sterling engines run off of the difference in temperature between two substances, liquid primarily. were the ancient henges used for this purpose, to irrigate water, grind grains etc? Ii have discovered that this is highly possible. some interesting facts in this regard:
Although I do not live in the UK, over the years I've had the opportunity to visit a number of Britain's hinges. They vary considerably in size, construction, materials, layout. Stonehenge is just one of many, though it gets most of the publicity. Personally I don't see them being a sterling engine. Stonehenge especially is associated with numerous burial barrows. Other henges have adjacent structures more apt to be for religious/spiritual use than anything else. There are numerous other stone "works" all around the UK. I find them fascinating.
It's never too late to start! I retired to homestead on the slopes of Mauna Loa, an active volcano. I relate snippets of my endeavor on my blog : www.kaufarmer.blogspot.com
The temperature difference between the colored stones would not generate sufficient energy to do any work, in my opinion, especially not with stone and wooden machinery. You might be able to get a paper pinwheel to spin due to the difference in temperature, but that's about it, I think.
Aside from well-established solar/lunar/seasonal correspondences in many henges, Stonehenge in particular went through many phases of construction in different materials before arriving at the configuration you describe as being similar to part of a stirling engine. I find it really hard to imagine that a certain stage of a millennia-established ceremonial center suddenly became used as a power generator, even ignoring the fact that it would not have been efficient enough to, as Tyler put it, power a paper pinwheel.
He repaced his skull with glass. So you can see his brain. Kinda like this tiny ad: