During these formidable wars with Antigonus, Ptolemy had never been troubled with any serious rising of the conquered Egyptians; and perhaps the wars may not have been without their use in strengthening his throne. The first danger to a successful conqueror is from the avarice and disappointment of his followers, who usually claim the kingdom as their booty, and who think themselves wronged and their past services forgotten if any limit is placed to their tyranny over the conquered. But these foreign wars may have taught the Alexandrians that Ptolemy was not strong enough to ill-treat the Egyptians, and may thus have saved him from the indiscretion of his friends and from their reproaches for ingratitude. In the late war, the little Dorian island of Cos on the coast of Asia Minor fell, as we have seen, under the power of Ptolemy. This island was remarkable as being the first spot in Europe into which the manufacture of silk was introduced, which it probably gained when under the power of Persia before the overthrow of Darius. The luxury of the Egyptian ladies, who affected to be overheated by any clothing that could conceal their limbs, had long ago introduced a tight, thin dress which neither our climate nor notions of modesty would allow, and for this dress, silk, when it could be obtained, was much valued; and Pamphila of Cos had the glory of having woven webs so transparent that the Egyptian women were enabled to display their fair forms yet more openly by means of this clothing. [Illustration: 081.jpg ALEXANDRIAN LADY, ATTIRED IN BOMBYX SILK] Cos continued always in the power of the Ptolemies, who used it as a royal fortress, occasionally sending their treasures and their children there as to a place of safety from Alexandrian rebellion; and there the silk manufacture flourished in secret for two or three centuries. When it ceased is unknown, as it was part of the merchants' craft to endeavour to keep each branch of trade to themselves, by concealing the channel through which they obtained their supply of goods, and many of the dresses which were sold in Rome under the emperors by the name of Coan robes may have been brought from the East through Alexandria.