nomer, but astronomy was only one of the many fields of science in
which he shone. Surely something out of the ordinary was to be expected
of the man who could "repeat the AEneid of Virgil from the beginning
to the end without hesitation, and indicate the first and last line of
every page of the edition which he used." Something was expected, and he
fulfilled these expectations.

In early life he devoted himself to the study of theology and the
Oriental languages, at the request of his father, but his love of
mathematics proved too strong, and, with his father's consent, he
finally gave up his classical studies and turned to his favorite study,
geometry. In 1727 he was invited by Catharine I. to reside in St.
Petersburg, and on accepting this invitation he was made an associate
of the Academy of Sciences. A little later he was made professor of
physics, and in 1733 professor of mathematics. In 1735 he solved a
problem in three days which some of the eminent mathematicians would not
undertake under several months. In 1741 Frederick the Great invited him
to Berlin, where he soon became a member of the Academy of Sciences and
professor of mathematics; but in 1766 he returned to St. Petersburg.
Towards the close of his life he became virtually blind, being obliged
to dictate his thoughts, sometimes to persons entirely ignorant of the
subject in hand. Nevertheless, his remarkable memory, still further
heightened by his blindness, enabled him to carry out the elaborate
computations frequently involved.

Euler's first memoir, transmitted to the Academy of Sciences of Paris
in 1747, was on the planetary perturbations. This memoir carried off the
prize that had been offered for the analytical theory of the motions of
Jupiter and Saturn. Other memoirs followed, one in 1749 and another in
1750, with further expansions of the same subject. As some slight
errors were found in these, such as a mistake in some of the formulae
expressing the secular and periodic inequalities, the academy proposed
the same subject for the prize of 1752. Euler again competed, and won
this prize also. The contents of this memoir laid the foundation for
the subsequent demonstration of the permanent stability of the planetary
system by Laplace and Lagrange.

It was Euler also who demonstrated that within certain fixed limits
the eccentricities and places of the aphelia of Saturn and Jupiter are
subject to constant variation, and he calculated that after a