Contents

11 September 1998
Vol 281, Issue 5383

About The Cover

Cover image expansion

COVER Ombrotrophic peat bogs receive material exclusively from the atmosphere in the form of rain and soil dust, but pollutants also. As the peat accumulates over thousands of years, it preserves many changes in the chemical composition of the atmosphere. From a 650-centimeter-long core from a peat bog in the Jura Mountains, a record of atmospheric lead deposition was constructed extending back 12,370 radiocarbon years before the present. See page 1635.[Photo: Chaltenbrunnen mire, Swiss Alps, by S. Eigstler]