The gravestones at Clonmacnois may be compared with stones found elsewhere. I first compared the Clonmacnois data with data from Monasterboice - a roughly contemporaneous site elsewhere in Ireland. Like Clonmacnois, Monasterboice was an early Christian church, and it was also a center of development for the Celtic cross in Ireland. Monasterboice is considerably smaller in size, though.
I observed only one major difference between the two sites, and this difference occurred only with the most modern of the gravestones. The difference is not artistic; rather, it concerns the inscriptions. The modern inscriptions on the Clonmacnois and Monasterboice gravestones both contain the same basic elements but in different orders.
These formats are general trends, and they are not found on all of the gravestones. Nonetheless, the patterns are evident. The only point of divergence between the two inscription formats is the placement of the "erected by" element. This element comes first in Monasterboice and last in Clonmacnois. Also, it is more common in Monasterboice (occurring in a greater percentage of the modern gravestones).
I decided to compare the Clonmacnois gravestones with the gravestones of Irish immigrants at the Holy Cross Cemetery in Colma, California. I wanted to obtain an impression of what changes occurred when these particular people were not in direct contact with high crosses and other gravestones in Ireland.
Among the immigrant gravestones in question, I found one example of a standing ringed cross. It lacked the "roof" present on almost all of the Irish crosses. Also, it had only one "boss" in the center of the cross, whereas the Irish crosses had additional "bosses" at the four points of juncture between cross and ring. This California example showed an awareness of the traditional Celtic high cross, but the replication was not exact.
Other Irish immigrant gravestones showed considerable variation. The "IHS" insignia was common, but the "radial" display and the "ringed cross carved motif" were absent.
As expected, the Californian and Irish gravestones showed remarkable differences, despite the shared ancestry of the people associated with them. The changes occuring in Irish gravestones did not occur in California. For example, a radial display and the engraved form of a ringed cross were associated with the "IHS" insignia in Ireland, but this development never occurred in the Irish immigrant gravestones in California. The modern Irish stones also developed a "slab" facing to replace the "shaft" and "base" of the older high crosses, creating a surface better-suited for inscription. This development is not found in the Californian stones. Finally, the adherence to the traditional high cross form is very weak in the Californian gravestones. These occurrences may seem blatantly obvious; however, this information is helpful for archaeologists who desire to understand the explicit details of cultural trait transmission and variation.