ABSTRACT
Lyell’s expedition through Spanish and French Catalonia in the summer of 1830 is here documented from his field notebooks—a source still unexplored. As a result, the chronology, his itinerary and his activities are specified day by day. Several previously unknown aspects are revealed, especially Lyell’s unpublished geological observations on Tertiary basins, his contacts with native naturalists and the role of chance in choosing his itinerary. An attempt to reconstruct two of Lyell’s cross-sections through the Pyrenees has been made. The further influence of his papers on Spanish and French geologists is also discussed. 
