Walker (1940) considered that the chemical data of the differentiated Palisade sill could not be treated in variation diagrams because of the narrow range of SiO2 weight per cent. The present work examines the same data using a recent graphical technique which is not subject to such limitations. The results show that the chemical variation is almost exactly that required by crystal fractionation of olivine and pyroxene from a single, relatively homogeneous, parent magma. Most other hypotheses of differentation are either unnecessary or not in accordance with the chemical data. Generally, the results confirm Walker's earlier conclusions which were based mainly on petrography ansd field relations.