Kilmartin Glen, Argyll, June 2013
are these stones marked with Ogham ?
What is Ogham?
its an old alphabet, dates back to pictish and celtic days, that uses groups of lines marked to either side of a central line as the letters. It could be used on sticks of wood to transport messages (dark ages Welsh princes had their own coded versions), detailed in a medieval document along with musical versions. Most of the remaining examples are seen as lines scribed to either side of the corner of standing stones. It was recorded as used in Wales into Victorian times. Wikipedia has a good page on it and there's a lot more on the internet (including fonts !)
there are examples on DA, just search "Ogham"
I've visited these stones many times and they are very worn, never seen anything. Neolithic, perhaps too old to still see anything engraved. Perhaps its the exposed location?