Complex sentence: Between 1866 and 1872 he delivered a series of free lectures which he described in "A Synopsis of Fourteen Popular Lectures"; and in 1871 he gave a lecture to the British Archæological Association on "Art Treasures and their Preservation".
Split into simpler sentences: Between 1866 and 1872 he delivered a series of free lectures which he described in "A Synopsis of Fourteen Popular Lectures". In 1871 he gave a lecture to the British Archæological Association on "Art Treasures and their Preservation".