But what about Cana Independent Chapel in Felindre Farchog, dating from a little earlier, namely 1856-7? It would not have made much sense for stones to have been hauled from Carn Meini to a place on the northern side of the mountain -- and it's much more likely that the source would have been either Carn Goedog, Carn Breseb or one of the other spotted dolerite outcrops between Carn Goedog and Carn Alw. Maybe several sources....... Access to all these sites would have been very easy, especially if horse-drawn sledges were used.
After all, the route running past the southern tip of Carn Goedog was a familiar one, which was used by hundreds of local farmers and drovers, and many thousands of animals, en route over the Preseli ridge and running towards Carn Alw and thence to Eglwyswrw.
Thinking of the drovers, I wouldn't be at all surprised to find that the grassy "col" between Carn Goedog and the mountain slope was used occasionally as a camp site by the drovers in the rip-roaring days before the railways killed off the droving trade at a stroke. The col is one of the few places on the open mountain where there is some shelter.
Worth some research -- perhaps we can convince the geologists to take a spotted dolerite sample from the chapel and see where it fits in the great scheme of things? I'm sure the Good Lord would not mind a discreet drill-hole somewhere on the front facade, all in the cause of science........