Surmounted by a circle in the form known as the Crux Ansata, it was sacred to Isis, and stood as an emblem of immortality and life generally.
There are various forms of the cross in Christian art, the Greek cross with four equal arms, signifies the blessing which the great Sacrifice extends equally over the four quarters of the world.
The Latin cross, in which the shaft is longer than the upper arm, sometimes has three steps which signify the triple foundations of Faith, Hope and Charity; the last being the lowest as the foundation of all Christian virtues.
The Latin cross is sometimes furnished with two transverse arms, when it is known as the Ecclesiastical cross, used by Cardinals and Bishops at Rome. The cross of the Pope has three transverse arms.
The Cross of St. Andrew, or cross saltire, is in the shape of the letter X, and is used as a symbol of martyrdom.
The Tau Cross in the shape of the letter T—frequently used in Byzantine representations of the Crucifixion, is that on which the Brazen Serpent was uplifted; and was also the sign marked on the door-posts at the sacrifice of the Paschal Lamb of the Exodus.
The Cross with the arms bearing leaves or blossom, is symbolical of the triumph of Christianity over sin and persecution. Occasionally it takes the form of a spreading tree. When five red marks or jewels are placed in the centre and extremities they are emblematic of the five wounds.
In Christian art the cross is the symbol of Christ, either in the simple form, or as a crucifix, which in the early renderings was more suggestive of voluntary sacrifice. The realistic treatment of physical suffering belongs to a later period.
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.