Jean Picard, a French astronomer, born in La Fleche, July 21, 1620, died in 1682. He assisted Gassendi in observing the solar eclipse of Aug. 25, 1645, was appointed in 1655 his successor in the chair of astronomy at the college de France, and became in 1666 one of the original members of the academy of sciences. His introduction of several improvements in practical geometry greatly increased the exactness of scientific observations. In connection with Azout he reinvented the micrometer, was the first to apply a telescope in the measurement of angles, devised methods of verification in astronomical investigations, made in 1669-'71 the first exact measurement of a degree of the meridian between Amiens and Malvoisine, and pointed out the twofold phenomena of nutation and aberration, afterward explained by Bradley. He also introduced the modern method of determining the right ascension of the stars by employing a pendulum to note the instant of their meridional passages. In order to make the observations of Tycho Brahe more accessible to astronomers, he visited Ura-nienborg in 1671 to ascertain the latitude and longitude of the observatory at that place.
He welcomed to France the celebrated Cassini; and when, through his exertions, the observatory of Paris was established, he saw without envy the Italian philosopher promoted to the directorship of an institution of which he himself was the father. He wrote valuable works.