Address delivered at the anniversary meeting of the Geological Society of London, on the 21st of February, 1873 : prefaced by the announcement of the award of the Wollastom Medal, the proceeds of the Donation Fund, the Murchison Medal and Geological Fund for the same year / by the Duke of Argyll, K. T., D. C. L., F.R.S., President of the Society / London : Printed by Taylor and Francis , 1873