Sorry Pat.
A pebble search, is when you take a starting point eg parish where they were at a particular time, in my case the 1851 census and draw a circle around it representing say a mile, search all churches (or other sources)in that area, if you dont have any luck, move your search about to say 2 miles around the area and so on. That way you are searching evenly, quite often the ancestors would only move into a neighbouring parish. Its still a bit hit and miss though.
I dont think I have explained very clearly, but hope you get the idea, I found it has worked for me a few times.
Daisy