rminates in an ink-fed style which records the
pressure of the atmosphere on a moving ribbon. In all continuously
registering barometers, however, it is necessary, as a check, to make
eye-observations with a mercury standard barometer hanging near the
registering barometer from four to eight times daily.

See Marvin, _Barometers and the Measurement of Atmospheric Pressure_
(1901); and C. Abbe, _Meteorological Apparatus_ (1888). Reference may also
be made to B. Stewart and W. W. H. Gee, _Practical Physics_ (vol. i. 1901),
for the construction of standard barometers, their corrections and method
of reading.

BAROMETRIC LIGHT, the luminous glow emitted by mercury in a barometer tube
when shaken. It was first observed by Jean Picard, and formed the subject
of many experiments at the hands of Francis Hawksbee. The latter showed
that the Torricellian vacuum was not essential to the phenomenon, for the
same glow was apparent when mercury was shaken with air only partially
rarefied. The glow is an effect of the electricity generated by the
friction of the mercury and the air in the barometer tube.

BARON, MICHEL (1653-1729), French actor (whose family name originally was
Boyron), was born in Paris, the son of a leading actor (d. 1655) and of a
talented actress (d. 1662). At the age of twelve he joined the company of
children known as the _Petits Comediens Dauphins_, of which he was the
brightest star. Moliere was delighted with his talent, and with the king's
permission secured him for his own company. In consequence of a
misunderstanding with Moliere's wife, the actor withdrew from the
dramatist's company, but rejoined it in 1670, reappearing as Domitien in
Corneille's _Tite et Berenice_, and in his _Psyche_. He remained in this
company until Moliere's death. He then became a member of the company at
the Hotel de Bourgogne, and from this time until his retirement in 1691 was
undisputed master of the French stage, creating many of the leading roles
in Racine's tragedies, besides those in two of his own comedies, _L'Homme a
bonnes fortunes_ (1686), and _La Coquette_ (1687). He also wrote _Les
Enlevements_ (1685), _Le Debauche_ (1689), and translated and acted two
plays of Terence. In 1720 Baron reappeared at the Palais Royal, and his
activity on the stage was renewed in a multitude of parts. He died on the
22nd of December 1729.

His son ETIENNE MICHEL BARON (1676-1711) was also a fine actor, and left a
son and two daughters