but little
help. Mirabeau, however, with his assistance, prepared a speech against
slavery, to be delivered before the National Assembly, and the Marquis
de la Fayette entered enthusiastically into his views. During this visit
Clarkson met a deputation of negroes from Santo Domingo, who had come to
France to present a petition to the National Assembly, desiring to be
placed on an equal footing with the whites; but the storm of the
Revolution permitted no substantial success to be achieved. Soon after
his return home he engaged in a search, the apparent hopelessness of
which finely displays his unshrinking laboriousness and his passionate
enthusiasm. He desired to find some one who had himself witnessed the
capture of the negroes in Africa; and a friend having met by chance a
man-of-war's-man who had done so, Clarkson, though ignorant of the name
and address of the sailor, set out in search of him, and actually
discovered him. His last tour was undertaken in order to form
anti-slavery committees in all the principal towns. At length, in the
autumn of 1794, his health gave way, and he was obliged to cease active
work. He now occupied his time in writing a _History of the Abolition of
the Slave Trade_, which appeared in 1808. The bill for the abolition of
the trade became law in 1807; but it was still necessary to secure the
assent of the other powers to its principle. To obtain this was, under
pressure of the public opinion created by Clarkson and his friends, one
of the main objects of British diplomacy at the Congress of Vienna, and
in February 1815 the trade was condemned by the powers. The question of
concerting practical measures for its abolition was raised at the
Congress of Aix-la-Chapelle in 1818, but without result. On this
occasion Clarkson personally presented an address to the emperor
Alexander I., who communicated it to the sovereigns of Austria and
Prussia. In 1823 the Anti-Slavery Society was formed, and Clarkson was
one of its vice-presidents. He was for some time blind from cataract;
but several years before his death on the 26th of September 1846, his
sight was restored.

Besides the works already mentioned, he published the _Portraiture of
Quakerism_ (1806), _Memoirs of William Penn_ (1813), _Researches,
Antediluvian, Patriarchal and Historical_ (1836), intended as a
history of the interference of Providence for man's spiritual good,
and _Strictures_ on several of the remarks concerning himse