rom this place
would have occasioned a weary stay of three months; Arago, therefore,
set out for it by land under conduct of a Mahommedan priest, and reached
it on Christmas day. After six months' stay in Algiers he once again, on
the 21st of June 1809, set sail for Marseilles, where he had to undergo
a monotonous and inhospitable quarantine in the lazaretto, before his
difficulties were over. The first letter he received, while in the
lazaretto, was from A. von Humboldt; and this was the origin of a
connexion which, in Arago's words, "lasted over forty years without a
single cloud ever having troubled it."

Through all these vicissitudes Arago had succeeded in preserving the
records of his survey; and his first act on his return home was to
deposit them in the Bureau des Longitudes at Paris. As a reward for his
adventurous conduct in the cause of science, he was in September 1809
elected a member of the Academy of Sciences, in room of J.B.L. Lalande,
at the remarkably early age of twenty-three, and before the close of the
same year he was chosen by the council of the polytechnic school to
succeed G. Monge in the chair of analytical geometry. About the same
time he was named by the emperor one of the astronomers of the Royal
Observatory, which was accordingly his residence till his death, and it
was in this capacity that he delivered his remarkably successful series
of popular lectures on astronomy, which were continued from 1812 to
1845.

In 1816, along with Gay-Lussac, he started the _Annales de chimie et de
physique_, and in 1818 or 1819 he proceeded along with Biot to execute
geodetic operations on the coasts of France, England and Scotland. They
measured the length of the seconds-pendulum at Leith, and in Unst, one
of the Shetland isles, the results of the observations being published
in 1821, along with those made in Spain. Arago was elected a member of
the Board of Longitude immediately afterwards, and contributed to each
of its _Annuals_, for about twenty-two years, important scientific
notices on astronomy and meteorology and occasionally on civil
engineering, as well as interesting memoirs of members of the Academy.

In 1830, Arago, who always professed liberal opinions of the extreme
republican type, was elected a member of the chamber of deputies for the
Lower Seine, and he employed his splendid gifts of eloquence and
scientific knowledge in all questions connected with public education,
the rewards of in