dyed), a kind of etching
(q.v.) which imitates washes with a brush. There are many ways of
preparing a plate for aquatint, the following being recommended by P.G.
Hamerton. Have three different solutions of rosin in rectified alcohol,
making them of various degrees of strength, but always thin enough to be
quite fluid, the weakest solution being almost colourless. First pour
the strongest solution on the plate. When it dries it will produce a
granulation; and you may now bite as in ordinary etching for your darker
tones, stopping out what the acid is not to operate upon, or you may use
a brush charged with acid, perchloride of iron being a very good mordant
for the purpose. After cleaning the plate, you proceed with the weaker
solutions in the same way, the weakest giving the finest granulation for
skies, distances, &c. The process requires a good deal of stopping-out,
and some burnishing, scraping, &c., at last. Aquatint may be effectively
used in combination with line etching, and still more harmoniously with
soft ground etching in which the line imitates that of the lead pencil.

AQUAVIVA, CLAUDIO (1542-1615), fifth general of the Jesuits, the
youngest son of the duke d'Altri, was born at Naples. He joined the
Jesuits at Rome in 1567, and his high adm