Information on Ballygrant and Kilmeny church can be found here:

http://www.islayinfo.com/ballygrant.html
http://www.geograph.org.uk/photo/1856958

"The water is wide" between Carrickfergus and Ballygrant, and the Ballygrant burial ground "in Kilmeny" has "marble stones as black as ink." Seems pretty straightforward.