The two Frenchmen had preluded their discoveries by an excursion to the oasis of Siwâh. At the end of 1819 they left Fayum with a few companions, and entered the Libyan desert. In fifteen days, and after a brush with the Arabs, they reached Siwâh, having on their way taken measurements of every part of the temple of Jupiter Ammon, and determined, as Browne had done, its exact geographical position.