Whitehurst, John (1713-1788). An inquiry into the original state and formation of the earth. -- The 2d ed. London: Printed for W. Bent, 1786.
In 1786 Whitehurst published a second edition of his Inquiry, and he added a significant new chapter on the Giants Causeway. He had visited northern Ireland on a commission to find coal, and when he examined the area, he found evidence that the entire region of the north Irish coast had once been flooded by lava. There is not the least doubt, he asserted, that this was a volcanic production.
Concerning the Causeway, which he describes in some detail and illustrates with a new plate, he proposed that what is now the Causeway was once in the heart of a mountain, and in a state of fusion. The rock must have cooled very slowly, and as it contracted it acquired its columnar form. He thought the original temperature must have been immense, and the cooling process must have been very gradual.