|I was very excited when I found this paragraph.
It hints that the motte may be a passage tomb as I had suspected.
Journal of the Waterford and South East of Ireland Archaeological Society Volume III 1897
Available to download at http://www.waterfordcountylibrary.ie/en/localstudies/ejournals/jwseias/jwseiasvol3/
Pg 92 - Earliest Monuments in Cashel and Emly
by Rev R H Long, Rector, Templemore
"What a pity it is that a society is not formed now, e'er it is too late, to make a thorough photographic examination of those that remain, and deposit in our museum whatever articles may be found in them of historic value.
The fairies of our times are growing too merciful to mankind to be trusted any longer with those relics, and when they allow Paddy to get hold of them he does not care anything about them unless they are either gold or silver. However, it is probable that but few of these earth-works are sepulchral; those with a central mound are, I suppose, the only ones that may be.
The remains at New Grange, near Drogheda, are considered to be tombs, and the similar mounds in the diocese of Cashel and Emly may be also. The most notable of these are two in Rathcool parish-one at Ardmayle, and one at Knockgraffon. There is no doubt that these mounds are hollow, and there is but little doubt that some day they will be destroyed. One of them had in recent years a narrow escape from a passing railway. I have been informed on good authority that some fifty years age certain workmen, while tilling the field about this latter, came on a subter-ranean passage in which they found what they described as two old swords and an old bucket, which, of course, they treated as rubbish."
Posted by bawn79
5th January 2009ce
Edited 5th January 2009ce