became one of the best-known men of science of
his day, and whose services were eagerly sought
by the rulers of Europe, began life as a foundling,
having been exposed in one of the markets of
Paris. The sickly infant was adopted and cared for
in the family of a poor glazier, and treated as a member
of the family. In later years, however, after the
foundling had become famous throughout Europe, his
mother, Madame Tencin, sent for him, and acknowledged
her relationship. It is more than likely that
the great philosopher believed her story, but if so he
did not allow her the satisfaction of knowing his belief,
declaring always that Madame Tencin could "not
be nearer than a step-mother to him, since his mother
was the wife of the glazier."

D'Alembert did much for the cause of science by his
example as well as by his discoveries. By living a
plain but honest life, declining magnificent offers of
positions from royal patrons, at the same time refusing
to grovel before nobility, he set a worthy example to
other philosophers whose cringing and pusillanimous
attitude towards persons of wealth or position had
hitherto earned them the contempt of the upper
classes.

His direct additions to astronomy are several, among
others the determination of the mutation of the axis
of the earth. He also determined the ratio of the attractive
forces of the sun and moon, which he found