Shortly after this letter, Lyell, though all the manuscript of his second volume had not yet been sent to the printers, and proof-sheets followed him, refreshed himself with a tour of four or five weeks in the volcanic district of the Eifel. Here the cones, all comparatively low, are scattered sporadically over a rolling upland which occupies the angle between the Rhine and the Moselle. The valleys for the most part are carved out of slaty rocks much of the same age as those of Devonshire; and the craters, "strange holes, each eruption having been almost invariably at some new point," are now very commonly occupied by quiet pools of water, such as Lyell had already seen in the old volcanic districts of the Papal States. Among these craters, composed sometimes of loose and light scoria, from which no lava-stream ever flowed, he found fresh evidence--as at the Rotherberg--against the diluvian hypothesis. "It is," as he writes to his friend, Dr. Fleming, "one of the ten thousand proofs of the incubus that the Mosaic deluge has been, and is, I fear, long destined to be, on our science. Now, I am fully determined to open my strongest fire against the new diluvial theory of swamping our continents by waves raised by paroxysmal earthquakes. I can prove by reference to cones (hundreds of uninjured cones) of loose volcanic scoriæ and ashes, of various and some of great antiquity (as proved by associated organic remains), that no such general waves have swept over Europe during the Tertiary era--cones at almost every height, from near the sea, to thousands of feet above it."[48] But early in August he was back in London, hard at work in writing and correcting proofs. This business detained him longer than he anticipated, but his labours were cheered by the news of the eruption of Graham's Island. Here was another case in support of the thesis which he was ready to maintain against all comers. But a few months since there had been a depth of eighty fathoms, as was proved by sounding, on the site of this island. Now the cone "is 200 feet above water and is still growing.[49] Here is a hill 680 feet, with hope of more, and the probability of much having been done before the 'Britannia' sounded." Surely Nature herself was testifying "her approbation of the advocates of modern causes! Was the cross which Constantine saw in the heavens a more clear indication of the approaching conversion of a wavering world?" But in the beginning of September Lyell broke away from the emissaries of the press and took passage by sea to Edinburgh, there to combine business with a fair amount of both scientific work and social pleasure. This visit afforded him an opportunity of hearing Chalmers preach. In a letter to Miss Horner he gives a brief abstract, and expresses his general opinion of the sermon[50]:--