The African Association sent him to the University of Göttingen to study Arabic and otherwise prepare for an expedition from the east into the unknown regions of North Africa.
He then spoke, but indifferently, both Arabic and Turkish, and he was accompanied as servant and interpreter by Joseph Freudenburg, a German convert to Islam, who had thrice made the pilgrimage to Mecca.
The British consul at Tripoli heard from a source believed to be trustworthy that about June 1803 Jusef (Hornemann's Muslim name) was at Caina, i.e. Katsina, in Northern Nigeria, in good health and highly respected as a marabout.
Hornemann was the first European in modern times to traverse the north-eastern Sahara, and up to 1910 no other explorer had followed his route across the Jebel-es-Suda from Aujila to Temissa.
A French translation of the English work, made by order of the First Consuls and augmented with notes and a memoir on the Egyptian oases by L. Langlès, was published in Paris in the following year.