it was shaped like the helms of the guards of the citadel , save that it was loftier , and it was all white , and the wings at either side were wrought of pearl and silver in the likeness of the wings of a sea-bird , for it was the emblem of kings who came over the sea ; and seven gems of adamant were set in the circlet , and upon its summit was set a single jewel the light of which went up like a flame .