It is curious to note the strong tendency of single devices or badges to merge into threes. It occurs first in the case of the single crown, which presently gets tripled, then the single harp does the same, and the three castles, the arms of Dublin, very likely began as one. James I. made one more important change; he substituted one of the Scottish unicorn supporters for the red dragon of Cadwallader, used as a dexter supporter by Henry VIII., Edward VI., Mary, and Elizabeth. The ancient Scottish supporters were two unicorns arg., armed, maned, and unguled, gorged with a princely coronet and chained or. The origin of the unicorn supporters is lost, but the creature is generally considered to be an emblem of purity and of freedom; the horn, moreover, was credited with medical powers as a remedy against poisons. The idea of an animal bearing a single horn arose probably from the horn of the narwhal, which has diagonal striations upon it resembling those generally shown on the horn of a unicorn, and certainly does not look like the tooth of a fish. On the other hand cups made of rhinoceros horn are credited with the same magical powers as that of the unicorn. The chain attached to a princely coronet on the neck of the unicorn is not easy to explain; it is said that it alludes to an early king of Scotland, who, as a young man, accidentally killed his father, and bore the chain ever afterwards on his supporters as a sign of grief. The lion and the unicorn have remained ever since the time of James I. as the supporters of the English Royal coat-of-arms, without any change whatever. In Scotland James VI. had John Gibson for his bookbinder. He was appointed under the Privy Seal, and was "Our Soverane Lordis Buikbinder," but there is no binding left that can with certainty be attributed to him. On James's advent to England John and Roger Norton and Robert and Christopher Barker were made Royal binders and printers, and in 1604 John and Abraham Bateman were made "Bookbinders to the King." The many fine armorial bindings which were used by James I. were probably made by one or other of these binders, but for the present no signed binding has been found, so the authorship of any one of them is only conjectural.