McClaran-delta-intro

"For centuries the Phoenicians alone possessed the secret of the manufacture of purple. ... The Roman emperors transferred the manufacture of purple to Italy and conducted it as a monopoly. The art of purple dying, which, like many of the arts, had reached a high level at this time, was lost almost completely in the stormy period which marked the migration of nations. For a short time the art was still preserved in the Byzantine Empire, only to become extinct there in the 12th Century."

Josef Maria Eder, Edward Epstean, and Hinricus Lüppo-Cramer, HISTORY OF PHOTOGRAPHY. (New York: Columbia University Press, 1945).