After reading that there were traces of Ogham writing in New England I started keeping an eye out for scratched rocks. Ogham was a writing system used in Bronze age Europe and Britain, based on groups of vertical lines crossing a long horizontal base line. Different numbers of verticals in a group, or whether the group was above, below or across the baseline, determines which letter is represented by the group. Ogham came in many forms and appears to have been used by such people as the Celts in Western Europe and Britain, the people of Troy, and by other seagoing people whose God was "Bel" or "Baal". Examples of Ogham also have been found in Japan and in Africa, and very clear examples have been found on the east coast America and along its larger river systems. For the most part the languages written in Ogham and the variants of the alphabet are known and it is sometimes possible to read Ogham inscriptions. A search on the Web for "Ogham" turns up plenty of sites on the subject.

Sure enough, there is a Petroglyph in Concord in the form of Ogham. This example comes from the woods around Hanscom field. The grooves are uniform in depth and width, with a shallow "U" cross section, but I had to put water on them to make them visible, a somewhat suspect procedure. Normally, engraving like this can only be seen when the light comes in just right from the side.
 
 

   Here is a closer view (and you can see that the added water started to drip). Following a version of the alphabet given in The White Goddess by Robert Graves, I came up with 'C', 'H', 'B', 'N' for the first four main strokes, but could not make anything of the way the message is divided along the ridge of the rock into a separate line of strokes. In one reference book, the small cross below the left end of the horizontal is identified as a symbol for "moon".

Someday perhaps an expert in deciphering Ogham can make something out of this.  The presence of Ogham in America is highly controversial so let us leave it at this: there are petroglyphs here in Concord that could be Ogham.