on in
favour of a _savant_ whose works had thrown lustre on France, and whose
existence his government would regret to embitter." But the tenure of
office thus granted did not prove of long duration. Arago was now on his
death-bed, under a complication of diseases, induced, no doubt, by the
hardships and labours of his earlier years. In the summer of 1853 he was
advised by his physicians to try the effect of his native air, and he
accordingly set out for the eastern Pyrenees. But the change was
unavailing, and after a lingering illness, in which he suffered first
from diabetes, then from Bright's disease, complicated by dropsy, he
died in Paris on the 2nd of October 1853.

Arago's fame as an experimenter and discoverer rests mainly on his
contributions to magnetism and still more to optics. He found that a
magnetic needle, made to oscillate over nonferruginous surfaces, such as
water, glass, copper, &c., falls more rapidly in the extent of its
oscillations according as it is more or less approached to the surface.
This discovery, which gained him the Copley medal of the Royal Society
in 1825, was followed by another, that a rotating plate of copper tends
to communicate its motion to a magnetic needle suspended over it
("magnetism of rotation"). Arago is also fairly entitled to be regarded
as having proved the long-suspected connexion between the aurora
borealis and the variations of the magnetic elements.

In optics we owe to him not only important optical discoveries of his
own, but the credit of stimulating the genius of A.J. Fresnel, with
whose history, as well as with that of E.L. Malus and of Thomas Young,
this part of his life is closely interwoven. Shortly after the beginning
of the 19th century the labours of these three philosophers were shaping
the modern doctrine of the undulatory theory of light. Fresnel's
arguments in favour of that theory found little favour with Laplace,
Poisson and Biot, the champions of the emission theory; but they were
ardently espoused by Humboldt and by Arago, who had been appointed by
the Academy to report on the paper. This was the foundation of an
intimate friendship between Arago and Fresnel, and of a determination to
carry on together further researches in this subject, which led to the
enunciation of the fundamental laws of the polarization of light known
by their names (see POLARIZATION). As a result of this work Arago
constructed a _polariscope_, which he used for some inte