n and BC as axis of x is x^2y^2 = (a +
y)^2 (b^2 -y^2). Both branches belong to the same curve and are included
in this equation. Three forms of the curve have to be distinguished
according to the ratio of a to b. If a be less than b, there will be a
node at O and a loop below the initial point (curve 1 in the figure); if
a equals b there will be a cusp at O (curve 2); if a be greater than b
the curve will not pass through O, but from the cartesian equation it is
obvious that O is a conjugate point (curve 3). The curve is symmetrical
about the axis of y and has the axis of x for its asymptote.

CONCIERGE (a French word of unknown origin; the Latinized form was
_concergius_ or _concergerius_), originally the guardian of a house or
castle, in the middle ages a court official who was the custodian of a
royal palace. In Paris, when the _Palais de la Cite_ ceased about 1360
to be a royal residence and became the seat of the courts of justice,
the _Conciergerie_ was turned into a prison. In modern usage a
"concierge" is a hall-porter or janitor.

CONCINI, CONCINO (d. 1617), COUNT DELLA PENNA, MARSHAL D'ANCRE, Italian
adventurer, minister of King Louis XIII. of France, was a native of
Florence. He came to France in the train of Marie de' Medici, and
married the queen's lady-in-waiting, Leonora Dori, known as Galigai. The
credit which his wife enjoyed with the queen, his wit, cleverness and
boldness made his fortune. In 1610 he had purchased the marquisate of
Ancre and the position of first gentleman-in-waiting. Then he obtained
successively the governments of Amiens and of Normandy, and in 1614 the
baton of marshal. From then first minister of the realm, he abandoned
the policy of Henry IV., compromised his wise legislation, allowed the
treasury to be pillaged, and drew upon himself the hatred of all
classes. The nobles were bitterly hostile to him, particularly Conde,
with whom he negotiated the treaty of Loudun in 1616, and whom he had
arrested in September 1616. This was done on the advice of Richelieu,
whose introduction into politics was favoured by Concini. But Louis
XIII., incited by his favourite Charles d'Albert, due de Luynes, was
tired of Concini's tutelage. The baron de Vitry received in the king's
name the order to imprison him. Apprehended on the bridge of the Louvre,
Concini was killed by the guards on the 24th of April 1617. Leonora was
accused of sorcery and sent to the stake in the same year.