In 1809, after his defeat by Sir John Moore, he invadedPortugal and took Oporto, but, busying himself with the political settlement of his conquests in the French interests and, as he hoped, for his own ultimate benefit as a possible candidate for the throne, he neglected to advance upon Lisbon, and was eventually dislodged from Oporto by Sir Arthur Wellesley, making a painful and almost disastrous retreat over the mountains.
In September 1665 we find Oldenburg twitting him with having turned from philosophy to theology and busying himself with angels, prophecy and miracles.
For some years the world heard nothing from him; he was at Farringford, busying himself with the Arthurian traditions.
He spent about three months in the Low Countries, and in March 1737 returned to Cirey, and continued writing, making experiments in physics (he had at this time a large laboratory), and busying himself with iron-founding, the chief industry of the district.
In 1850 he returned to GÃ¶ttingen and began to prepare his doctor's dissertation, busying himself meanwhile with "Naturphilosophic" and experimental physics.