"Pillar Island", an uninhabited islet of basaltic formation off the W. coast of Scotland, 54 m. W. of Oban; 1½ m. in circumference, and girt with precipitous cliffs, except on the sheltered NE., where there is a shelving shore; is remarkable for its caves, of which Fingal's Cave is the most famous, having an entrance 42 ft. wide and 66 ft. high, and penetrating 227 ft.