Complex sentence: Dr. Mead my have acquired the manuscript in the 1690's when he traveled to Italy, however, the manuscript did not appear in the catalog of the sale of Dr. Mead's library in 1754-55.
Split into simpler sentences: Dr. Mead my have acquired the manuscript in the 1690's when he traveled in Italy. However, the manuscript did not appear in the catalog of the sale Dr. Mead's library, 1754-55.