When studying the geology of the Giants Causeway district in 1924 I noticed a strange system of well-developed joints on the surface of some basalt columns. As these only appeared on the planes of a few columns in this district, where several hundred thousand basalt columns are exposed, and as these joints were only to be found on and quite close to the surface, I firstly regarded them as a mere feature of weathering. It was only after Professor Dr. Maximilian Weber in Munich pointed out to me the striking resemblance of these joints to the photos published in Daubrée's Études synthétiques de Géologie Experimentale, and I decided to investigate this problem closer, the results of which are given as follows:–

This system of joints is only to be found at one locality in the Giants Causeway district, i.e. the lower parts (sea level) of the “Grand Causeway” (west side) opposite the “wishing chair” (the spot is marked with a white X on Fig. 1, Pl. XIV).