SummaryWilliam Barlow was an important if unconventional scientist, known for having developed the ‘closest-packing’ atomic models of crystal structure. He resumed an early nineteenth-century tradition of utilizing crystallographical and chemical data to determine atomic arrangements in crystals. This essay recounts Barlow's career and scientific activity in three parts: His place in the tradition of determining atomic arrangement in context of this earlier tradition and of contemporaneous developments of crystallography and chemistry, his unconventional career, and the ‘success’ of his program to (...) determine atomic arrangements in crystals and its influence on the work of William Lawrence Bragg. (shrink)