Daubuisson, a favourite pupil of the Freiberg professor, had written and published at Paris in 1803 a volume on the Basalts of Saxony, conceived in the true Wernerian spirit, and treating these rocks, as he had been taught to regard then, as chemical precipitates from a former universal ocean. In the following year the young and accomplished Frenchman went to Auvergne and the Vivarais that he might see with his own eyes the alleged proofs of the volcanic origin of basalt. Greatly no doubt to his own surprise, he found these proofs to be irrefragable. With praiseworthy frankness he lost no time in publicly announcing his recantation of the Wernerian doctrine on the subject, and ever afterwards he did good service in making the cause of truth and progress prevail.
Still more sensational was the conversion of a yet more illustrious prophet of the Freiberg school—the great Leopold von Buch. He too had been educated in the strictest Wernerian faith. But eventually, after a journey to Italy, he made his way to Auvergne in 1802, and there, in presence of the astonishing volcanic records of that region, the scales seem to have fallen from his eyes also. With evident reluctance he began to doubt his master's teaching in regard to basalt and volcanoes. He went into raptures over the clear presentation of volcanic phenomena to be found in Central France, traced each detail among the puys, as in the examination of a series of vast models, and remarked that while we may infer what takes place at Vesuvius, we can actually see what has transpired at the Puy de Pariou. With the enthusiasm of a convert he rushed into the discussion of the phenomena, but somehow omitted to make any mention of Desmarest, who had taught the truth so many years before.
Impressed by the example of such men as Daubuisson and Von Buch, the Wernerian disciples gradually slackened in zeal for their master's tenets. They clung to their errors longer perhaps in Scotland than anywhere else out of Germany—a singular paradox only explicable by another personal influence. Jameson, trained at Freiberg, carried thence to the University of Edinburgh the most implicit acceptance of the tenets of the Saxon school, and continued to maintain the aqueous origin of basalt for many years after the notion had been abandoned by some of his most distinguished contemporaries. But the error, though it died hard, was confessed at last even by Jameson.
After the close of this protracted and animated controversy the study of former volcanic action resumed its place among the accepted subjects of geological research. From the peculiarly favourable structure of the country, Britain has been enabled to make many important contributions to the investigation of the subject. De la Beche, Murchison and Sedgwick led the way in recognizing, even among the most ancient stratified formations of England and Wales, the records of contemporaneous volcanoes and of their subterranean intrusions. Scrope threw himself with ardour into the study of the volcanoes of Italy and of Central France. Maclaren made known the structure of some of the volcanic groups of the lowlands of Scotland. Ramsay, Selwyn, and Jukes, following these pioneers, were the first to map out a Palæozoic volcanic region in ample detail. Sorby, applying to the study of rocks the method of microscopic examination by thin slices, devised by William Nicol of Edinburgh for the study of fossil plants, opened up a new and vast field in the domain of observational geology, and furnished the geologist with a key to solve many of the problems of volcanism. Thus, alike from the stratigraphical and petrographical sides, the igneous rocks of this country have received constantly increasing attention.
The present work is intended to offer a summary of what has now been ascertained regarding the former volcanoes of the British Isles. The subject has occupied much of my time and thought all through life. Born among the crags that mark the sites of some of these volcanoes, I was led in my boyhood to interest myself in their structure and history. The fascination which they then exercised has lasted till now, impelling me to make myself acquainted with the volcanic records all over our islands, and to travel into the volcanic regions of Europe and Western America for the purpose of gaining clearer conceptions of the phenomena.
From time to time during a period of almost forty years I have communicated chiefly to the Geological Society of London and the Royal Society of Edinburgh the results of my researches. As materials accumulated, the desire arose to combine them into a general narrative of the whole progress of volcanic action from the remotest geological periods down to the time when the latest eruptions ceased. An opportunity of partially putting this design into execution occurred when, as President of the Geological Society, the duty devolved upon me of giving the Annual Addresses in 1891 and 1892. Within the limits permissible to such essays, it was not possible to present more than a full summary of the subject. Since that time I have continued my researches in the field, especially among the Tertiary volcanic areas, and have now expanded the two Addresses by the incorporation of a large amount of new matter and of portions of my published papers.
In the onward march of science a book which is abreast of our knowledge to-day begins to be left behind to-morrow. Nevertheless it may serve a useful purpose if it does no more than make a definite presentation of the condition of that knowledge at a particular time. Such a statement becomes a kind of landmark by which subsequent progress may be measured. It may also be of service in indicating the gaps that have to be filled up, and the fields where fresh research may most hopefully be undertaken.
I have to thank the Councils of the Royal Society of Edinburgh and the Geological Society for their permission to use a number of the illustrations which have accompanied my papers published in their Transactions and Journal. To Colonel Evans and Miss Thom of Canna I am indebted for the photographs which they have kindly taken for me. To those of my colleagues in the Geological Survey who have furnished me with information my best thanks are due. Their contributions are acknowledged where they have been made use of in the text.
The illustrations of these volumes are chiefly from my own note-books and sketch-books. But besides the photographs just referred to, I have availed myself of a series taken by Mr. Robert Lunn for the Geological Survey among the volcanic districts of Central Scotland.
Geological Survey Office,
28 Jermyn Street, London,
1st January 1897.