It is also in its various forms an emblem of martyrdom that of St. Peter’s being in a reversed position in reference to the manner of his execution. _The Pastoral Staff_ The cross, invariably with foliated ends, mounted on a staff, is the Crozier of an Archbishop. The staff of a Bishop terminates with a curving head in the form of a shepherd’s crook which it symbolises; both being indicative of authority. _Symbols of Martyrdom_ Martyrdom is symbolised not only by the palm, and the crown, as indicative of Victory over death and reward, but by the banner of Triumph over death and persecution. Also by the sword, as a symbol of violent death, or by other implements of execution. These are represented in conjunction with the individual martyr or saint, as attributes and as a means of identification. As symbols personal to Christ, the emblems of the Passion and Crucifixion are proper to the Cross and chalice. Such, for instance, as the crown of thorns, the nails, scourge, whipping-post, ladder, spear, lantern, thirty pieces of silver, etc. _Symbolism of Gems, etc._ In Christian art, gems, metals and colours are invested with symbolic meaning. The amethyst signifies humility, the Diamond--Invulnerable Faith, the Sardonyx--Power, the Sapphire--Hope, Gold represents Power or Glory, and Silver--Purity. Black represents Grief or Death, Blue--Hope and Divine Contemplation, pale blue--Peace, Christian Prudence or a serene conscience, Green--Faith, Gladness, pale green--Baptism, Grey--Tribulation, Purple--Justice or Royalty, Red--Martyrdom for Faith, Scarlet--Fervour, and glory of witnesses to the Church, Violet--Penitence, and White--Purity, Temperance and Innocence. Shells on tombstones are allusive to the earthly body left behind, a mere shell of the immortal soul. They are also used to indicate a pilgrim, by whom they were carried, probably as a drinking vessel or form of spoon. Torches, either upright or inverted, symbolised respectively Life and Death. When in the latter position the flame is represented as ascending, the significance is Death with hope of the Resurrection. An earlier signification in Pagan art is the bridal torch of Hymen. _Masks_ Masks, which frequently appear in Renaissance ornament, are traceable to the Greek employment to symbolise Comedy and Tragedy. The Medusa head, which occurs on shields and on the Ægis of Athenē, was the emblem of Terror. The tradition being that Medusa, one of the three Gorgons, famous for her hair, set her beauty against that of Athenē. As a punishment, her hair was converted into serpents, the aspect of which was so terrible that any who looked thereon were changed to stone. A fate to which the Gorgon herself succumbed on seeing her reflection in the burnished shield of Perseus.