Abstract
The specimen of cordierite-gneiss under notice was collected by Mr. T. N. Muthuswami (Assistant Professor of Geology, Presidency College, Madras) in a quarry at Ganguvarpatti in the Madura district. On examining tliin sections of the rock, he found that many of the cordierite crystals were optically positive, and, thinking that the mineral might be worth further investigation, he sent a specimen of the rock to me. The investigation was carried out ill the Geological Department of the Imperial College of Science and Technology, and my thanks are due to Professor W. W. Watts and Dr. J. W. Evans for their kindness in affording me facilities for this work and also to Dr. H. H. Thomas, of H.M. Geological Survey, for his kindness in placing Fedorov's universal stage at my disposal for the measurement of the optic axial angle.
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