The presence of zones of muddy, ice-free water at the sea faces of tidal glaciers has been recorded from Alaska (Gilbert, 1910), and from Spitzbergen (Stott, 1936). In view of their great significance in local ecology an understanding of the causes of these so-called "Brown Zones" seemed desirable and the problem of their establishment was first attacked hydrographically by the Oxford University Expedition to Spitzbergen, in 1933....