CELTIC HIGH CROSSES
What we generally call Celtic Crosses are memorial crosses: the Latin cross with the crescents forming a circle between the cross and upright beams. They take their form from the Irish High Crosses which are found throughout Ireland and in parts of Britain and Scotland where Irish monks founded monasteries. They were usually located around monasteries although they sometimes marked boundaries or market places.
The total height of the cross, including the base and cap (shaped like a roof) varied – 7 feet up to 24 feet. Some historians suspect that the term high cross does not refer to the height of the cross but to its status. In Irish the word Árd is usually translated as high but also means principal or main. The origins of the characteristic ring have several theories. The simplest is as a support for the cross beam. That seems just too simple an explanation since a straight piece with 45 degree angle from the upright at each side would be much easier to carve although less pleasing to the eye.
There are other explanations here are a few:
The ring is made to form a halo representing Jesus to a symbol of eternity to a leftover reference to the carried over from the art representing the Irish Sun God from ancient times. Other characteristics were the scalloping on the shaft and cross beam where the crescents join. Many crosses were also decorated with scenes from the old and new testaments. Small decorative cylinders called volutes are also found attached to either the crescent or the shaft. There were two main periods when the crosses were erected through the 9th and 10th centuries, and again in the 12th century. The 9th and 10th century crosses are known as scriptural crosses because of their biblical scenes. The East facing side had the Old Testament and the West side the New Testament. The later crosses had fewer biblical scenes but more of high relief figures of Jesus and a local Saint or Bishop. These carvings are similar to those found in Roman and other Western European churches and monasteries. It is believed that monasteries turned to erecting the crosses since they would be less prone to destruction. Many precious objects and manuscripts had been looted and destroyed during the Viking raids.
Many of the crosses have been carved from sandstone which I believe may be a relatively easy material to work with. But others have been carved from limestone and granite.