Seven glaciers from 9 to 26 kilometers in width move 0.3 to 2.3 meters per day. Byrd Glacier is the fastest moving of the known valley glaciers in Antarctica.

Iceberg Size (km) Latitude/longitudeSince the publication of the second edition of our Illustrated glossary of snow and ice (Cambridge, Scott Polar Research Institute, 1973) a number of suggestions have been made for additions and alterations. We invite comments on the following new terms and definitions, either informally or to be published as letters to the Editor. These terms are considered necessary for convenient description of features which occur in the polar regions. ICEBERGA large mass of floating or stranded ice of greatly varying shape, usually more than 5 m above sea level, which has broken away from a glacier. (The word 'usually' has been added to the existing definition in order to include tabular bergs originating from low ice shelves.) * Scott Polar Research Institute, Cambridge CB2 1ER. t British Antarctic Survey, Cambridge CB3 0ET.

Dear editor and reviewers, Thank you for your time, and extensive and very constructive comments. We are currently revising the manusript according to all your comments. We also expect advices from the editor regarding the revision. We will submit the revised manuscript and point-to-point responses to comments once completed. Best. C1

A set of Landsat-5 multispectral scanner (MSS) images of Filchner-Ronne Ice Shelf was commissioned by the Institut für Angewandte Geodäsie and recorded over a short period in early 1986. A mosaic of digitally enhanced images was constructed, using all available ground control. In due course it is planned to use the data for the production of a series of digital-image maps at a scale of 1:1 000 000. Meanwhile a line map has been prepared at a scale of 1 :2 000 000 to show the principal glaciological features. The new mosaic shows much more detail than earlier Landsat images and extends coverage to higher latitudes. More of the poorly known southern boundary of the ice shelf can be identified but floating ice still extends beyond the limit of coverage. Extensive ice rumples are revealed, many of them undetected in earlier imagery. Flow bands can be tracked without a break from their ice-stream source to the ice front, over distances of up to 800 km. Even minor tributaries, and sheet flow from the inland ice sheet between the ice streams, yield narrow but identifiable flow bands. Ice thickness, velocity, and mass-flux data are reviewed, in order to underline their dependence on good mapping.

The characteristics and probable development of dirt cones on Vatnajökull (Iceland) are described. Thick accumulations of debris protect the ice beneath them from ablation, whereas thin ones accelerate the process. Under given conditions of ablation, the nature of the debris covering is the deciding factor—in particular its radiation absorption coefficient, conductivity and thickness. Contrasts are noted between the dirt cones of Vatnajökull and those of other glaciers. The nature of the debris and of the ablation varies greatly from place to place, but all dirt cones result from differential ablation.