"Chemical analysis of dust which fell on the S.S. Dunstan when about 400 miles southwest of the Canary islands on February 6, 1962, shows essential differences (in SiO 2 , Al 2 O 3 , MgO content and in the Fe:Ti ratio) between the dust and the nearest analysed deep-sea sediment, and indicates a means of recognizing aeolian material in such sediments. The presence of clear, uncoated quartz grains in the Dunstan dust shows that quantitative estimates of wind borne dusts in ocean sediments cannot reliably be obtained from counts of coated quartz grains in these sediments. . . . The origin of the dust is believed to be the coast of Spanish Sahara, where long shallow depressions may act as suitable gathering grounds for both the minerals and the organic matter."