This one appears to say CAEW, which is Sindarin for Resting Place
All 4 runes are part of Tolkien's Cirth. These runes belong to the alphabet known as Angerthas Daeron and are the runes used to represent Sindarin. The runes in the picture translate as "kaew":
The runic 'k' is actually meant to represent a Sindarin 'c', however the elvish 'c' is almost always pronounced as a 'k'. With this in mind, the letters "kaew" would actually appear in Sindarin as "caew". So, what does this mean?
Well, "caew" can be used to refer to a resting-place, which seems particularly apt given that the stone circle is where you go to rest after retreating from battle.
Although it is likely just a coincidence, I have also noticed that if you take the phonetic representation of this word ("kaew") and read it backwards, you get "weak", which is exactly what you are after retreating.
Source: Reddhawk's forum post