On the recommendation of
Joseph Banks he went to
London where he befriended the botanist
James Edward Smith and the surgeon
John Hunter. He began lecturing in pharmacy and mineralogy in London. His first stay in Britain was seven years, approximately 1786 to 1793. He made a briefer return as a traveling companion to
Caspar Voght in 1794/95. In 1794 he was elected a Fellow of the
Royal Society of London, his proposer being
Joseph Banks. In 1795 he was elected a Fellow of the
Royal Society of Edinburgh during his tour of
Scotland. His proposers were
John Rotherham,
Andrew Duncan, the elder, and
William Wright. He was also a member of the
Linnean Society. He returned to the Altona region in 1796 to work as a pharmacist on the Baron's estate at
Flottbek where the Baron built him a laboratory. Later in 1796 he accompanied the Baron's friend,
Georg Sieveking on his trip to
Paris, which was then still reeling from the
French Revolution. In 1798 he accompanied
Johann Georg Busch to the
Harz in east Saxony, to Brunswick,
Göttingen and
Hanover. Around 1822/23 he spent some time in
Copenhagen. On his return he settled in
Hamburg. == Death ==