In her 1991 Master's Thesis, The Role of the High Cross in Early Christian Ireland: 8th to 11th Centuries, Jill Quattlebaum discusses the early Christian Church in Ireland and the importance of the stone cross as its symbol. The thesis is available to read online.
The archaeology of Ireland reaches as far back as eight thousand years ago and has revealed a history as intricate and compelling as the beautiful artwork produced by her people. And while archaeology has illuminated Ireland’s cultural past as far back as its earliest settlers, this thesis is concerned with a later period during which Ireland became an economic power of note, and more importantly, a cultural beacon in the darkness which covered Western Europe. The period to which I am referring is the fifth through the twelfth centuries also known as the Early Christian Period.